Sombat Thanawan

Origin of phase shift in atomic force microscopic investigation of the surface morphology of NR/NBR blend film.

Atomic force microscopy (AFM) was used to study the morphology and surface properties of NR/NBR blend. Blends at 1/3, 1/1 and 3/1 weight ratios were prepared in benzene and formed film by casting. AFM phase images of these blends in tapping mode displayed islands in the sea morphology or matrix-dispersed structures. For blend 1/3, NR formed dispersed phase while in blends 1/1 and 3/1 phase inversion was observed. NR showed higher phase shift angle in AFM phase imaging for all blends. This circumstance was governed by adhesion energy hysteresis between the device tip and the rubber surface rather than surface stiffness of the materials, as proved by force distance measurements in the AFM contact mode.

Synthesis of Graft Copolymers and Their Preliminary Use as a Compatibilizer in Polymer Solar Cells

Poly(p-xylylene)-graft-poly(butylacrylate-g-fullerene) or PPX-g-PBAFu was synthesized by using Wessling route and atom transfer radical addition (ATRA) techniques. The graft copolymers were used as a compatibilizer in the bulk heterojunction (BHJ) polymer solar cells of poly(3-hexylthiophene) (P3HT) and fullerene (C60). The results from AFM micrographs showed that the phase size of P3HT and the aggregated C60 in the blended system was decreased from 300 to 30 nm after adding the copolymer (20 pph). Furthermore, the efficiencies of the BHJ cells from J-V curve were remarkably increased five times after adding the copolymer.

Effect of Non-Rubber Components on Properties of Sulphur Crosslinked Natural Rubbers

Non-rubber components (mainly proteins and lipids) in natural rubber (NR) play important roles for controlling the properties of NR. Crosslinking process creates intermolecular chemical bonds in order to obtain a three-dimensional network, resulting in more elastic rubber. Sulphur crosslinking is the most popular method and is applied in the present study. Two types of NR were prepared, namely, whole natural rubber (WNR) and purified natural rubber (PNR). PNR was deproteinized by centrifugation method and then acetone extraction. These rubbers were crosslinked by an efficient vulcanization (EV) system. They were cured for three curing times (1xt90, 2xt90, 3xt90) at 150°C. WNR presents shorter curing time than PNR because there are some phospholipids and proteins which are natural accelerators for curing reaction. The presence of non-rubber components seems to play a major role on crosslinking density and adhesion phenomenon for rubber/glass system. AFM images of WNR show more heterogeneity and roughness compared to PNR.

Influence of Non-Rubber Components on NR Surface Modification by Chlorination

Natural rubber (NR) is a very useful elastomer and renewable polymer with outstanding properties compared to synthetic elastomers. However, as a natural polymer, the non-rubber species (proteins, phospholipids, carbohydrate, etc.) have to be considered carefully for the understanding of the surface and interfacial properties. Especially these components can markedly affect the frictional and adhesive properties of the rubber surface. Although many methods can be used to modify the surface properties, chlorination remains one of the easiest way.The present study deals with surface modification of peroxide crosslinked NRs and synthetic cis-1,4 polysioprene as reference samples by chlorination. Surface and frictional properties of these different rubbers were analyzed by various complementary techniques The influence of critical parameters on wetting, frictional and mechanical properties were investigated and will be discussed

Preparation and Characterizations of Natural Rubber from Natural Rubber Latex by Using Thermal Drying Method °"√»÷'—'''' πÈâ''È‚¥¬°"√"™ââ

Natural rubber prepared from thermal drying technique was achieved. The range of drying temperature covered from 70 I150 Ilocal-made machine. The cure characteristic at 155 I mooney viscosity, mechanical properties (before and after aging) were investigated as compared to control rubber (derived from acid coagulation) It was found that mooney viscosity of thermal dried natural rubbers (TNR) was higher than that of acid coagulated rubber (ANR). T 2 and T 90 of TNR for all vulcanizing system were shorter than that of ANR. The average mechanical properties of TNR showed slightly lower tensile strength as compared to ANR. The differences in obtained properties should be claimed by the content of non rubber in rubber composition.