Electron‐beam processing of nylon 6 and HNBR blends. Part II: development of high strength,heat‐ and oil‐resistant thermoplastic elastomers

The effects of electron‐beam irradiation on morphology, mechanical properties and on the heat and hot oil resistance of the thermoplastic elastomeric blend of 30:70 and 70:30, nylon 6 and hydrogenated nitrile rubber (HNBR) were investigated over the dose range 0–8 Mrad. The insoluble content of blends increased with increase in the radiation dose. The morphology of the blend was studied in scanning electron microscopy, with special reference to the effect of radiation prior to processing via injection molding. Irradiated pellets showed better mechanical properties after injection molding compared with irradiated sheets at low radiation dose. The observed differences in mechanical properties are explained on the basis of morphology of the blend. The blend properties were also found to have a strong dependence on nylon content. It was found that the blends rich in nylon had superior mechanical properties, hot oil and solvent resistance, whereas blends with higher HNBR content had better set and heat resistance. The effect of radiation on interaction in these blends was also evaluated and was found to induce possible inter‐chain crosslinking in the blends. Copyright © 2006 Society of Chemical Industry     

Electron‐beam irradiation of blends of polypropylene with recycled acrylonitrile‐butadiene rubber

One‐mm thick sheets were prepared from blends of polypropylene and recycled acrylonitrile‐butadiene rubber (rNBR) with different blend ratios. Trimethylolpropane triacrylate (TMPTA) was used as a co‐agent. Electron‐beam‐initiated cross‐linking of the sheets was carried out at a dose of 40 kGy, and 3 phr of TMPTA based on the weight of rNBR was used. Properties such as tensile strength, Young's modulus, elongation at break, swelling percentage in oil, and morphology were studied. The results showed that the tensile properties had been improved by irradiation. The studies of swelling in oil revealed a higher cross‐link density in the irradiated blends compared to that in nonirradiated blends at similar blend ratios. Scanning electron microscopy studies revealed better adhesion between the phases and rough failure surfaces with a large number of tear lines which indicated a higher energy requirement for the failure of irradiated blends compared to that for nonirradiated blends. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Effects of cashew nut shell liquid as a plasticizer on cure characteristics,processability, and mechanical properties of 50 : 50 NR/EPDM blends: A comparison with paraffin oil

50 : 50 natural rubber (NR) and ethylene–propylene–diene monomer rubber (EPDM) blends were prepared with different contents of cashew nut shell liquid (CNSL), a natural product obtained from the shells of the cashew nut, as a plasticizer. For comparison, a commercial paraffin oil plasticizer was also used. The effect of plasticizer content on the cure characteristics, processability, and mechanical properties such as tensile strength, elongation at break, and Young's modulus before and after ageing was investigated. Scanning electron microscopy (SEM) was used to observe the blend morphology. The results indicated that the CNSL plasticizer resulted in lower Mooney viscosity and lower cure time of the 50 : 50 NR/EPDM blends. The incorporation of CNSL into 50 : 50 NR/EPDM blends improved tensile strength and elongation at break but decreased Young's modulus. On addition of CNSL the resistance of the blends to heat and weathering ageing improved. Scanning electron micrographs revealed that the morphology of the blend plasticized with CNSL is finer and more homogeneous compared with the blend plasticized with paraffin oil. Overall results indicate that CNSL can be used as a cheaper plasticizer to replace paraffin oil in NR/EPDM blends with improved processability and mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Efficiency of high energy electrons to produce polypropylene/natural rubber‐based thermoplastic elastomer

High energy electrons have been used to induce chemical crosslinking in 50/50 blend of polypropylene and natural rubber. The blend morphology was generated during melt mixing and not changed by high energy electron treatment in the solid state at room temperature. The variation of absorbed dose (150–350 kGy) at fixed electron energy (1.5 MeV) brings a dramatic change in the properties of the polymer blend. In addition, the effect of a polyfunctional monomer (PFM) and the absorbed dose on the tensile properties of the polymer blend was investigated. The presence of a PFM led to blends having an elongation at break of about 350% and a tensile strength of nearly 14 MPa after the treatment with a comparatively low dose of 150 kGy. The morphology of the blends was found to be co‐continuous. A plausible mechanistic pathway for the phenomenon leading to enhancement of property has been suggested for better understanding of structure–property‐relationship. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.     

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.     

Structure and mechanical properties of polysulfone‐based in situ composites

Composites based on the polysulfone of bisfenol A (PSF) and a liquid‐crystalline copolyester (Rodrun 5000) were obtained by two processing methods, (1) direct injection moulding (DI) and (2) extrusion followed by injection moulding (PI), across the whole composition range. The blends were immiscible and showed two pure amorphous phases. The inferior mechanical properties of PI blends, and their more difficult processing, meant that the PI procedure is not suitable in these blends. The generally linear relationship of the Young's modulus of the DI blends is due to the counteracting effects of the large orientation of the skin and its low thickness. The improvement in notched impact strength of PSF on the addition of small amounts of LCP indicated an important reduction in its notch sensibility. The tensile strength behaviour was close to linearity, with the exception of the 20/80 blend in which it was synergistic. This had been seen in previous thermoplastic/LCP blends, and depicts a behaviour reminiscent of rubber‐toughened blends. Copyright © 2004 Society of Chemical Industry     

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.     

Mechanical and thermal properties of LDPE‐cellulose acetate phthalate blends—Effect of maleic anhydride‐grafted LDPE compatibilizer

Biodegradable blends of LDPE and cellulose acetate phthalate have been prepared. Maleic anhydride‐grafted LDPE has been added as a compatibilizer to this blend. The elastic modulus and tensile strength has been considerably improved by adding LDPE‐g‐maleic anhydride compatibilizer. Scanning electron microscope micrographs reflected the observed results for the increase in mechanical properties of the blend. Further blend morphology exhibited a deformed matrix for the compatibilized blends. Thermogravimetric analysis studies showed two‐stage degradation for the blends. Differential scanning calorimetry thermograms showed a loss of crystallinity for the LDPE phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Tensile failure of γ-ray irradiated blends of high-density polyethylene and natural rubber

The effect of ⁶⁰Co γ-radiation on the tensile properties of thermoplastic elastomer blends of natural rubber (NR) and high-density polyethylene (HDPE) has been investigated. The samples were irradiated to absorbed doses ranging from 0.1 to 100 Mrad in air at room temperature (25°C) at a dose rate of 0.21 Mrad/hr. The effect of blend ratio and addition of carbon black (N 330) dicumyl peroxide (DCP) on the radiation resistance of the blends has also been studied. High energy radiation at a high dose rate was found to cause extensive crosslinking in the bulk, which in effect, caused a minima in the ultimate tensile strength in the range of 10–25 Mrad and a continuous decline in the elongation at break in all the blends. Chain scission, on the other hand, was restricted to the surface under the above-mentioned experimental conditions. This contention was substantiated by the results of irradiation of the samples in a nitrogen environment. Scanning electron microscopy (SEM) studies on the tensile fracture surface morphology of the blends have also been undertaken in order to gain insight to the mechanism of failure.     

The Effect of Dicumyl Peroxide Vulcanization on the Properties & Morphology of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber Blends

ABSTRACT

This article discusses some properties such as tensile properties, chemical and oil resistance, gel content, crystallinity, and morphology of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends. Dicumyl peroxide (DCP) was applied as a crosslinking agent. In terms of tensile properties, peroxide vulcanized blend shows higher tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) as compared with the unvulcanized blend. The elongation at break of the peroxide vulcanized blend is higher for the blend with NR rich content compared with the EPDM rich content. The improvements in chemical and oil resistance as well as gel content of peroxide vulcanized blends have also proved the formation of crosslinks in the rubber phase. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the crosslinks have occurred during dynamic vulcanization. Dynamical vulcanization with DCP has decreased the percent crystallinity of blends that can be attributed to the formation of crosslinks in the rubber.     

Studies on the properties and structure of electron‐beam crosslinked low‐density polyethylene/poly[ethylene‐co‐(vinyl acetate)] blends

Blends of low‐density polyethylene (LDPE) and poly[ethylene‐co‐(vinyl acetate)] (PEVA), crosslinked by electron‐beam (EB) radiation, formed separate crystalline lattices with a homogeneous amorphous phase. The crystallinity of the EB‐exposed samples slightly decreased, as verified by a slight reduction in the densities and melting heats and temperatures of the samples. The results obtained from both gel content and hot set tests showed that the degree of crosslinking in the amorphous regions was dependent on the dose and blend composition. The molecular weights between the crosslinks, measured from creep data, showed that an increasing PEVA content resulted in tighter network structures, thus supporting the idea that the crosslinking density at a given irradiation dose depends on the amorphous portions of the polymers. Addition of trimethylolpropane trimethacrylate as a radiation sensitizer enhanced the gel content of the neat polyethylene significantly, while the addition of an antioxidant showed the reverse effect. A significant improvement in the tensile strength of the neat PEVA samples was obtained upon EB radiation up to 210 kGy. The irradiated LDPE/PEVA blends showed improved tensile strength and elongation at break when compared to LDPE. Copyright © 2004 Society of Chemical Industry     

The toughness and morphology of (chlorinated poly[vinyl chloride])/(methyl methacrylate‐butadiene‐styrene) blends

A series of methyl methacrylate‐butadiene‐styrene (MBS) graft copolymers were synthesized via seeded emulsion polymerization techniques by grafting styrene and methyl methacrylate on poly(butadiene‐co‐styrene) (SBR) particles. The chlorinated poly(vinyl chloride) (CPVC)/MBS blends were obtained by melting MBS graft copolymers with CPVC resin, and the effect of the core/shell ratio of MBS graft copolymer and SBR content of CPVC/MBS blends on the mechanical properties and morphology of CPVC/MBS blends was studied. The results showed that, with the increase in the core/shell ratio, the impact strength of the blend increased and then decreased. It was found that, when the core/shell ratio was 50/50, the impact strength was about 155 J/m, and the tensile strength evidently increased. The toughness of the CPVC/MBS blend was closely related to the SBR content of the blend, and with the increasing of SBR content of blend, the impact strength of the blend increased. The morphology of CPVC/MBS blends was observed via scanning electron microscopy. Scanning electron microscopy indicated that the toughness of CPVC/MBS blend was consistence with the dispersion of MBS graft copolymers in the CPVC matrix. J. VINYL ADDIT. TECHNOL., 22:501–505, 2016. © 2015 Society of Plastics Engineers     

Mechanical and thermal properties of copoly(styrene/acrylonitrile) compatibilised Nylon–thermoplastic elastomer blends

Abstract

The effects of blend compositions on the mechanical and thermal properties of polymer blends containing Nylon 66 and a thermoplastic elastomer (TPE), Santoprene^®, have been studied. A 5% styrene/acrylonitrile copolymer was added to neat Nylon, TPE, and their blends. The blends were injection moulded and the tensile and impact properties were investigated. The morphology and thermal properties of the blends were observed using scanning electron microscopy and differential scanning calorimetry.

The presence of double melting temperatures showed that the Nylon 66 and TPE are immiscible. However, blending produced a modification of mechanical and thermal properties. At TPE/Nylon ratios above 50 : 50 the tensile properties of TPE improved. In addition the impact properties of Nylon improved above the 50 : 50 ratio, i.e. in the TPE rich region. Both the melting temperature and crystallinity were depressed in the region of 50 : 50 blend composition. The presence of two phases, which is evidence of immiscibility of the blends, was confirmed by scanning electron microscopy.     

Nanomodified fillers in chloroprene‐rubber‐compatibilized natural rubber/acrylonitrile–butadiene rubber blends

Because of the structural dissimilarity, natural rubber (NR) and acrylonitrile–butadiene rubber (NBR) are immiscible, and compatibilizers are used during their blending. Neoprene or chloroprene rubber (CR) has a polar chlorine part and a nonpolar hydrocarbon part. Also, it has many advantageous properties, such as oil resistance, toughness, a dynamic flex life, and adhesion capacity. Hence, it is not less scientific to use CR as a compatibilizer in the blending of NBR with NR. Because many fewer studies on the use of neoprene as a compatibilizer in NR–NBR blend preparation are available, efforts were made to prepare 20:80 NR–NBR blends with CR with the aim of studying the effect of poly(ethylene oxide) (PEO)‐coated nano calcium silicate along with nano N‐benzylimine aminothioformamide and stearic acid coated nano zinc oxide in the sulfur vulcanization of the blends. The optimum dosage of the compatibilizer was derived by the determination of the tensile properties, tear resistance, abrasion resistance, compressions set, and swelling values. The tensile strength, tear resistance, and abrasion resistance of the gum vulcanizates of the blend were improved by the compatibilizing action of CR up to 5 parts per hundred parts of rubber (phr). In the case of the filled vulcanizates, the tear resistance, 300% modulus, hardness, and abrasion resistance increased with increasing dosage of nano calcium silicate. The elongation at break percentage decreased as expected when there was an increase in the modulus. Scanning electron microscopy was used to study the phase morphology of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Use of poly(ethylene‐co‐vinyl alcohol) as compatibilizer in LDPE/thermoplastic tapioca starch blends

Poly(ethylene‐co‐vinyl alcohol) (EVOH) was used as a compatibilizer to make blends of low‐density polyethylene (LDPE) and plasticized starch (TS). The tensile properties and impact strength were measured and compared with those of neat LDPE. The morphology of the blend specimens, both fractured and unfractured, was observed by scanning electron microscopy. Comparison of the properties showed that the impact strength of the blend improves significantly by the addition of a compatibilizer even with a high TS loading of 40 and 50% (by weight). A high elongation at break almost matching that of neat polyethylene was also obtained. The blend morphology of the etched specimens revealed fine dispersion of the starch in the polyethylene matrix, while the fracture surface morphology clearly indicate that the failure of compatibilized blends occurs mainly by the ductile mode. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3126–3134, 2002     

氟橡胶/EPDM动态硫化共混物的研究

研究了动态硫化工艺条件和共混比对氟橡胶（ＦＫＭ）／ＥＰＤＭ共混物拉伸性能拉、热油老化性能和应力松弛性能的影响。结果表明：与直接静态硫化相比,动态硫化可避免两种硫化体系的相互影响;静态硫化共混物拉伸强度只有２ＭＰａ,而动态硫化共混物可达１０ＭＰａ以上;工艺条件对动态硫化共混物性能的影响不大;随共混物中ＥＰＤＭ用量的增大,共混物的热空气老化和热油老化性能均有所下降     

Improvement of Physicochemical Properties of Rubber Blends Between Nonirradiated and Irradiated Rubber Latexes by Radiation Vulcanization

Abstract

Nonirradiated natural rubber latex (NRL) and irradiated (12 kGy) rubber latex were blended in ratios of 100:0, 85:15, 65:35, 50:50, 35:65, 15:85, and 0:100 (v/v) to improve properties of the rubber latex. The blends were irradiated using different irradiation doses (0–20 kGy) in the presence of a radiation vulcanization accelerator (RVA), normal butyl acrylate (n-BA). The physicochemical properties of the nonirradiated latex, irradiated latex, and blend films were determined after leaching with distilled water. It was observed that the tensile strengths of the blend films increases with an increase in the content of the irradiated proportion and radiation doses. The composition of the blends and the doses of radiation were optimized. The maximum tensile strength (31.41 MPa) was found for the 50:50 composition of the blend with a 5 kGy radiation dose. The 100:0 blends, when irradiated, give the highest tensile strength (27.69 MPa) with 12 kGy but a 15:85 nonirradiated blend gives the tensile strength of 26.18 MPa.     

Characterization of epoxidized natural rubber/ethylene vinyl acetate (ENR‐50/EVA) blend: Effect of blend ratio

Epoxidized natural rubber/Ethylene vinyl acetate copolymer (ENR‐50/EVA) blends with different ratios were prepared by using a Haake internal mixer. The effect of the blend ratio on the processing, tensile properties (such as tensile strength, elongation at break, Young's modulus and stress–strain behavior), morphology, dynamic mechanical properties, and thermal properties has been investigated. The tensile properties increase with the increase of EVA content, whereas the stabilization torque increases with the increase of ENR‐50 content in the blend. In 40:60 and 50:50 blend of ENR‐50/EVA, both the phases exist as continuous phases, producing a co‐continuous morphology. At these blend ratio, the drastic change in properties were noted, indicating that the phase inversion occurs. The results on dynamic mechanical properties revealed that the blends are compatible. Blending of ENR‐50 and EVA lead to the improvement in thermal stability and 50:50 blend ratios is the most stable blend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1504–1515, 2006     

Effect of triblock copolymers on homogeneity,mechanical properties and swelling behavior of IIR/SBR rubber blends

The present research concerns with the preparation and characterization of isobutylene isoprene/butadiene–styrene rubber (IIR/SBR) blends with different blend ratios, in the presence and absence of styrene–isoprene–styrene (SIS) and styrene–isobutylene–styrene (SiBS) triblock copolymers to be tested as compatibilizers. Effect of the triblock copolymers on the blend homogeneity was investigated with the aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. Characterization of the rubber blends was conducted by measuring the physico-mechanical properties after and before thermal aging, in presence and absence of the triblock copolymers. In addition, weight swell % in toluene, motor oil and brake fluid of the rubber blend vulcanizates was assessed. The incorporation of SIS and SiBS triblock copolymers improved the homogeneity of IIR/SBR blends as well as increased both tensile strength and elongation at break of the rubber blend vulcanizates. Of the entire blend ratios examined, IIR/SBR (25/75) blend containing SIS compatibilizer possessed the best physico-mechanical properties (12.6 MPa tensile strength and 425 % elongation at break) and (14 MPa tensile strength and 555 % elongation at break) after and before thermal aging, respectively. Utilization of SIS and SiBS triblock copolymers enhanced the thermal stability of IIR/SBR blend vulcanizates. Moreover, IIR/SBR blends of different blend ratios showed superior swelling resistance in the brake fluid. IIR/SBR (25/75) blend containing SIS compatibilizer and cured with CBS/ZDEC/S vulcanizing system possessed the best physico-mechanical properties (14.4 MPa tensile strength and 440 % elongation at break) and (16.5 MPa tensile strength and 610 % elongation at break) after and before thermal aging, respectively.     

Effects of irradiation on the mechanical,electrical, and flammability properties of (low‐density polyethylene)/(ethylene‐[vinyl acetate] copolymer) blends containing alumina trihydrate

Alumina trihydrate (ATH) was added to (low‐density polyethylene)/(ethylene‐[vinyl acetate] copolymer) blends (LPEs) to enhance their flame resistance. The addition of substantial amounts of ATH has been known to have deleterious effects on the mechanical properties of such blends. Hence, electron beam irradiation was used to improve the mechanical properties of our ATH‐filled LPE specimens. The specimens were irradiated at 50 to 150 kGy before being cut into specified shapes for analysis. The increase in the irradiation dosage increased the gel content as a result of the formation of crosslinked networks. Also, the flame resistance of the LPE blends was enhanced by increasing both the loading level of ATH and the irradiation dosage. However, a high ATH loading level reduced tensile strength and elongation at break. Nevertheless, the electron beam irradiation maintained the tensile strength and elongation of the ATH‐filled blends. In addition, a higher content of ATH in the LPE blends showed reactive interaction with irradiation effects. A higher amount of ATH reduced the electrical resistivity of the blends, but analysis of their surface and volume resistivity showed that the electrical resistance of the ATH‐filled LPE blends could be improved by electron beam irradiation in the range of 50 to 150 kGy. J. VINYL ADDIT. TECHNOL., 20:91–98, 2014. © 2014 Society of Plastics Engineers