Natural rubber/polystyrene (NR/PS) blend films with weight ratios of 70/30, 60/40, and 50/50 were prepared using polystyrene grafted natural rubber copolymers (NR-g-PS) as the compatibilizer. Copolymers with molar ratios of 90/10, 80/20, and 70/30 were synthesized via emulsion copolymerization using tert-butyl hydroperoxide/ tetraethylene pentamine as an initiator. The copolymers were subsequently added into the blends at 0, 5, 10, 15, 20, 25, and 30 phr. The mixtures were cast into films by the solution-casting method using toluene as the casting solvent. Mechanical and morphological properties of the prepared films were investigated. The film prepared from 80/20 NR-g-PS showed higher tensile and tear strength, as well as finer domain size of the dispersed phase, than those prepared from 90/10 and 70/30 NR-g-PS. However, the mechanical properties of the films were decreased at high loading of the copolymers. In addition, themogravimetric analysis revealed that weight loss was decreased upon introduction of the compatibilizer.

Mechanical properties and morphology of the deproteinized natural rubber (NR) films reinforced with modified silica (SiO2) nanoparticles were studied in this research. In the step of deproteinization, a chemical method followed by centrifugation was used to reduce the amount of protein from 0.42 wt% to 0.11 wt%. Structure-modified nanosilica with Silane A174 was used as an additive to reinforce the deproteinized films. The addition of 1 phr of the modified nanosilica exhibited better tensile strength, tensile force at break, modulus at 500% and elongation at break which were improved significantly compared to those of bare films. The modified nanosilica dispersed uniformly in the rubber matrix with the nanoparticle size less than 100 nm observed from the scanning electron microscope. The prepared rubber films containing the modified SiO2 nanoparticles have great potential to produce the NR gloves having very tiny amounts of protein for medical use which still provide the good mechanical strength compared to the standard ones.

The effects of graft copolymers applied as compatibilizers for natural rubber/nitrile rubber (NR/NBR) blends at 50/50 (w/w) on cure characteristics, mechanical properties, thermal properties, oil resistance, and morphology were investigated. The graft copolymers of methyl methacrylate (MMA) onto NR initiated by benzoyl peroxide (NR- g-PMMA<BPO>) and by potassium persulfate (NR- g-PMMA<PPS>) under emulsion polymerization were synthesized and used to compatibilize the blends. The structures of the copolymers were characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. NR was blended with NBR via a two-roll mill at 70°C under the compatibilizer loading ranging from 0 to 10 parts per hundred of rubber (phr). The results showed that the tensile property and tear strength of the blends increased with the increasing amount of NR- g-PMMA<BPO> as a compatibilizer. Thermal aging determined in terms of tensile properties exhibited the smaller difference between before and after aging in an oven with the increasing compatibilizer loading. The morphology of the compatibilized NR/NBR vulcanizates was investigated by scanning electron microscopy of the tensile fracture surfaces, which exhibited the improvement of interfacial adhesion between the two rubber phases. The thermal properties of compatibilized NR/NBR vulcanizates were reported in terms of a glass transition temperature under differential scanning calorimetry and dynamic mechanical analysis. The incorporation of an appropriate amount of the compatibilizer into the blends apparently improved the oil resistance of NR. Among them, the blend filled with 7.5 phr of NR- g-PMMA<BPO> showed the lowest volume change in IRM 903 oil.

Epoxidized natural rubber (ENR) was synthesized from natural rubber (NR) latex via in situ epoxidation using HCOOH and H2O2. The prepared ENR with 22 mol% epoxidation (ENR-22) was reinforced with silane modified silica (SMS) nanoparticles with different SMS loading in latex stage. The tensile properties, thermal stability, oil resistance and morphology of the ENR-22/SMS nanocomposites were investigated. The tensile strength was improved significantly and gained the maximum point at 7.5 phr SMS content. The thermogravimetric analysis showed an increased initial degradation temperature with the addition of SMS, suggesting higher thermal stability of the nanocomposites. The oil resistance of ENR-22/SMS nanocomposites in IRM 901 oil and IRM 903 oil were increased with the increasing amount of SMS content, indicating having improved oil resistance. The morphology revealed that the dispersions of SMS have been significantly improved since most of the spherical clusters of nanoparticles were individually scattered among the ENR matrix.