Dynamic vulcanization of polyethylene-based thermoplastic elastomer blends (original) (raw)
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Polymer Engineering and Science, 2007
Dynamically vulcanized blends of polyoxymethylene (POM) and ethylene propylene diene terpolymer (EPDM) with and without compatibilizer were prepared by melt mixing in a twin screw extruder. Maleic anhydride (MAH) grafted EPDM (EPDM-g-MAH) has been used as a compatibilizer. Dicumyl peroxide was used for vulcanizing the elastomer phase in the blends. Mechanical, dynamical mechanical, thermal, and morphological properties of the blend systems have been investigated as a function of blend composition and compatibilizer content. The impact strength of both dynamically vulcanized blends and compatibilized/dynamically vulcanized blends increases with increase in elastomer content with decrease in tensile strength. Dynamic mechanical analysis shows decrease in tanδ values as the elastomer and compatibilizer content increased. Thermograms obtained from differential scanning calorimetric studies reveal that compatibilized blends have lower Tm values compared to dynamically vulcanized blends, which confirms strong interaction between the plastic and elastomer phase. Scanning electron microscopic observations on impact fractured surface indicate reduction in particle size of elastomer phase and its high level of dispersion in the POM matrix. In the case of compatibilized blends high degree of interaction between the component polymers has been observed. POLYM. ENG. SCI., 47:934–942, 2007. © 2007 Society of Plastics Engineers
Dynamic Vulcanized Thermoplastic Elastomers Based on Ethylene-Propylene Terpolymer and Polyethylene
The paper presents the studies on the obtaining and characterization of new types of dynamically vulcanized thermoplastic elastomers based on ethylene-propylene terpolymer rubber and polyethylene. As a vulcanizing agent, a phenolic resin (0-15 parts per 100 parts rubber) was used in the presence of dehydrated stannous chloride. Mixtures were obtained by the dynamic vulcanization technique in a Plasti-Corder Brabender mixer at 80 rpm and a temperature of 170°C. Analyzing variations of physical-mechanical characteristics depending on the amount of resin introduced into the blends, it was observed that 100% modulus, tensile strength, and tear strength increased to an optimal point after which they tended to decrease. By dynamically crosslinking the elastomer in the thermoplastic polymer melt there was a significant improvement in the resistance to repeated flexures, behavior to permanent deformation at compression, and resistance to the action of toluene. New materials can be used in various fields such as: the footwear industry (soles, heels and plates), protection equipment, obtaining gaskets, hoses, technical rubber products for cars, etc.
Journal of Applied Polymer Science, 2008
Dynamic vulcanization was used to prepare thermoplastic elastomer blends of nylon (polyamide), polypropylene (PP) and polybutylene terephthalate thermoplastics with chlorobutyl (CIIR) and nitrile (NBR) rubbers. Mechanical properties of the blends were correlated against composition. Although hardness and tensile strength increase with increasing thermoplastic content for all blends, elongation at break values initially decrease and then increase in the range of 20–40% thermoplastic. For various blend compositions, the swelling behavior was evaluated with solvents that are able to dissolve the uncured rubber portion but not the thermoplastic component of the mixtures. All five systems showed swelling index values that were substantially less than the calculated “theoretical” values of swelling index. This was attributed to a caging effect of the thermoplastic component on the rubber phase, which restricts access of solvent and swelling of the rubber phase. In turn, this affects the solvent resistance of the blend. Some of the blends were evaluated by differential scanning calorimetry to assess the compatibility of the components in the blend. scanning electron microscopy was also used to determine the degree of compatibility of the two phases generated in the mixing process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Journal of Applied Polymer Science, 2008
Epoxidized natural rubber (ENR) with a level of epoxide groups of 20 mol % was prepared via the performic epoxidation method. It was then used to blend with high-density polyethylene (HDPE) at various blend ratios. Three types of blend compatibilizers were prepared. These included a graft copolymer of HDPE and maleic anhydride (MA; i.e., HDPE-g-MA) and two types of phenolic modified HDPEs using phenolic resins SP-1045 and HRJ-10518 (i.e., PhSP-PE and PhHRJ-PE), respectively. We found that the blend with compatibilizer exhibited superior tensile strength, hardness, and set properties to that of the blend without compatibilizer. The ENR and HDPE interaction via the link of compatibilizer molecules was the polar functional groups of the compatibilizer with the oxirane groups in the ENR molecules. Also, another end of the compatibilizer molecules (i.e., HDPE segments) was compatibilizing with the HDPE molecules in the blend components. The blend with compatibilizer also showed smaller phase morphology than the blend without compatibilizer. Among the three types of the blend compatibilizer, HDPE-g-MA provided the blend with the greatest strength and hardness properties but the lowest set properties.
Journal of Applied Polymer Science, 2003
The effects of the blend ratio, reactive compatibilization, and dynamic vulcanization on the dynamic mechanical properties of high-density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends have been analyzed at different temperatures. The storage modulus of the blend decreases with an increase in the EVA content. The loss factor curve shows two peaks, corresponding to the transitions of HDPE and EVA, indicating the incompatibility of the blend system. Attempts have been made to correlate the observed viscoelastic properties of the blends with the blend morphology. Various composite models have been used to predict the dynamic mechanical data. The experimental values are close to those of the Halpin–Tsai model above 50 wt % EVA and close to those of the Coran model up to 50 wt % EVA in the blend. For the Takayanagi model, the theoretical value is in good agreement with the experimental value for a 70/30 HDPE/EVA blend. The area under the loss modulus/temperature curve (LA) has been analyzed with the integration method from the experimental curve and has been compared with that obtained from group contribution analysis. The LA values calculated with group contribution analysis are lower than those calculated with the integration method. The addition of a maleic-modified polyethylene compatibilizer increases the storage modulus, loss modulus, and loss factor values of the system, and this is due to the finer dispersion of the EVA domains in the HDPE matrix upon compatibilization. For 70/30 and 50/50 blends, the addition of a maleic-modified polyethylene compatibilizer shifts the relaxation temperature of both HDPE and EVA to a lower temperature, and this indicates increased interdiffusion of the two phases at the interface upon compatibilization. However, for a 30/70 HDPE/EVA blend, the addition of a compatibilizer does not change the relaxation temperature, and this may be due to the cocontinuous morphology of the blends. The dynamic vulcanization of the EVA phase with dicumyl peroxide results in an increase in both the storage and loss moduli of the blends. A significant increase in the relaxation temperature of EVA and a broadening of the relaxation peaks occur during dynamic vulcanization, and this indicates the increased interaction between the two phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2083–2099, 2003
A novel thermoplastic elastomer based on dynamically vulcanized polypropylene/acrylic rubber blends
2008
Thermoplastic elastomer based on polypropylene (PP) and acrylic rubber (ACM) was investigated, with special attention on the compatibilization and dynamic vulcanization. ACM component contains chlorine and carboxyl groups along the backbone, which act as center for the curing and reactive compatibilization. The last event was carried out by adding a combination of maleic anhydride-modified PP (PP-g-MA) and triethylene tetramine (TETA), which act as interfacial agents between PP and ACM phases. The effectiveness of the compatibilization was suggested from mixing torque and viscosity, determined from rheological measurements. Outstanding mechanical performance, especially elongation at break, and better tensile set (lower values) were obtained with the compatibilization. The dynamic vulcanization also resulted in good mechanical properties for compatibilized blends, but the performance was inferior to that observed for non vulcanized blends. The effect of the compatibilization and/or dynamic vulcanization on the dynamic mechanical, thermal, morphological and stress relaxation properties was investigated.
Journal of Applied Polymer Science, 2004
Attempts were made to prepare dynamically crosslinked ethylene-propylene-diene monomer/polypropylene (EPDM/PP, 60/40 w/w) blends loaded with various amounts of silica as a particulate reinforcing agent. The dispersion of silica between the two phases under mixing conditions, and also extent of interaction, as the two main factors that influence the blend morphology were studied by scanning electron microscopy. Increasing the silica concentration led to the formation of large-size EPDM aggregates shelled by a layer of PP. Dynamic mechanical thermal analysis performed on the dynamically cured silica-loaded blend samples showed reduction in damping behavior with increasing silica content. Higher rubbery-like characteristics under tensile load were exhibited by the silica-filled EPDM/ PP-cured blends. However, increasing the silica level to 50 phr led to the enhancement of interface, evidenced by increases in the tensile modulus and extensibility of the blend compared with those of the unloaded sample. Addition of a silane coupling agent (Si69) into the mix improved the mechanical properties of the blend, attributed to the strengthening of interfacial adhesion between the PP matrix and silica-filled EPDM phase.
Journal of Elastomers and Plastics, 2010
In this study, mixtures of low-density polyethylene (LDPE) and the recycled elastomeric terpolymer ethylene-propylene-diene (EPDM-r) were obtained. The EPDM-r was incorporated as obtained by the manufacturer (vulcanized) and also after being submitted to a devulcanization process using microwaves. The mixtures were obtained with the use of bis(a, a-dimethylbenzyl) peroxide. The elastomeric residue was characterized by gel content and scanning electron microscopy, before and after the devulcanization process. The mixtures obtained were characterized by thermogravimetric analysis, differential scanning calorimetry, and mechanical tests for resistance to traction and impact. The results of the analysis of the residues showed that the devulcanization process reduced significantly the gel content of the elastomer. The mixtures obtained demonstrated that the incorporation of vulcanized EPDM-r reduced the crystallization and fusion enthalpies, while conserving the crystallization and fusion characteristics of the thermoplastic. The mixtures showed a reduction in the deformation and traction strength; however, the incorporation of devulcanized EPDM-r led to a significant increase in the elasticity modulus values and the resistance to impact in relation to the pure LDPE.
Polymer …, 2004
Recycled low density polyethylene (R-LDPE) has been reactively compatibilized with butadiene rubber (BR) by using small additions of reactive polyethylene copolymers and reactive BRs to produce thermoplastic elastomers (TPEs). TPEs were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), rheology measurements, wide-angle X-ray scattering (WAXS) and mechanical testing. WAXS results show that the presence of BR and reactive modifiers does not completely prevent the crystallization of R-LDPE during the TPE formation. Depression of the melting point has been found in all cases. Also in all cases, compatibility is provided by formation of interfacial layers. The best mechanical characteristics are obtained for R-LDPE + BR blends compatibilized with poly(ethylene-co-acrylic acid) (PE-co-AA) and polybutadiene terminated with isocyanate groups (PB-NCO) for PB-NCO = 7.5 wt% per PB and COOH/NCO ratio = 1/1. The stress at break and elongation at break are respectively improved by 31 % and 63 %. The PB-NCO modifier participates in co-vulcanization with BR in the rubber phase and reacts at the interface with the PE-co-AA dissolved in the polyolefin phase. As a result, the amorphous phase of R-LDPE is dissolved by the rubber phase and a morphology with dual phase continuity is formed, assuring an improvement of mechanical properties of TPEs.