This research aimed to study the production of a biodegradable film from Jicama starch (Pachyrhizus erosus (L.) Urbar) for plant bag application. The film was prepared by dissolving Jicama starch in water to the concentration of 5 wt%. To study the effect of the glycerol content the glycerol was added at 6 levels; 0 10 20 30 40 50 and 60 wt%. The film was casted in a molded and dried at 60 oC for 24 h. After drying properties of films; thickness water activity (aw) solubility tensile strength (TS) elongation (%E) puncture strength and the degradation of the films were evaluated. The thickness of the films was in the range of 0.16-0.28 mm. The aw of films ranged from 0.36-0.49. The water vapor permeability water solubility and flexibility of the film increased with the increasing of glycerol content. Tensile and puncture strength of the starch films tended to increased when the glycerol content decrease. After the films were buried under the ground (8-10 cm depth) for 12 weeks they were degraded by 100%. The Jicama starch film with 40 wt% glycerol showed the best overall properties.

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.

This research work was to study the improvement of toughness and impact resistance of polylactic acid (PLA) with modified soybean oil (MSBO) and palm fiber (PF). The detail of this work was divided into three parts. The first was to find the suitable condition for modification of soybean oil with ozonolysis. The second and last parts were to study the effects of MSBO and PF contents on the properties of PLA respectively. For oil modification the reaction times were varied from 0 to 3 hours and the chemical changes in molecules of soybean oil were investigated by Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. The result suggested that the most suitable condition for ozonolysis reaction was 2 hours considering the decrease in double bond between carbon atoms and the increase in hydroxyl group into molecular structure of MSBO. For the effect of MSBO content on mechanical properties it was evaluated by tensile and impact testing. Differential scanning calorimeter (DSC) and scanning electron microscope (SEM) were used for thermal and morphology analyses. The result showed that elongation at break and impact strength of modified PLA by MSBO increased about 89 and 25 % compared to those of neat PLA respectively. MSBO act as the efficient plasticizer for PLA considering the conversion of fracture behavior from brittle to ductile good dispersions of MSBO droplets in PLA and the decrease of glass transition temperature (Tg) with addition of MSBO. The addition of PF improved the impact strength of modified PLA. Strong interfacial bonding between PLA and PF indicated MSBO being both coupling agent for PLA and natural fiber and plasticizer for PLA. For migration test it was found that contents of released heavy metal and migrated chemical from specimens of PLA and PLA/PF composite were under the criteria according to Notification of the Ministry of Public Health (No. 295) B.E. 2548.