氟橡胶双酚AF/BPP硫化体系硫化特性的研究

研究了双酚AF硫化体系中硫化剂双酚AF、促进剂BPP对氟橡胶硫化特性的影响以及硫化温度对硫化特性的影响.结果表明：硫化剂双酚AF的用量主要影响胶料的交联密度以及硫化时间,并且可以改善胶料的加工性能;促进剂BPP的用量主要影响胶料的硫化时间,对加工性能有一定的影响;硫化温度的提高会使交联密度下降.     

双酚AF/BPP硫化体系对氟橡胶2462性能的影响

研究了双酚AF和BPP对氟橡胶2462性能的影响。结果表明,随着双酚AF用量的增大,胶料的最大转矩逐渐增大,强度变化较小,硫化胶压缩永久变形降低,脆性温度呈下降的趋势;随着BPP用量的增加,胶料的焦烧时间和正硫化时间缩短,硫化胶压缩永久变形增大,脆性温度逐渐升高,但是由于BPP对交联密度的提高贡献不大,因此硫化胶的力学性能变化不明显。     

配方因素对氟橡胶高温撕裂性能的影响

研究了硫化剂品种、双酚AF用量、促进剂BPP用量、补强剂品种及炭黑N990用量对不同测试温度下氟橡胶撕裂强度的影响,采用核磁共振法测定了不同温度下氟橡胶硫化胶的交联密度,研究了氟橡胶的高温撕裂强度与其交联密度间的关系。结果表明,随着测试温度的增加(25℃增加到200℃),不同配方的氟橡胶的撕裂强度均明显降低。在100~200℃温度范围内,双酚AF/BPP硫化的氟橡胶的撕裂强度高于过氧化物或胺类硫化氟橡胶的撕裂强度。随着双酚AF用量的增大,氟橡胶的常温撕裂强度明显降低,而高温撕裂强度略有下降。促进剂BPP用量增大,氟橡胶的常温和高温撕裂强度均变化不大。几种补强剂中,沉淀法白炭黑补强氟橡胶在200℃时的撕裂强度仅为25℃时撕裂强度的0.6%。测试温度从25℃升至200℃,炭黑N990补强氟橡胶的撕裂强度降低幅度较小,随着N990用量的增大,氟橡胶的常温撕裂强度增幅明显,而高温撕裂强度略有提高。测试温度升高,氟橡胶硫化胶的交联密度减小,同时撕裂强度也降低,双酚硫化时,在相同测试温度下,氟橡胶的交联密度越小,撕裂强度越大。     

氟橡胶低温性能研究

通过对不同胶种、硫化体系用量、配合剂及加工工艺的研究,发现氟橡胶在混炼前进行适度塑炼后,加入合适的配合剂,以及调整硫化剂双酚AF/促BPP用量,控制交联密度,可以使其脆性温度明显降低。     

氟橡胶中双酚AF硫化体系的硫化特性分析

研究了双酚AF硫化体系对氟橡胶硫化特性的影响。结果表明：双酚AF硫化体系中硫化剂及促进剂用量的变化对胶料的加工性能无任何影响；在硫化体系中，BPP（苄基三苯基氯化磷）对胶料友化特性的影响较双酚AF更为明显。     

低压变氟橡胶硫化体系试验的研究

对硫化剂双酚AF，促进剂BPP在氟橡胶中的应用进行了研究。结果表明，BPP用量增大，焦烧时间缩短，转矩不变，正硫化时间缩短，对胶料的硬度、伸长率、拉伸强度和撕裂强度的影响轻微；双酚AF用量增大，焦烧时间延长，转矩增大，正硫化时间延长，胶料的硬度、拉伸强度增大，撕裂强度、拉断伸长率减小，热老化后的硬度变化、拉伸强度变化率增大，伸长率变化、压缩永久变形减小。通过调整双酚AF和BPP的用量和配比，能够有效的缩短正硫化时间，提高生产效率．改善胶料的物理性能。     

双酚AF硫化体系的硫化特性分析

研究了双酚AF硫化体系对氟橡胶硫化特性的影响。研究表明采用双酚AF硫化体系对胶料的加工性能无任何影响；在硫化体系中，BPP（苄基三苯基氯我）对胶料硫化特性的影响较双酚AF更为明显。本文的研究结果为高性能氟橡胶混炼胶的设计提供依据。     

硫化体系对246型氟橡胶耐高温性能的影响

研究N，N’-双肉桂叉基-1，6-己二胺（3#硫化剂）和双酚AF／苄基三苯基氯化磷（BPP）硫化体系对246型氟橡胶硫化特性、物理性能和耐高温性能的影响。结果表明，选用2份3#硫化荆或并用比为1．5／0．6的双酚AF／BPP硫化体系的氟橡胶各项性能较好;相对而言，3#硫化剂氟橡胶的拉伸性能较好，硬度较低，有利于加工;双酚AF／BPP硫化体系氟橡胶物理性能和加工性能稍差，但耐高温性能较好。     

双酚AF/BPP硫化体系对氟橡胶性能的影响

试验研究双酚AF、苄基三苯基氯化磷（BPP）用量及一段硫化温度对氟橡胶性能的影响。结果表明，随着双酚AF用量的增大，胶料的ML减小，MH增大，t10和t90延长；硫化胶的硬度和100％定伸应力增大，拉断伸长率和拉断永久变形减小，拉伸强度呈先升后降趋势。随着BPP用量的增大，胶料的ML增大，t10和t90缩短；硫化胶的物理性能变化不大。随着一段硫化温度的升高，胶料的ML和MH减小，ts1和t90缩短；硫化胶的物理性能下降。     

三元氟橡胶硫化时硫化剂和促进剂的配方优化

对偏氟乙烯、四氟乙烯、六氟丙烯三元共聚物(F246)氟橡胶的硫化剂和促进剂进行了配方优化的研究。结果表明,促进剂用量一定时,随着双酚AF用量增加,最小扭矩M_L和最大扭矩M_H逐渐增大,T_(S2)和TC_(90)时间也逐渐延长;双酚AF用量一定时,随着苄基三苯基氯化磷(BPP)的用量增加可大幅度缩短焦烧时间和正硫化时间。双酚AF用量增加,混炼胶拉伸强度变化不大,伸长率下降明显,硬度略有增加,压缩永久形变降低,脆性温度呈下降趋势;BPP用量增加,混炼胶拉伸强度和伸长率变化不大,硬度略有增加,压缩永久形变大,并且氟橡胶脆性温度呈上升趋势;综合各因素,双酚AF与BPP的质量分别为F246的2.5%和0.6%为宜。     

FKM/ACM并用胶的结构及性能研究

对采用双酚AF/促进剂BPP硫化体系的氟橡胶(FKM)/丙烯酸酯橡胶(AcM)并用胶的各项性能进行研究.结果表明:以双酚AF/促进剂BPP为硫化体系,FKM和ACM可以实现共硫化,制得的FKM/ACM并用胶物理性能优良,耐热氧、耐紫外光和耐臭氧老化性能以及热稳定性较好,压缩永久变形性能优异}扫描电子显微镜显示FKM和ACM具有较好的相容性.     

N‐(2‐biphenylenyl)‐4‐[2′‐phenylethynyl] phthalimide: 2. Detailed study of the monomer cure and properties of the resulting polymer

A detailed study is presented of the high‐temperature cure of the difunctional monomer N‐(2‐biphenylenyl)‐4‐[2′‐phenylethynyl]phthalimide (BPP) and the thermal properties of the resulting homopolymer. Although the phenylethynyl groups are consumed within 1 h at 370 °C, other reactions continue well after this, leading to a cured polymer whose glass transition temperature (T_g) is highly dependent on cure time and temperature. A T_g of 450 °C is achieved after a 16 h cure at 400 °C. Use of chemometrics to analyse the infrared spectra of curing BPP provides evidence for changes in the aromatic moieties during cure, perhaps indicative of co‐reaction between the biphenylene and phenylethynyl groups; however, other processes also contribute to the overall complex cure mechanism. Despite the high T_g values, BPP homopolymer exhibits unacceptably poor thermo‐oxidative stability at 370 °C, showing a weight loss of about 50 % after 100 h ageing. This is perhaps a result of formation of degradatively unstable crosslink structures during elevated‐temperature cure. Copyright © 2004 Society of Chemical Industry     

Moisture absorption by cyanate ester modified epoxy resin matrices. Part IV: Effect of curing schedules

The cure schedule (time and temperature) has a profound effect on the physical properties of thermosetting materials. For hydrophilic systems, it can also influence the rate of diffusion of moisture and the equilibrium concentration. The effect of post‐cure time and temperature on the moisture sorption behavior and the viscoelastic properties of cyanate ester modified epoxy resin has been investigated. Moisture absorbed at 96% R.H. (relative humidity) and 50°C under isothermal conditions was found to increase with post‐cure temperature, but the diffusion coefficient decreased in line with the crosslink density. Resins of high crosslink density and high glass transition temperature appeared to exhibit a larger reduction in glass transition temperature on plasticization by moisture in comparison to those with lower crosslink density.     

盐雾条件下氟橡胶与金属粘接用胶粘剂的研究

通过对几种不同类型的氟橡胶胶粘剂在常规和盐雾条件下的试验对比,发现双酚AF/BPP硫化体系的氟橡胶与金属骨架的粘接性能中,树脂类胶粘剂在盐雾条件下的防锈性能明显优于其他类型的胶粘剂。批量生产验证表明,树脂类胶粘剂在盐雾24 h条件下,粘接性能变化率最小,仅为2.29%,外观颜色为浅绿色,表面均匀度好。     

The effect of stoichiometry on the fracture toughness of a liquid crystalline epoxy

The fracture toughness of a liquid crystalline epoxy was compared with that of a standard bisphenol‐A based epoxy to understand how both the liquid crystalline structure and the crosslink density affect fracture toughness. For the liquid crystalline epoxy, the liquid crystalline domain size decreased with increasing temperature of cure and away from the stoichiometric formulation. Quantitative fractography showed that there is a competition between the liquid crystalline domain structure and the stoichiometry in determining the fracture toughness. At some cure conditions the effect of the domains is dominant. When the cure conditions are adjusted to reduce the domain size, the domains become too small to affect the fracture toughness, and thus the effect of the stoichiometry is dominant. The result is that the formation of liquid crystalline structure only increases the fracture toughness relative to that of a traditional epoxy at and near the stoichiometric formulation.     

Effect of vulcanization temperature and vulcanization systems on the structure and properties of natural rubber vulcanizates

The effect of vulcanization temperature (150°–180°C) on the structure and technical properties of gum natural rubber vulcanizates with four different 2-(morpholinodithio)-benzothiazole: sulphur ratios (A, 0.6:2.4; B, 1.5:1.5; C, 2.4:0.6; D, 3.0:0.0) at the respective optimum cure times has been determined. The influence of cure temperature on (a) the chemical crosslink density; (b) the distribution of crosslink types; (c) the extent of sulphidic main chain modifications and (d) the zinc sulphide formation was investigated. Results show that elevated cure temperatures produce a network with lower crosslink density, in particular a lower polysulphidic crosslink density. The formation of intramolecular sulphidic groups and zinc sulphide increase with increasing cure temperatures. The possibility of chain scission during vulcanization, as examined by a quantitative analysis of the sol—gel data, was found to be negligible. The network results have been correlated with the technical properties.     

Effect of stoichiometry and cure prescription on fluid ingress in epoxy networks

Stoichiometry and cure temperature were evaluated for epoxy systems based on the diglycidyl ethers of bisphenol‐A and bisphenol‐F and cured with 3,3′‐ or 4,4′‐diaminodiphenylsulfone. The materials were formulated as stoichiometric benchmarks and with an excess of epoxide and cured in two steps (125°C/200°C) or one step (180°C). Dynamic mechanical analysis and free volume testing indicated decreased crosslink density and increased chain packing in the excess‐epoxy materials, as well as a narrowing gap in properties between 33‐ and 44‐cured networks with excess epoxy. The narrowing gap was less pronounced in materials cured at 180°C. The excess‐epoxy materials were more resistant to water ingress, exhibiting reduced equilibrium water uptake. The excess‐epoxy materials were also more resistant to methyl ethyl ketone ingress, which occurred at a slower rate in most excess‐epoxy materials. The improvement in fluid resistance was attributed to enhanced chain packing in the materials with lower crosslink densities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013