纤维热熔法缠绕用氰酸酯树脂基体研究

用DSC和VHR方法研究催化剂二月桂酸二丁基锡（DBTDL）对双酚A氰酸酯及环氧改性氰酸酯体系反应的影响。根据纤维热熔缠绕要求，研制出工艺适用的改性氰酸酯树脂基体。热熔工作温度100℃。碳纤维增强复合材料层剪强度测试结果表明，基体适用于纤维热熔法缠绕复合材料。     

一种改性氰酸酯树脂性能的研究

采用自制改性剂改性双酚A型氰酸酯树脂,制备了一种适合常规180℃固化工艺的改性氰酸酯树脂,可用于热熔法制备预浸料。对改性氰酸酯树脂的工艺性、力学性能、耐热性能和微观形貌等进行了研究,结果表明制备的树脂具有良好的工艺性,无需进行高温后固化处理即可得到力学性能和耐热性能较为优异的固化物,可广泛用于航空、航天、电子等领域高性能复合材料的制备。     

酚酞基聚芳醚砜改性双酚A型氰酸酯预聚体的制备及性能研究

将酚酞基聚芳醚砜（PES-C）与双酚A型氰酸酯（BCE）共混,在一定的条件下使氰酸酯预聚,得到酚酞基聚芳醚砜与双酚A型氰酸酯共混改性预聚体系,借助FT-IR和DSC确定了固化工艺,并用扫描电镜（SEM）对预聚体及其固化物进行表征,测试了改性体系的冲击强度和对铝合金的粘接强度。结果表明,PES-C对CE起到了明显的增韧改性的作用,改性体系固化物具有较好的介电性能,在常温到230℃范围内粘接剪切性能优异（均大于20MPa）。该改性体系可用作一种新型耐高温结构胶黏剂的主体树脂。     

预浸料用中温固化环氧树脂体系的制备

中温固化环氧树脂基复合材料具有成型温度适中、成型周期短、韧性高等优点,是复合材料应用领域的研究热点。通过筛选不同牌号环氧树脂,调节配方中树脂、固化剂、增韧剂以及增塑剂的含量,研制出一种中温固化并适用于热熔法制备预浸料的环氧树脂体系。考察了树脂体系的胶膜状态、黏度-温度曲线、DSC曲线特性,最终选定的树脂配方为双酚A型环氧树脂CYD-011、双酚A环氧树脂E-44与邻甲酚醛环氧树脂CYDCN-205的质量比为3∶5∶2。对由其制备的预浸料和复合材料的力学性能进行了测试,结果表明,由该树脂体系制备的预浸料综合性能优异,具有强度高、韧性好和适用期长等特点,各项指标均很好地满足了厂家对材料的要求。     

中低温固化预浸料用环氧树脂基体的制备与性能研究

以邻甲酚酚醛环氧和双酚A环氧为主体树脂,采用核壳增韧剂进行改性,配合潜伏性固化促进剂,制备了一种可中低温固化的环氧预浸料基体树脂.通过对树脂力学性能、耐热性能、微观形貌和固化特征的分析,确定了树脂体系的组成和固化工艺,同时研究了该树脂制备的T700碳纤维预浸料固化后的力学性能.研究表明,环氧树脂基体浇铸体拉伸强度75M...     

一种改性氰酸酯预聚体的合成和性能研究

将聚砜树脂(PSF)和双酚A型氰酸酯树脂(BCE)在一定条件下进行预聚反应,通过红外光谱(FT-IR)、差热扫描(DSC)、扫描电镜(SEM)对所得到的预聚体树脂及其固化后产物进行分析和表征。结果表明改性后的氰酸酯预聚体具有优异的力学性能和良好的介电性能。     

直升机柔性杆用环氧树脂预浸料的研制

研制了用于制备直升机主传力系统中复合材料柔性杆件的改性环氧树脂基体及其RC10．800连续玻璃纤维预浸料。探讨了树脂基体组成、连续玻璃纤维窄带预浸工艺参数等变量对预浸料和复合材料性能的影响。选用的促进剂满足直升机柔性杆的技术要求和热熔工艺要求，满足此生产工艺要求。     

一种双酚A型氰酸酯树脂流变特性及其改性研究

本文采用平板法研究了一种双酚A型氰酸酯树脂的流变特性,通过恒温预固化的方法对其进行改性,并借助红外光谱、差示扫描量热法(DSC)和凝胶渗透色谱法(GPC)等手段分析了预固化对氰酸酯树脂化学结构的影响.在此基础上,针对S-2玻璃纤维/氰酸酯复合材料层板,采用热压机工艺考察了加压时机和预固化对层板成型质量的影响.研究结果表明,该氰酸酯树脂反应活性低且流动性高,热压工艺中树脂流动不易控制;预固化可使氰酸酯树脂发生一定程度的自聚反应,从而降低其流动性,可明显改善氰酸酯树脂的工艺性,提高了层板的成型质量.     

氰酸酯树脂结晶性研究

对氰酸酯树脂结晶性进行了研究。通过折光指数测试监控氰酸酯树脂预聚反应过程,采用凝胶色谱研究了预聚前后树脂的结构变化,通过差热扫描分析了氰酸酯体系结晶物的熔融相变。结果表明,随着预聚时间的延长,折光指数不断增加,氰酸酯树脂出现大量多聚体,结晶时间推迟;双酚E型单体的引入可降低氰酸酯树脂的熔点、增加熔限,阻止氰酸酯结晶过程。在双酚A型氰酸酯树脂中加入25%双酚E型单体,并在130℃下预聚55 m in,折光指数达1.5842时,共混体系可在室温下长时间保持液态,未出现结晶。     

两种预浸工艺对玻璃布预浸料性能的影响

着重研究了用溶液法和热熔胶膜法工艺所制备的5231/823玻璃布预浸料的物理性能、工艺性能、力学性能和滚筒剥离性能,旨在探讨不同预浸工艺对预浸料及其复合材料性能的影响,试验结果表明:这2种工艺所制的5231/823预浸料的工艺性能和剥离性能相当,但在预浸料树脂含量控制精度方面,热熔法工艺高于溶液法工艺;在预浸料挥发分方面,热熔法工艺的较低,一般低于0.8%。在复合材料常规力学性能方面,一般前者高于后者。     

Low‐temperature cure high‐performance cyanate ester resins/microencapsulated catalyst systems

The encapsulated catalyst can be released under stimulation conditions to control the polymerization reaction. In this study, poly(urea‐formaldehyde) (PUF) microcapsules (MCs) filled with dibutyltin dilaurate (DBTDL) catalyst (PUF/DBTDL MCs) were applied to bisphenol A dicyanate ester (BADCy) resins to develop a novel low temperature cure high performance BADCy/MCs systems. The effect of PUF/DBTDL MCs on the reactivity of BADCy was investigated. The mechanical property, the thermal property, the water uptake, and the dielectric property of cured BADCy/MCs resin systems were discussed in detail. Results indicate that roughly varying the content of the encapsulated DBTDL can easily and safely adjust the polymerization temperature. The BADCy systems with proper content of MCs cured at low temperature show excellent mechanical property, good thermal property, low water uptake, and low dielectric property. When the content of MCs is 0.125 wt%, the cured BADCy/MCs system has the optimal integrated properties owing to the formation of more uniform crosslinked structure and high conversion of cyanate ester (? OCN) groups resulting from the slow release of DBTDL catalyst through the wall shell under heating condition. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Relationship between viscoelastic properties and gelation in the epoxy/phenol‐novolac blend system with N‐benzylpyrazinium salt as a latent thermal catalyst

A study of viscoelastic properties and gelation in epoxy/phenol‐novolac blend system initiated with 1 wt % of N‐benzylpyrazinium hexafluoroantimonate (BPH) as a latent cationic thermal initiator was performed by analysis of rheological properties using a rheometer. Latent behavior was investigated by measuring the conversion as a function of curing temperature using traditional curing agents, such as ethylene diamine (EDA) and nadic methyl anhydride (NMA) in comparison to BPH. In the relationship between viscoelastic properties and gelation of epoxy/phenol‐novolac blend system, the time of modulus crossover was dependent on high frequency and cure temperature. The activation energy (E_c) for crosslinking from rheometric analysis increased within the composition range of 20–40 wt % phenol‐novolac resin. The 40 wt % phenol‐novolac (N40) to epoxy resin showed the highest value in the blend system, due to the three‐dimensional crosslinking that can take place between hydroxyl groups within the phenol resin or epoxides within the epoxy resin involving polyaddition of the initiator with BPH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2299–2308, 2001     

Properties and origins of high‐performance poly(phenylene oxide)/cyanate ester resins for high‐frequency copper‐clad laminates

A high‐performance matrix is the key base for the fabrication of high‐frequency copper‐clad laminates. A high‐performance resin system based on commercial poly(phenylene oxide) (PPO) and 2,2′‐bis(4‐cyanatophenyl) isopropylidene (BADCy), coded as PPO‐n/BADCy (where n is the weight parts of PPO per 100 weight parts of BADCy), was developed. The effect of PPO on the key properties, including the dielectric and thermal properties, water resistance, and toughness, of the cured resins was investigated extensively. The results show that PPO not only catalyzed the curing reaction of BADCy but also reacted with BADCy to form a single‐phase structure. Furthermore, compared with the cured BADCy resin with 1 phr epoxy resin as a catalyst, the cured PPO‐n/BADCy resins had significantly increased impact strengths and decreased dielectric constants, loss, and water resistance. The reasons behind these desirable improvements are discussed from the view of structure–property relationships. These results suggest that the PPO‐n/BADCy system has great potential to be used as a matrix for high‐frequency copper‐clad laminates or other advanced composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical characterization of carbon fiber reinforced phenolic resol and epoxy condensate plastic

A matrix resin for carbon fiber reinforced composite was developed that consisted of resol type phenolic and difunctional epoxy resin (PR-EP) condensate or adduct. Carbon fiber reinforced composite with fiber volume fraction of 0.6 was prepared with PR-EP matrix containing 0, 50, 100, 150, and 175 parts of epoxy resin per hundred parts of phenolic resin (php), especially a synthesized resol type. One-shot and prepreg techniques have been adopted and the study of loss of volatiles has indicated the superiority in terms of favorable processability of prepreg technique over the other. FTIR spectroscopic analysis confirmed the PR-EP adduct formation at the prepreg preparation stage. The improvement in properties such as tensile strength and elongation at break was observed in resin matrices with epoxy and phenolic resin; however, the flexural strength and modulus remained more or less unaltered. The prepreg technique of composite preparation has resulted in substantial improvement in mechanical properties and the same was attributed to the formation of PR-EP adduct and low volatiles during cure. Composites of carbon fiber reinforced PR-EP matrix developed here are likely to meet the requirement of aerospace structures in view of the realization of a wide spectrum of properties.     

Epoxy‐modified cyanate ester resin and its high‐modulus carbon‐fiber composites

Epoxy E51‐modified bisphenol A dicyanate (BADCy) and its high‐modulus carbon fiber (M40) reinforced composites were prepared in this research. The carbon‐fiber composites were prepared by autoclave molding. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy of BADCy‐E51 blend systems showed that polycyclotrimerization of BADCy primarily took place at low temperature. Epoxy group reacted with triazine ring group and produced oxazolidinone at high temperature. The data of mechanical properties, water absorption, and heat deflection temperature (HDT) of cured castings showed that the matrix system containing 95 wt% BADCy and 5 wt% E51 had optimum characteristics. Scanning electron microscopy (SEM) analysis of M40 fiber and the fracture surfaces of M40/BADCy‐E51 composite displayed that the adhesion between M40 fiber and BADCy was good though the surface of M40 was inert. The high retention of mechanical properties of M40/BADCy‐E51 composite after long‐term exposure to environmental conditions indicated that the M40/BADCy composite was suitable for space applications. POLYM. COMPOS., 27:402–409, 2006. © 2006 Society of Plastics Engineers     

中温热熔预浸料用环氧树脂及其固化体系的研究进展

本文综述了中温热熔预浸料用环氧树脂体系,包括国内外基体树脂及固化体系的发展现状;分析了粘度对基体树脂的影响规律、固化剂和促进剂的匹配、催化剂的选择等;重点介绍了脲类衍生物和咪唑两类固化促进体系的进展;表明环氧树脂热熔预浸料研制的技术关键是选择合理的树脂体系组合,有较长潜伏期的固化剂和促进剂的匹配及合适的催化剂。     

Epoxy-based composite adhesives with improved lap shear strengths at high temperatures for steel-steel bonded joints

High-performance room temperature-cure epoxy structural adhesives utilizing simplified formulation are developed. The developed structural adhesive consists of diglycidyl ether of bisphenol A (DGEBA) and novolac epoxy blend as a base resin, micrometer-sized silica particles as a reinforcing filler, and triethylenetetramine as a curing agent. The developed ambient temperature-cure epoxy structural adhesive with optimized formulation exhibits outstanding properties including high glass transition temperature of 95°C, high thermal stability with degradation temperature at 5% weight loss of 364°C, exceptionally high rubbery plateau modulus of 320 MPa, good flame-retardant characteristics with limiting oxygen index of 40, and high single lap shear strength for single lap steel-steel bonded joint of 548 MPa at the temperature of 80°C. The silica-filled DGEBA/novolac epoxy composite adhesive is a potential candidate for applying as a structural adhesive for construction with long-term durability.     

Effect of the epoxy molecular weight on the properties of a cyanate ester/epoxy resin system

Bisphenol A dicyanate (BADCy) was modified by diglycidyl ether of bisphenol A epoxy resins with different molecular weights [E20 (weight‐average molecular weight = 1000) and E51 (weight‐average molecular weight = 400)] to investigate the effects of the epoxy molecular weight on the properties of the modified systems. The reactions were monitored with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy, and the results showed that more pentacyclic oxazolidinone rings were formed in BADCy/E51 than in BADCy/E20 with the same epoxy resin weight content. DSC showed that BADCy/E20 had a lower curing temperature than BADCy/E51 because of the higher concentration of hydroxyl groups (? OH) in E20. Thermal, moisture absorption, and mechanical testing showed that E51‐modified BADCy performed better because of its lower molecular weight. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1744–1750, 2006     

Effect of Phenol/Formaldehyde Stoichiometry on the Modification of Epoxy Resin Using Epoxidized Novolacs

ABSTRACT

Unmodified epoxy resins based on bisphenol A exhibit brittleness and low elongation after cure. This article reports the results of a study for improving the properties of epoxy resin by blending with suitable thermosets. Hybrid polymer networks of diglycidyl ether of bisphenol A (DGEBA) resin with epoxidized phenolic novolac resins (EPN) containing phenol and formaldehyde in different stoichiometric ratios were prepared by physical blending. The modified epoxy resins were found to exhibit improved mechanical and thermal properties compared to the neat resin. DGEBA resins containing 2.5 to 20 wt% of epoxidized novolac resins (EPN) prepared in various stoichiometric ratios (1:0.6, 1:0.7, 1:08, and 1:0.9) between phenol and formaldehyde were cured using a room temperature amine hardener. The cured samples were tested for mechanical properties such as tensile strength, modulus, elongation, and energy absorption at break. All the EPNs are seen to improve tensile strength, elongation, and energy absorption at break of the resin. The blend of DGEBA with 10 wt% of EPN-3 (1:0.8) exhibits maximum improvement in strength, elongation, and energy absorption. EPN loading above 10 wt% is found to lower these properties in a manner similar to the behavior of any filler material. The property profiles of epoxy–EPN blends imply a toughening action by epoxidized novolac resins and the extent of modification is found to depend on the molar ratio between phenol and formaldehyde in the novolac.     

Blends of cardanol-based epoxidized novolac resin and CTBN for application in surface coating: a study on thermal,mechanical, chemical,and morphological characteristics

Blend samples of cardanol-based epoxidized novolac resin and different weight percentages of carboxyl-terminated butadiene acrylonitrile (CTBN) were developed and cured with stoichiometric amounts of aliphatic amine. The formation of various products during the curing of blend samples has been studied by Fourier-transform infrared spectroscopy. The dynamic differential scanning calorimeter scans showed that the pure epoxies and their blend samples with CTBN cured in the temperature range of 100–150°C. The blend sample containing 15 wt% CTBN showed the least cure time (at 120°C) among all other blend samples. Upon evaluation, it was found that blend samples exhibit better properties compared to pure epoxy resin in terms of increase in impact strength and elongation-at-break of the casting and gloss, scratch hardness, adhesion, and flexibility of the film. The improvement in these properties indicates that the rubber modified resin would be more durable than the epoxy based on cardanol. Chemical and morphological properties of the formulated resins were also determined. The thermal stability of the blend samples containing 15 wt% CTBN in epoxy resin was the highest among all other prepared systems. The blend morphology, studied by scanning electron microscope, showed the presence of precipitated discrete rubber particles, which dispersed throughout the epoxy matrix—i.e., they revealed the presence of two-phase morphological features.