Chanchai Thongpin

Improvement of Structural and Thermal Stabilities of PVC and Wood/PVC Composite by Zn and Pb Stearates, and Zeolite

Three different chemical stabilizers were introduced into neat PVC and a wood/PVC composite (containing 50 phr wood flour) to improve their thermal and structural stabilities. The changes in CIE yellowness index, polyene index, %wt loss, and decomposition temperature (Td) were monitored. The effects of type and content of thermal stabilizers, thermal ageing time, and the presence of wood flour were our main interests. The experimental results suggested that the additions of Zn and Pb stearates into PVC and wood/PVC composite could improve the thermal stability of the PVC. At the test temperature of 177°C, the additions of Zn and Pb stearates could improve the thermal stabilities of PVC by retarding the upzipped reaction and by reducing the conjugated double bonds in PVC, Pb stearate being the most suitable for thermally stabilizing the PVC. Around the Td range (∼264°C), the addition of Zn stearate reduced the Td value of PVC whereas that of Pb stearate had no effect on the change in Td value. Zeolite loading could shift the Td value of the PVC from 264 to 280°C. The addition of wood particles increased the polyene content and decreased the decomposition temperature of the PVC. The effect of wood flour on the thermal and structural changes of PVC overruled that of thermal stabilizer loading.

The Effect of Excess Silane-69 Used for Surface Modification on Cure Characteristic and Mechanical Properties of Precipitated Silica Filled Natural Rubber (PSi/NR)

This research is concentrated on the effect of concentration of silane-69 used for surface modification on precipitated silica (PSi), on cure characteristic and mechanical properties of PSi filled NR. The PSi content in this study was fixed at 20 phr in order to reveal the effect of silane used to modify PSi, on NR compound and vulcanizate. Moving Die Rheometer (MDR) was used to characterize cure characteristic of rubber compounds. Generally, scorch and cure time of NR would increase with the addition of PSi due to the absorption of accelerator on its surface whereas the addition of Si-69 modified PSi would reduce both scorch and cure time. It was found in this research that the excess amount of Si-69 used increased scorch and cure time of rubber compounds. This was thought to be that the excess of Si-69 led to the formation of polysiloxane clusters which could absorb accelerator in rubber compound and resulted in a prolonged scorch and cure time. In term of vulcanized rubber, it was found that maximum torque increased with the concentration of Si-69 up to 6 %. The polysiloxane formed during the cure characterization test was responsible for the slightly decreased torque after 6% of Si-69 treatment. Nonetheless, even with high concentration of Si-69 used, torque was still higher than that of untreated PSi filled NR. This is widely understood that sulfur atoms in Si-69 molecule are able to participate in the bonding between rubber and silane molecules resulted in the enhancement of crosslink density of the vulcanizate rubber. The increased of modulus at 200 % elongation, tensile strength under tension, with the silane concentration, was evidence of the crosslink enhancement. Tear strength and hardness of the vulcanizates exhibiting the increment, with the silane used, also clearly confirmed the bonding between Si-69 and rubber molecules. It was elucidated from the research that excess of Si-69 would lead to polysiloxane formation, cluster form of silane and crosslinking density. Scanning Electron Microscope (SEM) micrographs and swelling test are also presented to confirm the phenomena.

The Effect of Second Filler on Cure Characteristic and Mechanical Properties of Si-69 Treated Precipitate Silica/NR Composite

Silica has been widely used as non-black reinforcing filler, however, the filler-filler interaction has been an important issue. Cure characteristic and mechanical properties of the rubber compound and rubber vulcanizate were affected both by filler-rubber interaction and filler-filler interaction. There have been, presently, a number of natural fillers which are also used as fillers for the rubber, i.e. fly ash, sawdust and zeolite. This work therefore will study the effect of second filler added into the 13% Si-69 treated precipitate silica (PSi) filled natural rubber compounds. It was revealed that the scorch and cure time of the rubber compound increased with the content of treated PSi. This was the effect of excess of the silane treated onto PSi which would agglomerate and form the cluster of polysiloxane and would then be able to absorb vulcanizing accelerator resulting in extending the scorch and cure time of the rubber compounds. However, this effect was over ruled with the reinforcing effect as could be seen by the increasing, with the contents of PSi, of maximum torque and mechanical properties of the vulcanizates. The NR compounded with treated PSi content of 20 phr selected to study the effect of excess silane on the cure characteristic of hybrid fillers NR composite. The addition of sawdust led to longer scorch time and cure time but not much change of the maximum torque. As expected, the modulus of the rubber vulcanizate increased with the sawdust content whereas the tensile strength and elongation at break decreased with the sawdust content. The incorporation of zeolite could accelerate the cure reaction therefore both scorch time and cure time decreased. The maximum torque also increased with the content of zeolite. Both modulus and tensile strength increased with the content of the zeolite whereas elongation at break tended to be unchanged. In the case of using fly ash as the second filler, the cure time tended to be unchanged. However, the maximum torque tended to be increased with the content of fly ash. It was found that the modulus, tensile strength increased but elongation at break decreased. Interestingly, the excess of Si-69 used effect pronouncedly for the addition of zeolite and fly ash cases as the excess silane could promote the interaction between fillers surface and rubber molecule accept for sawdust

The Modification of Asphalt Emulsion Using Pre-Vulcanized Natural Rubber Latex for Highway Application

Asphalt emulsion is manufactured by emulsification of asphalt, and it is an energy-saving, ecologically safe material because it does not need any heating processes which can emit gas and fire hazard in its use. The purpose of this study is to elucidate the feasibility on using pre-vulcanized natural rubber latex as an admixture for asphalt emulsion in order to improve thermal stability and useful mechanical properties of the asphalt emulsion. The crosslink density was determined by swell ratio. The effect of vulcanizing agent on residue properties of modified asphalt emulsions was studied. The morphology properties of the modified asphalt were also investigated by using an optical microscope. The results showed that asphalt emulsion which was modified using pre-vulcanized NR latex could provide a standard asphalt emulsion and applicable for highway construction application. The mechanical and physical properties of the dried asphalt emulsion were also very well modified by the vulcanized rubber phase. The residue properties of modified asphalt with natural rubber and pre-vulcanized natural rubber latex, including softening point and penetration was improved. The increase in vulcanizing agent could also increase softening point. At low polymer contents, the samples reveal the existence of dispersed polymer particles in a continuous bitumen phase, whereas at high polymer contents a continuous polymer phase was observed.

Cure Characteristics, Morphology and Mechanical Properties of Partially Cured NBR Blended with NR

This research is aimed to study the effect of partially cured acrylonitrile butadiene styrene rubber (NBR) blended with natural rubber (NR) and vulcanized with sulfur system. The research started with compounding NBR with zinc chloride, ZnCl2 in an internal mixer. The cure characteristic of the NBR compound was investigated using moving die rheometer (MDR). The compound NBR is then blended in NR at 160 °C. The temperature was then lowered to 50 °C before the addition of sulfur cure additives. Cure characteristic of the rubber blends were investigated and found that the increasing of NBR caused shortened in scorch time. Rubber blends morphology was investigated using SEM. NBR was found dispersed in NR phase. The particle size of dispersed NBR was increased with its content. This is due to high viscosity of NBR and hence larger particles will be obtained. The de-bonding at the interface was shown in SEM micrograph. The compound is then filled with fragrance absorbed fumed silica. The fragrance silica was added during milling of NBR and NR. The releasing behavior of fragrance was found dependent upon NBR/NR ratio.

Bioplastics from Blends of Cassava and Rice Flours: The Effect of Blend Composition

Abstract Bioplastics from melt-mixing of cassava flour, rice flour and their blends with compositions of between 0/100 and 100/0 %wt were successfully obtained using twin-screw extrusion and compression molding processes. The influence of blend composition on the bioplastics properties was studied. It was found that the flour blends were uniformly mixed. The tensile properties and dynamic properties of the flour bioplastics were examined. The tensile strength and storage modulus of compression molded bioplastics based on rice flour was greater than those of the cassava flour, but their flexibility was lower. The tensile strength and storage modulus of the flour blend bioplastics increased with increasing rice flour content. The flour bioplastics showed two glass transitions, one corresponding to glycerol rich phase and the other corresponding to plasticized starch. For plasticized flour blends, the glass transitions were not affected by the blend composition. The improvement in the mechanical properties of the bioplastics produced from the cassava/rice flour blend could be explained by an increase in the crystallinity level resulting from the higher concentration of rice flour. Using flour blends derived from cassava and rice flours, the bioplastics developed in this study offer a greater performance while maintaining environmental compatibility and sustainability, which allows for a substitution of tradition bioplastics from cassava starch.

The Effect of Organic Modificaition Method onto Montmorillonite on Mechanical Properties of Natural Rubber

Montmorillonite is a type of clays that has been used to reinforce polymer including rubber. Therefore this research is aimed to modify mechanical properties of natural rubber (NR) using montmorillonite (MMT) comparing with the organic modified montmorillonite (CTAB-MMT) and organic molecule grafted MMT. The affect of MMT, CTAB-MMT and HTMS-g-CTABMMT on cure characteristics of NR were studied. It was found from the research that the increase of MMT content could prolong the scorch time whereas CTAB-MMT and HTMS-g-CTABMMT could shorten the scorch time. The cure times of the compounds in all cases were not much different. In term of mechanical properties, modulus, tensile strength and tear strength of NR/HTMS-g-CTABMMT vulcanizate were higher than those of NR/MMT and NR/CTAB-MMT vulcanizates. Meanwhile, elongation at break of the NR/ HTMS-g-CTABMMT vulcanizate decreased more than the latter cases

Effect of ENR Contents on Cure Characteristic and Properties of NR/ENR/EVA Foam

This research studied foaming of natural rubber (NR), epoxidized natural rubber (ENR) and ethylene vinyl acetate copolymer (EVA) blends vulcanizate. The contents of NR/ENR/EVA investigated were 60/10/30, 70/10/20, 50/20/30 and 60/20/20 to keep NR based to 70 and 80 % by weight whereas EVA contents were 20 and 30 % by weight. ENR used in this research was ENR 50. The content of ENR was varied as 10 and 20 % by weight with restpect to total polymer content. The Efficient vulcanization and peroxide systems were used for rubber vulcanization in order to cure both rubber and EVA. Oxydibenzenesulfonyl hydrazide (EW or OBSH) was used as foaming agent. The results showed that rubber blends with 20% ENR tended to show better compatibilization between NR and EVA. The viscosity of rubber blend which indicated by minumum torque was increased with the content of ENR. Cell size of rubber blends foam containing ENR 20 % showed rather normal distribution than ENR 10%. Foam with high content of NR based rubber showed slightly higher density than the other systems. Tensile properties of rubber blends foam were dependent upon NR based contents and compatibility between NR and EVA. Rubber blends foam with high ENR content showed higher specific secant modulus. The specific tensile strength and elongation at break were slightly inferior. The specific tear resistance of the rubber foam was independent on compatibility. High EVA content reduced both specific compressive modulus and compressive strength of the foam. For the foam that contained EVA domain showed permanent deformation and hence high in compression set. Compatibilized rubber blend foams and the foam with high EVA possessed low ball rebound resilience.

In Situ Reinforcement of PLA Using Nylon 6 in PLA/Nylon 6 Extrudate Blend via Twin-Screw Extrusion

This research was aimed to study the possibility of in-situ reinforcement of PLA by elongated Nylon 6 in PLA/Nylon 6 blend during elongating of PLA/Nylon extrusion. PLA was melt blending with Nylon 6 in a twin screw extruder with various compositions i.e. 5, 10, 15 and 20 % of Nylon 6. The extrudate was drawn after leaving extrusion orifice die of 3 mm in diameter, with the pulling speed of 12 cycles per minute. The extrudate gauge length 15 cm were used to perform tension test in order to investigate tensile properties. The blending between PLA and Nylon 6 with 11 phr of benzene sulfonamide (BSA), based on Nylon 6, as a plasticizer was also investigated at the same PLA/Nylon 6 blend ratios. The extrusion used conditions were also the same. Tension was also performed onto the extrudates with the gauge length 15 cm. Thermal degradation was also investigated. The SEM micrographs of blends in the longitudinal direction of PLA/Nylon 6 extrudate showed elongated of Nylon 6 in PLA matrix phase. The elongated of Nylon 6 phase in PLA matrix phase was found very clear in the plasticized blends. This phenomenon clearly occurred for the blends composition of both 95/5 and 90/10, with and without plasticizer. The results also showed that Young’s modulus of the blends with 5 % Nylon 6 was increased about 10 % whereas at 10 % nylon 6, the modulus was not significantly different from neat PLA. With the addition of plasticizer, nylon 6 was elongated more than that in the blend with un-plasticized Nylon 6. Due to the lack in interfacial adhesion, shown by SEM micrograph, tensile strength was found to be decreased. As expected, the elongation at break under tension was increased with the content of nylon 6. This was due to the toughening effect of elongated Nylon 6. Thermal stability, notified by degradation temperature of PLA, Td, was found to be improved. This was due to the high thermal stability of nylon 6. The results from the research can inform that the elongated nylon 6 phase in PLA matrix can perform as fibrous reinforcement. At high content of nylon 6, i.e. 15 and 20 %, the elongation of nylon 6 was rather difficult due to the less matrix phase and low shearing between PLA and nylon 6. Phase compatibility improvement could be the factor to improve the in-situ reinforcement.

Cure Characteristic and Mechanical Properties of Epoxidized Natural Rubber/Chloroprene (ENR/CR) Blends

Epoxidized Natural rubber (ENR) with the epoxide content of 40 % was prepared and blended with various contents of chloroprene rubber (CR) and 50 phr of carbon black. The cure characteristic, mechanical properties and the effect of gasohol E-85 on the mechanical properties of the rubber vulcanizate were studied. It was revealed from cure characteristic results, tested by Moving Die Rheometer (MDR), that minimum torque of the rubber compounds increased with the content of CR whereas maximum torque tended to increase at the content of 10 phr and decrease after this content, of which the values agreed well with the modulus at 100% elongation in rubber vulcanizates. Considering characteristic scorch and cure time, the values increased with the CR contents. It was clear from the result that at the ENR:CR ratio of 90:10, modulus of 100% elongation and tear strength exhibited the highest values. It was also found that the mechanical properties of the blend vulcanizates were slightly suffered by gasohol E85 except for tear strength. It was understood that this must be because of the effect of the phase continuity and crosslinking that occurred differently in two phases. The phase morphology of the blends were also investigated and reported in the research.