On the study of structure property of polypropylene-glycol based polyurethane ionomer

Water-based polyurethane ionemers which have been successfully synthesized at our lab are demonstrated to be polypropylene glycol-based polyurethane ionomers by FT-IR spectra. For polyurethane ionomers prepared at a fixed ratio of NCO to OH as a function of ionic content, their viscosities are seen to be higher for polypropylene glycol with molecular weight of 1500 (triols) than for polypropylene glycol with molecular weight of 1000 (diols) or 2000 diols based polyurethane ionomers, as a result of strong intra ionic chain interaction. On the other hand, the viscosities due to strong inter chain interaction appear to be higher for polypropylene glycol with molecular weight of 1000 than for polypropylene glycol with molecular weight of 1500 or 2000-based polyurethane ionomers made at a fixed ionic content and under the variation of the ratio of NCO/OH. Like surfactant, poly-propylene glycolbased polyurethane ionomers present in water can substantially reduce the surface tension-of water. Thus, it may be considered as an ionomer-like surfactant.     

WPU预聚体中羧基含量及其位置对树脂的粒径及其耐水性之影响的研究

本文先将马来酸酐与多元醇作用，然后再与其它单体反应，合成了含有羧基的聚氨酯预聚体，并用丁酮稀释后，在普通搅拌条件下使预聚体分散于三乙醇胺的水溶液中，合成出以水为分散介质的聚氨酯分散体系（WPU）。并通过改变羧基在预聚体中的含量和位置，发现随着羧基含量的增加，WPU的粒径减小，而耐水性下降。同时发现，在一定的羧基含量下，同侧羧基相比，端羧基更有利于预聚体的乳化，制得的WPU不仅颗粒较小，而且树脂耐水性明显优于侧基羧预聚体制备的WPU，从而提出羧基的运动自由度是影响羧基乳化活性和树脂耐水性的重要因素。     

Synthesis and properties of polyurethane elastomers crosslinked with amine-terminated AB2-type hyperbranched polyamides

Amine-terminated AB₂-type hyperbranched polyamides of different molecular weights were prepared from 3,5-bis-(4-aminophenoxy)benzoic acid (AB₂ monomer) by fractional precipitation technique and characterized by FTIR, ¹H-NMR spectroscopies, DSC and GPC techniques. The degree of branching (DB) of hyperbranched polymers (HBP) was determined using ¹³C-NMR spectroscopy and it was found that the value increased with decrease in molecular weight of polymer considered. As the molecular weight distribution was narrow, the approximate number of end functional groups of each HBP was conveniently calculated. Three polymers were selected and used as crosslinkers in the preparation of polyurethanes. The incorporation of hyperbranched polyamide into the polyurethane chains was confirmed using FTIR and ¹H-NMR spectroscopic techniques. Among the range studied (1-6%), it was found that high tensile strength is attained with 1% of HBP. It was also found that the tensile strength decreases with increase in number of end functional groups and decrease in DB of HBP. However, glass transition temperatures and thermal stability of polyurethanes crosslinked with up to 6% of HBP, above which gelation occurred, were not affected and similar to the blank polymer prepared without AB₂ polymer.     

Mechanical properties of solvolysis lignin-derived polyurethanes

In order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG-MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.     

Thermal analysis of thermoplastic elastomers based on recycled polyethylenes and ground tyre rubber

Thermal stability and phase structure of thermoplastic elastomers (TPEs) based on post-consumer materials such as recycled lowor high-density polyethylene and ground tyre rubber (GTR) were investigated by using TG, DSC and DMTA analysis. Preliminary reclamation of GTR leads to enhancement of compatibility between polyethylene matrix and dispersed GTR particles.     

Structure and water sorption of polyurethane nanocomposites based on organic and inorganic components

Organic-inorganic polymer composites, consisting of a polyurethane organic phase and a mineral inorganic phase were prepared by the joint polymerization of the urethane oligomer with the water solution sodium silicate. The structure and the morphology of the composites, at a fixed weight fraction of the inorganic component of 20%, and of the corresponding pure polyurethane matrices were investigated by wide-angle and small-angle X-ray scattering (WAXS and SAXS, respectively). The results show similar size (5-7 nm) of the scale of heterogeneity of the composites due to the microphase separation of the rigid and the flexible blocks of the amorphous polyurethane matrix and due to the inorganic crystalline inclusions, i.e. the materials prepared are nanocomposites. The WAXS measurements indicate that the individual properties of the block inorganic component are lost in the nanocomposites, probably due to physical and chemical interactions between the two components. Water sorption from the liquid phase was studied gravimetrically in a composite and in the corresponding polyurethane. The results show high sorption capacity of the composite, due to the hydrophilicity of the inorganic phase and the elasticity of the polyurethane matrix, and allow to estimate the layer thickness of water adsorbed on the inorganic nanoparticle surface to about 20 nm, in reasonable agreement with a model adopted from the literature. WAXS and SAXS measurements on the swelled composite and the swelled-and-dried composite indicate changes in the structure of the inorganic component induced by water, which are, however, to a large extent reversible. These materials may find applications as gel electrolytes and as hydrogels in drug delivery systems.     

Degradation and thermal properties of in situ compatibilized PS/POE blends

This paper reported the degradation behaviors and thermal properties of polystyrene (PS)/polyolefin elastomer (POE) blends with AlCl₃ as the catalyst of Friedel-Crafts alkylation reaction. Gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) were adopted to reveal the effects of in situ grafting reaction and degradation of blending compounds on the thermal properties of PS/POE blends. It was found that the changes in both catalyst content and blend composition influenced the competition between in situ grafting reaction and degradation, resulting in the complexity of the thermal properties of PS/POE/AlCl₃ blends.     

Photoageing of an electron beam cured polyurethane acrylate resin

Photoageing reactions and kinetics on long wavelength irradiation of an electron beam (EB) cured resin are presented. The material studied is an aliphatic polyurethane acrylate resin. The chemical photoreactivity of the polymer was followed by infrared spectroscopy and UV-visible spectrophotometry. Two periods of photo-oxidation were found. In the first stage the reaction of acrylate functions remaining after EB polymerization leads to additional crosslinking and to oxidized products. The tip of an atomic force microscope was used as an indenter to follow the variation of stiffness at the surface resulting from crosslinking. In the second stage, oxidation rate decreases and photodegradation products are formed at a constant rate. A heterogeneous distribution of residual acrylates was evidenced across the coating thickness (thick films of 100 μm). An oxidation profile was also observed in the depth of the film after photoageing.     

Effect of oligomeric surface modifying agent on electro-optical properties of polymer dispersed liquid crystal

In order to lower the driving voltage of polymer dispersed liquid crystal (PDLC), an oligomeric surface modifying agent (SMA) which is a fluoroalkyl terminated polyurethane (PU) oligomer has been synthesized and added to polyurethane acrylate (PUA) resin. With the addition of SMA, contact angle of the resin surface with an LC drop increased and domain size decreased significantly due to the enrichment of SMA molecules at the surfaces. Operating voltage decreased up to 5 phr SMA and increased beyond this content. Regarding the effect of SMA molecular weight, lower molecular weight drove the shutter at lower operating voltage, indicative of more enrichment of the SMA molecules at the surfaces.     

Accelerated ageing of polyurethanes for marine applications

Polyurethanes are frequently used in underwater applications. They are required to resist the marine environment over long periods of immersion but the multiplicity of resin formulations makes material selection difficult. Accelerated tests are essential to guarantee long term integrity. This paper presents results from an experimental study in which polyurethane samples of two hardnesses, 40 and 90 Shore A, have been subjected to immersion in artificial sea water for periods up to two years at temperatures from 50 to 100 °C. In parallel samples have been immersed at sea in the Brest Estuary for up to five years. Mechanical properties have been measured on tensile specimens after ageing. The accelerated test results and FTIR analysis indicate that hydrolysis can occur. However, an estimation based on a linear Arrhenius extrapolation indicates that the timescale for 50% property loss at sea temperatures is in excess of 100 years. The results from sea ageing confirm that these materials retain 100% of their initial tensile properties after five years of immersion.