Ekwipoo Kalkornsurapranee

Influence of Reaction Volume on the Properties of Natural Rubber-g-Methyl Methacrylate

Graft copolymer of natural rubber and poly(methyl methacrylate) was prepared using CHP/TEPA redox initiators at 50°C and a reaction time of 3 h. Various reaction volumes (i.e., 0.5, 100, and 200 L) were used to prepare the graft copolymer which was then characterized by Fourier transform infrared spectrophotometer and proton nuclear magnetic resonance spectrophotometer (1H-NMR) techniques. It was found that conversion of monomer to polymer and grafting efficiency slightly decreased with increasing reaction volumes. Quantity of grafted poly(methyl methacrylate) was calculated based on the integrated peak areas of the 1H-NMR spectra and quantitative analysis by extraction method. It was found that both techniques gave similar level of the grafted poly(methyl methacrylate) onto the natural rubber backbone. Furthermore, Mooney viscosities, glass transition temperature (Tg) and degradation temperature (Td) of the natural rubber and poly(methyl methacrylate) were slightly decreased with increasing the reaction volumes.

Investigation of Structure-Properties Relationship of High Performance TPV Based on ENR/TPU

Thermoplastic natural rubber based on blending of ENR-50/TPU and un-modified NR/TPU was prepared via dynamic vulcanization technique. Influences types of natural rubber (i.e., un-modified NR and ENR-50) on mechanical and morphological properties of the blends were investigated. It was found that the blends with ENR-50 exhibited superior properties than that of the blend with unmodified NR. This is attributed to the interactions between the functional groups of ENR molecules and polar functional groups in TPU molecules which caused higher interfacial adhesion and interaction between both phases. The chemical interactions were confirmed by ATR-FTIR. Furthermore, it was found that the ENR-50/TPU blend showed smaller and finer grain morphology compared with the un-modified NR/TPU.

Effect of Antioxidant on Properties of Thermoplastic Natural Rubber Based on ENR/TPU Blends

Thermoplastic natural rubber based on epoxidized natural rubber (ENR) and thermoplastic polyurethane (TPU) blend was prepared via dynamic vulcanization process. The main objective is to improve thermal properties of the blends. Two types of antioxidant: phenolic antioxidant (Wingstay®L) and N-(1,3-dimethzlbutyl)-N-Phenyl-p-phenylenediamine (6PPD) were used to improve oxidative degradation of the blends. It was found that thermal properties in term of thermal elastic properties and thermal stability can be improved by adding the antioxidants and 6PPD gave the blend with the highest thermal properties. These were measured based on temperature scanning stress relaxation (TSSR) technique. Incorporation of ENR into the TPU caused reduction of the hardness, improved thermal properties, elasticity and oil resistance compared to the neat TPU. These results indicated that the novel high performance TPNRs with high elasticity can be prepared.

Effect of processing parameters on the vulcanisation of natural rubber using glutaraldehyde

ABSTRACT The process ability of vulcanising natural rubber using glutaraldehyde at low temperature has been studied. The main objective of this work is to improve the properties and stability of natural rubber (NR) using glutaraldehyde as a curing agent. In this study, the vulcanised samples were prepared systematically and compared with sulphur cured natural rubber vulcanisates. The influence of mole ratio of ammonia and glutaraldehyde, and the processing parameters (i.e. curing time and temperature) was investigated. The cured NR based on glutaraldehyde exhibited better hardness and thermal properties than that of the NR cured from conventional sulphur system. The experimental results reveal that the properties of glutaraldehyde cured NR can be developed with the proper additives combination and conditions adopted in the preparation. This cured system is very interesting due to it can be used for high temperature industrial applications. Moreover, it eases of processing at low temperature and cost.

Medicated Pressure Sensitive Adhesive Patches from STR-5L Block Rubber: Effect of Preparation Process

STR-5L is a high quality block rubber in Thailand that is interesting to apply in medical and pharmaceutical products because it has very low impurity but high uniformity. In this study, medicated pressure sensitive adhesive (PSA) patches were developed by melt blending technique using hydroxyethyl cellulose (HEC) as tackifier and paraffinic oil as softener. Two rolls mill was used to blend all ingredients and the thin PSA patches were rolled out. Various preparation parameters were studied such as initial viscosity of rubber (60 or 80 Mooney viscosity; MV), mastication time (5-20 minutes), step of mixing, mixing time (35-80 minutes) and gap between rollers (0.1-0.4 mm). The suitable processing conditions were optimized. It was found that the rubber having initial viscosity of 80 MV provided better physical properties, for example, higher force T-peel, lap shear strength and shear holding time. Longer mastication time increased the shear holding time of patches. At 70 minutes of mixing time, the patches showed the highest shear holding time and did not leave any residue on the testing equipment surface. Moreover, the shear holding time decreased when the gap between rollers was expanded. Mixing method with the sequential addition of STR-5L, HEC and then paraffinic oil, provided good PSA patches. However, preparation process did not affect the plasticity retention index of PSA patches due to there were not significant change of values when those all parameters were varied. Next, lidocaine or its hydrochloride salt in powder form could be blended into this PSA to be the homogeneous patches. This lidocaine PSA patches for local anesthetics application on the skin would be evaluated in further study.

Mechanical Properties and Morphology of ER/PS Blends

Thermoplastic elastomeric blends of Polystyrene (PS) and Exudated Resin (ER) with different compositions have been prepared by solution casting method. The mechanical performance of this system has been studied in detail. Stress-stain behavior, tensile strength, elongation at break and young’s modulus was determined. The effect of blend ratio on the mechanical properties and surface hardness has been analyzed. By the addition of ER reduces the plasticity of polystyrene. The blend with 60/40 PS/ER combination exhibited comparatively better mechanical properties. 60/40 PS/ER blend ratio shows higher compatibility between the phases among the series of the blends studied. It is explained on the basis of the morphology of the blend. Various theoretical models such as series, Parallel and Halpin-Tsai have been used to fit the experimental mechanical data. Scanning Electron Microscopy was employed to analyze the surface morphology of the blend.

Influence of Blend Proportions on Properties of ENR-25/TPU Simple Blends

Thermoplastic natural rubber (TPNR) based on blending of thermoplastic polyurethane (TPU) and epoxidized natural rubber with 25 mol % epoxide (ENR-25) was prepared by simple blend technique. Influence of various blend proportions was investigated. It was found that an incorporation of rubber caused decreasing of mechanical properties in terms of tensile strength, elongation at break and hardness. This is attributed to incorporation of rubber phase may cause chain restriction of the soft segments in TPU and hence lower elongation at break and tensile strength. It was also found that the tension set value decreased with increasing proportion of natural rubber which indicates greater elasticity or tendency to recover to the original shape after prolonged deformation. Additionally, shear stress and shear viscosity of the blends increased with increasing rubber proportions due to higher viscosity of the ENR-25 component which leads to higher force to compress the polymer melt flowing through a capillary channel. Morphological properties of the simple blend with various blend proportions exhibited formation of co-continuous phase structure was observed where larger rubber formation are observed in the blend with higher content of ENR-25 phase.