Papers by Keyword: Dynamic Vulcanization

Abstract: To achieve higher thermal electric and mechical properties in non-polar thermoplastic vulcanizate (TPV), multi-walled carbon nanotubes (MWCNTs) as reinforcing nanofiller to prepare TPV/MWCNTs conductive elastomer composites by dynamic vulcanization. The thermodynamic calculation indicates that MWCNTs have a tendency to preferentially localize at the two-phase interface of PP and IIR during melt-blending processing. The morphology of TPV/MWCNTs composites elucidated from TEM micrograph exhibited that the IIR domains dispersed in the PP matrix, and most MWCNTs were dispersed at the two-phase interface and PP phase, which is mainly due to the effect of kinetic factors. When the MWCNTs content reached the percolation threshold (3 wt%), the network structure of MWCNTs was formed, the ac conductivity and dielectric permittivity increased sharply. Compared with pristine TPV, the thermal conductivity of TPV/MWCNTs composites increased 39.7 %. The MWCNTs can combine to the IIR network during dynamic vulcanization, and enhances the interface interaction of MWCNTs and TPV matrix, which is improve the tensile strength of TPV/MWCNTs composites.

Abstract: This work aimed to study effect of rotor speed during melt mixing of natural rubber/polycaprolactone (NR/PCL) on the morphology which controls mechanical properties of dynamic vulcanizate using Luperox101 as a curing agent in NR component. The rotor speeds at 60 and 80 rpm were compared. The morphology of NR/PCL vulcanizates elucidated from SEM micrograph showed that the vulcanizates exhibited NR paticles dispersed in PCL matrix. In addition, the phase size of dispersed NR should be smaller with increasing rotor speed due to the increased shear force. This large PCL domain induced stronger strain hardening in stress-strain behavior under tension. This behavior is closed to tensile behavior of PCL and appeared at the vulcanizates. In terms of modulus, Young’s modulus was concentrated and reported. The lower degradation of PCL phase during melt mixing in the vulcanizates prepared from melt mixing at rotor speed of 60 rpm was responsible for higher Young‘s modulus than that prepared from rotor speed of 80 rpm. The tension set of NR/PCL vulcanizates prepared with rotor speed of 60 was higher than that with rotor speed of 80 rpm. It was suggested by Nakason et.al. [1] that the tension set of vulcanizates should be lower than 50 % so that they could be applied for thermoplastic vulcanizates. In this system, tension set values of the vulcanizates containing PCL 30-45 wt.% were lower than 50% in both rotor speed conditions.

Abstract: The effects of thermoplastic starch (TPS) loading on polypropylene (PP)/natural rubber (NR) blend vulcanized with N, N’-m-phenylene bismaleimide (HVA-2) were investigated. Thermoplastic starch ratios was varied at 5%,10%,20% and 30% weight percentage in order to imparted biodegradable properties into PP/NR blends. The study has focused on the thermoplastic starch loading and blend’s modification on the mechanical properties, morphology and biodegradable properties of PP/NR blends. This study showed that the tensile properties of the PP/NR blends were deteriorated with increasing in TPS content. The dynamic vulcanization by using HVA-2 crosslinker was applied on the blends in order to compensate the deterioration properties caused by incorporation of TPS. According to the results, the HVA-2 crosslinker showed the increasing in tensile properties as well as better morphology analysis as compared to unvulcanized counterparts. On top of that, the scanning electron microscopy (SEM) studied also found that the interfacial adhesion and dispersion of TPS was improved upon HVA-2 vulcanized in PP/NR blends. Microscope images after soil burial test show that the HVA-2 crosslinker has delayed the biodegradability of PP/NR/TPS blends.

Abstract: PP/EPDM blends were prepared by dynamic vulcanization technology within a HAAKE torque rheometer. The effect of different plastic/rubber ratios of PP/EPDM blends on the curing behavior and crystallization kinetics were investigated. The obtained results showed that the plastic/rubber ratios played an important part in the solidification process as well as the crystallization kinetics. With increasing EPDM content, the cooling rate of PP/EPDM blends was significantly larger than that of neat PP. When PP content was 20 wt%, the crystallinity of PP was obviously larger than that of neat PP. Compared with neat PP, the crystallization temperature of the blends were remarkably shifted to the lower temperature. EPDM particles showed active effect on the nucleation process of PP during the cooling crystallization of the PP/EPDM blends.

Abstract: The effect of dynamic vulcanization and fiber loading on properties of low density polyethylene (LDPE)/natural rubber (NR)/water hyacinth fibers (WHF) were investigated. In this study, the vulcanized thermoplastics were obtained by in situ dynamic curing of LDPE/NR/WHF composites. The LDPE/NR/WHF composites with different fiber loading were prepared by using Brabender mixer at 180 °C with the rotor speed of 50 rpm. The results showed that dynamic vulcanized LDPE/NR/WHF composites gave a higher tensile strength, Young’s modulus, elongation at break but lower molar sorption than unvulcanized LDPE/NR/WHF composites. The SEM micrographs also displayed better fibers dispersion and the crosslink formation in dynamic vulcanized LDPE/NR/WHF composites indicated better interfacial bonding among fibers and matrix compared to unvulcanized LDPE/NR/WHF composites.

Abstract: Dynamic vulcanized thermoplastic olefin/ organoclay composites were prepared in this paper. The morphology of the composites is studied with WAXD, which suggest organoclay shows good dispersion in TPV. The prepared TPV/organoclay composites improved mechanical properties significantly, the thermal property were also changed when organoclay is added. Besides, the content of curing agent and the addition of oil on the influence of properties were discussed.

Abstract: The effects of dynamic vulcanisation in vPE/rPE/EPDM blends were studied. The discarded polyethylene used in the study was obtained from local cable manufacturers. The effects of different sulfur loading on the tensile properties and morphology of the thermoplastics elastomer blends were examined. Results show that the tensile properties (except E_B) increased as increasing in sulfur loading. Scanning electron microscopy indicates that a uniform distribution of vulcanised EPDM in vPE/rPE/EPDM blends.

Abstract: Thermoplastic vulcanizate (TPV) based on natural rubber (NR) and polypropylene (PP) blends were successfully prepared through a dynamic vulcanization process using Brabender Plastograph EC Plus with a rotor speed of 60 rpm at 180°C. Sulfur vulcanization system was used to cure rubber phase in the TPVs. Three grades of PP (i.e., PP700J, HP553R and HP544T) were used to blend with NR at a fixed blend ratio of NR/PP = 60/40. The mechanical properties, crosslink density, complex viscosity and morphological properties of the blends were examined. The results revealed that the dynamically cured NR/PP700J samples showed the best mechanical properties because of higher crosslink density and smaller rubber particle size when compared with those of the blends combined with HP553R and HP544T. Furthermore, the complex viscosity of the TPVs was highest for the blends with PP700J.

Abstract: The mixing efficiency of intermeshing rotor internal batch mixers for the preparation of rubber-rich thermoplastic vulcanizates (TPV) based on ethylene propylene diene terpolymer (EPDM) and polypropylene (PP) blends was investigated. Two laboratory scale mixers, namely intensive batch mixer (INS) and kneader batch mixer (KND), were used. The mixer choice at controlled mixing conditions was investigated to determine its effects on morphological and mechanical properties and crosslink density of the prepared EPDM/PP TPVs. Such effects were found on the degradation of the polymer, on the distribution of the EPDM phase in the blend morphology, particularly the size of EPDM inclusion, and on the crosslink density of the EPDM phase. In summary, the different mixing efficiencies of INS and KND type mixers affect the EPDM/PP TPVs and their properties. Also, the INS mixer has higher mixing efficiency than the KND mixer.

Abstract: Dynamically vulcanized NR/ABS blends by phenolic curing were carried out using an internal mixer at 180 °C. The effect of NR/ABS ratio (i.e., 50/50, 60/40, 70/30) on mechanical, dynamical and morphological properties was investigated. It was found that the tensile strength and hardness increased with an increase in ABS loading whilst the elongation at break decreased, indicating that the strength and hardness attributed to thermoplastic component whereas the elasticity of the blends contributed to the vulcanized NR. The results showed that the 60/40 NR/ABS blend provided the well-balanced mechanical properties. The storage modulus of thermoplastic vulcanizates (TPVs) increased with increasing contents of rubber. This is due to that a higher content of vulcanized NR domain was dispersed in the ABS matrix. The results agreed well with the tan δ and complex viscosity of the TPV at various blend ratios. SEM micrographs of 60/40 NR/ABS blend showed that vulcanized rubber domains were dispersed in a continuous ABS phase and it contributed to greater interfacial adhesion between the two phases and thus provided superior properties.