环氧氯丙烷橡胶的热可逆共价交联

以环戊二烯二羧酸钾 [DCPD(COOK) 2 ]为交联剂 ,采用溶液反应法使环氧氯丙烷橡胶 (环氧氯丙烷均聚物 ,CER)交联 ,制得了凝胶含量达 88 75 %的交联CER ,研究了溶剂种类、反应温度、催化剂及交联剂用量对凝胶形成量的影响 .IR谱证明 ,DCPD(COOK) 2 与CER发生双端酯化而交联 ;反应溶解性试验表明 ,该共价交联聚合物具有热可逆转化特性 ,热可逆转化百分率随反应温度的提高、交联剂用量的增多而下降     

聚氯乙烯的热可逆共价交联

利用环戊二烯 (CPD)在常温下自动二聚形成双环戊二烯 (DCPD)、在高温下DCPD又可解聚成CDD的热可逆Diels Alder反应 ,合成了DCPD二羧酸衍生物 ,并将其引作聚氯乙烯 (PVC)的共价交联 ,研究了交联剂种类和用量对交联程度、力学性能和流动特性的影响及交联产物的热可逆转化行为 ,制得了力学性能和耐热性均有所提高的热可逆共价交联PVC     

热可逆共价交联氯化聚乙烯的制备和性能

以双环戊二烯二羧酸钾 [DCPD(COOK) 2 ]为交联剂 ,通过共混反应法制得了共价交联的氯化聚乙烯(CPE)热塑性弹性体 (TPE) ,研究了共混反应条件 (温度、时间及交联剂用量等 )对TPE物性的影响 .反应溶解性和IR测定数据证明 ,DCPD(COOK) 2 与CPE分子链上的活性氯反应形成共价酯键而交联 ;物性测定数据表明 ,交联CPE的主要力学性能接近CPE常规硫化胶 ,不同的是该交联聚合物具备可塑性 ,经反复加工三次后 ,其力学性能还略有提高     

活性氯型丙烯酸酯橡胶的热可逆共价交联

利用热可逆季铵化反应特性,将含叔胺功能基团的聚合物用于活性氯型丙烯酸酯橡胶(ACM)的热可逆共价交联。通过乳液聚合方法合成了丙烯酸丁酯(BA)/4-乙烯基吡啶(4-VP)共聚物交联剂,考察了交联剂用量、模压温度和模压时间对ACM交联程度、力学性能的影响,并通过DSC、变温扭矩测定、热塑再加工成型等方法研究了交联ACM胶样的热可逆性。研究表明,BA-4-VP共聚物交联的炭黑填充ACM胶样拉伸强度可达8.5MPa,并可进行热塑模压成型,再次加工成型后胶样断裂强度增大、伸长率下降。     

丙烯酸乙酯/烯丙基缩水甘油醚共聚物的热可逆共价交联

研究了双环戊二烯基二羧酸及其铵盐对丙烯酸乙酯 /烯丙基缩水甘油醚共聚物的交联反应 ,对比了二者的交联速度 .用DSC评价了它们的热可逆转化行为 .制得了热可逆部分达 79 7%的共价交联环氧型丙烯酸酯橡胶     

开环共聚法合成热可逆共价交联聚醚橡胶

以烷基铝为催化剂,双环戊二烯二甲酸双缩水甘油酯为交联单体,与环氧氯丙烷、环氧乙烷、环氧丙烷进行离子型开环共聚,制得了热可逆共价交联的聚醚橡胶．研究了聚合方法、聚合配方和工艺条件对单体转化率、共聚物组成的影响．通过 Ｉ Ｒ 和 Ｄ Ｓ Ｃ 测定及反应溶解性和高温成型实验,证明了共聚物的结构及共价交联的热可逆转化特性．     

热可逆共价交联反应及其研究进展

梗概评述了环戊二烯（ＣＰＤ）与双环戊二烯（ＤＣＰＤ）之间Ｄｉｅｌｓ－Ａｌｄｅｒ反应的特点,以及将其引作大分子间交联键的思路;以此为基础详细讨论了热可逆共价交联聚合物的分析方法。制备路线,以及利用这一反应目前所达到的研究水平和成就 。     

热可逆交联环氧树脂的动态结构与性能研究

通过双马来酰亚胺与侧链带有呋喃官能团线性环氧树脂间的Diels-Alder反应,制备了热可逆交联的环氧树脂(DAERs),通过热分析、固体核磁共振技术和力学性能测试详细研究了该热可逆交联聚合物中的热可逆转变过程、动态化学键演化以及交联度对力学性能的影响.示差扫描量热法(DSC)和动态热机械分析(DMA)等热分析结果表明,可逆共价键的化学交联作用提高了材料的玻璃化转变温度,随着交联度的增大,热可逆共价键断裂及玻璃化转变协同作用导致材料软化温度显著提高,进而提高了材料的耐热性.通过变温13C固体NMR实验原位监测DA/retro-DA反应过程,发现DAERs中通过DA反应形成的交联网络结构可以在高温解交联而生成呋喃与马来酰亚胺小分子化合物,而低温时呋喃与马来酰亚胺化合物又再次反应得到DA加成结构,进而从分子水平上为材料的热可逆交联特性提供了关键的实验证据.而原样品和溶液法再加工样品的拉伸实验结果表明,可逆交联DA反应不但使样品具有较高的力学强度,而且使交联聚合物具有了再加工的能力.     

低交联聚乙烯后交联的研究(Ⅱ)

本文用四氯化碳为后交联剂,通过Friedel—Crafts反应使低交联聚苯乙烯发生后交联,形成大孔树脂。用正交试验法考查了反应时间,反应温度,后交联剂用量,催化剂用量和溶剂组成对树脂孔结构的影响。后交联得到的树脂的比表面积和孔容分别可达到484m~2/g和0.42ml/g。     

胍胶压裂液体系有机硼交联剂合成研究进展

胍胶压裂液是目前压裂作业中应用最多的工作液,但存在胍胶用量高、残渣量大、储层伤害严重的问题。有机硼交联剂因交联性能优异、延迟交联易调控、压裂液破胶彻底、可降低胍胶用量、减少胍胶残渣对储层的伤害,是目前胍胶压裂液体系交联剂的主要研究方向。文章介绍了胍胶压裂液体系有机硼交联剂的研究进展,探讨了有机硼交联剂的交联作用机理,重点总结了有机硼交联剂的合成研究情况,在此基础上对今后发展方向进行了展望。从合成研究情况来看,有机硼交联剂主要有多种配体复合制备、长链多头极性有机胺硼制备、纳米交联剂制备三种方式,在降低胍胶用量、提高压裂液携砂性能方面表现优异。今后研究中应以提高交联效率为关键,长链多头极性结构是主要研究方向,有机配体的优选和反应设计将是研究的核心问题。     

Emulsion procedures for thermally reversible covalent crosslinking of polymers

Quaternization and dequaternization of tertiary amine compounds were employed to obtain thermally reversible ionene networks from aqueous colloidal polymer dispersions prepared via emulsion polymerization. Chlorine‐functionalized polymers prepared via the emulsion copolymerization of styrene (St), butylacrylate (BA), or both with chloromethylstyrene, and amino‐functionalized polymers prepared via the emulsion copolymerization of St, BA, or both with 2‐(dimethylamino)ethylacrylate or 4‐vinylpyridine, were reacted without polymer separation, with a ditertiaryamine crosslinker and a dihalide crosslinker, respectively, to obtain crosslinked polymers. Crosslinked polymers were also obtained via the reaction of a chlorine‐functionalized polymer dispersion with an amino‐functionalized polymer dispersion or via the drying of the polymer blend prepared from the two kinds of dispersions. Reactive solubility experiments, flowability investigations (by thermocompression at ca. 215 °C), IR, and ¹H NMR analyses of the obtained crosslinked polymers indicated that the generated ionene bridges dequaternized on heating and requaternized on cooling. In comparison with solution crosslinking, no organic solvent was employed, and simple procedures were required for the preparation of the thermally reversible covalent crosslinked polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4373–4384, 2000     

Thermally reversible linking of halide-containing polymers by potassium dicyclopentadienedicarboxylate

A novel crosslinker for thermally reversible covalent (TRC) linking of halide-containing polymers is suggested. Chlorine-containing polymers such as chloromethylstyrene copolymers, chlorinated polypropylene, polyvinylchloride, chlorinated polyisoprene, and polyepichlorohydrin were crosslinked with potassium dicyclopentadienedicarboxylate (KDCPDCA). The crosslinker was prepared by reacting potassium ethoxide with dicyclopentadienedicarboxylic acid. Because of the low solubility of KDCPDCA in organic solvents, a phase transfer catalyst, benzyltrimethyl-ammonium bromide, was employed for the crosslinking reaction. The crosslinking reaction occurred at a higher rate in a polar solvent, such as dimethylformamide, than in a nonpolar one, such as toluene, and was affected by the nature of the chlorine-containing polymer. Some of the polymers crosslinked even at room temperature. The chain-extending reaction between KDCPDCA and a α,ω-dihalide compound such as α,α′-dichloro-p-xylene, 1,4-dichlorobutane, or 1,4-dibromobutane also was carried out to obtain linear oligomers. The IR spectra indicated that the crosslinking and chain-extending reactions were based on the esterification between the halide carbon bonds of the polymer and the COOK groups of KDCPDCA. The flowability at 195 °C and solubility on heating in a dichlorobenzen-maleic compound mixture of the crosslinked polymers indicated that the TRC crosslinking occurred via the reversible Diels–Alder cyclopentadiene/dicyclopentadiene conversion as long as the polymer was thermally stable and did not contain olefinic CC bonds. The TRC linking also was confirmed by the rapid decrease of the specific viscosity of the obtained linear oligomers on heating. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4390–4401, 1999     

Synthesis of crosslinked poly(butyl methacrylate‐co‐pentaerythritol triacrylate) gel by single electron transfer‐living radical polymerization and its oil‐absorbing properties

A novel high oil‐absorbing crosslinked gel was synthesized by copolymerization of butyl methacrylate (BMA) with a small amount of pentaerythritol triacrylate (PETA) crosslinker using single electron transfer‐living radical polymerization (SET–LRP) initiated with carbon tetrachloride (CCl₄) and catalyzed by Cu(0)/hexamethylenetetramine (HMTA) in N, N‐dimethylformamide (DMF). The polymerization followed first‐order kinetics as indicated by linear increase of monomer concentration with reaction time. Effects of reaction temperature, crosslinker, initiator, and catalyst on the oil‐absorbing properties of the crosslinked gel were investigated in detail. The oil absorptions of the crosslinked gel to chloroform, toluene could reach 51.9, 34.5 g/g, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cross-linking of Polymer of Intrinsic Microporosity (PIM-1) via nitrene reaction and its effect on gas transport property

Polymer of Intrinsic Microporosity (i.e. PIM-1) has been crosslinked thermally via nitrene reaction using polyethylene glycol biazide (PEG-biazide) as a crosslinker. The crosslinking temperature was optimized using TGA coupled with FT-IR spectroscopy. The dense membranes containing different ratios of PIM-1 to PEG-biazide were cast from chloroform solution. Crosslinking of PIM-1 renders it insoluble even in excellent solvents for the uncrosslinked polymer. The resulting crosslinked membranes were characterized by FT-IR spectroscopy, TGA and gel content analysis. The influence of crosslinker content on the gas transport properties of PIM-1, its density and fractional free volume (FFV) were investigated. Compared to the pure PIM-1 membrane, the crosslinked PIM-1 membranes showed better gas separation performance especially for CO₂/N₂, CO₂/CH₄ and propylene/propane (C₃H₆/C₃H₈) gas pairs and as well as suppressed penetrant-induced plasticization under high CO₂ pressure.     

Investigation of thermo-reversibility of polymer crosslinked by reversible covalent bonds through torque measurement

Brominated butyl rubber (BIIR) was crosslinked through an esterification reaction using the sodium salt of dicyclopentadiene dicarboxylic acid (DCPDCA) as crosslinking agent. The crosslinked BIIR could de-crosslink upon heating and re-crosslink upon cooling due to Diels-Alder type reversible de-dimerization/re-dimerization of dicyclopentadiene moieties in the rubber networks. Torque measurement of the crosslinked rubber was conducted at various temperatures using a typical curemeter to investigate the thermo-reversibility. It was revealed that proper temperature for thermal processing of the crosslinked BIIR would be around 174 °C, at which the crosslinked polymer exhibits good flowability and is not too high to induce unexpected side reactions. The torque measurement was also carried out to investigate the efficiency of antioxidant on retarding the loss of the thermo-reversibility of the crosslinked polymer during heating-cooling cycles. It was found that addition of antioxidant 2246 [2,2′-methylenebis(6-tert-butyl-4-methylphenol)] into BIIR could significantly improve the thermo-reversibility of DCPDCA crosslinked BIIR. Torque measurement provides a convenient and sensitive method to understand the thermal behavior of reversible covalent crosslinked polymer.     

增塑化学微交联聚氯乙烯中化学交联和物理交联的协同作用

由氯乙烯／ 邻苯二甲酸二烯丙基酯（ＶＣ／ＤＡＰ） 悬浮共聚合成了化学微交联聚氯乙烯（ＰＶＣ） 树脂,并进行增塑加工．共聚得到的化学交联ＰＶＣ 具有溶胶／ 凝胶分配特性,交联密度较低;化学交联ＰＶＣ 的溶胶和凝胶均存在分子链缠结作用,尤其当凝胶含量较高时,物理缠结对凝胶交联密度有较大贡献．化学交联对增塑ＰＶＣ 结晶性的影响较小,因此在增塑化学微交联ＰＶＣ 中同时存在化学交联网络和以分子链物理缠结点和微晶为交联点的物理交联网络,两者协同影响增塑ＰＶＣ 材料的性能．