In this research, we present an easy way to prepare environment-friendly hydrophilic rubbers derived from natural rubber (NR) grafted with sodium acrylate (NaAA) through reactive blending using an internal mixer operated at a rotor speed of 80 rpm and 150 C. The key parameters affecting the grafting efficiency of NR-g-NaAA were investigated in terms of the fill factor (FF) of the chamber, mixing time, and NaAA content. Lastly, the grafted sample (with a suitable grafting efficiency) was crosslinked using peroxide curing to produce X(NR-g-NaAA) as a hydrophilic NR sample. Results showed that grafting effi-

The addition of ethylene-propylene-diene rubber (EPDM) into acrylic sheets was expected to enhance their thermal and UV aging resistance for outdoor applications. According to the dissimilar polarity of EPDM and styrene (ST)/methyl methacrylate (MMA) monomer mixture (20/ 80% (w/w)) used for preparation of acrylic sheets, this research aimed to modify EPDM via graft copolymerization with ST and MMA to increase its compatibility. The graft copolymerization of ST and MMA at a ST/MMA ratio of 25/75% (w/w) onto EPDM was carried out in the solution polymerization initiated by benzoyl peroxide at 90°C for 16 h, resulting in 88.1% grafting efficiency. The addition of 1.0-3.0% (w/w) of graft EPDM (GEPDM) into the acrylic sheets increased their impact strength (~17-22%), but decreased their flexural strength (~12-36%). However, their mechanical properties were improved after thermal and UV aging. Scanning electron microscopy (SEM) based analysis of the modified acrylic sheets revealed that the fracture surface shifted from brittle to ductile failure characteristics after modification. The thermogravimetric analysis results also exhibited that the addition of GEPDM improved the thermal and UV resistance of the modified acrylic sheets by increasing their initial decomposition temperature and activation energy of thermal decomposition.

In this research, the effect of hydroxyl-terminated polybutadiene (HTPB) on processability, mechanical properties, thermal aging and oil resistance of 80/20 ethylene-propylene diene rubber/epoxidized natural rubber (EPDM/ENR) blend was investigated. The amount of HTPB used was varied from 0-4 parts per hundred of rubber (phr). The results revealed that addition of HTPB into EPDM/ENR blend decreased the compound viscosity, while scorch time and cure time slightly increased with increasing HTPB content. Furthermore, hardness, tensile and tear strengths of the blend decreased due to the poor dispersion of fillers in the presence of HTPB. After thermal aging treatment, the crosslink density of all EPDM/ENR blends increased leading to increasing in 100% modulus, tensile strength and swelling resistance, as well as reducing in elongation at break. However, it had additional plus features that high resilience with low compression set was achieved in the blend containing 2 phr of HTPB.

No abstract

The aim of this research was to reduce and improve the brittleness and thermal properties of poly lactic acid (PLA), respectively. Epoxidized natural rubber (ENR) was used to enhance the toughness and rutile titanium dioxide (R-TiO2) as filler was also incorporated to improve the thermal properties of the PLA. 10wt% ENR with epoxidation contents of 25 mol% (ENR25) and 50 mol% (ENR50) and various R-TiO2contents (0-10 phr)were compounded with PLA by using a twin-screw extruder at 155-165°C and a rotor speed of 40 rpm. The pellets of blends were then formed a thin film using a cast film extruder machine and cooled down under air flow. Thermal and mechanical properties and morphology of PLA/ENR/R-TiO2thin film were investigated. The crystallinity of PLA was found to increase with addition of ENR. The mechanical properties of thin film showed that the ENR50 enhanced the elongation but reduced the tensile strength of PLA with addition of R-TiO2at 5 and 10 phr, respectively. The TGA indicated that the addition of 10 phr R-TiO2increased in the decomposition temperature at 5% weight loss (Td5%) of PLA/ENR film. Thus the thermal stability of PLA/ENR50 was found to improve with addition of R-TiO2. From morphology study, the ENR50 phase showed a good dispersion in the PLA matrix. In conclusion, the addition of ENR and R-TiO2was found to enhance both toughness and thermal stability of PLA.