适用于RTM成型的高性能环氧树脂体系的研制

通过优化实验得到了具有室温粘度小于1000 mPa·s,凝胶化和固化时间短,固化时放热量少,有足够的适用时间(室温下适用期大于48 h)等满足RTM成型要求的树脂体系。经拉伸强度、弯曲强度、剪切强度及模量的测试表明该体系具有较好的强韧性。通过扫描电镜照片,表明微观结构均匀致密,树脂基体的湿润性良好,断裂形式为韧性破坏。     

复合材料缠绕成型用电子束固化环氧树脂体系研究

为了研究适合于缠绕成型的低粘度可电子束固化复合材料的耐热环氧树脂基体,研究了不同组成的电子束固化树脂体系的粘度与温度的关系、耐热性与辐射剂量的关系及浇注体的力学性能。研究表明,树脂EB-4在60℃时粘度为389 mPa.s,树脂辐射固化的最佳剂量为150 kGy,而且在150 kGy辐射固化的EB-1、EB-4的玻璃化转变温度Tg分别为212.96℃、214.77℃,EB-4树脂浇注体的拉伸强度可以达到52.7 MPa,拉伸弹性模量2.79 GPa,断裂延伸率为2.18%,是1种适用于室温或低温下缠绕成型的耐热电子束固化环氧树脂基复合材料树脂体系。     

Evaluation of dielectric cure models for an epoxy-amine resin system

The parallel-plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre-gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time-temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.     

新颖的氯丁橡胶交联剂：天然氨基酸

硫脲类促进剂乙烯硫脲（ETU）被广泛应用于氯丁橡胶（CR）的硫化中，硫化后能得到良好的力学性能、抗老化性能和密封性能。然而，ETU被认为是有潜在致癌作用的化合物，因此对ETU的高效能替代品的研究就相继出现。该研究使用天然氨基酸衍生物——二甲基L-胱氨酸作为CR的硫化促进剂。这是一种环境友好型的化合物，它优化了硫化性能和力学性能，如定伸应力、拉伸强度、断裂伸长率和硬度。对此交联剂的用量和硫化温度也进行了讨论。同时，MgO的含量和活性对二甲基L-胱氨酸硫化的性能有很大影响。     

Bio-resourced furan resin as a sustainable alternative to petroleum-based phenolic resin for making GFR polymer composites

Iranian Polymer Journal - Toward sustainability of polymer-matrix composites, this study aimed to prepare and evaluate glass fiber reinforced (GFR) biocomposites of fully bio-based furan resin, and...     

Naturally occurring amino acid: Novel curatives for chloroprene rubber

Polychloroprene is a diene rubber, but unlike other diene rubbers, its compounding with various additives and curing mechanisms is different. A derivative of thiourea, ethylene thiourea (ETU), is widely used to vulcanize chloroprene rubber (CR), and the vulcanizates thus obtained exhibit excellent mechanical properties, good aging resistance, and very good sealing properties. However, the problem is that ETU is reported to be a potent carcinogenic compound, and hence, the effective substitution for ETU has been extensively explored. In this study, we used a naturally occurring amino acid derivative, dimethyl L ‐cystine, as an ecofriendly compound for the vulcanization of CR. It had a significant influence on the curing characteristics and mechanical properties, such as modulus, tensile strength, elongation at break, and hardness values. The concentration of this novel crosslinking agent and also the curing temperature were optimized. In the presence of dimethyl L ‐cystine, the amount and activity of magnesium oxide also exhibited significant influences on the crosslinking characteristics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3981–3986, 2006     

Cure kinetics of epoxy resin used for advanced composites

The cure kinetics of an epoxy resin used for the preparation of advanced polymeric composite structures was studied by isothermal differential scanning calorimetry (DSC). A series of isothermal DSC runs provided information about the kinetics of cure over a wide temperature range. According to the heat evolution behavior during the curing process, several influencing factors of isothermal curing reactions were evaluated. The results showed that the isothermal kinetic reaction of this epoxy resin followed an autocatalytic kinetic mechanism. In the latter reaction stage, the curing reaction became controlled mainly by diffusion. Cure rate was then modeled using a modified Kamal autocatalytic model that accounts for the shift from a chemically controlled reaction to a diffusion‐controlled reaction. The model parameters were determined by a nonlinear multiple regression method. Copyright © 2004 Society of Chemical Industry     

Thermal characterization of a bis-maleimide/bis-cyanate/epoxy thermosetting resin for composites

The thermosetting resin investigated here was a mixture of bis-maleimide and bis-cyanate, frequently referred to as BT (bis-maleimide triazine). Triazine is the reaction product of the cyclotrimerization of bis-cyanate during curing. For circuit board applications, a brominated epoxy resin was blended with BT to impact flame resistance. Resin cure was extensively investigated using a combination of thermoanalytical techniques (thermal analysis, heated cell infrared spectroscopy, and dynamic mechanical analysis). The ultimate glass transition temperature was found to be 240°C, which could only be obtained using cure temperatures above 225°C. At lower temperatures, the reaction does not reach full conversion, since the glass transition temperature of the curing network equals or slightly exceeds the cure temperature. Differential scanning calorimetry (DSC) indicates a minimum of two separate reactions. Fourier transform infrared spectroscopy provided more detailed information on the crosslinking reactions during cure. The onset of cyclotrimerization was found to start at 150°C, correlating with one of the peaks in the DSC. At higher temperatures, the epoxide reacts with the cyanate functionality forming oxazoline ring structures. It was not possible to unambiguously assign the origins of the high temperature peaks in the DSC. These high temperature peaks may be attributed to several reactions, including epoxy homopolymerization and polymerization of bis-maleimide. The high temperature reaction mechanisms warrant further investigation.     

Processability and properties of phenoxy resin toughened phenolic resin composites

A novel method has been developed to toughen phenolic resin using phenoxy resin. Phenoxy resin was dissolved in phenol to form a glutinous mixture at 110°C, and an acid catalyst (p-toluene sulfonic acid, PTSA) was utilized to reduce the viscosity of mixture. The mixture was blended with resole-type phenolic resin. IR spectra confirmed that the amount and strength of hydrogen bonds increased with PTSA content, and the viscosity decreased with PTSA content in the polymer blends. The wet-out of glass fiber by modified resin was improved. The flexural and notched Izod impact strength of the polymer-blend composites increased significantly. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 911–917, 1997     

Modeling fracture of resin matrix composites

Characteristics of the fracture of resin matrix fibrous composites are discussed with emphasis on the physical parameters influencing fracture and the requirements of a suitable model for predicting crack growth. The influences of notch geometry, fiber orientation, specimen geometry, and far field loading on crack growth in unidirectional resin matrix composites are discussed. The normal stress ratio theory is reviewed and its applicability for crack initiation in unidirectional resin matrix composites is considered. Experimental results from a variety of tests on resin matrix composites are reviewed and compared with theoretical predictions. It is shown that the normal stress ratio theory correctly predicts the initiation site and direction of crack growth from an existing notch. Predictions of critical stress are less consistent being quite accurate in some cases, but less accurate in others.     

环氧树脂固化剂的改性研究

以异佛尔酮二胺和1,6-己二胺为原料,加入适量自制的催化剂,在190℃反应2.5 h,即制成新型环氧树脂固化剂(简称YFJA)。将其按不同比例添加到传统固化剂二氨基二苯甲烷(简称DDM)和甲基四氢苯酐(简称Me-THPA)中,通过对固化物的冲击强度、拉伸强度和力学损耗等性能的检测分析,发现当自制固化剂添加量为固化剂总量的50%时,体系的力学性能达到最佳效果,冲击强度最高可提高346.5%,拉伸强度可提高73.0%。     

Elevated temperature testing for comparison of glass/resin composites

Static test methods were used to evaluate and compare the thermal and mechanical properties of several glass/thermoset laminated composites between 25° and 400°C. The unidirectional matrix composites consisted of phenolic-modified epoxy, epoxy novolac, epoxy, and modified phenolic resins. These materials were selected as potential alternative materials for rotary compressor vanes. Dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA) techniques were selected to evaluate elevated temperature performance. The short-beam shear test was chosen to measure interlaminar shear properties. The results indicated that an elevated-temperature matrix, such as the modified phenolic resin, may not result in optimum composite strengths. Instead, an epoxy resin reinforced with glass fibers provides a better balance between elevated-temperature performance and interlaminar shear strength. The test results of this study, in addition to being adequate for discriminating the materials for initial selection purposes, were obtained quickly and easily. Moreover, the thermal results provide a more realistic understanding of composite elevated-temperature characteristic than do those of the present standard test.     

Cure behaviour of epoxy resin matrices for carbon fibre composites

The cure behaviour of two resin formulations (with high and low curing agent content respectively) of an epoxy resin system, used as matrix for carbon fibre composites, was studied through calorimetric analysis. The aim of this work is to investigate the kinetics of this specific epoxy system in order to be able to choose a proper set of processing parameters which will give good composite material properties. The shape of the conversion curves gives evidence of the differences in the cure kinetics of the two systems. Furthermore, the values of the activation energies were determined both for formulation in the conversion range where vitrification occurs, following a phenomenological approach. These values give an indication of the differences in the curing mechanisms, when varying the content of curing agent. In particular, for both systems, the same reaction represents the onset of the cure process, ie the autocatalytic epoxy ring opening through addition reaction to the primary amine. This reaction dominates the entire cure process of the epoxy formulation at high curing agent content. Conversely, in the formulations with a low curing agent content, after depletion of the primary amines, different reactions may take place (with secondary amines and hydroxyl groups), depending on the cure temperature and the resin viscosity. © 1999 Society of Chemical Industry     

PANI-PMN/环氧树脂复合材料的制备

用自制的聚苯胺（PANI）包覆铌镁锫钛酸铅（PMN）粉末为功能相，以环氧树脂为基体，制备了PANI—PMN／环氧树脂复合材料。当w（PANI—PMN）小于60％时，随w（PANI～PMN）的增大复合材料的压缩强度有所提高。当w（PANI-PMN）大于60％时，压缩强度降低。随着w（PANI—PMN）的提高，试样的电导率增大。PANI包覆PMN制备的复合材料的阻尼损耗因子提高。在PANI—PMN／环氧树脂复合材料中，除环氧树脂的黏弹性阻尼、填料与基体的相互作用耗能外，还存在压电阻尼作用，并且具有一定电导率的体系有利于压电阻尼发挥作用。     

Viscoelastic behavior of boron fiber-epoxy resin composites

A torsion pendulum study of boron fiber-epoxy resin composites has shown marked deviations, at elevated temperatures, from the predicted behavior. A new damping peak at approximately 180°C as measured at 5 Hz is present which appears to be independent of the type of epoxy resin present in the matrix. This peak is attributed to interfacial effects between the boron fibers and the matrix resin. A linear model is tentatively proposed to explain this effect.     

Comparison of the thermal stabilities of some resin matrices for composites

The thermal stabilities of eleven different epoxy resin formulations, ten different polyimide resin formulations, a triazine resin formulation and two aromatic thermoplastic matrices have been compared by isothermal gravimetry in air. The overall activation energies for degradation as a function of percentage weight loss have been determined by regression analysis of the isothermal data. The values obtained indicate a very complex breakdown mechanism in the majority of cases.     

Green composites using switchgrass as a reinforcement for a conjugated linseed oil‐based resin

Switchgrass (SWG) has been used as a filler to produce conjugated linseed oil‐based green composites. The effect of the amount of the SWG; the matrix crosslink density; and the incorporation of a compatibilizer, maleic anhydride (MA), on the structure, water absorption, and thermal and mechanical properties of the composites has been investigated. The thermal stability of the composites is primarily dependent on the amount of the SWG fibers, which are far less thermally stable than the linseed oil‐based resin. For the most part, improvements in the mechanical properties can be achieved by increasing the amount of SWG (up to 70 wt %), increasing the amount of the crosslinker, and adding MA to increase the filler–matrix interaction. The uptake of water in the composites is mostly influenced by the loading of the SWG fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013