The effect of dynamic vulcanization on mechanical properties and water absorption of silica and rubberwood filled polypropylene/natural rubber hybrid composites

Dynamic vulcanized silica and rubberwood filled polypropylene (PP)/natural rubber (NR) hybrid composites were prepared using a Brabender plasticorder at 150°C and a rotor speed of 50 rpm for 12 minutes. The effectiveness of the dynamic vulcanization was indicated by the Brabender plastograms. The mechanical and water absorption properties of hybrid composites with different concentration of sulfur were investigated. Significant enhancement in mechanical properties, viz. tensile strength, stress at peak, Young modulus and flexural modulus were observed for dynamically vulcanized hybrid composites compared to unvulcanized hybrid composites. This has been attributed to the increase in crosslink density, which was manifested by a reduction of water absorption and increase of stabilization torque at the end of mixing stage with increasing sulfur concentration.     

The effects of dynamic vulcanization and compatibilizer on properties of paper sludge‐filled polypropylene/ethylene propylene diene terpolymer composites

The effects of dynamic vulcanization (DV) and dynamic vulcanization plus compatibilizer (DVC) of paper sludge (PS) filled polypropylene/ethylene propylene diene terpolymer (PP/EPDM) composites on torque development, mechanical properties, water absorption, morphology, and thermal properties were studied. Results show that DV and DVC composites exhibit higher stabilization torque than unvulcanized composites (UV). The dynamic vulcanized (DV) and dynamic vulcanized plus compatibilizer (DVC) composites exhibit higher tensile strength, elongation at break, and Young's modulus but lower water absorption than unvulcanized composites. The scanning electron microscopy (SEM) study of tensile fracture surface of DV and DVC composites shows the improved interfacial interaction between PS and PP/EPDM matrix. The DV and DVC composites also exhibit better thermal stability and higher crystallinity than unvulcanized PP/EPDM/PS composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blends of polyacetal and ethylene-octene elastomer: Mechanical,dynamic mechanical and morphological properties

Polyacetal (POM) and ethylene octene copolymer(EOC) elastomers form immiscible blends with extremely low compatibility. In order to improve the dispersion, stability and properties of these blends, dynamic vulcanization was carried out in a twin screw extruder using dicumyl peroxide. The tensile strength decreased with increase in % elongation at break for both blend systems. There was a drastic decrease in impact strength for unvulcanized blends as the elastomer content increased and this was attributed to the coalescence of the elastomer particles as their content increased. In the case of dynamically vulcanized blends there was a significant increase in impact strength as the levels of elastomer increased. Dynamic mechanical analysis has been carried out to investigate the effect of blend composition and dynamic vulcanization on dynamic mechanical parameters such as storage modulus, loss modulus and loss factor. The results indicate gross incompatibility of POM and EOC blends. However, dynamically vulcanized blends show better adhesion between component polymers. The morphological studies reveal that the particle size and coalescence of elastomer was significantly reduced in comparison to unvulcanized bends. The phase adhesion was improved by dynamic vulcanization. Hence, it was observed that dynamic vulcanization effectively improves the morphology of the blend system and enhances the properties of polyacetal.     

Water absorption behavior and its effect on tensile properties of ethylene–propylene–diene–terpolymer/polypropylene/filler ternary composites: a preliminary study

The water absorption behavior of white rice husk ash (WRHA) and silica filled ethylene-propylene-diene-terpolymer/polypropylene (EPDM/PP) ternary composites was studied with special reference to filler type, test specimen preparation (die cut or molded), and dynamic vulcanization of elastomer phase. The water uptake of composites was recorded as a function of them over 40 days of immersion period in distilled water. The influence of final water uptake on tensile properties of the composites was also studied. White rice husk ash filled composites and molded composites exhibit lower water uptake when compared to silica and die cut composites, respectively. All vulcanized composites showed lower water uptake than the unvulcanized composites. After the immersion period in water, tensile properties of unvulcanized composites were almost unaffected while vulcanized composites exhibit an increase in the tensile properties. None of the composites reached the equilibrium state within the immersion period. The results of this preliminary study suggest the importance of in-depth study of water absorption–tensile property correlation of this ternary system over a large span of time till the equilibrium state is reached. It is further revealed that the water absorption behavior depends on the characteristics of the test specimen used.     

Effect of a silane coupling agent on the properties of white rice husk ash–polypropylene/natural rubber composites

White rice husk ash (WRHA)–polypropylene (PP)/natural rubber (NR) composites were prepared using a Brabender Plasticorder at 180 °C and a rotor speed of 50 rev min^?1. The mechanical and water‐absorption properties were studied. The incorporation of WRHA into the PP/NR matrix has resulted in the improvement of the tensile modulus; however, the tensile strength, elongation at break and stress at yield decreased with increasing WRHA loading. Poor filler matrix interactions are believed to be responsible for the decrease in the properties. Incorporation of a silane coupling agent, 3‐aminopropyl triethoxysilane (3‐APE), improved tensile modulus, tensile strength and stress at yield of the composites. Water‐absorption studies indicate that the use of the coupling agent reduced the amount of water absorbed by the composites. © 2001 Society of Chemical Industry     

Effects of poly(ethylene‐co‐propylene) elastomer on mechanical properties and combustion behaviour of flame retarded polyethylene/magnesium hydroxide composites

Magnesium hydroxide‐based halogen‐free flame retarded linear low density polyethylene composites containing poly(ethylene‐co‐propylene) elastomer were prepared in the melt process and subsequently vulcanized thermally. Influences of the elastomer on the mechanical properties, combustion characteristics and crystallization behaviour of polyethylene/magnesium hydroxide composites have been investigated. The results from the mechanical tests show that the incorporation of a suitable amount of elastomer into polyethylene/magnesium hydroxide composites after vulcanization can increase both the tensile strength and elongation greatly, compared with those of the composites without the elastomer. It has been found that the properties such as limiting oxygen index, UL‐94 rating, the time to ignition and the rate of heat release of polyethylene/magnesium hydroxide/elastomer composites are all improved in comparison with polyethylene/magnesium hydroxide composites at the same retardant level. Scanning electron microscopy studies show that the incorporation of the elastomer into polyethylene/magnesium hydroxide composites improves the compatibility between the filler and the polymer substrate. The degrees of crystallinity of polyethylene/magnesium hydroxide/elastomer composites decrease with increasing the elastomer content. © 2002 Society of Chemical Industry     

Flow mark defects reduction of injection-molded polypropylene by dynamically vulcanized polyolefin elastomer

Flow mark defects (FMs) worsen surface esthetics and mechanical properties of injection-molded polypropylene (PP). In this work, experiments and dissipative particle dynamic (DPD) simulations were used to investigate the effect of dynamically vulcanized polyolefin elastomer (POE) on FMs of injection-molded PP. Significant FMs reduction was achieved by dynamically vulcanized POE. DPD simulations indicated that POE molecules were randomly distributed in the PP, while dynamic vulcanization led to the formation of elastomeric quasi-clusters, and these quasi-clusters were able to reduce FMs. Both DPD simulations and scanning electron microscopy results showed that more agglomerates with longer and irregular shapes formed with longer vulcanization time and more initiators. The formation of too many agglomerates resulted in different pock surface defects. Dynamically vulcanized POE produced at optimal reaction conditions did not affect the tensile strength, tensile modulus, flexural strength, and flexural modulus, while breaking elongation and notched Izod impact strength of injection-molded PP decreased slightly. This work suggests that the addition of dynamically vulcanized POE may be a promising way to reduce FMs of injection-molded PP.     

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.     

A comparison of white rice husk ash and silica as fillers in ethylene–propylene–diene terpolymer vulcanizates

White rice husk ash (WRHA) and silica filled ethylene–propylene–diene terpolymer (EPDM) vulcanizates were prepared using a laboratory size two‐roll mill. Curing characteristics and physical properties of vulcanizates were studied with respect to the filler loading and filler type. Filler loading was varied from 0–50 parts per hundred resin (phr) at 10 phr intervals. Curing was carried out using a semi‐efficient vulcanization system in a Monsanto rheometer. Enhancement of the curing rate was observed with increasing WRHA loading, whereas the opposite trend was observed for silica‐filled vulcanizates. It was also indicated by the maximum torque and Mooney viscosity results that WRHA offers processing advantages over silica. Compared to the silica‐filled vulcanizates, the effect of filler loading on the physical properties of WRHA‐filled vulcanizates was not significant. According to these observations, WRHA could be used as a diluent filler for EPDM rubber, while silica can be used as a reinforcing filler. © 2001 Society of Chemical Industry     

Effect of dynamic crosslinking on tensile yield behavior of polypropylene/ethylene‐propylene‐diene rubber blends

Tensile yield behavior of the blends of polypropylene (PP) with ethylene‐propylene‐diene rubber (EPDM) is studied in blend composition range 0–40 wt % EPDM rubber. These blends were prepared in a laboratory internal mixer by simultaneous blending and dynamic vulcanization. Vulcanization was performed with dimethylol phenolic resin. For comparison, unvulcanized PP/EPDM blends were also prepared. In comparison to the unvulcanized blends, dynamically vulcanized blends showed higher yield stress and modulus. The increase of interfacial adhesion caused by production of three‐dimensional network is considered to be the most important factor in the improvement. It permits the interaction of the stress concentrate zone developed at the rubber particles and causes shear yielding of the PP matrix. Systematic changes with varying blend composition were found in stress‐strain behavior in the yield region, viz., in yield stress, yield strain, width of yield peak, and work of yield. Analysis of yield stress data on the basis of the various expressions of first power and two‐thirds power laws of blend compositions dependence and the porosity model led to consistent results from all expression about the variation of stress concentration effect in both unvulcanized and vulcanized blend systems. Shapes and sizes of dispersed rubber phase (EPDM) domains at various blend compositions were studied by scanning electron microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2104–2121, 2000     

EPDM rubber reinforced with titania generated by nonhydrolytic sol‐gel process

EPDM rubber was reinforced with titania in situ generated by using a nonhydrolytic sol‐gel (NHSG) process starting from TiCl₄ as titania precursor and tert‐butanol as oxygen donor. Titania particles in anatase form and with average diameter of 6 nm were synthesized via NHSG route and then the same procedure was adopted in presence of EPDM rubber to obtain composites containing up to 30 wt% of filler. Extraction and equilibrium swelling tests suggested an interfering effect of the NHSG reaction on the vulcanization process of the rubber resulting to a crosslink density which decreased in the presence of titania. Quasi‐static and dynamic‐mechanical characterizations indicated that the presence of titania as rigid filler in both the unvulcanized and vulcanized EPDM matrix led to a significant increase in stiffness and stress at break. The experimental values of modulus were systematically higher than the values predicted by classical equations suggesting an additional stiffening contribution deriving from the molecular interaction between the rubber and the filler. POLYM. ENG. SCI., 54:2544–2552, 2014. © 2013 Society of Plastics Engineers     

The comparison of properties of (rubber tree seed shell flour)‐filled polypropylene and high‐density polyethylene composites

The effect of varied rubber tree seed shell flour (RSSF) filler loadings on processing torque, mechanical, thermal, water absorption, and morphological properties of polypropylene (PP) and high‐density polyethylene (HDPE) composites has been studied. The addition of RSSF in the composites increased the stabilization torque in both PP‐ and HDPE‐based composites. Tensile strength, elongation at break, flexural strength, and impact strength show significant reduction when higher loading of RSSF was incorporated, while tensile modulus and flexural modulus were improved. The phenomenon was noted for both matrices, PP and HDPE, but HDPE‐based composites showed clear effects on the reduction of the mechanical properties compared with RSSF‐filled PP. Scanning electron microscopy of tensile fracture specimens revealed the degree of dispersion of RSSF filler in the matrices. At higher filler loadings, agglomerations and poor dispersion of RSSF particles were spotted, which induce the debonding mechanism of the system. Thermogravimetric analysis thermograms showed that both PP‐ and HDPE‐based composite systems with higher RSSF content have higher thermal stability, initial degradation temperature, degradation temperature, and total weight loss. Water absorption ability of the composites increases as the filler loading increases for both matrices. J. VINYL ADDIT. TECHNOL., 22:91–99, 2016. © 2014 Society of Plastics Engineers     

Effects of palm ash loading and maleated natural rubber as a coupling agent on the properties of palm‐ash‐filled natural rubber composites

Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory‐size two‐roll mill (160 × 320 mm²) maintained at 70 ± 5°C in accordance with the method described by ASTM D 3184–89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber–filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber–filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm‐ash‐filled natural rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Design and analysis of single-factor experiments: Analysis of variance of the effect of rice husk ash and commercial fillers in NR compounds

Summary White rice husk ash (WRHA) and black rice husk ash (BRHA) were incorporated into natural rubber (NR) using a laboratory-sized two-roll mill. A conventional vulcanization system was used for curing and physical tests of the NR vulcanized involved determining of tensile and tear resistances. For comparison purposes, precipitated silica (Zeosil-175) and carbon black (N774) were used too. Using the analysis of variance of single-factor experiments, it can be concluded that: BRHA is non-reinforcing filler and its use is limited to 20 phr; WRHA is semi-reinforcing filler and the variation of filler loading (0 up to 50 phr) causes the maximum variation upon tensile strength of NR compounds; and, that although carbon black and silica are reinforcing fillers, a real reinforcement is reached up to 20 phr for tensile strength.     

Jatropha deoiled cake filler‐reinforced medium‐density polyethylene biocomposites: Effect of filler loading and coupling agent on the mechanical,dynamic mechanical and morphological properties

This work focuses on the performance of Jatropha deoiled cake (JOC) as filler for medium‐density polyethylene. The biocomposites were prepared using a melt‐compounding technique. Maleated polyethylene (MPE) was used as a reactive additive to promote polymer/filler interfacial adhesion. The mechanical, thermodynamic mechanical and morphological properties of the resultant composites were investigated. The results show that the incorporation of JOC into the matrix reduced tensile, flexural, and impact strengths compared with the pure matrix. Moreover, tensile and flexural moduli were increased. The composites prepared with MPE had better mechanical properties and lower water uptake, indicating an enhancement in the interfacial interaction between JOC and polyethylene systems. The storage modulus was increased by the increase in filler loading and decreased when MPE was used. The composites loss modulus curves revealed two glass transitions indicating partial miscible blends. Scanning electron microscopy analysis for maleated composites showed a relatively homogeneous morphology with few left cavities, and the filler particle size is smaller compared to nontreated composites. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

EPDM/iPB共混型热塑弹性体的制备与性能

通过对比不同共混比的EPDM/iPB共混体系动态硫化与未硫化的力学性能研究发现,动态硫化后的EPDM/iPB体系的性能明显优于未硫化的,当EPDM/iPB的配比为60/40、动态硫化的时间为6min时,综合性能较好;同时,研究了硫化剂和硫化时间等因素对EPDM/iPB力学性能的影响,结果表明:采用DCP/S作为硫化剂、...     

动态硫化EVA/BR热塑性弹性体的增强研究

采用动态硫化法制备了乙烯-醋酸乙烯共聚物(EVA)/顺丁橡胶(BR)共混型热塑性弹性体(TPE),通过在树脂相中添加HDPE的方式对复合体系进行增强,对其力学性能及断面微观结构进行了研究。结果表明,对于动态硫化EVA/BR共混型TPE,当HDPE填充量在0～30phr的范围内,其动态硫化产物均表现出TPE的特征;随着树脂相中HDPE用量的提高,复合体系的拉伸强度、撕裂强度、邵氏硬度趋于显著提高,断裂伸长率趋于缓慢增加,而扯断永久形变则始终低于25%;FE-SEM的观察表明,动态硫化TPE的拉伸断面上两相界面结合良好;刻蚀样品表面的硫化胶粒子的尺寸在5mm左右且均匀分散。     

Dynamically vulcanized nitrile rubber/polypropylene thermoplastic elastomers

A new compatibilized method was used to prepare thermoplastic elastomer (TPE) of nitrile rubber (NBR) and polypropylene (PP) with excellent mechanical properties by dynamic vulcanization. Glycidyl methacrylate (GMA) grafted PP/amino‐compound was used as a compatibilizer. The effects of the curing systems, compatibilizer, PP type, and reprocessing on the mechanical properties of NBR/PP thermoplastic elastomers were investigated in detail. Experimental results showed that the addition of amino‐compound in the compatibilzer can significantly increase the mechanical properties of the NBR/PP thermoplastic elastomer. Compared with other amino‐compounds, diethylenetriamine (DETA) has the best effect. PP with higher molecular weight is more suitable for preparing NBR/PP thermoplastic elastomer with high tensile strength and high elongation at break. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2862–2866, 2002     

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.     

Poly(ethylene‐co‐vinyl acetate)/calcium phosphate nanocomposites: Thermo mechanical and gas permeability measurements

Poly(ethylene‐co‐vinyl acetate) (EVA)/Calcium phosphate nanocomposites were prepared by melt mixing in a Brabender plasticoder. Nanoparticles of calcium phosphate were synthesized by the polymer‐mediated synthesis and characterized by X‐ray diffractometry and transmission electron microscopy. Mechanical properties such as tensile strength, tensile modulus, tear strength, etc., were measured with respect to the filler loading. Thermal stability of the composites under nitrogen atmosphere was also measured. The composites showed better thermal stability due to the nanoreinforcement. Oxygen gas permeability of the composites showed considerable decrease due to tortuous path created by the nanofillers. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers