Studies on the properties of glass fiber reinforced epoxy composites of DGEBA / epoxidized polyhydric alcohols with or without fortifier

Differential scanning calorimetry (DSC) technique was used to study the curing reaction of diglycidyl ether of bisphenol A (DGEBA) resin and different di- and trifunctional polyhydric alcohols with phthalic anhydride as curing agent and triethylamine as catalyst with or without fortifier. The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied as well. Activation energies of curing reactions range within 75.1 to 88.3 kJ mol^?1. The cured products have good thermal stability; the composites have good mechanical strength, electrical insulation properties and chemical resistance. 36 to 53% improvement in flexural strength has been observed when fortifier was added to the DGEBA-diluent systems.     

Properties and curing behavior of reactive blended allyl novolak with bismaleimide using dicumyl peroxide as a novel curing agent

For reducing the cure temperature and improving the thermal stability and mechanical properties, a thermosetting resin system composed of novolak and bismaleimide (BMI) was developed by reactive blending and using dicumyl peroxide (DCP) as a novel curing agent. Novolak was allylated and reacted with BMI to produce bismaleimide allylated novolak (BAN), and the effect of DCP on flexural, impact and heat distortion temperature of cured resin were investigated. On the basis of improved mechanical and thermal properties at 0.5% DCP contents, the curing behavior of DCP/BAN resin system was evaluated by DSC analysis. Ene, Diels‐Alder, homo‐polymerization and alternating copolymerization which occurred in DCP/BAN resin system were further verified using FTIR at sequential cure conditions from 140 to 200°C. Kissinger and Ozawa‐Flynn‐wall methods were used to optimize the process and curing reactions of DCP/BAN resin system. The results showed that the addition of 0.5% DCP in BAN reduced the curing temperature and time of the modified resin. For evaluating process ability of the modified system, composite samples using polyvinyl acetyl fiber were molded and tested for flexural properties. The resulting samples showed better flexural properties when compared with the composite made with neat BAN. The modified 0.5% DCP/BAN resin system with good mechanical properties and manufacturability can be used for making bulk molding compounds and fiber reinforced composites required in various commercial and aerospace applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41829.     

Properties of dicumyl peroxide initiated bismaleimide modified allyl novolac and its molded composites

A thermosetting resin system, bismaleimide (BMI) modified allyl novolac (BAN), was developed via reactive blending of formaldehyde and catalyst drop wise to improve the extent of reaction between BMI and phenol‐carbenium ions. For improving the curing behavior and mechanical properties, dicumyl peroxide (DCP) was selected as a novel curing initiator to compare with hexamethylenetetramine (HTMA) which is the most common curing initiator used in the manufacture of phenolic resins. BAN was characterized by ¹H nuclear magnetic resonance and Fourier transfer infrared spectroscopy. Curing behavior with initiators was analyzed by differential scanning calorimetry and glass transition temperature of the cured resins was examined by dynamic mechanical analysis. For evaluating efficiency of the modified system, composite samples using polyvinyl acetyl fiber were molded and tested for flexural properties before and after ageing at 150°C for 1,000 h. The morphology of composite samples was examined by scanning electron microscope, and the effects of the incorporated initiators on the mechanical and thermal properties of composite were investigated. The results indicated that the initiators reduced the curing temperature effectively and improved the curing process. DCP proved to be more effective in crosslinking and heat resistance than HTMA. Meanwhile, the molded composite with DCP showed higher mechanical properties before and after ageing when compared with HTMA curing initiator. Therefore, DCP/BAN resin system with good heat resistance, higher mechanical properties, and better process ability can be applied as matrix resin for the manufacturing of advanced fiber reinforced composites. POLYM. COMPOS., 37:2260–2271, 2016. © 2015 Society of Plastics Engineers     

Solid freeform fabrication of epoxidized soybean oil/epoxy composites with di‐, tri‐, and polyethylene amine curing agents

Soybean oil/epoxy‐based composites are prepared by solid freeform fabrication (SFF) methods. SFF methods built materials by the repetitive addition of thin layers. The mixture of epoxidized soybean oil and epoxy resin is modified with di‐, tri‐, or polyethylene amine gelling agent to solidify the materials until curing occurs. The high strength and stiffness composites are formed through fiber reinforcement. E‐glass, carbon, and mineral fibers are used in the formulations. The type of fiber affects the properties of the composites. It was found that a combination of two types of fibers could be used to achieve higher strength and stiffness parts than can be obtained from a single fiber type. In addition, the effects of curing temperature, curing time, and fiber concentration on mechanical properties of composites are studied and reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 356–363, 2004     

Preparation and characterization of modified‐clay‐reinforced and toughened epoxy‐resin nanocomposites

Epoxy–clay nanocomposites were prepared by the dispersion of an organically modified layered clay in an epoxy resin (diglycidyl ether of bisphenol A) and curing in the presence of methyl tetrahydro acid anhydride at 80–160°C. The nanometer‐scale dispersion of layered clay within the crosslinked epoxy‐resin matrix was confirmed by X‐ray diffraction and transmission electron microscopy, and the basal spacing of the silicate layer was greater than 100–150 Å. Experiments indicated that the hydroxyethyl groups of the alkyl ammonium ions, which were located in the galleries of organically modified clay, participated in the curing reaction and were directly linked to the epoxy‐resin matrix network. Experimental results showed that the properties of epoxy were improved, evidently because of the loading of organically modified clay. The impact strength and tensile strength of the nanocomposites increased by 87.8 and 20.9%, respectively, when 3 wt % organic clay was loaded, and this demonstrated that the composites were toughened and strengthened. The thermal‐decomposition and heat‐distortion temperatures were heightened in comparison with those of pure epoxy resin, and so were the dynamic mechanical properties, including the storage modulus and glass‐transition temperature. Moreover, experiments showed that most properties of the composites were ameliorated with low clay contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2649–2652, 2004     

Synthesis and characterization of chlorinated soy oil based epoxy resin/glass fiber composites

Composites with good toughness properties were prepared from chemically modified soy epoxy resin and glass fiber without additional petroleum based toughening agent. Chlorinated soy epoxy (CSE) resin was prepared from soybean oil. The CSE was characterised by spectral, and titration method. The prepared CSE was blended with commercial epoxy resin in different ratios and cured at 85°C for 3 h, and post cured at 225°C for 2 h using m‐phenylene diamine (MPDA) as curing agent. The cure temperatures of epoxy/CSE/MPDA with different compositions were found to be in the range of (151.2–187.5°C). The composite laminates were fabricated using epoxy /CSE/MPDA‐glass fiber at different compositions. The mechanical properties such as tensile strength (248–299 MPa), tensile modulus (2.4–3.4 GPa), flexural strength (346–379 MPa), flexural modulus (6.3–7.8 GPa) and impact strength (29.7–34.2) were determined. The impact strength increased with the increase in the CSE content. The interlaminor fracture toughness (G_IC) values also increased from 0.6953 KJ/m² for neat epoxy resin to 0.9514 KJ/m² for 15%CSE epoxy‐modified system. Thermogravimetric studies reveal that the thermal stability of the neat epoxy resin was decreased by incorporation of CSE. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Development of soybean oil‐based composites by solid freeform fabrication method: Epoxidized soybean oil with bis or polyalkyleneamine curing agents system

Soybean oil‐based composites are prepared by the solid freeforming fabrication (SFF) method. Epoxidized soybean oil is solidified with a gelling agent, and composites are formed by fiber reinforcement. Glass, carbon, and mineral fibers are used in the formulations. The type of fiber and degree of fiber alignments affect the properties of the composites. In addition, the effects of curing agents, curing temperature, fiber combination, and fiber loading on mechanical properties of composites and dynamic analysis are studied and reported. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2100–2107, 2002     

Effect of curing method on mechanical and morphological properties of carbon fiber epoxy composites for solid rocket motor

Microwave (MW) curing and conventional thermal curing techniques were utilized to cure carbon fiber epoxy composites for solid rocket motor to investigate the effect of curing method on their mechanical and morphological properties. In this work, tensile and inplane shear strength properties together with morphological properties were compared between MW cured and thermally cured composites, and the mechanism for MW curing was analyzed. The study shows that 83% cure cycle time reduction is achieved through MW curing. Mechanism analysis for MW curing indicates the resin at the surface layer and interior parts of the composites is cured with different forms. Temperature monitoring during MW processing indicates the uneven electric field distribution in the domestic MW oven. Fourier transform infrared spectrum measurements reveal that MWs do not initiate any new chemical reactions during the curing process of the composites. Thermal analysis using differential scanning calorimeter reveals higher glass transition temperature (T_g) of MW cured composites compared with thermally cured counterparts. Moreover, the MW cured composites show 17% lower tensile strength than thermally cured composites, whereas a 3% increase of the inplane shear strength is observed for MW cured composites, which is also confirmed via scanning electron microscope by means of better coating the fibers with resin, increased fiber wetting and less fiber pullout. POLYM. COMPOS., 36:1703–1711, 2015. © 2014 Society of Plastics Engineers     

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.     

长玻璃纤维增强聚丙烯复合材料的力学性能研究

采用熔体浸渍技术制备了长玻璃纤维母料(LGF/PP-g-MAH/PP)增强聚丙烯(PP)复合材料(LGF/PP)。通过双螺杆挤出机制备了同等配比的短玻纤增强聚丙烯(SGF/PP)复合材料。研究了LGF含量、环氧树脂(EP)和固化剂(2E4MZ)对LGF/PP复合材料的力学性能影响。结果表明:当LGF质量分数为35%～40%时,LGF/PP的综合力学性能最好,且明显优于同样组成的SGF/PP复合材料。EP和含固化剂(2E4MZ)的EP对LGF/PP复合材料的力学性能提高有一定的作用。SEM照片分析表明:EP的加入能改善玻纤与聚丙烯基体的界面粘接。     

Preparation and properties of dipropargyl ether of bisphenol A‐modified bismaleimide resins and composites

A kind of modified bismaleimide resin, with good heat resistance and processing properties for advanced composites, was developed. The modifier, dipropargyl ether of bisphenol A (DPBPA), was prepared by a phase‐transfer catalyzing procedure, characterized by FTIR, ¹H NMR, and elementary analysis, and used to modify 4,4′‐bismaleimidodiphenylmethane (BMDPM). The thermopolymerization of a DPBPA‐modified BMDPM resin was followed up by FTIR. The curing of the resin was investigated by differential scanning calorimeter and gelation characterization. The relation of viscosity and temperature was used to characterize the processability of the resin. The results of DMA analysis showed that the cured DPBPA‐modified BMDPM resins had a glass transition temperature higher than 320°C. The carbon fiber (T700) reinforced composites showed excellent flexural properties at ambient temperature and at 250°C. DPBPA could effectively improve mechanical properties without deteriorating heat resistance of the BMDPM resin a lot. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Mechanical properties of poly(styrene‐co‐acrylonitrile)‐modified epoxy resin/glass fiber composites

Poly(styrene‐co‐acylonitrile) was used to modify diglycedyl ether of bisphenol‐A type epoxy resin cured with diamino diphenyl sulfone and the modified epoxy resin was used as the matrix for fiber‐reinforced composites (FRPs) to get improved mechanical properties. E‐glass fiber was used as fiber reinforcement. The tensile, flexural, and impact properties of the blends and composites were investigated. The blends exhibited considerable improvement in mechanical properties. The scanning electron micrographs of the fractured surfaces of the blends and tensile fractured surfaces of the composites were also analyzed. The micrographs showed the influence of morphology on the properties of blends. Results showed that the mechanical properties of glass FRPs increased gradually upon fiber loading. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

CA型环氧树脂固化剂性能研究

用ＩＲ光谱表征了自制ＣＡ型环氧树脂固化剂的结构特点,测定了ＣＡ型固化剂的固化特性,固化树脂的性能和增塑效果。实验结果表明,ＣＡ型固化剂能使环氧树脂涂料在潮湿表面和带油表面上固化成膜,其固化的树脂具有良好的耐蚀性,冲击强度较二乙撑三胺固化的树脂有较大提高,同时也是一种较好的环氧树脂用增塑剂。     

Toughened epoxy resin matrix for a membrane shell by wet filament winding

A toughened epoxy resin matrix was obtained with a reactive toughening agent and methyl hexahydrophthalic anhydride as a curing agent. The mechanical properties of the modified epoxy resin and its glass‐fiber‐reinforced composites were investigated systematically. The modified epoxy resin matrix possessed many good properties, including a high flexural strength (138 MPa), high elongation at break (5.2%), low viscosity, long pot life at room temperature, and good water resistance. In addition, the glass‐fiber‐reinforced composites showed a high strength conversion ratio of the glass fiber (86.7%) and good fatigue resistance. The results demonstrated that the modified epoxy resin matrix is very suitable for applications in reverse osmosis membrane shell products fabricated with wet filament winding for water treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚丙烯/马来酸酐接枝聚丙烯/环氧树脂/玻璃纤维复合材料的制备及其性能研究

通过双螺杆挤出机制备了聚丙烯/马来酸酐接枝聚丙烯/环氧树脂/玻璃纤维（PP/PP-g-MAH/EP/GF）复合材料,并研究了PP-g-MAH含量、EP含量及固化剂对复合材料力学性能的影响。结果表明,PP-g-MAH含量为10份,含有固化剂EP的含量为3份时,复合材料的综合力学性能最佳;与不加EP的复合材料相比,其拉伸强度、弯曲强度、冲击强度分别提高了41 %、47 %、86 %。扫描电子显微镜分析表明,EP的加入明显改善了GF和PP基体的黏结强度。     

棉油酸甲酯改性胺固化剂的合成及性能研究

利用棉油酸甲酯制备了一种环氧树脂固化剂棉油酸甲酯改性胺,研究了棉油酸甲酯改性胺用量对环氧树脂体系的力学性能和热性能的影响,利用红外光谱、热分析、动态力学分析讨论了棉油酸甲酯改性胺的结构、环氧树脂固化物的性能。结果表明,环氧树脂固化物的拉伸性能、弯曲性能和冲击强度随着棉油酸甲酯改性胺用量的增加而增加。     

兆瓦级风力发电机叶片用环氧树脂

针对兆瓦级风机叶片用纤维/环氧复合材料的特殊要求,开展了适用于真空辅助灌注(VARTM)工艺的环氧基体树脂的国产化研究。采用国产环氧树脂与实验室自制的稀释剂制备环氧树脂与胺类固化剂配合使用,通过示差扫描量热分析,IR光谱,力学性能,耐热性、粘度及吸水性测试等研究了环氧树脂与固化剂配比对其工艺和固化物性能的影响,获得了初始粘度低、粘度对温度不敏感、操作时间长的环氧基体树脂,其树脂浇注体的拉伸性能、弯曲性能均优于国外环氧树脂固化体系,可满足兆瓦级风机叶片用高性能复合材料的使用需求。     

Improved thermomechanical properties of carbon fiber reinforced epoxy composite using amino functionalized XDCNT

Carbon fiber‐reinforced epoxy composites (CFEC) are fabricated infusing up to 0.40 wt % amino‐functionalized XD‐grade carbon nanotubes (XDCNT) using the compression molding process. Interlaminar shear strength (ILSS) and thermomechanical properties of these composites are evaluated through short beam shear and dynamic–mechanical thermal analysis tests. XDCNTs are infused into Epon 862 resin using a mechanical stirrer followed by sonication. After the sonication, the mixture was placed in a three roll milling processor for three successive cycles at 140 rpm for uniform dispersion of CNTs. Epikure W curing agent was then added to the resin using a high‐speed mechanical stirrer. Finally, the fiber was reinforced with the modified resin using the compressive mold. ILSS was observed to increase by 22% at 0.3 wt % XDCNT loading. Thermal properties, including storage modulus, glass transition temperature, and crosslink density demonstrated linear enhancement up to the 0.3 wt % XDCNT loading. Scanning electron microscopy revealed better interfacial bonding in the CNT‐loaded CFEC. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40709.     

空心玻璃微珠/环氧复合材料的制备及性能研究

制备了空心玻璃微珠/环氧复合材料。通过力学性能、固化收缩率、热性能等测试考察了空心玻璃微珠粒径、填充量、硅烷偶联剂处理对树脂及固化物性能的影响。结果表明,硅烷偶联剂改善了空心玻璃微珠与树脂基体的相容性。复合材料的力学性能随着空心微珠粒径减小而增大。随着空心微珠填充量的加大,固化物拉伸强度有所降低,冲击强度和弯曲强度在空心玻璃微珠质量分数为2%时达到最大值,比纯树脂分别提高了30%和34.2%,同时材料的固化收缩率和密度降低,玻璃化转变温度升高。     

短切碳纤维对聚苯腈/碳纤维复合材料性能的影响

利用碳纤维（CF）增强聚苯腈（PN）树脂制备一系列PN/CF复合材料,利用万能试验机和动态热机械分析仪（DMA）,研究短CF含量、长度与偶联剂种类对PN树脂力学性能的影响。结果表明,采用苯基三乙氧基硅烷作为偶联剂时力学性能和热稳定性达到最佳水平,相较于未经偶联剂改性PN/CF复合材料的储能模量提高了22.2%,热失重5%温度（Td5%）提高了33.1%;随着CF掺杂量的增加,材料力学性能呈现先增大后减小趋势,在0.3%（质量分数,下同）时获得了最优异力学性能,相较于PN树脂,其弯曲强度提高了38.4%,弯曲模量提升了97.7%;CF长度为6 mm时材料的弯曲强度和储能模量优于CF长度为3 mm时的材料。