Materials Science Forum Vol. 815

Abstract: Poly(ethylene terephathalate)/1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (POSS) composites were prepared by in situ polymerization with 1.5-5.0 wt% loading of POSS. The dispersion of POSS in PET matrix was investigated by scanning electron microscope(SEM) the interaction between POSS and PET chains was studied by nuclear magnetic resonance(NMR) andX-ray photoelectron spectroscopy(XPS), and the thermal behavior of PET/POSS composites was investigated by DSC and TG as well as the melt rheological testing of PET/POSS. SEM observation suggests that POSS particles disperse evenly innanosize(80-100nm)in PET matrix, and this fine dispersion of POSS was further supported by XPS analysis, there is a covalent linkage presenting between POSS and PET chains. The crystallization temperature of the composites moved to high temperature as the POSS particles behave as the nucleating agent. The shear modulus(G’) increased apparently with the addition of POSS.

Abstract: L-lysine-based dendritic gelator(G₃-C₁₂-G₃) was successfully designed and synthesized using a divergent approach and it can self-assemble into nanofibers in MMA followed by gelation. After thermal polymerization of MMA gels, the self-assembly nanofibers modified PMMA nanocomposite can be obtained. SEM studies indicate the embedded supra molecular nanofibres joint each other and form a relative intact gel networkskeleton in PMMA matrix. Impact strength and DMTAmeasurementindicatethe existence of gel network skeleton make PMMA nanocomposite had higher impact strength and storage modulus than pure PMMA. UV-vis spectrophotometer studies indicate PMMA nano-composite retains high light transmittance.

Abstract: The effect of orotic acid (OA) and its mixtures with calcium stearate (CaSt₂) and zinc stearate (ZnSt₂) in various ratios on the thermal stability of PVC has been investigated by Congo red and discoloration tests. The results shows that OA acts as a long-term thermal stabilizer for PVC like CaSt₂, and the combination of OA and ZnSt₂ exhibited a synergistic stabilization effect at a certain ratio. This is due to the ability of OA to absorb HCl released during the degradation of PVC to diminish its catalytic effects, and react with ZnCl₂ to stop its catalytic effect for PVC. CaSt₂-ZnSt₂/OA stabilizers exhibit good synergistic effects with both acceptable initial color and long-term stability for PVC

Abstract: Three kinds of amide dendritic branches, Branch₁ (COOH), Branch₂ (COOH) and Branch₃ (COOH), are successfully synthesized. After mixing with diaminoctane, their self-assembly behavior in methyl methacrylate (MMA) is investigated. The structures of the amide dendritic branches are confirmed by ¹H-NMR and Mass spectra (MS). The gelation ability of the amide dendritic gelators is researched through tube inversion experiment, the results of which show that different structures led to quite different gelation ability, including gel-sol temperature and critical concentration to form a stable gel. SEM experiments show that three kinds of gelators formed different gel morphologies in MMA.

Abstract: Ultra high temperature treatment was used to promote the molecular chain diffusion of UHMWPE/HDPE blend. At the same time, melt blended sample and solution blended sample were also prepared for a comparison. The phase morphology of the samples observed by scanning electron microscope (SEM) showed that the difference between HDPE and UHMWPE became smaller after high temperature treatment. While the UHMWPE particle could not be observed in solution blending samples. The results of rheological test showed that the elastic modulus and complex viscosity of treated samples are higher than that of untreated samples but still below the viscosity of solution blending sample. The results deem, high temperature treatment indeed promoted the chain diffusion of UHMWPE/HDPE blend and a good fusion between HDPE and UHMWPE is obtained as a result

Abstract: A series of porous poly(styrene-divinylbenzene) monoliths (polyHIPE) was synthesized by high internal phase emulsions (HIPE). The effects of the ethanol contents on the microstructure of the polyHIPE were characterized by scanning electron microscopy and mercury intrusion porosimeter. The adsorption and release behaviors of the polyHIPE for a monomer mixture consisting of dicyclopentadiene (DCPD) /styrene (St) (DS, mass ratio of 9/1) were investigated. The polymerization of the mixture DS within pores of the polyHIPE was studied. The results showed that the microstructure of the polyHIPE was significantly influenced by the ethanol content. The increase of ethanol in the HIPE increased the internal pore diameter and decreased the pore volume of the polyHIPE, thus decreased the DS absorption and increased the release rate. The DS monomer can enter the pores(cavities, windows) and fill the original holes after the polymerization. Compared with conventional polymerization of DCPD/St, the poly(DCPD/St) (pDS) obtained from confined spaces possess higher molecular weight, broader molecular weight distribution, and higher T_g. As the pore diameter increased, the effect of space confinement reduced, and the performances of pDS were closed to that prepared by conventional polymerization.

Abstract: The preparation of high performance hydrogels has always been one of the research focuses in the area of soft matters and functional polymers. In this paper, a facile method was developed for the preparation of high performance hydrophobic association nanocomposite hydrogels (HANC gels) via in situ copolymerization of acrylamide (AM) and octadecyl methacrylate (OMA) in the aqueous suspension of hectorite clay Laponite HZ-200 (clay) with sodium dodecyl benzene sulfonate (SDBS). Tensile hysteresis curves showed that the hysteresis degrees between HANC gels and conventional hydrophobic association hydrogels (HA gels) were almost the same, but the tensile strength of the HANC gel reinforced by just 0.4 wt% clay at the strain of 1500% was already as 630% as the strength of the HA gel, which indicated that the mechanical properties of the HA gel were greatly enhanced by the introduction of a small amount of clay without increasing the internal friction in the hydrogel network. The effects of clay on the structure of HANC gels were further confirmed by swelling test, it was found that the addition of clay effectively maintained the structural integrity of HANC gels in watery environment and prevented the collapse of gel network. Moreover, HANC gels exhibited superior cationic dye adsorption capacity compared to HA gels due to the existence of abundant negative charges on the surfaces of clay nanosheets

Abstract: In order to check the feasibility of crosslinking engineering plastics through chemical coupling, reactive blending of polyamide 6 (PA6) was performed with various amounts of a multi-functional epoxide named as Joncryl ADR®4370s. The formation of cross-linked structure in ADR modified PA6 was clearly verified by utilizing dynamic rheological technique. The thermal properties of modified PA6 were compared with that of pristine nylon by combination of differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Mechanical tests were also carried out and the results showed that ADR had a positive effect on improving tensile properties of polyamide.

Abstract: Balanced mechanical properties are always the goal of high-performance general plastics for engineering purposes. In order to develop uniformly dispersed graphene oxide/poly(_L-lactic acid) nanocomposites with balanced mechanical properties, a poly(ethylene glycol) (PEG) grafted graphene oxide was introduced into poly(_L-lactic acid) (PLLA) matrix. The PEG grafted graphene oxide (GEG) was confirmed by the results of fourier transform infrared (FTIR) spectra and thermal gravimetric analysis (TGA). Then the mechanical properties of the nanohybrids were measured. The results showed that in contrast to the aggregation of GO, GEG could uniformly disperse in PLLA matrix. An intriguing phenomenon is that thanks to the strong interfacial interaction between GEG and PLLA, it exhibits a substantial enhancement of the elongation at break (EB) as well as a simultaneous improvement of the tensile strength (TS), while the addition of GO decreases the EB of PLLA matrix. This work provides a potential industrialized technique for high-performance PLLA nanocomposites

Abstract: An IPDI-based waterborne polyurethane emulsion(WPU) was synthesized by the reaction of polyester glycol(PBA), di-methylol propionic acid(DMPA) with isophorone diisocyanate (IPDI) instead of toluene di-isocyanatotoluene(TDI) because of its low toxicity, low saturated vapor pressure. The factors influencing the properties of IPDI -based WPU were discussed. It was observed that the appearance and properties of the IPDI -based WPU were nearly related with the ratio of NCO/OH(R) and the amount of DMPA.