Showing papers by "Kung-Hwa Wei published in 2001"
TL;DR: In this paper, the hydrogen bonding in the hard segments of the synthesized montmorillonite/polyurethane nanocomposites of various hard segment ratios was found to decrease with the increasing amount of montminillonite regardless of the hard segment ratio.
330 citations
TL;DR: In this paper, a polyurethane prepolymer was synthesized by using reactive swelling-agent-modified silicates as pseudo chain extenders for polyurethene prepolymers, which achieved a 34% increase in Young's modulus, a 1.7-fold increase in tensile strength, and a 3.3-fold increased in elongation to break.
Abstract: Tethered layered silicates/polyurethane nanocomposites displaying high tensile strength and high elongation to break were synthesized by using reactive swelling-agent-modified silicates as pseudo chain extenders for a polyurethane prepolymer. The dispersion of layered silicates in polyurethane was found to be transformed from an intercalated to an exfoliated structure when the number of hydroxyl groups of the swelling agent increased as evidenced from the transmission electron microscopy and wide- angle X-ray diffraction analyses. The improved morphology of the nanocomposites resulted in an ultrahigh efficiency in enhancing the mechanical properties of polyurethane, despite variations in the molecular weight and in the extent of hydrogen bonding in the hard segment phase. In particular, a 34% increase in Young's modulus, a 1.7-fold increase in the tensile strength, and a 1.3-fold increase in the elongation to break occurred in the nanocomposite of polyurethane containing only 1 wt % trihydroxyl-group swelling- agent-modified silicates as compared to those of pristine polyurethane.
263 citations
TL;DR: Montmorillonite/polyimide (3,3,4,4‘-benzophenone tetracarboxylic dianhydride-4, 4‘)-oxydianiline, BTDA-ODA) nanocomposites displaying different morphological, thermal, and mechanical characteristics as mentioned in this paper.
Abstract: Montmorillonite/polyimide (3,3‘,4,4‘-benzophenone tetracarboxylic dianhydride-4,4‘-oxydianiline, BTDA-ODA) nanocomposites displaying different morphological, thermal, and mechanical characteristics...
171 citations
TL;DR: In this paper, the thermal properties and the moisture absorption of three types of polyimide/montmorillonite nanocomposite were investigated: 3,3,4,4'-biphenyltetracarboxylic dianhydride-4, 4'-oxydianiline (BPDA-ODA); pyromellitic dian hydride-ODDA (PMDA-ODA); and 3, 3,4',4', 4,'-benzophenone tetracaroxylic diyanide-dian
Abstract: The thermal properties and the moisture absorption of three types of polyimide/montmorillonite nanocomposite were investigated: 3,3',4,4'-biphenyltetracarboxylic dianhydride-4,4'-oxydianiline (BPDA-ODA); pyromellitic dianhydride-ODA (PMDA-ODA); and 3,3',4,'-benzophenone tetracarboxylic dianhydride-ODA (BTDA-ODA) The inhibition effect on in-plane coefficients of thermal expansion (CTE) and moisture absorption of these polyimide nanocomposites by layered silicates from montmorillonite was found to decrease with the crystallinity in the pristine polyimides The largest reduction, 30% in in-plane CTE occurred in the case of amorphous BTDA-ODA containing 5 wt % montmorillonite as compared with that of pure BTDA-ODA, while the reduction in in-plane CTE was 20% for the case of semicrystalline BPDA-ODA The maximum reduction in moisture absorption, 43%, also took place for the case of 3/97 ODA-Mont/BTDA-ODA as compared with that of pure BTDA-ODA, whereas the semicrystalline 1/99 PPD-Mont/BPDA-ODA showed a 30% reduction as compared with that of pure BPDA-ODA
37 citations