热致性液晶聚合物各类对环氧树脂性能的影响研究

利用自行合成的多种热致性高分子液晶聚合物对CYD－128环氧树脂进行共混改性,用FTIR方法研究了液晶聚合物对环氧树脂固化反应程度的影响,用DSC、TGA研究了液晶聚合物对环氧树脂固化物Tg和热失重温度的影响,测试了共混物的力学性能,并用扫描电镜观察了共混物冲击断面的形貌。结果表明：端基含有活性反应基团的液晶聚合物可以提高固化反应程度、提高固化物的韧性和强度,同时还使固化物的Tg和热失重温度提高,SEM观察表明,加入液晶聚合物的材料断裂面面积增大,逐渐出现韧性断裂的特征。     

热致性液晶固化剂增韧环氧树脂的研究

合成了一种环氧树脂的热致性液晶固化剂,利用红外光谱、偏光显微镜（POM）、差热分析仪（DSC）、元素分析等手段确认其结构。将此液晶固化剂加入环氧树脂／二氨基二苯砜（DDS）固化体系中,测试了固化物的力学性能,并用热重量分析仪（TG）、DSC测试了固化物的玻璃化转变（Tg)和热失重温度（Td),用偏光显微镜（POM）以不同配比的环氧树脂／液晶固化剂体系的固化样品形貌进行观察。结果表明：加入不到3％的液晶固化剂,可以使环氧固化物的拉伸强度提高50％,冲击强度提高一倍,Tg和Td明显提高,偏光显微镜照片表明液晶固化剂的加入使固体体系出现了相分离。     

液晶相对分子质量对热致性液晶／环氧树脂共混物性能的影响

采用自行合成的各种相对分子质量的反应型液晶聚合物（LCPU）对环氧树脂CYD-128/4，4′-二氨基二苯砜（DDS）固化体系进行改性，固定LCPU用量为5%，对各种改性体系的冲击强度，拉伸强度，弯曲强度，弹性模量，玻璃化转变温度（Tg），热失重温度（Td）、电性能，吸水性能与LCPU相对分子质量（n）的关系进行了研究，结果表明，LCPU的相对分子质量对固化物的力学性能和热性能影响较大，对其电性能和吸水性能的影响较小，当n=6时LCPU对环氧树脂的综合改性效果最好。     

一种侧链型液晶聚合物与环氧树脂共混改性研究

设计并合成了一种侧链型液晶聚合物（SLCP），用红外光谱（FTIR），差示扫描量热分析（DSC）和偏光显微镜（POM）对聚合物结构和液晶性能进行表征，探讨其对环氧树脂共混物力学性能的影响，并分析共混物的微相分离结构，结果表明，用T31作固化剂时SLCP对环氧树脂有较好的增强增韧效果，在强度和玻璃化温度不降低的情况下断裂伸长度比未改性固化物最大提高2．6倍，但用三乙醇胺作固化剂时SLCP对环氧树脂改性效果不明显。     

苄基二甲胺／双氰胺／环氧树脂体系固化物性能的研究

本文用DSC、介电和动态力学方法研究了组成对苄基二甲胺催化的双氰胺固化环氧树脂体系固化物的玻璃化转变温度的影响。结果表明,在相同的固化条件下,胺与环氧的当量配比等于O.6时,固化物获得较高的Tg值,体系中引入酚醛型环氧树脂能够使固化物的Tg值提高。应用热失重和差热分析测试技术对环氧固化体系的热稳定性也进行了探讨。     

环氧多聚磷酸铵的合成及其对环氧树脂固化物性能的影响

将环氧树脂和多聚磷酸直接反应后用氨水中和,制得了含磷18.5%且与环氧树脂相容性较好的新型环氧多聚磷酸铵(EPPA)阻燃剂。用极限氧指数、冲击强度、硬度、热失重等测试方法研究了EPPA对环氧树脂二乙烯三胺固化物阻燃性以及其它各种性能的影响。实验结果表明该阻燃剂对环氧树脂固化物有较好的阻燃作用,适量添加EPPA可大幅提高固化物的韧性,并且对固化物的硬度以及热稳定性影响不大。     

苯酐固化邻甲酚醛环氧的热性能与热分解动力学

研究了邻甲酚醛环氧树脂(o CFER)与邻苯二甲酸酐固化物的热分解动力学,用动态力学谱仪测定了玻璃化温度(Tg)。讨论了固化剂用量、固化时间等因素对玻璃化转变温度(Tg)的影响。结果表明,固化体系的玻璃化温度随反应程度的增加而升高,当达到一定程度后,趋于一定值。利用热重分析仪(TGA)研究了完全固化产物的热分解动力学,说明热分解反应分2步进行。     

热致型液晶增韧环氧树脂的研究进展

利用热致型液晶化合物对环氧树脂进行增韧改性,固化体系既融合了液晶的有序性又保留了环氧树脂网络交联的特点,其韧性、冲击强度大幅度提高,而不降低耐热性,这是环氧树脂的传统增韧方法所无法比拟的,是实现环氧树脂高性能化的重要途径之一。热致型液晶高分子(TLCP)增韧环氧树脂可以归纳为两类:液晶环氧树脂(LCEP)增韧和其他聚合物液晶共混增韧。概述了LCEP增韧的方法和增韧机理,TLCP共混增韧的方法和增韧机理,综述了热致型液晶增韧环氧树脂的研究进展,并对其今后研究作了展望。     

氰酸酯/联苯型环氧树脂共混体系的DSC研究

采用非等温差示扫描量热法对氰酸酯/联苯型环氧树脂共混体系的固化反应动力学、特征温度、转化率和玻璃化转变温度(Tg)进行了研究。共混体系的表观活化能随着联苯型环氧树脂量的增加而降低,质量比为80/20树脂体系的表观活化能为88.6k J·mol~(-1),高于80/20氰酸酯/双酚A型环氧树脂体系的表观活化能。当固化程度接近完全时,80/20共混体系的Tg为249.2℃,比80/20氰酸酯/双酚A型环氧树脂体系的Tg值高出24.3℃。催化剂的加入能使共混体系的表观活化能下降约20k J·mol~(-1),反应特征温度降低约100℃,同时对Tg影响较小。     

环氧树脂聚酰胺网络体系性能研究

用红外光谱法表征了4种聚酰胺固化剂与环氧树脂按等当量配比,在一定条件下的固化反应过程。DSC法测定了其固化反应活性。桐马聚酰胺/环氧树脂固化体系较聚酰胺650/环氧树脂固化体系的固化活性大大提高,同时测定了该固化产物的热失重(TG)及玻璃化温度(Tg),对该固化物的热稳定性进行了评价,还测定了不同固化时间的剪切强度以研究其动态力学性能,从浇铸体的冲击强度方面比较其韧性。综合比较分析了聚酰胺固化剂与环氧树脂固化体系的力学性能、耐热性、电绝缘性等。结果表明:桐马聚酰胺Ⅲ型固化剂具有黏度低、粘接强度大、耐热性好、力学性能优等优点。     

A study on the properties of epoxy resin toughened by a liquid crystal‐type oligomer

A series of novel reactive toughening agents (LCEU_PPG) containing both a flexible spacer and rigid liquid crystalline unit were synthesized to modify the bisphenol epoxy resin/dicyandiamide curing system. The curing reactivity, apparent activation energy, curing mechanism, dynamic mechanical behavior, and impact strength of the modified system were systematically studied. Compared with the unmodified system, the results indicate that LCEU_PPG have greatly accelerated the curing reaction between epoxy resin and dicyandiamide, reduced the apparent activation energy of the curing reaction, enhanced the impact strength 3–7 times, and maintained high dynamic modulus and good thermal properties. In addition, SEM observation of the fracture surfaces showed a two‐phase microstructure in the modified systems. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 177–184, 1999     

Modification of an o‐cresol formaldehyde epoxy resin by the thermotropic liquid crystalline polymer

Two novel liquid crystalline polymers, polydiethyleneglycol bis(4‐hydroxybenzoate) terephthaloyl and block copolymer (PDBH), were synthesized by condensation reaction. The blends of the two liquid crystalline polymers and o‐cresol formaldehyde epoxy resin were prepared by linear phenol‐formaldehyde resin as curing reagent. Both mechanical and thermal properties of the blends containing liquid crystalline polymer were improved to a certain extent. By adding 5 wt % PDBH, the impact strength, bending strength, and the glass transition temperature were enhanced by 128%, 23.84%, and 28°C, respectively, compared with the unmodified version. The results of curing kinetics showed that the curing reaction active energy of the modified system by PDBH decreased from 79.70 to 70.26 kJ/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1626–1631, 2005     

Enhancement in the thermal and dynamic mechanical properties of high performance liquid crystalline epoxy composites through uniaxial orientation of mesogenic on carbon fiber

In this work, a high performance liquid crystalline epoxy composite was prepared and the effect of the alignment of LCE with long lateral substituent on the carbon fiber surface curing at low temperature on fracture toughness, dynamic mechanical, and thermal properties of liquid crystalline epoxy with lateral substituent (LCE6) was investigated by polarized optical microscopy (POM), wide angle X‐ray diffraction measurements (WAXS), dynamic mechanical analysis (DMA), thermogravimetric (TGA), and scanning electron microscopy (SEM). Curing degree of the composite was observed by FTIR. The experimental results indicate that the fracture toughness, glass transition temperature (T_g), thermal stability, degradation kinetics are associated with the alignment of LCE6 along long axis of carbon fiber. The alignment of LCE6 on carbon fiber surface can increase mesogen network density, which leads to higher fracture toughness, higher thermal stability, increase of the activation energies and higher T_g of the composite. The dynamic mechanical analysis shows that the compoaite possesses extremely higher dynamic storage moduli, which indicates that this LCE6/DDM/CF composite can be a high performance composite. Thus, the compoaite can be a potential candidate for advanced composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40363.     

含苯并恶嗪单元的双邻苯二甲腈树脂的粘接性能

采用含苯并恶嗪单元的双邻苯二甲腈树脂(BZ-BPH)粘接经过处理表面为新鲜铝合金层及氧化物的铝合金基片,对粘接样的室温及高温热处理后(400℃,30 min)的拉伸性能进行了测试并采用SEM观察了断面的形貌。以上述表面不同的2种铝合金粉体为模型,采用差热扫描(DSC)研究了不同界面对BZ-BPH固化反应的影响。研究结果表明,表面为氧化物的试片室温力学性能远大于表面为铝合金的试片;经过高温热处理后,后者的拉伸剪切强度有较大提高,而前者稍有降低,这表明BZ-BPH具有较好的高温粘接性能。     

Rheological and mechanical properties of thermotropic polyesters with long flexible spacers in the main chain

Linear thermotropic liquid crystalline polymers based on two bisphenol monomers and terephthaloyldichloride were prepared via melt polymerization. Fibers from liquid crystalline polymers were spun above the mesophase transition temperature. In this work, the mechanical and morphological properties of fibers based on such polymers were studied. High values of tensile strength and tensile modulus were obtained, and we tried to prove these high mechanical properties quantitavely by using rheological properties of these polymers and morphology of their fibers. These values were varied by the take-up speed.     

液晶双马来酰亚胺/环氧树脂共聚物的制备

本文采用含柔性链（C10）的液晶双马来酰亚胺和含联苯基的液晶环氧树脂合成共聚物，经FTIR、DSC、偏光显微镜、SEM表征了该共聚物的结构与液晶特征。结果表明该共聚物具有较好热致液晶性，其液晶织态呈向列型织构，亦能保留在交联网络结构中。     

Toughening of Diglycidyl Ether of Bisphenol-A Epoxy Resin Using Poly (Ether Ether Ketone) with Pendent Ditert-Butyl Groups

Poly(ether ether ketone) (PEEKDT), hydroxyl terminated poly(ether ether ketone) (PEEKDTOH) and fluorine terminated poly (ether ether ketone) (PEEKDTF) with pendent ditert-butyl groups were synthesized by the nucleophilic substitution reaction of 4,4′-difluorobenzophenone with 2,5-ditert-butylhydroquinone in N-methyl-2-pyrrolidone medium using anhydrous potassium carbonate as catalyst. Diglycidyl ether of bisphenol-A epoxy resin was blended with PEEKDT, PEEKDTOH, and PEEKDTF, and cured with 4,4′-diaminodiphenylsulfone (DDS). The polymers formed heterogeneous blends before curing, and upon curing the polymers got dispersed in the epoxy matrix. The mechanical properties of the cured blends were slightly lower than that of the unmodified resin. The fracture toughness increased with the addition of ditert-butyl PEEK into epoxy resin and the extent of improvement was dependent on the type of modifier used. Hydroxyl terminated polymers gave up to 40% increase in fracture toughness. The dynamic mechanical spectrum of the blends showed only a single T_g due to the proximity of the glass transition temperature of modified PEEK and DDS cured epoxy resin.     

环氧树脂/环氧液晶/蒙脱土纳米复合材料研究

采用液晶环氧预聚物(PHQEP)与有机蒙脱土(OMMT)共混改性环氧树脂制备三元共混体系的环氧基复合材料。用X射线衍射法(XRD)测试了有机化蒙脱土在被插层前后片层间距的变化,通过DSC、TGA及SEM等对PHQEP/OMMT增韧改性环氧树脂固化体系的力学性能,热性能及微观相态结构进行了研究。结果表明:当PHQEP质量分数为5%,添加1.5%的有机蒙脱土可以使环氧树脂的冲击强度达到最大值23.43 kJ/m2,比纯环氧树脂提高2倍左右,玻璃化转变温度及5%热分解温度比纯环氧树脂分别高出15℃和27℃。PHQEP与OMMT的加入使纳米复合材料的力学性能和热性能得到明显提高。     

Liquid crystalline epoxy resin based on biphenyl mesogen: Effect of magnetic field orientation during cure

A biphenyl based epoxy monomer, 4,4′-diglycidyloxybiphenyl (BP), was synthesized and cured with a tetra-functional amine, sulfanilamide (SAA), to obtain a liquid crystalline epoxy network. The curing behavior of BP with SAA was studied using differential scanning calorimetry, polarized optical microscopy, and parallel plate rheology. Macroscopic orientation of the liquid crystalline epoxy resins (LCERs) was achieved by curing in a high strength magnetic field, and quantified by an orientation parameter determined with wide angle X-ray diffraction. The effects of orientation on the glass transition temperature, coefficient of thermal expansion, and dynamic mechanical properties of the LCERs were investigated. The results reveal that the formation of the liquid crystalline phase has a dramatic influence on the curing reaction, leading to a decrease in viscosity of the reacting system. Oriented LCERs exhibit anisotropic thermal expansion behavior and significant improvements of thermomechanical properties.     

Wear and mechanical properties of reactive thermotropic liquid crystalline polymer/unsaturated polyester/glass fiber hybrid composites

To improve the performance of unsaturated polyester (UP) under cold‐heat alternate temperature, self‐synthesized reactive thermotropic liquid crystalline polymer (TLCP)‐methacryloyl copolymer (LCMC), UP, and glass fiber (GF) hybrid composites was prepared by molding technology. The apparent activation energy and crystal behavior analysis of LCMC/UP blends were investigated by Differential scanning calorimetry and X‐ray diffraction (XRD), respectively, the results showed that the addition of LCMC can reduce apparent activation energy and accelerate the curing reaction of UP, the XRD analysis indicated that the crystal phase of LCMC still exist in the blends after blending with UP. The effect of LCMC content on the properties of LCMC/UP/GF hybrid composites such as impact strength, bending strength, and ring‐on‐block wear were also investigated through static mechanical tests and wear tests. The mechanical properties of hybrid composites increased significantly because of the addition of LCMC. The wear tests showed that LCMC can improve the wear resistance of the UP/GF/LCMC hybrid composites even though the content of LCMC was at a relatively low level (5–7.5 wt %). This makes it possible to develop novel kind of UP‐based materials with good wear resistance for various applications. The Worn surface was observed by scanning electron microscopy (SEM) and the mechanism for the improvement is discussed in this paper. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3899–3906, 2007