Exploring the effect of radiation crosslinking on the physico‐mechanical,dynamic mechanical and dielectric properties of EOC–PDMS blends for cable insulation applications

This work focuses on the effect of electron beam irradiation on the physico‐mechanical, dynamic mechanical and dielectric properties of blends based on ethylene octene copolymer (EOC) and poly dimethyl siloxane (PDMS) rubber. It is found that electron beam irradiation caused considerable improvement in the physico‐mechanical properties; the tensile strength was enhanced by nearly 35% for 70:30 EOC:PDMS blend. Phase morphology of the blends analyzed before irradiation by scanning electron microscopy (SEM) exhibited droplet/matrix morphology with sizes of the PDMS rubber domain varying from 0.55 µm to 0.47 µm as the amount of PDMS rubber decreased from 30 wt% to 10 wt%. This reduction in the PDMS rubber domain has been correlated with the physico‐mechanical properties of the blends. Further, the dynamic mechanical properties and creep behavior of these EOC:PDMS blends before and after irradiation has been studied. It is inferred that the 70:30 blend after radiation crosslinking shows a 17% decrease in the creep compliance, i.e. higher creep resistance compared to neat blends. All the radiation crosslinked blends exhibited lower dielectric constant, lower dielectric loss and higher electrical resistivity as compared to the virgin blends which makes it suitable for cable insulating application. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

In this study, waste tire dust is recycled as filler and blended with ethylene-propylene diene monomer (EPDM) rubber. Three different polyfuntional monomers (PFMs) are incorporated into the standard formulation and irradiated under electron beam at different doses up to maximum of 100 kGy. The combined effects of PFMs and absorbed dose on the physical properties of EPDM/WTD blend are measured and compared with sulfur crosslinked formulation. Thermogravimetric analysis showed that radiation developed better crosslinked network with higher thermal stability than sulfur crosslinked structure. The physical properties of radiation crosslinked blend are similar to the sulfur crosslinked blend. The absence of toxic chemicals/additives in radiation crosslinked blends made them an ideal candidate for many applications such as roof sealing sheets, water retention pond, playground mat, sealing profile for windows etc.     

Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δ_max were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002     

Studies on thermal, thermal ageing and morphological characteristics of EPDM-g-VTES/LLDPE

A novel graft copolymer of vinyltriethoxysilane onto ethylene propylene diene terpolymer has been developed by grafting varying contents of VTES using dicumyl peroxide as an initiator in a twin-screw extruder. Grafting of VTES and EPDM has been ascertained using FTIR. The EPDM-g-VTES developed has been blended with different weight percentage of linear low density polyethylene [LLDPE] by melt mixing. Thermal, thermal ageing and morphological behaviour of the blends are studied with respect to the effect of blend composition, static vulcanization and dynamic vulcanization with varying quantities of VTES and LLDPE. The incorporation of silane moiety onto EPDM raises the inception and final decomposition temperature. The stability EPDM-g-VTES/LLDPE blend increases with increase in concentration of EPDM-g-VTES due to thermally stable Si-O-Si linkage. It was ascertain from SEM micrograph that EPDM-g-VTES/LLDPE blends lead to formation of interpenetrating crosslinked network during hot water treatment and by treatment with DCP, respectively. The linear, statically vulcanized, dynamically vulcanized and filled blends of EPDM-g-VTES/LLDPE have been characterized to assess the suitability of the blends for high performance applications. In addition, it is also observed that the incorporation of fillers improves thermal stability of the blends.     

Two‐way multi‐shape memory properties of peroxide crosslinked ethylene vinyl‐acetate copolymer (EVA)/polycaprolactone (PCL) blends

Rare studies have investigated on the 2‐way shape memory crosslinked blends with multiple shape memory behavior up to date. To consider the merit of commercial cost‐competitive crystalline polymers, ethylene vinyl‐acetate copolymer (EVA) / polycaprolactone (PCL) blends (60/40 and 30/70) were peroxide‐cured to form the 2‐way multi‐shape memory crosslinked blends using a melt‐blending method. Both resins were selected to have a similar controlled crosslinking degree, which allowed us to distinctly evaluate their actuation contributions from the cooling‐induced elongation (crystallization) and from the entropy‐driven elongation during cooling process, respectively. In the 2‐way process for the 60/40 system, 2 respective peaks contributed from the cooling‐induced crystallization of EVA and PCL in the cooling curves based on the strain derivate rates at various temperatures were observed. After the cooling process under the loading stress of 150 kPa, the 2‐step heating‐induced contraction process with increasing temperature started at 54.1°C above the melting temperature of PCL at 52.3°C and EVA at 78.3°C, demonstrating 2‐way multi‐shape memory behavior. The multi‐step behavior was more prominent at higher PCL composition and higher load for the 30/70 system. It was found that the entropy‐driven contribution to the overall actuation magnitude increased with increasing nominal loads due to the increased orientation of molecular networks in the blends. The current approach offers numerous possibilities in preparing 2‐way multi‐shape memory crosslinked blends.     

The role of thiophosphoryl disulfide on the co‐cure of CR‐EPDM blends

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS) has been used as a coupling cum curing agent for the compatibilization of blends of ethylene propylene diene monomer rubber (EPDM) with chloroprene rubber (CR). Electrical and mechanical properties of the blend vulcanizates have been studied to find the efficiency of the vulcanizing cum coupling activity of DIPDIS. The study reveals that CR in the presence of DIPDIS greatly improves the physical properties of EPDM. It is noted that the physical properties of the vulcanizates obtained from CR‐EPDM blend depend upon CR:EPDM ratio. The scanning electron microscopy (SEM) study reveals that it is possible to form a coherent blend of CR and EPDM in the presence of DIPDIS. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigation of phase morphology of incompatible polyethylene/nylon 6 blends containing EPDM-based functionalized compatibilizers

Graft copolymer and graft terpolymer were prepared by solution grafting of maleic anhydride (MAH) or acrylonitrile (AN) alone and mixture of MAH and AN on to ethylene–propylene–diene terpolymer (EPDM) using benzoyl peroxide (BPO) as an initiator. The resulting EPDM-g-MAH, EPDM-g-AN and EPDM-g-(MAH-co-AN) have been used to obtain a binary blend of Nylon 6/functionalized EPDM and a ternary blend of polyethylene/Nylon 6/functionalized EPDM by melt blending. The effects of the nature and the amount of the grafted species on the phase morphology, crystallization behavior and mechanical properties of the blends were characterized through scanning electron microscopy, optical microscopy, infrared spectroscopy and using a dynamic mechanical analyzer. From the morphological study, it can clearly be seen that the presence of the functionalized EPDMs in these blends resulted in an improvement of the dispersion degree in incompatible polyethylene/Nylon 6 blends.     

Thermogravimetric and wide angle X-ray diffraction analysis of thermoplastic elastomers from nylon copolymer and EPDM rubber

Nylon copolymer (PA6, 66) and ethylene propylene diene (EPDM) blends with and without compatibilizer were prepared by melt mixing using Brabender Plasticorder. The thermal stability of nylon copolymer (PA6, 66)/ethylene propylene diene rubber (EPDM) blends was studied using thermogravimetric analysis (TGA). The morphology of the blends was investigated using scanning electron microscopy (SEM). In this work, the effects of blend ratio and compatibilisation on thermal stability and crystallinity were investigated. The incorporation of EPDM rubber was found to improve the thermal stability of nylon copolymer. The kinetic parameters of the degradation process were also studied. A good correlation was observed between the thermal properties and phase morphology of the blends. By applying Coats and Redfern method, the activation energies of various blends were derived from the Thermogravimetric curves. The compatibilization of the blends using EPM-g-MA has increased the degradation temperature and decreased the weight loss. EPM-g-MA is an effective compatibilizer as it increases the decomposition temperature and thermal stability of the blends. Crystallinity of various systems has been studied using wide angle X-ray scattering (WAXS). The addition of EPDM decreases the crystallinity of the blend systems.     

Phase behavior,crystallization, and morphology in thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin and poly(ϵ‐caprolactone)

Thermosetting blends of a biodegradable poly(ethylene glycol)‐type epoxy resin (PEG‐ER) and poly(?‐caprolactone) (PCL) were prepared via an in situ curing reaction of poly(ethylene glycol) diglycidyl ether (PEGDGE) and maleic anhydride (MAH) in the presence of PCL. The miscibility, phase behavior, crystallization, and morphology of these blends were investigated. The uncured PCL/PEGDGE blends were miscible, mainly because of the entropic contribution, as the molecular weight of PEGDGE was very low. The crystallization and melting behavior of both PCL and the poly(ethylene glycol) (PEG) segment of PEGDGE were less affected in the uncured PCL/PEGDGE blends because of the very close glass‐transition temperatures of PCL and PEGDGE. However, the cured PCL/PEG‐ER blends were immiscible and exhibited two separate glass transitions, as revealed by differential scanning calorimetry and dynamic mechanical analysis. There existed two phases in the cured PCL/PEG‐ER blends, that is, a PCL‐rich phase and a PEG‐ER crosslinked phase composed of an MAH‐cured PEGDGE network. The crystallization of PCL was slightly enhanced in the cured blends because of the phase‐separated nature; meanwhile, the PEG segment was highly restricted in the crosslinked network and was noncrystallizable in the cured blends. The phase structure and morphology of the cured PCL/PEG‐ER blends were examined with scanning electron microscopy; a variety of phase morphologies were observed that depended on the blend composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2833–2843, 2004     

The role of thiophosphoryl disulfide on the co‐cure of CR‐EPDM blends: effect of white fillers

Bis(diisopropyl) thiophosphoryl disulfide (DIPDIS) being a rubber accelerator has a definite role as a coupling agent in the silica filled polychloroprene rubber with ethylene propylene diene rubber (CR‐EPDM) blends. Diethylene glycol can further improve the beneficial effect of DIPDIS in silica filled CR‐EPDM blends. Two‐stage vulcanization technique further improves the physical properties of silica filled CR‐EPDM blends. The results have been compared with non‐reinforcing calcium carbonate filled systems. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the silica filled CR‐EPDM blend vulcanizates obtained from this two‐stage process. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of Electron Beam Irradiation on the Properties of High Styrene Rubber/Styrene Butadiene Rubber Blends

High styrene rubber (HSR)/styrene butadiene rubber (SBR) blends at different ratios were exposed to various doses of electron beam irradiation. The effect of irradiation dose and blend ratios on the mechanical properties and shape memory characteristics in terms of strain fixation) rate (R_f) and strain recovery rate (R_r) was investigated. The results revealed that rich styrene blends displayed higher tensile strength and hardness than low styrene content blends at all irradiation doses. However, elongation at break, and toughness were lower for rich styrene content. Also, it was observed that for most specimens, the tensile strength, elongation at break and hardness increases up to100 kGy. Increasing irradiation doses resulted in slight deterioration in some mechanical properties only for low styrene content at150 kGy. According to the normalized tensile stress at 25% elongation, it was found that the contribution of irradiation in enhancing the mechanical properties is higher for rich butadiene blends. On the other hand, it was observed that rich styrene content blends possess higher R_f and R_r at all the irradiation doses and stretching temperatures. However, the increase of irradiation dose decreases R_f values; the extent of this decrease depends on the blend ratios. Conversely, for all blends, R_r were increased by increasing irradiation dose and styrene content ratios.     

iPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为

用DSC、~(13)C-NMR、SEM和WAXD等方法研究了IPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为。实验结果表明,EPDM与PE组分的相容性优于与PP组分的相容性,多数EPDM分子链段能够分布在PE组分中;EPDM含量为15％时,共混物相容性最好,SEM照片呈现晶体微区的互连或网络状结构;随EPDM含量增加,总结晶度X_c减小,其中PE组分结晶度X_(cE)有较大幅度地降低,PP组分结晶度X_(cp)基本没有变化,这可以根据EPDM和PE、PP之间相容性的差异以及PE、PP两组分在冷却过程中不同的结晶行为来解释。     

Studies on phase morphology and thermo-physical properties of nitrile rubber blends

The study deals with the morphological and thermal analysis of binary rubber blends of acrylonitrile-co-butadiene rubber (NBR) with another polymer. Either ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA), chlorosulphonated polyethylene (CSM), or polyvinyl chloride (PVC) has been selected for the second phase. Depending on the relative polarity and interaction parameter of the components, the binary blends showed development of a bi-phasic morphology through scanning electron microscopy (SEM). Use of different types of thermal analysis techniques revealed that these blends are generally incompatible excepting one of NBR and PVC. Derivative differential scanning calorimetry (DDSC), in place of conventional DSC, has been used to characterize the compatibility behavior of the blends. NBR–PVC shows appearance of only one glass transition temperature (T _g) averaging the individual T _g’s of the blend components. The partially missible blend of NBR and CSM shows a broadening of T _g interval between the phase components, while the immiscible blends of either NBR–EPDM or NBR–EVA do not show any change in T _g values corresponding to the individual rubbers of their blend. The experimental T _g values were also compared with those calculated theoretically by Fox equation and observed to match closely with each other. Studies have also been made to evaluate the thermal stability of these blends by thermo-gravimetric analysis (TG) and evaluation of activation energy of respective decomposition processes by Flynn and Wall method. Thermo-mechanical analysis (TMA) was found to be effective for comparison of creep recovery and dimensional stability of the blends both at sub-ambient as well as at elevated temperatures.     

Chemical modification of polyolefin blends

The effect of crosslinking on the properties of low density polyethylene / polypropylene blends was investigated. It was found that crosslinking results in much higher deformability of the blends compared to uncrosslinked materials. A decrease in crystalline portion determined by DSC leads to lower modulus in crosslinked samples. High drawability of crosslinked samples is mainly attributed to peculiar behaviour of PE part of the crosslinked blend where thicker lamellae are formed during drawing.     

Relationship between structure and rheological properties in the melt of polymers containing spherical inclusions

The linear viscoelastic behavior of model rubbertoughened polymer melts has been studied. The most significant influence of the dispersed crosslinked rubber phase on the melt rheology of the blends is the existence of a secondary plateau for the storage modulus G′ at low frequencies. This behavior was ascribed to a percolation phenomenon, leading to the formation of a threedimensional network of inclusions, and contributing to the elasticity at low frequencies of the blend. Two different systems were investigated: (a) a polystyrene matrix with crosslinked and structured latex particles and (b) silicon oil matrices with homogeneous crosslinked PMMA particles. An initial shearing history was found to influence the dynamic mechanical properties of the molten blends and in particular to lower the lowfrequency plateau value for G′. During a subsequent annealing, the plateau modulus increases again. These results are in agreement with the assumption of a particle network.     

Study on the toughening mechanism of PP/EVA dynamically crosslinked blend

The toughening mechanism of polypropylene (PP)/ethylene-co-vinyl acetate (EVA) dynamically crosslinked blend was investigated. The results indicated that dynamical crosslinking technology not only improved the interfacial adhesion between PP and EVA, but also increased the mechanical properties of PP/EVA blend. The quantitative and qualitative analysis of scanning electron microscopy (SEM) micrographs demonstrated that dynamical crosslinking technology could refine EVA particles in PP/EVA blend and promote the size distribution of EVA particles. The critical matrix ligament thickness of dynamically crosslinked and uncrosslinked blend was about 0.55 μm and 0.6 μm, respectively, indicating that the brittle-ductile transition occurred. Dynamic mechanical analysis (DMA) results illustrated that the tan δ peak of PP component in the dynamically crosslinked blend moved toward lower temperature compared with that of pure PP and the PP component in uncrosslinked blend; and the tan δ value of the dynamically crosslinked blend was higher than that of the uncrosslinked blend, which interpreted the toughening mechanism of dynamical crosslinking technology from the dynamic mechanical property of the blend.     

iPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为

 用DSC、¹³C-NMR、SEM和WAXD等方法研究了IPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为。实验结果表明,EPDM与PE组分的相容性优于与PP组分的相容性,多数EPDM分子链段能够分布在PE组分中;EPDM含量为15％时,共混物相容性最好,SEM照片呈现晶体微区的互连或网络状结构;随EPDM含量增加,总结晶度X_c减小,其中PE组分结晶度X_cE有较大幅度地降低,PP组分结晶度X_cp基本没有变化,这可以根据EPDM和PE、PP之间相容性的差异以及PE、PP两组分在冷却过程中不同的结晶行为来解释。     

Physico-Mechanical Characteristics of Some EPDM/Plasticized PVC Blends

Summary: In this study were prepared blends based on ethylene propylene terpolymer rubber (EPDM) and plasticized poly (vinyl chloride) (PVC). These blends are immiscible and need to be compatibilized. The following compatibilization methods were used: (1) addition of a compatibilization agent; there were used: maleinized EPDM, maleinized polyethylene (PE), chlorinated polyethylene (CPE) and maleinized polypropylene (PP); chlorinated polyethylene has proved to be the most efficient; the amount of the added CPE giving the best physico-mechanical characteristics was of 7,5 parts to 100 polymer parts; (2) reactive compatibilization, using crosslinked copolymer formation strategy; three different crosslinking systems were used: (a) common method with sulphur and accelerators, (b) crosslinking with benzoyl peroxide and trimethylpropane trimethacrylate (TMPT DL 75), (c) vulcanization with phenol resin and tin chloride. The best physico-mechanical characteristics were obtained with the EPDM/plasticized PVC blends crosslinked with 8 phr phenol resin. Such types of polymer blends can be processed by methods specific for plastics, removing thus vulcanization operation required in case of elastomers. These blends can be used in the manufacture of hoses, gaskets, footwear constituents etc.     

Thermo‐responsive shape memory behavior of poly(styrene‐b‐isoprene‐b‐styrene)/ethylene‐1‐octene copolymer thermoplastic elastomer blends

Thermally‐triggered shape memory polymers (SMPs) are smart materials, which are capable of changing their shapes when they are exposed a heat stimulant. Blending semi‐crystalline and elastomeric polymers is an easy and low‐cost way to obtain thermo‐responsive SMPs. In this work, novel poly(ethylene‐co‐1‐octene) (PEO) and poly(styrene‐b‐isoprene‐b‐styrene) (SIS) thermoplastic elastomer blends were prepared via melt blending method. The morphological, mechanical, rheological properties and shape memory behaviours of the blends were investigated in detail. In morphological analysis, co‐continuous morphology was found for 50 wt% PEO/50 wt% SIS and 60 wt% PEO/40 wt% SIS (60PEO/40SIS) blends. The shape memory analysis performing by dynamic mechanical analyzer showed that the 60PEO/40SIS blend also exhibited the optimum shape memory performance with 95.74% shape fixing and 98.98% shape recovery. Qualitatively shape memory analysis in hot‐water pointed out that the amount of semi‐crystalline PEO promotes shape fixing ability of the blends whereas SIS content enhances shape recovery capability. Although the SIS and PEO are immiscible polymers, the blends of them were exhibited good elastomeric properties with regard to tensile strength, toughness, and elongation at break.     

Processing,properties and morphology of polypropylene-epdm blends

Blends of polypropylene and an elastomer (ethylene propylene diene terpolymer, EPDM) are systematically investigated to determine the effect of the rubber on the polymer properties. Five compositions on the complete range of blend compositions are analyzed. The study reported here is a first of a series which main objective is to analyze in a systematic way the influence of the different factors that determine the effectiveness of EPDM as an impact modifier for PP. In this first part of the study, the processing behavior of the PP-EPDM blends are analyzed and the mechanical properties of the processed blends (tensile, flexural and impact resistance) are examined. Halpin-Tsai and porosity models successfully represent the mechanical behavior of the blends. The model results allow a physical interpretation of the role of the dispersed phase in terms of the aspect ratio and of the stress concentration factors associated to the dispersed particles. Moreover, the mechanical properties are correlated with the morphology of the blends studied by scanning electron microscopy, where two phases are clearly observed in the complete range of compositions. The results show that PP-EPDM blends with at low rubber content present a good processability, without significant deterioration with respect to neat PP and with a considerable improvement of the room and low temperature performance.