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This work investigates the effect of epoxidized low molecular weight natural rubber (ELMWNR) in silica- and carbon black-filled natural rubber (NR) compounds on processing and mechanical and dynamic mechanical properties. The ELMWNRs with different mol% epoxide content were prepared from depolymerization of epoxidized NR using periodic acid in latex state to have a molecular weight in a range of 50 000–60 000 g/mol. Their chemical structures and actual mol% of epoxide were analyzed by 1H NMR. The ELMWNRs were added to the filled NR compounds as compatibilizers at varying loadings from 0 to 15 phr. The addition of ELMWNR decreases compound viscosity and the Payne effect, that is, filler–filler interaction, of the silica-filled compound. In the silica–silane compound and the compound with 28 mol% epoxide (ELMWNR-28), the compound viscosities are comparable. The optimal mechanical properties of silica-filled vulcanizates are obtained at the ELMWNR-28 loading of 10 phr. In contrast, the addition of ELMWNR to a carbon black-filled compound shows only a plasticizing effect. The incorporation of ELMWNR into NR compounds introduces a second glass transition temperature and affects their dynamic mechanical properties. Higher epoxide contents lead to higher loss tangent values of the rubber vulcanizates in the range of the normal service temperature of a tire.

Magnetic polymer composites containing recycled neodymium-iron-boron (NdFeB) powder and natural rubber (NR) were prepared by the two-roll mill technique. Their mechanical and cure properties were studied as a function of NdFeB loading from 0-120 phr. With increasing magnetic loading, the cure time of the NdFeB-NR composites were exponentially decreased because of the reduction of the polymer chain crosslink. The tensile strength of the NR compound, related to the cure characteristics, was reduced by 40% by the addition of 10 phr NdFeB fillers because of the inhibition of the stress-induced crystallization. However, the variation in loading from 30-90 phr has modest effects on the tensile strength as well as elongation at break and the hardness. Furthermore, recycled NdFeB-NR composites had higher modulus and lower percentage of swelling in this magnetic loading regime. Simple tests confirmed the distribution of magnetic stray field around pieces of NdFeB-NR composites.

Epoxidized low molecular weight natural rubber (ELMWNR) with 28 mol% epoxide groups and weight average molecular weight of 49,000 g mol À1 was prepared by oxidative degradation of epoxidized natural rubber (NR) using periodic acid in the latex state. ELMWNR-28 was used at 10 parts per hundred parts of rubber (phr) loading in combination with bis-(triethoxysilylpropyl) tetrasulfide (TESPT) as the silane coupling agent in the range of 0-4.5 phr in silica-reinforced NR compounds. The use of TESPT in combination with ELMWNR-28 gives lower mixing torques and compound viscosities compared with the use of TESPT alone and the system without any compatibilizer. The bound rubber content, modulus, and tensile strength of the compounds with only TESPT strongly depend on the TESPT loading. The use of ELMWNR-28 as a compatibilizer clearly improves such properties compared with the non-compatibilized systems. By adding TESPT into the compound with ELMWNR-28, the properties further improve with increasing TESPT loading. The combined effect of ELMWNR-28 at 10 phr with a small amount of TESPT at 1.5 phr results in compounds with superior processability (i.e. low Mooney viscosity and Payne effect), and only slightly lower modulus and Downloaded from reinforcement index (M300/M100) compared with the use of the optimum content of TESPT. This compatibilizer/TESPT combination has the environmental benefits that the ELMWNR is a naturally based product, and that the reduced amount of TESPT silane coupling agent emits a greatly reduced amount of ethanol during processing.

Physical properties of polyurethane (PU) can be modified for desired applications by adding appropriate fillers. In this work, cobalt (Co) powder of average diameter 2 μπι was filled in PU elastomers synthesized by a reaction between polyol and diisocyanate. Variation of Co loading (0, 20,40 and 60 wt.%) modified thermal properties of PU composites in terms of the shift in a melting temperature and the increase in heat absorption. From DC hysteresis loops, PU/Co composites exhibited ferromagnetic properties with improved magnetizations by the increase in Co loading. On the other hand, the coercive field was almost unvaried. For high frequency electromagnetic behaviors, the complex electrical permittivity (ε-je") and magnetic permeability (μ'-]μ") were sensitive to the frequency from 10 MHz up to 100 MHz and reached the modest values in the regime between 100 MHz and 1 GHz. At each frequency, the real part of permeability and permittivity of PU were raised by the inclusion of Co fillers. While the thermal behaviors were explained using the interaction between Co clusters and the PU matrix, the electromagnetic properties can be understood by taking into the account of interactions between Co clusters at high loading levels.

Silica-filled natural rubber (NR) encounters incompatibility problems, owing to the strong particle-particle interaction arising from the hydrogen bonds of hydroxyl groups, which generally leads to the formation of agglomerates. The addition of coupling agents, especially silane coupling agents, reduces the agglomeration. However, this has some disadvantages, such as toxicity, a risk of pre-curing, and the generation of ethanol during mixing. This work aims to focus on the effect of filling the plasma-polymerisation of polyacetylene-coated silica into natural rubber compounds. The deposition of plasma-polymerised acetylene applied to silica particles was firstly carried out using a radio frequency (RF) with an input power of 20 kW for 60 min and further incorporated into NR compounds. On the surface of the coated silica analysis, the formation of a polyacetylene layer on the silica surface was obviously confirmed that it exhibited more stability in water. The following polyacetylenecoated silica (PA-coated silica)-filled NR compound properties were analysed: mixing energy and temperature, Payne effect, complex viscosity, and cure characteristics. The NR compounds mixed with PA-coated silica showed a lower mixing torque, dumping temperature, Payne effect, and viscosity, when compared to NR compounds with unmodified silica and ordinary silane systems. However, the differences were insignificantly noticed in the cure characteristics of the compounds. Polyacetylene-coated silica developed from plasma polymerisation can be used to improve the uniformity of dispersion, as well as the compatibility of silica in a natural-rubber matrix, without changing its cure characteristics, compared to the one with a silane coupling agent.

This work investigates the effect of epoxidized low molecular weight natural rubber (ELMWNR) in silica-filled NR compounds on processing, mechanical and dynamic mechanical properties. The ELMWNRs with mol% epoxide groups varying from 0-50 and molecular weight in a range of 50,000-60,000 g/mol were prepared from depolymerization of epoxidized natural rubber using periodic acid in latex state. They were then added in the silica-filled NR compounds as a compatibilizer at varying loading from 0-15 phr. The addition of ELMWNR decreases compound viscosity and Payne effect, i.e. filler-filler interaction. The optimal mechanical properties of silica-filled vulcanizates are observed at the ELMWNR-28 (28 mol% epoxide) loading of 10 phr. The incorporation of ELMWNR with 28 and 51 mol% epoxide groups into NR compounds introduces a second glass transition temperature and affects on their dynamic mechanical properties. Higher epoxide content leads to higher Tan δ of the rubber vulcanizates in the range of normal service temperature.

The properties of both compounds and vulcanizates of silica-filled natural rubber (NR) compatibilized with epoxidized low molecular weight natural rubbers (ELMWNRs) consisting of 12 and 28 mol% epoxide are investigated. The ELMWNRs with a molecular weight range of 50,000 to 60,000 g/mol are produced by depolymerization of epoxidized natural rubber (ENR) latex using periodic acid, and then used as compatibilizer in a range of 0 to 15 phr in virgin NR. The compounds with LMWNR without epoxide groups, and with bis-(triethoxysilylpropyl) tetrasulfide (TESPT) coupling agent are also prepared for comparison purpose. Incorporation of ELMWNRs lowers Mooney viscosity and Payne effect to the level closed to that of silica/TESPT compound, and clearly enhances the modulus and tensile strength of vulcanizates compared to the compounds with no compatibilizer and LMWNR. The higher epoxide groups content results in the better tensile properties but somewhat less than the compound with TESPT. Addition of extra sulfur into the compounds with LMWNR and ELMWNRs to compensate for the sulfur released from silane molecule in the silica/TESPT system shows small influence on Mooney viscosity, but remarkably enhances 300% modulus, tensile strength and loss tangent at 60°C as a result of the better network formation.