EPOXY RESIN TOUGHENED BY THERMOPLASTICS

Two kinds of tough ductile heatresisting thermoplastic, namely bisphenol A polysulfone (PSF) and polyethersulfone (PES) were used to toughen thermoset epoxy resin. A systematic study on the relationship between the molecular weight and the terminal group of the thermoplastic modifier and the fracture toughness of the modified resin was carried out. The morphology of PSF modified epoxy resin was surveyed. With the same kind of PSF the structure of the epoxy resin and the toughening effect of PSF was also investigated. The fractography of PSF, particle modified epoxy was examined in detail with SEM. The contribution of every possible energy absorption process has been discussed. Crack pinning mechanism seems to be the most important toughening mechanism for tough ductile thermoplastic PSF particle modified epoxy system.     

一种液晶环氧增韧环氧树脂的研究

环氧树脂具有优异的机械性能 ,耐高温以及良好的加工工艺性 .被广泛用于机械、航天、船舶等领域 .由于环氧树脂固化后断裂延伸率小 ,脆性大 ,使其应用受到了一定的限制 .为此 ,国内外学者对环氧树脂进行了大量的改性研究工作 .用含有“柔性链段”的固化剂固化环氧 ,在交联网络中引入柔性链段[1] ;在环氧基体中加入橡胶弹性体[2 ] 、热塑性树脂[3 ,4] 、液晶聚合物[5,6] 等分散相或用热固性树脂连续贯穿于环氧树脂网络中形成互穿、半互穿网络结构[7] ,以改善环氧树脂的韧性 .本文采用液晶环氧化合物原位复合增韧环氧树脂 ,考察了液晶环氧对环…     

不同软段长度PBT-co-PBS-b-PEG嵌段共聚物的合成与表征

用熔融缩聚法合成了一系列具有不同软段长度的聚对苯二甲酸丁二酯 (PBT) co 聚丁二酸丁二酯(PBS) b 聚乙二醇 (PEG)嵌段共聚物 (PTSG) ,考察了PEG分子量 (Mn(PEG) )及PBS摩尔分数 (MPBS)对材料性能的影响 实验表明 ,随Mn(PEG)增加 ,缩聚反应时间延长 ,所得产物分子量均呈较为对称的单峰分布 ,多分散性指数小于 2 0 硬段序列结构分析显示 ,随MPBS 增加 ,PBT平均序列长度减小 ,而PBS平均序列长度增加 ,二者呈无规分布 .受组成及硬段平均序列长度变化影响 ,材料内部呈微观相分离状态 ,DSC曲线上可分别观察到软、硬段熔点及玻璃化转变温度 ;硬段熔点及结晶度随MPBS升高而降低 ,主要是受其平均序列长度变化及共晶作用所致 .材料断裂延伸率及降解速率均随Mn(PEG)及MPBS增加而增加 ,可见提高软段长度及降低硬段结晶度等均能有效改善共聚物高分子链的柔韧性及亲水性 ,赋予共聚物更好的降解性能 .     

RHEOLOGICAL MODIFICATION OF EPOXY RESINS WITH NANO SILICA PREPARED BY THE SOL-GEL PROCESS*

Nano silica-modified epoxy resins were synthesized by the sol-gel process. The materials have themorphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed aphysical network in the resin and thus influenced the rheological behavior greatly. However, the nano silicadid not show a significant influence on the mechanical properties of the cured resins.     

MODIFICATION OF EPOXY RESINS WITH PHENOLIC HYDROXYL-TERMINATED POLYSILOXANE

Phenolic hydroxyl-terminated polysiloxanes were incorporated into epoxy resins to reducethe internal stress owing to the mismatch in coefficient of thermal expansion (CTE).Polysiloxane-epoxy resin block copolymers were made by a pre-reaction step prior to thecuring. In the cured resin, the domain size of the polysiloxane phase depended on thestructure of the phenolic hydroxyl-terminated polysiloxane. It was found that the modulus ofthe cured resin depended largely on the level of the modifier, while the CTE was affectedgreatly by the structure of the polysiloxane. By means of incorporating a few percent ofmethylphenylsiloxane unit into the polydimethylsiloxane chain, or by introducing morecompatible end-capping groups, the compounds of more effective low stress modifiers weresynthesized.     

MECHANICAL RELAXATION AND INTERMOLECULAR INTERACTION IN EPOXY RESINS/POLY (ETHYLENE OXIDE) BLENDS CURED WITH PHTHALIC ANHYDRIDE

The miscibility of the blend,composed of a bisphenol A epoxy resins (Diglycidyl etherof bisphenol A) (DGEBA) and poly(ethylene oxide) (PEO) and crosslinked by phthalicanhydride (PA) was studied using dynamic mechanical method. Single glass transitiontemperatures intermediate between the two pure components were observed for all blendlevels. The secondary relaxation mechanism should relate to not only diester linkage, butalso hydroxyether structural unit in the system. Fourier transform infrared spectroscopy(FTIR) is applied to study the curing reaction and intermolecular specific interaction of thesystem. The results indicate the PEO participates the crosslinking reaction, accelerates thecuring reaction and make the reaction more perfect. The shifts of the hydroxyl band andcarbonyl band demonstrate the presence of the intermolecular interaction in the curedblend. Moreover, the molecular interaction between the side hydroxyl in the hydroxyetherunits and the ether bond in PEO macromolecules is stronger.     

SPECIAL EFFECT OF ULTRA-FINE RUBBER PARTICLES ON PLASTIC TOUGHENING

According to the present theories of plastic toughening, it is impossible to enhance the toughness, stiffness and/orheat resistance of plastics simultaneously by using rubber. A series of novel nano-rubber particles (UFPR) were introduced,which were prepared through irradiating common rubber lattices and spray drying them. Epoxies toughened with UFPRshowed a much better toughening effect than those with CTBN, and the heat resistance of epoxy was unexpectedly elevated.For polypropylene toughening, UFPR can improve the toughness, stiffness and heat resistance of PP simultaneously. Thesespecial toughening effects overcome the deficiencies in rubber toughening technology and are worth further investigating.     

STUDY ON THE EPOXY RESIN TOUGHENED BY HYDROXY-TERMINATED BUTADIENE-ACRYLONITRILE COPOLYMER

Toughened epoxy resin with excellent properties was obtained by adding organic acid anhydride curing agent and hydroxy-terminated butadiene-acrylonitrile copolymer (HTBN), which is cheaper than CTBN. The anhydride reacts with both epoxy groups on epoxy resin and hydroxyl groups on HTBN. As a result the soft long chains of HTBN and the rigid chain of epoxy resin form one network, giving the resin toughness. Two-phase structure of the toughened resin was observed by SEM and TEM.     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS——POLY (ARYLENE TEREPHTHALATE-CO-BUTYLENE TEREPHTHALATE)

A series of copolyesters based on bis(4-hydroxybutyl) terephthalate, terephthaloyl chloride andvarious aromatic diols (i.e. hydroquinone, chlorohydroquinone, bromohydroquinone or dihydroxybi-phenyl) was prepared. ~1H-NMR studies revealed that the monomer units had microstructures closeto random distribution in the chains. The copolymers showed composition-dependent liquid crystal-line properties as verified by visual observation of stir opalescence, polarizing microscope, DSC andX-ray diffration. The copolyesters with aromatic diol contents over a certain extent (for chloro-hydroquinone m≥0.33) were thermotropic with wide liquid crystalline temperature ranges. Theintroduction of chlorohydroquinone into the copolyesters could gradually destroy the crystallinityof the polymers but retain the liquid crystalline characteristics.     

CRYSTALLIZATION OF BLENDS OF AN ASYMMETRIC POLY（OXYETHYLENE）-b-POLY（OXYBUTYLENE） BLOCK COPOLYMER WITH POLY（OXYBUTYLENE）

An oxyethylene/oxybutylene block copolymer with asymmetric volume fraction (E115B103) was blended with oxybutylene homopolymer (Bh) at different volume fractions of the block (φE). Crystallization behavior of the blends was studied and was compared with that of the blends from a symmetric block copolymer (E114B56). It was found that the crystallization temperature of E115B103/B28 blend is lower than that of the blends from symmetric block copolymer. For the blend with φE= 0.30 breakout crystallization with an Avrami exponent n ≈ 3.0 is observed. At φE = 0.22 the blend exhibits a variable crystallization behavior: confined crystallization with n ≈ 1.0 at lower crystallization temperatures but breakout crystallization at high crystallization temperatures. For the blend with φE = 0.14 and sphere morphology confined crystallization occurs at all crystallization temperatures studied. When compared with the blends from symmetric block copolymer, confined crystallization occurs more easily in the E115B103/B28 blends. The SAXS results agree with the isothermal crystallization kinetics. Deformation of the confined crystalline block is observed in the blend with φE = 0.14 and mixed lamellar and cylinder morphologies in the blend with φE = 0.22.     

功能基化介晶高聚物增韧环氧树脂性能研究——材料断裂面形态结构与力学性能的关系

在系统研究含介晶基团的高聚物ＬＣＥＵＰＰＧ增韧环氧树脂Ｅ ５１／双氰双胺（ｄｉｃｙ）固化体系固化反应活性、反应机制、动态力学行为及冲击性能的基础上,以扫描电镜（ＳＥＭ）为手段,对材料断裂面的形态结构进行了研究,并对体系的形态结构与动态力学行为、冲击性能之间的关系进行了探讨．结果表明,改性后材料断裂面的形态均呈微观两相网络结构,明显不同于未改性体系,正是由于两相网络结构的存在,导致了改性体系的冲击强度大幅度提高．     

透闪石/环氧树脂复合材料性能研究

环氧树脂是一类综合性能较好的热固性树脂,为了扩大其应用范围．通常的办法是采用纤维进行增强．目前,许多研究工作者采用纳米粒子、粘土对其进行改性,所用的粘土包括各种有机蒙脱土、高岭土等,作者曾采用海泡石对环氧树脂进行改性,使环氧树脂的各项力学性能得以提高,然而采用透闪石对环氧树脂进行改性,还鲜见相关报道．透闪石是一种带有极性基团的天然矿物,     

STUDIES ON THE OXIDATION AND GRAFT COPOLYMERIZATION OF POLY(ETHER-URETHANE)

A new method of graft copolymerization of acrylamide (AAM) on poly(ether-urethane) (PEU) which was prepared from poly(tetramethylene ether) glycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI) and ethylene diamine or butanediol extender was investigated. Hydroperoxide group was first introduced onto the surface of PEU through photo-oxidation in the presence of hydrogen peroxide, then it was reacted with ferrous ion or N,N-dimethyl toluidine (DMT) to initiate AAM graft copolymerization on PEU surface. The graft reaction could be carried out effectively at low temperature. The formation of graft copolymer has been verified by its water absorption % and the scanning electron microscopy photographs. Some model compounds of PEU soft segment and hard segment were synthesized in order to clarify the site of graft reaction. The results of oxida-tion and graft copolymerization of model compounds showed that this graft copolymerization possesses higher selectivity, and it takes place predominately at the polyether segments, because the ether linkage in soft segment is very sensitive to oxidation and can form hydroperoxide easily. Thus, the grafting site appears to be at α-carbon of the ether linkage.     

STUDY ON LIQUID CRYSTALLINITY OF POLY(N-VINYLCARBAZOLE)

The liquid crystallinity of poly(N-vinylcarbazole) was studied by using powder X-ray diffraction, polarized opticalmicroscopy, and differential scanning calorimetry. The results show that the lower molecular weight fractions of this polymerdo not form a liquid crystalline phase, while the samples of sufficiently high molecular weight do form a mesophase attemperatures above the glass transition. The lowest value of the degree of polymerization for PVK to form a stable liquidcrystalline phase was found to be in the range of 150 to 200, significantly higher than the value of 50 for most conventionalside chain liquid crystaline polymers.     

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.     

SYNTHESES OF POLYSTYRENE RESINS CONTAINING POLYETHER OLIGOMERS AND THEIR EXTRACTION FOR GOLD (Ⅲ)*

Three polystyrene resins containing polyether oligomers as extractants were synthesized andtheir extraction properties were studied. Gold (III) ion could be extracted rapidly by the resins(T_(1/2),相似文献   

螺环原酸酯改性环氧树脂的研究

合成了一个新的螺环原酸酯单体,即带有螺环原酸酯结构单元的环氧树脂（Ｅ ５４）．用该单体对环氧树脂进行改性,可以减少残留在树脂基体中的环氧基团,这说明该单体与环氧树脂之间发生了共聚固化反应．基体的Ｔｇ和热稳定性随预聚物加入量的增加而降低,但改性环氧树脂的粘接强度则随预聚物的加入量的增加而增加．对上述试验观察到的现象进行了讨论,并测试了改性环氧树脂基体的力学性能．     

CLOUD POINT CURVES OF POLY(ETHYLENE GLYCOL)/POLY(PROPYLENE GLYCOL) MIXTURES AND THEIR THERMODYNAMIC EXPLANATION

In the study of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) mixtures not only a bimodal shape but also a reverse trend of the dependence on molecular weight of the cloud point curves were observed.This trend indicates that the miscibility of the studied mixtures decreases as the molecular weight of one component decreases. The excess volumes of the mixtures show that the interaction parameter between two components decreases at first and increases after passing a minimum as the concentration of one component increases. This supports the explanation of Koningsveld on the bimodal shape of cloud point curves. Based on a binary interaction model a formula was derived revealing that the interaction between PPG and the end group of PEG and the hydrogen bonding interaction between ether and hydroxy end group inner or inter PEG molecules are not favorable for mixing. The latter interaction is an "attractive" force in PEG molecules. The two interactions are responsible for the observed abnormal dependence.     

IMMOBILIZATION OF POTENTIALLY BIOACTIVE MOIETIES ONTO POLYETHER WITH POLY(ETHYLENE GLYCOL)-SULFONATE SPACER

A new reactive graft copolymer, poly(tetramthylene glycol) - graft-w-propyl sodiumsulfonate-poly(ethylene glycol) (PTMG-g-PEG-CH_2CH_2CH_2SO_3~-Na~+), was synthesizedby the cationic polymerization of a-w-bifunctional PEG macromonomer (O?CH_2—PEG——CH_2 CH_2 CH_2 SO_3 Na) and THF. The obtained copolymer exhibits the expected structureas indicated by the result of characterization. Two amino acids (L-arginine, L-tyrosine)were covalently attached to the copolymer after converting the sulfonate group to sulfonylchloride. So the new reactive graft copolymer (PTMG-g-PEG-CH_2CH_2CH_2SO_3~-Na~+) isexpected to be very useful in attachment of potentially bioactive moieties to polymer viaa hydrophilic PEG spacer.     

PROPERTIES OF DILUTE SOLUTIONS OF HYDROPHOBICALLY MODIFIED POLY (4-VINYL PYRIDINE) (POLYSOAPS)

Hydrophobically modified poly(4-vinyl pyridines) by alkyl bromides arekinds of polysoap similar to the surfactant. Properties of dilute solutions were studiedthrough the viscosity measurements in pure water and NaCl solutions. In aqueous solu-tions of polysoaps hydrophobic interaction can be attributed to aggregation of hydrophobicgroups of the polysoap main chains. The hydrophobic groups of polysoap can aggregate toform hydrophobic microdomains (micelles) in aqueous solution. This is a compact confor-mation. The formation of such microdomains is a process of dynamic equilibrium.