**5. Influence of plasticizers on the properties of maleated EPDM ionic elastomers**

Ionic plasticizers play the role of promoting the ionic break-up of the ionic interactions at high temperatures to enable the shearing flow of the compound; at room temperature they behave like a filler. The most largely used ionic plasticizer is zinc stearate but some others can be also used, like calcium stearate, zinc acetate, stearamide.

Non-ionic plasticizers play the role of solvating the non-ionizing elastomer chains. They are chemically and thermally stable materials which are added to polymers to facilitate their processing, imparting flexibility and softness to the finished products. The major plasticizer functions in the polymer blends are the following: improving the processing and applications of long chain polymers; lowering the polymer processing temperature under their decay temperature; plasticizers decrease the intermolecular polymer forces, like the temperature does; changing the finished product characteristics, enabling the polymers to be used in specific fields requiring conditions which cannot be met by the unplasticized polymers. Plasticizers increase generally the polymer characteristics, such as flexibility, elongation, resistance to low temperatures but also can lower some characteristics like the tensile strength, the dielectric prperties, etc.; enlarging the application field because of their lower costs.

The action of the ionic plasticizer (zinc stearate) and non-ionic plasticizer (paraffin oil) on the ionic thermoplastic elastomer characteristics based on the maleinized ethylene propylene terpolymer rubber was discussed in order to select some optimum compositions for applications.

The prepared blends have shown different physico-mechanical characteristics according to the levels of the added plasticizer. Zinc stearate was used as plasticizer agent in concentrations of 20 and 40 phr, respectively and as nonionic plasticizer, paraffin oil in concentration of 10-50 phr.

increases with 25% as the filler level increases, while in compositions containing Royaltuf 498 the tensile strength increases with 37.7 % for carbon black level of 30 phr and then it decreases untill 22.6 %. The elongation at break decreases together with the increase of filler level. The most increase was observed in compositions containing precipitated silica. Tear strength increases against filler level for all compositions, the high values were obtained for

Also, the specific weight and abrasion resistance increase as the filler level becomes higher. However, the values of specific weight for compositions containing more than 60 phr of filler are very high and inadequate for use in shoes fabrication. The values of abrasion resistance confirm that these compounds can be used to manufacture "every day" shoes.

From Tabs. 5 and 6, the best characteristics of the compositions based EPDM-g-MA were obtained using as fillers carbon black and silica, occurring an increase of hardness, tensile strength and tear strength. Taking into account that a higher filler level leads to the decrease of melt composition viscosity and to the increase of specific weight and abrasion resistance, a rubber composition containing 30 phr carbon black or 30 phr precipitated silica could be

Ionic plasticizers play the role of promoting the ionic break-up of the ionic interactions at high temperatures to enable the shearing flow of the compound; at room temperature they behave like a filler. The most largely used ionic plasticizer is zinc stearate but some others

Non-ionic plasticizers play the role of solvating the non-ionizing elastomer chains. They are chemically and thermally stable materials which are added to polymers to facilitate their processing, imparting flexibility and softness to the finished products. The major plasticizer functions in the polymer blends are the following: improving the processing and applications of long chain polymers; lowering the polymer processing temperature under their decay temperature; plasticizers decrease the intermolecular polymer forces, like the temperature does; changing the finished product characteristics, enabling the polymers to be used in specific fields requiring conditions which cannot be met by the unplasticized polymers. Plasticizers increase generally the polymer characteristics, such as flexibility, elongation, resistance to low temperatures but also can lower some characteristics like the tensile strength, the dielectric prperties, etc.; enlarging the application field because of their

The action of the ionic plasticizer (zinc stearate) and non-ionic plasticizer (paraffin oil) on the ionic thermoplastic elastomer characteristics based on the maleinized ethylene propylene terpolymer rubber was discussed in order to select some optimum compositions

The prepared blends have shown different physico-mechanical characteristics according to the levels of the added plasticizer. Zinc stearate was used as plasticizer agent in concentrations of 20 and 40 phr, respectively and as nonionic plasticizer, paraffin oil in

selected in order to utilize in EPDM-g-MA compounds (Zuga et al., 2004).

can be also used, like calcium stearate, zinc acetate, stearamide.

**5. Influence of plasticizers on the properties of maleated EPDM ionic** 

compositions containing carbon black.

**elastomers** 

lower costs.

for applications.

concentration of 10-50 phr.

Figure 10 shows that adding the plasticizer (paraffin oil) for polymer chains has resulted in a decreased hardness (by 12oShA) but adding the ionic plasticizer (zinc stearate) has resulted in an increased hardness as the last one plasticizes the ionic groups at a temperature above the its melting point (128oC) and at the room temperature it acts like a filler (increases by 1oShA up to 11oShA). Hardness changes as a result of adding zinc stearate are more marked with the blend containing EPDM and 1 % maleic anhydride because of the enlarged ionic ranges.

An increase in elasticity with the increase in the amount of paraffin oil added to the blends was found out (Fig. 11); but the elasticity decreases as the amount of the added ionic plasticizer is increased and this decrease is more marked with blends containing EPDM and 1 % maleic anhydride. The blends containing EPDM and 1 % maleic anhydride show a higher elasticity with the decreasing in crystalline phase to the favour of amorphous phase.

Fig. 10. Changes in hardness according to the added plasticizer amounts. (a) for blends with Royaltuf 485; (b) for blends with Royaltuf 498

Fig. 11. Changes in elasticity according to the added plasticizer amounts: (a) for blends with Royaltuf 485 (b) for blends with Royaltuf 498

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 385

0

(a) (b) Fig. 15. Changes in tear strength according to the added plasticizer amounts. (a) for blends

**6. Influence of polyolefins on the properties of ionic thermoplastic elastomer** 

Some characteristics of the compositions based on EPDM-g-MA can be improved by adding other polymers in system. The choising of polymer type must be made as a function of its miscibility with the thermoplastic elastomer present already in composition. The selection of polymers to obtain blends with enhanced properties takes into account the following

Tear strength, N/mm

100

200

Elongatin at break, %

(a) (b) Fig. 14. Changes in elongation at break according to the added plasticizer amounts. (a) for

Tear strength decreases with the added paraffin oil and also with the increase in zinc

The ionic plasticizer has shown filler characteristics leading to some increase in hardness and decrease in elasticity, elasticity modulus, tensile strength and tear strength. Non-ionic plasticizer has solvated non-ionizable elastomer chains leading to some increase in elasticity

and elongation at break and decrease in hardness, tensile strength and tear strength.

 20 phr zinc stearate 40 phr zinc stearate 300

400

0 10 20 30 40 50 60

 20 phr zinc stearate 40 phr zinc stearate

 20 phr zinc stearate 40 phr zinc stearate

Paraffin oil level, phr

0 10 20 30 40 50 60

Paraffin oil level, phr

 20 phr zinc stearate 40 phr zinc stearate

0 10 20 30 40 50 60

Paraffin oil level, phr

0 10 20 30 40 50 60

Paraffin oil level, phr

with Royaltuf 485; (b) for blends with Royaltuf 498;

blends with Royaltuf 485; (b) for blends with Royaltuf 498

**compositions** 

Tear strength, N/mm

stearate level (Fig. 15).

Elongation at break, %

As can be seen in Figs. 12 and 13, paraffin oil solvates the non-ionic ranges leading to a decrease in elasticity modulus and tensile strength and this decrease is less marked with blends containing higher levels of zinc stearate. Increasing the zinc stearate levels in blends has resulted in an insignificant decrease in the elasticity modulus and tensile strength.

Elongation at break increases as the amount of paraffin oil added to the blends is increased and decreases as the amount of zinc stearate added to the blends is increased (Fig. 14). It decreases with high plasticizer levels.

Fig. 12. Changes in elasticity modulus and tensile strength according to the added amount paraffin oil to the blends of EPDM with 0.5 % maleic anhydride. (a) for the blends with 20 phr zinc stearate; (b) for the blends with 40 phr zinc stearate

Fig. 13. Changes in elasticity modulus and tensile strength according to the added amount paraffin oil to the blends of EPDM with 1.0 % maleic anhydride. (a) for the blends with 20 phr zinc stearate; (b) for the blends with 40 phr zinc stearate

As can be seen in Figs. 12 and 13, paraffin oil solvates the non-ionic ranges leading to a decrease in elasticity modulus and tensile strength and this decrease is less marked with blends containing higher levels of zinc stearate. Increasing the zinc stearate levels in blends has resulted in an insignificant decrease in the elasticity modulus and tensile strength.

Elongation at break increases as the amount of paraffin oil added to the blends is increased and decreases as the amount of zinc stearate added to the blends is increased (Fig. 14). It

> 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0

> > 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8

(a) (b)

Fig. 13. Changes in elasticity modulus and tensile strength according to the added amount paraffin oil to the blends of EPDM with 1.0 % maleic anhydride. (a) for the blends with 20

Elasticity modulus and tensile strength, N/mm2

(a) (b) Fig. 12. Changes in elasticity modulus and tensile strength according to the added amount paraffin oil to the blends of EPDM with 0.5 % maleic anhydride. (a) for the blends with 20

Elasticity modulus and tensile strength, N/mm2

10 20 30 40 50

 100% modulus, N/mm<sup>2</sup> 300% modulus, N/mm<sup>2</sup> Tensile strength, N/mm<sup>2</sup>

 100% modulus, N/mm<sup>2</sup> 300% modulus, N/mm<sup>2</sup> Tensile strength, N/mm2

Paraffin oil level, phr

10 20 30 40 50

Paraffin oil level, phr

decreases with high plasticizer levels.

10 20 30 40 50

 100% modulus, N/mm2 300% modulus, N/mm2 Tensile strength, N/mm<sup>2</sup>

Paraffin oil level, phr

10 20 30 40 50

Paraffin oil level, phr

phr zinc stearate; (b) for the blends with 40 phr zinc stearate

phr zinc stearate; (b) for the blends with 40 phr zinc stearate

 100% modulus, N/mm2 300% modulus, N/mm2 Tensile strength, N/mm2

2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

Elasticiy modulus and tensile strength, N/mm2

Elasticity modulus and tensile strength, N/mm2

Fig. 14. Changes in elongation at break according to the added plasticizer amounts. (a) for blends with Royaltuf 485; (b) for blends with Royaltuf 498

Tear strength decreases with the added paraffin oil and also with the increase in zinc stearate level (Fig. 15).

The ionic plasticizer has shown filler characteristics leading to some increase in hardness and decrease in elasticity, elasticity modulus, tensile strength and tear strength. Non-ionic plasticizer has solvated non-ionizable elastomer chains leading to some increase in elasticity and elongation at break and decrease in hardness, tensile strength and tear strength.

Fig. 15. Changes in tear strength according to the added plasticizer amounts. (a) for blends with Royaltuf 485; (b) for blends with Royaltuf 498;

#### **6. Influence of polyolefins on the properties of ionic thermoplastic elastomer compositions**

Some characteristics of the compositions based on EPDM-g-MA can be improved by adding other polymers in system. The choising of polymer type must be made as a function of its miscibility with the thermoplastic elastomer present already in composition. The selection of polymers to obtain blends with enhanced properties takes into account the following

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 387

0 20 40 60 80

HDPE, phr

0 20 40 60 80

HDPE, phr

0 20 40 60 80

HDPE, phr

0 20 40 60 80

HDPE, phr

Fig. 21. Dependence of tensile strength on HDPE level

Tensile strength, N/mm2

Tearing strength, N/mm

Fig. 20. Dependence of tear strength on HDPE level

300% Modulus, N/mm2

Fig. 18. 100% modulus versus the HDPE level

Fig. 19. 300% modulus versus the HDPE level

100% Modulus, N/mm2

criteria: structure, solubility, crystallinity degree, superficial tension, etrc. (Datta & Lohse, 1996, Utracki, 1998). According to these criteria polymers such as polypropylene, polyethylene (PE), maleated polyethylene (PE-g-MA), HDPE were selected to be used in compositions based on EPDM-g-MA.

Upon analyzing physico-mechanical characteristics of resulting blends, the following are noticed:


Fig. 16. Hardness versus the HDPE level

Fig. 17. Elasticity versus the HDPE level

Fig. 18. 100% modulus versus the HDPE level

criteria: structure, solubility, crystallinity degree, superficial tension, etrc. (Datta & Lohse, 1996, Utracki, 1998). According to these criteria polymers such as polypropylene, polyethylene (PE), maleated polyethylene (PE-g-MA), HDPE were selected to be used in

Upon analyzing physico-mechanical characteristics of resulting blends, the following are





0 20 40 60 80

HDPE, phr

0 20 40 60 80

HDPE, phr

increase of polyolefin amount in blends, but their values are good.

between the elastomer and polyolefin existing in the blend.

Elasticity, %

Hardness , ShA

Fig. 16. Hardness versus the HDPE level

Fig. 17. Elasticity versus the HDPE level

compositions based on EPDM-g-MA.

imprints surface properties on the blend.

noticed:

are additive.

Fig. 19. 300% modulus versus the HDPE level

Fig. 20. Dependence of tear strength on HDPE level

Fig. 21. Dependence of tensile strength on HDPE level

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 389

If the organomodified clay particles are dispersed in a polymer matrix three different types of structures can be found in nanocomposites: intercalated, flocculated and exfoliated. In the intercalated structures the polymer chains have penetrated into the layered structure maintaining the well-order multilayered nature. The flocculated structure is similar to the intercalated one, but the intercalated silicate layers sometimes flocculated because of the hydroxylated edge-edge interactions. The exfoliated structures of the silicate nanolayers are randomly dispersed throughout the polymer matrix. The exfoliated structures will determine enhanced properties of nanocomposites due to their higher phase homogeneity as compared to intercalated ones (Kang et al., 2007; Ray et al., 2003). XRD at small angles (2θ < 10o) and transmission electron microscopy (TEM) are effective methods to investigate these structures present in nanocomposites. XRD data reveal some peaks whose position is related to the basal spacing d001 and its broadness can give information about the distribution of spacings. In the exfoliated structures the interlayer spacing can be of the order of the gyration radius of the polymer and no peaks in their region are present due to the large d-spacings (10 nm) (Kang et al., 2007; Cole, 2008). Transmission electron microscopy gives the possibility to obtain data on the delaminated layers or intercalated stacks. The intercalation/exfoliation of layered clays is determined by compatibility of

Polymer/clay nanocomposites can be obtained by different methods, such as solution intercalation, in-situ intercalation polymerization and polymer melt intercalation. The melt compounding method is more advantageous due to its compatibility with current industrial polymer processing procedures and its environmental benefit determined by the lack of solvents (Kawasumi et al., 1997; Vaia & Giannelis, 1997). The properties of nanocomposites obtained by melt blending technique can be controlled by various parameters: molecular architecture of the alkylammonium cation used in ionic exchange, the presence of additives during silicate modification, processing temperature, the type and the content of

Because ethylene propylene diene terpolymer is a widely used material, EPDM/clay composites should be of great application potential. The homogeneous dispersion of silicate clay in polymer matrix occurs with difficulty because EPDM does not include polar groups in the polymer chain. In this case the modification of EPDM with maleic anhydride or the use of a compatibilizing agent can assure a good dispersability of organoclay in EPDM

The EPDM-gMA compositions were prepared by melt blending method using a Plasti-Corder Brabbender equipment at a temperature of 190 oC for 12 min as mix time. The organoclay (OMMT) was montmorillonite intercalated by octadecyltrimethylamine (Nanomer 128E). The other compounding ingredients such as zinc oxide, stearic acid, zinc strearate and antioxidant (Irganox 1010) were also utilized in formulations. PP-g-MA (1 % MA) was applied as compatibilizing agent (Stelescu et al., 2010). Three compositions containing EPDM-g-MA were prepared according to tab. 7. The compositions contain also compounding ingredients such as zinc oxide (10 g), stearic acid (1 g), zinc stearate (20 g) and Irganox 1010 (2 g). The resultant composites were homogenized on an electrically operated laboratory roller mill at 155-165°C. The test specimens for physico-mechanical measurements were obtained by pressing in an electrical press at 170°C for 5 min and

components, polymer diffusivity and processing conditions.

compatibilizer and polymer viscosity (Reichert et al., 2000).

matrix.

pressure of 150 MPa.

From the results obtained it was noticed that by increasing the quantity of HDPE introduced in EPDM-g-MA blends, hardness, modulus and tear strength increase and elasticity and residual elongation decrease. These effects prove that the properties of polymer blends depend on the characteristics of component polymers and on their molar fractions. The blend containing 80 phr polyethylene was selected, as it had the best values of hardness, modulus, tear strength and good values of tensile strength, elongation at break and elasticity (Zuga & Cincu, 2006c). This blend was used to make ionic thermoplastic elastomer granules in the laboratory extruder-granulator.

Fig. 22. Elongation at break versus HDPE level

Fig. 23. Residual elongation versus HDPE level

### **7. Nanocomposites based on maleated ethylene propylene diene monomer and clay**

In the last decades, polymer/layered clay nanocomposites (PCN) have attracted considerable attention in both basic research and industry exploitation because they possess a combination of properties that are not available in any of the single components. These systems exhibited improvements in mechanical properties, thermal stability, gas barrier properties, flame retardance, chemical and dimension stability (Stelescu et al, 2010). The clay mineral most used in elastomers/clay nanocomposites is montmorillonite, which have a layered structure consisting of two silicate tetrahedral sheets with an edge shared octahedral sheet of either aluminium or magnesium hydroxide (Ahmadi et al., 2005; Lowe et al., 2011). In order to obtain a nanoscale dispersion of clays in a polymer matrix, the silicates must be pretreated with alkylammonium ions to produce an organoclay (Tjong et al., 2002).

From the results obtained it was noticed that by increasing the quantity of HDPE introduced in EPDM-g-MA blends, hardness, modulus and tear strength increase and elasticity and residual elongation decrease. These effects prove that the properties of polymer blends depend on the characteristics of component polymers and on their molar fractions. The blend containing 80 phr polyethylene was selected, as it had the best values of hardness, modulus, tear strength and good values of tensile strength, elongation at break and elasticity (Zuga & Cincu, 2006c). This blend was used to make ionic thermoplastic elastomer granules

0 20 40 60 80

HDPE, phr

0 20 40 60 80

HDPE, phr

**7. Nanocomposites based on maleated ethylene propylene diene monomer** 

pretreated with alkylammonium ions to produce an organoclay (Tjong et al., 2002).

In the last decades, polymer/layered clay nanocomposites (PCN) have attracted considerable attention in both basic research and industry exploitation because they possess a combination of properties that are not available in any of the single components. These systems exhibited improvements in mechanical properties, thermal stability, gas barrier properties, flame retardance, chemical and dimension stability (Stelescu et al, 2010). The clay mineral most used in elastomers/clay nanocomposites is montmorillonite, which have a layered structure consisting of two silicate tetrahedral sheets with an edge shared octahedral sheet of either aluminium or magnesium hydroxide (Ahmadi et al., 2005; Lowe et al., 2011). In order to obtain a nanoscale dispersion of clays in a polymer matrix, the silicates must be

Residual elongation, %

Elongation at break, %

Fig. 22. Elongation at break versus HDPE level

Fig. 23. Residual elongation versus HDPE level

**and clay** 

in the laboratory extruder-granulator.

If the organomodified clay particles are dispersed in a polymer matrix three different types of structures can be found in nanocomposites: intercalated, flocculated and exfoliated. In the intercalated structures the polymer chains have penetrated into the layered structure maintaining the well-order multilayered nature. The flocculated structure is similar to the intercalated one, but the intercalated silicate layers sometimes flocculated because of the hydroxylated edge-edge interactions. The exfoliated structures of the silicate nanolayers are randomly dispersed throughout the polymer matrix. The exfoliated structures will determine enhanced properties of nanocomposites due to their higher phase homogeneity as compared to intercalated ones (Kang et al., 2007; Ray et al., 2003). XRD at small angles (2θ < 10o) and transmission electron microscopy (TEM) are effective methods to investigate these structures present in nanocomposites. XRD data reveal some peaks whose position is related to the basal spacing d001 and its broadness can give information about the distribution of spacings. In the exfoliated structures the interlayer spacing can be of the order of the gyration radius of the polymer and no peaks in their region are present due to the large d-spacings (10 nm) (Kang et al., 2007; Cole, 2008). Transmission electron microscopy gives the possibility to obtain data on the delaminated layers or intercalated stacks. The intercalation/exfoliation of layered clays is determined by compatibility of components, polymer diffusivity and processing conditions.

Polymer/clay nanocomposites can be obtained by different methods, such as solution intercalation, in-situ intercalation polymerization and polymer melt intercalation. The melt compounding method is more advantageous due to its compatibility with current industrial polymer processing procedures and its environmental benefit determined by the lack of solvents (Kawasumi et al., 1997; Vaia & Giannelis, 1997). The properties of nanocomposites obtained by melt blending technique can be controlled by various parameters: molecular architecture of the alkylammonium cation used in ionic exchange, the presence of additives during silicate modification, processing temperature, the type and the content of compatibilizer and polymer viscosity (Reichert et al., 2000).

Because ethylene propylene diene terpolymer is a widely used material, EPDM/clay composites should be of great application potential. The homogeneous dispersion of silicate clay in polymer matrix occurs with difficulty because EPDM does not include polar groups in the polymer chain. In this case the modification of EPDM with maleic anhydride or the use of a compatibilizing agent can assure a good dispersability of organoclay in EPDM matrix.

The EPDM-gMA compositions were prepared by melt blending method using a Plasti-Corder Brabbender equipment at a temperature of 190 oC for 12 min as mix time. The organoclay (OMMT) was montmorillonite intercalated by octadecyltrimethylamine (Nanomer 128E). The other compounding ingredients such as zinc oxide, stearic acid, zinc strearate and antioxidant (Irganox 1010) were also utilized in formulations. PP-g-MA (1 % MA) was applied as compatibilizing agent (Stelescu et al., 2010). Three compositions containing EPDM-g-MA were prepared according to tab. 7. The compositions contain also compounding ingredients such as zinc oxide (10 g), stearic acid (1 g), zinc stearate (20 g) and Irganox 1010 (2 g). The resultant composites were homogenized on an electrically operated laboratory roller mill at 155-165°C. The test specimens for physico-mechanical measurements were obtained by pressing in an electrical press at 170°C for 5 min and pressure of 150 MPa.

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 391

EPDM-g-MA sample shows a wide diffraction maximum centered at 2 = 20.65o due to amorphous phase. For the studied composites a diffraction peak appeared at around 2 = 6.54o. This peak at small diffraction angle scan be determined by the presence in composites of some diffraction centers formed by the aggregation tendency of ionic species leading to the formation of some microphases enriched in ions within polymer matrix and it can be attributed to interaggregated interface, the distances between ionic aggregates being Braag spaces while other authors assigned this peak to intraaggregated phase (Zuga, M.D. &

Fig. 24. X-ray diffraction patterns of organoclay (1) and EPDM nanocomposites: 2-EPDM-g-

The evolution of the weight loss of our composites with temperature is depicted in Fig. 25. Thermogravimetric analysis (TGA) was conducted on MOM Derivatograpgh at a heating rate of 10°C/min. The samples were heated in the temperature range from room to 750°C in air.The modified organoclay exhibits two stage of decomposition, the first corresponds to the elimination of absorbed free and interlayer water. In the second stage the degradation of organic material occurs starting at 220oC. The temperature at which the weight loss was 5%

MA/OMMT; 3-EPDM-g-MA/OMMT/PP-g-MA

can be considered the initial decomposition temperature (Td).

Cincu, C., 2006b; 2006c).


Table 7. EPDM-g-MA compositions


Table 8. Diffraction pattern characteristics of composites (according to Stelescu et al., 2010)

X-ray diffractometry is a powerful method to study the dispersion of organoclay in polymer matrix. It permitts the precise determination of silicate layer spacing and monitors the intercalation behavior of polymer chains. X-ray diffractograms were collected from a Bruker A8 Advance diffractometer with Ni-filtered Cu-Kα radiation (λ = 0.1541 nm) operating a tube voltage of 40 kV and a tube current of 35 mA. The diffractograms were scanned in 2θ range from 1°-30° at a rate of 1°/min. The interlayer spacing (d001-spacing) was evaluated by the Braag equation: λ = 2d sin θ, where θ is the diffraction angle, λ is the x-ray wavelength and d is the interlayer spacing. The modified organoclay shows two 2 peaks at 3.81o and 5.65o which correspond to a basal spacing of 2.32 and 1.56 nm, respectively (Fig. 24). For the nanocomposites EPDM-g-MA/OMMT and EPDM-g-MA/OMMT/PP-g-MA a high increase in d-spacing of the layered silicate was observed (Tab. 8) and the corresponding diffraction peak is shifted to lower 2 angles namely 2.24o. The shift of the sharp diffraction peak of organoclay from 2 = 3.81o to lower diffraction angles in our composites suggests that EPDM-g-MA has been able to intercalate into the gallery space of layered silicate, expanding the basal spacing of organoclay to 3.94 nm, which can clearly confirm the nanocomposite formation. The basal spacing increase in nanocomposites can be also influenced by the presence of hydrogen bondings between the maleic anhydride groups and the oxygen of silicate. The greater polarity of the EPDM-g-MA facilitates the interdiffusion of the polymer chains into the gallery spaces of the organoclay leading to a better dispersion of the nanoclay in polymer matrix. As given in Fig. 24, the EPDM-g-MA/PP-g-MA nanocomposite exhibits a diffraction peak at the same 2 with the same basal spacing relating to sample EPDM-g-MA (Tab. 8). It can be observed that the intensity of 2 diffractive peak at 2.24o is practically the same for nanocomposites EPDM-g-MA/OMMT and EPDM-g-MA/OMMT/PP-g-MA, a slight decrease was found out for the peak at about 4.72o for the composition containing compatibilizer PP-g-MA. The X-ray diffractogram of

3 EPDM-g-MA/OMMT/PP-g-MA

5.65 19.86 26.74

4.61 21.55 23.82

4.72 17.02 21.53 2.32 1.56 0.45 0.33

3.94 1.92 0.41 0.37

3.94 1.87 0.52 0.41

Code Compound 1 EPDM-g-MA

OMMT 3.81

EPDM-g-MA/OMMT 2.24

EPDM-g-MA/OMMT/PP-g-MA 2.24

Table 7. EPDM-g-MA compositions

2 EPDM-g-MA/OMMT

Sample 2 (o) d (nm)

Table 8. Diffraction pattern characteristics of composites (according to Stelescu et al., 2010)

X-ray diffractometry is a powerful method to study the dispersion of organoclay in polymer matrix. It permitts the precise determination of silicate layer spacing and monitors the intercalation behavior of polymer chains. X-ray diffractograms were collected from a Bruker A8 Advance diffractometer with Ni-filtered Cu-Kα radiation (λ = 0.1541 nm) operating a tube voltage of 40 kV and a tube current of 35 mA. The diffractograms were scanned in 2θ range from 1°-30° at a rate of 1°/min. The interlayer spacing (d001-spacing) was evaluated by the Braag equation: λ = 2d sin θ, where θ is the diffraction angle, λ is the x-ray wavelength and d is the interlayer spacing. The modified organoclay shows two 2 peaks at 3.81o and 5.65o which correspond to a basal spacing of 2.32 and 1.56 nm, respectively (Fig. 24). For the nanocomposites EPDM-g-MA/OMMT and EPDM-g-MA/OMMT/PP-g-MA a high increase in d-spacing of the layered silicate was observed (Tab. 8) and the corresponding diffraction peak is shifted to lower 2 angles namely 2.24o. The shift of the sharp diffraction peak of organoclay from 2 = 3.81o to lower diffraction angles in our composites suggests that EPDM-g-MA has been able to intercalate into the gallery space of layered silicate, expanding the basal spacing of organoclay to 3.94 nm, which can clearly confirm the nanocomposite formation. The basal spacing increase in nanocomposites can be also influenced by the presence of hydrogen bondings between the maleic anhydride groups and the oxygen of silicate. The greater polarity of the EPDM-g-MA facilitates the interdiffusion of the polymer chains into the gallery spaces of the organoclay leading to a better dispersion of the nanoclay in polymer matrix. As given in Fig. 24, the EPDM-g-MA/PP-g-MA nanocomposite exhibits a diffraction peak at the same 2 with the same basal spacing relating to sample EPDM-g-MA (Tab. 8). It can be observed that the intensity of 2 diffractive peak at 2.24o is practically the same for nanocomposites EPDM-g-MA/OMMT and EPDM-g-MA/OMMT/PP-g-MA, a slight decrease was found out for the peak at about 4.72o for the composition containing compatibilizer PP-g-MA. The X-ray diffractogram of EPDM-g-MA sample shows a wide diffraction maximum centered at 2 = 20.65o due to amorphous phase. For the studied composites a diffraction peak appeared at around 2 = 6.54o. This peak at small diffraction angle scan be determined by the presence in composites of some diffraction centers formed by the aggregation tendency of ionic species leading to the formation of some microphases enriched in ions within polymer matrix and it can be attributed to interaggregated interface, the distances between ionic aggregates being Braag spaces while other authors assigned this peak to intraaggregated phase (Zuga, M.D. & Cincu, C., 2006b; 2006c).

Fig. 24. X-ray diffraction patterns of organoclay (1) and EPDM nanocomposites: 2-EPDM-g-MA/OMMT; 3-EPDM-g-MA/OMMT/PP-g-MA

The evolution of the weight loss of our composites with temperature is depicted in Fig. 25. Thermogravimetric analysis (TGA) was conducted on MOM Derivatograpgh at a heating rate of 10°C/min. The samples were heated in the temperature range from room to 750°C in air.The modified organoclay exhibits two stage of decomposition, the first corresponds to the elimination of absorbed free and interlayer water. In the second stage the degradation of organic material occurs starting at 220oC. The temperature at which the weight loss was 5% can be considered the initial decomposition temperature (Td).

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 393

DSC determinations were utilized to characterize melting and crystallization behavior of composites based on EPDM-g-MA. Dynamic scanning calorimetry (DSC) measurements were performed on Perkin Elmer Pyris Diamond calorimeter, at a heating rate of 15°C/min. Figures 26 and 27 depict the DSC cooling and reheating melt thermograms of composites under study. Some of representative data from DSC scans are presented in Table 8 such as melting peak temperature (Tm), heat of fusion ( *H <sup>f</sup>* ), crystallization temperature (Tc). The melting process of EPDM-g-AM (nano)composites shows a broad endotherm peak between

Fig. 26. DSC thermograms of composites 1-EPDM-g-MA; 2-EPDM-g-MA/OMMT; 3-EPDM-

Fig. 27. DSC crystallization properties of composites 1-EPDM-g-MA; 2-EPDM-g-MA/OMMT; 3-EPDM-g-MA/OMMT/PP-g-MA.(according to Stelescu et al., 2010)

g-MA/OMMT/PP-g-MA(according to Stelescu et al., 2010)

65 and 130°C (Fig. 26).

Tab. 9 summarized the thermal analysis data such as temperature at 5% weight loss, decomposition temperature at maximum weight loss rate (Tmax), weight loss determined at the end decomposition (R). The three composites exhibit a very sharp weight loss of about 83% between 250 and 490oC, followed by a second short stage with maximum temperature near 510-530oC. As it can be noticed, the thermal stability of composition containing nanoclay and compatibilizer was increased slightly compared to initial sample EPDM-g-MA. Also, the char residue has higher values in the first two compositions (EPDM-g-MA/OMMT and EPDM-g-MA/OMMT/PP-g-MA). The thermal stability of EPDM-g-MA composites did not enhance as much, compared to the simple sample EPDM-g-MA. This small increase in thermal stability can be attributed to the clay nanolayers which can proceed as barriers to reduce the permeability of volatile degradation products from polymer matrix (Hsueh & Chen, 2003; Ahmadi et al., 2005). From Table 8 it can see that the organoclay practically does not decompose during processing or characterization of these materials.

Fig. 25. TGA curves of 1-EPDM-g-MA; 2-EPDM-g-MA/OMMT; 3-EPDM-g-MA/OMMT/PP-g-MA; 4-OMMT (according to Stelescu et al., 2010)


Table 9. Thermal characteristics of composites (according to Stelescu et al., 2010)

Tab. 9 summarized the thermal analysis data such as temperature at 5% weight loss, decomposition temperature at maximum weight loss rate (Tmax), weight loss determined at the end decomposition (R). The three composites exhibit a very sharp weight loss of about 83% between 250 and 490oC, followed by a second short stage with maximum temperature near 510-530oC. As it can be noticed, the thermal stability of composition containing nanoclay and compatibilizer was increased slightly compared to initial sample EPDM-g-MA. Also, the char residue has higher values in the first two compositions (EPDM-g-MA/OMMT and EPDM-g-MA/OMMT/PP-g-MA). The thermal stability of EPDM-g-MA composites did not enhance as much, compared to the simple sample EPDM-g-MA. This small increase in thermal stability can be attributed to the clay nanolayers which can proceed as barriers to reduce the permeability of volatile degradation products from polymer matrix (Hsueh & Chen, 2003; Ahmadi et al., 2005). From Table 8 it can see that the organoclay practically does not

decompose during processing or characterization of these materials.

Fig. 25. TGA curves of 1-EPDM-g-MA; 2-EPDM-g-MA/OMMT;

MA/OMMT/PP-g-MA 335 455 13.91 120.17

(°C)

Sample T5%

EPDM-g-

3-EPDM-g-MA/OMMT/PP-g-MA; 4-OMMT (according to Stelescu et al., 2010)

Tmax (°C)

Table 9. Thermal characteristics of composites (according to Stelescu et al., 2010)

R (%)

EPDM-g-MA 350 475 10.08 119.01 20.57 76.41

PP-g -AM 163.23 85.70 118.01

EPDM-g-MA/OMMT 340 460 13.31 120.52 22.07 74.02

Tm (°C)

162.34

Hf (J/g)

16.45 11.84

Tc (°C)

103.87

95.24

74.64 108.97 DSC determinations were utilized to characterize melting and crystallization behavior of composites based on EPDM-g-MA. Dynamic scanning calorimetry (DSC) measurements were performed on Perkin Elmer Pyris Diamond calorimeter, at a heating rate of 15°C/min. Figures 26 and 27 depict the DSC cooling and reheating melt thermograms of composites under study. Some of representative data from DSC scans are presented in Table 8 such as melting peak temperature (Tm), heat of fusion ( *H <sup>f</sup>* ), crystallization temperature (Tc). The melting process of EPDM-g-AM (nano)composites shows a broad endotherm peak between 65 and 130°C (Fig. 26).

Fig. 26. DSC thermograms of composites 1-EPDM-g-MA; 2-EPDM-g-MA/OMMT; 3-EPDMg-MA/OMMT/PP-g-MA(according to Stelescu et al., 2010)

Fig. 27. DSC crystallization properties of composites 1-EPDM-g-MA; 2-EPDM-g-MA/OMMT; 3-EPDM-g-MA/OMMT/PP-g-MA.(according to Stelescu et al., 2010)

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 395

**EPDM-g-MA**

**EPDM-g-MA/OMMT/PP-g-MA**

**EPDM-g-MA/OMMT/PP-g-MA**

**EPDM-g-MA**

**EPDM-g-MA/OMMT/PP-g-MA**

**EPDM-g-MA**

Fig. 29. Dependence of modulus 100% on nanoclay loading

Fig. 30. Dependence of elasticity on nanoclay level

Fig. 31. Tensile strength as a function of nanoclay content

The melting temperatures for the first stage were found to be almost the same for all samples. The small decrease of melting temperature with the introduction of PP-g-MA as well as the decrease of exothermic signal intensities can be due to the decrease of maleated polypropylene crystallization in composition in the presence of EPDM-g-MA. Therefore PPgAM retards the crystallization of PP. Especially as the incorporation of OMMT in composite (sample EPDM-g-MA/OMMT) determines the increase of Tm and of the fusion heat (Table 9) suggesting a supplementary nucleation increase due to the nanoclay presence. The crystallization temperature of PP-g-MA was around 118°C and this signal is shifted to 109°C after addition of OMMT and EPDM-g-MA in composition due to the limitation of chain mobility determined by the formation of hydrogen bonds between maleated EPDM and OMMT.

The mechanical properties of EPDM-g-MA (nano) composites under different OMMT loadings are presented in figures 28-33. Significant improvement in hardness, tensile strength, modulus and tear strength is clearly noticed for EPDM-g-MA/OMMT/PP-g-MA nanocomposites containing compatibilizer with the increasing of OMMT content. Only the elasticity decreases with the increase of OMMT level in composites (fig.30). The modulus and tensile strength increase rapidly with the increase of nanoclay loading (figs. 29 and 31) compared to that of MA sample. The enhancement in modulus and tensile strength shows that a better dispersion of layered silicate in polymer matrix in the presence of PP-g-MA as compatibilizer occurs and that the properties of the resulting polymer blends are additive. The tensile strength and elongation at break reach a maximum at about 2.5 phr of OMMT and then decrease (figs. 31 and 32), taking into account high nanoclay level and the ability of EPDM-g-MA to accept high loadings of clay diminishes. However, tensile strength and elongation at break of the uncompatibilized sample (EPDM-g-MA) show a minimum at 5 phr of OMMT content. This fact can be attributed to the decrease of ductibility while the stiffness become higher by reinforcing effect of OMMT layered silicate.

Tear strength and hardness exhibit a remarkable increase with increasing nanoclay level (figs. 28 and 33).

Fig. 28. Dependence of hardness on nanoclay content

Fig. 29. Dependence of modulus 100% on nanoclay loading

The melting temperatures for the first stage were found to be almost the same for all samples. The small decrease of melting temperature with the introduction of PP-g-MA as well as the decrease of exothermic signal intensities can be due to the decrease of maleated polypropylene crystallization in composition in the presence of EPDM-g-MA. Therefore PPgAM retards the crystallization of PP. Especially as the incorporation of OMMT in composite (sample EPDM-g-MA/OMMT) determines the increase of Tm and of the fusion heat (Table 9) suggesting a supplementary nucleation increase due to the nanoclay presence. The crystallization temperature of PP-g-MA was around 118°C and this signal is shifted to 109°C after addition of OMMT and EPDM-g-MA in composition due to the limitation of chain mobility determined by the formation of hydrogen bonds between maleated EPDM

The mechanical properties of EPDM-g-MA (nano) composites under different OMMT loadings are presented in figures 28-33. Significant improvement in hardness, tensile strength, modulus and tear strength is clearly noticed for EPDM-g-MA/OMMT/PP-g-MA nanocomposites containing compatibilizer with the increasing of OMMT content. Only the elasticity decreases with the increase of OMMT level in composites (fig.30). The modulus and tensile strength increase rapidly with the increase of nanoclay loading (figs. 29 and 31) compared to that of MA sample. The enhancement in modulus and tensile strength shows that a better dispersion of layered silicate in polymer matrix in the presence of PP-g-MA as compatibilizer occurs and that the properties of the resulting polymer blends are additive. The tensile strength and elongation at break reach a maximum at about 2.5 phr of OMMT and then decrease (figs. 31 and 32), taking into account high nanoclay level and the ability of EPDM-g-MA to accept high loadings of clay diminishes. However, tensile strength and elongation at break of the uncompatibilized sample (EPDM-g-MA) show a minimum at 5 phr of OMMT content. This fact can be attributed to the decrease of ductibility while the

Tear strength and hardness exhibit a remarkable increase with increasing nanoclay level

**EPDM-g-MA/OMMT/PP-g-MA**

**EPDM-g-MA**

stiffness become higher by reinforcing effect of OMMT layered silicate.

Fig. 28. Dependence of hardness on nanoclay content

and OMMT.

(figs. 28 and 33).

Fig. 30. Dependence of elasticity on nanoclay level

Fig. 31. Tensile strength as a function of nanoclay content

New Thermoplastic Ionic Elastomers Based on MA-g-EPDM with Advanced Characteristics 397

The potential users of the new rubber materials will be economic operators processing rubber and plastics, footwear and car component manufactures etc. They can be used in the manufacture of a large range of products like as hoses, gaskets, rubber shoes, protective

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[3] Cole, K. C. (2008). Use of infrared spectroscopy to characterize clay exfoliation in

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[5] Datta, S. & Lohse, D. J. (1996). Polymer Compatibilizers: Uses and Benefits in Polymer

[6] Eisenbach, C. D., Godel, A., Terskan-Reinold, M & Schubert, U. S. (1998). Thermoplastic

[8] Hsuech, H. B. & Chen, C. Y. (2003). Preparation and properties of LDHs/epoxy

[9] Kang, D., Kim, D., Yoon, S. H., Kim, D., Barry, C. & Mead, J. (2007). Properties and

[10] Kawasumi, M., Hasegawa, N., Kato, M., Usuki, A. & Okada, A. (1997). Preparation and

[11] Lowe, D. J., Chapman, A. V., Cook, S. & Busfield, J. C. Natural rubber nanocomposites by in situ modification of clay, Macromol. Mater. Eng., 296, 693-702. [12] Nahmias, N. & Marco Serra, A. (2002). Tires produced from carboxylated rubber

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Fig. 32. Effect of nanoclay loading on elongation at break

Fig. 33. Tear strength as a function of nanoclay content

This increase is due to the fact that the OMMT clay behaves as a reinforcing agent for the polymer matrix leading to the enhanced hardness.

#### **8. Conclusions**

The results confirm that the ionic thermoplastic elastomers based on EPDM-g-MA have properties similar to EPDM-based vulcanized rubber blends, and in addition, they can be easily processed using methods specific for thermoplastic materials, thus removing the vulcanization stage involving high power expenditure and release of noxious compounds determining improved characteristics (higher values for elasticity, ageing resistance, abrasive resistance, acid and alkali fastness) of the resulting materials.

Ionic thermoplastic elastomer granules can be used in various areas, due to specific properties such as resistance to water and diluted or concentrated acid and base solutions, resistance to accelerated aging, abrasion resistance or resistance to repeated bending.

The potential users of the new rubber materials will be economic operators processing rubber and plastics, footwear and car component manufactures etc. They can be used in the manufacture of a large range of products like as hoses, gaskets, rubber shoes, protective equipment etc.
