Ultrasonic investigation on compatibility of PVC-modified liquid natural rubber blends

The extent of compatibility of the blend solutions poly(vinyl chloride)–liquid natural blends (PVC–LNR), PVC–expodized LNR-20 (PVC–ELNR-20), and PVC–ELNR-50 has been studied using an ultrasonic technique. The variation of ultrasonic velocity with composition is nonlinear in the case of blends of PVC–LNR and PVC–ELNR-20, showing incompatibility. The ultrasonic velocity versus composition plot for PVC–ELNR-50 showed linear behavior showing compatibility. The above behavior was confirmed by heat of mixing calculations as well as ultrasonic attenuation measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 785–790, 1998     

Blends of PVC and epoxidized liquid natural rubber: Studies on impact modification

Liquid natural rubber of different molecular masses L‐LNR, and H‐LNR were subjected to varying degree of epoxidation (L‐ELNR‐10, L‐ELNR‐20, L‐ELNR‐30, L‐ELNR‐40, L‐ELNR‐50, H‐LNR‐20, and H‐LNR‐50) and the products were incorporated into PVC at various compositions by the solution blending method. These blend systems were subjected to tensile testing, tensile impact measurements, and SEM studies. It was observed that blends with L‐ELNR‐20 showed highest impact strength modification, followed by L‐ELNR‐10 and L‐ELNR‐30. High impact properties showed by these blends are attributed to the optimum level of compatibility existing between the blend components. Tensile impact fracture studies revealed that the failure pattern for this blend system is intermediate between the brittle fracture of rigid PVC and ductile fracture of PVC/L‐ELNR‐50 samples. Blends up to 30 mol % of epoxidation showed partially compatible heterogeneous nature exhibiting domain morphology. Blends of liquid rubber with higher degree of epoxidation showed deterioration in tensile strength, modulus, yield strength, and tensile impact strength due to plasticization of PVC caused by the higher polar interaction between PVC chains and the oxirane rings. Effect of ELNR molecular weight was studied and it is found that the impact modification is higher for the L‐ELNR blends compared to the H‐ELNR blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A study on compatibility of polymer blends of polystyrene/poly(4‐vinylpyridine)

Blends of polystyrene/poly (4‐vinylpyridine) have been prepared by casting from a common solvent. The compatibility of the blends was studied by using dilute solution viscometry (DSV), differential scanning calorimetery (DSC), Fourier transformation‐infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). The relative viscosity versus composition plots for the blends are not perfect linear. The corresponding intrinsic viscosity values show negative deviation from ideal behavior when plotted against composition. Also, the modified Krigbaum and Wall interaction parameter, Δb, shows small and negative values for all compositions except for the blend PS/P4VP (25 : 75). The results indicate that the polymers are incompatible but small interaction values predict physically miscible blends which eventually show phase separation, as is observed in the present studies. However, the blends as obtained show a single, composition‐dependent, glass transition temperature that fits the Fox equation well, indicating the presence of homogeneous phase. The constant, k obtained from Gordon‐Taylor equation suggests intermolecular attraction between these polymers. FT‐IR and SEM support the results of DSV and DSC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological properties of poly(vinyl chloride)/epoxidized natural rubber blends. Part I: Composition dependence and the effect of compounding conditions

Epoxidized natural rubber is a recently commercialized modified form of natural rubber. This paper is part of our continuing effort to study the responses of this new material to melt mixing and other shaping processes. The Shimadzu capillary rheometer was used to evaluate the composition dependence of miscibility of polyvinyl chloride/epoxidized natural rubber blends (PVC/ENR blends). The rheometer was also used to evaluate the effect of compounding parameters on the rheological properties of the blends. The results confirmed PVC/ENR blends as miscible systems that show a synergism in apparent shear viscosity highlighted by the positive deviation from the logarithmic additivity rule. These results based on capillary rheometry are also in very good agreement with our earlier attempt to predict optimum mixing from torque rheometry by using the Brabender Plastogram as an indicator.     

Melt flow behavior of blends from poly(vinyl chloride) and epoxidized natural rubber

Blends from poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) were prepared in a Brabender plasticorder by the melt blending technique. The melt flow behavior of these blends with respect to blend ratio and temperature has been examined using a melt flow indexer and capillary rheometer. ENR decreases the Brabender torque, increases the melt flow index (MFI), and decreases the melt viscosity of PVC in the blends. Arrhenius plots were used to study the effect of temperature on melt flow index (MFI) and viscosity. Moreover, the flow behavior index (n′) obtained from capillary rheometer data was found to be dependent on temperature and blend ratio.     

Miscible blends from plasticized poly(vinyl chloride) and epoxidized natural rubber

Miscible blends from plasticized poly(vinyl chloride), and epoxidized natural rubber having 50 mol% epoxidation level were prepared in a Brabender Plasticorder by the melt-mixing technique. Changes in Brabender torque and temperature, density, dynamic mechanical properties, and differential scanning calorimetry of the samples were examined as a function of blend composition. The plasticized poly(vinyl chloride)/epoxidized natural rubber blends behaved as a compatible system at all composition ranges as evident from their single glass-rubber transition temperature (T_g) obtained from dynamic mechanical analysis as well as from differential scanning calorimetry. Profound changes in the nature of the glass-rubber transition were noted with respect to blend composition. The T_g-width values of blends lie between those of plasticized poly(vinyl chloride) and epoxidized natural rubber.     

全硫化超细粉末橡胶对PVC-U力学性能及形态的影响

研究了未增塑聚氯乙烯／粉末橡胶共混物的力学性能和形态特征。研究发现，随粉末橡胶用量增大，共混物的冲击强度先有所降低然后逐渐上升。实验结果和电镜图像表明：粉末橡胶基本粒子均匀分散的效果是影响共混物冲击韧性高低的重要因素；环氧化天然橡胶有促进粉末橡胶分散、改进增韧效果的作用。基本断裂功方法的研究结果表明，共混物的比基本断裂功随粉末橡胶用量增多而降低，比非基本断裂功则随之而升高，且断裂功的变化主要表现在材料屈服之前。     

The Effect of Epoxidized Sunflower Oil on the Miscibility of Plasticized PVC/NBR Blends

Blends of plasticized poly(vinyl chloride) (PVC) with several ratios of nitrile rubber (NBR) were studied. The effects of epoxidized sunflower oil (ESO) in combination with di-(2-ethylhexyl)phthalate (DEHP) in the PVC blends on the tensile strength, elongation, hardness, and dynamical mechanical analysis (DMA) were studied. The modulus and hardness results revealed that the addition of ESO to the blend favors the miscibility of PVC and NBR. The PVC/NBR/(DEHP-ESO) blends behave as a compatible system as is evident from the single T _g observed in DMA. The moderate level broadening of the T _g zone in blends is due to the presence of ESO in the plasticizer system. Blends of plasticized PVC and nitrile rubber showed promising properties. The ESO is suitable to partially replace DEHP in PVC/NBR blends.     

Improvement of the compatibility of natural rubber/ethylene–propylene diene monomer rubber blends via natural rubber epoxidation

The longitudinal ultrasonic velocity, longitudinal ultrasonic absorption (attenuation coefficient), glass‐transition temperature, and Mooney viscosity for epoxidized natural rubber/ethylene–propylene diene monomer blends were measured. The variation of the longitudinal ultrasonic velocity with the blend ratios was linear, indicating a compatible system in comparison with the same system without epoxidation (natural rubber/ethylene–propylene diene monomer), which was incompatible. Also, the behavior was confirmed by heat of mixing calculations as well as Mooney viscosity measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2816–2819, 2002     

Natural rubber–HDPE blends with liquid natural rubber as a compatibilizer. I. Thermal and mechanical properties

The measurement of physical properties of thermoplastic natural rubber (TPNR) of NR–HDPE blends have been made at various compositions of high-density polyethylene (HDPE). The tensile properties and hardness of TPNR improve significantly with the addition of liquid natural rubber (LNR) to the blend. The degree of cross-linking also increases with increasing amount of LNR added. The LNR with molecular weight (M_w) of 50,000 and reactive terminals promotes cross-linking within the rubber phase and grafting of the polyethylene chains onto the rubber matrix system. The maximum stress and strain of the blends measured are about 7.5 MPa and 1000%, respectively. Dynamic mechanical analysis results indicate a single T_g on a tan δ trace at about ?50 and ?55°C for the two types of blends, respectively. © 1994 John Wiley & Sons, Inc.     

Adhesion properties of pressure-sensitive adhesives prepared from SMR 10/ENR 25, SMR 10/ENR 50, and ENR 25/ENR 50 blends

The adhesion properties, i.e. viscosity, tack, and peel strength of pressure-sensitive adhesives prepared from natural rubber/epoxidized natural rubber blends were investigated using coumarone-indene resin and toluene as the tackifier and solvent respectively. One grade of natural rubber (SMR 10) and two grades of epoxidized natural rubbers (ENR 25 and ENR 50) were used to prepare the rubber blends with blend ratio ranging from 0 to 100%. Coumarone-indene resin content was fixed at 40 parts per hundred parts of rubber (phr) in the adhesive formulation. The viscosity of adhesive was measured by a HAAKE Rotary Viscometer whereas loop tack and peel strength was determined using a Lloyd Adhesion Tester operating at 30 cm/min. Results show that the viscosity of the adhesive passes through a minimum value at 20% blend ratio. For loop tack and peel strength, it indicates a maximum at 60% blend ratio for SMR 10/ENR 25 and SMR 10/ENR 50 systems. However, for ENR 25/ENR 50 blend, maximum value is observed at 80% blend ratio. SMR 10/ENR 25 blend consistently exhibits the best adhesion property in this study, an observation which is attributed to the optimum compatibility between rubbers and wettability of adhesive on the substrate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of EPDM on the mechanical properties of blends of high and low density polyethylene

Summary We studied the effect of adding ethylene-propylene-diene rubber (EPDM) to blends of high (HDPE) and low (LDPE) density polyethylene. The extrusion torque of the blend without EPDM shows a deviation from the linear addition rule, but blends with rubber follow the addition rule. Two composition regions that are compatible with the torque behavior are present in the Young's modulus and extension at break curves. The EPDM content improves the extension at break of LDPE rich blends. This improvement extends to higher compositions of HDPE as the EPDM content is increased. Received: 4 September 1997/Revised version: 30 April 1998/Accepted: 13 May 1998     

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.     

Effect of matrix composition on the fracture behavior of rubber-modified PMMA/PVC blends

Summary PB-g-MMA core-shell impact modifiers were synthesized by seed emulsion polymerization and impact-modified PMMA/PVC blends were prepared by melt blending PMMA, PVC and PB-g-MMA at 160 °C. The PB-g-MMA particles were dispersed uniformly in the PMMA/PVC matrix. PMMA/PVC blends were prepared in the blend ratio from 100/0 to 0/100 and the rubber content was kept 16% in all the compositions. The effects of matrix composition on the mechanical properties and morphology of the blends were studied. It was found that when the matrix was a PMMA-rich system, the sample broke in a brittle mode and crazing of the matrix was the main mechanisms of deformation. When the matrix was a PVC-rich system, the sample broke in a ductile mode and the main deformation mechanisms were cavitation of the particle and shear yielding of the matrix. There existed a transition from crazing to shear yielding in the rubber-modified PMMA/PVC blend as the matrix composition varied.     

Changes in morphology and properties of NR–NBR blends. Effect of viscosity ratio modified by liquid natural rubber and epoxidised liquid natural rubber

Abstract

Changes in rheological properties, morphology, and oil resistance in NR–NBR blends by viscosity ratio have been investigated. In this study, the viscosity ratio was modified by mechanical mastication and addition of liquid natural rubber (LNR) and epoxidised liquid natural rubber (ELNR). The results reveal that as viscosity ratio increased from 0·5 to 1·0, Mooney viscosity of the blends increased, and then decreased sharply as the viscosity ratio further increased from 1·0 to 2·0. The addition of LNR and ELNR for plasticising NR and NBR, respectively, does not significantly affect cure properties of the blends. The phase size of the NR dispersed phase depends strongly on the viscosity ratio. The high viscosity of the matrix and/or the low viscosity of the dispersed phase promote breaking up of the dispersed phase. Unexpectedly, a decrease in size of the dispersed phase by the modification of viscosity ratio via the use of low molecular weight rubber (i.e. LNR and ELNR) did not result in an improvement in oil resistance.     

Mechanical Properties and Thermooxidative Aging of a Ternary Blend,Pvc/Enr/Nbr,Compared with the Binary Blends of Pvc

In the quest to improve the thermooxidative aging of the poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, nitrile rubber (NBR) was incorporated into the blend to yield a ternary blend of PVC/ENR/NBR. A Brabender Plasticorder with a mixing attachment was used to perform the melt mixing at 150°C and 50 rpm followed by compression molding. The mechanical properties, dynamic mechanical properties, and thermooxidative aging behavior of the ternary blend were compared with those of the binary blends (i.e., PVC/ENR and PVC/NBR). It was found that the ternary blend exhibits mechanical properties which are superior to those of PVC/ENR. A single glass transition temperature (T _g) obtained from dynamic mechanical analysis coupled with synergism in the modulus and some other mechanical properties indicate that PVC, ENR, and NBR form a single phase (miscible system) in the ternary blend. Di-2-ethyl hexylphthalate (DOP) plasti-cizer improves the aging resistance of the blends generally, whereas the presence of CaCO₃ as a filler only imparts minor influences on the properties and aging resistance of the blends.     

Contact angle behaviour of poly(vinyl chloride)/ epoxidized natural rubber miscible blends

—Contact angle studies of miscible poly(vinyl chloride)/epoxidized natural rubber (PVC/ ENR) blends were carried out in air using water and methylene iodide. The solid surface free energy was calculated from harmonic mean equations. Blending of PVC and ENR decreased their contact angle or increased their solid surface free energy due to the improved chain mobility, and the accumulation of excess polar sites at the surface through conformational alterations resulting from the specific interaction of PVC and ENR. The work of adhesion, interfacial free energy, spreading coefficient, and Girifalco-Good's interaction parameter changed markedly with the blend composition. In blends, PVC and ENR improved hydrophilicity, and wettability with polar and non-polar liquids. The presence of a plasticizer in PVC, in general, further improved the wettability and hydrophilicity in blends.     

Mechanical and thermo-oxidative properties of blends of poly(vinyl chloride) with epoxidized natural rubber and acrylonitrile butadiene rubber in the presence of an antioxidant and a base

Being polar and compatible with poly(vinyl chloride), epoxidized natural rubber (ENR) is similar in behaviour to acrylonitrile butadiene rubber (NBR). To assess the extent of this similarity, the mechanical properties of 50/50 blends of PVC with these two rubbers were compared. Their response to thermo-oxidative ageing in the presence of an antioxidant and a base was also investigated by ageing the blends at 100°C for 7 days. Studies involving mechanical properties and FTIR were used to evaluate the extent of thermal degradation. The results revealed that blends of ENR show mechanical properties which are as good as, and in some instances better than, those of the NBR blends. However, the ENR blends with PVC are very prone to oxidative ageing. This might be attributed to the susceptibility of the oxirane group to ring-opening reactions, particularly in the presence of PVC, which yields HCl as it degrades. The amine-type antioxidant 2,24-trimethyl-1,2-dihydroquinoline (TMQ) improved the oxidative stability of both blends. This was more significant in the ENR blend, which in some cases attained stability comparable with that of NBR. The addition of a base, calcium stearate [Ca(St)₂], did not show any influence in the PVC/ENR blend, even though it was expected to curb acid-catalysed degradation. Ca(St)₂, however, improved the oxidative stability of the PVC/NBR blend. The combination of optimum amounts of TMQ and Ca(St)₂ effectively improved the tensile strength of both unaged blends, without appreciable adverse effect on elongation at break. This combination also imparted stability better than that of TMQ alone.     

Blending of natural rubber with linear low-density polyethylene

Blends of natural rubber (NR) with linear low-density polyethylene (LLDPE) were prepared by melt blending of the materials in a plasticorder mixer at various temperatures around the melting point of LLDPE and at various mixing rates. The optimum processing conditions were a temperature of about 135°C and a mixing rate of 55 rpm. The tensile properties, stress and strain, of the blend had improved significantly with the addition of liquid natural rubber (LNR) into the blend. For blends with compositions around 50% NR, about 10–15% LNR produced the most significant improvement in the physical properties. Welldispersed plastic particles in a rubber matrix were strongly indicated in these samples. Scanning electron micrographs (SEM) of the samples also indicated an increase in the homogeneity of the mixes with the addition of LNR. A single glass transition temperature of about?55°C for the blend was observed via dynamic mechanical analysis (DMA). Interfacial linking between the NR and LLDPE phases was attributed to the presence of active groups on the polyisoprene chain of LNR, which induced the interphase reaction between the NR and LLDPE phases. © 1995 John Wiley & Sons, Inc.     

Plastification of poly(vinyl chloride) by polymer blending

Blends of poly(vinyl chloride) (PVC) with different copolymers have been studied to obtain a plasticized PVC with improved properties and the absence of plasticizer migration. The copolymers used as plasticizers in the blends were acrylonitrile butadiene rubber, ethylene vinyl acetate (EVA), and ethylene-acrylic copolymer (E-Acry). Blends were studied with regard to their processing, miscibility, and mechanical properties, as a function of blend and copolymer composition. The results obtained were compared with those of equivalent compositions in the PVC/dioctyl phthalate (DOP) system. Better results than PVC/DOP were obtained for PVC/acrylonitrile butadiene rubber blends. The plasticizing effect on PVC of EVA and E-Acry copolymers was similar to that of DOP. It is shown that crosslinking PVC/E-Acry blends or increasing the vinyl acetate content in PVC/EVA blends, are alternatives that can increase the compatibility and mechanical properties of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1303–1312, 2000