Dynamic Vulcanization Research Articles

Reactively compatibilized and dynamically vulcanized thermoplastic elastomers based on high-density polyethylene and reclaimed rubber

Melt blending was employed to prepare thermoplastic elastomer (TPE) of reclaimed rubber (RR) and high density polyethylene (HDPE). Mechanical properties of TPE samples were improved in different methods including dynamic vulcanization and reactive blending (reactive compatibilization) during melt mixing in an internal Haake mixer. The physical and mechanical properties of the TPE blends were investigated by the dynamic mechanical analysis (DMA) and tensile tests. The thermal behavior was characterized by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The phase morphology of the blends was studied by scanning electron microscopy (SEM). Experimental results showed that, both static and dynamic mechanical properties of reactively-compatibilized and dynamically-vulcanized samples improved significantly compared with the virgin samples. The effect of dynamic-vulcanization and reactivecompatibilization on the mechanical properties revealed that the Young’s modulus and storage modulus increased with both improvement methods. SEM results showed that, dynamic-vulcanization and reactivecompatibilization methods improved the distribution of RR particles in HDPE matrix. Although both methods improved the thermal and mechanical properties of the HDPE/RR blends, dynamic-vulcanization was more effective and promising approach due to the higher properties of HDPE/RR blends prepared by this method.

Thermal Tensile, and Dynamic Mechanical Properties of PVDF/FKM Blends in Different Curing Systems

Blends of poly(vinylidene fluoride) (PVDF) and fluororubber (FKM) were prepared in an internal mixer by dynamic vulcanization. The effect of FKM, with and without curing system, was studied with respect to the properties of the PVDF/FKM blends. The tensile test showed that the tensile strength and modulus decreased after blending but the elongation-at-break naturally increased because of the presence of rubber in PVDF matrix. The differential scanning calorimetry (DSC) test gave good indications of improved state of miscibility in most blend ratios. The increase of FKM content showed a favorable tendency of PVDF component toward crystallization. The incorporation of FKM as a coblend improved the thermal stability of PVDF, and the temperature at 10% weight loss of the blends increased. This was confirmed by one value of glass transition temperature obtained from DMTA test, which indicated two different values for pure polymers. The rheological tests showed that the complex viscosity and storage modulus of the blends increased with increasing frequency.

Optimization of Electrical Conductivity, Dielectric Properties, and Stress Relaxation Behavior of Conductive Thermoplastic Vulcanizates Based on ENR/COPA Blends by Adjusting Mixing Method and Ionic Liquid Loading

Conductive thermoplastic vulcanizates based on epoxidized natural rubber (ENR) and copolyamide (COPA) blends were prepared using two alternative mixing stages to incorporate MWCNTs: after or before dynamic vulcanization (i.e., ADV or BDV, respectively). Effects of ionic liquid (IL) loading on properties of the blends were also studied. The results indicated that both ADV and BDV mixing preferentially localized MWCNTs in the COPA phase. However, with BDV mixing some of the MWCNTs also resided in ENR domains. The TPVs made with BDV showed higher electrical conductivity, dielectric properties, and superior stress relaxation behavior relative to those prepared by ADV. This might be due to better dispersion of MWCNTs in both phases of the blends. In addition, the electrical and dielectric properties were improved by the IL in a dose dependent manner with the IL loading. However, the IL reduced stress relaxation of the TPVs due to its plasticizing effect.

The modification of EPDM with trimethoxysilyl-modified polybutadiene

Trimethoxysilyl poly-1,2-butadiene (TMSPBD) is used with considerable frequency in the rubber industry. In this study, the effect of TMSPBD modification of an EPDM matrix is studied in detail and the changes in thermal, mechanical and rheological properties and kinetics of vulcanization are reported. The results show that the mechanical properties and thermal stability are improved. It is also seen that the amount of the TMSPBD is important for the degree of modification to be obtained within the polymeric matrix.

Toughening polylactide by dynamic vulcanization with castor oil and different types of diisocyanates

Dynamic vulcanization of polylactide (PLA) with castor oil (CO) and three different diisocyanates, namely 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), was performed to study the effect of diisocyanate type on the vulcanization process and on the morphology as well as mechanical properties of the PLA/CO-based polyurethane blends. The reactivity of the three diisocyanate followed the order of MDI > HDI > IPDI when reacting with castor oil. Interfacial compatibilization between PLA and the CO-based polyurethane occurred when the less reactive HDI and IPDI was used. Among all the blends, PLA/CO-IPDI showed the finest morphology and the best toughening efficiency. Incorporation of 20 wt% CO-IPDI increased the elongation at break and notched impact strength of PLA by 47.3 and 6.6 times, respectively. Cavitation induced matrix plastic deformation was observed as the toughening mechanism for the PLA blends with CO-based polyurethane. The effect of CO-IPDI content on the morphology and mechanical properties of PLA was studied in detail. The particle size of dispersed CO-IPDI and the elongation at break increased gradually, the tensile strength and Young's modulus decreased gradually, while the impact strength first increased and then decreased with increasing CO-IPDI content from 5 to 30 wt%. The maximum impact strength appeared for the blends with 20 wt% CO-IPDI.

Improving properties of natural rubber/polyamide 12 blends through grafting of diacetone acrylamide functional group

The aim of the present study was to improve the compatibility in blends of natural rubber (NR) and polyamide 12 (PA12) by grafting NR with hydrophilic monomer, diacetone acrylamide (DAAM), via seeded emulsion polymerization. The increase in polarity of NR after grafting modification was confirmed by a considerable increase in the polar component of its surface energy. Blends of graft copolymers of NR and poly(diacetone acrylamide) prepared using 10 wt% of DAAM (NR-g-PDAAM10) and PA12 were prepared at a 60/40 blend ratio (wt%) using simple blend and dynamic vulcanization techniques. The mechanical and rheological properties of the resulting blends were subsequently investigated and compared with those of the corresponding blends based on unmodified NR. The results show that dynamic vulcanization led to a significant increase in both mechanical and rheological properties of the blends. It was also observed that the dynamically cured NR-g-PDAAM10/PA12 blend had smaller particle size of vulcanized rubber dispersed in the PA12 matrix than observed for the dynamically cured NR/PA12 blend. This is due to the compatibilizing effect of DAAM groups present in NR-g-PDAAM10 molecule, which decreases the interfacial tension between the two polymeric phases. Therefore, it can be stated that the interfacial adhesion between NR and PA12 was improved by the presence of DAAM groups in NR molecule. This was reflected in the higher tensile properties observed in the dynamically cured NR-g-PDAAM10/PA12 blend. Copyright © 2017 John Wiley & Sons, Ltd.

Fracture toughness and deformation mechanism of un-vulcanized and dynamically vulcanized polypropylene/ethylene propylene diene monomer/graphene nanocomposites

Polypropylene (PP)/Ethylene propylene diene monomer (EPDM)/graphene nanocomposites were prepared by melt mixing process via an internal mixer (Brabender plasti-corder). The effect of multi-layer graphene (MLG), few-layer graphene (FLG) and dynamic vulcanization on microstructure and fracture toughness of the multicomponent system were investigated. The morphology of the samples were characterized by wide X-ray diffraction (WAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which revealed that graphene mostly was dispersed into the PP phase and the size of the dispersed phase (EPDM) was decreased with incorporation of graphene, more specifically FLG, in both un-vulcanized and vulcanized systems. The concept of essential work of fracture (EWF) was used to analyze the fracture toughening behavior and deformation mechanism of PP/EPDM/graphene nanocomposites. In the case of un-vulcanized polymer, the total work of fracture improvements (+23.5%) was noted for PP/EPDM/FLG in which FLG platelets with higher aspect ratio were used, showed the better dispersion and higher ductility fracture behavior compared with MLG. The fracture mechanism of un-vulcanized samples occurs due to debonding and/or cavitation of the dispersed phase (EPDM), while for vulcanized samples the fracture mechanism proceeds through creation of nanovoids and cavitation in the dispersed phase which lead to the shear yielding of PP matrix. The graphene platelets acted as crack initiation sites as well as obstacles against crack propagation. The results of microstructure properties along with the fracture analysis data showed that the aggregated MLG platelets act as stress concentration and facilitate the initiate cracks while the FLG platelets hindered the crack path. Improvement in toughness behavior and matrix resistance were attributed to higher voiding stresses and finer dispersion of graphene.

High Performance and Thermal Processable Dicarboxylic Acid Cured Epoxidized Plant Oil Resins through Dynamic Vulcanization with Poly(lactic acid)

Dicarboxylic acid (DA) cured expoxidized soybean oil (ESO) resins are nonprocessable and usually exhibit low mechanical performance, which significantly restrict the application of these sustainable materials. In this study, we report a facile and efficient way of endowing these thermosetting ESO resins with high performance and thermoplasticity via dynamic vulcanization of ESO with sebacic acid (SA) and poly(lactic acid) (PLA). A phase-separated morphology with vulcanized ESO resin (VESO) dispersed in PLA matrix was formed for the dynamically vulcanized blends even with the content of VESO as high as 80 wt %. Rheological analysis indicated that the obtained VESO/PLA blends showed good melt processability as evidenced by the low complex viscosity at high frequency range. The blend contained 80 wt % cross-linked VESO could also be injection molded. The tensile strength and Young’s modulus of VESO were improved by ∼11 and ∼16 times after incorporation of only 20 wt % PLA and could be further increased by ∼39 and ∼103 times with increasing PLA’s content to 50 wt %. Furthermore, the VESO/PLA blends showed high toughness with large tensile strains although both VESO and PLA showed brittle characters. With excellent mechanical properties and thermal processability, the dynamically vulcanized ESO resins would find wider potential applications than the low performance and thermosetting ESO resins.

Sustainable biobased blends of poly(lactic acid) (PLA) and poly(glycerol succinate-co-maleate) (PGSMA) with balanced performance prepared by dynamic vulcanization

A sustainable and industrially viable method for toughening poly(lactic acid) by dynamic vulcanization using glycerol and succinic acid based polyesters.

Unique microstructure of an oil resistant nitrile butadiene rubber/polypropylene dynamically vulcanized thermoplastic elastomer

This paper reports on the microstructure, morphological evolution and the properties of oil resistant nitrile butadiene rubber (NBR)/polypropylene (PP) thermoplastic vulcanizates (TPVs) prepared by dynamical vulcanization (DV).

動的粘弾性による新しい架橋型熱可塑性エラストマーの評価方法の検討

Thermoplastic elastomer (TPE) produced by dynamic vulcanization which is one of the reactive processing is generally called thermoplastic vulcanization (TPV). It is considered that, in the mixing process of TPV, the crosslink reaction and the EPDM dispersion in PP proceeds simultaneously. Therefore, the phase structure of TPV is complex and it is very difficult to analyze the kneading states. Since the slight difference of kneading states is known to lead to the large differences in the physical properties such as the extrusion processability and the surface appearance of the products, the conventional and exact testing methods to estimate TPV kneading state is required at TPV mixing plant. It was found that an apparent activation energy (Ea) calculated from the temperature dependence of dynamic viscosity modulus is an effective index for measuring the degree of crosslink. Also the degree of EPDM dispersion was quantified by dynamic elasticity modulus change ratio (Gr) between G* at the strain of 20% and 1%. These indices can be calculated simply and easily from dynamic viscoelastic results and can be applied to estimate the kneading state of the TPV compound.

Property improvements of natural rubber and low density polyethylene blends through dynamic vulcanization

Polymer blends are prepared by melt mixing, solution or latex blending. Thermoplastic vulcanizates (TPVs) are generally produced by melt mixing. TPVs can be co-injected or co-extruded to produce complex articles built from very soft/hard components. Dynamic vulcanization would give rise to a uniform and fine distribution of rubber and thermoplastic phases. The aim of this study was to identify a suitable dynamic vulcanization system to produce natural rubber (NR)/low-density polyethylene (LDPE) blends with improved chemical, ageing and morphological properties. Three 50:50 NR/LDPE blends were prepared by varying the vulcanizing agent as sulphur, dicumyl peroxide (DCP) and 50:50 sulphur: DCP. A control was prepared without any vulcanizing agent. All these blends were prepared by melt mixing. The blends were characterized using FTIR spectroscopy and SEM analysis of tensile fracture surfaces. Water absorption, swelling and ageing behaviour of the blends were investigated. Water absorption percentage of blends prepared with DCP and the mixed curing system was zero. Analysis of gel content indicated a higher crosslink density for the blend prepared with the mixed curing system compared to the other blends. Also, the former blend showed the highest retention of strength properties and elongation at break compared to the other two blends prepared with vulcanizing agents. SEM analysis showed a fine and smooth textured morphology for this blend. Results in overall indicated that the 50:50 NR/LDPE blend prepared with the mixed curing system would be suitable to manufacture heat and solvent resistant products.

Dynamically cured poly(vinylidene fluoride)/epoxidized natural rubber blends filled with ferroelectric ceramic barium titanate

Ceramic-polymer composites based on dynamically cured blends of poly(vinylidene fluoride) and epoxidized natural rubber (PVDF/ENR TPVs) with barium titanate (BT) filler were prepared. The main aim was to develop new polymeric materials with high dielectric permittivity and mechanical properties. Two alternative mixing methods were exploited by addition of BT particles before (BDV) or after (ADV) dynamic vulcanization. The ADV method limited the migration of BT into the higher viscosity vulcanized ENR phase. The interfacial localization of BT with the ADV method might make it act as a compatibilizer and improve stress transfer between the two phases. Furthermore, the storage modulus of the composites increased with BT loading. Also, those dynamically cured PVDF/ENR blends with higher PVDF contents had higher permittivities and reduced loss factors. Furthermore, the incorporation of BT particles in PVDF/ENR TPVs produced materials with excellent mechanical and dielectric properties, such that might be applied in energy storage devices.

Preparation, morphology and superior performances of biobased thermoplastic elastomer by in situ dynamical vulcanization for 3D-printed materials

3D-printing of polymers provides the opportunity to fabricate materials into customized sizes and shapes. The present study describes fully renewable thermoplastic vulcanizates (TPVs) consisting of synthesized biobased elastomer (PLBSI) and poly (lactic acid) (PLA) by in situ dynamic vulcanization for 3D-printed materials. The morphology study implied in situ dynamic vulcanization and phase inversion occurs and leads the PLBSI elastomer dispersed as microparticles in PLA matrix. Then, the morphological evolution mechanism was proposed and indicated the dispersed PLBSI elastomer microparticles are actually agglomerates of elastomer nanoparticles. The PLBSI/PLA TPVs perform good processability and reprocessability by rheological and recyclability tests. Besides, good in vitro degradability and cytotoxicity suggests PLBSI/PLA TPVs are promising sustainable biomaterials. The superior strength and elasticity confirmed by the tensile tests of 3D-printed samples, and firm microstructure and the reliable printed accuracy of 3D-printed samples investigated by SEM implied the PLBSI/PLA TPVs were ideal 3D-printing materials.

Super-tough Poly(lactide) Thermoplastic Vulcanizates Based on Modified Natural Rubber

In order to take advantage of the sustainability and environmental friendliness of a biobased poly(lactide) (PLA), it was used with natural rubber graft-modified glycidyl methacrylate (NR-GMA), via bulk free radical polymerization, to produce a new thermoplastic vulcanizate (TPV) by in situ dynamical vulcanization. The well-dispersed super-tough PLA-based thermoplastic vulcanizate with 20 wt % NR-GMA exhibited a greatly improved notched impact strength of 73.4 kJ/m2 and elongation yield of 136%, which represented a 26- and 33-fold increase, respectively, compared to neat PLA. Interfacial reactive compatibilization between the PLA matrix and NR-GMA phase was confirmed by Fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical analysis (DMA) and differential scanning (DSC) measurements. This strong interfacial interaction, in combination with a fine microscale and nanoscale dispersed phase structure, were responsible for the high toughness of PLA/NR-GMA TPV. These new PLA-based vulcanizates h...

РАЗРАБОТКА ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ НА ОСНОВЕ ТЕРМОПЛАСТИЧНЫХ ЭЛАСТОМЕРОВ

This paper presents data on the development of polymer composite materials based on thermoplastic elastomers. As starting materials for the synthesis of the matrix components were selected as follows: isotactic polypropylene and ternary ethylene-propylene-diene elastomer (EPDM). Diene component in EPDM are ethylidene norbornene composition in an amount of 4-5%. Dynamic vulcanization was carried out using the elastomer element sulfur. The filler polymer composite materials used silica gel with dimethyl polysiloxane. Synthesis was carried out by filling the sol-gel technology. The filler content in the composite varied from 10 to 80% by weight. Mixing of filler and the matrix was performed in a laboratory twin-rotor mixer, type "Brabender". It is found that the maximum possible filler content of the matrix used was 80%. With the introduction of more filler mixing of the components it has been difficult. When the filler content from 10 to 70% of parameters such as tensile strength, flexural strength and modulus of longitudinal elasticity increasing and administered at higher filler and 80 wt%. markedly reduced. Thus, it can be concluded that the content of filler in the composite is 70%. Further research should be directed to the evaluation of the radiation resistance of the developed composite materials.

Superior heat-resistant and oil-resistant blends based on dynamically vulcanized hydrogenated acrylonitrile butadiene rubber and polyamide 12

High-performance thermoplastic vulcanizates (TPVs) are the new generation of TPVs that provide superior heat and oil aging behavior. TPVs based on hydrogenated acrylonitrile butadiene rubber and polyamide 12 (PA12) have been first developed by the dynamic vulcanization process, in which selective cross-linking of the elastomer phase during melt mixing with the thermoplastic phase (PA12) was carried out simultaneously. In this present investigation, hydrogenated acrylonitrile butadiene rubber (HNBR)/PA12 and partially hydrogenated carboxylated acrylonitrile butadiene rubber (XHNBR)/PA12 with blend ratio of 50:50, 60:40, and 70:30 wt% were prepared at 185°C at a rotor speed of 80 rpm for 5 min. Di-(2-tert-butyl peroxy isopropyl) benzene was chosen as the suitable cross-linking peroxide to pursue the dynamic vulcanization. TPV based on 50:50 HNBR/PA12 and XHNBR/PA12 show better physico-mechanical properties, rheological behavior, thermal stability, dynamic mechanical analysis, and creep behavior among all the TPVs. Morphology study reveals that dispersed phase morphology has been formed with an average dimension of the rubber particles in the range of 0.8–1.5 µm. For aging test, TPVs were exposed to air and ASTM oil 3, respectively. Air aging tests were carried out in hot air oven for 72 hr at 125°C, while the oil aging tests were carried out after immersion of the samples into the oils in an aging oven. After aging, there is only slight deterioration in the physico-mechanical properties of the TPVs. In case of 50:50 blends of HNBR/PA12 and XHNBR/PA12, the retention of the properties upon after aging was found excellent. These TPVs are designed to find potential application in automotive sector especially for under-hood-application, where high-temperature resistance as well as high oil resistance is of prime importance. Copyright © 2016 John Wiley & Sons, Ltd.

Carbon black reinforced thermoplastic vulcanisates based on ethylene–vinyl acetate copolymer/styrene–butadiene rubber blends

Thermoplastic vulcanisates (TPVs) based on ethylene–vinyl acetate copolymer (EVA)/styrene–butadiene rubber (SBR) blends were prepared by dynamic vulcanisation, with the TPVs being reinforced by carbon black (CB). Experimental results indicated that the mechanical properties of dynamically vulcanised EVA/SBR blends were enhanced remarkably by the incorporation of CB. Morphology study showed that the SBR particles with average diameter of 20 μm were dispersed evenly on the etched surface of EVA/SBR/CB TPVs. The Mullins effect could be observed in the stress–strain curves of EVA/SBR TPVs and EVA/SBR/CB TPVs during the uniaxial loading–unloading cycles. Compared with EVA/SBR TPVs, CB reinforced EVA/SBR TPVs had the relatively higher stress, residual deformation and internal friction loss.

Retraction Note to: Effect of dynamic cross-linking on melt rheological properties of isotactic polypropylene (iPP)/ethylene–propylene diene rubber (EPDM)/nitrile rubber (NBR) elastomeric blends

An attempt has been made to study the melt rheological properties of uncross-linked and dynamically cross-linked isotactic polypropylene (iPP)/ethylene-propylene-diene rubber (EPDM)/Nitrile rubber (NBR) elastomeric blends, at blending ratios 10–40 wt.%, EPDM/NBR are reported. Blends were prepared by melt blending in an internal mixture at 190 °C and various rheological parameters have been evaluated at 220 °C by single screw capillary rheometer. Cross-linking was performed with resole type dimethylol phenolic resin. The effects of (i) blends composition (ii) shear stress/shear rate on melt viscosity (iii) flow characteristics and shear sensitivity at processing (iv) melt elasticity of the extrudate and (v) dynamic vulcanization effect on the processing characteristics were studied. It was found that the melt viscosity increases with the increasing EPDM/NBR concentration and decrease with increasing intensity of the shear mixing of all the blend compositions. As compared to the uncross-linked blends, dynamically cross-linked blends displayed high pseudoplastic behavior and provides unique processing characteristics that enable to perform well in both injection molding and extrusion process. The high viscosity at low shear rate provides the integrity of the extrudate during extrusion, and the low viscosity at high shear rate enabling low injection pressure and less injection time. Also the low die-swell characteristics of cross-linked blends also gave high precision for dimensional control during processing (extrusion).

Morphology and properties of super-toughened bio-based poly(lactic acid)/poly(ethylene-co-vinyl acetate) blends by peroxide-induced dynamic vulcanization and interfacial compatibilization

Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials.