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1.
H. -J. Sue J. L. Bertram E. I. Garcia-Meitin J. W. Wilchester L. L. Walker 《Colloid and polymer science》1994,272(4):456-466
The fracture behavior of a core-shell rubber (CSR) modified cross-linkable epoxy thermoplastic (CET) system, which exhibits high rigidity, highT
g, and low crosslink density characteristics, is examined. The toughening mechanisms in this modified CET system are found to be cavitation of the CSR particles, followed by formation of extended shear banding around the advancing crack. With an addition of only 5 wt.% CSR, the modified CET possesses a greater than five-fold increase in fracture toughness (G
IC) as well as greatly improved fatigue crack propagation resistance properties, with respect to those of the neat resin equivalents. The fracture mechanisms observed under static loading and under fatigue cyclic loading are compared and discussed. 相似文献
2.
Graft interpenetrating polymer networks (graft-IPNs) of polyurethane (PU) and the diglycidyl ether of bisphenol A (epoxy) were prepared by first grafting excess PU prepolymer to the epoxy and then simultaneously polymerizing the PU prepolymer and epoxy. The fracture properties, at high shear rate (e.g., impact) and low shear rate (e.g., pseudostatic tensile fracture energy measurement) of these graft-IPNs exhibit opposite behavior. Although dispersed rubber particles can enhance the Izod impact strength, toughening of the matrix of graft-IPNs was found to be the main contribution. In contrast, it was found that a heterogeneous morphology with suitably dispersed rubber domains of appropriate size as well as the toughness of the matrix are requirements for effectively increasing the fracture energy at low shear rate. A reinitiating crack in the plastic matrix is proposed as the main toughening mechanism and can be invoked to interpret the fracture behavior at high and low shear rates of the graft-IPNs. 相似文献
3.
The use of emulsion polymerization to prepare core–shell rubber (CSR) toughening particles with different shell thickness-to-core diameter ratios is described. The conditions leading to controlled particle size and morphology are discussed. The particle shell is crosslinked during the synthesis so that its integrity and morphology are maintained upon curing of the epoxy network. The mixing of the CSR particles with the reactive epoxy and the processing of toughened-epoxy networks are described. The characteristics of each phase and the mechanical properties of the materials are reported. The fracture parameters (Klc, Glc) are discussed in relation to the structure of the CSR-particles. 相似文献
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H. -J. Sue E. I. Garcia Meitin D. M. Pickelman C. J. Bott 《Colloid and polymer science》1996,274(4):342-349
The fracture mechanisms of a high performance epoxy system modified with two types of preformed rigid core-shell particles (RCSP) were investigated. The use of the preformed RCSP anables the control of the dispersion of the toughener phase in the epoxy, which, in turn, allows the mechanical properties of the modified epoxy to be optimized. The toughening effect via the RCSP modification is found to be as good as that via the core-shell rubber modification. The moduli andT
g of these RCSP-modified epoxies are virtually unaltered via the RCSP modification, when compared with the neat epoxy resin equivalent. The toughening mechanisms in these toughened systems appear to be predominantly crack deflection, crack bifurcation, and microcracking. Approaches for effective toughening of high performance polymers via rigid polymers are discussed. 相似文献
6.
Raju Thomas Jacob Abraham Selvin Thomas P Sabu Thomas 《Journal of Polymer Science.Polymer Physics》2004,42(13):2531-2544
A mixture of epoxy with liquid nitrile rubber, carboxyl‐terminated (butadiene‐co‐acrylonitrile) (CTBN) was cured under various temperatures. The cured resin was a two‐phase system, where spherical rubber domains were dispersed in the matrix of epoxy. The morphology development during cure was investigated by scanning electron microscope (SEM). There was slight reduction in the glass transition temperature of the epoxy matrix (Tg) on the addition of CTBN. It was observed that, for a particular CTBN content, Tg was found to be unaffected by the cure temperature. Bimodal distribution of particles was noted by SEM analysis. The increase in the size of rubber domains with CTBN content is due probably to the coalescence of the rubber particles. The mechanical properties of the cured resin were thoroughly investigated. Although there was a slight reduction in tensile strength and young's modulus, appreciable improvements in impact strength, fracture energy, and fracture toughness were observed. Addition of nitrile rubber above 20 parts per hundred parts of resin (phr) made the epoxy network more flexible. The volume fraction of dispersed rubbery phase and interfacial area were increased with the addition of more CTBN. A two‐phase morphology was further established by dynamic mechanical analysis (DMA). © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2531–2544, 2004 相似文献
7.
H.-J. Sue J. L. Bertram E. I. Garcia-Meitin P. M. Puckett 《Journal of Polymer Science.Polymer Physics》1995,33(14):2003-2017
Formation of dilatation bands has been found in a series of moderately crosslinked thermosets with molecular weights between crosslinks, Mc, ranging from 560 to 1000 g/mole. These dilatation bands, although they do not show distinct craze fibrils inside the band, do behave mechanically like the well-known crazing phenomenon observed in polystyrene. Although the cause for the formation of dilatation bands is still largely unknown, the occurrence of the craze-like fracture phenomenon (dilatation bands) is found to be strongly influenced by the stress state the matrix experiences, by the type of loading applied to the specimen, and by the type/size of toughener particles incorporated in the matrix. The tendency for dilatation band formation in engineering thermosets can be greatly enhanced by the use of craze-prone toughener particles, such as nylon particles. The toughening effect via these newly observed dilatation bands is found to be quite impressive, and in some cases, can approach that via the shear-banding process. The potential significance of the present finding for a better design of toughened thermosets for structural applications is discussed. ©1995 John Wiley & Sons, Inc. 相似文献
8.
The following factors affecting the rubber toughened epoxy resin system were studied: 1. kindsof curing agent used, 2. the M_c value of the matrix, 3. the bonding foce between the dispersed phaseand the matrix. Our experimental result indicates that the average chain length between crosslinks(M_c) is a much more important affecting factor. Chemical bonding between the dispersed phaseand the matrix is also important. A toughening mechanism of rubber toughened epoxy has beenproposed. In the material with relatively low crosslinking density, extensive fracture process stripis formed which is induced by the combined stress field near the rubber particles. The chemical bond-ing between the dispersed phase and the matrix may inerease the strength of the local stress field aboutthe rubber particles which is in favor of broading the fracture process area. 相似文献
9.
Hamidreza Ali-Asgari Dehaghi Saeedeh Mazinani Davood Zaarei Mohammadreza Kalaee Hamed Jabari Navid Sedaghat 《Journal of Thermal Analysis and Calorimetry》2013,114(1):185-194
Systematic study about the effect of acrylonitrile–butadiene rubber (NBR) concentration on the fracture toughness and thermal behavior of epoxy resin is conducted in this study. NBR is solved in an aromatic hydrocarbon solvent and is added to epoxy resin. We used diethylene-teriamin as the curing agent for epoxy resin. Tensile test results, performed followed by molding procedure, show that the toughness is improved owing to the increase of rubber content. Scanning electron microscopy (SEM) and atomic force microscopy besides thermogravimetric analysis (TG) are used to investigate the epoxy/rubber interface and chemical decomposition of the resultant mixture. The thermal behavior of cured epoxy resin was analyzed via TG instrument at different heating rates. Thermogravimetry curves showed that the thermal decomposition of epoxy system was occurred in only one stage regardless of the rubber content. The apparent activation energies of the rubber/epoxy systems containing 0, 5, and 10 phr of rubber were determined by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Friedman methods. The results prove that the thermal stability of epoxy resin was decreased with enhancing the rubber content. However, the trend of changing activation energy versus conversions is totally different followed by adding the elastomer to the system compared to neat epoxy resin. Moreover, the results obtained via our proposed facile solution blending method are compared to those of resins modified with nano-powdered elastomer. 相似文献
10.
In this paper, we review recent progress made in the field of epoxy-based binary and ternary nanocomposites containing three-, two-, and one-dimensional (i.e., 3D-, 2D-, and 1D) nano-size fillers with a special focus on their fracture behaviors. Despite investigations conducted so far to evaluate the crack-resistance of epoxy nanocomposites and attempts made to clarify the controlling toughening mechanisms of these materials, some questions remain unsolved. It is shown that silica nanoparticles can be as effective as rubber particles in improving the fracture toughness/energy; but incorporation of carbon nanotubes (CNTs) or clay platelets in epoxy matrices delays crack growth only modestly. The “nano” effects of silica (<25 vol.%) and rubber (>10 wt.%) nanoparticles in toughening epoxy resin are confirmed by comparison with silica and rubber micro-particles of the same loading. There is clear evidence of both synergistic and additive toughening effects in the silica/rubber/epoxy ternary nanocomposites. In addition, positive hybrid toughening effect has been observed in the nano-rubber/CNT/epoxy composites; however, a negative hybrid effect is predominant in nano-clay/nano-rubber/epoxy ternary nano-composites. Future research directions for epoxy-based nanocomposites towards multi-functional applications are discussed. 相似文献
11.
Scrap car tyre particles can be used as filler or toughening agent in rigid epoxy matrices if the resultant interface is adequate. The objective of this work was to investigate the effects of use of different silane coupling agents (SCAs) to improve the interface between the epoxy resin and recycled rubber particles. For this purpose, seven different SCA were used to modify surfaces of the rubber particles. After the preparation of epoxy-rubber specimens, tensile Charpy impact and plane-strain fracture toughness tests were conducted. Mechanical tests and fractographic studies revealed that some of the SCA can improve of the interface between the epoxy matrix and the rubber particles leading to increases in strength while slight decreases in toughness of the samples. 相似文献
12.
In this work the curing kinetics behaviour of a rubber modified epoxy amine system is investigated through calorimetric analysis.
This study is part of a wider investigation on new epoxy formulations to be used as matrices of composite materials. The aim
is to enhance both the processing behaviour and the mechanical properties of the matrix in order to obtain higher performance
composites for more demanding applications. The epoxy system is blended with a high molecular mass rubber containing functional
groups reactive towards the epoxies. The formation of a rubber/epoxy network can be achieved by means of a 'pre-reaction'
between the epoxy monomers and the rubber functional groups, carried out in the presence of a suitable catalyst and before
the resin is cured with the amino hardener. In this work the influence of both the rubber and the catalyst on the resin cure
kinetics is analysed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Poornima Vijayan P Debora Puglia Agnieszka Dąbrowska Pournami Vijayan P Andrzej Huczko Jose M. Kenny Sabu Thomas 《先进技术聚合物》2015,26(2):142-146
The silicon carbide (SiC) nanofibers (0.1, 0.25, and 0.5 phr), produced by self‐propagating high‐temperature synthesis (SHS), are used to reinforce the epoxy matrix cured with an anhydride hardener. Morphological studies reveal a better dispersion of SiC nanofibers and a good level of adhesion between nanofiber and the matrix in composites with lower (0.1 and 0.25 phr) nanofiber loading. The flexural studies show that a maximum increase in flexural properties is obtained for composites with 0.25 phr SiC nanofiber. The fracture toughness of epoxy is found to increase with the incorporation of SiC nanofibers, and 0.25 phr SiC nanofiber loading shows maximum fracture toughness value. The possible fracture mechanisms that exist in epoxy/SiC nanofiber composites have been investigated in detail. Thermogravimetric analysis reveals that SiC nanofibers are effective fillers to improve the thermal stability of epoxy matrix. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
15.
在双螺杆挤出机中制备了环氧官能化的二元乙丙橡胶(gEPR) ,采用红外光谱工作曲线法测量了EPR的接枝率.将环氧官能化的EPR与尼龙6 (Nylon- 6 )熔融共混,并对共混体系的相形态、断裂形貌、增韧机理、力学性能进行了研究.结果表明,gEPR的环氧官能团与Nylon- 6的端羧基和(或)端氨基发生了化学反应生成Nylon -6 co EPR共聚物,该共聚物作为界面改性剂降低了Nylon -6与EPR之间的界面张力,使EPR在Nylon -6基体中均匀、稳定地分散,而且随着EPR接枝率的增加,EPR的粒径尺寸逐渐减小.断面形貌观察发现,与Nylon -6 EPR体系相比,Nyon -6 gEPR共混体系呈现明显的韧性断裂特征.通过对Nylon -6 gEPR共混体系缺口冲击形变区的研究得出EPR增韧Nylon -6的机理是橡胶粒子的空洞化和塑料基体的剪切屈服.力学性能测试表明gEPR的引入显著提高了Nylon -6的缺口冲击强度. 相似文献
16.
Bio-based bacterial cellulose (BC) epoxy composites were manufactured and their mechanical properties were examined. The BC was initially fabricated from Vietnamese nata de coco by means of alkaline pretreatment followed by solvent exchange. The obtained fibers were dispersed in epoxy resin (EP) by both mechanical stirring and ultrasonic techniques. The resulting blend was used as the matrix for glass-fiber (GF) composite fabrication using a prepreg method followed by multiple hot-press-curing steps. The morphology, mechanical characteristics and mode-I interlaminar fracture toughness of the fabricated composites were investigated. With a 0.3-wt% BC content, the mode-I interlaminar fracture toughness for both crack initiation and crack propagation were improved by 128.8% and 1110%, respectively. The fatigue life was dramatically extended by a factor of 12, relative to the unmodified composite. Scanning electron microscopy images revealed that the BC plays a vital role in increasing the interlaminar fracture toughness of a GF/EP composite via the mechanisms of crack reflection, debonding and fiber-bridging. 相似文献
17.
Sania Akhtar Dipak K. Setua Prajna P. De Sadhan K. De 《Polymer Degradation and Stability》1985,10(4):299-317
Natural rubber vulcanizates undergo severe corrosion when exposed to nitric acid. The nature and extent of damage with increasing degree of corrosion has been assessed by studies on the fall in mechanical properties, such as tensile strength and tear strength, and examination of scanning electron microscopy photomicrographs of the fracture surfaces of tensile and tear samples, both before and after acid treatment. It has been observed that, in the case of inert fillers, which simply dilute the rubber matrix, the filled vulcanizates disintegrate, on acid treatment, more quickly than the unfilled vulcanizates but that, when the filler is reinforcing, this effect is largely overshadowed by polymer-filler interaction which restricts acid corrosion. 相似文献
18.
High strength toughened epoxy nanocomposite based on poly(ether sulfone)‐grafted multi‐walled carbon nanotube 下载免费PDF全文
Hydroxyl terminated poly(ether sulfone) (PES) has been grafted on multi‐walled carbon nanotube (MWCNT). The grafting reaction was confirmed by different characterization techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The extent of the grafting was found to be around 58 wt%. Hybrid nanocomposite of epoxy with the modified MWCNT was also prepared. Effect of grafting on the mechanical, thermal, and viscoelastic properties was studied. Dynamic mechanical studies show an increase in the storage modulus for the nanocomposite prepared using PES‐grafted MWCNT compared with neat epoxy system. PES‐grafted MWCNT–epoxy nanocomposite induces a significant increase in both tensile strength (26%) and fracture toughness (125%) of the epoxy matrix. Field emission scanning electron micrographs of fractured surfaces were examined to understand the toughening mechanism. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
19.
Xiao-Lin Xie Zhong-Zhen Yu Qing-Xin Zhang Gen-Wen Zheng Yiu-Wing Mai 《Journal of polymer science. Part A, Polymer chemistry》2007,45(12):1448-1458
Maleated styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MA) and epoxy monomer, individually or in combination, are used to toughen polyamide 6/glass fiber composites. The epoxy monomer enhanced interaction between polyamide 6 and glass fiber. SEBS-g-MA rubber is uniformly dispersed in polyamide 6 matrix caused by the preferred compatibilizing reaction between the anhydride group of rubber and the amine terminal group of polyamide 6. The addition of epoxy does not affect the fine dispersion of SEBS-g-MA. Polyamide 6/glass fiber binary composites are brittle. The addition of epoxy monomer alone does not change their brittle features. Similarly, in the absence of epoxy monomer, adding 20 wt % of SEBS-g-MA to polyamide 6/glass fiber composites does not greatly increase the tensile ductility. Only when both SEBS-g-MA and epoxy monomer are present in some combination, do the polyamide 6/glass fiber composites show prominent ductile characteristics, such as stress-whitening and necking. This synergistic effect of epoxy monomer and SEBS-g-MA also imparts higher notched impact strengths to the ternary composites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1448–1458, 2007 相似文献
20.
The solid-state light scattering from ABE (acrylonitrile butadiene epoxy) copolymers was studied as a function of rubber content by measuring the intensity distribution of scattered light under Vv polarization conditions. The range of heterogeneity has been quantified by the Debye–Bueche statistical treatment and by comparison with simulated scattering envelopes. The data indicate that below a critical rubber concentration of 20% the rubbery phase precipitates as spherical domains of nearly constant size. Phase inversion occurs at a rubber concentration of 20% and is accompanied by a maximum in polydispersity of the dispersed phase. Beyond this concentration, epoxidic domains are imbedded in a rubber and epoxy matrix. As a result of comparison of Debye–Bueche parameters with simulated values of these, it is concluded that the correlation distance is very sensitive to the presence of a small number of large particles. 相似文献