Rubber Thermoplastic Elastomers Research Articles

Effects of Egg and Snail Shells on Biodegradation and Tensile Properties of Waste Plastics Fabricated Thermoplastics Elastomer Composites

The essence of this study is to proffer solution on the degradation of the environment caused by non-degradable plastics waste. A novel approach on plastic waste management was adopted by fabricating a thermoplastic natural rubber (TPNR) composite using waste Polyethyleneterephthalate {PET}plastics and eggshell as biofillers to initiate degradation by microorganism.Waste Polyethylene Terephthalates (PET) was grinded andmelted blended with Natural Rubber with 40pphr of Eggshell to fabricate a Natural Rubber Thermoplastic elastomer (TPNR) composite. The resultant thermoplastic elastomer composite was prepared for soil burial for a period of 90 days to obtain percentage weight loss as an indication of biodegradation. The NR/PET composite was evaluated for tensile properties. The results obtained were of the new that the tensile strength, elongation at break and modulus decreases with increase in soil burial duration time. The eggshell as a biopolymer has been shown to initiate biodegradation. There was a reduction in tensile strength at a blend ratio of 50/50 NR/PET blend, an indication that degradation has occurred, hence tensile properties are useful tools for the evaluationof biodegradation of polymeric materials

Microstructure-properties of dynamically vulcanized mengkuang leaf fibre/ethylene vinyl acetate/natural rubber thermoplastic elastomer composites

Thermoplastic elastomer composites based on ethylene vinyl acetate (EVA), natural rubber (NR), and Mengkuang leaf fibre were prepared using the sulfur and peroxide vulcanization systems. Different curing systems and fibre loadings affecting the processing torque, tensile, thermal, and morphology of the composites were investigated. Addition of Mengkuang leaf fibre resulted in poor fibre dispersion and agglomeration in the matrix, which may have affected the efficiency of stress transfer and thus could explain a decline in tensile and thermal properties. Composites with dynamic vulcanization showed a rougher surface that might be due to the presence of crosslinking, which requires more force to fail. The increase in stabilization torque for the composites with dynamic vulcanization was observed due to the addition of curing agents, which implies some changes at the molecular level due to crosslinking. Tensile properties of Mengkuang leaf fibre filled EVA/NR composites indicated that the tensile strength, elongation at break, and Young’s modulus of the peroxide cure system were higher than the sulfur cure system and unvulcanised composites. The sulphur cure system showed better resistance towards thermal degradation compared to the peroxide cure system. This was attributed to dicumyl peroxide (DCP), which degrades the polymer chain or the composites at high temperature.

Properties Enhancement of Mengkuang Leaf Fiber/Ethylene‐Vinyl Acetate/Natural Rubber Thermoplastic Elastomer Composites by Alkaline Peroxide Bleaching Treatment

In this article, the effect of alkaline peroxide bleaching treatment using hydrogen peroxide on mengkuang leaf fiber (MLF) to the tensile, thermal properties and water absorption of thermoplastic elastomer composites based on ethylene‐vinyl acetate/natural rubber and MLF was investigated. Fiber morphology and the fiber‐matrix interface were further characterized by scanning electron microscopy (SEM). Treated composites showed better tensile properties than untreated fiber composites. SEM of the fractured surfaces of the composite specimens indicates that the bleaching treatment improved the interfacial interaction between the fiber and the matrix. The results of thermogravimetric analysis showed a higher thermal stability for treated composites than untreated composites. Furthermore, alkaline bleaching treatment has resulted in reduction of water absorption from 31% to 26% as compared with untreated composites. J. VINYL ADDIT. TECHNOL., 26:127–134, 2020. © 2019 Society of Plastics Engineers

Synergistic effects of rare earth oxides on intumescent flame retardancy of Nylon 1010/ethylene-vinyl-acetate rubber thermoplastic elastomers

Synergistic effects of two kinds of rare earth oxides (REOs), samarium oxide (Sm2O3) or lanthanum oxide (La2O3) on the intumescent flame retardancy of Nylon 1010/ethylene-vinyl-acetate rubber (EVM) thermoplastic elastomers (TPE) were studied systemically. The limiting oxygen index (LOI) of intumescence flame retardant (IFR)-TPE increased from 30.5 to 32.5 and 34 when 0.5 wt% of IFR was substituted by La2O3 and Sm2O3, respectively. Sm2O3 showed higher synergistic effectivity than La2O3. Cone calorimetry tests confirmed that REOs enhanced flame retardancy of IFR-TPE. Smoke and CO production rate slightly decreased after incorporation of REOs as compared to IFR-TPEs without REOs, indicating relatively reduced combustion hazard. By thermalgravimetric analyses (TGA), it was found that the presence of REOs promoted the esterification and carbonization process in low-temperature range while enhanced the thermal stability of IFR and IFR-TPEs in high-temperature range. X-ray diffraction (XRD) proved that the interaction of Sm2O3 with IFR resulted in the formation of samarium phosphate (SmPO4) with high-thermal stability. Rheological measurements showed that the complex viscosities of the IFR-TPEs increased with the addition of REOs, which might aid in suppressing melt dripping. For mechanical properties, incorporation of REOs led to higher modulus, similar tensile strength but lower elongation at break as compared to IFR-TPEs without REOs.

Reinforcement of maleated polyethylene/ground tire rubber thermoplastic elastomers using talc and wood flour

AbstractMaleated polyethylene (MAPE)/Ground tire rubber (GTR) thermoplastic elastomer with 50 vol % GTR was reinforced by incorporation of talc powder and wood flour. Scanning electron microscopy (SEM) reveals that maleated polyethylene (MAPE) has good compatibility with wood flour, but the adhesion with talc particles is weak. Tensile moduli of MAPE/GTR increase more significantly after inclusion of talc particles compared to wood flour. Prediction of the tensile modulus of hybrid MAPE/GTR/particle composites is successfully performed using a combination of Kerner and Halpin‐Tsai models. Elastic moduli are shown to depend strongly on both aspect ratio and level of particle dispersion in the matrix. Measurement of compression sets shows that elastic recovery of the compounds decreases after addition of solid particles. Samples having better particles/matrix compatibility show higher elastic recovery. Thermogravimetric analysis shows that inclusion of wood flour decreases thermal stability of compounds. Density and hardness of MAPE/GTR are also shown to increase after inclusion of particulate reinforcements. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40195.

Degradation behavior of maleated polyethylene/ground tire rubber thermoplastic elastomers with and without stabilizers

This work investigates the effects of different degradation processes (weathering, thermal ageing and re-extrusion) on maleated polyethylene (MAPE), as well as MAPE/ground tire rubber (GTR) thermoplastic elastomers with and without stabilizers (thermal stabilizer, UVA and HALS). Mechanical characterizations revealed that GTR addition reduced compounds stability against thermal ageing at both 80 and 90 °C. But addition of stabilizers increased thermal stability of the MAPE phase. However, the results suggest that the stabilizers had no effect on the GTR phase. Mechanical characterizations also showed that weathering caused degradation in MAPE, while presence of stabilizers decreased the effects of degradation. Addition of GTR also increased significantly the stability of MAPE against weathering (due to presence of carbon black in GTR). Re-extrusion resulted in lower MAPE modulus (due to decreased molecular weight), while the modulus of GTR filled compounds increased. Re-extrusion also led to decreased GTR average particle size, especially at higher GTR contents. Morphological analyses showed that thermal ageing and re-extrusion did not change significantly blend morphology, but weathering, on the other hand, led to severe degradation of both MAPE and GTR filled compounds surface. Compression set of MAPE/GTR compounds was found to decrease with increasing degradation level (due to crosslinking). Finally, sample density slightly increased with degradation level (also due to crosslinking).

Microwave‐absorbing performance and mechanical properties of poly(vinyl chloride)/acrylonitrile–butadiene rubber thermoplastic elastomers filled with multiwalled carbon nanotubes and silicon carbide

AbstractPoly(vinyl chloride) (PVC)/acrylonitrile–butadiene rubber (NBR) were mixed with multiwalled carbon nanotubes (MWCNTs) and silicon carbide (SiC) to prepare microwave‐absorbing composites. The complex permittivity, direct‐current (dc) conductivity, microwave‐absorbing performance, morphology, and mechanical properties of the composites were studied. The real and imaginary parts of the permittivity of the composites increased with increasing MWCNT content. The premixing of the MWCNTs with PVC was more beneficial to the dispersion of MWCNTs; this led to a higher dc conductivity and permittivity and better microwave‐absorbing performance than the premixing of MWCNTs with NBR for the PVC/NBR/MWCNT composites. The PVC/NBR/MWCNT composites had a minimum reflection loss (RLmin) of −49.5 dB at the optimum thickness of 1.96 mm. The efficient microwave absorption of the PVC/NBR/MWCNT composites was due to a high dielectric loss and moderate permittivity. The incorporation of SiC into the PVC/NBR/MWCNT composites increased the real and imaginary parts of permittivity of the composites. When the SiC content was 70 phr, RLmin decreased to −34.9 dB at a thickness of 3 mm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Polypropylene/natural rubber thermoplastic elastomer: Effect of phenolic resin as a vulcanizing agent on mechanical properties and morphology

AbstractThe aim of this study is to characterize thermoplastic elastomers (TPEs) from polypropylene and natural rubber with and without phenolic resin as a vulcanizing agent. The blends containing 40–60 wt % of polypropylene were mixed in an internal mixer and pressed with a compression molding machine. TPEs without rubber vulcanization, named as unvulcanized thermoplastic natural rubber (uTPNR) were compared to TPEs containing dynamic vulcanized rubber, referred as vulcanized thermoplastic natural rubber (vTPNR). The uTPNRs illustrated cocontinuous phase morphology, whereas the vTPNRs displayed dispersed phase of vulcanized natural rubber. Tensile properties, tear strength, thermal ageing resistance, ozone resistance, tension set, hardness and swelling test in toluene, IRM 903 oil and engine oil were carried out according to ASTM. It was found that tensile and tear strength, hardness and tension set of the uTPNRs increased with increasing polypropylene content. Dynamic vulcanization improved tensile strength, elongation at break, tension set and degree of swelling of the TPEs, whereas hardness and tear strength did not show significant change after dynamic vulcanization. The vTPNRs exhibited higher ozone resistance and swelling resistance than the uTPNRs. Reprocessability of the vTPNRs was investigated and showed that tensile strength decreased at 20 and 30% and elongation at break decreased at 13 and 27% for the first and the third reprocessing respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The Effect of Prolonged Thermo-oxidative Ageing on the Mechanical Properties of Dynamically Vulcanized Poly(Vinyl Chloride)/Nitrile Butadiene Rubber Thermoplastic Elastomers

ABSTRACT Plasticized poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR) thermoplastic elastomers (TPEs) were dynamically vulcanized in the melt stage with the incorporation of a semi-efficient vulcanizing system using a Brabender Plasticorder at 150°C and 50 rpm rotor speed. Curative concentration was progressively increased from 0 to 1 part per hundred (phr) NBR in order to study the effect of dynamic curing on the plasticized blend. The mechanical properties investigated include tensile strength, elongation at break (%EB), modulus at 100% elongation (M100), tear strength, and hardness. The effect of thermo-oxidative ageing (TOA) on the mechanical properties was investigated by exposing the PVC/NBR TPEs in an air oven at 100°C for 3, 7, 14, and 21 days. It was found that tensile and tear strength passed through a maximum value, whereas, hardness and M100 increased steadily with the sulfur content and ageing time. On the contrary, the elongation at break reduced gradually with ageing time until it reaches a minimum value. The increase in crosslink density as well as the steady reduction in swelling index with increasing concentration of curatives provided an excellent evidence for the significant increase in crosslink density with ageing time. The changes in physical and mechanical properties of the TPEs is believed to be closely related to some microstructural changes taking place as a result of the formation of new crosslinks due to prolonged thermo-oxidative environment.

Structural study of natural rubber thermoplastic elastomers and their composites with carbon black by small-angle neutron scattering and transmission electron microscopy

Structures of natural rubber (NR)/high density polyethylene (HDPE) thermoplastic elastomers (TPE) and their composites with carbon black were investigated by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). TEM observations revealed that the carbon black nonoparticles were dominantly located in the NR domains of the TPE. The extremely low contrast between crystalline and amorphous HDPE for SANS enabled us to measure the interface thickness between NR and HDPE in the TPE (5–6 nm) as well as that between NR and carbon black in the composite (2.4 nm).

Oil Resistance of Dynamically Vulcanized Poly(Vinyl Chloride)/Nitrile Butadiene Rubber Thermoplastic Elastomers

Dynamically cured poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR), thermoplastic elastomers (TPEs) were melt mixed at 150°C at 50 rev.min.-1 with a Brabender Plasticorder. Curatives concentration was varied from 0 to 1 phr in order to study the effect of dynamic curing on the oil resistance of the plastified formulations. The compounds were characterized in respect to their mass swell, tensile properties, tear strength and hardness. The PVC/NBR formulations have been exposed to air and oil under otherwise identical conditions. The influence of oil and thermo-oxidative ageing on the mechanical properties were characterized at room temperature and 100°C. It was found that at ambient temperature the samples immersed in oil possessed similar properties to those that were exposed to air. Profound enhancement in mechanical properties were observed for both environments at 100°C. The observed scenario has been attributed to the increase in the degree of curing which was accompanied by a steady reduction in % mass swell with increased sulfur loading. The excellent mechanical behavior of the PVC/NBR TPEs even after immersing the samples in oil at 100°C evidenced for the good oil resistance of the materials.

Mechanical properties, morphological structure, and thermal behavior of dynamically photocrosslinked PP/EPDM blends

AbstractA dynamically photocrosslinked polypropylene (PP)/ethylene–propylene–diene (EPDM) rubber thermoplastic elastomer was prepared by simultaneously exposing the elastomer to UV light while melt‐mixing in the presence of a photoinitiator as well as a crosslinking agent. The effects of dynamic photocrosslinking and blend composition on the mechanical properties, morphological structure, and thermal behavior of PP/EPDM blends were investigated. The results showed that after photocrosslinking, tensile strength, modulus of elasticity, and elongation at break were improved greatly. Moreover, the notched Izod impact strength was obviously enhanced compared with corresponding uncrosslinked blend. Scanning electron microscopy (SEM) morphological analysis showed that for uncrosslinked PP/EPDM blends, the cavitation of EPDM particles was the main toughening mechanism; whereas for dynamically photocrosslinked blends, shear yielding of matrix became the main energy absorption mechanism. The DSC curves showed that for each dynamically photocrosslinked PP/EPDM blend, there was a new smaller melting peak at about 152°C together with a main melting peak at about 166°C. Dynamic mechanical thermal analysis (DMTA) indicated that the compatibility between EPDM and PP was improved by dynamic photocrosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3371–3380, 2004

Viscoelastic behavior of polypropylene/nitrile rubber thermoplastic elastomer blends: Application of Kerner's models for reactively compatibilized and dynamically vulcanized systems

AbstractThe viscoelastic properties of binary blends of nitrile rubber (NBR) and isotactic polypropylene (PP) of different compositions have been calculated with mean‐field theories developed by Kerner. The phase morphology and geometry have been assumed, and experimental data for the component polymers over a wide temperature range have been used. Hashin's elastic–viscoelastic analogy principle is used in applying Kerner's theory of elastic systems for viscoelastic materials, namely, polymer blends. The two theoretical models used are the discrete particle model (which assumes one component as dispersed inclusions in the matrix of the other) and the polyaggregate model (in which no matrix phase but a cocontinuous structure of the two is postulated). A solution method for the coupled equations of the polyaggregate model, considering Poisson's ratio as a complex parameter, is deduced. The viscoelastic properties are determined in terms of the small‐strain dynamic storage modulus and loss tangent with a Rheovibron DDV viscoelastometer for the blends and the component polymers. Theoretical calculations are compared with the experimental small‐strain dynamic mechanical properties of the blends and their morphological characterizations. Predictions are also compared with the experimental mechanical properties of compatibilized and dynamically cured 70/30 PP/NBR blends. The results computed with the discrete particle model with PP as the matrix compare well with the experimental results for 30/70, 70/30, and 50/50 PP/NBR blends. For 70/30 and 50/50 blends, these predictions are supported by scanning electron microscopy (SEM) investigations. However, for 30/70 blends, the predictions are not in agreement with SEM results, which reveal a cocontinuous blend of the two. Predictions of the discrete particle model are poor with NBR as the matrix for all three volume fractions. A closer agreement of the predicted results for a 70/30 PP/NBR blend and the properties of a 1% maleic anhydride modified PP or 3% phenolic‐modified PP compatibilized 70/30 PP/NBR blend in the lower temperature zone has been observed. This may be explained by improved interfacial adhesion and stable phase morphology. A mixed‐cure dynamically vulcanized system gave a better agreement with the predictions with PP as the matrix than the peroxide, sulfur, and unvulcanized systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1417–1432, 2004

Rheological and mechanical properties of dynamically cured poly(vinyl chloride)/nitrile butadiene rubber thermoplastic elastomers

AbstractPlasticized poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR) thermoplastic elastomers (TPEs) were dynamically cured in the melt stage with the incorporation of a semi‐efficient curing system using a Brabender Plasticorder at 150 °C and rotor speed of 50 rev min−1. Sulfur concentration was progressively increased from zero to 1 part per hundred NBR to study the effect of dynamic curing on mechanical and rheological behaviour of the TPEs. The compounds were characterized in respect of their rheological and mechanical properties. The effectiveness of dynamic curing was studied using Brabender plastograms, a moving disc rheometer and swelling index measurement. The mechanical properties investigated include tensile strength, elongation at break, modulus at 100% elongation, tear strength and hardness. The influence of thermooxidative ageing on the mechanical properties was investigated by incubating the PVC/NBR TPEs in an air oven at 80 °C for 168 h. The torque values obtained from both rheometers increased with increasing sulfur dosage, while the swelling index decreased. The significant increase in the degree of curing evidenced by the steady reduction in the swelling index provided excellent proof of the efficiency of the dynamic curing technique. Thermo‐oxidative ageing resulted in a pronounced enhancement in mechanical properties as a function of sulfur content. This observation seems to indicate that some microstructural changes, such as the formation of new crosslinks, occur in the thermo‐oxidatively aged TPEs. This trend was supported by further reduction in the swelling index of the aged TPEs.© 2003 Society of Chemical Industry

Finite element analysis of flow of thermoplastic elastomer melt through axisymmetric die with slip boundary condition

A finite element model for the flow of thermoplastic elastomers in extrusion dies has been developed. The rheological behaviour of the polymer melt is assumed to be described by the generalised Newtonian models and as a special case, the well known, power law equation was selected. Owing to the very low variation of the temperature field, the flow regime was considered to be isothermal. The set of governing equations are solved using the finite element method in a cylindrical (r, z) coordinate system. Slip–stick of the polymer melt on the solid wall, encountered in the flow of highly viscous fluids, is incorporated into the model by the use of Navier's slip condition. A new method based on a technique developed previously is described for the inclusion of this condition in the working equations. The applicability of the model was verified by a comparison between the results of the simulation of a polypropylene–nitrile/butadiene rubber thermoplastic elastomer with experimentally measured data. These comparisons show that there are very good agreements between the model predictions and actual data, provided that the slip of the polymer melt during the flow in extrusion die has been taken into consideration.

Rheological properties of dynamically vulcanized poly(vinyl chloride)/epoxidized natural rubber thermoplastic elastomers: effect of processing variables

The melt rheological behavior of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) thermoplastic elastomers (TPEs) was studied with a special reference to the effect of dynamic vulcanization, apparent shear rate and temperature using a twin screw capillary rheometer. PVC/ENR TPEs were compounded with a HAAKE twin screw extruder (WCT100). At a particular temperature it was found that the apparent viscosity decreased with increased in apparent shear rate following a pseudoplastic behavior, thus indicating that the dynamically vulcanized TPEs are processible as thermoplastics. The elastic phenomena was investigated by calculating the die swell which was found to be affected by the apparent shear rate and processing temperature. The extrudate surfaces at different apparent shear rates were studied by means of optical microscopy. It was observed that as apparent shear rate increases the extrudate surface exhibits a higher degree of deformation, the extent of which is also dependent on the sulfur concentration.

Oil-resistance studies of dynamically vulcanized poly(vinyl chloride)/epoxidized natural rubber thermoplastic elastomer

Dynamically vulcanized poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) thermoplastic elastomers (TPEs) were prepared with a Brabender plasticorder coupled with a mixing attachment by melt mixing. The blends were prepared at 150°C at a rotor speed of 50 rpm. Curatives concentration was steadily increased from 0 to 1 phr in order to study the vulcanization effect on the plasticized blend. The effectiveness of the dynamic vulcanization was indicated by the Brabender plastograms. The properties investigated include mass swell, tensile strength, elongation at break, modulus at 100% elongation (M100), tear strength, and hardness. The PVC/ENR samples were exposed to two types of environments, namely, air and oil under otherwise identical conditions. The effect of oil and thermooxidative aging on the mechanical properties were characterized at room temperature and 100°C. It was found that at ambient temperature the samples immersed in oil possessed similar properties to those that were exposed to air. Significant enhancement in mechanical properties were observed for both environments at 100°C. This has been attributed to the increase in crosslink density which was manifested by a steady reduction in percent mass swell with increased sulfur loading. The excellent mechanical behavior of the PVC/ENR TPEs even after immersing the samples in oil at 100°C has provided a good indication of the oil resistance of the materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1357–1366, 1998

The effect of an epoxidized plasticizer on the thermo-oxidative ageing of poly(vinyl chloride)/epoxidized natural rubber thermoplastic elastomers

The effects of an epoxidized plasticizer on the mechanical properties and thermo-oxidative ageing behaviour of poly(vinyl chloride)/epoxidized natural rubber thermoplastic elastomers (TPEs) were investigated. Aged and unaged blends were characterized by FTIR, tensile properties, tear strength, hardness and dynamic mechanical analysis (DMA). The properties of the epoxidized soya oil (ESO) plasticized TPEs were compared with those of the di-2-ethylhexylphthalate (DOP) plasticized counterparts. The presence of epoxide groups in ESO has been shown to produce two conflicting effects. On the one hand, the presence of excessive epoxide groups has resulted in poor ageing behaviour. On the other hand, it has resulted in a good interaction and compatibility with PVC/ENR. It was found that the tensile strength of the ESO plasticized blends were comparable with the DOP plasticized ones, but the elongation at break (EB) of the ESO blends fell short of that of the DOP blends. Also the retention of both tensile properties for the ESO blends was poorer than for DOP blends. Hardening and embrittlement also occurred in the ESO blends. Despite these weaknesses, ESO could be an ideal plasticizer for the PVC/ENR system as indicated by plasticizer permanence and the greater efficiency of plasticization. © 1998 SCI.

The effect of an epoxidized plasticizer on the thermo‐oxidative ageing of poly(vinyl chloride)/epoxidized natural rubber thermoplastic elastomers

The effects of an epoxidized plasticizer on the mechanical properties and thermo-oxidative ageing behaviour of poly(vinyl chloride)/epoxidized natural rubber thermoplastic elastomers (TPEs) were investigated. Aged and unaged blends were characterized by FTIR, tensile properties, tear strength, hardness and dynamic mechanical analysis (DMA). The properties of the epoxidized soya oil (ESO) plasticized TPEs were compared with those of the di-2-ethylhexylphthalate (DOP) plasticized counterparts. The presence of epoxide groups in ESO has been shown to produce two conflicting effects. On the one hand, the presence of excessive epoxide groups has resulted in poor ageing behaviour. On the other hand, it has resulted in a good interaction and compatibility with PVC/ENR. It was found that the tensile strength of the ESO plasticized blends were comparable with the DOP plasticized ones, but the elongation at break (EB) of the ESO blends fell short of that of the DOP blends. Also the retention of both tensile properties for the ESO blends was poorer than for DOP blends. Hardening and embrittlement also occurred in the ESO blends. Despite these weaknesses, ESO could be an ideal plasticizer for the PVC/ENR system as indicated by plasticizer permanence and the greater efficiency of plasticization. © 1998 SCI.

Chemical Surface Treatments of Natural Rubber and EPDM Thermoplastic Elastomers: Effects on Friction and Adhesion

Abstract Natural rubber thermoplastic elastomers (NRTPEs) made by dynamic vulcanization of natural rubber during its mixing with polypropylene were subjected to various halogenation surface treatments. Marked reduction in the coefficient of friction is possible depending on the chemical treatment employed, TPE composition and the presence of a lubricant. As a result of halogenation there is an increase in the microroughness and hardness of the NRTPE surface. These effects in part explain the large decrease in the friction coefficients since the contact area is decreased. Thus NRTPE can be employed in applications requiring low friction, such as certain types of seals. Another consequence of halogenation of NRTPE is the increase in its surface energy which in turn promotes adhesion to various polar substrates. Indeed it was determined that halogenation of NETPE is an effective way of priming the surface of these materials for adhesion to acrylic and other substrates. Ethylene Propylene Diene Monomer rubber-Polypropylene thermoplastic elastomers (EPTPEs) were used as a control in this study to assess how a low unsaturation EPDM-based TPE compares with the high unsaturation NRTPEs in different halogenation surface treatments.