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.     

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.     

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.     

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.     

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.     

Aspects of miscibility in poly(vinyl chloride)/epoxidized natural rubber blends. Part I: Mechanical and morphological properties

Miscibility in poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was studied by examining evidence from tensile, impact, and physical properties. The observation of synergism in tensile strength, percent elongation at break, hardness, and relative density has reaffirmed PVC/ENR blends as miscible systems. Studies of impact properties, however, revealed that the blends are microheterogeneous in nature. This could be attributed to the large sizes of polymer molecules involved and the microgel content of ENR-50. Results from Fourier transform infrared spectroscopy (FTIR) revealed that hydrogen bonding is extensively involved in PVC/ENR systems. This evidence unveiled the exact nature of the specific interactions responsible for miscibility and hence the enhanced mechanical properties of PVC/ENR blends.     

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.     

Cure efficiency of dodecyl succinic anhydride as a cross‐linking agent for elastomer blends based on epoxidized natural rubber

Blends of a highly epoxidized natural rubber (ENR50) with unmodified natural rubber (NR) and ethylene propylene elastomers (EPDM) were produced to evaluate the mixing and curing characteristics. Dodecyl succinic anhydride was used to cross‐link the ENR50 component and the reactivity was assessed by monitoring the evolution of the torque in an oscillatory co‐axial cylinder rheometer, as well as by DSC thermal analysis. A physical model was used to obtain a single parameter for the reactivity of the system, which corresponds to the rate constant for first order curing reactions. Although the blends were thermodynamically immiscible, displaying no significant change in T_g, the components were well dispersed at microscopic level. Better mechanical properties were obtained for blends with EPDM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41448.     

炭黑并用对NR／ENR共混胶力学性能及减震性能的影响

对比N660研究了N330／N660、N660／N990炭黑填充体系对天然橡胶（NR）／环氧化天然橡胶（ENR）共混胶力学性能、压缩疲劳生热性能及减震性能的影响,并采用橡胶加工分析仪（RPA）对其加工性能进行了分析。结果表明：N660／N330和N660／N990两种填充体系硫化胶的力学性能,基本上是单用一种炭黑所得硫化胶力学性能的加权平均;不同粒径炭黑并用均能使共混胶的贮能模量E′下降,并且有利于拓宽NR／ENR减震材料的减震范围;不同粒径炭黑并用有利于改善NR／ENR共混胶料的加工性能。     

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     

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.     

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.     

Effect of electron‐beam irradiation on poly(vinyl chloride)/epoxidized natural rubber blend: dynamic mechanical analysis

The irradiation‐induced crosslinking in 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend was investigated by means of dynamic mechanical analysis. The influence of trimethylolpropane triacrylate on the irradiation‐induced crosslinking of PVC/ENR blends was also studied. The enhancement in storage modulus and T_g with irradiation dose indicated the formation of irradiation‐induced crosslinks. This is further supported by the decrease in tan δ_max and loss modulus peak. The compatibility of the blend was found to be improved upon irradiation. The Fox model was used to provide a further insight into the irradiation‐induced compatibility in the blend. Scanning electron microscopy studies on the cryofracture surface morphology of the blends as well as the homopolymer have been undertaken in order to gain more evidence on the irradiation‐induced crosslinking. © 2001 Society of Chemical Industry     

The effect of peroxide crosslinking on thermal,mechanical, and rheological properties of polycaprolactone/epoxidized natural rubber blends

Polycaprolactone (PCL)/epoxidized natural rubber (ENR) blends (PCL/ENR = 70/30, 50/50 wt/wt) were prepared by a melt mixing in an internal mixer in the presence of a small amount (0.5 and 1 phr) of dicumyl peroxide. The effect of peroxide crosslinking on thermal, mechanical, and rheological properties of the blends was investigated by means of DSC, tensile test, and small amplitude oscillating rheometer, respectively. It was revealed that peroxide crosslinking enhanced degree of crystallinity of PCL phase and its non-isothermal melt crystallization temperature. The crosslinked blends behave like a thermoplastic elastomer exhibiting high elongation-at-break and fairly good elastic recovery as well as melt processibility. From melt rheological analysis, the peroxide crosslinked blends showed more pronounced shear thinning effect and higher elasticity compared to simple blends.     

TENSILE PROPERTY OF EPOXIDIZED NATURAL RUBBER/NATURAL RUBBER BLENDS

The tensile strength and elongation at break of epoxidized natural rubber (ENR) blended with natural rubber (NR) was studied. ENR 25, ENR 50, and one grade of natural rubber (SMR L) were used as the elastomers. The composition of ENR was varied from 0% to 100% rubber. The accelerated sulfur vulcanization system was used throughout the investigation. The tensile property of unaged and aged samples was determined by using the Monsanto tensometer (T10) operating at 50 cm/min. Results show that the tensile strength and elongation at break passes through a maximum at 50% ENR for both ENR25/SMR L and ENR50/SMR L blends. This positive deviation from ideality is attributed to the mutual reinforcement of ENR and NR in the blends as a result of strain-induced crystallization. This synergistic effect is more pronounced in the case of ENR 25 due to the higher crystallinity and availability of more double bonds, which is more compatible to NR compared to ENR 50/NR blends. For the aged samples, a drop in the tensile property associated to the breakdown of the polysulfidic cross-link during aging is observed. A systematic study of the effect of sulfur concentration on the percentage retention of tensile property of the ENR blends after aging reveals that percentage retention decreases with increasing sulfur loading, which, in turn, enhances the formation of the polysulfidic cross-link; thus, more breakdown is observed in the rubber vulcanizate.     

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.     

Thermoplastic elastomers-based natural rubber and thermoplastic polyurethane blends

Thermoplastic elastomers based on the blends of thermoplastic polyurethane (TPU) and natural rubber were prepared by a simple blend technique. The influence of the two different types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends was investigated. The main aim of this study was to improve heat resistance and damping properties, and also to prepare the TPU material with low hardness by blending with various amounts of natural rubber. It was found that the TPU/ENR blends exhibited superior modulus, hardness, shear viscosity, stress relaxation behavior and heat-resistant properties compared to the blends with TPU and unmodified NR. This was attributed to higher chemical interaction between the polar functional groups of ENR and TPU by improving the interfacial adhesion. It was also found that the ENR/TPU blends exhibited finer grain morphology than the blends with unmodified NR. Furthermore, lower tension set, damping factor (Tan ??) and hardness, but higher degradation temperature, were observed in natural rubber/TPU blends compared to pure TPU. This proves the formation of TPU material with high heat resistance, low hardness and better damping properties. However, the blends with higher proportion of natural rubber exhibited lower tensile strength and elongation at break.     

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     

Interaction Between Fumed-Silica and Epoxidized Natural Rubber

Epoxidized natural rubber (ENR)/fumed silica vulcanizates were prepared by mechanical mixing method. Fumed silica content can affect mechanical properties of the composites, and ten parts per hundreds of rubber (phr) fumed silica lead to the best tensile strength. The interaction between ENR and fumed silica was characterized by Kraus equation, crosslink density (tested by NMR), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and scanning electron microscope (SEM). The results showed that the dispersion of silica in ENR was better than in natural rubber (NR), hydrogen bond was produced between ENR and fumed-silica in ENR/silica blends, and glass transition temperature of ENR/silica vulcanizate was higher than pure ENR vulcanizate. TGA and DMA confirmed that there was intense interaction between ENR and silica.     

Effect of carbon black on self‐crosslinking network structure of polychloroprene rubber and epoxidized natural rubber blends

The goal of this research is to improve poor network structure of polychloroprene rubber (CR)/epoxidized natural rubber (ENR) self‐crosslinking blends, which could substitute traditional vulcanizates in some application area. Carbon black (CB)–CR/ENR blends were prepared by reacting CR with ENR in the presence of CB. The structure of CR/ENR blends was characterized by attenuated total‐reflectance Fourier transform infrared spectroscopy (FTIR‐ATR). The effect of CB loading on curing characterization and mechanical properties of CR/ENR blends was investigated, and the interaction among CR, ENR, and CB was studied using differential scanning calorimetry. The effect of CB loading on the Payne effect of CR/ENR was investigated using rubber process analyzer. Scanning electron microscope was used to characterize the morphology of CB–CR/ENR blends. The results showed that CR/ENR blends were obtained by the ring‐opening reaction of epoxy groups in ENR and chlorine groups in CR. Mechanical properties of CR/ENR blends increased with the increase of CB loading. The Payne effect of CR/ENR became more remarkable with increasing CB loading. Morphology study indicated that interfacial compatibility between CR and ENR increased with the increase of CB loading because CB could strengthen the self‐crosslinking network structure of CR/ENR blends. The promoting effect of CB on self‐crosslinking reaction was verified by the assessment of crosslink density. POLYM. COMPOS., 38:463–471, 2017. © 2015 Society of Plastics Engineers