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.     

Modification of PVC/ENR blends by electron beam irradiation

The effects of electron irradiation, with doses ranging from 20 to 100 kGy on the physical properties of poly(vinyl chloride)/epoxidised natural rubber blends (PVC/ENR50 blends) were investigated. The enhancement in tensile strength, elongation at break, hardness, and aging properties of the blends have confirmed the positive effect of irradiation on the blends. Crosslinking of the ENR50 phase proved to play a major role in the improvement of mechanical properties of blends. The results also revealed that at any blend composition the enhancement in properties depends on the irradiation dose which controls the degree of radiation-induced crosslinking. The single glass transition temperature obtained confirms that the blends remain miscible upon irradiation.     

Thermal and mechanical properties of electron beam irradiated poly(vinyl chloride)/polystyrene blends

The effect of electron beam irradiation on the thermal and mechanical properties of poly(vinyl chloride)/polystyrene (PVC/PS) blends and PVC/PS blends containing epoxidized natural rubber (ENR) was studied. The thermogravimetric analysis study showed that the thermal decomposition of the plasticized PVC individual polymer goes through two stages, whereas PS decomposes through one stage. However, the temperature of the maximum rate of reaction (T_max) of PS is much higher than that for PVC and their blends. Meanwhile, the T_max was found to increase with increasing PS ratios in the blend. The thermal stability of PVC/PS blends was greatly increased after electron beam irradiation in comparison with unirradiated blends. Moreover, the addition of ENR to PVC/PS increased the thermal stability. On the other hand, the mechanical properties in terms of tensile strength and elongation at break of PVC/PS blends are lower than pure PVC polymer because of the immiscibility. However, the addition of ENR to the PVC/PS (80/20) blend increased the elongation at break from 114 to 321% associated with a small effect on the tensile properties. These behaviors were supported by structure morphology studies observations, which indicate an improvement in the interfacial adhesion between the phases. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Determination of optimum blending conditions for poly(vinyl chloride)/epoxidized natural rubber blends

An attempt to resolve the difficulties normally faced in preparing PVC-dominant PVC/ENR blends with the Brabender plasticorder is discussed. As expected, it was found that the mechanical properties of PVC/ENR blends are greatly influenced by the mixing parameters, which are further reinforced with evidence from both dynamic mechanical analysis (DMA) and morphological studies. Both techniques showed the attainment of compatible 50/50/PVC/ENR blends, the former a single glass transition temperature (T_g) and the latter a single-phase system, albeit their inherent properties are dependent on the blending parameters. By utilizing the correlation between mixing temperature and rotor speed derived, good PVC/ENR blends can be easily procured. © 1993 John Wiley & Sons, Inc.     

Internal mixer studies of poly(vinyl chloride)/epoxidized natural rubber blends

Blends of polyvinyl chloride/epoxidized natural rubber (PVC/ENR) blends were studied. Their rheological properties were studied with a Brabrender Plasticorder. It was found that the rheological properties of any PVC/ENR blends are governed by their blending conditions. To ensure homogenous PVC/ENR blends, adequate and suitable blending conditions must be utilized. PVC thermoplastics phases enhances rigidity while ENR rubbery phases imparts flexibility and processability to the blends. With premixing, Ba/Cd/Zn-based PVC stabilizer is effective in stabilizing the PVC/ENR blends. Their properties are further enhanced by the addition of curatives.     

Melt elasticity behavior and extrudate characteristics of rigid poly(vinyl chloride)/epoxidized natural rubber miscible blends

A study on the melt elasticity behavior and extrudate characteristics of melts of rigid poly(vinyl chloride), PVC, and rigid poly(vinyl chloride)/epoxidized natural rubber (ENR) miscible blends were conducted. Extrusion studies were carried out in a capillary rheometer and examinations of the surface characteristics of the extrudate were made by taking photomicrographs in a scanning electron microscope. The anomalous behavior in the die swell ratio of rigid PVC arising from the particle agglomerates continued in its blends up to 50 wt% composition of ENR. Temperature independence for high ENR blends was noted for the principal normal stress difference and elastic shear modulus, when shear stress was held constant. Recoverable shear strain and die swell ratio behaved identically in terms of blend composition and processing temperature. Factors which control the extrudate distortion and melt fracture of the melts of rigid PVC/ENR systems were fusion of particle agglomerates and strength of melts. Diamond cavitations were typical of the extrudate surface of PVC melts as those of the fracture surface of the tensile failure of PVC. Conditions to obtain a smooth extrudate surface of rigid PVC melts in blends with ENR have been found to be the low ENR content, low shear rate, or stress and high processing temperature.     

Enhancement of PVC/ENR blend properties by poly(methyl acrylate) grafted oil palm empty fruit bunch fiber

Effect of oil palm empty fruit bunch (OPEFB) fiber and poly(methyl acrylate) grafted OPEFB on several mechanical properties of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends were studied. The composites were prepared by mixing the fiber and the PVC/ENR blends using HAKEE Rheomixer at the rotor speed of 50 rpm, mixing temperature 150°C, and mixing period of 20 min. The fiber loadings were varied from 0 to 30% and the effect of fiber content in the composites on their ultimate tensile strength (UTS), Young's modulus, elongation at break, flexural modulus, hardness, and impact strength were determined. An increasing trend was observed in the Young's modulus, flexural modulus, and hardness with the addition of grafted and ungrafted fiber to the PVC/ENR blends. However the impact strength, UTS, and elongation at break of the composites were found to decrease with the increase in fiber loading. An increase in elongation at break and UTS and decrease in the flexural and Young's modulus was observed with the addition of PMA‐g‐OPEFB fiber compared to ungrafted fiber. This observation indicates that grafting of PMA onto OPEFB impart some flexibility to the blend. The morphology of cryogenically fractured and tensile fracture surfaces of the composites, examined by a scanning electron microscope shows that the adhesion between the fiber and the matrix is improved upon grafting of the OPEFB fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Aspects of miscibility in poly(vinyl chloride)/epoxidized natural rubber blends. Part II: Dynamic mechanical properties

Miscibility in poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was further investigated by means of dynamic mechanical analysis. The single glass transition temperature shown by the blends supported earlier observations of miscibility Furthermore, observed synergism in storage modulus has again reaffirmed the miscibility of these blends. A critical examination of the damping peaks at various compositions again revealed the microheterogeneous nature of the blends. Some theories relating glass transition temperature and modulus with miscibility were also used to examine miscibility. Agreement of the results with theories proposed by Gordon—Taylor and Kleiner has provided a further insight into the miscible nature of PVC/ENR blends.     

亚乙基硫脲对PVC和PVC/ENR共混物的交联作用

从交联速率、压缩永久变形、凝胶质量分数、强伸性能和耐热性能等方面考察了亚乙基硫脲（ＥＴＵ）和ＥＴＵ／硫黄对ＰＶＣ及其与环氧化天然橡胶（ＥＮＲ）共混物的交联作用。结果表明,ＥＴＵ和ＥＴＵ／硫黄对ＰＶＣ及其与ＥＮＲ的共混物有明显的交联作用;交联后共混物的物理性能和耐热性能均有较大提高;适当增大ＥＮＲ用量,有利于提高共混物的热变形性能;ＰＶＣ／ＥＮＲ的共混比为７０／３０时,硫黄的最佳用量为１５份,促进剂选择促进剂ＤＭ／ＴＭＴＤ体系为佳。     

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.     

Rheological properties of poly(vinyl chloride) / epoxidized natural rubber blends. Part II: The effect of processing variables

The effect of processing variables on the rheological properties of PVC/ENR blends was investigated. The role of crosslinking in determining the flow behavior of blends was also examined by means of dynamically cured blends. It was found that PVC/ENR blends yield melts that are power law fluids. The flow of the melts improves with an increase in temperature and shear rate. However, the introduction of crosslinks reverses this trend, although under more rigorous conditions, the influence of crosslinks is superseded, and subsequently, flow becomes shear rate and temperature dependent. PVC/ENR systems also manifested elastic phenomena. The dependence of the elastic phenomena such as die swell and melt fracture on L/D ratio of the die was demonstrated.     

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     

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.     

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。     

Preparation and Electron Beam Irradiation of PVC/ENR/CNTs Nanocomposites

Poly (vinyl chloride), PVC/epoxidized natural rubber blend, ENR/carbon nanotubes, CNTs nanocomposites were prepared using melt intercalation and solution blending methods. In both preparation methods PVC: ENR: CNTs ratios were fixed at 50:50:2, while the 50/50 PVC/ENR blend without the addition of CNTs was used as control. The PVC/ENR/CNTs nanocomposites were exposed to electron beam (EB) irradiation at doses ranging from 0–200 kGy. The effects of two different preparation methods on the tensile properties, gel fraction and morphology of the PVC/ENR/CNTs nanocomposites were studied. Prior to EB irradiation, the addition of 2 phr of CNTs caused a drop in the tensile strength (Ts) of the 50/50 PVC/ENR blend, implying poor distribution of CNTs in the PVC/ENR blend matrix. However upon EB irradiation, the nanocomposites prepared by the melt blending method exhibited higher values of Ts as compared to the neat PVC/ENR blend due to occurrence of radiation-induced cross-linking in the PVC/ENR blend matrix. Transmission electron microscopy (TEM) images proved that a better dispersion of CNTs in PVC/ENR blend matrix can be achieved by melt intercalation compared to solution blending and the dispersion of CNTs was improved by irradiation. Scanning electron microscopy (SEM) results showed a distinct failure surface with formation of rough structure for the irradiated nanocomposites, which explains the higher values of tensile properties compared to the non-irradiated nanocomposites.     

不同改性蒙脱土对ENR/PVC共混型TPV填充效果的研究

采用熔融插层法制备了聚氯乙烯/蒙脱土(PVC/MMT)插层产物,再将该产物与环氧化天然橡胶(ENR)在密炼机中进行熔融共混制备ENR/PVC/MMT共混型热塑性弹性体(TPV),研究了不同改性MMT对共混物力学性能、热稳定性以及动态力学性能的影响。结果表明:二甲基双十八烷基铵改性蒙脱土(MMT-2C18)能显著提高ENR/PVC共混型TPV的拉伸强度,无机MMT能显著提高ENR/PVC的断裂伸长率,十八烷基铵改性蒙脱土(MMT-C18)会降低TPV的拉伸强度和断裂伸长率;有机改性MMT会促进TPV中PVC的降解,使得复合材料的热稳定性降低;动态热力学分析显示,MMT可使复合材料的储能模量增加,其中有机改性MMT使材料的损耗因数(tanδ)曲线峰强降低,峰宽变宽。     

High‐performance bio‐based poly(lactic acid)/natural rubber/epoxidized natural rubber blends: effect of epoxidized natural rubber on microstructure,toughness and static and dynamic mechanical properties

Attempts have been made to prepare high‐performance bio‐based blends through blending of poly(lactic acid) (PLA) with natural rubber (NR) in the presence of epoxidized natural rubber (ENR) as a compatibilizer. The prepared samples were characterized using differential scanning calorimetry, measuring the tensile properties and impact resistance, scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMTA). Morphological studies revealed a matrix‐dispersed morphology for all blends, in which the average droplet size significantly decreased with the use of ENR. The elongation at break and impact strength of the blend containing 3 wt% ENR were 45 and 16 times those of neat PLA, respectively. These values are significantly higher than those previously reported for various simple and dynamically vulcanized rubber‐toughened PLAs. The influence of ENR on compatibility was confirmed by rheological tests, FTIR spectra and DMTA. DMTA also showed a marked increase in elastic modulus for the blend in the presence of 3 wt% ENR. The tensile properties and impact resistance were directly dependent on the ENR content and rubber droplet size. © 2018 Society of Chemical Industry     

NR/EPDM 的共硫化

利用环氧化天然橡胶(ENR)与天然橡胶(NR)和三元乙丙橡胶(EPDM)均有很好相容性的特点，采用硫化促进剂预混工艺对NR／EPDM并用胶实施共硫化。考察了其对NR／EPDM并用胶的硫化特性、硫化胶的物理机械性能和耐热空气老化性能的影响。结果表明：本工艺确实能改善NR／EPDM的共硫化性能，所得硫化胶物理性能较好且操作简单。     

Investigation of multiphase polymeric systems of poly(vinyl chloride)/ethylene-propylene-diene-gp-(styrene-CO-acrylonitrile) blends

The graft copolymer, ethylene-propylene-diene rubber (EPDM)-gp-(styrene-co-acrylonitrile) has been synthesized by solution precipitation polymerization using benzoyl perixide as initiator. The graft copolymer has been characterized after separation through soxhlet extraction by IR, NMR, and elemental analysis techniques. The graft copolymer of EPDM is melt blended with PVC. The nature of compatibility of the graft copolymers with PVC has been studied by means of morphological analysis and by thermal analysis. The mechanical properties, Izod impact strength, tensile strength, and flexural modulus of the blends are extensively studied over the wide range of concentrations. The results of both compatibility and mechanical properties are compared with those of PVC/EPDM blends. The nature of compatibility obtained shows that PVC/EPDM blends are incompatible and the PVC/EPDM-gp-SAN system is semicompatible. Also, these results indicate that the PVC/EPDM-gp-SAN system has its highest impact strength at 14 wt% of EPDM/gp-SAN graft copolymer. The fractured surface analysis of the impact fractured samples is also undertaken by an SEM technique. The results of the mechanical properties are discussed in view of existing theories of impact modification, along with the morphological feature of fractographs.