No abstract

Mechanical and morphological properties of hot gas butt welds on polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) sheets for four different procedures, which are single and double V-welds with and without a welding shoe, were investigated. Besides, weldabilities of base materials were evaluated by rheological measurements. These revealed that weldabilities of PE and PP sheets were better than that of PVC. Welding energy (E w ), which is transferred onto weld surfaces, was calculated to evaluate weld quality. The results of tensile, impact, and bending tests indicated that the weld strengths of PVC sheets were lower than those of PE and PP sheets. When the welding shoe was used, weld strength increased significantly for each material because of the presence of sufficient welding pressure and the effective heating on surfaces. The best results were attained for the double V-welds with the welding shoe. Morphology of welded regions was evaluated by polarized light, stereo, and scanning electron microscopy. Polarized light microscopy studies indicated that the heat-affected zone (HAZ) consisted of welding rod core, molten zone, and deformed spherulitic zone, and the welding interface was indistinguishable from the base material when the welding pressure was enough. POLYM. ENG. SCI., 48:732-746, FIG. 3. Geometries of weld grooves (y-z plane). (a) Single V-weld groove. (b) Double V-weld groove. FIG. 4. A cross-sectional view of the welding jig. a The values of welding speed (S w ) were measured on one of the two seams. The true welding speed values of double V-welds (X-welds), which are shown in parentheses, are half because a double V-weld comprises two seams. b The values of welding energy (E w ) were calculated using the true welding speeds of corresponding double V-welds. FIG. 9. Stress-strain (r-e) curves for base and welded PE, PP, and PVC sheets with various welding procedures.

Mechanical properties of the isotactic-polypropylene/ glass bead (iPP/GB) and iPP/wollastonite (iPP/W) composites modified with thermoplastic elastomers, the poly(styrene-b-ethylene-co-butylene-b-styrene) copolymer (SEBS) and corresponding block copolymer grafted with maleic anhydride (SEBS-g-MA), were investigated. An increase in toughness of iPP with the elastomers was associated with a decrease in rigidity and strength. Mechanical performance of iPP increased more with acicular W than with spherical GB due to reinforcing effect of W. Comparing the (iPP/GB)/ SEBS and (iPP/W)/SEBS composites having the separate microstructure, strength and toughness values of the iPP/GB and iPP/W composites increased more with SEBS-g-MA at the expense of rigidity due to the coreshell microstructure with strong interfacial adhesion. Moreover, the iPP/W composite exhibited superior mechanical performance with 2.5 and 5 vol% of SEBSg-MA because of a positive synergy between the coreshell microstructure and reinforcing effect of acicular W. The extended models revealed that the elastomer and filler particles in the (iPP/GB)/SEBS and (iPP/W)/ SEBS composites acted individually due to the separate microstructure. However, the rigid GB and W particles encapsulated with the thick elastomer interlayer (R 0 /R 1 ¼ 0.91) in the (iPP/GB)/SEBS-g-MA and (iPP/W)/ SEBS-g-MA composites acted like neither big elastomer particles nor like individual rigid particles, inferring more complicated failure mechanisms in the core-shell composites. POLYM. COMPOS.

In this study, polyimide-silica (PI-silica) based hybrid coating compositions were prepared from tetraethoxysilane (TEOS), g-glycidyloxypropyl trimethoxy silane (GOTMS), and polyamic acid (PAA) via a combination of sol-gel and thermal imidization techniques. PAA was synthesized from 3,3(,4,4(-benzophenone tetracarboxylic dianhydride (BTDA) and 3,3'-Diaminodiphenyl sulfone (DDS) in N-Methyl-2-pyrrolidone (NMP). The silica content in the hybrid coatings was varied from 0 to 20 wt%. The structural characterization of the hybrid coatings was performed using FTIR and 29 Si-NMR spectroscopies. Results from both pendulum hardness and micro indentation test show that the hardness of hybrid coatings improves with the increase in silica content. The tensile tests also demonstrated that the mechanical properties at low silica content are rather striking. Their surface morphologies were characterized by scanning electron microscopy (SEM). SEM studies revealed that inorganic particles were distributed homogenously through the PI matrix. It was also found that, incorporation of the silica domains increased the thermal stability of the hybrid coatings.

Microstructural characteristics of isotactic-polypropylene/glass bead (iPP/GB) and iPP/wollastonite (iPP/W) composites modified with thermoplastic elastomers, poly(styrene-b-ethylene-co-butylene-b-styrene) copolymer (SEBS) and corresponding block copolymer grafted with maleic anhydride (SEBS-g-MA), were investigated. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analyses (DMA) showed that the iPP/SEBS and iPP/SEBS-g-MA blends were partially compatible two-phase systems. Well-dispersed spherical GB and acicular W particles without evidence of interfacial adhesion were observed in the iPP/GB and iPP/W binary composites respectively. Contrary to the blends, melt flow rates of the iPP/GB and PP/W composites decreased more with SEBS-g-MA than with SEBS because of enhanced interfacial adhesion with SEBSg-MA elastomer. The SEM analyses showed that the ternary composites containing SEBS exhibited separate dispersion of the rigid filler and elastomer particles (i.e., separate microstructure). However, SEBS-g-MA elastomer not only encapsulated the spherical GB and acicular W particles completely with strong interfacial adhesion (i.e., core-shell microstructure) but also dispersed separately throughout iPP matrix. In accordance with the SEM observations, the DSC and DMA revealed quantitatively that the rigid filler and SEBS particles in iPP matrix acted individually, whereas the rigid filler particles in the ternary composites containing SEBS-g-MA acted like elastomer particles because of the thick elastomer interlayer around the filler particles. The Fourier transform infrared analyses revealed an esterification reaction inducing the strong interfacial adhesion between the SEBS-g-MA phase and the filler particles. POLYM. COMPOS.FIG. 12. Storage modulus (E 0 ) and damping factor (tan d) variations of the ternary composites as a function of temperature.