外电场对CER/TMPTMA IPNs形成过程的在线监测

利用自制装置研究了脂环族环氧树脂(CER)/三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)互穿网络聚合物(IPNs)的固化过程.通过在线测试CER/TMPTMA体系固化过程中的交流电阻和电容,发现电阻和电容的变化反映出CER/TMPTMA体系的固化过程是一个分步IPNs的形成过程,而且电阻和电容变化趋势与体系的粘度、离子浓度以及偶极子的数量息息相关.利用自制电极和装置可以远距离在线监测热固性树脂的固化过程,在外磁场干扰下,利用CER/TMPTMA固化体系的电阻波动可以表征体系的固化反应情况.     

Morphologies and applied properties of free radical/cationic UV‐cured CPUA/TMPTMA/CER composite films

A UV‐cured composite film was prepared by free free‐radical photopolymerization from a blend containing oligomer cycloaliphatic polyurethane acrylate (CPUA) and reactive diluent trimethylolpropane trimethaacrylate (TMPTMA) with the same weight (coded as UT) in the presence of free free‐radical photoinitiator Irgacure 754. It was proved to be a homogeneous system featuring only one phase by means of scanning electron microscopy (SEM). Cycloaliphatic epoxy resin (CER) was introduced to enhance mechanical properties of the UV‐cured UT composite film in the presence of cationic photoinitiator Irgacure 250, and a series of UV‐cured CPUA/TMPTMA/CER composite films with different component ratios were prepared by free radical/cationic hybrid UV UV‐curing technique. Results of conversion curves, SEM, and Fourier‐ transform infrared spectroscopy illustrated that UT was cured faster than CER, leading to dynamically asymmetric photopolymerization‐induced phase ‐separation behaviors. The thermal and mechanical properties were evaluated via thermal degradation analysis, dynamic mechanical analysis, and stress–strain curves. Surface properties such as pencil hardness, pendulum hardness, shrinkage rate, contact angle, flexibility, and glossiness were also studied. All these measurements revealed that component ratios, intermolecular attractions, photopolymerization velocities, and viscosities had remarkably influenced on the morphologies and applied properties of UV‐cured composite films, and interpenetrating polymer network films had better comprehensive performances than other UV‐cured composite films with different microstructures. POLYM. COMPOS., 36:1177–1185, 2015. © 2014 Society of Plastics Engineers     

环氧树脂/三羟甲基丙烷三甲基丙烯酸酯互穿网络聚合物的微观结构和电性能研究

采用新型脂环族环氧树脂（CER）、甲基六氢邻苯二甲酸酐（MeHHPA）和三羟甲基丙烷三甲基丙烯酸酯（TMPTMA）作为基体树脂制备了一种崭新的互穿网络聚合物。由于TMPTMA的自由基聚合反应先于CER和MeHHPA的阳离子聚合反应,得到了一种分步互穿网络聚合物,最终分步互穿网络聚合物没有出现明显微观相分离现象。着重考察了TMPTMA含量对互穿网络聚合物电性能的影响。结果表明,CER/TMPTMA互穿网络聚合物在不同温度下的交流电阻与体系的组成和微观结构有关。随着TMPTMA含量的增加,CER/TMPTMA互穿网络聚合物的击穿强度和形态参数增大,互穿网络聚合物的均匀度逐渐增加,击穿机理趋于一致。     

Morphology and thermal and dielectric behavior of cycloaliphatic epoxy/trimethacrylate interpenetrating polymer networks for vacuum‐pressure‐impregnation electrical insulation

Vacuum pressure impregnation has been known as the most advanced impregnation technology that has ever been developed for large and medium high‐voltage electric machines and apparatuses. We developed one new type of vacuum‐pressure‐impregnation resin with excellent properties by means of a novel approach based on in situ sequential interpenetrating polymer networks resulting from the curing of trimethacrylate monomer [trimethylol‐1,1,1‐propane trimethacrylate (TMPTMA)] and cycloaliphatic epoxy resin (CER). In this study, the influence of the concentrations of the components and their microstructures on their thermal and dielectric behaviors were investigated for the cured CER/TMPTMA systems via atomic force microscopy, dynamic mechanical analysis, thermogravimetric analysis, and dielectric analysis. The investigation results show that the addition of TMPTMA to the CER–anhydride system resulted in the formation of a uniform and compact microstructure in the cured epoxy system. This led the cured CER/TMPTMA systems to show much higher moduli in comparison with the pure CER–anhydride system. The thermogravimetric analysis results show that there existed a decreasing tendency in the maximum thermal decomposition rates of the cured CER/TMPTMA systems, which implies that the thermal stability properties improved to some extent. The dielectric analysis results show that the cured CER/TMPTMA systems displayed quite different dielectric behaviors in the wide frequency range 0.01 Hz–1 MHz and in the wide temperature range 27–250°C compared with the cured CER–anhydride system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase separation in the polyurethane/poly(2‐hydroxyethyl methacrylate) semi‐interpenetrating polymer networks synthesized by different ways

The thermal, dynamic mechanical analysis, morphology and mechanical properties of semi‐interpenetrating polymer networks based on crosslinked polyurethane (PU) and poly(2‐hydroxyethyl methacrylate) (PHEMA) synthesized by photopolymerization and by thermopolymerization have been investigated. The thermal analysis has evidenced the two glass temperature transitions in the semi‐IPNs and this is confirmed by the thermodynamic miscibility investigation of the systems. The Dynamic Mechanical Analysis spectra have shown that the phase separation is more significant in the thermopolymerized semi‐IPNs: the tan δ peaks of constituent polymers are more distinct and the minimum between the two peaks is deeper. The calculated segregation degree values of semi‐IPN's components are significantly higher for thermopolymerized semi‐IPNs, thereby the process of phase separation in the thermopolymerized semi‐IPNs is more developed. The structures of two series of samples investigated by SEM are completely different. The mechanical properties reflect these changes in structure of semi‐IPNs with increasing amount of PHEMA and with the changing of the method of synthesis. The results suggest that the studied semi‐IPNs are two‐phase systems with incomplete phase separation. The semi‐IPN samples with early stage of phase separation demonstrate higher mechanical characteristics. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Recent studies on interpenetrating polymer networks

Recent investigations on interpenetrating polymer networks (IPNs) have included two component IPNs from polyurethanes and poly(methacrylates) and two component IPNs from polyurethanes and epoxies. All the IPNs were prepared by the simultaneous polymerization technique (SIN-IPNs). Two types of IPNs, polyurethane-poly(methyl methacrylate) (PU/PMMA) and polyurethane-poly(methyl methacrylate-methacrylic acid) (PU/PMMA-MAA) were prepared. Improved phase miscibility and decreasing extent of phase separation was observed in both types of IPNs with increasing the NCO/OH ratio, decreasing molecular weight of the polyol in the PU and introduction of charge groups. A comparison was made between full-IPNs, pseudo-IPNs, graft copolymers and related homopolymers from polyurethanes and epoxies. Increased compatibility in full-IPNs and graft copolymers was observed by means of DSC, SEM and was also further substantiated by a shift toward single T_gs as determined by dynamic mechanical spectroscopy. The introduction of opposite charge groups in two-component IPNs from polyurethanes and epoxies led to improved compatibility (no phase separation) and enhanced mechanical properties.     

Filler effect on formation and properties of interpenetrating polymer networks based on polyurethane and polyesteracrylate

The formation processes of unfilled and filled interpenetrating polymer networks (IPNs) and some of their physico-mechanical properties have been investigated. The IPN formation kinetics and the constituent network curing rates determine the rate and degree of microphase separation. This in turn determines the boundary layer composition and structure. Introduction of filler into the IPN during formation affects greatly the crosslinking reaction and the microphase segregation of homopolymers. It has been shown that the degree of phase segregation in filled IPNs differs from that in unfilled ones. All the fillers were found to shorten the time of internal stress appearance and to increase its value for IPNs with predominantly high-modulus component content. Some filled IPNs were shown to have greater thermodynamic stability than unfilled ones.     

Dependence of viscoelastic properties on segregation degree of components in interpenetrating polymer networks

The temperature dependences of elastic moduli, loss moduli, and mechanical loss angle tangent were investigated for the interpenetrating polymer networks: polyurethane–polyurethane acrylate by the method of dynamic mechanical spectroscopy (DMS). The segregation degree of components due to phase separation have been calculated from the parameters of relaxation maxima. An essential change was found in the segregation degree of components with the curing sequence of individual networks being changed. It was shown that, with the conditions and sequence of IPN formation changed, the phase separation degree can be fixed at a particular stage, i.e., the structures with a different segregation degree of components are obtainable. For the IPNs under investigation the variation of elastic moduli of the composites proved possible by fixing the separation degree of components.     

网络间的化学键效应对聚氨酯／乙烯基酯树脂IPN形态与力学性能的影响

本文通过环氧树脂（Ｅ—５１）与甲基丙烯酸合成了大分子链中含有羟基或羟基被封闭的乙烯基酯树脂（分别称为ＶＥＲＨ与ＶＥＲＡ），并用它们与聚氨酯（ＰＵ）合成了不同组成的ＰＵ／ＶＥＲ互穿网络（ＩＰＮ），用扫描电子显微镜考察了这些ＩＰＮ材料的形态，发现网络间的化学键对ＩＰＮ的形态有很大影响，它们抑制了两个网络间的分相以及ＰＵ硬段局部有序结构的形成。对这些材料的力学性能进行了测定，结果表明网络间的化学键能较大幅度地提高材料的力学性能。     

顺丁橡胶/生物基酚醛树脂复合材料的研究

利用生物基材料木质素代替部分苯酚合成生物基酚醛树脂,并将其应用到顺丁橡胶中;采用同步法制备顺丁橡胶/生物基酚醛树脂复合材料(BR/LPF),并对其形态结构、机械性能及热稳定性等进行了研究。SEM及DSC结果表明,BR/LPF形成了互穿网络结构,两相出现相分离,相畴尺寸较大。机械性能实验结果表明,BR与LPF的比例对复合材料的拉伸强度、撕裂强度、硬度、拉断伸长率等影响较大,其中以BR/LPF(80/20)复合材料综合性能最佳;LPF的构成组分对机械性能也有较大影响。TGA实验表明,BR/LPF复合材料具有较好的热稳定性,加入LPF可提高复合材料的降解温度(T50%)。     

Morphology control in reaction-induced phase-separated polymeric systems

In this article the morphology control of poly(ethyl acrylate)/poly(methyl methacrylate) (PMMA) semi-interpenetrating polymer networks (IPNs) has been attempted either by changing reaction temperature or by adding the third component at the initial stage of phase separation. The morphological variation was followed via dynamic mechanical behavior and electron microscopy. It was found that raising the polymerization temperature of PMMA or adding linear PMMA to the initial mixture facilitates phase separation during the semi-IPNs formation process. However, the phase separation was further induced by annealing, which indicates that kinetically controlled morphology was not at its equilibrium state. © 1995 John Wiley & Sons, Inc.     

Polymerization induced phase separation in poly(ether imide)-modified epoxy resin cured with imidazole

This paper studies the phase separation in poly(ether imide) (PEI) modified epoxy resin using imidazole (C₁₁Z-CNS) as epoxy hardener to control its morphology. The sponge-like phase structures were founded at higher PEI concentration (10-25 phr), while homogeneous structures are formed at low PEI concentration (5 phr). The effects of PEI concentration on curing kinetics and phase structures were studied by differential scanning calorimeters (DSC) and scanning electron microscopy (SEM). It is shown that although the addition of PEI does not change the curing mechanism, the separated morphology becomes finer at high PEI concentration. The curing rate and conversion decrease with the increase of the content of PEI. The chain growth polymerization of these systems caused an early gelation (conversion <10%) and early freezing of morphologies. The evolution of phase separation in the early stage was monitored by synchrotron radiation small angle X-ray scattering (SR-SAXS) and transmission electronic microscopy (TEM). It is suggested that the formation of sponge-like phase structure could be attributed to the strong viscoelastic effects in the early stage of phase separation.     

Synthesis and characterization of high performance,transparent interpenetrating polymer networks with polyurethane and poly(methyl methacrylate)

Transparent, interpenetrating polymer network (IPN) materials were synthesized using polyurethane (PU) and poly(methyl methacrylate) (PMMA). PMMA contributed to the transparency and rigidity necessary for use in impact‐resistant applications, whereas PU contributed to toughness. Several factors affecting the physical properties, such as the ratio of PU to PMMA, curing profile, inclusion of different isocyanates for the PU phase, and use of an inhibitor in the PMMA phase, were investigated. Full‐IPNs were synthesized so that the two polymer networks would remain entangled with one another, and domain sizes of each system were reduced, mitigating phase separation. Both simultaneous IPNs, polymerization of monomers occurring at the same time, and sequential IPNs, polymerization of monomers occurring at different temperatures, were synthesized for studying the reaction kinetics and final morphologies. The phase morphology and the final thermal and mechanical properties of the IPNs prepared were evaluated. Findings suggest that samples containing ～80 wt% PMMA, 1,6‐diisocyanatohexane 99+% (DCH), and an inhibitor with the MMA monomer created favorable results in the thermo‐mechanical and optical properties. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Effect of crosslinking density on the physical properties of interpenetrating polymer networks of polyurethane and 2-hydroxyethyl methacrylate-teminated polyurethane

Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate-terminated polyurethane (HPU) and polyurethane (PU) with different crosslinking densities of the PU network were prepared by simultaneous solution polymerization. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) show that compatibility of component polymers in IPN formation depends on the crosslinking density of the PU network. Physical properties such as density and water absorption rely on the subtle balance between the degree of phase separation and the crosslinking density of the PU network. In spite of the occurrence of phase separation, the tensile moduli and tensile strength of the IPNs increase with the crosslinking density of the PU network. Morphological observation by scanning electron microscopy revealed different fracture surfaces between the compatible and incompatible IPNs. Surface characteristics of the IPNs, indicated as hydrogen bonding index and hard-to-soft segment ratio, are altered considerably by varying surface morphologies. Improved blood compatibility of IPN membranes is due to the variation of the hydrophilic and hydrophobic domain distribution.     

固化动力学对PU/VER同步互穿网络聚合物性能的影响

互穿网络聚合物(IPNs)是一种特殊的交联聚合物合金.本研究以聚氨酯(PU)和乙烯基酯(VER)预聚物为原料,在室温下合成了互穿网络聚合物.采用傅立叶红外光谱法跟踪了网络形成的动力学过程并进行半定量分析,研究了固化体系对互穿纲络聚合物的摩擦学性能、力学性能及光学性能等的影响.结果显示,两种预聚物在固化过程中虽遵循不同的聚合机理,却相互影响制约.通过改变引发剂和催化剂的配比得到的样品显示出不同特性.当VER引发剂的用量为0.75%,PU催化剂的用量为0.6%时,两网络可基本实现同步互穿;同步互穿网络聚合物显示出良好的耐磨性,在实验条件下涂层寿命可达28.81 min,且力学性能优异,在可见光波长范围内具有良好的透光性, 450 nm处的透光率可达85%.     

Effect of co-promoter and secondary monomer on shrinkage control of unsaturated polyester (UP)/styrene (St)/low-profile additive (LPA) systems cured at low temperatures

The shrinkage of unsaturated polyester (UP)/styrene (St) resins cured at low temperatures can be reduced by the presence of low-profile additives (LPAs). It is believed that the reaction-induced phase separation and the polymerization shrinkage in both the LPA-rich and UP-rich phases result in the formation of microvoids, which partially compensates the resin shrinkage. The relative reaction rate in the two phases plays an important role in shrinkage control. In this study, secondary monomers [such as divinylbenzene (DVB) and trimethylopropane trimethacrylate (TMPTMA)] and a co-promoter, 2,4-pentandione (2,4-P), were added into the UP/St/LPA resin systems to investigate their effect on the shrinkage control of resins cured at low temperatures. Dilatometery results showed that the addition of both TMPTMA and 2,4-P resulted in an earlier volume expansion during curing and better shrinkage control. The phase separation, reaction kinetics, and viscosity changes in the LPA-rich and UP-rich phases during curing were also investigated. The results confirmed that the increased reaction rate in the LPA-rich phase led to an earlier formation of microvoids and, consequently, less volume shrinkage of the cured resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 738–749, 2001     

Sequential interpenetrating polymer network based on styrene butadiene rubber and polyalkyl methacrylates

A series of sequential interpenetrating polymer network (IPNs) based on styrene butadiene rubber (SBR) and polyalkyl (methyl, ethyl, and butyl) methacrylates have been prepared by using tetraethylene glycol dimethacrylate as crosslinker. The IPNs were characterized by infrared spectrophotometer, dynamic mechanical analyzer, thermogravimetric analyzer, and swelling study. IPNs have exhibited higher tensile properties compared with pure SBR. IPNs based on PMMA have shown higher tensile strength compared with others. Dynamic mechanical analysis has shown that the IPNs have superior dynamic properties than SBR. Because of IPN formation, tan δ peak shifted inward between SBR and acrylates. Although the magnitude of tan δ decreased, the peaks were broadened because of micro heterogeneous phase separation. At higher concentration of methacrylate, splitting in tan δ peak was noticed because of phase separation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1120–1126, 2007     

Laboratory investigation of cracking resistance performance of the cold-mixed epoxy resin

Cold-mix epoxy resin (CER) is an excellent binder material but with weak crack resistance and brittle failure risk. Therefore, it is of significance to find a feasible parameter to constrain the failure potential. To this end, the dynamic mechanical test, tensile test, volume shrinkage test, fracture test, and scanning electron microscopy (SEM) were used to analyze and evaluate mechanical properties, curing shrinkage, and fracture toughness of the CER. Subsequently, the bivariate correlation analysis was used to feature the relationship among different indicators. The results indicated that the amount of curing agent has a significant influence on the tensile strength, elongation at break, volume shrinkage, fracture toughness, and plastic radius of CER. Meanwhile, there is a close correlation between tensile strength, elongation at break, and fracture toughness. Fracture toughness can be used as an evaluation index to represent the crack resistance of CER, and tensile test can be used as a confirmatory parameter. However, the volume shrinkage of CER cannot be ignored. Small voids distributed on the fracture surface of the CER can increase the toughness and then improve the crack resistance of the CER through SEM analysis.     

Cure kinetics and physical properties of dicyanate/polyetherimide semi‐IPNs

The curing behavior and physical properties of dicyanate/polyetherimide (PEI) semi‐interpenetrating polymer network (IPN) systems were investigated. Differential scanning calorimetry (DSC) was used to study the curing behavior of the dicyanate/PEI semi‐IPN systems. The curing rate of the semi‐IPN system decreased as the PEI content increased. An autocatalytic reaction mechanism can describe well the curing kinetics of the semi‐IPN systems. The reaction kinetic parameters were determined by fitting DSC conversion data to the kinetic equation. The glass transition temperature of the semi‐IPNs decreased with increasing PEI content. Two glass transitions due to phase‐separated morphology were observed for the semi‐IPN containing over 15 phr (parts per hundred parts of dicyanate resin) PEI. The thermal stability and dynamic mechanical properties of the semi‐IPNs were measured by thermal analysis.     

Reaction kinetics of irradiation- prepolymerized methyl methacrylate-polyurethane interpenetrating polymer networks by FTIR

The reaction kinetics of irradiation-prepolymerized MMA-PU (polyether) IPNs have been studied by FTIR. The results indicate that the polymerization of each component in the IPN follows its normal distinct reaction mechanism with no mutual interference. Increasing the concentration of TMPTMA (crosslinking agent of PMMA) increased the formation rate of PMMA, while the formation rate of PU networks remained almost the same. Increasing the concentration of TMP (crosslinking agent of PU) increased the formation rate of PU, while the formation rate of PMMA networks decreased. The formation rate of PU was obviously faster than that of PMMA. A theory for the cage effect of the PU network has been proposed.