Kinsuk Naskar

Recent Developments on Thermoplastic Elastomers by Dynamic Vulcanization

A comprehensive overview is given of the recent developments of thermoplastic vulcanizates (TPVs) with special reference to the technological advancements. TPVs combine the high volume molding capability of thermoplastics with the elastomeric properties of thermoset rubber. Therefore, they lend themselves to a broad range of applications in various fields. TPVs represent the second largest group of soft thermoplastic elastomers, after styrenic-based block copolymers. TPVs have undergone evolutionary changes in terms of the selection of polymers, design of crosslinking, compounding techniques, and methods of production, and have achieved better elastic recovery, easy processability and low hardness etc.

Dynamically vulcanized PP/EPDM blends: Effects of different types of peroxides on the properties

Abstract Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates are thermoplastic elastomers produced by simultaneous mixing and crosslinking of a rubber and a thermoplastic. The effects of diff...

Thermoplastic elastomers based on pp/epdm blends by dynamic vulcanization

Abstract This review article introduces various aspects of dynamic vulcanization as applied to thermoplastic elastomers (TPEs). The classification of polymer blends and TPEs, the development of the...

Dynamically vulcanized PP/EPDM blends: Multifunctional peroxides as crosslinking agents. Part I

Abstract Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates are a special class of thermoplastic elastomers, produced by mixing and crosslinking of a rubber and a thermoplastic polymer simultaneously. In a previous study, it was demonstrated that the use of dicumyl peroxide in combination with triallyl cyanurate as crosslinking agents provides a good overall balance of physical properties of PP/EPDM TPVs. Commonly used peroxides like dicumyl peroxide generally produce volatile decomposition products, which sometimes provide a typical smell or show a blooming effect. In this paper multifunctional peroxides are described, which reduce the above-mentioned problems. They consist of a peroxide and co-agent-functionality combined in a single molecule. The multifunctional peroxides provide properties of TPVs, which are comparable with commonly employed co-agent assisted peroxides. The solubility and kinetic aspects of the various peroxides are highlighted, as well as the decomposition products of the mult...

Exploring the influence of electron beam irradiation on the morphology, physico-mechanical, thermal behaviour and performance properties of EVA and TPU blends

The effects of electron beam radiation (EBR) on the blends of ethylene vinyl acetate/thermoplastic polyurethane (EVA/TPU) at two different blend ratios prepared via melt blending technique were investigated. All the samples were irradiated by using a 2.5 MeV electron beam accelerating energy over a dose range from 25 to 200 kGy. The blends exhibit drastic improvement in the mechanical properties with increasing radiation dose upto an optimum dosage, beyond which the properties began to deteriorate. Modification of the blends via EBR enhances the elastic recovery of the blends resulting significant improvement in tension set behaviour. DSC study shows that electron beam irradiation causes a marginal change in melting temperature (Tm), glass transition temperature (Tg) and crystallization peak temperature (Tc) of EVA/TPU blends. Dynamic mechanical analysis (DMA) was conducted to investigate the change of loss tangent and storage modulus with varying radiation dose. Thermogravimetric analysis (TGA) suggests that irradiation induced crosslinks also help to improve the thermal stability of the blends to some extent. Scanning electron microscopy (SEM) study was performed to explore the changes in morphology before and after irradiation. All the irradiated blends have higher electrical resistivity than the blends without irradiation and the volume resistivity increases upto 150 kGy. The samples were found to exhibit remarkable improvement in oil resistance property after irradiation which is more prominent in EVA/TPU 70/30 blends.

Influence of Various Peroxides in PP/EPDM Thermoplastic Vulcanizates at Varied Blend Ratios

Thermoplastic vulcanizates (TPVs) or dynamic vulcanizates containing finely dispersed micron-size cross-linked rubber particles in a thermoplastic matrix exhibit performance properties of the conventional vulcanized rubbers, however, they can be processed as thermoplastics. The basic objective of the present study is to investigate the effects of different types of peroxides as cross-linking agents at varied PP/EPDM blend ratios in dynamically vulcanized products. The TPVs were prepared by batch melt mixing of polypropylene (PP) with ethylene propylene diene monomer (EPDM), using various peroxides and triallyl-cyanurate (TAC) as co-agent. The physical properties of the TPVs change significantly with the PP/EPDM blend ratios, chemical nature of the peroxides, the extent of cross-linking in the EPDM phase, and the extent of degradation in the PP phase. The reason of increased tensile strength, modulus, and hardness with the increasing amount of PP is due to the increased thermoplastic hard component in the blend. Irrespective of the PP/EPDM blend ratios, in most cases dicumyl-peroxide (DCP), out of four different types of peroxides investigated, gives the best overall balance of physical properties. Special emphasis is laid on the interpretation of the different behavior of the various peroxides.

Thermally cross-linked and sulphur-cured soft TPVs based on S-EB-S and S-SBR blends

Thermoplastic vulcanizate (TPV) is a specific group of elastomer alloy (EA), in which the rubber phase is selectively cross-linked by dynamic vulcanization and dispersed in the presence of a molten thermoplastic phase under intensive mixing. The development of binary blends, utilizing melt-blending technology of poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer (S-EB-S) and solution-polymerized styrene butadiene rubber (S-SBR) were investigated, as were the characteristic differences of these blends compared to other soft TPVs. Design of experiments (DOE) has been adopted to execute the optimum processing conditions in terms of mixing temperature, rotor speed and time of mixing by utilizing the Taguchis L9 methodology, and the measure of confidence has been accomplished using standard statistical technique of the analysis of variance (ANOVA). A novel, thermally cross-linked (TCL) TPV has emerged as a by-product of DOE. Thereafter, meticulous analysis and characterization have been conducted to understand the newly developed TPV system. Furthermore, both semi-efficient vulcanizate (SEV) and efficient vulcanizate (EV) sulphur-based curing systems have been designed by adopting the optimized processing conditions to cure the rubber phase, and a comparative study has been organized among the TCL, SEV and EV systems. Dynamic mechanical analysis (DMA) has revealed reduced rolling resistance for EV-cured TPVs compared to SEV- and TCL-cured systems, while still maintaining good wet grip by comparing the lost tangent values. Theoretical calculation of viscoelastic properties by adopting the Kerner model predicts primarily co-continuous morphology for the TPV systems, which is in good accordance with the experimental and morphological observations.

Optimization of Process Parameters of Immiscible Blends of Linear Low-Density Polyethylene and Poly Dimethyl Siloxane Rubber Using Taguchi Methodology

Blends of Linear low density polyethylene (LLDPE) and Poly dimethyl siloxane rubber (PDMS) are immiscible due to dissimilarity in their structures and wide difference in their surface energies. The processing parameters such as temperature, rotor speed and time in an internal mixer (Brabender Plasticorder) were optimized by using Design of Experiments (DOE) as per Taguchi Methodology, for a blend ratio of 50:50. Mechanical properties such as tensile strength and impact strength were chosen as the criteria for assessing the optimization phenomenon. The optimum processing parameters were found to be a temperature of 200°C, a rotor speed of 100 rpm and the time as 8 minutes.

Selective dispersion of carbon fillers into dynamically vulcanized rubber/plastic blends: a thermodynamic approach to evaluate polymer reinforcement and conductivity enhancement

In this present work, the fundamental aspect of filler migration in a newly introduced thermoplastic vulcanizate based on ethylene octene copolymer and natural rubber, fabricated via semi-efficient sulphur vulcanization, has been investigated through thermodynamic calculations. Meticulous analysis has been conducted through different spectroscopic and microscopic techniques in order to identify the more favorable phase for filler dispersion. However, the consequent effect of phase selective filler dispersion has actually been realized from differential scanning calorimetry and X-ray diffraction, which, in turn, has successfully explained the observed mechanical and dynamic-mechanical properties. The upshifted G band absorbance frequencies obtained from Raman spectroscopy, on the other hand, have effectively explained the observed electrical properties. This work elucidates the fundamental understanding of polymer reinforcement as well as conductivity enhancement by incorporating carbon fillers into a newly introduced TPV system, which may be considered as a highly potential material for future automotive applications.

Novel Styrenic Thermoplastic Elastomers from Blends with Special Reference to Compatibilization and Dynamic Vulcanization

A thermoplastic elastomer (TPE) is a rubbery material with final properties and functional performance similar to those of a conventional vulcanized rubber at ambient temperature, yet it can be processed in a molten condition as a thermoplastic polymer at elevated temperature. The main objectives of the present investigation are: to prepare novel styrenic-based thermoplastic elastomers based on blends of a thermoplastic (polystyrene or styrene acrylonitrile) with a rubber (styrene butadiene or ethylene vinylacetate) and to investigate the interaction between various polymers with special reference to compatibilization via oxazoline-modified polystyrene or oxazoline-modified styrene acrylonitrile and dynamic vulcanization. Styrene acrylonitrile/ethylene vinylacetate blends are found to exhibit better overall properties, especially tensile strength, elongation at break and tension set. The solubility or interaction parameter and the morphology of the blends are the key parameters, which basically govern the final properties of blends. Physical properties of these blends have been correlated with the interaction parameter and final morphology.