Thermoplastic Dynamic Vulcanizates Research Articles

In situ–produced polyurethane-based thermoplastic elastomers: the effect of the acrylonitrile content of the rubber phase

We prepared thermoplastic dynamic vulcanizates (TDVs) with an in situ–produced thermoplastic polyurethane (TPU) matrix. We used unfilled acrylonitrile butadiene rubber (NBR) with different acrylonitrile contents and investigated the effect of the polarity of the rubber phase on the properties of the TDV samples. The results show that the acrylonitrile (AN) content of the rubbers affects the tensile strength and modulus slightly but the strain at break of the TDVs only negligibly. The results of TDVs are in between those of TPU and unfilled NBRs, demonstrating the feasibility of the TPU/NBR combination.

Preparation and Characterization of Intrinsically Compatibilized Thermoplastic Polyurethane and Silicone Rubber

Front Cover: In article number 2100420 by Lan Cao, Chengzhong Zong, and co-workers, hydroxybutane-terminated polydimethylsiloxane (PDMS) block thermoplastic polyurethane (TPU) is used as the matrix and methyl vinyl silicone rubber (VMQ) to prepare thermoplastic dynamic vulcanizates (TPV). PDMS essentially compatibilizes molecular chains, which not only affects the microstructure, but also has a series of effects on the macroscopic properties of TPU/VMQ-based TPVs.

Preparation and Characterization of Intrinsically Compatibilized Thermoplastic Polyurethane and Silicone Rubber

AbstractTo combine the excellent properties of thermoplastic polyurethane (TPU) with methyl vinyl silicone rubber (VMQ), thermoplastic dynamic vulcanizates (TPVs) are synthesized. An essentially compatibilized method is used to resolve the thermodynamic incompatibility between TPU and VMQ. The principle is that the hydroxybutane‐terminated polydimethylsiloxane (PDMS) block on the TPU will increase the microphase separation of the matrix, but it will also increase the phase compatibility through similar compatibility with VMQ. Moreover, a series of effects of PDMS on the microstructure and macroscopic properties of TPV have been explored to find the influence law of PDMS, which will guide the application of TPV in various environments.

Development of Polypropylene-based Thermoplastic Elastomers with Crumb Rubber by Dynamic Vulcanization: A Potential Route for Rubber Recycling

In our current paper the preparation and properties of thermoplastic elastomer produced by dynamic vulcanization is presented and discussed. We dynamically vulcanized natural and styrene butadiene rubber (NR/SBR) phase by continuous extrusion. Dispersion and in-situ vulcanization of the rubber phase occurred simultaneously in a co-rotating twin screw extruder. We used a random polypropylene copolymer (rPP) as the thermoplastic matrix and untreated crumb rubber (CR) to partially substitute the neat fresh rubber in order to check whether this is a potential recycling route for waste rubber products. We studied the effect of various rubber formulations, various processing conditions (screw speed and configuration) and various CR particle size distributions by characterizing the mechanical performance of the thermoplastic dynamic vulcanizates (TDVs) with tensile and hardness tests and their morphology by evaluating SEM micrographs taken from the fracture surfaces of the tensile specimens. The results showed that increasing screw speed and more high-shear elements in the screw setup led to a finer dispersion of the rubber phase, resulting in improved mechanical properties. The ultimate tensile properties of the best TDVs reached 20.5 MPa in tensile strength and 550 % in strain at break. However, partial replacement of the fresh rubber with untreated CR caused a significant deterioration in mechanical properties, due to poor adhesion between the CR particles and the matrix and rubber. This suggests that some kind of pre-treatment (e.g. by microwave or other devulcanization techniques) is necessary to enhance the surface activity of the CR particles.

Extension of the pavement service life by bitumen modification with thermoplastic dynamic vulcanizates based on polymer wastes

Extension of the pavement service life by bitumen modification with thermoplastic dynamic vulcanizates based on polymer wastes

Thermoplastic Dynamic Vulcanizates with In Situ Synthesized Segmented Polyurethane Matrix.

The aim of this paper was the detailed investigation of the properties of one-shot bulk polymerized thermoplastic polyurethanes (TPUs) produced with different processing temperatures and the properties of thermoplastic dynamic vulcanizates (TDVs) made by utilizing such in situ synthetized TPUs as their matrix polymer. We combined TPUs and conventional crosslinked rubbers in order to create TDVs by dynamic vulcanization in an internal mixer. The rubber phase was based on three different rubber types: acrylonitrile butadiene rubber (NBR), carboxylated acrylonitrile butadiene rubber (XNBR), and epoxidized natural rubber (ENR). Our goal was to investigate the effect of different processing conditions and material combinations on the properties of the resulting TDVs with the opportunity of improving the interfacial connection between the two phases by chemically bonding the crosslinked rubber phase to the TPU matrix. Therefore, the matrix TPU was synthesized in situ during compounding from diisocyanate, diol, and polyol in parallel with the dynamic vulcanization of the rubber mixture. The mechanical properties were examined by tensile and dynamical mechanical analysis (DMTA) tests. The morphology of the resulting TDVs was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM) and the thermal properties by differential scanning calorimetry (DSC). Based on these results, the initial temperature of 125 °C is the most suitable for the production of TDVs. Based on the atomic force micrographs, it can be assumed that phase separation occurred in the TPU matrix and we managed to evenly distribute the rubber phase in the TDVs. However, based on the SEM images, these dispersed rubber particles tended to agglomerate and form a quasi-continuous secondary phase where rubber particles were held together by secondary forces (dipole–dipole and hydrogen bonding) and can be broken up reversibly by heat and/or shear. In terms of mechanical properties, the TDVs we produced are on a par with commercially available TDVs with similar hardness.

Microwave Devulcanized Crumb Rubbers in Polypropylene Based Thermoplastic Dynamic Vulcanizates.

Because of the chemically crosslinked 3D molecular structure of rubbers, their recycling is a challenging task, especially when cost efficiency is also considered. One of the most straightforward procedures is the grinding of discarded rubber products with subsequent devulcanization. The devulcanized rubber can be used as a feedstock for fresh rubber compounds or can be blended with uncured virgin rubber and thermoplastic polymers to form thermoplastic dynamic vulcanizates (TDVs). TDVs combine the beneficial (re)processability of thermoplastics and the elastic properties of rubbers. Our current work focuses on the development of polypropylene (PP)-based TDVs with the use of a tire model rubber (MR) composed of natural rubber (NR) and styrene-butadiene rubber (SBR) in a ratio of 70/30. The research target was the partial substitution of the above fresh MR by microwave devulcanized crumb rubber (dCR). TDVs were produced by continuous extrusion, and the effects of composition (PP/MR/dCR = 40/60/0…50/35/15) and processing parameters (different screw configurations, temperature profiles, the feeding method of PP) were investigated. Results showed that the fresh rubber compound can be replaced up to 10 wt % without compromising the mechanical properties of the resulting TDV.

Effects of blend composition and dynamic vulcanization on the morphology and dynamic viscoelastic properties of PP/EPDM blends

AbstractThe morphology and dynamic viscoelastic properties of isotactic polypropylene (PP) blended with oil‐free/oil‐extended ethylene–propylene–diene (EPDM) rubbers were studied. Unvulcanized and dynamically vulcanized blends with the compositions PP/EPDM = 50/50 and = 30/70 were investigated. The morphology was observed by phase contrasted atomic force microscopy. The dynamic viscoelastic properties were determined with a rheometer of plate–plate configuration. It was shown that the rheological behavior was strongly affected by both the composition and the morphology of the blends. Significant improvement in the flowability of the dynamically vulcanized blends was observed when oil‐extended EPDM was used instead of the oil‐free version. It was demonstrated that the rheological properties are mostly controlled by the elastomer phase at low frequencies, while in the high‐frequency range the influence of PP becomes dominant. The peculiarities in the rheological behavior of the thermoplastic elastomers (uncured blends, TPE) and thermoplastic dynamic vulcanizates (TPV, dynamically cured blends) containing oil‐extended EPDMs were traced to a limited compatibility between the PP and EPDM components in the melt. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Influence of Engage® copolymer type on the properties of Engage®/silicone rubber-based thermoplastic dynamic vulcanizates

Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomers, which are produced by simultaneously mixing and crosslinking a rubber with a thermoplastic polymer at an elevated temperature. Peroxide-cured TPVs based on blends of silicone rubber and thermoplastic Engage of two different types, mainly ethylene-octene and ethylenebutene copolymers at different blend ratios have been developed. A detailed comparative study of ethylene-octene vs. ethylene-butene based TPVs are mainly focused in this paper. These TPVs exhibit very good overall mechanical and electrical properties. With increasing amount of Engage in the blends at a fixed concentration of peroxide and coagent, tensile strength, modulus and hardness of the TPVs were found to increase considerably. Ageing characteristics and recyclability of silicone rubber based TPVs are also found excellent. Rheological studies confirm the pseudoplastic nature of these TPVs.

Unlubricated sliding and rolling wear of thermoplastic dynamic vulcanizates (Santoprene ®) against steel

The friction, sliding and rolling wear characteristics of thermoplastic dynamic vulcanizates (TPV; Santoprene ® grades), composed of polypropylene (PP), ethylene/propylene/diene rubber (EPDM) and extender oil, were studied against steel counterparts in dry condition. The composition and basic mechanical properties of the TPV of various hardness (Shore A = 60°, 70° and 80°) were evaluated. The wear performance of the TPVs was investigated in different tribotests, viz. pin-on-plate (POP), cylinder-on-plate (fretting) and rolling ball-on-plate (RBOP), whereby “plate” was always the rubber. From the above tests the coefficient of friction (COF) and specific wear rate were determined. It was established that with increasing hardness usually both COF and the specific wear rate were reduced. Values of the COF and wear rate depended strongly on the configuration and testing parameters of the related tribotests. The wear mechanisms were concluded by inspecting the worn surfaces by white light profilometry and scanning electron microscopy (SEM), respectively, and discussed.

Influence of Gamma-Irradiation on Dielectric Properties of Recycled Polyethylene Composites

AbstractThe influence of γ-irradiation on the dielectric losses (tg δ) and permittivity (ε′) of recycled high density polyethylene (HDPER) thermoplastic dynamic vulcanizates (TDV) has been investigated. The materials and composites that were studied include HDPER:EPDM, HDPER+EPDM+GTR, HDPER+EPDM+GTR/plast; EPDM (ethylene-propylene diamine).The experimental data obtained shows significant differences between dielectric properties different samples, as well as between the unirradiated and γ-irradiated samples.

PP/EPDM‐based thermoplastic dynamic vulcanizates with organoclay: morphology, mechanical and viscoelastic properties

AbstractDynamically vulcanized nanocomposite thermoplastic vulcanizates (NC‐TPVs) based on ethylene‐propylene‐diene rubber (EPDM) and melt intercalated hybrid of poly(propylene) (PP)/maleic anhydride grafted poly(propylene) (PP‐g‐MA) with organo‐modified montmorillonite (org‐MMT) were prepared. X‐ray diffraction (XRD) analysis and scanning electron microscopy (SEM) examination have been performed to evaluate the extent of the intercalation, as well as to characterize the microstructure developed during dynamic vulcanization. The organocaly was better intercalated and dispersed in the PP matrix of the NC‐TPV samples at low clay contents. The NC‐TPV samples showed a matrix‐disperse type of morphology in which the crosslinked EPDM particles appeared in the form of agglomerates covered by a layer of nanocomposite PP (NC‐PP). The NC‐TPV samples exhibited higher elastic modulus compared with similar but unfilled TPV sample in spite of the lower crystallization degree for the former. The storage modulus (G′) of the molten NC‐TPV proved to be highly frequency dependent. This was assigned to the formation of a nanoclay network structure by the NC‐PP covered EPDM rubber particles. Copyright © 2006 John Wiley & Sons, Ltd.

Reactive compatibilization of recycled low density polyethylene/butadiene rubber blends during dynamic vulcanization

AbstractFor reactive compatibilization of the recycled LDPE with butadiene rubber (BR) an equal quantity of few couples of reactive polyethylene copolymer/reactive polybutadiene (1/1) were introduced into the corresponding phases before the dynamic vulcanization. The LDPE/BR thermoplastic dynamic vulcanizates (TDVs) produced using the poly(ethylene‐co‐acrylic acid), PE‐AA/polybutadiene terminated with isocyanate groups, PB‐NCO compatibilizing couple with different ratio of functional groups have demonstrated the best mechanical properties and have been characterized by X‐Ray analysis and DMTA measurements. For all of systems studied the increasing components compatibility due to the formation of the essential interface layer have been observed. The PB‐NCO modifier participates in two processes: it is co‐vulcanised with BR in rubber phase and reacts in the interface with the PE‐AA dissolved in LDPE. The amorphous phase of LDPE is dissolved by rubber phase, i.e. the morphology with dual phase continuity is formed that provides an improvement of mechanical characteristics of material obtained. The best combination of mechanical characteristics was obtained for LDPE(PE‐AA)/BR(PB‐NCO), PB‐NCO=7.5 wt.% per PB, COOH/NCO=1/1. The tensile strength and an elongation at break for these blends were 3.9 MPa and 353% and for the basic non‐compatibilized blend 3.2 MPa and 217%, relatively.