Chi-Hui Tsou

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.

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.

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 containing thermally treated attapulgite nanorods

In this study, polyurethane (PU) was synthesized using 4,4,-diphenylmethane diisocyanate as a hard segment, polytetramethylene glycol and polycaprolactone diol as soft segments, and 1,4-butanediol (1,4-BD) as a chain extender. Thermally treated attapulgite (TAT) was added to the PU matrix to prepare TAT/PU nanocomposites. The TEM, FT-IR, XRD and EDS were used to characterize the structure and morphology of the TAT/PU nanocomposites. The TEM results show that TAT maintains its rod-like structure in the PU matrix. The results showed that the addition of a small content of TAT resulted in no obvious changes in the Fourier transform infrared (FT-IR) spectra. XRD results showed that the main crystalline peak of TAT became more pronounced with increasing content of TAT, and EDS showed that the content of Si increased with increasing content of TAT in the TAT/PU nanocomposites. The thermal and mechanical properties were optimal at 2 wt% TAT. When TAT was added at 5 wt%, agglomeration occurred, resulting in a decrease in the thermal and mechanical properties of the TAT/PU nanocomposites. Contact angle and AFM results showed that the hydrophobicity and surface roughness increased with increasing content of TAT. SEM showed that the hydrolytic degradation was affected by the test temperature, test time, and the content of TAT. Moisture absorption tests showed that the moisture absorption of TAT/PU nanocomposites increased with increasing content of TAT and higher environmental humidity.

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.

Preparation and physicochemical properties of digested collagen fragments with varying molecular weights

The porcine dermal collagen molecules were successfully digested by clostridium histolyticun collagenases (CHC) and then ultra-filtrated using varying grades of ultra-filtration membranes. Gel permeation analyses revealed that collagen fragments with varying molecular weights were successfully segregated using ultra-filtration membranes with varying grades of pore sizes. Fourier transform infra-red analyses suggest that digested collagen fragments and digested collagen fragments prepared after ultra-filtration still preserve certain percentages of triple helix structures of collagen molecules, although the percentages of preserved triple helix structures present in digested and ultra-filtrated collagen fragments reduce significantly as their Mw values reduce. Thermal and denaturation temperature analysis suggest that denaturation temperature and thermal degradation temperature values of digested collagen fragments and ultra-filtrated collagen fragments decrease significantly as their Mw values reduce. The absorbed/desorbed amounts of digested and ultra-filtrated collagen fragments in PA6/PP flocking specimens are significantly higher than those of the original collagens, and increase significantly as their Mw values reduce. Possible reasons accounting for the above degradation, ultra-filtration physicochemical, absorbing and desorbing properties of original, digested and ultra-filtrated digested collagen molecules are reported.