This research was concentrated on characterized mechanical properties and adjusted compatibility of poly (lactic acid) (PLA) with thermoplastic starch (TPS) as biodegradable polymers composites. PLA was blended with TPS at the proportion of 10 20 30 50 and 70 wt% as well as 2 phr chain extender by an internal mixer at 200°C. The blended materials were then injection molded at 230°C. Tensile testing showed that as the amount of TPS increase the elongation at break tended to increase but the tensile strength and modulus tended to decrease. The morphology was investigated by scanning electron microscope. It was found that distinct phase between PLA and TPS was observed. Yet adding the chain extender clearly improved the compatibility between PLA and TPS. The blended materials were also analyzed by differential scanning calorimetry method to study thermal properties. It was found that as the amount of TPS increased the glass transition temperature (Tg) melting temperature (Tm) and cold crystallization temperature (Tcc) deceased. Additionally chain extenders did not affect thermal properties. The thermal stability of the composites decreased when increasing the amount of TPS because of the degradation of TPS in PLA. However when heated at 100ºC for 1 hr the PLA sample bent while TPS did not bend. When PLA was mixed with TPS the composite was bent according to adding TPS.

The aims of this research work were to enhance the impact resistance and processibilty of wheat gluten (WG) by the addition of epoxidized natural rubber (ENR) compared to glycerol. This work was divided into two parts: to study the optimum ENR content for improvement of WG and the effect of together functions between ENR and glycerol on the properties of WG. Tested specimens were mixed and prepared by internal mixer and compression molding machine respectively. ENR and glycerol were varied from 10 to 40 phr. The effects of modifier types and contents on WG were evaluated by tensile impact and water absorption testing and thermal analysis. Fracture behavior and rubber dispersion were investigate with scanning electron microscope (SEM). The result revealed that the increase of ENR or Glycerol contents led to the decreases in tensile modulus and strength except for modifier content of 10 phr whereas elongation at break and impact strength increased. Glass transition temperature (Tg) of modified WG tended to decreased with the increase of ENR or glycerol contents especially for glycerol. The presence of glycerol affected on the decomposition temperature (Td) values but those were unchanged for case of ENR. Water resistant of WG specimen was improved by the presence of ENR whereas the increase of glycerol led to weight loss at immersion time of 2880 min. For the effect of ENR : glycerol ratios it indicated that glycerol enhanced tensile resistances but suppressed impact and water resistances of modified WG by ENR. Sizes and dispersion of ENR particles were improved by the addition of glycerol. Tg and Td values of modified WG by ENR and glycerol increased when ENR fractions were increased.

This research work was to study the toughening modification of polylactic acid by the mixing with epoxidized natural rubber (ENR) and the increase of effectiveness of mechanical properties with a compatibilizer. Enhancement of properties in polylactic acid was evaluated by tensile and impact testings Fourier-transform Infrared Spectroscopy (FTIR) technique Differential Scanning Calorimetry (DSC) technique and Scanning Electron Microscope (SEM). For the addition of ENR it was revealed that the increase of ENR contents improved elongation at break and impact strength but decreased tensile modulus and ultimate tensile strength. Glass transition temperature (Tg) percentage crystallinity and the melting point of polylactic acid tended to decrease with the addition of ENR. Chemical change was found that position of C=O peak in polymer blend was slightly shifted as compared to the spectrum of neat polylactic acid. The optimum formulation for toughening modification was ENR content of 30 wt%. Its impact strength was 1982.55 % of neat polylactic acid. For increasing effectiveness of mechanical properties with a compatibilizer it revealed that the addition of Joncryl ® ADR-4300 as compatibilizer improved both tensile and impact properties. The optimum loading of a compatibilizer for improving mechanical properties was 0.5 wt% of polylactic acid. The decreases of crystallinity and melting point of polylactic acid with adding Joncryl ® ADR-4300 might be because Joncryl ® ADR-4300 was also chain extender of polylactic acid and it might be obstructing crystallization. The presence of Joncryl ® ADR-4300 unaffected on Tg value and chemical change.

This research work was to study the improvement of toughness of polylactic acid (PLA) and the cost reduction of raw material with addition of untreated and treated oil palm fiber (OPF). The detail of this work was divided into two parts. The first was to find the suitable condition for surface treatment of OPF with sodium hydroxide (NaOH). The second part was to study the effect of untreated and treated OPF contents on the mechanical properties of PLA. For surface treatment of OPF NaOH concentrations and immersion times were varied from 0 to 15 wt% and 0 to 30 min respectively. Aspect ratio (L/D) and surface of untreated and treated OPF were investigated by using optical microscope and scanning electron microscope (SEM) respectively. The result suggested that the most suitable condition for surface treatment of OPF was NaOH concentration of 10 wt% at immersion time of 20 min. Treated OPF was occurred microporous and had more rough as compare to untreated fiber. For the effect of untreated and treated OPF contents on the mechanical properties of PLA it was evaluated by tensile and impact testing. SEM was used for investigation of interfacial adhesion and fiber dispersion. The results showed that tensile modulus and impact strength tend to increase with adding 2.5 wt% OPF content and slightly changed at higher OPF content whereas ultimate tensile strength and elongation at break decreased with increasing fiber content. Surface treatment with NaOH led to enhancement of mechanical properties of composite due to improve interfacial adhesion and fiber dispersion.