Preparation of UV-curable functionalized graphene/polyurethane acrylate nanocomposite with enhanced thermal and mechanical behaviors

Functionalized graphene nanosheets (f-GNSs) were synthesized by a simple covalent functionalization of graphene with 3-methacryloxypropyl trimethoxysilane (MPTES). The results from FTIR, XPS and XRD showed that MPTES was successfully attached onto the surface of graphene. Functionalized graphene/polyurethane acrylate (f-GNS/PUA) nanocomposites were prepared by UV radiation of PUA with f-GNS. The onset thermal degradation temperature of f-GNS/PUA nanocomposite was increased by 16 °C, at an f-GNS content of 1 wt%. Meanwhile, the storage modulus and glass transition temperature of the nanocomposites were enhanced by incorporating f-GNS into the PUA. This is believed to be attributed to that the covalent functionalization of graphene can improve both the dispersion of f-GNSs in the polymer matrix and the interfacial interactions between f-GNSs and PUA.     

单组分聚氨酯密封胶的研制

论述了单组分聚氨酯密封的合成方法，讨论了聚醚分子量，填料含量，催化剂用量等对聚氨酯弹性体性能的影响，选择合适的多元醇和多异氰酸酯，以适当的比例合成的弹性体性能和国外产品相媲美，能满足工业化生产的需要。     

聚氨酯弹性体水解稳定性

以聚氨酯水解机理为基础，讨论了影响聚氨酯弹性体（ＰＵＲ）水解稳定性的因素，并综述了改善ＰＵＲ水解稳定性的方法。     

Flexible cross‐linking by both pentaerythritol and polyethyleneglycol spacer and its impact on the mechanical properties and the shape memory effects of polyurethane

A series of polyurethane (PU) polymers cross‐linked laterally by pentaerythritol and polyethyleneglycol (PEG) spacers were compared with linear PU. The PU was composed of 4,4′‐methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol), 1,4‐butanediol (BD), pentaerythritol, and PEG‐200 as a spacer. PEG‐200 connected the pentaerythritol hydroxyl groups of two PU chains with MDI as a connecting agent. The phase separation between hard and soft segments was disrupted by the PEG crosslinking, and T_m did not change with an increase in cross‐linking content. Instead, the cross‐link density increased with an increase of pentaerythritol content. A significant increase in maximum stress compared with linear PU was attained, together with an increase in strain. The combination of both pentaerythritol and PEG‐200 in the PU resulted in the improvement of both stress and strain, unlike in the conventional cross‐linking method. The shape recovery increased to 90% and did not decrease after three test cycles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Surface segregation and miscibility in blends of poly(vinylidene fluoride-co-hexafluoro-acetone) with poly(butyl acrylate)

The surface segregation in poly(butyl acrylate) (PBA)/poly(vinylidene fluoride-co-hexafluoro-acetone) [P(VDF-HFA)] blends was confirmed by X-ray photoelectron spectroscopy (XPS), and is thought to be caused because the surface tension of P(VDF-HFA) is smaller than that of PBA. The PBA/P(VDF-HFA) blends were miscible at room temperature and exhibited a lower critical solution temperature (LCST) phase behavior. Thus, it was considered that the surface segregation of the P(VDF-HFA) component in PBA/P(VDF-HFA) blends was caused by the difference in surface tension between the components. Depth profiles [In(<Ø₁ (d) -Ø^b ₁) vs. depth (d), where Ø₁ (d) and Ø^b ₁ are the volume fractions at depth d from the surface and into the bulk, respectively] for PBA/P(VDF-HFA) blends were constructed by the mean-field treatment. The ln(Ø₁(d) - Ø^b ₁) vs. d plots for the PBA/P(VDF-HFA) blends could be approximated by a straight line.     

DEGRADATION RATE OF WATER-SOLUBLE POLYMERS BY OZONE

Water-soluble polymers were degraded by ozone, and the degradation rate defined by the change of weight average polymerization degree per unit time was obtained. The degradation rate of poly(oxyethylene) (PEG) was proportional to the 1.5 to 2.0 power of the polymerization degree, and was 20 to 60 times that of poly(acrylamide) (PAAm). The experimental results of PEG and PAAm were correlated as a function of polymerization degree, temperature, dissolved ozone concentration and OH^? ion concentration. The degradation rate of poly(sodium acrylate)(PANa) was proportional to the 2.0 power of the polymerization degree when no other electrolyte was added. However, the degradation rate of PANa decreased with the increase in NaCl concentration, and approached that of PAAm in the range of high NaCl concentrations.     

A polyurethane‐based nanocomposite biocompatible bone adhesive

A novel polyurethane‐based foam‐like adhesive reinforced with nanosized hydroxyapatite (HA) particles was developed and investigated for bone‐to‐bone bonding applications in terms of mechanical adhesion and biocompatibility. The adhesive has a hierarchical structure with HA particles at the nanoscale level and pores at the micro‐scale level. This adhesive was tested mechanically in the three principal loading modes anticipated: shear, tension, and compression. Standard testing procedures were used when available. Tensile strength of primed adhesive showed a four‐fold increase in adhesion on unmodified bone and a nearly two‐fold increase in adhesion to primed bone as compared with the conventional bone cement. Biocompatibility was initially assessed in vitro using cell culture tests, which showed positive interaction with the adhesive. Then, a second biocompatibility test was performed using Xenopus laevis limbs to assess an in vivo response. The results indicated that the adhesive material produces a normal response consistent with control specimens. However, long‐term observations and tests with additional species are needed to demonstrate full biocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

Self adhesion of short Kevlar fibre-thermoplastic polyurethane composite

The self adhesion behaviour of thermoplastic polyurethane (TPU) in itself and its composite with short Kevlar fibre with respect to contact time, temperature, pressure, and fibre loading has been studied. The adhesion strength showed two linear increments of different slopes with respect to the square root of time: with temperature and pressure of contact, the adhesion strength was improved. The maximum strength was obtained with 20 phr of short fibre in only one of the mating substrates in the peel test sample. The duration for wetting and diffusion was shifted to longer time intervals with fibres loaded in both the substrates.     

Letter

¹⁵N variable contact time (VCT) cross polarization magic angle spinning (CPMAS) NMR experiments were employed to investigate the reaction products formed in wood composites bonded with ¹⁵N-enriched polymeric diphenylmethane diisocyanate (PMDI)-based adhesives. Two wood species were studied. Aspen (Populus tremuloides) and Southern Pine (Pinus sylvestris). The influence of temperature and wood moisture content on the distribution of PMDI-derived species are presented and discussed.     

双环戊二烯-马来酸酐共聚物的合成、表征及其与聚氨酯反应性共混研究

合成了双环戊二烯-马来酸酐交替共聚物(DCPD-co-MA),产率约25%。采用红外、核磁共振氢谱和碳谱对共聚物进行了表征,差热分析和热重分析表明该共聚物具有较好的热性能,其T_g为210℃,起始热失重温度为310℃。采用反应性共混方法合成了DCPD-co-MA与聚氨酯(PU)的共混物(PU/DCPD-co MA),反应温度为80℃。该共混物具有较好的综合性能,其起始热失重温度较纯PU提高了约41℃,共混后,其耐热性能有较大改善。