Tsu-Hwang Chuang

Thermal Properties and Flammability of Ethylene-Vinyl Acetate Copolymer/Montmorillonite/Polyethylene Nanocomposites with Flame Retardants

Ethylene-vinyl acetate copolymer (EVA)/montmorillonite (MMT) composite was blended with a linear low density polyethylene (LLDPE). X-ray diffraction and transmission electron microscopy (TEM) image of the EVA/MMT composite are in support of an intercalated with partially delaminated nanocomposite. The tensile strength of the nanocomposite is about 20% higher than that without layered silicates, MMT. Furthermore, the incorporation of MMT into polymer blend delays the main thermo-oxidative degradation. Cone calorimeter test points out that the addition of layered silicates into the pristine EVA/LLDPE blend or the blend with a low smoke non-halogen (LSNH) fire retardants, aluminum trihydroxide, and antimony trioxide, can reduce the maximum heat release rate by 30–40%. The smoke suppressing effect of layered silicates is only observed in the nanocomposite containing flame retardants. According to the limiting oxygen index (LOI) data and cone calorimeter test, the addition of the nanodispersed layered silicate and LSNH flame retardants to the EVA/LLDPE exhibits a synergistic effect on the flame retardancy and smoke suppression.

Kinetic analysis of the thermal oxidation of metallocene cyclic olefin copolymer (mCOC)/TiO2 composites by FTIR microscopy and thermogravimetry (TG)

A new amorphous engineering thermoplastic, metallocene cyclic olefin copolymer (mCOC) is considered as a promising material for optical, electrical and mechanical applications. To further expand its application in electro-optic devices, the improvement of mCOCs thermophysical and dielectric properties has been achieved by the addition of suitable inorganic fillers. In the present study, TiO2 powder was chosen to be mixed with mCOC to form a polymer composite. The change of thermal stability of the mCOC composite due to the presence of TiO2 is examined by a thermogravimetry (TG) and an in situ FTIR microscopy equipped with a hot stage. As a result, reaction mechanisms of polymer degradation with and without the filler are obtained. In addition, kinetics of thermal oxidation of filler-free mCOC and mCOC/TiO2 composite are quantitatively achieved by means of non-isothermal weight-loss data analysis.

Kinetic model of hyperbranched polymers formed by the polymerization of AB2 monomer with a substitution effect

Hyperbranched polymers obtained by the polymerization of AB2-type monomer with a substitution effect on the B2 groups were studied by means of the kinetic model. In this polymerization with the substitution effect, if one of the B2 group reacts first, the reactivity of the remaining unreacted B group will be changed. The profiles of the degree of polymerization, polydispersity, degree of branching, and structural units of the hyperbranched polymers with the conversions were all calculated by the generating function method. It is shown that the weight-average degree of polymerization and the degree of branching of the hyperbranched polymers having substitution effect differ from that with equal reactivity of the B2 groups. If the substitution effect causes an increase in the rate constant after one of the B2 groups has reacted, a broader molecular weight distribution and a higher degree of branching are observed.

EFFECTS OF GLASS MICROFILLERS ON THE WATER-TRANSPORT BEHAVIOR OF POLYURETHANE COMPOSITES

Glass microspheres with unique composition and diameter, and modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the liquid transport properties of the PU composites. Transport properties such as diffusion, permeability, and sorption coefficient were measured on various filler-filled PU composites at three different temperatures. These temperature-dependent parameters were used to provide a quantitative way to examine the effects of filler loading and the surface properties on the improvement of the water transport properties of PU composites. Results show that due to trapping at interfacial boundaries between filler and polymer, a high water affinity and large space for water activity is expected inside all the filler-filled composites. As a result, lower water diffusion (or high water resistivity) was found among all the filler-filled composites compared to that of filler-free composites. Besides, the more filler present in the composite, the longer the paths of the water molecules within the composites as the water penetration proceeds. Thus, lower diffusion coefficient values were observed for composites with large amounts of filler addition.

DYNAMIC MECHANICAL STUDIES OF POLYURETHANE COMPOSITES FILLED WITH GLASS MICROFILLERS

Ceramic microspheres with unique composition and diameter, modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the visco-elastic and mechanical properties of PU composites. Results of dynamic mechanical spectra indicate that the introduction of micro-beads H50, D32 and K37 into the PU network leads to the shift of glass transition temperature. Besides, the intensity of loss tanδ of PU composites decreased as a function of the fillers concentration, due to reduced concentration of polymer backbones. Both the shift of Tg as well as the changes of loss tanδ show that the introduction of microspheres not only creates physical bonding with PU but also causes steric effects due to the adsorption of N−H and C=O functional groups of PU on the filler surface. However, the introduction of various microfillers shows the composites to have different Youngs modulus. This evidence shows that the rigidity and elasticity of polymer composite can be finely tuned by the introduction of various surface-treated microfillers as well as the amount of filler added.