阴离子端羟基聚丁二烯的表征及其固化物的力学性能

简述了以硅烷保护羟基的烷基锂为引发剂,环己烷为溶剂合成丁羟胶的聚合方法;通过IR、^1H—NMR和GPC等方法研究了阴离子端羟基聚丁二烯主链结构、分子质量分布、官能度及其分布;对其固化物力学性能进行了评价。研究结果表明,阴离子端羟基聚丁二烯的1,4-结构含量高达约90％、分子质量分布指数≤1．05、官能度接近2,其固化物具有优异的力学性能。     

GPC法测定HTPB的官能度分布

端羟基聚丁二烯(HTPB)是一种重要的预聚物。据报道,HTPB的分子量(Mi)、分子量分布、官能度(f)和官能度分布对其物理和加工性能均有很大的影响。因此,对HTPB官能度分布的研究,具有十分重要的意义。 HTPB在聚合过程中,由于无法控制链的转移而产生了不同的官能度。预聚物的官能度被定义为预聚物的数均分子量(Mn)     

端羟基聚丁二烯官能度对推进剂力学性能的影响研究

通过凝胶渗透色谱（GPC）测定端羟基聚丁二烯（HTPB）样品的平均相对分子质量,化学滴定测定样品羟值,根据相对分子质量和羟值计算得到产品的平均官能度。通过假设交联密度和交联点间相对分子质量分别与推进剂抗拉强度和延伸率成正比,建立简单的官能度数学模型,阐述了平均官能度对推进剂力学性能的影响,同时官能度变化可很好地解释HTPB推进剂固化“活性”的差异。     

三臂星形端羟基聚丁二烯的阴离子合成及其表征

以叔丁基二甲基硅氧基丙基锂为引发剂,环己烷为溶剂进行阴离子聚合合成三臂星形端羟基聚丁二烯。采用凝胶渗透色谱(GPC)和1H-NMR方法表征了聚合物相对分子质量及其分布、支化度、平均官能度和主链微观结构。研究结果表明,三臂星形端羟基聚丁二烯的相对分子质量分布指数≤1.1,平均官能度和支化度均接近3。     

四羟基聚丁二烯的合成及其改性端羟基聚丁二烯液体橡胶的力学性能

采用自制的烷基锂引发剂,以环己烷为溶剂、四氢呋喃为结构调节剂、四氯硅烷为偶联剂合成了具有四羟基的端羟基聚丁二烯(HTPB)液体橡胶,通过凝胶渗透色谱仪、核磁共振仪等对其进行了表征.结果表明,四羟基HTPB的多分散指数小于1.1,平均官能度接近4,微观结构可调.用该四羟基HTPB改性现有商品HTPB可提高其拉伸强度,但扯...     

负离子聚合法合成端羟基聚丁二烯与自由基法端羟基聚丁二烯的性能对比

以硅烷保护羟基的烷基锂为引发剂,采用负离子聚合法合成了端羟基聚丁二烯(HTPB),通过核磁共振氢谱、傅里叶变换红外光谱、凝胶渗透色谱和差示扫描量热法表征了HTPB的微观结构、分子量分布、官能度及玻璃化转变温度(Tg),研究了HTPB胶片的拉伸性能,并与自由基法HTPB进行了对比。结果表明,负离子法HTPB的1,4-结构摩尔分数约为90%,比自由基法HTPB高约12%,分子量分布小于1.1,低于自由基法HTPB,平均官能度比自由基法HTPB更接近理想值2,Tg为-88.3℃,较自由基法HTPB低9.7℃;负离子法HTPB胶片的拉伸强度与自由基法HTPB胶片相近,但扯断伸长率比自由基法HTPB胶片提高约74%。     

端羟基聚丁二烯官能度分布的测定

本工作采用高压液相色谱法测定端羟基聚丁二烯(HTPB)的官能度分布.将3,5-二硝基苯甲酰氯(DNBC)在一定条件下,进行衍生化反应.衍生化后的 HTPB 经高压液相色谱仪的紫外(UV)和方差(RI)双检测器进行检测。所得色谱图经数据处理,并分区统计组合,得到 HTPB的羟基官能团随分子量的分布,同时得到相应的数均分子量、重均分子量、分子量分散指数、数均官能度、重均官能度及官能度分散指数.     

端羟基聚丁二烯官能度及分布的测定

用凝胶渗透色谱法（GPC）测定端羟基聚丁二烯（HTPB）官能度分布。将HTPB用3,5-二硝基苯甲酰氯在一定条件下进行衍生化反应,衍生化后的HTPB经GPC的示差／紫外（RI／UV）双检测器进行检测,所得的色谱图经数据处理,得到HTPB的官能度及其分布。     

端羟基聚丁二烯主链改性研究进展

简要介绍了目前合成端羟基聚丁二烯(HTPB)的自由基聚合法和阴离子聚合法,并简述这2种合成方法的优缺点。重点叙述了HTPB主链改性研究进展,通过对 HTPB 主链中的双键进行改性或利用嵌段共聚技术,可向HTPB主链上引入新的特征基团或某些功能性链段,从而赋予改性后的HTPB不同的性能,拓宽其应用领域。     

丙烯酸树脂及其涂料

低VOC含量并提高了贮存稳定性的涂料组合物用水性丙烯酸乳液 一种水性涂料组合物含丙烯酸酯型基料{含1％～10％至少一种羟基官能共聚单体,其通式A-[B],-C,其中,A是可聚合基团,B是间隔基团,C是羟基官能基团,n是0或1}、至少一种颜料、〈3％的抗冻剂和其它的添加剂和填料。     

High performance HTLNR/epoxy blend—Phase morphology and thermo-mechanical properties

An attempt was made to toughen diglycidyl ether of bisphenol A (DGEBA) type epoxy resin with liquid natural rubber possessing hydroxyl functionality (HTLNR). Epon 250 epoxy monomer is cured using nadic methyl anhydride as hardener in presence of N, N dimethyl benzyl amine as accelerator. HTLNR of different concentrations up to 20 wt % is used as modifier for epoxy resin. The addition HTLNR to an anhydride hardener/epoxy monomer mixture has given rise to the formation of phase-separated structure, consisting of small spherical liquid natural rubber particles bonded to the surrounding epoxy matrix. The particle size increased with increase in rubber content. The viscoelastic properties of the blends were analyzed using dynamic mechanical thermal analysis. The T_g corresponding to epoxy rich phase was evident from the dynamic mechanical spectrum, while the T_g of the rubber phase was overlapped by the β relaxation of epoxy phase. Glass transition of the epoxy phase decreased linearly as a function of the amount of rubber. The mechanical properties such as impact and fracture toughness were also carefully examined. The impact and fracture toughness increase with HTLNR content. A threefold increase in impact strength was observed with 15 wt % HTLNR/epoxy blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Functionality distribution and crosslink density of hydroxyl-terminated polybutadiene

A novel approach is proposed for estimating the average molecular weight between crosslinks (M?_c) from the functionality distribution of hydroxyl-terminated polybutadiene ( HTPB ). The functionality distribution of four free-radically polymerised HTPB prepolymers of varying hydroxyl content and molecular weight was determined by a combination of preparative and analytical gel permeation chromatography. The gumstock properties of the samples cured with stoichiometric amounts of toluene diisocyanate were not correlatable with the relative amounts of difunctional chain extender and multifunctional crosslinker present, unlike the case of HTPB with similar hydroxyl content and molecular weight. However, the mechanical properties and sol content could be correlated with the average molecular weight between crosslink sites, M?_c, of the cured polymer. The M?_c values derived by our method compare well with those of classical methods, and the observed differences are attributed to segmental entanglement. These M?_c values give consistently good correlation with all the gumstock properties, confirming the validity of our approach and the soundness of the techniques developed for the determination of the functionality distribution of HTPB .     

Effect of molecular weight and content of PDMS on morphology and properties of silicone‐modified epoxy resin

To achieve a stable blend of a bisphenol A type epoxy resin and poly(dimethylsiloxane) (PDMS), reaction between hydroxyl (OH) groups of the epoxy and silanol groups of hydroxyl‐terminated(HT) PDMS has been investigated. The chemical structures of the HTPDMS‐modified epoxies were characterized by Fourier transform infrared (FTIR) and ¹H‐ and ¹³C‐NMR spectroscopy. To allow further understanding of the influence of viscosity and content of HTPDMS on the blend morphology, four different viscosities of HTPDMS were used in three content levels. The morphologies of modified epoxy resins were observed with optical microscopy. The modified epoxies were cured with a cycloaliphatic polyamine. The morphologies of modified epoxies were investigated by using scanning electron microscopy (SEM)/energy dispersive X‐ray (EDX) technique. The cured films showed droplet in matrix morphology with different mean droplets size which was influenced by the viscosity and the content of the incorporated HTPDMS. To illustrate the effect of the morphologies of the cured samples on mechanical properties, tensile strength tests were performed. The introduction of HTPDMS into the epoxy altered the tensile behavior according to its viscosity and content. Surface properties of the cured films were evaluated by sessile drop method. The results clearly indicate that the hydrophilic surface of the epoxy turns to a hydrophobic one due to the modification with HTPDMS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

低黏度环氧树脂高温固化的性能影响

研究了风电叶片用低黏度环氧树脂在70℃、90℃和110℃固化温度下固化物的性能变化。气相色谱–质谱分析低黏度环氧树脂主要由双酚A环氧树脂和1,4–丁二醇二缩水甘油醚组成,固化剂为多元胺的成分,再通过红外光谱对70℃、90℃和110℃3组样件进行分析,结果显示,随着固化温度升高,固化物中起到体型网络交联的醚键的含量呈下降趋势,同时羰基和亚甲基含量增加,这些都说明在此固化温度区间内,固化温度升高,高分子的交联度呈下降趋势。对环氧浇铸体和玻璃钢样件的力学性能测试显示,从70℃到110℃固化温度升高样件的各项力学性能呈下降趋势。     

Novel phosphorus‐containing hardeners with tailored chemical structures for epoxy resins: Synthesis and cured resin properties

A comparative evaluation of systematically tailored chemical structures of various phosphorus‐containing aminic hardeners for epoxy resins was carried out. In particular, the effect of the oxidation state of the phosphorus in the hardener molecule on the curing behavior, the mechanical, thermomechanical, and hot‐wet properties of a cured bifunctional bisphenol‐A based thermoset is discussed. Particular attention is paid to the comparative pyrolysis of neat cured epoxy resins containing phosphine oxide, phosphinate, phosphonate, and phosphate (with a phosphorus content of about 2.6 wt %) and of the fire behavior of their corresponding carbon fiber‐reinforced composites. Comparatively faster curing thermosetting system with an enhanced flame retardancy and adequate processing behavior can be formulated by taking advantage of the higher reactivity of the phosphorus‐modified hardeners. For example, a combination of the high reactivity and of induced secondary crosslinking reactions leads to a comparatively high T_g when curing the epoxy using a substoichiometric amount of the phosphinate‐based hardener. The overall mechanical performance of the materials cured with the phosphorus‐containing hardeners is comparable to that of a 4,4′‐DDS‐cured reference system. While the various phosphorus‐containing hardeners in general provide the epoxy‐based matrix with enhanced flame retardancy properties, it is the flame inhibition in the gas phase especially that determines the improvement in fire retardancy of carbon fiber‐reinforced composites. In summary, the present study provides an important contribution towards developing a better understanding of the potential use of such phosphorus‐containing compounds to provide the composite matrix with sufficient flame retardancy while simultaneously maintaining its overall mechanical performance on a suitable level. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and Application of a New Curing Agent for Epoxy Resin

A new curing agent based on palmitoleic acid methyl ester modified amine (PAMEA) for epoxy resin was synthesized and characterized. Diglycidyl ether of bisphenol A (DGEBA) epoxy resins cured with different content of PAMEA along with diethylenetriamine (DETA) were prepared. The mechanical properties, dynamic mechanical properties, thermal properties, and morphology were investigated. The results indicated that the PAMEA curing agent can improve the impact strength of the cured epoxy resins considerably in comparison with the DETA curing agent, while the modulus and strength of the cured resin can also be improved slightly. When the PAMEA/epoxy resin weight ratio is 30/100, the comprehensive mechanical properties of the cured epoxy resin are optimal; at the same time, the crosslinking density and glass transition temperature of the cured epoxy resin are maximal.     

Interphase Reaction of Isocyanates with Epoxy Resins Containing Functional Groups of Different Reactivity

Interphase reactions between cured epoxy resins and isocyanates are investigated. The epoxy resins contain secondary hydroxyl groups as reactive groups only or secondary hydroxyl plus amine. The isocyanate diffuses into the epoxy resin forming an interphase with a thickness of some micrometers. Depending on the functional groups available in the epoxy resin, urethane and urea groups are formed in the interphase. If a monofunctional isocyanate is used, no difference between both kinds of epoxy resin could be detected regarding the formation of urethane. If the epoxy resins react with bifunctional isocyanates a crosslinked interphase is formed. Due to the higher reactivity between amine and isocyanate compared to hydroxyl and isocyanate, the urea is formed first. The resulting cross‐links restrict the further diffusion of isocyanate into the epoxy resin. The consequence is a lower urethane content in the interphase and a thinner interphase compared to the epoxy resin containing hydroxyl only. If a prepolymer with isocyanate end groups is used as isocyanate the formation of the interphase is slower compared to the low molecular weight isocyanate. This is due to the reduced mobility of the prepolymer.     

Effect of curing agent on the properties of mineral silica filled epoxy composites

Polymer materials have been used extensively as the organic substrate materials in electronic packaging industry. The mechanical, thermal, and morphology properties of the alternative low cost composites have been investigated in this article. One of the materials is epoxy resin cured by aliphatic amine, and the other is cured by aromatic amine. It was found that the physical, mechanical, and thermal properties of epoxy resins are strongly depended on the curing agents. Morphology changed differently in these two epoxy‐curing systems. Crosslink density obtained from rubbery modulus in dynamic flexural storage modulus showed aromatic amine functionality group that gives higher crosslink density and increased in physical, mechanical, and thermal properties. POLYM. COMPOS., 29:27–36, 2008. © 2007 Society of Plastics Engineers     

Bio-based shape memory epoxy resin synthesized from rosin acid

A bio-based shape memory epoxy resin (DGEAPA) was synthesized from rosin to achieve the sustainability of shape memory epoxy resin, and its chemical structure was determined by FTIR and ¹H NMR. For comparison, a petroleum-based epoxy, diglycidyl ester of terephthalic acid (DGT) having one benzene ring, was also synthesized. The properties, including thermal and mechanical properties, as well as shape memory properties of the epoxy resins cured with poly(propylene glycol)-bis (2-aminopropyl ether) (D230), were studied by differential scanning calorimeter, dynamic mechanical analysis, thermogravimetric analysis, tensile test, and U-type shape memory test. The effect of the stoichiometric ratio n_DGEAPA/n_DGT on the properties was studied as well. The thermal and mechanical properties, including thermal stability, glass transition temperature, tensile strength, and modulus of the cured epoxy systems, were found to be increased with DGEAPA incremental content, and the cured neat rosin-based epoxy system exhibited the highest properties. Both the cured rosin-based epoxy and the cured DGEAPA showed significant shape memory performance. Meanwhile, the rosin ring structure made the cured rosin-based epoxy systems display excellent shape recovery fixity, while small lower shape recovery and shape recovery rate relative to the cured neat DGT system. Therefore, the rosin-based epoxy resin has a great potential in the shape memory material applications.