**6. Biodegradable polyurethanes based on ε-Caprolactone**

Polyols with different molecular weights have been synthesized through ring opening polymerization of caprolactone by BHETA. Polyurethanes with different soft segment chainlengths have been synthesized using above-mentioned polyols.

#### **6.1 Ring opening polymerization: Using of BHETA**

Ring opening polymerization of caprolactone by BHETA is a unique method which is used to synthesis of biodegradable polyurethanes. BHETA synthesized locally was reacted with ε-caprolactone through ring opening polymerization at 130°C using 1 wt% DBTDL as the catalyst for 3.5 h in a round-bottom flask equipped with a condenser, stirrer, thermometer and nitrogen gas-inlet tube. The reaction and HNMR spectrum of the synthesized polyol is shown in Fig. 17. Polyols with different molecular weights through ring opening polymerization of caprolactone by BHETA have been synthesized. (Mir M. Sadeghi et al, 2011).

The various molar ratios of ε-Caprolactone to BHETA used in the synthesis of polyols, named Polyol-8 to Polyol-142, are shown in Table 1. Then urethane linkages were formed using Di-isocyante without chain extender. For synthesis of polyurethanes (PU-8 to PU-142) at first, polyols were extended with HDI. Calculated amount of HDI/DMF solution was added drop-wise at 110°C. The homogeneous mixture was then poured slowly into a Teflon mold and maintained at 60ºC for 12 h. The films were then removed and placed in a desiccator for testing.

Three types of polyurethanes have been synthesized based on BHETA. In the first case, BHETA is used as ring opening agent in caprolactone polymerization, and then novel biodegradable polyurethane has been synthesized. In the second and third cases, BHTEA is used as chain extender to synthesis of special and high modulus polyurethanes as follows:

Polyols with different molecular weights have been synthesized through ring opening polymerization of caprolactone by BHETA. Polyurethanes with different soft segment chain-

Ring opening polymerization of caprolactone by BHETA is a unique method which is used to synthesis of biodegradable polyurethanes. BHETA synthesized locally was reacted with ε-caprolactone through ring opening polymerization at 130°C using 1 wt% DBTDL as the catalyst for 3.5 h in a round-bottom flask equipped with a condenser, stirrer, thermometer and nitrogen gas-inlet tube. The reaction and HNMR spectrum of the synthesized polyol is shown in Fig. 17. Polyols with different molecular weights through ring opening polymerization of caprolactone by BHETA have been synthesized. (Mir M. Sadeghi et al,

The various molar ratios of ε-Caprolactone to BHETA used in the synthesis of polyols, named Polyol-8 to Polyol-142, are shown in Table 1. Then urethane linkages were formed using Di-isocyante without chain extender. For synthesis of polyurethanes (PU-8 to PU-142) at first, polyols were extended with HDI. Calculated amount of HDI/DMF solution was added drop-wise at 110°C. The homogeneous mixture was then poured slowly into a Teflon mold and maintained at 60ºC for 12 h. The films were then removed and placed in a

Fig. 16. FTIR spectrum of BHETA.

2011).

desiccator for testing.

**5.2 Synthesis of polyurethanes based on BHETA** 

**6. Biodegradable polyurethanes based on ε-Caprolactone** 

lengths have been synthesized using above-mentioned polyols.

**6.1 Ring opening polymerization: Using of BHETA** 

Fig. 17. Ring opening polymerization of caprolactone by BHETA to obtain polyol.


Table 1. Molar ratios, theoretical and experimental "Mn" and "n" of used polyols.

From PET Waste to Novel Polyurethanes 373

DSC thermograms and the related data such as Tg, Tm, ΔHf and degree of crystallinity (αC) are shown in Fig. 20 and Table 2. The melting curves in Fig. 21 clearly show an endotherm for the melting, indicating the presence of one distinct crystalline zone in all polymers, which could be ascribed to ordering or size in the crystallites. As shown obviously in Table 2, increasing of molecular weight of synthesized polycaprolactone leads to a regular increase in the observed melting point from 36ºC to 63 ºC and also in heat of fusion of samples.

As shown in Table 2, the crystallinity, **α**c , of polycaprolactone (PCL) phase increases with increasing molar ratio of polycaprolactone to BHETA. **α**c is calculated using a value of ∆*H*<sup>f</sup> for completely crystalline PCL, equal to 142 J g-¹. *T*m of PU containing PCL with lower molecular weight (Mn= 2632) shows lower *T*m than *T*m of PU with higher Mn. The results indicate that the crystals obtained in PU-142 during crystallization are larger than those developed in PUs with lower content of soft segments (Table 2). The presence of hydrogen bonding between the hard and soft segments restricts the phase separation and ordering (crystallization) of PUs. When the soft segment length increases from 2632 to 16472, the reduction in the degree of connectivity between the hard and soft segments should make the phase separation process and crystallization easier. These peaks could be related to HDI/BD hard segments which have a regular repeat structure capable of high degree of hydrogen bonding, exhibit very sharp endothermic peaks at higher temperatures about 290ºC. DSC thermograms for all samples indicate that an increase in molar ratio of *ε*-caprolactone to BHETA changes the size and peak position temperature of the endotherms above 280ºC.

Longer soft segments produce better phase-separated systems which caused to form more readily sharp peaks as indicated by the trend in phase separation with increasing soft segment length at 290ºC. However, these endothermic peaks may be thought to arise from the disruption of ordered, non-crystalline hard-segment aggregates. As shown in Fig. 19, as the lengths of soft segments increases, Tg of polyurethane decreases due to more flexibility

**6.2.2 DSC results** 

Fig. 19. DSC thermograms of PU-22 to PU-142.

#### **6.2 Polyurethane characterization**

#### **6.2.1 FTIR spectroscopy**

FTIR spectra of polyurethanes with different polyol chain lengths are shown in Fig. 18. There are distinctive absorbance bands at *ca* 3435 Cm-1(nonbonded –NH groups), *ca* 3330 Cm-1(bonded –NH groups), *ca* 2940 and *ca* 2865 Cm-1 (asymmetric and symmetric CH2 groups), *ca* 1730 Cm-1(overlapped carbonyl groups of polycaprolactone and urethane linkages), *ca* 1620 Cm-1 (C=C stretching vibration in aromatic ring), *ca* 1540 Cm-1 (-CO-N amide II), *ca*(1468,1418,1390,1368) Cm-1: various modes of CH2 vibrations, *ca* (1240,1169,1040) Cm-1: stretching vibration of the ester groups and stretching of the ether group (~1100 Cm-1).

Mechanical properties of polyurethanes and Mn of used polyol are shown in Table 2.

Fig. 18. FTIR spectra of PU-22 to PU-142.


Table 2. Thermal and mechanical properties of polyurethanes and Mn of used polyol.

#### **6.2.2 DSC results**

372 Material Recycling – Trends and Perspectives

FTIR spectra of polyurethanes with different polyol chain lengths are shown in Fig. 18. There are distinctive absorbance bands at *ca* 3435 Cm-1(nonbonded –NH groups), *ca* 3330 Cm-1(bonded –NH groups), *ca* 2940 and *ca* 2865 Cm-1 (asymmetric and symmetric CH2 groups), *ca* 1730 Cm-1(overlapped carbonyl groups of polycaprolactone and urethane linkages), *ca* 1620 Cm-1 (C=C stretching vibration in aromatic ring), *ca* 1540 Cm-1 (-CO-N amide II), *ca*(1468,1418,1390,1368) Cm-1: various modes of CH2 vibrations, *ca* (1240,1169,1040) Cm-1: stretching vibration of the ester groups and stretching of the ether group (~1100 Cm-1).

Mechanical properties of polyurethanes and Mn of used polyol are shown in Table 2.

Table 2. Thermal and mechanical properties of polyurethanes and Mn of used polyol.

**6.2 Polyurethane characterization** 

Fig. 18. FTIR spectra of PU-22 to PU-142.

**6.2.1 FTIR spectroscopy** 

DSC thermograms and the related data such as Tg, Tm, ΔHf and degree of crystallinity (αC) are shown in Fig. 20 and Table 2. The melting curves in Fig. 21 clearly show an endotherm for the melting, indicating the presence of one distinct crystalline zone in all polymers, which could be ascribed to ordering or size in the crystallites. As shown obviously in Table 2, increasing of molecular weight of synthesized polycaprolactone leads to a regular increase in the observed melting point from 36ºC to 63 ºC and also in heat of fusion of samples.

As shown in Table 2, the crystallinity, **α**c , of polycaprolactone (PCL) phase increases with increasing molar ratio of polycaprolactone to BHETA. **α**c is calculated using a value of ∆*H*<sup>f</sup> for completely crystalline PCL, equal to 142 J g-¹. *T*m of PU containing PCL with lower molecular weight (Mn= 2632) shows lower *T*m than *T*m of PU with higher Mn. The results indicate that the crystals obtained in PU-142 during crystallization are larger than those developed in PUs with lower content of soft segments (Table 2). The presence of hydrogen bonding between the hard and soft segments restricts the phase separation and ordering (crystallization) of PUs. When the soft segment length increases from 2632 to 16472, the reduction in the degree of connectivity between the hard and soft segments should make the phase separation process and crystallization easier. These peaks could be related to HDI/BD hard segments which have a regular repeat structure capable of high degree of hydrogen bonding, exhibit very sharp endothermic peaks at higher temperatures about 290ºC. DSC thermograms for all samples indicate that an increase in molar ratio of *ε*-caprolactone to BHETA changes the size and peak position temperature of the endotherms above 280ºC.

Fig. 19. DSC thermograms of PU-22 to PU-142.

Longer soft segments produce better phase-separated systems which caused to form more readily sharp peaks as indicated by the trend in phase separation with increasing soft segment length at 290ºC. However, these endothermic peaks may be thought to arise from the disruption of ordered, non-crystalline hard-segment aggregates. As shown in Fig. 19, as the lengths of soft segments increases, Tg of polyurethane decreases due to more flexibility

From PET Waste to Novel Polyurethanes 375

**6.2.4 Optical Microscopy (OM) and Scanning Electron Microscopy (SEM)** 

Fig. 22. Optical microscopy images: (a) PU-22; (b) PU-38; (c) PU-76; (d) PU-142;

(e) Disordered PU-76; (f) disordered PU-142.

Optical microscopy (OM) images shown in Fig. 22 illustrate the morphology of the synthesized PUs (scale bar shows 30 microns). OM results show rather smooth and rather rough structures for samples PU-22 and PU-38, while are fibrous-looking for PU-76 and PU-

Fig. 21. DMTA thermogram of PU-38.

142.

of soft segments chains. Caprolactone-based polyurethane shows Tg at -54ºC by DSC method for polycaprolactone with Mn about 2000 g/mol. Presence of BHETA in the chemical structure results in increasing of Tg in our work.

#### **6.2.3 DMTA results**

DMTA Results are shown in Figs. 20 and 21 for PU-22 and PU-38 respectively. Two main transitions are present in the DMTA spectra: a first peak (Tβ) located in the low-temperature region (at about -75°C and - 85°C) and a second peak (*T*α) seen in a higher temperature region (at about -25°C). Increasing in soft segments length caused to decrease Tβ of polyurethanes. The observed Tβ at –75ºC and –85ºC which was assigned to methylene sequence local relaxations, in analogy to results reported previously, is due to relaxation of caprolactone-based soft segments. It is found clearly that Tβ decreases with increasing of - CH2- units in caprolactone chains in sample PU-38 rather than PU-22.

For the assignment of *T*α, we have considered a mixing-transition temperature (*T*mix), which would be the result of the various degrees of mixing between the ester and urethane blocks.

According to this interpretation, the matrix would be formed by a PCL-rich continuous phase, in which PCL crystallites would be embedded, and amorphous PCL segments emerging from entangled domains with urethane segments would be connected to these crystallites. Some damping or fluctuations at higher temperatures is seen which corresponds to the hard-segments glass transition. As Shown in Figs. 20 & 21 E' in glassy region decreases with increasing of crystalline PCL soft segments length, whereas increases in rubbery plateau. The polymer with a higher content of PCL crystalline soft segments gives a higher E' in rubbery region for PU-38 in comparison with PU-22. TGA results shows that T90% and char residue decreases with increasing of molecular weight of soft segments for samples PU-22 to PU-142, which confirms decreasing in concentration of urethanes and aromatic groups in the samples. Also, presence of aromatic ring due to BHETA led to increasing of thermal satiability.

Fig. 20. DMTA thermogram of PU-22.

of soft segments chains. Caprolactone-based polyurethane shows Tg at -54ºC by DSC method for polycaprolactone with Mn about 2000 g/mol. Presence of BHETA in the chemical

DMTA Results are shown in Figs. 20 and 21 for PU-22 and PU-38 respectively. Two main transitions are present in the DMTA spectra: a first peak (Tβ) located in the low-temperature region (at about -75°C and - 85°C) and a second peak (*T*α) seen in a higher temperature region (at about -25°C). Increasing in soft segments length caused to decrease Tβ of polyurethanes. The observed Tβ at –75ºC and –85ºC which was assigned to methylene sequence local relaxations, in analogy to results reported previously, is due to relaxation of caprolactone-based soft segments. It is found clearly that Tβ decreases with increasing of -

For the assignment of *T*α, we have considered a mixing-transition temperature (*T*mix), which would be the result of the various degrees of mixing between the ester and urethane blocks. According to this interpretation, the matrix would be formed by a PCL-rich continuous phase, in which PCL crystallites would be embedded, and amorphous PCL segments emerging from entangled domains with urethane segments would be connected to these crystallites. Some damping or fluctuations at higher temperatures is seen which corresponds to the hard-segments glass transition. As Shown in Figs. 20 & 21 E' in glassy region decreases with increasing of crystalline PCL soft segments length, whereas increases in rubbery plateau. The polymer with a higher content of PCL crystalline soft segments gives a higher E' in rubbery region for PU-38 in comparison with PU-22. TGA results shows that T90% and char residue decreases with increasing of molecular weight of soft segments for samples PU-22 to PU-142, which confirms decreasing in concentration of urethanes and aromatic groups in the samples. Also, presence of aromatic ring due to BHETA led to

CH2- units in caprolactone chains in sample PU-38 rather than PU-22.

structure results in increasing of Tg in our work.

**6.2.3 DMTA results** 

increasing of thermal satiability.

Fig. 20. DMTA thermogram of PU-22.

Fig. 21. DMTA thermogram of PU-38.

#### **6.2.4 Optical Microscopy (OM) and Scanning Electron Microscopy (SEM)**

Optical microscopy (OM) images shown in Fig. 22 illustrate the morphology of the synthesized PUs (scale bar shows 30 microns). OM results show rather smooth and rather rough structures for samples PU-22 and PU-38, while are fibrous-looking for PU-76 and PU-142.

Fig. 22. Optical microscopy images: (a) PU-22; (b) PU-38; (c) PU-76; (d) PU-142; (e) Disordered PU-76; (f) disordered PU-142.

From PET Waste to Novel Polyurethanes 377

to lower flexibility in polyol chain and finally higher Me in comparison to virgin polycaprolactone. Therefore, Mn of Polyol-76 (8720 g/mol) is lower than Me of BHETA containing polyols. The presence of entanglement in polymeric chains provided higher strength for this sample (Fig.25.c and Fig.25.d). It is interesting to obtain good tensile properties for synthesized polyurethanes in this study (especially for PU-22 and PU-38 which show higher hydrogen bonding confirmed by FTIR. This is explained by the fact that ordering degree of PCL blocks increases, and they are capable of forming crystalline structures, which promotes growth of their tensile strength and Young's modulus. It is noticeable that PU-22 and PU-38 were formulated without chain extender. Mechanical properties of novel polyurethanes in this work are comparable with similar commercial polyurethanes that already available. In this research we choose tensile test because of rapid biodegradation of samples and impossibility to weigh during and after decomposition. In order to compare

Fig. 24. b-Stress-Strain curves of PU-142: (a) before; (b) after biodegradability.

Fig. 25. Schematic chemical structures of PU-22 to PU-142.

a

b

c

d

Comparison shows as the soft segment length increases, the tendency to crystallization increases and formation of different structures is observed clearly. Circular regions with 200 µm diameters are seen for PU-142. DSC results confirm the presence of crystallites with sharp melting points from 36ºC-63.6ºC, which could be correlated to these structures. Rough structures are seen for samples PU-142 and PU-76, whereas PU-22 and PU-38 are less high. SEM results confirm the observed phenomena in OM images. Structures formed in the order of magnitude of *ca*10-100 nm and as Mn of soft segments increases, domains are larger.

#### **6.2.5 Tensile strength and biodegradability study**

Tensile strength and elongation at break of samples, before and after biodegradability tests, is shown in Figs. 23.a and 23.b which shows that elongation at break of PU-22 and strength of PU-38 has the highest values respectively.

Fig. 23. a-Stress-Strain curves of PU-22: (a) Before biodegradability test; (b) after biodegradability test (3 days in compost); (c) after biodegradability test (20 days in compost).

In contrast, elongation at break of PU-142 and PU-76 are lower than others dramatically. As shown in Fig. 24, PU-22 and PU-38 show elastomeric behavior. Of course, PU-38 shows necking; this isn't seen for PU-22, PU-76 and PU-142 show brittle behavior. Fig. 25 shows schematic chemical structures of PU-22 to PU-142. The observed necking could be correlated to extension of chain folding in chemical microstructure of PU-38 under constant force (Fig.25b). Very low strengths in samples PU-76 and PU-142 compared to PU-22 and PU-38 (Fig.25) are due to low concentration of urethane linkages and hydrogen bonding. More strength for PU-142 than PU-76, which is related to the soft segment molecular weight of this sample (Mn=16472 g/mol) that is more than entanglement molecular weight (Me) of polycaprolactone diol as *ca* 8000 g/mol.

The presence of BHETA leads to lower flexibility in polyol chain and finally higher Me in comparison to virgin polycaprolactone equal to *ca* 8000g/mol. The presence of BHETA leads

Comparison shows as the soft segment length increases, the tendency to crystallization increases and formation of different structures is observed clearly. Circular regions with 200 µm diameters are seen for PU-142. DSC results confirm the presence of crystallites with sharp melting points from 36ºC-63.6ºC, which could be correlated to these structures. Rough structures are seen for samples PU-142 and PU-76, whereas PU-22 and PU-38 are less high. SEM results confirm the observed phenomena in OM images. Structures formed in the order of magnitude of *ca*10-100 nm and as Mn of soft segments increases, domains are larger.

Tensile strength and elongation at break of samples, before and after biodegradability tests, is shown in Figs. 23.a and 23.b which shows that elongation at break of PU-22 and strength

Fig. 23. a-Stress-Strain curves of PU-22: (a) Before biodegradability test; (b) after

biodegradability test (3 days in compost); (c) after biodegradability test (20 days in compost).

In contrast, elongation at break of PU-142 and PU-76 are lower than others dramatically. As shown in Fig. 24, PU-22 and PU-38 show elastomeric behavior. Of course, PU-38 shows necking; this isn't seen for PU-22, PU-76 and PU-142 show brittle behavior. Fig. 25 shows schematic chemical structures of PU-22 to PU-142. The observed necking could be correlated to extension of chain folding in chemical microstructure of PU-38 under constant force (Fig.25b). Very low strengths in samples PU-76 and PU-142 compared to PU-22 and PU-38 (Fig.25) are due to low concentration of urethane linkages and hydrogen bonding. More strength for PU-142 than PU-76, which is related to the soft segment molecular weight of this sample (Mn=16472 g/mol) that is more than entanglement molecular weight (Me) of

The presence of BHETA leads to lower flexibility in polyol chain and finally higher Me in comparison to virgin polycaprolactone equal to *ca* 8000g/mol. The presence of BHETA leads

**6.2.5 Tensile strength and biodegradability study** 

of PU-38 has the highest values respectively.

polycaprolactone diol as *ca* 8000 g/mol.

to lower flexibility in polyol chain and finally higher Me in comparison to virgin polycaprolactone. Therefore, Mn of Polyol-76 (8720 g/mol) is lower than Me of BHETA containing polyols. The presence of entanglement in polymeric chains provided higher strength for this sample (Fig.25.c and Fig.25.d). It is interesting to obtain good tensile properties for synthesized polyurethanes in this study (especially for PU-22 and PU-38 which show higher hydrogen bonding confirmed by FTIR. This is explained by the fact that ordering degree of PCL blocks increases, and they are capable of forming crystalline structures, which promotes growth of their tensile strength and Young's modulus. It is noticeable that PU-22 and PU-38 were formulated without chain extender. Mechanical properties of novel polyurethanes in this work are comparable with similar commercial polyurethanes that already available. In this research we choose tensile test because of rapid biodegradation of samples and impossibility to weigh during and after decomposition. In order to compare

Fig. 24. b-Stress-Strain curves of PU-142: (a) before; (b) after biodegradability.

Fig. 25. Schematic chemical structures of PU-22 to PU-142.

From PET Waste to Novel Polyurethanes 379

Tables 3 and 4 give the various molar ratios used in the synthesis of PU-1 to PU-10 (with

Polyol (mol)

HDI (mol) Reaction Time (min)

Gel Time (min)

BHETA (mol)

PU-1b 1 1 0.14 0.06 1.2 6 - PU-5b 1.5 1 0.14 0.06 1.8 - 35 PU-3b 3 1 0.14 0.06 3.6 - 50 PU-4b 4 1 0.14 0.06 4.8 6 - PU-7b 7 1 0.14 0.06 8.4 6 - PU-10b 10 1 0.14 0.06 12 6 -

Polyol(mol) b: NCO/OH ratio in the polyurethane C: polyurethane without BHETA

As seen in the spectra of PU-3, PU-10 and PU-3-W (Fig. 26), strong inter-urethane hydrogen bonding is developed for all samples. Participating N–H group the hydrogen bond and nonbonded N–H group absorption displays a characteristic absorption band between 3300 and 3446 cm−1 and 3446 cm−1 respectively. FTIR spectrum of polyurethanes would display two carbonyl bands: one at 1707 cm−1 assigned to bonded C-O groups, and a second at 1731 cm−<sup>1</sup>

DSC and TGA results are shown, respectively, in Figs. 28a and 28b for samples PU-3 and PU-3-W. Comparison of DSC thermograms of PU-3 and PU-3-W shows the first endothermic peak at 150°C for PU-3-W, whereas it is at 190°C for PU-3 due to presence of BHETA in the chemical structure. DSC Thermograms in Figures 28a and 28b show

Exothermic crosslinking reactions are due to the thermodynamically favorable conformation that such interchain covalent bonds would promote. Conversely, the destruction of interchain hydrogen bonding, chain scission and pyrolysis reactions cause a DSC endotherm. The bond dissociation energy for a carbon–carbon single bond is relatively high

Conversely, for PU-3-W, crosslinking reactions predominate over destruction of urethane hydrogen bonding and chain scission. Dissociation or chain scission reactions in thermal degradation mechanisms of polyurethanes were summarized by Saunders *et al*. in four types of reactions that may take place during thermal degradation: (i) Dissociation to isocyanate and alcohol; (ii) formation of primary amino and olefin; (iii) formation of secondary amine; and (iv) transesterification-type bimolecular displacement. Therefore chain scission reactions in samples PU-3-W and PU-3 are indeed as shown in Fig 27. It has been shown

Table 4. Molar ratios of reactants to synthesis of PUs (without BHETA).

exothermic peaks for PU-3-W and endothermic peaks for PU-3.

(*ca* 375 kJ mol−1) and bond scission is endothermic.

BHETA) and PU-3-W and PU-10-W (without BHETA).

BD (mol)

Sample NCO/OH

<sup>a</sup>BD(mol) = 5

Molar ratio

**6.3.2 FTIR analysis of polyurethanes** 

assigned to free C-O groups.

**6.3.3 Thermal analysis** 

biodegradability of polyurethanes, dumbbells of various samples were maintained in compost (soil, straw, leaves, etc.) at 45ºC and 95% moisture and tensile strength tests have been achieved after 3 and 20 days. Stress-elongation curves of PU-22 to PU-142, before and after biodegradability test, are shown in Figs. 23 to 24 respectively. As shown in the figures strength and elongation at break have been reduced after 3 days in all samples. After 20 days all of polyurethanes decomposed except PU-22. However, mechanical properties of PU-22 have been reduced dramatically. More resistance of PU-22 to degradation is due to more concentration of urethane groups and less concentration of carbonyl groups in the polymer chains in this sample. Biodegradability of samples is comparable to polymers based on caprolactone; however presence of BHETA affects on biodegradability obviously.

#### **6.3 Synthesis of special polyurethanes**

Novel polyurethanes were synthesized based on prepared BHETA, 1,4-Butanediol (BD),Ether type Polyol and various molar ratio of Hexamethylene Diisocyanate (HDI). To evaluate the effect of BHETA, properties of polyurethanes without and with BHETA have been compared. FTIR, thermal transitions (DSC), degradation (TGA) of synthesized PUs have been investigated. (Shamsi et al, 2009).

#### **6.3.1 Materials and synthesis method**

PET staple waste fiber consists of short fibers with density of 1.45 g cm-3. PET staple waste fibers were boiled with methanol for 3 h to remove any surface finishing and dirt present in the fiber mass. Ethanolamine (EA), Ether type polyol (Polyol): Mn=2000 (Bayer), Sodium acetate,1,4-Butanediol (BD), Dibutyl Tin dilaurate (DBTDL), Hexamethylene Diisocyanate (HDI) were used as received. Polyurethanes were synthesized using a one-shot polymerization method. BHETA (0.0277 mol), Polyol (0.0119 mol), BD (0.198 mol) and DBTDL (7.78 × 10−4 mol) were dissolved in 200 mL of DMSO in a three-necked flask equipped with a condenser and stirrer. The temperature was raised to 90°C. Then desired amounts of HDI were added and the reaction mixed vigorously. In order to study the effect of BHETA on the polyurethane properties, two samples were synthesized without BHETA.


a BD(mol) = 5 BHETA(mol) + Polyol(mol) BHETA(mol) = 2.33 Polyol(mol) b NCO/OH ratio in the polyurethane

Table 3. Molar ratiosa of reactants to synthesis of PUs (with BHETA).

Polyol, BD and DBTDL were dissolved in 100 mL of DMF in a three-necked flask equipped with a condenser and stirrer. Then the desired amounts of HDI were added. After removing the mixtures from the reactor, they were post-cured and dried at 100°C for 8 h.

biodegradability of polyurethanes, dumbbells of various samples were maintained in compost (soil, straw, leaves, etc.) at 45ºC and 95% moisture and tensile strength tests have been achieved after 3 and 20 days. Stress-elongation curves of PU-22 to PU-142, before and after biodegradability test, are shown in Figs. 23 to 24 respectively. As shown in the figures strength and elongation at break have been reduced after 3 days in all samples. After 20 days all of polyurethanes decomposed except PU-22. However, mechanical properties of PU-22 have been reduced dramatically. More resistance of PU-22 to degradation is due to more concentration of urethane groups and less concentration of carbonyl groups in the polymer chains in this sample. Biodegradability of samples is comparable to polymers based

on caprolactone; however presence of BHETA affects on biodegradability obviously.

Novel polyurethanes were synthesized based on prepared BHETA, 1,4-Butanediol (BD),Ether type Polyol and various molar ratio of Hexamethylene Diisocyanate (HDI). To evaluate the effect of BHETA, properties of polyurethanes without and with BHETA have been compared. FTIR, thermal transitions (DSC), degradation (TGA) of synthesized PUs

PET staple waste fiber consists of short fibers with density of 1.45 g cm-3. PET staple waste fibers were boiled with methanol for 3 h to remove any surface finishing and dirt present in the fiber mass. Ethanolamine (EA), Ether type polyol (Polyol): Mn=2000 (Bayer), Sodium acetate,1,4-Butanediol (BD), Dibutyl Tin dilaurate (DBTDL), Hexamethylene Diisocyanate (HDI) were used as received. Polyurethanes were synthesized using a one-shot polymerization method. BHETA (0.0277 mol), Polyol (0.0119 mol), BD (0.198 mol) and DBTDL (7.78 × 10−4 mol) were dissolved in 200 mL of DMSO in a three-necked flask equipped with a condenser and stirrer. The temperature was raised to 90°C. Then desired amounts of HDI were added and the reaction mixed vigorously. In order to study the effect of BHETA on the polyurethane properties, two samples were

> Polyol (mol)

Polyol, BD and DBTDL were dissolved in 100 mL of DMF in a three-necked flask equipped with a condenser and stirrer. Then the desired amounts of HDI were added. After removing

PU-3**b**-W**<sup>c</sup>** 3 1 0.2 3.6 - 70 PU-10**b**-W**<sup>c</sup>** 10 1 0.2 12 6 -

BHETA(mol) + Polyol(mol) BHETA(mol) = 2.33 Polyol(mol) b NCO/OH ratio in the polyurethane

the mixtures from the reactor, they were post-cured and dried at 100°C for 8 h.

HDI (mol)

Reaction Time(min) Gel Time (min)

**6.3 Synthesis of special polyurethanes** 

have been investigated. (Shamsi et al, 2009).

**6.3.1 Materials and synthesis method** 

synthesized without BHETA.

Sample NCO/OH

a

ratio (mol)

BD(mol) = 5

BD (mol)

Table 3. Molar ratiosa of reactants to synthesis of PUs (with BHETA).


Tables 3 and 4 give the various molar ratios used in the synthesis of PU-1 to PU-10 (with BHETA) and PU-3-W and PU-10-W (without BHETA).

<sup>a</sup>BD(mol) = 5 Polyol(mol) b: NCO/OH ratio in the polyurethane C: polyurethane without BHETA

Table 4. Molar ratios of reactants to synthesis of PUs (without BHETA).

### **6.3.2 FTIR analysis of polyurethanes**

As seen in the spectra of PU-3, PU-10 and PU-3-W (Fig. 26), strong inter-urethane hydrogen bonding is developed for all samples. Participating N–H group the hydrogen bond and nonbonded N–H group absorption displays a characteristic absorption band between 3300 and 3446 cm−1 and 3446 cm−1 respectively. FTIR spectrum of polyurethanes would display two carbonyl bands: one at 1707 cm−1 assigned to bonded C-O groups, and a second at 1731 cm−<sup>1</sup> assigned to free C-O groups.

#### **6.3.3 Thermal analysis**

DSC and TGA results are shown, respectively, in Figs. 28a and 28b for samples PU-3 and PU-3-W. Comparison of DSC thermograms of PU-3 and PU-3-W shows the first endothermic peak at 150°C for PU-3-W, whereas it is at 190°C for PU-3 due to presence of BHETA in the chemical structure. DSC Thermograms in Figures 28a and 28b show exothermic peaks for PU-3-W and endothermic peaks for PU-3.

Exothermic crosslinking reactions are due to the thermodynamically favorable conformation that such interchain covalent bonds would promote. Conversely, the destruction of interchain hydrogen bonding, chain scission and pyrolysis reactions cause a DSC endotherm. The bond dissociation energy for a carbon–carbon single bond is relatively high (*ca* 375 kJ mol−1) and bond scission is endothermic.

Conversely, for PU-3-W, crosslinking reactions predominate over destruction of urethane hydrogen bonding and chain scission. Dissociation or chain scission reactions in thermal degradation mechanisms of polyurethanes were summarized by Saunders *et al*. in four types of reactions that may take place during thermal degradation: (i) Dissociation to isocyanate and alcohol; (ii) formation of primary amino and olefin; (iii) formation of secondary amine; and (iv) transesterification-type bimolecular displacement. Therefore chain scission reactions in samples PU-3-W and PU-3 are indeed as shown in Fig 27. It has been shown

From PET Waste to Novel Polyurethanes 381

**a b** 

that the endothermic behavior (T2 peak) is dissociation and degradation, resulting from long-range ordering and disordering of the hard segment domains in segmented polyurethanes. Some endothermic thermal transitions in DSC analysis of polyurethanes are due to structural decomposition of the polymer. As seen from the TGA and differential TGA (DTGA) thermograms (Figs 27(a) and (b)), weight reduction in PU-3-W begins at 140°C while it starts at about 235°C for PU-3. The first, second and third peaks in the DTGA trace of PU-3 are related to chain scission of urethane linkages, Polyol and BHETA, and isocyanurate and carbodiimide, respectively. 38 Also, the composition of various products was calculated as 20, 68 and 10.3 wt%, respectively. TGA of sample PU-3-W shows

> Char residue at 500 C (Wt. %)

Fig. 27. DSC and TGA thermograms of (a) PU-3-W and (b) PU-3.

continuous degradation, while in PU-3 three-step degradation is observed.

PU-3a 232 330 360 385 445 1.7 PU-3a-Wb 138 249 284 333 360 0.8 Table 5. Initial, 25%, 50%, 75% and 90% decomposition temperatures, and char residues.

The presence of BHETA in the chemical structure of polyurethane (due to longer chain extender and more hydrogen bonding in polyurethane chains) results in a shift of the beginning of degradation from 140 to 235°C and also three-step degradation. As shown in Table 5, the presence of the BHETA aromatic ring causes retardation of degradation. Also, a

Strength measured as maximum load (*F*m) of samples PU-4, PU-7, PU-10 and PU-10-W (applied on aluminum and iron substrates) is given in Table 6. As can be seen, addition of BHETA to polyurethane caused an increase of *F*m and elongation for both Fe-Fe and Al-Al substrates specifically. The surface preparation method (hand abrasion) for both Fe-Fe and Al-Al substrates was identical; therefore it can be concluded that the presence of BHETA causes stronger bonding as opposed to samples without BHETA. Strong bonds between the

Sample Tinitial T25% T50% T75% T90%

char residue of about 1.7 wt% is seen for PU-3 and 0.8 wt% for PU-3-W.

**6.3.4 Tensile shear strength** 

Fig. 26. FTIR spectra of PU-3, PU-10 and PU-3-W.

Fig. 26. FTIR spectra of PU-3, PU-10 and PU-3-W.

**a b** 

Fig. 27. DSC and TGA thermograms of (a) PU-3-W and (b) PU-3.

that the endothermic behavior (T2 peak) is dissociation and degradation, resulting from long-range ordering and disordering of the hard segment domains in segmented polyurethanes. Some endothermic thermal transitions in DSC analysis of polyurethanes are due to structural decomposition of the polymer. As seen from the TGA and differential TGA (DTGA) thermograms (Figs 27(a) and (b)), weight reduction in PU-3-W begins at 140°C while it starts at about 235°C for PU-3. The first, second and third peaks in the DTGA trace of PU-3 are related to chain scission of urethane linkages, Polyol and BHETA, and isocyanurate and carbodiimide, respectively. 38 Also, the composition of various products was calculated as 20, 68 and 10.3 wt%, respectively. TGA of sample PU-3-W shows continuous degradation, while in PU-3 three-step degradation is observed.


Table 5. Initial, 25%, 50%, 75% and 90% decomposition temperatures, and char residues.

The presence of BHETA in the chemical structure of polyurethane (due to longer chain extender and more hydrogen bonding in polyurethane chains) results in a shift of the beginning of degradation from 140 to 235°C and also three-step degradation. As shown in Table 5, the presence of the BHETA aromatic ring causes retardation of degradation. Also, a char residue of about 1.7 wt% is seen for PU-3 and 0.8 wt% for PU-3-W.

#### **6.3.4 Tensile shear strength**

Strength measured as maximum load (*F*m) of samples PU-4, PU-7, PU-10 and PU-10-W (applied on aluminum and iron substrates) is given in Table 6. As can be seen, addition of BHETA to polyurethane caused an increase of *F*m and elongation for both Fe-Fe and Al-Al substrates specifically. The surface preparation method (hand abrasion) for both Fe-Fe and Al-Al substrates was identical; therefore it can be concluded that the presence of BHETA causes stronger bonding as opposed to samples without BHETA. Strong bonds between the

From PET Waste to Novel Polyurethanes 383

respectively. As can be seen in Table 6, the lowest *F*m value is for PU-3-W on Al-Al substrate. Comparison of Fm for Fe-Fe and Al-Al samples shows higher values for the

This relates to higher mechanical interlocking due to the higher porosity of iron. The data obtained in the adhesion evaluation tests show a variation in *F*m for both substrates. The polyurethanes used have various NCO/OH molar ratios. Therefore *F*m can be related to free isocyanate groups. However, other parameters such as surface preparation method,

The swelling behavior of samples PU-3 to PU-10 with different solvents (DMSO, DMF, EA and Tol) was investigated at room temperature. The measured values of the polymer densities were in the range 1.13–1.2 g cm−3.Fig. 31 shows that the swelling ratio decreases with increasing NCO/OH ratio. Increasing the NCO/OH ratio also increases the crosslinking density, consequently causing a decreasing of the swelling ratio. As regards the effect of the solvent on the swelling ratio, it is seen that an increase of solubility parameter increases the swelling ratio for all NCO/OH ratios (solubility parameters (in (cal.cm−3)0*.*5)

Polyurethanes have been synthesized based on BHETA, HDI and polyethylene glycol via prepolymer method. Since catalyst and raw materials have low price, synthesis of BHETA is economical and could be used as diol to synthesis of polyurethanes. In this search, polyurethanes have been synthesized based on BHETA, HDI and polyethylene glycol via prepolymer method. TGA and DSC were carried out to study thermal stability, thermal transitions, Tm and Tg of synthesized polyurethanes. Effect of BHETA content in the main chain on thermal stability of polyurethanes, strength and stiffness has been evaluated.

moisture, evaporation of solvent, post-curing conditions, also affect the results.

former.

**6.3.5 Swelling behavior** 

(Mohammadi et al,2010)

are: DMSO, 12.87; DMF, 12.1; EA, 9.1; Tol, 8.9).

**6.4 Synthesis of high modulus polyurethanes** 

Fig. 29. Load–deformation curves for PU-4 on both substrates.

surface of the metal and polyurethane films, such as hydrogen bonds, are likely to be due to –NH groups in BHETA.

Fig. 28. Probable reactions in the degradation of polyurethanes.


Table 6. shows that the maximum loads for substrates Al-Al.

Figs 29-30 show load–deformation curves for, respectively, PU-4, PU-7 for both substrates. The load–deformation curves of the polyurethanes show brittle failure for Al-Al substrate as well as for Fe-Fe and Fe-Fe are different. The highest value of *F*m (3054 N) is observed for sample PU-10 on Fe-Fe substrate. Comparison of the maximum load for sample PU-10 with commercial epoxy and polyester-type adhesives shows a 2.03- and 2.34-fold increase,

surface of the metal and polyurethane films, such as hydrogen bonds, are likely to be due to

Fig. 28. Probable reactions in the degradation of polyurethanes.

Table 6. shows that the maximum loads for substrates Al-Al.

NCO/OH Ratio (mol)

PU-1a 1 - - PU-5a 1.5 - - PU-3a 3 - - PU-4a 4 2822.63 2168.13 PU-7a 7 2378 1959 PU-10b 10 3054.63 1968 PU-3 a -W b 3 - - PU-10 a -W b 10 1092.18 806.42

Figs 29-30 show load–deformation curves for, respectively, PU-4, PU-7 for both substrates. The load–deformation curves of the polyurethanes show brittle failure for Al-Al substrate as well as for Fe-Fe and Fe-Fe are different. The highest value of *F*m (3054 N) is observed for sample PU-10 on Fe-Fe substrate. Comparison of the maximum load for sample PU-10 with commercial epoxy and polyester-type adhesives shows a 2.03- and 2.34-fold increase,

Maximum load on Fe-Fe (N)

Maximum load on Al-Al (N)

–NH groups in BHETA.

Sample

respectively. As can be seen in Table 6, the lowest *F*m value is for PU-3-W on Al-Al substrate. Comparison of Fm for Fe-Fe and Al-Al samples shows higher values for the former.

This relates to higher mechanical interlocking due to the higher porosity of iron. The data obtained in the adhesion evaluation tests show a variation in *F*m for both substrates. The polyurethanes used have various NCO/OH molar ratios. Therefore *F*m can be related to free isocyanate groups. However, other parameters such as surface preparation method, moisture, evaporation of solvent, post-curing conditions, also affect the results.

#### **6.3.5 Swelling behavior**

The swelling behavior of samples PU-3 to PU-10 with different solvents (DMSO, DMF, EA and Tol) was investigated at room temperature. The measured values of the polymer densities were in the range 1.13–1.2 g cm−3.Fig. 31 shows that the swelling ratio decreases with increasing NCO/OH ratio. Increasing the NCO/OH ratio also increases the crosslinking density, consequently causing a decreasing of the swelling ratio. As regards the effect of the solvent on the swelling ratio, it is seen that an increase of solubility parameter increases the swelling ratio for all NCO/OH ratios (solubility parameters (in (cal.cm−3)0*.*5) are: DMSO, 12.87; DMF, 12.1; EA, 9.1; Tol, 8.9).

#### **6.4 Synthesis of high modulus polyurethanes**

Polyurethanes have been synthesized based on BHETA, HDI and polyethylene glycol via prepolymer method. Since catalyst and raw materials have low price, synthesis of BHETA is economical and could be used as diol to synthesis of polyurethanes. In this search, polyurethanes have been synthesized based on BHETA, HDI and polyethylene glycol via prepolymer method. TGA and DSC were carried out to study thermal stability, thermal transitions, Tm and Tg of synthesized polyurethanes. Effect of BHETA content in the main chain on thermal stability of polyurethanes, strength and stiffness has been evaluated. (Mohammadi et al,2010)

Fig. 29. Load–deformation curves for PU-4 on both substrates.

From PET Waste to Novel Polyurethanes 385

The test results of chemical resistant are shown in Table 8. Polyurethanes were soluble in DMF and DMSO and they were resistant in basic media (50wt %), of course with increasing BHETA, chemical resistance of polyurethane decreases. Aromatic ring leads to increasing distance between chains, therefore chemicals can penetrate in polymer matrix easily and the

> HDI (mol)

Dense HNO3

++: resistant −: un resistant, which number of −shows rate of decomposition

PU53 −−− −−− ++ ++ PU46 −−− −−− ++ ++ PU42 −− −− ++ ++ PU32 − − ++ ++

PU53 1 2.75 1.5 53.35 a PU46 1 2.2 1 46.54 a PU42 1 1.91 0.739 42 a PU32 1 1.42 o.29 32.49 a Table 7. Description of Samples and a indicates hard segment content of polyurethanes.

Hard Segment Content

> 23 wt% NaCl

BHETA (mol)

> 50 wt% NaOH

Fig. 32. Synthesis method for PUs.

polyurethane decomposes rapidly.

Sample H2SO4 98 wt%

Table 8. Results of chemical resistance tests.

Sample

**6.4.2 Chemical resistance & solubility tests** 

PEG (mol)

Fig. 30. Load–deformation curves for PU-7 on both substrates.

Fig. 31. Swelling ratio as a function of NCO/OH ratio for various solvents.

#### **6.4.1 Synthesis and characterization**

A 250 mL round-bottom flask equipped with a temperature controller, magnetic stirrer, reflux condenser, an N2 inlet, charged with Hexamethylene diisocyanate isocyanate(HDI), polyethylene glycol 1000 (PEG), DMF and Di-butyl Tin Dilaurate (DBTDL) (catalyst 1 wt%). HDI and PEG were reacted for 2 h at 75°C. The obtained prepolymer, then subjected to further reaction with BHETA. The reaction time was 3 h at 70°C. Molar ratio was fixed at 1.1 .The mixtures then were immediately cast on Teflon plates and then were kept in oven for 72 h at 70°C. Details of synthesis and method of synthesis are given in Table 7 and Fig. 32.

Fig. 30. Load–deformation curves for PU-7 on both substrates.

Fig. 31. Swelling ratio as a function of NCO/OH ratio for various solvents.

A 250 mL round-bottom flask equipped with a temperature controller, magnetic stirrer, reflux condenser, an N2 inlet, charged with Hexamethylene diisocyanate isocyanate(HDI), polyethylene glycol 1000 (PEG), DMF and Di-butyl Tin Dilaurate (DBTDL) (catalyst 1 wt%). HDI and PEG were reacted for 2 h at 75°C. The obtained prepolymer, then subjected to further reaction with BHETA. The reaction time was 3 h at 70°C. Molar ratio was fixed at 1.1 .The mixtures then were immediately cast on Teflon plates and then were kept in oven for 72 h at 70°C. Details of synthesis and method of synthesis are given in Table 7 and Fig. 32.

**6.4.1 Synthesis and characterization** 

Fig. 32. Synthesis method for PUs.

#### **6.4.2 Chemical resistance & solubility tests**

The test results of chemical resistant are shown in Table 8. Polyurethanes were soluble in DMF and DMSO and they were resistant in basic media (50wt %), of course with increasing BHETA, chemical resistance of polyurethane decreases. Aromatic ring leads to increasing distance between chains, therefore chemicals can penetrate in polymer matrix easily and the polyurethane decomposes rapidly.


Table 7. Description of Samples and a indicates hard segment content of polyurethanes.


++: resistant −: un resistant, which number of −shows rate of decomposition

Table 8. Results of chemical resistance tests.

From PET Waste to Novel Polyurethanes 387

Thermoplastic segmented polyurethanes display several thermal transitions. The soft phase, responsible of the properties at low temperatures, shows glass and melting transition (if semicrystalline), while the hard phase is responsible of the properties at high temperatures showing multiple melting transitions depending on the hard segment content in the matrix. As can be seen DSC graphs of the PU42 and PU46 shown in Fig. 35, one peak at –21.6 8C and –21.18 8C are appearance for PU42 and PU46, respectively. The peak appearing at the lower temperature might be associated with a soft segment glass transition temperature (Tgss). The destruction of interchain hydrogen bonding caused to a DSC endotherm. It seems that the peak at about 142°C in both PU4 and PU46 is related to breaking of hydrogen bonding which has been occurred in PU42 more than PU46. This phenomenon can be attributed to more aromatic rings exist in PU42 per unit length of chains whereas is less in PU46, thus higher flexibility in PU42 caused to higher possibility for hydrogen bonding formation. The third peak in 179°C and 173°C shows formed restructuring in PU42 and PU46, respectively. Apparent endothermic peaks could result from crystal structures. As hard segment content increases, position of the endothermic peaks is shifted to higher temperatures, which is indicative of better ordered hard domain .The peak at around 237°C

**6.4.4 DSC analysis** 

and 240°C is related to PU42 and PU46 respectively.

Fig. 35. DSC thermograms of PU42 and PU46.

#### **6.4.3 Mechanical properties**

Mechanical properties of synthesized polyurethanes are shown in Table 9. The results indicate that increasing of chain extender leads to increasing of strength and stiffness of polymer and decreasing in elongation at break. For example modulus increases from 106.37 MPa to 296.16 MPa in the samples PU46 and PU53 respectively. In fact, the BHETA has an important role in strengthening of polyurethane by increasing of hydrogen bonding (since BHETA has many sites for formation of hydrogen bond) between polyurethane chains effectively. As seen in the Fig. 33 modulus and strength of polyurethanes increases with increasing of BHETA content. As shown in Fig. 34, content of BHETA affect on behavior of stress-strain curve for synthesized polyurethane under tension. It seems elastic region of the curves increases as BHETA content increases.


Table 9. Mechanical properties of samples contain different hard segment content.

Fig. 33. Young's modulus (a) and max stress (b), as a function of hard segment content.

Fig. 34. Stress-Strain curves for PU42, PU46, and PU53: Two samples for each test).

#### **6.4.4 DSC analysis**

386 Material Recycling – Trends and Perspectives

Mechanical properties of synthesized polyurethanes are shown in Table 9. The results indicate that increasing of chain extender leads to increasing of strength and stiffness of polymer and decreasing in elongation at break. For example modulus increases from 106.37 MPa to 296.16 MPa in the samples PU46 and PU53 respectively. In fact, the BHETA has an important role in strengthening of polyurethane by increasing of hydrogen bonding (since BHETA has many sites for formation of hydrogen bond) between polyurethane chains effectively. As seen in the Fig. 33 modulus and strength of polyurethanes increases with increasing of BHETA content. As shown in Fig. 34, content of BHETA affect on behavior of stress-strain curve for synthesized polyurethane under tension. It seems elastic region of the

PU 53 296.16 9.18 45.82 PU 46 106.37 6.94 31.13 PU 42 62.68 5.72 51.99 PU 32 28.569 2.98 128.56

Table 9. Mechanical properties of samples contain different hard segment content.

Fig. 33. Young's modulus (a) and max stress (b), as a function of hard segment content.

Fig. 34. Stress-Strain curves for PU42, PU46, and PU53: Two samples for each test).

Max Stress (MPa)

Elongation at Break (%)

**6.4.3 Mechanical properties** 

curves increases as BHETA content increases.

Sample Young's modulus

(MPa)

Thermoplastic segmented polyurethanes display several thermal transitions. The soft phase, responsible of the properties at low temperatures, shows glass and melting transition (if semicrystalline), while the hard phase is responsible of the properties at high temperatures showing multiple melting transitions depending on the hard segment content in the matrix. As can be seen DSC graphs of the PU42 and PU46 shown in Fig. 35, one peak at –21.6 8C and –21.18 8C are appearance for PU42 and PU46, respectively. The peak appearing at the lower temperature might be associated with a soft segment glass transition temperature (Tgss). The destruction of interchain hydrogen bonding caused to a DSC endotherm. It seems that the peak at about 142°C in both PU4 and PU46 is related to breaking of hydrogen bonding which has been occurred in PU42 more than PU46. This phenomenon can be attributed to more aromatic rings exist in PU42 per unit length of chains whereas is less in PU46, thus higher flexibility in PU42 caused to higher possibility for hydrogen bonding formation. The third peak in 179°C and 173°C shows formed restructuring in PU42 and PU46, respectively. Apparent endothermic peaks could result from crystal structures. As hard segment content increases, position of the endothermic peaks is shifted to higher temperatures, which is indicative of better ordered hard domain .The peak at around 237°C and 240°C is related to PU42 and PU46 respectively.

Fig. 35. DSC thermograms of PU42 and PU46.

From PET Waste to Novel Polyurethanes 389

polyurethanes. At first use of ethanolamine for aminolytic degradation of PET waste has been investigated. Obtained product, BHETA has potential for further reactions to synthesize useful products such as polyurethanes which have important industrial applications. In our studies, BHETA has been used as an intermediate to produce useful materials based on PET waste. At first study, ring opening polymerization of caprolactone by BHETA was carried out and polyols with different Mn have been synthesized and then polyurethanes have been synthesized using above mentioned polyols. Increasing of Mn polycaprolactone diol leads to regular increasing in melting point, crystallinity and fusion heat of samples, tendency to crystallization and formation of ordered structures is observed clearly which confirm by SEM and OM. Thermal degradation is serious for the sample containing lowest aromatic concentration. Elongation at break of 4.7 to 520% and strength of 9.3 to 16 MPa for synthesized polyurethanes without chain extender has been obtained.

In second study, BHETA has been used as an additional chain extender to synthesize novel segmented polyurethanes used in adhesives and coatings. Strong hydrogen bonding was evident from the FTIR spectra for all synthesized polyurethanes (with and without BHETA). Different thermal behavior for polyurethanes with and without BHETA have been observed using TGA due exothermic or endothermic reactions during their degradation. Addition of BHETA to the polyurethanes caused an increase in maximum load (*F*m) and elongation for both Fe-Fe and Al-Al substrates. Comparison of the *F*m for the synthesized adhesive with those of commercial epoxy and polyester-type adhesives shows a 2.03 and 2.34-fold increase, respectively. Chemical resistance tests show a high resistance of the polyurethanes to alkaline, NaCl and water media, but a lower resistance in high-concentration acids.

In third study BHETA uses instead of common chain extenders to synthesize of novel segmented polyurethanes. BHETA has an important role in strengthening of polyurethane, increasing of BHETA content caused to obtain modulus as 300 Mpa, Maximum stress as 9.18 Mpa. Using of BHETA in production of polyurethane leads to obtain polyurethanes with suitable phase separation and mechanical properties, decrease in raw material costs as well

[1] Kloss J, Fernanda SM, Souza D, Edilsa R, Silva D, Jair Alves D, 656 Leni A, Sonia Faria Z

[3] Sivaram S, (1997) National seminar on recycling and plastics waste management,

[4] Barbozaa ES, Lopez DR, Amico SC, Ferreira CA (2009) Resour Concerv Recy 53:122.

[6] Mishra S, Goje AS, Zope VS (2003) Poly Plastics Technol Eng 42(4): 581–603.

Biodegradability tests show high rated biodegradation for all polyurethanes.

as green environment based on a PET waste recycled material.

(2006) Macromol Symp 245–246: 651–656

[2] Shukla SR, Harad AM, Jawale LS (2009) Polym Deg Stab 94: 604–609.

[7] Mishra S, Goje AS, Zope VS (2003) Polym React Eng 11(1): 79–99.

[9] Lamparter RA, Barna BA, Johnsrud DR (1985) US Patent 4542239.

**8. References** 

Sep:283–8.

[5] Pusztaszeri SF (1982) US Patent 4355175.

[10] Tindall GW, Perry RL (1991) US Patent 5045122.

[8] Schwartz J (1995) US Patent 5395858.

#### **6.4.5 TGA analysis**

Polyurethanes are comparatively thermally unstable polymers; decomposition temperature of the polyurethane depends on the polyurethane structure. Polyurethane degradation usually starts with the dissociation of the urethane bond, CO2 and isocyanate evaporation. Normally, three mechanisms of decomposition of urethane bonds have been proposed and reactions may proceed simultaneously: dissociation to isocyanate and alcohol, formation of primary amine and olefin and formation of secondary amine and carbon dioxide. Fig. 36 shows TGA curves of PU42 and PU46. The shapes of the weight loss curves of both polyurethanes are almost identical and degradation profiles of polyurethanes depend on the content of BHETA. It could be described with different values which are bringing in Table 10. Initial degradation temperature of PU42 is much higher than that of PU46. Generally, reduction of Tid for PU46 may be attributed to these facts: at first flexibility can affected on hydrogen bonding formation; PU42 is more flexible which leads to increase probability of hydrogen bonding formation as, mentioned in DSC tests.


Table 10. Results of the thermo gravimetric analysis of samples.

Second reason; as seen in DSC thermograms restructuring phenomenon occurred at about 170°C. It seems, in the case of PU42 restructuring is predominant rather to decomposition reactions, in restructuring phenomenon new bonds formed, that leads to higher thermal stability in PU42.

Fig. 36. TGA and DTG thermo grams for PU46 and PU42.

#### **7. Conclusions**

Recycling of polyethylene terephthalate (PET) by aminolysis breeds environmental benefits. There are few reports on the usage of recycled BHETA from PET to synthesis of

Polyurethanes are comparatively thermally unstable polymers; decomposition temperature of the polyurethane depends on the polyurethane structure. Polyurethane degradation usually starts with the dissociation of the urethane bond, CO2 and isocyanate evaporation. Normally, three mechanisms of decomposition of urethane bonds have been proposed and reactions may proceed simultaneously: dissociation to isocyanate and alcohol, formation of primary amine and olefin and formation of secondary amine and carbon dioxide. Fig. 36 shows TGA curves of PU42 and PU46. The shapes of the weight loss curves of both polyurethanes are almost identical and degradation profiles of polyurethanes depend on the content of BHETA. It could be described with different values which are bringing in Table 10. Initial degradation temperature of PU42 is much higher than that of PU46. Generally, reduction of Tid for PU46 may be attributed to these facts: at first flexibility can affected on hydrogen bonding formation; PU42 is more flexible which leads to increase probability of

hydrogen bonding formation as, mentioned in DSC tests.

T20% °C

Table 10. Results of the thermo gravimetric analysis of samples.

Fig. 36. TGA and DTG thermo grams for PU46 and PU42.

T30% °C

Second reason; as seen in DSC thermograms restructuring phenomenon occurred at about 170°C. It seems, in the case of PU42 restructuring is predominant rather to decomposition reactions, in restructuring phenomenon new bonds formed, that leads to higher thermal

Recycling of polyethylene terephthalate (PET) by aminolysis breeds environmental benefits. There are few reports on the usage of recycled BHETA from PET to synthesis of

PU 42 201 232 245 256 368 2.534 240 PU 46 172 203 220 233 351 5.100 250

T50% °C

Char Residue (%)

DTG (Max Temp.) °C

T10% °C

**6.4.5 TGA analysis** 

Sample Tid

stability in PU42.

**7. Conclusions** 

°C

polyurethanes. At first use of ethanolamine for aminolytic degradation of PET waste has been investigated. Obtained product, BHETA has potential for further reactions to synthesize useful products such as polyurethanes which have important industrial applications. In our studies, BHETA has been used as an intermediate to produce useful materials based on PET waste. At first study, ring opening polymerization of caprolactone by BHETA was carried out and polyols with different Mn have been synthesized and then polyurethanes have been synthesized using above mentioned polyols. Increasing of Mn polycaprolactone diol leads to regular increasing in melting point, crystallinity and fusion heat of samples, tendency to crystallization and formation of ordered structures is observed clearly which confirm by SEM and OM. Thermal degradation is serious for the sample containing lowest aromatic concentration. Elongation at break of 4.7 to 520% and strength of 9.3 to 16 MPa for synthesized polyurethanes without chain extender has been obtained. Biodegradability tests show high rated biodegradation for all polyurethanes.

In second study, BHETA has been used as an additional chain extender to synthesize novel segmented polyurethanes used in adhesives and coatings. Strong hydrogen bonding was evident from the FTIR spectra for all synthesized polyurethanes (with and without BHETA). Different thermal behavior for polyurethanes with and without BHETA have been observed using TGA due exothermic or endothermic reactions during their degradation. Addition of BHETA to the polyurethanes caused an increase in maximum load (*F*m) and elongation for both Fe-Fe and Al-Al substrates. Comparison of the *F*m for the synthesized adhesive with those of commercial epoxy and polyester-type adhesives shows a 2.03 and 2.34-fold increase, respectively. Chemical resistance tests show a high resistance of the polyurethanes to alkaline, NaCl and water media, but a lower resistance in high-concentration acids.

In third study BHETA uses instead of common chain extenders to synthesize of novel segmented polyurethanes. BHETA has an important role in strengthening of polyurethane, increasing of BHETA content caused to obtain modulus as 300 Mpa, Maximum stress as 9.18 Mpa. Using of BHETA in production of polyurethane leads to obtain polyurethanes with suitable phase separation and mechanical properties, decrease in raw material costs as well as green environment based on a PET waste recycled material.

#### **8. References**


**16** 

*University of Sfax* 

*Tunisia* 

**Valorization of Organic Wastes by** 

Hafedh Rigane and Khaled Medhioub

**Composting Process and Soil Amendment** 

Agricultural wastes disposal is becoming a serious environmental problem. Indeed, these residues may be highly polluting and phytotoxic. The removal of the produced solid and liquid residues is causing serious environmental problems. The direct application of organic wastes, such as olive husks or olive mill wastewaters, to soil has been considered as an inexpensive method of disposal in addition to the recovery of their mineral and organic components. Nevertheless, due to their ligno-cellulosic contents, olive husks are potentially environmentally harmful biomass. Fresh olive husks (not biologically stabilized) may have phytotoxicity due to their monogenic chemical composition (only lignin and cellulose), to phenols coming from olive oil processing, to its high Carbon/Nitrogen (C/N) ratio and to the presence of hormon inhibitors (De Bertoldi et al., 1986). According to several authors (De Jager et al., 2001; Palm et al., 2001), the improvement of soil fertility mainly under low input agricultural systems requires the input of stabilized or mature organic wastes. Many studies (Gallardo-Lara and Nogales, 1987; He et al., 1992; Ouédraogo et al., 2001; Stamatiadis et al., 1999) have shown that application of mature composts at reasonable rates improves plant

Composting in a controlled biooxidative process that involves a heterogeneous organic solid substrate may resolve this problem. It evolves through a thermophilic stage and the temporary release of phytotoxins, leading to the production of carbon dioxide, water, mineral salts and stabilized organic matter containing humic like substances. These kinds of fertilizers are used to improve soil fertility and plant production either in organic and

The main problems that can occur from excessive application of compost are plant toxicity due to salt content (Stamatiadis et al., 1999) and accumulation in plants of trace metals which may pose a health risk when humans or farm animals consume the plant (Petruzzelli,

Many wastes produced in important quantities are used for composting process such as solid wastes (olive husk, poultry manure) and also liquid wastes mainly the olive mill wastewaters which may be transformed into an organic fertilizer by composting. This is an inexpensive method of disposal leading to important advantages. The composted olive

growth, soil physical properties and increases available soil nutrient levels.

**1. Introduction** 

conventional agriculture.

1996; Cabrera et al., 1989).

*Unité de Recherche: Etude et gestion des Environnements côtier et urbain,* 

