Thermoplastic Elastomer Blends Research Articles

Design and properties of a series of high‐temperature thermoplastic elastomeric blends from polyamides and functionalized rubbers

ABSTRACTA series of high‐temperature thermoplastic elastomers (TPEs) and thermoplastic vulcanisates (TPVs) were successfully developed based on two different types of heat resistant polyamide (PA) (25 parts by weight)—PA‐12 and PA‐6, in combination with three different functionalized rubbers (75 parts by weight) of varying polarity, e.g., maleic anhydride grafted ethylene propylene diene terpolymer (MA‐g‐EPDM), sulphonated ethylene propylene diene terpolymer, and carboxylated acrylonitrile butadiene rubber, by melt mixing method. These rubbers have low level of unsaturation in its backbone, and the plastics showed high melting range. Thus, the developed TPEs and TPVs were expected to be high temperature resistant. Resol type resin was used for dynamic vulcanization to further increase the high temperature properties of these blends. Interestingly, initial degradation temperature of the prepared blends was much higher (421 °C for MA‐g‐EPDM/PA‐12) than the other reported conventional TPEs and TPVs. Fourier transform infrared analysis described the interactive nature of the TPEs and TPVs, which is responsible for their superior properties. The maximum tensile strength with lowest tension set was observed for the carboxylated acrylonitrile butadiene rubber/PA‐12 TPV. Mild increase in mechanical properties without any degradation was observed after recycling. Dynamic mechanical analysis results showed two distinct glass transition temperatures and indicated the biphasic morphology of the blends, as evident from the scanning electron microscopy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45353.

Phase-Change Thermoplastic Elastomer Blends for Tunable Shape Memory by Physical Design

Intelligent polymeric materials are of increasing interest in contemporary technologies due to their low cost, light weight, facile processability, and inherent ability to change properties, shape, and/or size upon exposure to an external stimulus. In this study, we consider thermally programmable shape-memory polymers (SMPs), which typically rely on chemistry-specific macromolecules composed of two functional species. An elastic, network-forming component permits stretched polymer chains to return to their relaxed state, and a switching component affords at least one thermal transition to regulate fixation of a desired strain state and return to a previous strain state. Here, we produce designer shape-memory materials by combining thermoplastic elastomeric triblock copolymers with a midblock-selective phase-change additive, thereby yielding shape-memory polymer blends (SMPBs). These materials not only exhibit tunable switch points but also controllable recovery kinetics. We further highlight the versatil...

Mechanical properties of thermoplastic polyester elastomer controlled by blending with poly(butylene terephthalate)

Thermoplastic polyester elastomer (TPEE) blends with poly(butylene terephthalate) (PBT) were prepared by melt compounding for the phase morphology and mechanical property studies. Although PBT is immiscible with the continuous soft poly(tetramethylene glycol) (PTMEG) phase of TPEE, it is miscible with the discrete hard PBT one of TPEE. Therefore, PBT and TPEE are compatible and their blends reveal very low level of interfacial tension and very small size of discrete domains, as well as good interfacial adhesion between two phases, which provide high possibility to prepare TPEE alloys with controllable properties. Mechanical test results reveal that both the modulus and yield and tensile strengths increase with increasing weight ratios of PBT. The increased system rigidity and decreased system plasticity are further confirmed by the cyclic tensile tests. The main objective of this work is to provide useful information on the structure and property control of TPEE by simple mixing with aromatic polyesters.

Solvent Transport Characteristics of Thermoplastic Elastomer Blends Based on Nylon and NBR

Transport characteristics of chlorinated hydrocarbon through Nylon/NBR (Acrylonitrile Butadiene Rubber) blend has been investigated with special reference to the effect of blend ratio, compatibilizer and effect of dynamic crosslinking. An attempt has been made to correlate the diffusion characteristics with morphology of the blend. Fine and uniform distribution of the dispersed domains with a stable morphology were obtained by dynamic vulcanization. Depending on the composition, blends show dispersed/matrix and co-continuous phase morphologies. The various transport parameters such as diffusion coefficient (D), permeation coefficient (P) and sorption coefficients (S) were evaluated at different diffusion conditions such as temperature and percentage of compatibilizer. The equilibrium solvent uptake decreases with an increase in the concentration of NBR in the blends. Finally thermodynamic parameters were evaluated from the diffusion data. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Thermoplastic Elastomeric Blends Based on Waste Tires and Polyethylene: The Role of Rubber Particle Size

Recycling of scrapped tires has become an essential worldwide challenge. The preparation of soft plastics, or thermoplastic elastomers (TPEs), is one of many ways possible for this. Many researchers have prepared TPEs using rubber particles with dimensions 500 μm or more. However, we assume mechanical properties of the TPEs could be improved by using rubber powder with smaller particles. Therefore, we studied the influence of six rubber powder fractions (diameters ranging from 120 to 500 μm) on mechanical properties of TPE samples prepared by blending of ground waste tire rubber (GTR) with low-density polyethylene (PE-LD) in the laboratory mixer (Brabender Plastograph). In addition, two adhesion components were applied: ethylene-propylene-diene rubber (EPDM) and a styrene-ethylene/butylene-styrene copolymer (SEBS). The results of tensile tests suggest that the use of smaller particle sizes, together with the adhesion component, can produce TPEs with improved mechanical properties.

An effective strategy to develop nanostructured morphology and enhanced physico-mechanical properties of PP/EPDM thermoplastic elastomers

The present work reports the preparation of nanostructured thermoplastic elastomeric blends (TPEs and TPVs) based on polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) by a novel processing technique, where well-dispersed nanoscale EPDM particles (~40–100 nm) in the PP matrix were obtained after mixing at 180 °C at 50 s−1 and subsequent micro-injection molding at high melt shear rate (500–700 s−1) at 200 °C. For a precise comparison, conventional microstructured TPEs were also prepared. As a result of nanostructured morphology, significant improvement of various physico-mechanical properties such as tensile strength, modulus, elongation at break, tension set, loss tangent, thermal stability, and crystallinity was achieved for the micro-injection-molded samples. For example, Young’s modulus, the temperature corresponding to the maximum rate of degradation (T max) and crystallinity were 70 MPa, 404 °C, and 18.0 % in the case of the microstructured TPE, which increased to 130 MPa, 418 °C, and 22.5 %, respectively, for the nanostructured TPE. The improved properties of micro-injection-molded samples were analyzed with the help of fine nanoscale morphology of EPDM domains. The influence of micro-injection molding on structure development was predicted from the viscoelastic droplet breakup mechanism and critical capillary number. The results demonstrate a strong effect of melt shearing on the deformation and breakup of the rubber domains and enhancement of physico-mechanical properties of PP/EPDM TPEs, which have a great interest in the industry. This work provides a promising pathway for the design of new TPEs with high-performance for various applications.

Composition-dependent depression of the glass transition temperature of the rubber phase in a PE-SBR blend

AbstractA thermoplastic elastomeric blend was introduced based on high-density polyethylene and styrene-butadiene rubber (SBR). The morphology of the blend system was found to change from two-phase to co-continuous, depending on the polyethylene (PE) concentration. The thermo-mechanical measurements showed that, at the PE concentrations, which seemed to have a co-continuous morphology, the SBR inclusions were very fine. The fineness of the SBR domains resulted in a 20° depression of the glass transition temperature (Tg) of the SBR phase. This was attributed to the smooth interfaces at which the SBR chain sensed a higher free volume as compared with that in bulk SBR. A model correlating thin polymer thickness to the Tg of the confined polymer in the films was employed to correlate SBR domain size to the experimental Tg measured. The adjusting parameters A=129 and δ=1.45 were successfully used to fit the experimental data.

Tailored Nanostructured Thermoplastic Elastomers from Polypropylene and Fluoroelastomer: Morphology and Functional Properties

Conventional thermoplastic elastomer from rubber–plastic blends has rubber domains of a few micrometers dispersed in a plastic matrix. Nanotailoring of novel thermoplastic elastomeric blends from polypropylene (PP) and fluoroelastomer (FKM) by a special green technique generated a unique morphology in which FKM was dispersed in the nanometer range (50–70 nm) into the continuous PP matrix. The evolution of the unique nanostructure morphology was explained with the help of a viscoelastic drop breakup mechanism. The nanostructured blends exhibited superior physical properties and outstanding oil swelling resistance and thermal stability, which increased upon vulcanization of the rubber phase in situ. For example, volume swell of nanostructured PP/FKM blends was 8–10% in ASTM oil #3 at 100 °C for 72 h, which was the lowest in this type of thermoplastic elastomer. Insights into how the unique morphology influenced the functional properties of thermoplastic elastomers was provided. These new thermoplastic elastomers can be used in the automotive industry, particularly as a liner material for car hoses where superior flexibility, oil resistance, and heat resistance are desirable properties.

Crystallization kinetics of thermoplastic elastomeric blends based on ground tyre rubber

ABSTRACTThis work analyzes the crystallization process of thermoplastic elastomeric blends (TPE) based on ground tyre rubber (GTR). More specifically it analyzes the effect of GTR and fresh rubber materials, like ethylene propylene diene monomer (EPDM) and ethylene propylene rubber (EPR), on the crystallization of binary and ternary polypropylene (PP)‐based blends. The crystallization kinetics is studied under isothermal and nonisothermal conditions using differential scanning calorimetry (DSC). The kinetic parameters derived from the Avrami model are used to study the effect of temperature and rubber materials on the nucleation mechanism, the morphology of the crystalline structures, and the crystallization rate. Results reveal that GTR has a strong nucleating effect on PP and that its presence leads to higher crystallization rates. The EPDM presence has a slight effect on the PP crystallization process whereas EPR has no significant effect. From the DSC curves it is possible to detect an inverse relationship between temperature and the crystallization rate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42589.

Nanomechanics and Origin of Rubber Elasticity of Novel Nanostructured Thermoplastic Elastomeric Blends Using Atomic Force Microscopy

PeakForce quantitative nanomechanical mapping is an advanced atomic force microscopy (AFM) technique for measuring the mechanics of a sample surface by probing at the nanoscale. This nanomechanical mapping is performed in novel nanostructured thermoplastic elastomer (TPE) and thermoplastic vulcanizate (TPV) consisting of nanolevel dispersion of fluoroelastomer phase (60–80 nm) in the continuous polyamide matrix. Both in the case of TPE and TPV, elastic modulus and adhesion force (between the tip and sample surface) from the continuous matrix phase to the dispersed rubber particle through the nanometric interface (4–5 nm) are analyzed. The effect of dynamic vulcanization on the nanomechanical properties of the interface and the dispersed rubber phase of the blends is discussed. The origin of rubber elasticity in thermoplastic elastomeric blends in spite of the plastic as the continuous phase is proposed. It was shown for the first time that the interconnected dispersed rubber phase through the thin rubber ligament of 4–12 nm width in the thermoplastic matrix significantly contribute to the rubber elasticity in TPE and TPV. image

Rheological properties of ground tyre rubber based thermoplastic elastomeric blends

This work analyses the rheological behaviour of thermoplastic elastomeric blends (TPE) based on ground tyre rubber (GTR), more specifically the rheological behaviour of binary and ternary polypropylene (PP) based blends with different rubber materials: an ethylene propylene diene monomer (EPDM), an ethylene propylene rubber (EPR) and GTR. The study was developed under steady-shear rate conditions by capillary rheometry at three different temperatures. Time–Temperature Superposition Principle (TTSP) was applied to the viscosity curves using a temperature dependent shift factor, allowing the construction of master curves for the analysed blends. The Cross-WLF model was used to predict the rheological parameters, giving numerical results for viscosity similar to the experimental data. GTR increased the blends viscosity. EPR showed rheological behaviour similar to PP, and EPDM presented higher power law behaviour. Pseudoplastic behaviour was observed for all the analysed blends. Incorporation of GTR in TPE blends for injection moulding purposes was found to be a feasible strategy to upcycle this type of potentially wasted material.

Partial replacement of EPR by GTR in highly flowable PP/EPR blends: Effects on morphology and mechanical properties

ABSTRACTThis research analyzes the effect of ground tire rubber (GTR) and a novel metallocene‐based ethylene–propylene copolymer (EPR), with high propylene content, on the morphology and mechanical behavior of ternary polymer blends based on a highly flowable polypropylene homopolymer (PP). The PP/EPR blends morphology, with very small domains of EPR dispersed in the PP matrix, indicates a good compatibility among these materials, which leads to a significant improvement on elongation at break and impact strength. The incorporation of EPR on the rubber phase of thermoplastic elastomeric blends (TPE) based on GTR and PP (TPEGTR) has a positive effect on their mechanical performance, attributed to the toughness enhancement of the PP matrix and to the establishment of shell‐core morphology between the rubber phases. The mechanical properties of the ternary blends reveal that TPEGTR blends allow the upcycling of this GTR material by injection molding technologies. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42011.

Solvent Transport Properties of Er/Ps Thermoplastic Elastomeric Blends

Novel thermoplastic elastomeric blends from Polystyrene (PS) and Exudated Resin (ER) of Ailanthus Malabaricum tree are prepared by solution casting technique. The applicability of the resulting materials to design and fabricate barrier rubber materials for the transport and storage of liquids and gases has been studied in terms of solvent resistivity. It is important to carry out the transport studies to eliminate diffusion of chemicals into such material products. The sorption and diffusion of benzene through blends of Polystyrene and Exudated Resin of different compositions are studied at 35°C, 55°C and 65°C. The effects of blend ratio on diffusion, sorption and permeation coefficients are determined. The sorption data is used to estimate the activation energies of diffusion and permeation parameters. An anomalous behavior is observed for most of the blend compositions. The blend with 60/40 PS/ER combination at 35°C and 65°C exhibited Fickian transport mechanism. Minimum solvent uptake is observed for the blend ratio 60/40 PS/ER. This blend ratio shows better compatibility between the phases among the series of the blends studied.

Distinct Melt Viscoelastic Properties of Novel Nanostructured and Microstructured Thermoplastic Elastomeric Blends from Polyamide 6 and Fluoroelastomer

Distinct melt viscoelastic properties of novel polyamide 6 (PA6)/fluoroelastomer (FKM) thermoplastic elastomeric blends have been reported with special reference to the micro‐ and nano‐structures. In the entire frequency regime (0.0628–628 rad/s), nanostructured blend (the average dimension of the dispersed rubber phase, D ~ 90 nm) exhibited higher complex viscosity than the microstructured blend (D ~ 0.35 µm). The values of various interfacial parameters such as specific interfacial area per unit volume, interfacial tension, interaction parameter, interfacial thickness and infrared spectroscopic analysis confirmed the existence of more contact surface area between the blend components in nanostructured blend which increased intermolecular interaction. Due to the existence of greater restriction of mobility of the polymer chains, the relaxation time for the nanostructured blend was higher than that of the microstructured blend. The etched extrudate surface morphology was studied using field emission scanning electron microscopy and correlated with viscoelastic response of the blends.

Structure-Property Relationship in Terms of Dynamic Mechanical Properties of High Energy Radiation Treated Industrially Important Thermoplastic Elastomer Blend

A series of low-density polyethylene (LDPE)/ethylene propylene diene terpolymer (EPDM) blends with various compositions have been prepared by melt mixing followed by injection molding. These specimens are irradiated at 40, 80, 120 and 160 kGy electron beam radiation. The gel content increases with increase in EPDM and as well as EB dose. Storage modulus (E’) and loss modulus (E”) are decreased with increase in EPDM content. Storage modulus continues to increase and loss modulus keeps on decreasing with radiation dose. Interestingly, damping property is found to be more for EPDM rich blends, which again decreases upon irradiation. Morphology of fractured surface of LDPE/EPDM shows that with increase in EPDM content, the size and depth of the cavity becomes larger and deeper indicating higher ductility. But, EB crosslinking makes the surface smoother and the smoothness keeps on increasing with increase in dose rendering stiffness to the samples.

Dynamic vulcanization of novel nanostructured polyamide 6/ fluoroelastomer thermoplastic elastomeric blends with special reference to morphology, physical properties and degree of vulcanization

Dynamic vulcanization characteristics of fluoroelastomer during simultaneous mixing with a plastic, polyamide 6, for thermoplastic elastomeric compositions were analyzed in terms of induction time, scorch time, optimum cure and dynamic cure rate for the first time to understand their processing behavior. Also, a new derivative torque vs. time plot was proposed to gain insight into dynamic curing behavior of the rubber. Evolution of morphology and properties during different stages of mixing and dynamic vulcanization was captured. Size of the dispersed rubber phase decreased from ∼450 to ∼130 nm with increasing degree of cure and mixing time. Interestingly, it was revealed for the first time the role of injection molding in transforming the morphology and hence properties of such vulcanizates drastically. Nanometer-sized rubber particles (60–80 nm) were generated in thermoplastic vulcanizates (TPVs) after injection molding, which were clearly reflected from field emission scanning electron microscopy and atomic force microscopy and also theoretically predicted from the critical breakup law of viscoelastic droplets in a matrix. Significant improvement of tensile properties was recorded during dynamic vulcanization and also after injection molding of the samples. Tensile strength and Young's modulus of a TPV were 34.5 MPa and 200 MPa respectively as compared to 26.5 MPa and 92 MPa for the specimen before injection molding.

Preparation, Morphology and Properties of Poly(Trimethylene Terephthalate)/Thermoplastic Polyester Elastomer Blends

Poly(trimethylene terephthalate)(PTT)/thermoplastic polyester elastomer (TPEE) blends were prepared and their miscibility, crystallization and melting behaviors, phase morphology, dynamic mechanical behavior, rheology behavior, spherulites morphology, and mechanical properties were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), parallel-plate rotational rheometry, polarized optical microscopy (POM), wide angle X-ray diffraction (WAXD), universal tensile tester and impact tester, respectively. The results suggested that PTT and TPEE were partially miscible in the amorphous state, the TPEE rich phase was dispersed uniformly in the solid matrix with a size smaller than 2 μm, and the glass transition temperatures of the blends decreased with increasing TPEE content. The TPEE component had a good effect on toughening the PTT without depressing the tensile strength. The blends had improved melt viscosities for processing. When the blends crystallized from the melt state, the onset crystallization temperature decreased, but they had a faster crystallization rate at low temperatures. All the blends’ melts exhibited a predominantly viscous behavior rather than an elastic behavior, but the melt elasticity increased with increasing TPEE content. When the blends crystallized from the melt, the PTT component could form spherulites but their morphology was imperfect with a small size. The blends had larger storage moduli at low temperatures than that of pure PTT.

Investigation on the thermal and crystallization behavior of high density polyethylene/acrylonitrile butadiene rubber blends and their composites

The properties of a blend containing a crystallizable component depend largely on the extent of crystallinity and the crystallization behavior of that component in presence of the other. Here, the semi crystalline high density polyethylene (HDPE) is blended with the amorphous elastomer, acrylonitrile butadiene rubber (nitrile rubber or NBR) and we focus mainly on the crystallinity of HDPE/NBR immiscible blends and its variation in the presence of compatibilizer and filler. The effect of blend ratio, compatibilizer concentration, dynamic vulcanization, and filler incorporation were carefully evaluated from the crystallinity measurements using differential scanning calorimeter and the basic aim of this work lies in tuning these conditions. This study allows the elucidation of the influence of crosslink density in regulating the crystallinity of thermoplastic elastomer blends. The scanning electron micrographs provide blend morphology from which the reduced domain size and the influence of NBR particles as heterogeneous nuclei for crystallization are evidenced especially at 5% compatibilizer concentration. The crystallinity of blends was observed to be high at 30 phr carbon black filler addition. Finally, the thermal stability of blends and their composites are also addressed and correlated with the crystallization effect. POLYM. ENG. SCI., 55:1203–1210, 2015. © 2014 Society of Plastics Engineers

Stress–Strain and Diffusion Behavior of Industrial Waste-filled Acrylonitrile–Butadiene Rubber/High Density Polyethylene Blends

Abstract The mechanical properties and diffusion behavior of marble waste (MW)-filled acrylonitrile–butadiene rubber (NBR)/high density polyethylene (HDPE) blends were studied as a function of blend composition. A sulfur curing system was employed to crosslink the thermoplastic elastomer (TPE) blends. The results obtained showed that the physical properties of vulcanized NBR/HDPE blends were enhanced with the addition of HDPE in MW-filled vulcanized NBR/HDPE blends. Mechanical properties such as stress–strain behavior, tensile strength, modulus, and % elongation at break and tear strength, were assessed and found to fluctuate with the blend ratio. HDPE-incorporated vulcanized NBR/HDPE blends have been found to reveal a reduced toluene uptake trend compare to the NBR compound.

Mechanical Properties and Morphology of ER/PS Blends

Thermoplastic elastomeric blends of Polystyrene (PS) and Exudated Resin (ER) with different compositions have been prepared by solution casting method. The mechanical performance of this system has been studied in detail. Stress-stain behavior, tensile strength, elongation at break and young’s modulus was determined. The effect of blend ratio on the mechanical properties and surface hardness has been analyzed. By the addition of ER reduces the plasticity of polystyrene. The blend with 60/40 PS/ER combination exhibited comparatively better mechanical properties. 60/40 PS/ER blend ratio shows higher compatibility between the phases among the series of the blends studied. It is explained on the basis of the morphology of the blend. Various theoretical models such as series, Parallel and Halpin-Tsai have been used to fit the experimental mechanical data. Scanning Electron Microscopy was employed to analyze the surface morphology of the blend.