Morphology of epoxy resin modified with silyl‐crosslinked urethane elastomer

Silyl‐crosslinked urethane elastomer modifying epoxy resin has drawn much interest. Here the triethoxysilyl‐terminated polycaprolactone elastomer (PCL‐TESi) modifying diglycidylether of bisphenol A epoxy resins (DGEBA) system was chosen, and then the effect of the type of curing agent on the phase structure of the studied epoxy resin system was investigated. The modified systems were obtained with different phase structures by varying the formulations of the curing agent. It was experimentally shown that with the addition of aminosilane (KBE‐9103), the crosslinked density was greatly increased. The cured system also showed from SEM and TEM analysis that addition of KBE‐9103 increased the compatibility between the PCL‐TESi and DGEBA, which made the ductility of the system decrease, but also indicated from TEM that addition of much KBE‐9103 made the reacted silicone particles coagulate each other. The state of phase separation from TEM in the cured system was theoretically explained. These would serve the deeper studies of the mechanism of silyl‐crosslinked urethane elastomer modifying epoxy resin in the future. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 611–619, 2005     

邻接交联型聚氨酯脲弹性体的结构、性能与温度的相关性研究

以丁腈羟（HTBN）、甲苯二异氰酸酯（TDI）、扩链剂为原料,加入化学交联剂过氧化二异丙苯（DCP）和助交联剂N,N-间苯撑双马来酰亚胺（HVA-2）制备邻接交联型聚氨酯脲（PUU）弹性体,研究其结构、性能与温度的关系。变温拉伸测试表明,当温度升高时,PUU的力学性能保持率得到显著增加;变温红外测试表明交联型PUU的氢键化作用比线型PUU明显增强。     

低模量聚酯型PU弹性体力学性能的研究

以聚楷酯二醇、甲苯二异氰酸酯（TDI）和扩链剂为原料,制备浇注型PU弹性体,研究了预聚法和一步法、聚酯与聚醚、80/20-TDI和2,4-TDI、聚酯二醇的种类及其相对分子质量、弹性体交联点相对分子质量和硬段质量分数对弹性体力学性能的影响。结果表明,采用预聚法,以聚酯和80/20-TDI为原料合成的PU弹性体的综合性能较好。3种聚酯型PU弹性体中,聚丁二醇己二酸酯二醇的PU弹性体的综合力学性能最好。交联点相对分子质量为4500时,PU弹性体的强度为最大值。     

Syntheses and properties of pentaerythritol-containing urethane prepolymers and crosslinked films

Two series of polyhydroxyl urethane-prepolymers (Pre-PU) were synthesized from pentaery-thritol (PETH), toluene diisocyanate (TDI), and polyglycols (PG). One is a single molecular type of PETH-(TDI-PG)_n-TDI-PETH Pre-PU (S-Pre-PU). The other is a mixture of (PETH-TDI)_n-PETH and S-Pre-PU. The Pre-PU mixed with an equivalent triisocyanate regenerator (Desmodur AP-Stable, a crosslinking agent) were baked to form the crosslinked PU films. The mechanical properties such as tensile strengths, elongation at break, and viscoelasticities of PG-modified crosslinked films were studied.     

Syntheses and properties of urethane prepolymers and their corresponding crosslinked films

Trimethylol propane (TMP), polyglycol (PG), and toluene diisocyanate (TDI) were reacted in various molar ratios to produce TMP–TDI–PG–urethane prepolymers and then mixed with equivalent isocyanate generator (Desmodur AP-Stable) in a mixture of m-cresol and naphtha to give polyurethane varnishes which finally became crosslinked films by the casting method. The mechanical properties and viscoelasticities of the PG-modified and PG-free polyurethane crosslinked films and the practicability of magnet wires coated with them were studied in this article. Three different PGs used in this experiment were polyethylene glycol, PEG(#400), polypropylene glycols, PPG(#1000) and PPG(#2000). In the case of adding PEG(#400) for modification, strength at break increased but elongation did not change. Meanwhile, glass transition temperature (T_g) shifted to lower temperature with increasing molar ratio. In the case of adding PPG(#1000) and PPG(#2000) for modification, the samples changed their mechanical properties from hard and brittle to soft and tough. With increasing molar ratios, strength at break initially increased and then decreased gradually, and elongation varied a lot and was consistently contrary to strength at break. T_g occurred at two regions: one at high temperature above 100°C for small molar ratios and the other at low temperature below 100°C for high molar ratios. Besides, for all PG-modified polyurethane crosslinked films, strength at break showed a local maximum at TMP/TDI/PG = 1/1/0.5, which indicated their homogeneous structures. The molar ratios of PG-modified urethane prepolymers, which are suitable for manufacturing practical magnet wires according to testing method JIS-C-3211, are as follows: TMP/TDI/PPG(#100) = 1/1/0.15–0.35 and TMP/TDI/PPG(#2000) = 1/1/0.10. PEG(#400)-modified magnet wires were not accepted on the aging test. The properties of crosslinked films of practical magnet wires are generally as follows: strength at break at 200–700 kg/cm², elongation less than 41%, and T_g at 100–200°C.     

Influence of urethane group on properties of crosslinked polyurethane elastomers

Three series of weakly crosslinked polyurethanes based on a hydroxyterminated polybutadiene, hydroxyterminated butadiene–acrylonitrile copolymer, and hydroxyterminated ethylene–adipate–maleate–fumarate copolymer were prepared while varying the hard segment content between 1.72 and 2.36 mol ? NH? COO? /1000 g polymer. Information on the microphase structure and the properties of the synthesized polyurethanes was obtained by differential scanning calorimetry, wide‐angle X‐ray scattering, and mechanical studies. Up to a urethane concentration of around 2 mol ? NH? COO? /1000 g polymer, there is a mixture of hard–hard and hard–soft segments. Above this concentration a large part of the hard–soft segments passes into hard–hard crystallites, liberating the soft segments. The best mechanical properties of the studied polyurethanes were found for a urethane concentration of around 2 mol ? NH? COO? /1000 g polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1858–1867, 2003     

Low temperature transitions in a crosslinked urethane

We have investigated the low temperature transitions in a urethane prepolymer crosslinked with various amines and triols by measuring their dynamic mechanical properties over a temperature range of 25°C to approximately ? 190°C. In the formulations studied, a low temperature transition was observed near ? 140°C and the transition was shown to be related to the electronic and steric influences of the curing agent structure at the crosslink site. A quantitative relationship was demonstrated between the low temperature transition peak intensity and the polymer's crosslink density. The above relationships were derived from torsion pendulum and solvent swell experimentation.     

Nonlinear response and thermomechanochemical degradation of a urethane elastomer

We have studied the failure of a urethane elastomer due to cyclic compressive loading, using loading frequencies and specimen sizes for which internal heat generation is an important factor. The eventual failures were generally manifest by internal cracks growing transverse to the loading direction. A variety of experimental analyses indicate that this failure is primarily thermal, in that the temperature rise due to viscous dissipation eventually leads to a melting of the hard segment domains which act to reinforce the material. No strong indication of thermal or thermomechanical bond scission was obtained, although a progressive reduction in the rubbery modulus was noted.     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

无卤阻燃硅烷交联聚乙烯/橡胶的制备及性能

研究了氢氧化镁(MH)和微胶囊化红磷(MRP)不同添加量及不同配比对硅烷交联聚乙烯(SXPE)体系的氧指数、热释放速率、发烟量等燃烧性能的影响。结果表明，MRP对MH阻燃SXPE有协效作用，添加适量的MRP，SXPE／MH／MRP体系(PRMH2)的氧指数最高达37．5％。三元乙丙橡胶改善SXPE／MH体系力学性能的同时，阻燃性能也大幅度提高．阻燃级别由UL-94V-1级提高到VL-94V-0级。     

丁羟聚氨酯弹性体交联网络均匀性与其力学性能之间的关系

采用L-赖氨酸三异氰酸酯与端羟基聚丁二烯发生逐步聚合反应制备了丁羟型聚氨酯弹性体,通过动态热机械分析法研究了产物交联网络的均匀性,探讨了其与力学性能之间的关系。结果表明,端羟基聚丁二烯的分子量分布越窄,其所合成聚氨酯弹性体的交联网络越均匀,拉伸强度也越大,而扯断伸长率则减小。     

邻接交联丁腈羟/聚醚基聚氨酯脲弹性体的制备与性能(英文)

以丁腈羟和聚醚二醇、甲苯二异氰酸酯及扩链剂为原料,加入自由基引发剂双二五和化学交联剂N,N'-马来酰亚胺间苯撑(HAV-2),制备了邻接交联型聚氨酯脲弹性体(PUU).研究结果表明,随着HAV-2用量的增加,交联PUU弹性体的高温力学性能保持率逐渐提高,弹性体由热塑性转变为热固性,不再有软化点出现,表现出较好的热性能.     

Crystallization,structure, and enhanced mechanical property of ethylene-octene elastomer crosslinked with dicumyl peroxide

Crosslinking of polyolefin elastomer (POE, ENGAGE™ 8480) with Dicumyl Peroxide (DCP) can have effects on its crystallization dynamics, crystal structure, and properties. The POE crosslinked uniformly has significantly lower crystalline ability than the one with only amorphous phase crosslinked, which, in turn, has weaker crystalline ability than neat POE. The crystallinity and melting point depend on how the POE is crosslinked. The neat POE and POE crosslinked in amorphous phase only, are investigated with DSC and in-situ tensile/synchrotron radiation (WAXD/SAXS). In situ tensile/synchrotron X-ray during a uniaxial stretching process indicates that severe crystal fragmentation is observed at a strain around 45%, and with further increase in strain. The stress in the crosslinked POE is significantly larger than neat POE. For both samples, crystal orientation increases sharply within the strain range up to 88% where orientation-induced new crystals aligned in stretching direction are observed. The long period increases more in stretching direction for the crosslinked POE, consistent with larger stress in this sample, and the stress difference is more pronounced at large strains (27.3 vs. 10.9 MPa at a strain 435%). Permanent set of the crosslinked POE is smaller, consistent with less oriented crystals observed after the test for permanent set.     

Studies on curing reaction kinetics and properties of the CPE as a modifier of polyester–urethane elastomer

Chlorinated polyethylene (CPE)-modified polyester prepolymers with NCO end groups were synthesized. The chain-extension reactions of the prepolymers with 3,3′-dichloro-4,4′-diaminodiphenylmethane were studied by Fourier transform infrared spectrometry and found to change from second-order reaction at lower temperature to first-order reaction at higher temperature for these reaction systems. The properties of CPE-modified polyurethane (PU) elastomers was also studied by dynamic mechanical property analysis. The experimental results showed that the CPE content increase would lead to a decrease of the mechanical properties of PU elastomers and result in a prolongation of the cream time of curing reaction systems, but would make the manufacturing process easier than before. It is suggested that the CPE may be selected as a delayed-action activator of curing reaction. © 1996 John Wiley & Sons, Inc.     

Comprehensively improved mechanical properties of silane crosslinked polypropylene/ethylene propylene diene monomer elastomer blends

The properties and structure of silane crosslinked polypropylene (PP)/ethylene propylene diene monomer (EPDM) elastomer blends had been carried out. Fourier transform infrared spectroscopy and gel content tests were employed to evaluate the crosslinking reaction of PP/EPDM blends. Crosslinking efficiency of PP/EPDM blends was investigated using thermogravimetric analysis, differential scanning calorimeter, dynamic mechanical analysis, dynamic rheology, and tensile testing. Tanδ curves of silane crosslinked PP/EPDM blends exhibited an obvious “gel point” originated from the formation of dynamic crosslinking network. The blend corresponding to the “gel point” presented comprehensively improved mechanical properties. These results demonstrated that characteristic rheological parameters showed close correlations with key mechanical properties of silane crosslinked PP/EPDM blends. Scanning electron microscopy images illustrated that crosslinking had remarkably changed the morphologies of PP/EPDM blends. The large deformation mechanism of these blends had been suggested.     

交联三维网络结构PINPAm的制备及其性能研究

聚N-异丙基丙烯酰胺(PINPAm)水凝胶是一种亲水但不溶于水,具有交联三维网络结构的高分子聚合物,具有一定条件下的溶胀/退溶胀行为,同时具有输送和渗透性、能量转换、吸附分离、生物相容性等功能。本文研究了用不同量的引发剂过硫酸铵(APS)对水凝胶形成的影响;反应温度分别为低温(低于5℃、20℃、30℃、40℃对水凝胶形成的影响。所制备的PNIPAm水凝胶分别测定了相转变温度(LCST)和凝胶溶胀率(SR)。结果表明引发剂量用量增多时水凝胶形成反应时间变短;反应温度升高水凝胶外观出现由无色透明凝胶→乳白半透明凝胶→乳白色凝胶→乳白色且无固定形态凝胶的变化。低温生成的水凝胶相转变温度(LCST)在33~34℃之间,水凝胶体积发生不连续收缩现象;交联剂N,N-亚甲基双丙烯酞胺(BIS)使用量越多溶胀率越小。     

Reversible crosslinked low density polyethylenes: structure and thermal properties

In the present study, low density polyethylene (LDPE) has been crosslinked at 170 °C with three different systems by a) using peroxide, b) peroxide and accelerator and c), peroxide, accelerator and sulfur. The effect of chemical crosslinking on LDPE structure has been investigated using torque measurements, Fourier transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXS), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Therefore, effects of each crosslinking system on the structural and thermal properties of the material in terms of crystallinity, thermal transitions and stability have been discussed. The reversible crosslinking of LDPE allow the recyclability of polyolefins, increasing the thermal properties.     

Degradation of a poly(ether urethane urea) elastomer: infra-red and XPS studies

The potential for a poly(ether urethane urea) (PEUU) elastomer to undergo degradation, under the conditions preyalent in the biological environment, was investigated using an in vitro model system. The effect of exposing an unstabilized PEUU to an aqueous environment containing the proteolytic enzyme, papain, for one month was examined by Fourier transform infra-red spectroscopy, X-ray photoelectron spectroscopy and chromatographic methods. Evidence of degradation was observed in both enzyme- and water-treated PEUU, but was restricted to the surface regions of the polymer. Analysis of methanol extracts from polymer samples revealed evidence for the degradation of ether linkages, which was independent of the enzyme, whereas the degradation of urethane and urea groups, indicated by the detection of a primary aromatic amine degradation product, depended on the presence of the proteolytic enzyme.     

Action of hydrocarbon and ester plasticizer in urethane elastomer for sealing purposes

A comparison of the effects of two types of modifiers, anthracene oil (hydrocarbon) and dioctyl phthalate (ester), on physical and mechanical properties of urethane elastomers prepared from polyetherols (propylene oxide derivatives of various functionalities and MW) and TDI was performed. The aim of the study was to assess their suitability as binders in permanently elastic urethane sealants for use in construction. The urethane elastomers under investigation were synthesized by a prepolymer method. The modifiers, added to the reactive mixture before curing, were found to be fully compatible with the urethane elastomers and did not interfere with the curing process. The usable range of application for both modifiers was found to be up to 40 phr. Over this range the modified urethane elastomers are viscoelastic liquids. The hydrocarbon modifier does enhance the hydrophobic properties of urethane elastomer, at a lower degree of crosslinking. It was found that modified urethane elastomers may be good binders for sealants, although their long‐term sealing properties must be confirmed under field conditions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 523–529, 2001     

Mesoscopic structure and swelling properties of crosslinked polyethylene glycol in water

In this paper, we present our efforts in modeling and simulation of polyethylene glycol crosslinked with an isocyanate tHDI. The polymer, by its nature, is hydrophilic and has strong hydrogen bond interactions with water. The simulations are performed at coarse-grained scale by using a dissipative particle dynamics (DPD) simulation method. The effect of hydrogen bond between water and polymer beads on the structure of the crosslinked hydrophilic polymer structure is studied. The polymer is observed to phase separate with water in the absence of hydrogen bonds in DPD simulations. In the reverse case, where hydrogen bonds are explicitly included in DPD simulations, polymer mixes with water. This behavior is investigated by plotting the density profiles. Moreover, the volumetric swelling behavior in mixtures with different water contents is estimated from simulations and extrapolated by a polynomial fit to compare with experiments. It is observed that the predicted swelling ratio is in good agreement with the experimental measurements.