Papers by Keyword: Poly(lactic acid) (PLA)

Abstract: Nanocomposite is one of the most favorable approaches to improve mechanical properties of polymers. This study prepared polymer composite of PLA and LLDPE with different amount of rice husk silica (0.5 and 1 wt%). The composites were prepared by melt-mixing in a twin-screw extruder and processed into film by a chill roll cast extruder. The mechanical properties were investigated through tensile testing and tear testing. The result show that the tensile modulus of PLA decreased with 1wt% rice husk silica. Similarly, tensile modulus of LLDPE dropped with the addition of silica. However, with the addition 0.5 and 1 wt% rice husk silica, the elongation at break of PLA and LLDPE composites increases significantly.

Abstract: Poly (lactic acid) or PLA is one of the most promising biodegradable and bio-based materials commercially available for the manufacturing of environmentally friendly plastic products. Although, PLA has high modulus and biodegradable property, its brittleness and low thermal stability are the disadvantages. Several means have been explored so as to overcome this drawback, i.e. copolymerization, addition of some additives as well as blending with other polymers. The polymer blending technique has attracted the most attention because of its simplicity and economical reason. It was reported that the addition of a polyolefin elastomer e.g. poly (ethylene-co-octene) or POE in PLA matrix can effectively improve its brittleness. The aim of this study is thus to investigate the effect of the amount of POE on mechanical properties of the polymer blends. POE was also modified with glycidyl methacrylate in order to improve the compatibility between the two polymers. The results pointed out that the impact strength of PLA markedly increased while tensile and flexural properties of the blends were slightly lower than that of neat PLA. It was also observed that the tensile and flexural properties were slightly higher when the modified POE was used rather than those with unmodified POE which indicated the improved interfacial compatibility between two polymers.

Abstract: Graphene nanoplatelets (xGnP) were investigated as a novel nanoreinforcement filler in poly (lactic acid)(PLA)/poly (ethylene glycol)(PEG) blends by melt blending method. The prepared nanocomposites exhibited a significant improvement in tensile properties at a low xGnP loading. The tensile properties demonstrated the addition of 0.3wt% of xGnP led to an increase of up to 32.7%, 69.5% and 21.9% in tensile strength, tensile modulus and elongation at break of the nanocomposites respectively, compared to PLA/PEG blend. The nanocomposites also shows enhanced thermal stability compared with PLA/PEG blend in thermogravimetry analysis (TGA). Scanning electron microscopy (SEM) image of PLA/PEG/0.3wt% xGnP displays good uniformity and more homogenous morphology.

Abstract: An environmental friendly slow-release urea fertilizer with double films (SUFDF) was prepared by using dialdehyde starch urea resin (DASU) as inner coating and polylactic acid (PLA) as outer materials. The structural, chemical characteristics and morphology of the SUFDF were characterized by FTIR, element analysis and SEM. Its efficiency in slowing the nitrogen release was examined via soil leaching and pot experiments. The experimental results indicated that the introduction of hydrophobic PLA and DASU reduced the swell ability of the fertilizer, which made it can provide nitrogen persistently at the early farming. After the urea dissolved, the DASU in the fertilizer would continue to release nitrogen due to its good slow-release property. So this fertilizer would have potential applications in modern agriculture and horticulture.

Abstract: This paper deals with the evaluation of crystalline structure and thermal properties of injection molded parts based on polylactic acid (PLA) matrix reinforced by banana and hemp natural fibres (NF). Using differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) methods were evaluated thermal properties and crystalline structure of PLA/NF composites, depending on the amount of natural fibres within the weight ratio of 10% up to 30%. We observed that hemp and banana fibres work like natural nucleating agents and thus subsequently improve the material properties of PLA. We also observed process of melt (primary) and cold (secondary) crystallization of PLA/NF composites depending on cooling rate.

Abstract: Nowadays the use of biodegradable plastic in the food industry has increased dramatically. Because of its outstanding characteristics, i.e. environmental friendliness and non-toxicity, researchers are interested in studying how to improve the properties of plastic, especially polylactic acid or PLA, which is very fragile and intolerant to high impact force. Attempts have been made to improve the weak points of PLA by mixing PLA with epoxidized natural rubber. The natural rubber goes through an epoxidation process, resulting in epoxidized natural rubber (ENR) as the finished product. ENR contains epoxy groups which can efficiently react with PLA. Ratios of PLA and ENR employed in this study were 50:50, 60:40, 70:30, 80:20 and 90:10. In addition to finding a suitable ratio between PLA and ENR, the mixtures were subjected to migration tests according to the guidelines specified in European Commission Regulation (EU) No 10/2011 in order to prove whether the mixed materials are safe and suitable for consumer use. Migration testing was conducted by soaking samples in four different food simulants – 10% (v/v) ethanol in aqueous solution, 3% (w/v) acetic acid in aqueous solution, 20% (v/v) ethanol in aqueous solution and vegetable oil – for 24 h at 40 °C. The results showed that the PLA/ENR blends at every ratio had an overall migration amount of less than 10 mg/dm² in three of the sample simulants, while the overall migration from materials soaked in vegetable oil exceeded this standard. Migration tests of one of the sample blends conducted at 100 °C for 2 h showed similar results. In conclusion, polymer blends of PLA and ENR are appropriate for food packaging applications, but are not appropriate for foods containing vegetable oil.

Abstract: This thesis is mainly about modifying PLA with PA6 as compatilizer and blending PLA with PA6. The alloying of PLA and PA6 can change the original fragility and mutability of PLA, and therefore improve its mechanical property. The blending of PLA into PA6 decreases the water absorbability and light resistance of PA6. Since PLA is of high cost, the blending of PA6 can lower the cost.

Abstract: Thermoplastic starch (TPS)/poly (lactic acid) (PLA) blend and thermoplastic starch (TPS)/poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blend were prepared by melt blending method. PLA grafted with maleic anhydride (PLA-g-MA) was used as a compatibilizer to improve the compatibility of the blends. As TPS was incorporated into PLA, elongation at break was increased while tensile strength, tensile modulus, and impact strength were decreased. Tensile properties and impact properties of TPS/PLA blend were improved with adding PLA-g-MA indicating the enhancement of interfacial adhesion between PLA and TPS. With increasing PBAT content, elongation at break and impact strength of TPS/PLA blends were improved. The addition of TPS decreased glass transition temperature (T_g), crystallization temperature (T_c), and melting temperature (T_m) of PLA. T_g and T_c of TPS/PLA blend were decreased by incorporating PLA-g-MA. However, the presence of PBAT reduced T_c of TPS/PLA blend. Thermal properties of TPS/PLA/PBAT blends did not change with increasing PBAT content. SEM micrographs revealed that the compatibilized TPS/PLA blends exhibited finer morphology when compared to the uncompatibilized TPS/PLA blend.

Abstract: Sawdust/poly (lactic acid) (PLA) composites toughened with poly (butylene adipate-co-terephthalate) (PBAT) were prepared using a melt blending process. Mechanical, thermal and morphological properties of the composites were investigated. With the addition of PBAT into the sawdust/PLA composite, elongation at break and impact strength increased whereas tensile strength and tensile modulus decreased. In addition, thermal stability of the PLA composite improved with the presence of PBAT. Maleic anhydride grafted poly (lactic acid) (PLA-g-MA) was used as a compatibilizer to improve the compatibility of sawdust/PLA/PBAT composites. The compatibilized composites showed higher mechanical properties and thermal decomposition temperatures than that of the uncompatibilized composite due to improved interfacial adhesion between constituents of the composites. The optimum content of PLA-g-MA for sawdust/PLA/PBAT composites was 5 wt%. SEM micrographs revealed some features of ductile fracture in the composites toughened with PBAT and confirmed that PLA-g-MA improved the compatibility of the composites.

Abstract: Surface hydrophobicity of poly (lactic acid) have raise the concerns of surface incompatibility of PLA to function as biomaterial. Thus, various approaches have been made to improve the surface hydrophilicity of PLA. In the present paper, PLA materials were surface modified by alkaline hydrolysis. The indication of the reduction in water contact angle value, from 65 ̊ to 50 ̊ and 15 ̊, in 0.01M and 1M alkaline concentration respectively, proven surface hydrophilicity of PLA film was improved. Further alkaline treatment after 24 hours shows not significant reduction in contact angle. Whereas, the erosion of film surfaces treated under 1M alkaline solution have been observed under polarized optical microscopy. Intrinsic viscosity measurement was also conducted to monitor the surface treatment process. As a whole, surface treatment was successful and sufficient when no further decreased in contact angle value, thus prevent extensive surface erosion.