聚氨酯弹性体的耐热性能

指出影响ＰＵ 弹性体耐热性能的主要因素有软段（ 聚酯、聚醚） 、二异氰酸酯、扩链剂、硬段浓度、温度、时间及介质（ 包括气体、水、油） 对ＰＵ 弹性体高温下和高温老化后某些力学性能的影响。     

丙烯酸树脂改性的水性聚氨酯性能与结构

采用丙烯酸树脂（ＰＡ或ＰＡ’）对水性聚氨酯（ＰＵ）改性,研究了丙烯酸树脂改性的水性聚氨酯的性能与结构。结果表明：设计ＰＵ分子链硬段与ＰＡ分子链形成化学键,材料中ＰＵＡ及ＰＵ／ＰＡ中ＰＵ分子链硬段与ＰＡ分子链具有较高的相容性和共混程度;机械共混物ＰＵ／ＰＡ中ＰＵ分子链、ＰＡ分子链之间的共混主要集中于ＰＵ乳胶粒、ＰＡ乳胶粒表层;ＰＵＡ及ＰＵＡ’材料ＰＵ分子链与ＰＡ分子链之间处于一同相分离状态。ＰＵＡ’     

丙烯酸树脂改性的水性聚氨酯结构设计及表征

设计聚氨酯（ＰＵ） 、丙烯酸树脂（ ＰＡ）２ 种树脂的机械共混、化学共混即核－ 壳型聚合过程，及设计该２ 种树脂分子链之间形成的化学键，研究了用丙烯酸树脂改性的水性聚氨酯。分析乳胶粒大小及分布、胶膜材料红外光谱及ＤＳＣ 特征曲线表明：设计ＰＵ 分子链硬段与ＰＡ 分子链形成化学键，得到的材料中ＰＵＡ 及ＰＵ／ＰＡ 中ＰＵ 分子链硬段与ＰＡ 分子链具有较高的相容性和共混程度；核－ 壳型聚合得到的ＰＵＡ 及ＰＵＡ′材料ＰＵ 分子链与ＰＡ 分子链之间处于一定的微相分离状态；机械共混物ＰＵ／ＰＡ 中ＰＵ 分子链、ＰＡ 分子链之间的共混主要集中于ＰＵ 乳胶粒、ＰＡ 乳胶粒表层。     

不饱和聚酯/苯乙烯无皂乳液共聚合与聚合物微凝胶

以羧基封端的不饱和聚酯（ＵＰ）和苯乙烯（Ｓｔ）为单体进行了无皂乳液共聚合,制备了聚合物微凝胶,提出了ＵＰ－Ｓｔ无皂乳液聚合的成核机理,讨论了ＰＨ值、ＵＰ／Ｓｔ等因素对体系稳定性和微凝胶产率的影响,该聚合物微凝胶能明显提高ＵＰ的冲击强度。     

氨纶氯水降解及耐氯机理的探讨

应用红外光谱分析方法，对氨纶（ＰＵ纤维）氯水降解及耐氯机理进行了初步的研究。结果表明，ＰＵ浸氯水后，因受活性氯原子的攻击，ＰＵ大分子软链段的碳－碳键发生断裂，形成碳－氯化合物，添加剂加入后，因与ＰＵ大分子的软链段形成螯合物，从而避免了活性氯原子的攻击，有效地保护了软链段，使氨纶耐氯性能明显改善。     

聚氨酯改性软质PVC塑料的研制及其性能研究

采用共混反应一步挤出新方法研制了聚氨酯（ＰＵ）改性软质ＰＶＣ塑料，考察并确定了最佳工艺条件，并对ＰＵ－ＰＶＣ共混改性塑料的性能进行了研究，确定了聚氨酯的合适组成为４，４＇－二苯基甲烷二异氰酸酯、ＰＥ－３聚酯二元醇和乙二醇扩链剂（其配比为－ＮＣＯ－ＯＮ＝１．０５）及聚氯乙烯树脂的合适分子量（平均聚合度为１３００）；同时还考察了无机填料对ＰＵ－ＰＶＣ改性塑料性能的影响，结果表明，合适填料的加入，不仅能     

硬段含量对聚酯型聚氨酯弹性体形态与性能的影响

采用本法合成了一系列不同硬段含量的聚（１，４－丁二醇己二酸）酯型聚氨酯（简称ＰＢＡ型ＰＵ）弹性体，并用ＤＳＣ，ＷＡＸＤ，ＴＥＭ，ＳＥＭ，ＳＡＸＳ测试手段对其微相分离程度和结晶形态进行了表征，测定了材料的拉伸性能，讨论了硬段含量对材料形态与性能的影响。结果表明：ＰＢＡ型ＰＵ弹性体中微相分离程度以及软，硬链段的结晶性随硬段含量的提高而变化。拉伸性能受其内部微相分离程度和链段结晶性的相互影响。     

两亲聚氨酯弹性体(APU)的研究Ⅱ.IPN型APU制备及力学性能

以聚酯型聚氨酯为疏水组分,光固化聚乙二醇为亲水组分,通过溶液聚合制备了具有互穿聚合物网络（ＩＰＮ）结构的ＡＰＵ。研究了亲疏水组分比例、光固化条件等因素对ＩＰＮ型ＡＰＵ力学性能的影响。试验结果表明,当ＡＰＵ中光敏剂质量分数为００１０,光照前停放２０ｈ,光照时间为６ｍｉｎ时,ＩＰＮ型ＡＰＵ的力学性能最佳。     

PU的性能及应用

简要介绍了聚酯型ＰＵ和聚醚型ＰＵ的基本性能和合成方法;阐述了从加工方法上所分的３种类型ＰＵ（浇注型ＰＵ、注射型ＰＵ和混炼型ＰＵ）的合成方法和性能特点;列举出ＰＵ的主要用途。     

聚苯乙烯的苯甲酰基化反应研究

合成并表征了具有芳香酮侧链结构的苯甲酰基聚苯乙烯（ＢＰＳ）,讨论了反应时间、温度、溶剂、催化剂及投料比对聚苯乙烯（ＰＳ）转化为ＢＰＳ的转化率和交联反应的影响,结果表明,ＰＳ在合适条件下可转化成ＢＰＳ,ＰＳ转化成ＢＰＳ后其ＵＶ吸收强度明显增大     

氢化丁苯橡胶的性能与表征

用IR,DSC,TEM表征了由丁苯胶乳氧化制备的氧化丁苯橡胶（HSBR）的微观结构及结晶状态,并测定了HSBR老化前后的力学性能,结果表明,HSBR在较高氢化下形成了较多的结晶聚乙烯链段,具有较好的力学性以,优异的耐热老化性及耐候稳定性,HSBR的氢化度愈高,结晶度愈大,物理机械性能愈优异,可作为优良的耐老化型热塑性弹性体。     

盾构管片专用胶的研制及应用

以端羧基液体丁腈橡胶、环氧树脂、增稠剂、着色剂等为主要材料,研制了一种盾构管片专用的改性环氧树脂胶粘剂。通过将三元乙丙橡胶密封条和丁腈软木衬垫粘接在盾构管片上,有效地解决了盾构管片的渗水和安装问题。实验结果表明,制备的胶粘剂拉伸强度和剥离强度均满足设计要求,具有强度高、耐水性和耐老化性强等优点。     

Thermal aging study of carboxyl-terminated polybutadiene and poly(butadiene-acrylonitrile)-reactive liquid polymers

A thermal aging study of carboxyl-terminated polybutadiene (CTB) and poly(butadiene-acrylonitrile) (CTBN) reactive liquid polymers has been conducted at 50°, 75°, 100°, and 125°C. All CTB and CTBNs are stable at 50°C aging. On aging at higher temperatures prior to use, viscosities of CTB and CTBNs increase, and terminal carboxylic acid functional groups start disappearing. Rate of viscosity increase and rate of carboxylic acid functional group disappearance increase with higher aging temperature and also with higher cyano group concentration in the polymers. The major cause of rapid viscosity increase and disappearance of carboxylic acid functional groups seems to be crosslinking between terminal carboxylic acid groups and cyano groups, which form imide structures. Crosslinking among the unsaturation in polybutadiene segments may contribute to the slow, steady viscosity increase. No acid-anhydride formation and decarboxylation reaction, which may also result in viscosity increase and disappearance of carboxylic acid functional groups, are observed during the thermal aging at elevated temperatures.     

Weibull statistics in electrical aging of polyesterimide under AC voltage

This article is aimed at the investigation of electrical aging of polyesterimide under AC voltage using Weibull statistical analysis. It's shown that the time to breakdown characteristic (V–t) of polyesterimide includes two zones (segments of straight line). The first zone characterizes a statistical dispersion of the intrinsic defects of material. The second zone expresses the real aging of polymer. The variation of the slope of lifetime curve is attributed to the change in the degradation mechanism. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Aging-induced structural relaxation in cornstarch plasticized with urea and glycerol

In present work structural properties and aging of thermoplastic starches prepared by plasticization of cornstarch with urea, glycerol and their mixtures are studied using solid-state ¹H NMR and ¹³C NMR spectroscopy and WAXS measurements. Broad line ¹H NMR spectra reveal phase separation of plasticizers during aging of the samples with the same or higher relative amount of glycerol than the amount of urea. Glycerol in the TPS samples induces motion of starch chain segments, the mobility of which depends on the relative amount of glycerol. At the scale of nm, formation of B-type crystallites in the samples containing glycerol and also of single-helical crystallinity in all samples is observed during one-year aging through cross-polarization magic angle spinning ¹³C NMR spectra. Urea, when used as the sole plasticizer, prevents the ordering of starch chains in B-type crystallites. WAXS diffractograms show that regular crystals do not form in any of the samples.     

Aging behavior of a hot‐cured epoxy system

The thermal and hydro‐thermal aging of a hot‐cured epoxy system (diglycidylether of bisphenol A (DGEBA) + dicyandiamide (DDA)) in the glassy state is revisited using DSC and IR attenuated total reflection spectroscopy. Because of the diffusion of DDA from the solid particles into the liquid DGEBA matrix, curing produces a highly crosslinked amorphous matrix that contains low crosslinked amorphous regions. After full curing, the network possesses a relatively low molecular mobility and no residual reactive groups. Thermal and hydro‐thermal loading is performed at 60°C, well below the principal glass transition temperature (T_g1 = 171°C). Both aging regimes cause significant chemical and structural changes to the glassy epoxy. It undergoes a phase separation of relatively mobile segments inside the low mobile matrix, providing a second glass transition that shifts from T_g2 = 86–114°C within 108 days of aging. This phase separation is reversible on heating into the viscoelastic state. Hydro‐thermal aging leads to a reversible and a nonreversible plasticizing effect as well. On thermal aging, no chemical changes are observed but hydro‐thermal aging causes significant chemical modifications in the epoxy system. These modifications are identified as a partial degradation of crosslinks produced by the cyano groups of the DDA and correspond to the nonreversible plasticitation. These changes in the cured epoxy should exert an influence on the mechanical properties of an adhesive bond. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

The effects of thermoform molding conditions on polyvinylchloride and polyethylene double layer package materials

This work reports the effects of thermoform molding process conditions on polyvinylchloride (PVC) and polyethylene (PE) double layer package materials. Mechanical and microstructural properties of the package material were examined by different test methods which are tensile properties, tear resistances and scanning electron microscopy (SEM). Furthermore, package materials, which are produced in different conditions by thermoform molding. Effect of different mold depths and process temperatures on the samples are determined by thermal aging process at 60°C in first, third, and seventh days. With increase in mold depth from 25 mm to 75 mm, there is a significant increase in tensile strength from ～45 MPa to ～55 MPa, thermoform temperature at 150°C. The highest elongation of the material was obtained thermoform temperature at 165°C as 80%, mold depth at 35 mm. Tensile strength and elongation (%) of the material generally decrease by aging time with changing of mold depth (25, 35, and 75 mm) of the double layer package material. In addition, tear resistances of the material decrease via aging time in various thermoform temperatures (150°C, 165°C, and 175°C) due to the orientation of the segments. Scanning electron microscopic (SEM) images of the materials were taken for aging process in first, third, and seventh days. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Alkyl Tail Segments Mobility as a Marker for Omega-3 Polyunsaturated Fatty Acid-Rich Linseed Oil Oxidative Aging

Omega-3 polyunsaturated fatty acid (PUFA)-rich linseed oil (LSO) is an important component in biological systems, foods, and many other industrial products. In recent years, LSO has attracted increased attention in the field of functional foods, which has highlighted its facile susceptibility to aging by autoxidation. Common colorimetric and a long list of spectral methodologies have been used to follow after and predict LSO shelf life's quality, especially in regards to aging by autoxidation. These standard methodologies are nevertheless limited, because of the complexity of the LSO's chemical and physical changes. The goal of the present study is to develop a sensorial ¹H LF-NMR energy relaxation time application based on monitoring primary chemical and structural changes occurring with time and temperature during oxidative thermal stress for better and rapid evaluation of LSO's aging process. Using ¹H low-field NMR, the different T₂ times of energy relaxations due to spin–spin coupling, and proton motion/mobility of LSO molecular segments were monitored. As previously reported, we characterized the chemical and structural changes in all phases of the autoxidation aging process. Starting from the initiation phase (abstraction of hydrogen radical, fatty acid chain rearrangement, and oxygen uptake yielding hydroperoxides products), through to the propagation phase (chain reactions resulting in tail cleavage to form alkoxy radicals, and alpha, beta-unsaturated aldehydes formation), and a termination phase (cross linking and production of polymerization end products). The ¹H LF NMR transverse relaxation approach, monitors both the covalent bond's strong forces (100–400 kJ mol⁻¹) in LSO oxidative aging decomposition, as well as secondary relatively weak interactive forces by hydrogen bonds (~70 kJ mol⁻¹), and electrostatic bonds (0–50 kJ mol⁻¹) contributing to secondary crosslinking interactions leading to a LSO viscous gel of polymerized products in the termination phase. In the present paper, we show that LSO tail segments mobility in terms of T₂ multi-exponential energy relaxation time decays, generated by data reconstruction of ¹H transverse relaxation components are providing a clear, sharp, and informative understanding of LSO sample's autoxidation aging processes. To support T₂ time domain data analysis, we used data from high-field band-selective ¹H NMR pulse excitation for quantification of hydroperoxides and aldehydes of the same LSO samples treated under the same thermal conditions (25, 40, 60, 80, 100, 120 °C) with pumped air for 168 hours. Peroxide value, viscosity, and self-diffusion analyses, as well as fatty acids profile and by-products determined by GC–MS on the same samples were carried out, and correlated with the LSO tail T₂ energy relaxation time results. From these results, it is postulated that selective determination of LSO tail T₂ time domain can be used as a rapid evaluation marker for following omega-3 PUFA-rich oils oxidative aging process within industrial and commercial products.     

New aspects of aging in epoxy networks. I. Thermal aging

The thermal aging of an amine‐cured epoxy in the glassy state is studied for two network states by using DSC and attenuated total reflection‐infrared (IR‐ATR). The “low‐crosslinked” network possesses a relatively high molecular mobility and a considerable amount of residual reactive groups. In the low crosslinked matrix, the presence of high crosslinked regions is revealed. In contrast, the “highly crosslinked” epoxy system has a reduced molecular mobility and only small reactive groups. The high crosslinked matrix contains low crosslinked regions. Thermal loading for both networks is performed below their glass transition. During thermal aging, an ongoing curing reaction takes place in the low‐crosslinked epoxy. Thermooxidative degradation and the disintegration of short‐range ordering are observed as well. The highly crosslinked epoxy system undergoes a phase separation of relatively mobile segments in the low mobile matrix, which is a reversible process on heating. Thermooxidative degradation is also detected for this kind of network. In summary, for the “low” and the “highly” crosslinked epoxy, significant chemical and structural changes take place during thermal aging even though the networks are vitrified. It is convincing that these changes in the cured epoxy should exert an influence on the mechanical properties of a bonded structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 361–368, 2004     

Hexamethyl cyclotrisiloxane–styrene block copolymers and their chemical composition

Triblock copolymers of hexamethyl cyclotrisiloxane (D₃) and styrene were synthesized by first preparing “living” species of polystyrene dianion followed by polymerization of D₃. The chain lenght of polymeric blocks could be controlled in a predictable fashion leading to a central hard block of polystyrene and the two end segments of amorphous polydimethylsiloxane having narrow molecular weight distribution, were characterized by gel permeation chromatography. The chemical composition of block copolymers was determined by silicon analysis and infrared and nuclear magnetic resonance spectra. Thermal aging of block copolymers at 150, 200, and 300°C was also discussed.