**5.3. Synthesis of PUD based on glycolyzed products with molar ratio PET/glycol, 1:10**

Anionic PUD based on glycolyzed products with molar ratio PET/glycol, 1:10, were prepared by prepolymer mixing method in two steps: synthesis of NCO-terminated prepolymers and the preparation of dispersions by introducing anionic centers to aid dispersions (Athawale & Kulkarni, 2009). The prepolymer mixing method has been developed adjusting the molar ratio of DMPA to IPDI as 1:3, which was increased compared to the previous procedure. Mass of oligoester polyol, obtained by PET glycolysis, according to example 2, with a hydroxyl number which is equivalent to the hydroxyl number of 0.1 mol of poly(propylene glycol) PPG1000 (110 mg KOH/g), was for PG 54.5 g, TEG 52.6 g, poly (ethylene glycol) (PEG 400) 57.3 g. The mass of oligoester polyols and hydrophilic monomer was the same as in the previous procedure, but the mass of IPDI was (66.6 g, equ.0.3 mol). determined by molar ratio of a hydrophilic monomer to IPDI as 1:3. In order to obtain NCO terminated prepolymer, synthesis was controlled by determing the NCO groups by the dibutyl amine back-titration method until a theoretical value was achieved. The theoretical value of NCO groups for PUD based on oligoester polyol obtained from glycolysis with molar ratio of PET repeating unit to glycol, 1:10, was 14.2% for PG, 13.7%, for TEG and 13.9% for poly(ethylene glycol). The neutralization of the carboxylic groups in hydrophilic monomer, extension chain with EDA and the preparation of stable dispersion was done as in the previous modified acetone process. The solid content in this dispersion was 30%.

Films were prepared by casting the aqueous dispersions on the glass surface and allowing them to dry at room temperature for 7 days and then at 60 oC, for 12h (Coutinho, 1996, 2003). Films were cast by 100 μm applicators from the solutions onto glass surface (7cm x 2 cm) to obtain dry film thickness of 25-30 μm, making demoulding impossible. After demoulding, the films were kept into a desicator to avoid moisture. TG experiments were performed in a Perkin-Elmer TG-7 analyser. Film samples about 20 mg were placed in a platinum sample pan and heated from 30 to 600 oC, with an air flow of 200 mL min-1 and heating rates of 10 °C min-1. During the heating period, the weight loss and temperature difference were recorded as a function of temperature.

TGA was used to analyze decomposition behavior of cured films of PUD synthesized with glycolized products obtained from PET waste. TG curves are depicted in Figs. 4a,4c and 4e (curve marked as 1 a show lower molar ratio of PET / glycol (1:2) in the glycolized oligoester) represents the degradation of PUD influenced by the variation of oligoester polyols. It was verified that the thermal stability was influenced by glycol type and different molar ratio of PET repeating unit to glycol in glycolysis reaction. Figs. 4b, 4d and 4f depict the behavior of corresponding differential weight loss (DTG) curves.

**1:10** 

acetone by rotary vacuum evaporation at 35 oC.

difference were recorded as a function of temperature.

corresponding differential weight loss (DTG) curves.

PU anionomer was cooled to 30 oC then dispersed in water (50% of total mass) under high speed stirring for 30 min. The rate of water addition to the mixture was carefully controlled, to obtain a stable inversion. Upon completing the phase inversion, EDA (0.03 mol) was added for 60 min. at 35 oC. PUD of about 30 wt% solids was obtained upon removal of

**5.3. Synthesis of PUD based on glycolyzed products with molar ratio PET/glycol,** 

Anionic PUD based on glycolyzed products with molar ratio PET/glycol, 1:10, were prepared by prepolymer mixing method in two steps: synthesis of NCO-terminated prepolymers and the preparation of dispersions by introducing anionic centers to aid dispersions (Athawale & Kulkarni, 2009). The prepolymer mixing method has been developed adjusting the molar ratio of DMPA to IPDI as 1:3, which was increased compared to the previous procedure. Mass of oligoester polyol, obtained by PET glycolysis, according to example 2, with a hydroxyl number which is equivalent to the hydroxyl number of 0.1 mol of poly(propylene glycol) PPG1000 (110 mg KOH/g), was for PG 54.5 g, TEG 52.6 g, poly (ethylene glycol) (PEG 400) 57.3 g. The mass of oligoester polyols and hydrophilic monomer was the same as in the previous procedure, but the mass of IPDI was (66.6 g, equ.0.3 mol). determined by molar ratio of a hydrophilic monomer to IPDI as 1:3. In order to obtain NCO terminated prepolymer, synthesis was controlled by determing the NCO groups by the dibutyl amine back-titration method until a theoretical value was achieved. The theoretical value of NCO groups for PUD based on oligoester polyol obtained from glycolysis with molar ratio of PET repeating unit to glycol, 1:10, was 14.2% for PG, 13.7%, for TEG and 13.9% for poly(ethylene glycol). The neutralization of the carboxylic groups in hydrophilic monomer, extension chain with EDA and the preparation of stable dispersion was done as in the previous modified acetone process. The solid content in this dispersion was 30%.

Films were prepared by casting the aqueous dispersions on the glass surface and allowing them to dry at room temperature for 7 days and then at 60 oC, for 12h (Coutinho, 1996, 2003). Films were cast by 100 μm applicators from the solutions onto glass surface (7cm x 2 cm) to obtain dry film thickness of 25-30 μm, making demoulding impossible. After demoulding, the films were kept into a desicator to avoid moisture. TG experiments were performed in a Perkin-Elmer TG-7 analyser. Film samples about 20 mg were placed in a platinum sample pan and heated from 30 to 600 oC, with an air flow of 200 mL min-1 and heating rates of 10 °C min-1. During the heating period, the weight loss and temperature

TGA was used to analyze decomposition behavior of cured films of PUD synthesized with glycolized products obtained from PET waste. TG curves are depicted in Figs. 4a,4c and 4e (curve marked as 1 a show lower molar ratio of PET / glycol (1:2) in the glycolized oligoester) represents the degradation of PUD influenced by the variation of oligoester polyols. It was verified that the thermal stability was influenced by glycol type and different molar ratio of PET repeating unit to glycol in glycolysis reaction. Figs. 4b, 4d and 4f depict the behavior of

**Figure 4.** TG curves (a) and DTG curves (b) of PUD synthesized from glycolized oligoester PET/PG with molar ratio 1:2 (1) and 1:10 (2). TG curves (c) and DTG curves (d) of PUD synthesized from glycolized oligoester PET/TEG with molar ratio 1:2 (1) and 1:10 (2). TG curves (e) and DTG curves (f) of PUD synthesized from glycolized oligoester PET/poly(ethylene) glycol 400 with molar ratio 1:2 (1) and 1:10 (2).

PUD (synthesized from glycolized oligoester PET/PG (1:2), Fig. 4b) synthesized from depolymerised oligoesters with lower molar ratio of PET repeating unit to glycol in glycolysis reaction showed lower thermal stability in the initial stage of degradation may be due to the presence of greater amount of aromaticity in polyester backbone which makes the PU chains susceptible to scission and relieves the structure crowing (Athawale & Kulkarni, 2010). In later stage (above 300 oC), it showed enhanced thermal stability. It has also been proved that two or three peaks of first decomposition were well correlated with the higher value of polydispersity of GPC results (1.65), for oligoester polyols PET/PG (1:2) compared to the values of polydispersity (1.20), for oligoester polyols PET/PG(1:10). Curve marked as 2, in Figures 4b, 4d and 4f, which shifted third decomposition step temperature to the higher values, shows that glycolized oligoester obtained with higher molar ratio of PET/glycol of 1:10 have better thermal stability of obtained PUD.

Thermal Analysis of Polyurethane Dispersions Based on Different Polyols 95

**6. Waterborne PUD based on polycarbonate diols (PCD)** 

investigation of the role of the composition (Lee at al., 2004, 2006).

Solvent was added for reducing the viscosity, if necessary.

**6.1. Experimental** 

10 wt% to the prepolymer weight).

stirring the reaction mixture at 60 °

The polyols used in PUD synthesis are of polyether-, polyester-, polycaprolactone- and polycarbonate- origin. The use of individual types of polyol chains and their functionalities depend on the purpose of the potential use, e.g.; PUD made from polyesters can have slightly elevated strength and oil resistance compared to polyether-based PUD and have been largely used in PU paints as they exhibit outstanding resistance to light and aging. Polyether polyols are susceptible to light and oxygen when hot, however, they improve water dispersion, and impart chain flexibility (Gunduz & Kisakurek, 2004). The use of PCD in PUD, as compared to other polyols, imparts better hydrolysis resistance, improved ageing and oil resistance, excellent elastomeric properties even at low temperature, improved mechanical properties, good weathering and fungi resistance (Garcia et al., 2010). PCD used as the soft segment component in PUD synthesis are usually obtained from dimethylcarbonate or ethylene carbonate and a linear aliphatic diol (Foy et al., 2009). The properties of PUD are related to their chemical structure (Cakić et al., 2009; Athawale & Kulkarni, 2010) and are mainly determined by the interactions between the hard and soft segments, and the interactions between the ionic groups (Garcia et al., 2011). The properties of PUD are strongly influenced by composition and ionic content, an important target in an

Water-based PUD derived from IPDI, with different molar ratio PCD to DMPA, were prepared by the modified dispersing process. The ionic group content in PU-ionomer structure was varied by changing the amount of the internal emulsifier, DMPA (4.5, 7.5 and

Three waterborne PUD were prepared using NCO/OH = 1.5 by method in which the dispersing procedure was modified (Lee et al., 2006). In the modified procedure only the dispersing stage was varied compared to the standard procedure. The prepolymer solution was mixed with a small amount of deionized water for dispersion of polymer in water.

Into a 250 ml glass reaction kettle, equipped with a mechanical stirrer containing a torque meter, a thermometer, a condenser for reflux and nitrogen gas inlet, was added 60 g (0.03 mol) of PCD (dried under vacuum at 120 oC); and 4, 8 or 12 g (0.03, 0.06 or 0.09 mol) of DMPA dispersed in 30 ml DMF. The reaction mixture was heated at 70 oC for 0.5 h to obtain a homogeneous mixture. This step is important for the resulting equal uniform distribution of hydrophilic monomer, DMPA, on PU backbone. After that 20, 32 or 40 g (0.09, 0.15 or 0.18 mol) of IPDI and DBTDL (0.03 wt. % of the total solid) were added to the homogenized mixture and stirred at 80 oC for 2.5 h. Dibutyl amine back titration method was used for the determination of the reaction time necessary to obtain completely NCO-terminated prepolymer. Then the mixture was cooled down to 60 oC and carboxylic groups (DMPA equiv) were neutralized with TEA dissolved in NMP (2 wt % of the total reaction mass) by

C for 1h.

Because of the presence of oligoester polyols wich lower molecular weight in glycolysis reaction and a diamine were used in the synthesis of PUD, two kinds of hard segments are formed, urethane and urea. It has been estabilished that the urethanes have lower thermal resistance than urea and therefore the first decomposition process at about 190 - 250 oC and the second at about 270 – 290 oC of PUD should correspond to the urethane and urea hard segments, respectively. The decomposition temperature of the soft segment is observed at 400-430 oC. The decomposition temperature for investigated samples are listed in Table 1.


**Table 1.** Temperature of decomposition of PUD

The degradation profile of PUD was dependent on mole ratios of PET to glycol in glycolyzed products.

The samples based on PET/glycol, at molar ratio of 1:10, had better thermal stability than samples based on PET/glycol, at molar ratio of 1:2. The higher values of temperature for third decomposition stage, for samples with molar ratio of 1:10, probably is due to the increased length of glycol in glycolyzed oligoester polyol.
