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A unique technology for producing thermoplastic vulcanizate (TPV) has been developed using an intermeshing-type internal mixer (ITM). TPV produced by the ITM was compared with that produced using a co-rotating twin screw extruder (Co-TSE) to assess the former’s commercial possibilities. TPV, originating from ethylene-propylene-diene monomer (EPDM) and polypropylene (PP), was produced by both machines with equal filled volumes, same shear rate, and same specific mechanical energy. Results indicate that ITMs can be used to produce TPV with mechanical properties comparable to those of TPV produced by Co-TSE. TPV can be produced with a lower shear rate with ITM compared to Co-TSE. A long residence time can be maintained in the mixing chamber of the ITM, allowing high conversion of the cross-linking reaction and resulting in better elastic recovery properties due to the higher cross-linking density. However, this resulted in higher viscosity of TPV produced by ITM.

In the present work, the influences of filler type and content on cure characteristics, mechanical and dynamic mechanical properties, and heat aging resistance of filled styrene butadiene rubber (S...

This present work deals primarily with uncertainty and measurement problems in determining the phase morphology and the polymer compatibility in some blend systems. Ternary blends in the form of dynamically vulcanized EPDM/EOC in PP matrix were investigated across EPDM/EOC blend ratios. Both rheological study and SEM micrographs attribute the compatibilizing effects to the EOC, which acts as a wetting agent at the EPDM/PP interfaces between phases. This reduces the size of dispersed elastomer phases and prevents the coalescence of dispersed domains, in a dose-dependent manner with EOC content. The estimated interfacial tension, work of adhesion, relative interfacial energy and viscosity ratio of the blend components indicate that potentially the EOC phase has with the PP phase greater compatibility and stronger interactions than it has with the EPDM. Morphologically the EPDM/EOC/PP ternary blend has core–shell structures, with EPDM-cores encapsulated by EOC-shells, and such core–shell particles dispersed in the PP matrix. Moreover, the dispersed elastomer phases with core–shell structure are found to dominate when the volume fraction of EOC in the blend is sufficient. Keywords: Polymer blends, Dynamic vulcanization, Phase morphology, Interfacial properties, Melt viscosity, SEM observation

Titanium dioxide (TiO2) is normally added into the rubber compounds as a white pigment and inorganic filler for an improvement of thermal property. TiO2 is also known to have an outstanding photocatalytic activity. This work investigates the properties of natural rubber (NR) compounds filled with 5 phr of nanoTiO2 (n-TiO2). Since the direct incorporation of n-TiO2 into NR encounters incompatibility problem, therefore two types of coupling agent (i.e. bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT) and isopropyl trioleyl titanate (ITT)) are used. The coupling agent loading is varied in a range of 0-20 wt% relative to the n-TiO2. Mooney viscosities and minimum cure torque (ML) of the compounds increase with increasing coupling agent content and the ones with ITT show higher viscosity than the mixes with TESPT. The use of TESPT leads to shorter optimum cure time and higher torque difference compared to the use of ITT. The addition of n-TiO2 results in the improved modulus, reinforcing index and tensile strength compared to the unfilled vulcanizate. The presence of both TESPT and ITT significantly reduces a photodegradation efficiency. The difference in the properties and photocatalytic activity of n-TiO2 filled NR having TESPT and ITT as coupling agent indicates their possible different level of dispersion and interactions at the interphases.

Non-isothermal crystallization behavior and melting characteristics of polypropylene (PP) in EPDM/PP and EOC/PP TPVs were studied at various cooling rates using differential scanning calorimetry (DSC). The results revealed that the crystallization of PP in the TPVs occurs at a lower degree of undercooling, relative to neat PP, with smaller size PP crystals. The vulcanized EPDM and EOC particles could accelerate the crystallization of the PP phase either by providing nucleation or by promoting interfacial crystallization. The crystallization exotherm and melting endotherm peaks of the TPVs were broad, and they shifted towards lower temperatures as the cooling rate was increased. The analysis of non-isothermal crystallization kinetics indicates that the crystallization of the PP in the TPVs is heterogeneous nucleation, with two or three-dimensional growth during primary and secondary crystallization. Furthermore, the vulcanized EPDM and EOC particles promote the initial crystallization activation energy of the PP in TPVs to exceed that of the neat PP. The developed mathematical models show an approximately power-law dependence on the cooling rate for the crystallization behavior and the melting characteristics of PP in the TPVs.

The optimum condition of processing parameters (mixing temperature, rotor speed, fill factor, and blend ratio) and prediction models for the best key mechanical properties of ethylene propylene diene terpolymer/polypropylene thermoplastic vulcanizates (EPDM/PP TPVs) was investigated by using the Taguchi's optimization technique and data analysis. The results reveal that all of the processing parameters affected significantly the mechanical properties of the EPDM/PP TPVs, but specifically the blend ratio contributed more than 90% in effect size on tensile strength and tension set. There were three main factors, the mixing temperature, the fill factor, and the blend ratio, influencing the elongation at break. Furthermore, the mathematic models were effective and reliable in predicting the properties of TPVs. The correlation of mechanical properties, stress relaxation, and phase morphologies of the TPVs prepared from the predicted models was also investigated. It can be summarized that the morphological structure and stress relaxation of the TPVs were strongly governed by the EPDM content in the blend ratio. That is, the higher the EPDM content, the better phase morphology having smaller size of the vulcanized EPDM particles distributed in the PP matrix and the higher rate of stress relaxation. Moreover, these two properties were then principally pushing the mechanical characteristics of the EPDM/PP TPVs. Copyright © 2015 John Wiley & Sons, Ltd.

The isothermal and non-isothermal crystallizations of PP in neat form and in the TPVs EPDM/PP and EOC/PP were investigated using differential scanning calorimetry (DSC). The crystallization of PP was systematically studied by fitting mathematical models, and was later confirmed by X-ray diffraction (XRD) and by scanning electron microscopy (SEM). The experiments revealed that crosslinked elastomer particles first accelerated the primary nucleation of the PP matrix, acting effectively as a nucleating agent that reduces the induction time while increasing the nucleation efficiency. In the secondary nucleation regime (growth of spherulites), the crosslinked elastomer particles enhanced crystal growth rate, reducing the nucleation energy contribution from PP chain folding. Moreover, the crosslinked elastomer particles increased the final thickness of PP lamellae from that of neat PP, and this was corroborated by the XRD results. On comparing the two types of elastomer, it was found that the EOC particles were more effective in heterogeneous cell nucleation than the EPDM particles. The morphological study by SEM revealed completely altered PP spherulite size and shape, as well as their altered distribution, affected by heterogeneous nucleation effects of the crosslinked elastomer particles.

Titanium dioxide (TiO2) possesses excellent photocatalytic activity and provides UV protection for polymeric materials. The nanosized TiO2 particles with larger surface area to volume ratio and an increased surface reactivity shall impart better photocatalysis and UV protection efficiency to the rubber compounds, compared to the use of conventional micron-sized particles. Direct incorporation of TiO2 nanoparticles (n-TiO2) into non-polar rubbers faces incompatibility problem between the two phases. One of the solutions to overcome this problem is to treat the nanoparticle surface by using silane coupling agent such as bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT). This work prepared n-TiO2 from commercial micron sized-TiO2 by ultrasonication technique. Particle size of TiO2 was measured by laser light scattering particle size analyzer. The morphology of TiO2 nanoparticles was characterized by field emission scanning electron microscope (FESEM). The grafting reaction of silane on TiO2 nanoparticles surface was studied at varying reaction temperatures and times. The purified grafted materials were characterized by energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The characterization data confirm a presence of grafted silane on the TiO2 nanoparticles surface. The result shows that ultrasonication technique can effectively decrease particle size and the grafting reaction of silane coupling agent onto TiO2 nanoparticles can be successfully carried out at 140°C for 8 h.

Thermoplastic vulcanizates (TPVs) were produced by high speed intermeshing-type internal mixer. TPVs based on Ethylene-propylene-diene rubber (EPDM) and polypropylene (PP) with peroxide crosslink system, were used in this investigation. TPVs were prepared by different processing condition using the same TPV recipes. In this study we focus on the effect of mixing pattern on TPVs properties. From the results, tensile properties and hardness of TPVs are slightly affected by processing conditions. In the same way, compression set which relate to crosslink density in rubber phase, were not affected by processing condition as well. All TPV samples were extruded to form a strip of 1 x 50 mm rectangular cross section using single screw extruder. It was found that, the stage of adding curative shows significant influence on extrudates surface of TPVs. TPV samples produced by adding the curative at low temperature show the smoothest surface. This is because the fine dispersion of crosslinked rubber phase which confirmed by AFM.

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.

In this work, to study the utilization of zinc dimethacrylate (ZDMA) in sulfur vulcanized styrene butadiene rubber (SBR). The compounds were prepared by two roll mill mixer. Crosslink density and crosslink types were determined with an equilibrium swelling method. Physical properties and heat aging resistance were studied. The results shows that increase of ZDMA will decrease cure rate index and crosslink density which lead to decreased in 300% modulus and hardness. However, the addition of ZDMA can improve tensile strength, tear strength, elongation at break and heat aging resistance.

Natural rubber/rutile-TiO 2 nanocomposites (NR/n-TiO 2 (R) composites) with different n-TiO 2 (R) contents were prepared. The n-TiO 2 (R) with median particle size ( d 50) of 73 nm was successfully prepared from commercial micron-TiO 2 (R) by ultrasonication. NR incorporated with n-TiO 2 (R) shows the good performance in mechanical properties as well as UV-protection and antibacterial properties. The mechanical performance of NR/n-TiO 2 (R) composites was enhanced with an increase of n-TiO 2 (R) content up to the optimum content at 5 phr (parts per hundred parts of rubber) and then declined. In addition, the prepared NR/n-TiO 2 (R) composites possess the UV-protection material. The UV-protection property of NR nanocomposites was evaluated by measuring the evolution of carbonyl absorption band from ATR-FTIR spectra, surface cracking, and mechanical properties after UV irradiation. The presence of n-TiO 2 (R) exhibits significant improvement in photo-degradation by UV irradiation compared to the unfilled NR. More importantly, the obtained NR/n-TiO 2 (R) composites demonstrate effective antibacterial property against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), the strong antibacterial property of the prepared NR nanocomposites was obtained at the only loading level of 1 phr of n-TiO 2 (R). The prepared NR/n-TiO 2 (R) composites could be used as a novel antibacterial material.