Flow Behavior of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber (PP/EPDM/NR) Blends by Torque Rheometer: The Effect of N,N-m-Phenylene Bismaleimide (HVA-2) Addition

Blends of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) with different ratio were investigated using a Haake torque rheometer. The effect of N,N-m-phenylene bismaleimide (HVA-2) addition on the flow behavior of PP/EPDM/NR blends also was studied. The torque data was collected at different rotor speeds in the range of 30–60 rpm and different processing temperatures in the range of 170–190°C. The recorded data were interpreted in terms of apparent shear rate, apparent shear stress, and apparent viscosity. The shear stress–shear strain curve shows that all blends follow the power law where the pseudoplasticity behavior of melt viscosity increases with increasing NR content as well as addition of HVA-2. The apparent viscosity of the blends was found to increase with increasing NR content in the blend. The addition of HVA-2 increases the apparent viscosity due to the formation of cross-linking in rubber phase. However, blends with HVA-2 show lower flow activation energies than do similar blends without HVA-2. Scanning electron microscopy (SEM) shows good correlation with the flow properties of the blends.     

THE COMPARISON PROPERTIES OF RECYCLE RUBBER POWDER,CARBON BLACK,AND CALCIUM CARBONATE FILLED NATURAL RUBBER COMPOUNDS

The effects of filler loading on the curing characteristics, swelling behavior, and mechanical properties of natural rubber compounds were studied using a conventional vulcanization system. Recycle rubber powder (RRP), carbon black (CB) (N550), and calcium carbonate (CaCO₃) were used as fillers and the loading range was from 0 to 50 phr. Results show that the scorch time, t ₂, and cure time, t ₉₀, decrease with increase in filler loading. At a similar filler loading, RRP shows shortest t ₂ and t ₉₀ followed by CB and calcium carbonate. The tensile strength, tensile modulus, and hardness increase with increase in CB loading, whereas elongation at break, resilience, and swelling properties show opposite trend. For RRP and calcium carbonate filled natural rubber compounds, the tensile strength increases up to 10 phr and starts to deteriorate at higher filler loading. The other properties such as tensile modulus, hardness, elongation at break, resilience, and swelling percentage show a small change (increase or decrease) with increase in RRP and calcium carbonate loading in natural rubber compounds. Overall results indicate that RRP can be used as a cheapener to replace calcium carbonate in natural rubber compounds where improved mechanical properties are not critical.     

Mechanical and Morphological Properties of Polypropylene and Regenerated Tire-Rubber Blends

Mechanical properties and morphology of blends prepared from polypropylene (PP) and 5–20 wt% of regenerated tire-rubber (RgR) were studied. The samples were prepared in a twin-screw extruder. The addition of maleic anhydride-functionalized polypropylene (PP-g-MAH) was also investigated. Tensile and flexural moduli, tensile strength at break, elongation at break and Izod impact resistance at 23°C were increased by the addition of 15 wt% of regenerated rubber and 5 wt% of PP-g-MAH. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses showed some interaction between PP and RgR and considerable modification of the compatibilized mixture morphology. The fracture surface of the blend with PP-g-MAH showed a better interaction between the PP matrix and the regenerated rubber domains, for all blends. Well-dispersed particles of the rubber in the polypropylene matrix were observed. DSC showed that PP crystallizes on cooling at lower temperatures as the RgR content increases. The decrease in crystallization temperature is more evident for blends with 5 wt% PP-g-MAH.     

Study on polypropylene/natural rubber blend with polystyrene‐modified natural rubber as compatibilizer

Polystyrene‐modified natural rubber (SNR) was prepared in the laboratory and subsequently used as compatibilizer in polypropylene/natural rubber (PP/NR) blends. The effect of SNR (at 5%, 10%, 15% and 20% by volume) in PP/NR (70/30) blend was studied by maintaining the rubber volume while PP volume was replaced by SNR accordingly. The sequence of mixing was found to affect the blend morphology and tensile properties. The effect of curatives on the tensile properties of the blends was also investigated. The addition of curatives into the rubbers in PP/NR/SNR improved the tensile properties significantly compared with the PP/NR reference blend. For a semi‐efficient curative system, SNR loading at 10% gave the best overall tensile properties, while for an efficient curative system, 5% SNR loading resulted in improvements in tensile strength and stiffness of over 20% and 40%, respectively, compared with the reference. © 2002 Society of Chemical Industry     

CURE CHARACTERISTICS AND MECHANICAL PROPERTIES OF NATURAL RUBBER/RECLAIMED RUBBER BLENDS

Cure characteristics and mechanical properties of natural rubber/reclaimed rubber blends were studied. The minimum torque values of the blends were lower than that of the gum compound. The (maximum–minimum torque) and scorch time decreased with increasing reclaim content. The cure rate of the blends were lower than that of the virgin compounds. The tear strength was improved by the addition of reclaimed rubber. Tensile strength, elongation at break, and resilience decreased with increasing reclaim loading. The heat buildup was higher for the blends.     

Effects of Dynamic Vulcanization and Acrylic Acid on Properties of Recycled Poly(vinyl chloride)/Acrylonitrile Butadiene Rubber (PVCr/NBR) Blends

Effects of dynamic vulcanization and acrylic acid (AAc) on processability, mechanical properties, swelling behavior, morphology, and thermal stability of recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were investigated. Blends were prepared in a Haake Rheomix at a temperature of 150°C and a rotor speed of 50 rpm. Recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were also prepared as comparison. It was found that the dynamic vulcanization and the addition of acrylic acid improved the stabilization torque, mechanical energy, stress at peak, stress at 100% elongation (M₁₀₀), swelling resistance, and thermal stability but decreased the elongation at break of the blends. The introduction of a cross-link into the elastomer phase and better compatibility between PVCr and NBR are responsible for the enhancement of thermal stability and mechanical properties of dynamically vulcanized PVCr/NBR + AAc as evidence from the scanning electron microscopy (SEM) of the tensile fracture surfaces and infrared spectroscopy study of the dynamically vulcanized of PVCr/NBR + AAc shows.     

Comparison Properties of Natural Rubber (SMR L)/Ethylene Vinyl Acetate (EVA) Copolymer Blends and Epoxidized Natural Rubber (ENR-50)/Ethylene Vinyl Acetate (EVA) Copolymer Blends

Mixing torque, morphology, tensile properties and swelling studies of natural rubber/ethylene vinyl acetate copolymer blends were studied. Two series of unvulcanized blends, natural rubber/ethylene vinyl acetate (SMRL/EVA) copolymer blend and epoxidized natural rubber (50% epoxidation)/ethylene vinyl acetate (ENR-50/EVA) copolymer blend were prepared. Blends were prepared using a laboratory internal mixer, Haake Rheomix polydrive with rotor speed of 50 rpm at 120°C. Results indicated that mixing torque value and stabilization torque value in ENR-50 blends are lower than SMRL blends. The process efficiency of ENR-50/EVA blends is better due to less viscous nature of the blend compared to SMRL/EVA blends as indicated in stabilization torque graph. Tensile properties like tensile strength, M100 (modulus at 100% elongation) and E _b (elongation at break) increase with increasing EVA fraction in the blend. At the similar blend composition, ENR-50 blend shows better tensile properties than SMRL blends. In oil resistance test, swelling percentage increased with immersion time and rubber composition. At a similar immersion time, ENR-50 blends exhibit better oil resistance compared to SMRL blends. Scanning electron microscopy (SEM) of tensile fractured surface indicated that EVA/ENR-50 blends need higher energy to cause catastrophic failure compared to EVA/SMRL blends. In etched cryogenically fractured surface, size and distribution of holes due to extraction of rubber phase by methyl ethyl ketone (MEK) were studied and holes became bigger as rubber composition increased due to coalescence of rubber particle.     

The Effect of Dynamic Vulcanization on the Properties of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber (PP/EPDM/NR) Ternary Blend

The effects of dynamic vulcanization on the process development and some properties, such as tensile properties, swelling index, gel content, crystallinity, and morphology, of the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends were investigated. Dynamically vulcanized blends show higher stabilization torque than unvulcanized blends. In terms of tensile properties, the tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) of the vulcanized blends have been found to increase as compared with the unvulcanized blends, whereas the elongation at break is higher in the blend with richer EPDM content. These results can be attributed to the formation of cross-linking in the rubber phase. The formation of cross-links in the rubber phase has also been proved by swelling index and gel content. The percentage of crystallinity of the blends is decreased by dynamic vulcanization. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the cross-links occurred during dynamic vulcanization.     

Morphological evolution and mechanical property enhancement of natural rubber/polypropylene blend through compatibilization by nanoclay

Nanocomposites of natural rubber (NR)/polypropylene (PP) (80/20 wt %) blends filled with 5 phr pristine clay were prepared by melt‐mixing process. Effects of clay incorporation technique via conventional melt‐mixing (CV) and masterbatch mixing (MB) methods on nanostructure and properties of the blend nanocomposites were investigated. The XRD, SAXS, WAXD, and TEM results showed that the clays in the NR/PP blend nanocomposites were presented in different states of dispersion and were locally existed at the interface between NR and PP as well as dispersed in the NR matrix. The presence of clay caused unique morphological evolution such as fine fibrillar PP domains. The tensile strength was improved over the unfilled NR/PP blends by 53% and 224%, and the storage modulus at 25 °C was increased by 78% and 120% for the NR/PP/clay nanocomposites prepared by CV and MB methods, respectively. Significant improvement in both properties was particularly obtained from the MB method due to finer dispersion fibrillar PP phase in the NR matrix and stronger interfacial adhesion between NR and PP fibers, as suggested from DMA. The oil resistance of blend nanocomposites was also improved over that of the unfilled NR/PP blend, and this property was further progressed by the masterbatch mixing method. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44574.     

Properties of Polypropylene (PP)/Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Vulcanized Blends: The Effect of N,N-m-Phenylenebismaleimide (HVA-2) Addition

This paper discusses process development, tensile properties, morphology, oil resistance, gel content, and thermal properties of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) vulcanized blends with the addition of N,N-m-phenylenebismaleimide (HVA-2) as a compatibilizer. Blends were prepared in several blend ratios in a Haake Polydrive with temperature and rotor speed of 180°C and 50 rpm, respectively. Results indicated that the combination of dicumyl peroxide (Dicup) with HVA-2 shows high torque development and stabilization torque as compared to the blend with Dicup vulcanization alone. In terms of tensile properties, the combination of Dicup with HVA-2 shows higher tensile strength, tensile modulus (M₁₀₀), elongation at break, oil resistance, and gel content in all blend ratios compared to similar vulcanized blends with Dicup without HVA-2 addition. Scanning electron microscope (SEM) micrographs of the blends support that the cross-linking and compatibilization occur during the process of the vulcanized blend containing HVA-2. In the case of crystallinity of the blends, the addition of HVA-2 in Dicup vulcanized blend revealed a tendency for the percentage of crystallinity (Xc) to decrease. The addition of HVA-2 in Dicup vulcanization also produced blends with good thermal stability dealing with the so-called coagent bridge formation.     

Thermoplastic Elastomer Composites of Palm Ash-Filled Ethylene Vinyl Acetate/Natural Rubber Blends: Effects of Palm Ash Loading and Size

Thermoplastic elastomer composites of ethylene vinyl acetate (EVA)/natural rubber (NR) blends filled with palm ash were prepared by melt-mixing using a Haake Rheomix Polydrive R600/610 at 120°C with rotor speed of 50 rpm for 10 minutes. Increase in palm ash loading in composites resulted in increase the value of stabilization toque, Young's modulus and swelling resistance of the composites, but decreased the tensile strength and elongation at break. Scanning electron microscope micrographs revealed that higher filler loading resulted in agglomeration of palm ash in the composites. When smaller particle size of palm ash was used, further improvement in tensile strength, elongation at break, swelling resistance and stabilization torque value were observed.     

Studies on xanthate/dithiocarbamate accelerator combination in NR/BR blends

Zinc butyl xanthate [Zn(bxt)₂] was prepared in the laboratory. The effect of this xanthate with zinc diethyl dithiocarbamate (ZDC) on the vulcanization of natural rubber (NR), polybutadiene rubber (BR), and NR/BR blend has been studied at different temperatures. The amounts of Zn (bxt)₂ and ZDC in the compounds were optimized by varying the amount of ZDC from 0.75 to 1.5 phr and Zn (bxt)₂ from 0.75 to 1.5 phr. The cure characteristics were also studied. HAF filled NR, BR, and NR/BR blend compounds were cured at different temperatures from 60 to 150°C. The sheets were molded and properties such as tensile strength, tear strength, crosslink density and elongation at break, compression set, abrasion resistance, etc. were evaluated. The results show that the mechanical properties of 80NR/20BR blends are closer to that of NR vulcanizates, properties of 60NR/40BR blends are closer to BR vulcanizates, while the 70NR/30BR blends show an intermediate property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3516–3520, 2007     

Comparison of Properties of Polypropylene (PP)/Virgin Acrylonitrile Butadiene Rubber (NBRv) and Polypropylene (PP)/Recycled Acrylonitrile Butadiene Rubber (NBRr) Blends

The comparison properties of polypropylene (PP)/recycled acrylonitrile butadiene rubber (NBRr) blends and polypropylene/virgin acrylonitrile butadiene rubber (NBRv) blends were investigated. The tensile properties such as tensile strength, tensile modulus and elongation at break of PP/NBRv blends are higher than PP/NBRr blends. However, PP/NBRv blends exhibit lower stabilization torque and higher swelling percentage than PP/NBRr blends. Based on SEM, a finer morphology was observed in PP/NBRv blends in comparison with the PP/NBRr blends. The thermal stability of PP/NBRr is better than that of PP/NBRv blends.     

Morphology and tensile properties of high-density polyethylene/natural rubber/thermoplastic tapioca starch blends: The effect of citric acid-modified tapioca starch

The effect of citric acid on the tensile properties of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends was investigated. The ratio between HDPE/NR was fixed at 70/30 and used as the matrix system. TPS loadings, after modification with citric acid (TPSCA) and without modification (TPS), were varied from 0 to 30 wt %. The morphologies and tensile properties of HDPE/NR blends were evaluated as a function of TPS loadings. The tensile strength, Young's modulus, and elongation at break were found to decrease with increasing TPS loading. However, a slight improvement in the tensile strength of HDPE/NR/TPSCA blends at 5 and 10 wt % TPS loadings were observed. TPS can be partly depolymerised to produce a low viscosity product when processed with citric acid. TPS with low viscosity can easily disperse in the thermoplastic natural rubber (TPNR) system and reduce the surface tension at the interphase of TPS-HDPE/NR as shown by scanning electron microscopy (SEM). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

用废短纤维／橡胶复合材料制备纤维增强胶料

用废短纤维／橡胶复合材料，按ＣＮ８９１０５６５２．１技术处理制得４种ＳＦＲＣ母料。试验表明，其中ＳＦＲＣ２性能为最优，并分别与ＮＲ，ＢＲ，ＳＢＲ，ＮＢＲ，ＣＲ，ＩＩＲ等６种橡胶并用制得的纤维增强胶料，以ＮＲ为最好；用２种橡胶比ＳＦＲＣ２共混可改善加工行为，其胶料可制作Ｖ带，胶管，输送带，胶鞋等制品。     

Influence of incorporation methods of ATH on microstructure,elastomeric properties,flammability, and thermal decomposition of dynamically vulcanized NR/PP blends

Flame‐retardant thermoplastic vulcanizates (TPVs) of natural rubber (NR)/polypropylene (PP) (60/40 wt %) blends filled with alumina trihydrate (ATH) were prepared with an internal mixer. To increase the properties of flame‐retardant NR/PP TPV, the new mixing method, stepwise masterbatch mixing (SMB) method was adopted. The effects of SMB method along with different ATH loadings on microstructure and properties of NR/PP TPVs were investigated. Conventional one‐step mixing (CV) method was also studied for comparison. Transmission electron microscopy analysis showed that different processes led to a variation in microstructural homogeneity, which imposed various effects on blend properties. The mechanical properties of TPVs changed with ATH loading, and the strength of the samples obtained from SMB method was higher than those of CV method. LOI and cone calorimetry tests revealed that the flame retardancy of NR/PP blends dramatically increased at higher ATH loading. Furthermore, the increment level of flame retardancy was accelerated in the blends produced particularly through SMB method, resulting from homogeneity of local ATH distribution in NR/PP blend. Greater combustion resistance of blends prepared from SMB route were confirmed by thermogravimetry and pyrolysis‐gas chromatography–mass spectrometry techniques. Finally, a burning mechanism between filler structure and flammability of NR/PP TPVs obtained from CV and SMB methods was discussed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46231.     

Natural rubber/ethylene propylene diene blends for high insulation iron crossarms

This research studied the composition and behavior of natural rubber (NR) and ethylene propylene diene monomer (EPDM) blends at various carbon black concentrations (0–30 phr) in terms of electrical resistivity, dielectric breakdown voltage testing, and physical properties. The blends having electrical properties suitable for application in high‐insulation iron crossarms were selected for investigation of compatibility and increased physical properties. The effect of the homogenizing agent concentration on improvement of compatibility of blends was studied by scanning electron microscopy, pulsed nuclear magnetic resonance spectroscopy, and rheology techniques. We also examined mechanical properties such as tensile strength, tear strength, elongation at break, and hardness. The NR/EPDM blends filled with a fixed concentration of silica were investigated for ozone resistance. A carbon black content as high as 10 phr is still suitable for the insulation coating material, which can withstand electrical voltage at 10 kVac. Addition of the homogenizing agent at 5 phr can improve the mechanical compatibility of blends, as evidenced by the positive deviation of shear viscosity of the rubber blend, that is, the calculated shear viscosity being higher than that of experimental data. Moreover, the pulsed NMR results indicated that the spin‐spin relaxation (T₂) of all three components of the rubber blend was compressed upon the addition of the homogenizing agent. The ratio of NR/EPDM in the blend to best resist the ozone gas is 80/20 with the addition of silica of 30 phr into the blend. Also, the NR/EPDM filled with silica had a decreased change in thermal and mechanical properties of blends after thermal aging. The synergistic effect of silica content and high NR content (80) in 20 phr EPDM could improve antioxidation by ozone in the absence of a normal antioxidant for natural rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3401–3416, 2004     

PP／废旧橡胶／SBS复合材料的制备和力学性能研究

通过磨盘型力化学反应器制备PP/废旧橡胶(WTR)复合粉体，然后与SKS共混制备PP/WTR/SBS复合材料。研究了材料的力学性能、微观结构和共混物的加工性质。结果表明：当SBS添加量在20％～25％时，PP/WTR/SBS复合材料的力学性能较PP/WTR有了很大的提高，当SBS用量为25％时，断裂伸长率提高了365％，冲击强度提高了73．2％，而体系的拉伸强度基本不变。复合材料冲击断面的形貌和复合体系流变性能研究结果表明：磨盘碾磨可有效改善各组分间的混合性能，提高相容性并有效改善材料的加工性能。     

Effects of dynamic vulcanization on the physical,mechanical, and morphological properties of high‐density polyethylene/(natural rubber)/(thermoplastic tapioca starch) blends

Blending of high density polyethylene (HDPE), natural rubber (NR), and thermoplastic tapioca starch (TPS) have been studied. Two series of samples having 5–30 wt% of TPS were prepared: (a) unvulcanized blends (control) and (b) dynamically vulcanized HDPE/NR/TPS blends. The composition of the HDPE/NR was constant and fixed at a blend ratio of 70/30. Morphology studies by SEM showed that the TPS particles were homogeneously dispersed and well‐embedded in vulcanized HDPE/NR matrix. The SEM micrographs showed agreement with the tensile strength and elongation at break values. Tensile strength improved significanly when the HDPE/NR/TPS blends were vulcanized by using sulfur curative system. The enhancement in tensile properties is attributed to the crosslinking reaction within the NR phase. J. VINYL ADDIT. TECHNOL., 18:192–197, 2012. © 2012 Society of Plastics Engineers     

SORPTION,DIFFUSION, AND PERMEATION OF CHLORINATED HYDROCARBON VAPORS THROUGH NATURAL RUBBER,EPOXIDIZED NATURAL RUBBER,AND THEIR BLENDS

The study investigates the transport process of various chlorinated hydrocarbons through natural rubber (NR), epoxidized natural rubber (ENR), and their blends. The effect of structure and morphology of the membranes on the transport parameters has been investigated. Sorption coefficient is found to increase and the permeability coefficient shows the reverse trend with increasing epoxy content. As the mol% epoxidation increases, the polymeric network structure becomes more compact, which leads to a decrease in the diffusion coefficient, which ultimately results in a low permeation coefficient. The morphology of NR/ENR blends has been investigated by combining scanning electron microscopy with permeability measurements. The permeation coefficient is found to be minimum for the NR/ENR 70/30 composition; a 50/50 composition shows the maximum. The heterogeneous morphology of 70/30 NR/ENR blend results in the low permeability coefficient, whereas the co-continuous nature of the 50/50 composition accounts for the maximum permeability. Permeability measurements provide the most useful information about the way morphology is changing with composition of the blends and about the composition corresponding to the maximum level of co-continuity of the two phases.