Chin-San Wu

Study on the Crystallization, Miscibility, Morphology, Properties of Poly(lactic acid)/Poly(ε-caprolactone) Blends

A series of blends of poly(lactic acid) (PLA) and poly(ϵ-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA70PCL30 blend. This result reveals that the PLA70PCL30 blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the Tg. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA70PCL30 blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL.

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.

Study on the Crystallization Kinetic and Characterization of Poly(lactic acid) and Poly(vinyl alcohol) Blends

In this study, poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) blends, with PLA/PVA mass ratios of 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60, were prepared by means of the melt blending method. The result of torque measurements and thermal gravimtric analysis tests showed that the addition of PLA can decrease the melt viscosity of PVA and that the second degradation step of PVA nearly disappeared for the PLA80/PVA20 blend. The absorbance peaks of the carbonyl group and the hydroxyl group in the Fourier transform infrared spectra of PLA/PVA blends had significant shifts to lower wave numbers, indicating that there were interactions between these two groups. Combined with the result of the differential scanning calorimetry curves, this interaction would be favorable for improving miscibility. The X-ray diffraction patterns and the polarized light microscope (PLM) micrographs showed that PVA can serve as a nucleating agent to promote the crystallization of PLA in PLA/PVA blends. Moreover, the PLA80/PVA20 blend gave the highest growth rate of PLA spherulite.

Study on the Preparation and Characterization of Biodegradable Polylactide/SiO2–TiO2 Hybrids

In this study, the silicic acid produced from sodium metasilicate hydrate and titanium tetraisopropylate were chosen as the ceramic precursors for the modification of biodegradable polylactide (PLA) through an in situ sol-gel process and the melt blending method. In addition, acrylic acid grafted polylactide (PLA-g-AA) was studied as an alternative to PLA. Hybrids were characterized by Fourier transform infrared spectroscopy, 29 Si solid-state nuclear magnetic resonance (NMR), thermogravimetry analysis (TGA), scanning electron microscope (SEM), and Instron mechanical tester. The result was that properties of the PLA-g-AA/SiO2–TiO2 hybrid were superior to those of the PLA/SiO2–TiO2 hybrid. This was because the carboxylic acid groups of acrylic acid acted as coordination sites for the silica-titania phase to allow the formation of stronger chemical bonds. The 29 Si solid-state NMR showed that Si atoms coordinated around SiO4 units were predominantly Q3 and Q4. The 10 wt.% SiO2–TiO2 content gave the maximum values of tensile strength and glass transition temperature in PLA/SiO2–TiO2 and PLA-g-AA/SiO2–TiO2 both because excess SiO2–TiO2 particles caused separation between the organic and inorganic phases.

Antibacterial activity and in vitro evaluation of the biocompatibility of chitosan-based polysaccharide/polyester membranes

The antibacterial activity and biocompatibility of membranes of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and chitosan (CS) (PHBV)/CS) were evaluated in this study. Maleic anhydride (MA)-grafted polyhydroxyalkanoate (PHBV-g-MA) was evaluated as an alternative to PHBV. Mouse tail skin fibroblasts (FBs) were seeded on two series of these films to assess cytocompatibility. Collagen and cell proliferation analyses indicated that PHBV, PHBV-g-MA and their composite membranes were biocompatible with respect to FB proliferation. However, FB proliferation, collagen production and the percentage of normal cells growing on PHBV/CS membranes were greater than those for PHBV-g-MA/CS membranes. Cell-cycle and apoptosis assays by FBs on the PHBV-series membrane samples were not affected by DNA content related to damage; i.e. rapid apoptosis/necrosis was not observed, demonstrating the potential of PHBV/CS or PHBV-g-MA/CS membranes for biomedical material applications. Moreover, CS-based polysaccharide enhanced the Escherichia coli (BCRC 10239) antibacterial activity of the membranes. Membranes of PHBV-g-MA or PHBV containing CS-based polysaccharide had better antibacterial activity.

The compatible and mechanical properties of biodegradable poly(Lactic Acid)/ethylene glycidyl methacrylate copolymer blends

The Fourier transform infrared results suggest that the carboxylic acid groups of poly(lactic acid) (PLA) molecules react with the epoxy groups of molecules of Ethylene Glycidyl Methacrylate Copolymer (EGMC) during the reactive extrusion processes of PLAxEGMCy specimens. The tensile and tear strength values of PLAxEGMCy blown-film specimens in machine and transverse directions improve significantly, and reach their maximal values as their EGMC contents approach an optimum value of 6 wt.%. The melt shear viscosity values of PLAxEGMCy resins, measured at varying shear rates, are significantly higher than those of the PLA resin, and increase consistently with their EGMC contents. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) of PLA and PLAxEGMCy specimens reveal that the percentage crystallinity, peak melting temperature, and onset re-crystallization temperature values of PLAxEGMCy specimens reduce gradually as their EGMC contents increase. In contrast, the glass transition temperatures of PLAxEGMCy specimens increase gradually in conjunction with their EGMC contents. Demarcated porous morphology with several connected fungi-decomposed cavities was found on the surfaces of the PLAxEGMCy specimens after being buried for specific amounts of time, in which the sizes of the fungi-decomposed cavities found on the surfaces of buried PLAxEGMCy specimens reduce significantly as their EGMC contents increase. Further DMA and morphological analysis of PLAxEGMCy specimens reveal that the EGMC molecules are compatible with PLA molecules at EGMC contents equal to or less than 2 wt.% because no phase-separated EGMC droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLAxEGMCy specimens, respectively. The possible reasons for these remarkable properties of the PLA/EGMC specimens are proposed in this study.

Mechanical properties, biocompatibility, and biodegradation of cross-linked cellulose acetate-reinforced polyester composites.

Composites of treated (cross-linked) cellulose acetate (t-CA) and acrylic acid-grafted poly(hydroxyalkanoate) (PHA-g-AA/t-CA) exhibited noticeably superior mechanical properties compared with PHA/CA composites due to greater compatibility between the two components. The dispersion covering of t-CA in the PHA-g-AA matrix was highly homogeneous as a result of condensation reactions. Human lung fibroblasts (FBs) were seeded on these two series of composites to characterize the biocompatibility properties. In a time-dependent course, the FB proliferation results demonstrated higher performance from the PHA/CA series of composites than from the PHA-g-AA/t-CA composites. The water resistance of PHA-g-AA/t-CA was higher than that of PHA/CA, although the weight loss of both composites buried in Acetobacter pasteurianus (A. pasteurianus) indicated that they were both biodegradable, especially at higher levels of cellulose acetate substitution. The PHA/CA and PHA-g-AA/t-CA composites were more biodegradable than pure PHA, implying a strong connection between cellulose acetate content and biodegradability.

Palm fibre-reinforced hybrid composites of poly(butylene succinate): characterisation and assessment of mechanical and thermal properties

The biodegradability and mechanical and thermal properties of composite materials made from glycidyl methacrylate-grafted poly(butylene succinate) (PBS-g-GMA) and palm fibre (PF) were evaluated. Composites of PBS-g-GMA and PF (PBS-g-GMA/PF) exhibited noticeably superior mechanical properties compared with those of PBS/PF, due to greater compatibility of PBS-g-GMA with PF. The dispersion of PF in the PBS-g-GMA matrix was highly homogeneous as a result of condensation reactions. In addition, the PBS-g-GMA/PF composites were more easily processed due to their lower melt torque. The water resistance of PBS-g-GMA/PF was higher than that of PBS/PF, although the weight loss of composites buried in soil compost indicated that both were biodegradable, especially at high levels of PF substitution. The PBS/PF and PBS-g-GMA/PF composites were more biodegradable than pure PBS, which implies a strong connection between PF content and biodegradability.

Thermal properties and characterization of surface-treated RSF-reinforced polylactide composites

The thermal, mechanical, and biodegradation properties of composite materials made from polylactide (PLA) and rice straw fibre (RSF) were evaluated. To improve the properties of PLA/RSF composites, glycidyl methacrylate (GMA)-grafted polylactide (PLA-g-GMA) and treated (crosslinked) rice straw fibre (TRSF) were used to prepare the composites. The result showed that PLA-g-GMA/TRSF had noticeably superior mechanical properties compared with PLA/RSF because of greater compatibility between the polymer and TRSF. The dispersion of TRSF in the PLA-g-GMA matrix was more homogeneous, because branched and crosslinked macromolecules formed via condensation of the glycidyl methacrylate groups of PLA-g-GMA and the hydroxyl groups in TRSF. In addition, the PLA-g-GMA/TRSF composites were more easily processed because of their lower melt viscosities. The water resistance of PLA-g-GMA/TRSF was higher than that of PLA/RSF, although the weight loss of composites buried in soil compost indicated that both were biodegradable, especially at high levels of RSF substitution. The PLA/RSF and PLA-g-GMA/TRSF composites were more biodegradable than was pure PLA.

Biocompatibility and characterization of renewable agricultural residues and polyester composites

Composites of sesame husk and glycidyl methacrylate-grafted polytrimethylene terephthalate (PTT-g-GMA/SH) exhibit noticeably superior mechanical properties compared to PTT/SH composites due to greater compatibility between the two components. The dispersion of SH in the PTT-g-GMA matrix is highly homogeneous as a result of condensation reaction formations. Human lung fibroblasts (FBs) were seeded on these two series of composites to characterize the biocompatibility properties. In a time-dependent course, the FB proliferation results demonstrated higher performance from the PTT/SH series of composites than from the PTT-g-GMA/SH composites. In addition, collagen production by FBs present in the PTT/SH series was 20% higher than in regular culture-plates after 7 days of incubation. The water resistance of PTT-g-GMA/SH was higher than that of PTT/SH, although the weight loss of both composites buried in soil compost indicated that they were both biodegradable, especially at higher levels of SH substitution. The PTT/SH and PTT-g-GMA/SH composites were more biodegradable than pure PTT, implying a strong connection between SH content and biodegradability.