Papers by Author: Sirijutaratana Covavisaruch

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Authors: Lalintip Boonthamjinda, Nawadon Petchwatana, Sirijutaratana Covavisaruch, Wannee Chinsirikul, Noppadon Kerddonfag
Abstract: Poly(lactic) acid (PLA) is bioplastic produced from corn starch; its brittleness limits the use of PLA in many applications. Biaxial stretching is one approach adopted by film manufacturers to enhance the properties of plastics such as polypropylene (PP). This study aims to produce biaxially-oriented PLA films which had been toughened with 1-10% core-shell rubber (CSR). Differential scanning caloriemetry (DSC) results indicated that all biaxially-stretched neat PLA and the PLA/CSR films possessed nearly 20% greater crystallinity than the as-cast film.The yield stress of the biaxially-stretched films were higher than that of the unstretched films in both machine (MD) and transverse (TD) directions. After biaxial stretching, the elongation at break of the stretched films was still much higher than that of the unstretched ones. The tear resistance was highest in the film with 5 wt% CSR, it became higher after biaxial stretching. The water vapor permeation (WVP) was also minimum in the film with 5 wt% CSR. The biaxially-stretched films had lower WVP than the unstretched ones due to the enhanced crystallization and chain orientation in the stretched films.
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Authors: Sasinee Wiburanawong, Nawadon Petchwattana, Sirijutaratana Covavisaruch
Abstract: This research aims to study the influences of carvacrol essential oil on the tensile properties and antimicrobial activity of food packages prepared from poly (butylene succinate) (PBS). Overall, the tensile strength and tensile modulus of the PBS film decreased with the addition of carvacrol beyond 4wt%. PBS elongated to a greater extent when carvacrol was employed; the elongation reached its maximum level at 19% when carvacrol was added at 10wt%. The water vapor permeation (WVP) and oxygen permeation (OP) of PBS/carvacrol films tended to increase with increasing carvacrol content due to the vaporization of some carvacrol. Carvacrol was found to effectively inhibit microorganism growth; its antimicrobial activity against S.arious growth was evident when 4wt% of carvacrol was compounded with PBS while that against E.coli growth was found only when 10wt% of carvacrol was employed.
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Authors: Naphaporn Lertwongpipat, Nawadon Petchwatana, Sirijutaratana Covavisaruch
Abstract: Bio-based biodegradable Poly (lactic acid) (PLA) suffers limitations such as brittleness and slow crystallization. This study aims to resolve the brittle nature of PLA by blending with Poly (butylene succinate) (PBS), a more ductile biodegradable polymer with superior toughness and flexural properties. In this research, a series of PLA/PBS blends was prepared at the blend ratios of 100/0, 80/20, 60/40, 40/60, 20/80 and 0/100. FTIR showed that there was no change in the functional groups of the PLA/PBS blends. Thermal stability assessed by TGA revealed that PBS degraded at higher temperature than that of PLA; the decomposition temperature (Td) at 10% weight loss of PLA and PBS were 330.8 and 356.4°C respectively. The Td of all the blends increased gradually with the addition of PBS. The flexural properties in terms of the flexural strength and the flexural modulus of the blends reduced significantly with PBS content. The PLA/PBS specimens with greater PBS content were softened and flexed more easily, thereby requiring a much lower flexural strength. The flexural modulus of the 80/20 and 60/40 blends dropped from 3.5 GPa for neat PLA to 3.2 GPa and 2.1 GPa while the flexural strength also declined from 105.3 MPa to 90.9 MPa and 69.1 MPa respectively. The toughness of all the blends was greater than that of neat PLA; in particular the 60/40 blend exhibited superior impact strength of 48.7 J/m compared with 30.9 J/m of the neat PLA. The microscopic images of all the blends showed two distinct phases; the 60/40 blend consisted of well dispersed small particles of the tough PBS, resulting in greater absorption of energy upon impact.
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Authors: Nawadon Petchwattana, Sirijutaratana Covavisaruch, Nukul Euapanthasate
Abstract: Toughening of poly(lactic acid) (PLA) biopolymer by particles of acrylic based core-shell rubber (CSR) was conducted to observe the influences of the rubber contents on the properties of the modified PLA. A series of PLA specimens modified with the CSR by 0.1-10 wt% was prepared by twin screw extrusion and injection. Diminishing brittleness was reflected in the dramatic increment of both the impact strength by threefolds and the elongation at break by fifteenfolds when CSR was employed by 10 wt%. The toughening was also accompanied with a decrease in the tensile modulus and strength. At low loading, the added CSR by 0.5wt% also assisted crystallization of the PLA by slightly lowering the crystallization temperature, allowing decreased processing time and improving the degree of crystallinity of the generally difficult to crystallize PLA.
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Authors: Nawadon Petchwattana, Sirijutaratana Covavisaruch, Chanidapa Watkrut
Abstract: The purpose of this research is to enhance the toughness of richly-filled wood plastic composites (WPC) by using ultrafine acrylonitrile butadiene rubber (NBR) particles. The WPC was prepared by using poly (vinyl chloride) (PVC) matrix filled with Iron wood (Xylia xylocarpa) flour at 40 phr (WPC40) and 60 phr (WPC60). To enhance the impact strength, various contents of the ultrafine NBR were incorporated as an impact modifier from 1-11 phr. Experimental results indicated that the NBR toughened-WPCs were tougher than that of the unmodified ones, by increasing the tensile elongation at break. The impact strength of the WPCs modified with only 5 phr of NBR was notably enhanced around 26 and 7% for WPC40 and WPC60 respectively. Rheological results revealed that the ultrafine NBR functioned not only as an impact modifier but also as a processing aid with shorter processing time and lower melt torque.
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Authors: Nawadon Petchwattana, Sirijutaratana Covavisaruch, Kamolrat Kanawang
Abstract: Wood plastic composites (WPC) prepared from poly(vinyl chloride) (PVC) and Balau wood particles were studied in the current research. Various particles sizes of wood flour with a top cut of 45, 75, 106, 180 and 250 µm was investigated at the range of 0-80 phr. Experimental results indicated that WPC was more stiff and brittle when the Balau wood flour was applied at all compositions. There was no statistically significant difference in the tensile strength and the elongation at break among the composites with different particle sizes. Treating the composites with silane coupling agent induced increments in both the impact strength and the tensile elongation at break.
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