Chih-Yuan Tsou

Preparation and Characterization of Bioplastic-Based Green Renewable Composites from Tapioca with Acetyl Tributyl Citrate as a Plasticizer

Granular tapioca was thermally blended with poly(lactic acid) (PLA). All blends were prepared using a plasti-corder and characterized for tensile properties, thermal properties and morphology. Scanning electron micrographs showed that phase separation occurred, leading to poor tensile properties. Therefore, methylenediphenyl diisocyanate (MDI) was used as an interfacial compatibilizer to improve the mechanical properties of PLA/tapioca blends. The addition of MDI could improve the tensile strength of the blend with 60 wt% tapioca, from 19.8 to 42.6 MPa. In addition, because PLA lacked toughness, acetyl tributyl citrate (ATBC) was added as a plasticizer to improve the ductility of PLA. A significant decrease in the melting point and glass-transition temperature was observed on the basis of differential scanning calorimetry, which indicated that the PLA structure was not dense after ATBC was added. As such, the brittleness was improved, and the elongation at break was extended to several hundred percent. Therefore, mixing ATBC with PLA/tapioca/MDI blends did exhibit the effect of plasticization and biodegradation. The results also revealed that excessive plasticizer would cause the migration of ATBC and decrease the tensile properties.

Biodegradable composition of poly(lactic acid) from renewable wood flour

Maleic anhydride-grafted poly(lactic acid) (PLA-g-MAH) was prepared by blending with wood flour (WF). The effect of MAH and WF inclusion on the mechanical and thermal properties of the composites was examined. PLA-g-MAH/WF had optimum tensile properties compared with PLA/WF. Scanning electron microscopic images indicated poor interfacial adhesion of the PLA/WF. It was enhanced after MAH was grafted onto PLA; the PLA-g-MAH/WF showed excellent compatible morphology. Results also revealed that the biodegradation of PLA and PLA-g-MAH was improved with increasing of WF content.

Biocompatibility and characterization of polylactic acid/styrene-ethylene-butylene- styrene composites

Polylactic acid (PLA)/styrene-ethylene-butylene-styrene (SEBS) composites were prepared by melt blending. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WXRD) were used to characterize PLA and PLA/SEBS composites in terms of their melting behavior and crystallization. Curves from thermal gravimetric analysis (TGA) illustrated that thermostability increased with SEBS content. Further morphological analysis of PLA/SEBS composites revealed that SEBS molecules were not miscible with PLA molecules in PLA/SEBS composites. The tensile testing for PLA and PLA/SEBS composites showed that the elongation at the break was enhanced, but tensile strength decreased with increasing SEBS content. L929 fibroblast cells were chosen to assess the cytocompatibility; the cell growth of PLA was found to decrease with increasing SEBS content. This study proposes possible reasons for these properties of PLA/SEBS composites.

Preparation and characterization of biodegradable polyurethanes composites filled with silver nanoparticles-decorated graphene

In this study, polyurethane (PU) was synthesized using 4,4,-diphenylmethane diisocyanate (MDI) as a hard segment, polycaprolactone diol (PCL) as the soft segments and 1,4-butandiol (1,4-BD) as a chain extender. Nanosilver/graphene (Ag/G) was added to the PU matrix to prepare Ag/G/PU nanocomposites. EDS, SEM and XRD are used for assaying the silver content and characterization of Ag/G. TEM, FT-IR, XRD and EDS were used to characterize the structure and morphology of the Ag/G/PUs nanocomposites. The TEM results show that Ag/G belongs to sheet structures and is dispersed in a PU matrix. The SEM showed that the strong interfacial adhesion between the Ag/G and PU is indicated. FT-IR spectra analysis shows that the functional group of PU is free of obvious changes by adding a small amount of Ag/G in the PU matrix. XRD results showed that the main crystalline peak (26°) of Ag/G became more apparent with increasing content of Ag/G, and EDS showed that the content of Ag increased with increasing content of Ag/G in the Ag/G/PUs nanocomposites. The thermal stability and mechanical properties of Ag/G/PUs nanocomposites are improved with increasing content of Ag/G. Contact angle and AFM results showed that the hydrophobicity and surface roughness increased with increasing content of Ag/G. Moreover, the Ag/G/PUs nanocomposites exhibit antibacterial activities toward Staphylococcus aureus as well as Escherichia coli and their antibacterial rates increase with increasing Ag/G. In addition, the electrical conductivity measurements showed that both surface and volume resistance of the Ag/G/PUs nanocomposites decreased as the amount of Ag/G increased.

The Properties and a New Preparation of Ethylene Propylene Diene Monomer/Montmorillonite Nanocomposites

In this study, ethylene propylene diene monomer (EPDM)/organic clay nanocomposites were prepared using melt intercalation to explore how the nanoclay affected their structures and mechanical and thermal properties. Montmorillonite (MMT) modified with hydrochloric acid (HCl) and maleic anhydride (MAH) was employed to improve the compatibility of the EPDM and MMT phases. The effects of the modified clay on the properties of the EPDM were compared with those of commercially available MMTs (Clay10A and Clay30B) synthesized using an alternative modifier. The nanoclay structures of the EPDM/clay nanocomposites were characterized using X-ray diffraction (XRD), and their thermal and mechanical properties were examined a using thermogravimetric analysis (TGA) and universal tensile testing machine. MMT spacing can be increased with the addition of hydrochloric acid and maleic anhydride (MAH). The XRD results showed no diffraction peak for the EPDM and modified MMT (ClayMAH) composites, verifying that the MMT was exfoliated. The TGA results showed that the thermal decomposition temperature and the residual can be enhanced by increasing the ClayMAH content, the pyrolysis temperatures of EPDM/ClayMAH, EPDM/Clay10A, and EPDM/Clay30B are similar because of the barrier effect phenomenon. The mechanical properties can also be improved with additional ClayMAH content because the clay is dispersed in EPDM. A decline in the crosslinking density increases the slidability between polymers, which enhances the mechanical properties of the nanocomposite. ClayMAH is more effective for improving the tensile property compared to Clay10A and Clay30B.

Crystallization behavior and tensile property of poly(trimethyleneterephthalate)/styrene-ethylene-buthylene-styrene composites

Poly(trimethyleneterephthalate) (PTT)/styrene-ethylene-buthylene-styrene (SEBS) composites were prepared by melt compounding. Polarizing optical microscopy was used to observe the spherulitic morphology and the crystal structure of PTT and PTT/SEBS composites. Scanning electron microscopy was used to determine the dispersion and the compatibility of fracture surfaces of PTT and SEBS. The curves of thermal gravimetric analysis illustrated that the thermo stability decreased with increasing SEBS content. Differential scanning calorimetry was used to investigate the crystallization behavior; and the result showed that the glass transition temperature of the compound increased with the SEBS content. The Avrami equation described the isothermal crystallization kinetics. Stress-strain curves for PTT and PTT/SEBS composites showed that the elongation at break was enhanced with increasing SEBS content.

Isothermal Crystallization Kinetics Effect on the Tensile Properties of PLA/PTT Polymer Composites

A poly(lactic acid)/poly(trimethylene terephthalate) (PLA/PTT) composite was prepared by melt blending to improve the PTT crystallization rate. Morphology analysis of PLA/PTT fractured surfaces demonstrated the compatibility of its components. Thermogravimetric analysis revealed that the thermodegradation of a PLA/PTT sample was higher than that of PLA. Differential scanning calorimetry was used to evaluate the crystallization behavior. The Avrami equation described the isothermal crystallization kinetics. The Hoffman–Weeks parameters indicated that the PLA presence increased slightly the PTT nucleation. The tests of PLA, PTT, and PLA/PTT specimens in tension showed that a percent elongation of the PLA/PTT composite was between that of PLA and PTT; however, the tensile strength of the PLA/PTT composite was similar to that of PLA.