Wen Shyang Chow

Poly(lactic acid)/halloysite nanoclay composites (PLA/HNC) containing maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MAH) were exposed to hygrothermal aging at three different temperatures, i.e., 30, 40 and 50°C. The analysis was focused on the water diffusion kinetics and physical changes induced by the hygrothermal degradation. The water absorption kinetics of the PLA/HNC composites at immersion temperature of 30 and 40°C conforms to Fick's law. The equilibrium water absorption (M_m ) and diffusion coefficient (D) values are dependent on the SEBS-g-MAH content and immersion temperatures. Hydrolytic chain scission provoked significant molecular weight reduction. Nevertheless, adding SEBS-g-MAH improved hygrothermal stability of the PLA/HNC nanocomposites.

In this work, the influence of precipitated nano calcium carbonate (PNCC) on the mechanical and thermal properties of epoxy/glass fiber (GF) laminates was studied. The mechanical properties of the epoxy/GF/PNCC composites were characterized by flexural and impact tests. The fracture toughness of the epoxy hybrid composites was evaluated by the principle of linear elastic fracture mechanics via single-edge notched bending tests. The thermal properties of the epoxy hybrid composites were studied using dynamic mechanical analyzer (DMA) and thermogravimetric analyzer (TGA). The flexural properties, impact strength, and fracture toughness of the epoxy/GF laminates were increased profoundly in the presence of PNCC. Additionally, from the DMA and TGA results, it was found that the storage modulus and thermal decomposition temperature of the epoxy/GF increased remarkably with the addition of PNCC.

Poly(ethylene terephthalate)/organo-montmorillonite (PET/OMMT) nanocomposites were melt-compounded using twin screw extruder followed by injection molding. N,N′-ethylenebis(stearamide) (EBS) was selected as a dispersing agent to improve the dispersibility and exfoliation of OMMT clay in PET matrix. Morphological properties of the PET/OMMT nanocomposites were examined by using X-ray diffraction analysis, transmission electron microscopy and atomic force microscopy. Thermal properties of the nanocomposites were characterized by using dynamic mechanical thermal analysis. It was found that the OMMT are well dispersed and exfoliated in the presence of EBS. Remarkable enhancement in impact strength and storage modulus of PET/OMMT was achieved by the addition of EBS.

Poly(lactic acid)/organo‐montmorillonite (PLA/OMMT) nanocomposites toughened with maleated styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) were prepared by melt‐compounding using co‐rotating twin‐screw extruder followed by injection molding. The dispersibility and intercalation/exfoliation of OMMT in PLA was characterized using X‐ray diffraction and transmission electron microscopy (TEM). The mechanical properties of the PLA nanocomposites was investigated by tensile and Izod impact tests. Thermogravimetric analyzer and differential scanning calorimeter were used to study the thermal behaviors of the nanocomposite. The homogenous dispersion of the OMMT silicate layers and SEBS‐g‐MAH encapsulated OMMT layered silicate can be observed from TEM. Impact strength and elongation at break of the PLA nanocomposites was enhanced significantly by the addition of SEBS‐g‐MAH. Thermal stability of the PLA/OMMT nanocomposites was improved in the presence of SEBS‐g‐MAH. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

In this study, poly(ethylene terephthalate)/organo‐montmorillonite (PET/OMMT) nanocomposites were melt‐compounded using twin screw extruder followed by injection molding. Maleic anhydride grafted styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) was used to improve the impact properties of the PET/OMMT nanocomposites. The notched and un‐notched impact strength of PET/OMMT nanocomposites increased at about 2.5 times and 5.5 times by the addition of 5 wt % of SEBS‐g‐MAH. Atomic force microscopy (AFM) scans were taken from the polished surface of both PET/OMMT and SEBS‐g‐MAH toughened PET/OMMT nanocomposites. The addition of SEBS‐g‐MAH altered the phase structure and clay dispersion in PET matrix. It was found that some of the OMMT silicate layers were encapsulated by SEBS‐g‐MAH. Further, the addition of SEBS‐g‐MAH decreased the degree of crystallinity of the PET/OMMT nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) denture base composites were prepared using heat-processing polymers powder–liquid method, according to dental laboratory practice. The HA was pre-treated by isopropyl triisostearoyl titanate coupling agent (TCA) in order to improve the interfacial bonding between HA and PMMA. The effects of different concentration of titanate coupling agent (i.e., 2–8%) on the mechanical and morphological properties of PMMA were investigated. It was found that PMMA/2% TCA-treated HA composites exhibited higher flexural modulus and strength compared to PMMA/untreated HA composites. This is attributed to the enhanced interfacial interaction between PMMA and HA by the titanate coupling agent. However, for the PMMA/HA treated with 6% and 8% of TCA, the flexural properties was slightly reduced, which may associated to the plasticizing effects caused by excessive concentration of coupling agent. In addition, the fracture toughness properties of PMMA/5HA composites were influenced by the different concentration of TCA. The thermal properties of the PMMA/HA composites were enhanced by the treatment of titanate coupling agent.

Poly(lactic acid) (PLA)/organomontmorillonite (OMMT) nanocomposites were prepared by a melt intercalation technique. The effects of OMMT and poly(ethylene glycol) (PEG) on the thermal properties and water absorption behavior of PLA were investigated. The melting temperature and degree of crystallinity were comparable for the PLA and its nanocomposites. The glass transition temperature and crystallization temperature of PLA were decreased by the addition of PEG. X‐ray diffraction results revealed the formation of PLA nanocomposites, as the OMMT was partly intercalated and partly exfoliated. The maximum moisture absorption of PLA was increased in the presence of PEG and the diffusivity of the PLA nanocomposites decreased with increasing concentrations of PEG. However, the activation energy of the nanocomposites increased as the loading of PEG increased. These results indicated that the incorporation of OMMT and PEG enhanced the water‐barrier properties of the PLA. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers