热固性环氧树脂形状记忆效应研究

将新型的高分子固化剂与环氧树脂(EP)进行共混,经适度交联固化后制备出一种具有较低玻璃化转变温度(Tg)的无定型EP体系,并对该EP固化体系的力学性能、形状记忆特性和动态力学性能等进行了研究。结果表明:适度交联固化的EP体系具有良好的形状记忆特性,固化剂用量是影响该形状记忆体系综合性能的主要因素;其最大形变恢复率均为100%,形变恢复速率基本上随固化剂用量增加而增大,最大形变恢复速率为0.023 s-1;形变固定率随固化剂用量增加而减小,当w(固化剂)=37.5%或54.5%时,形变固定率为100%或96%。     

含氟形状记忆环氧树脂体系的制备与性能

将氢化环氧树脂(AL-3040)和自制的含氟环氧树脂按不同的物质的量比共混,以聚丙二醇二缩水甘油醚(XY-207)为环氧稀释剂、1,8-薄荷烷二胺(MDA)为固化剂,完全固化之后制备出一种新型的含氟形状记忆环氧树脂体系,并表征了其分子结构、含氟环氧树脂含量对固化体系储能模量和形状记忆性能的影响,测试了体系表面和冲击断面含氟量以及冲击力学性能。研究结果表明:增大体系含氟环氧树脂含量时,固化体系的交联度增大;固化体系的储能模量随含氟环氧树脂含量的增加而增大;该形状记忆含氟环氧树脂体系具有良好的形状记忆性能,形变完全的时间随体系含氟环氧树脂含量的增加而缩短。     

Modified shape memory epoxy resin composites by blending activity polyurethane

A series of modified shape‐memory epoxy resin composites were prepared by blending activity polyurethane (APU). Fourier transform infrared spectroscopy (FTIR), tensile tests, scanning electron microscope (SEM), dynamic mechanical analysis (DMA), and fold‐deploy shape memory tests were used to characterize the structure, mechanical, morphology, thermodynamics, and shape memory performance of these materials. FTIR results suggest that APU has been introduced into the resin matrix resin. Tensile test results show that the addition of appropriate APU can increase the elongation at break significantly, compared with neat epoxy. SEM results indicate that the fracture mechanism has changed from brittle to ductile, suggesting that the brittleness of the material has been overcome. DMA results show that modified materials have lower glass transition temperature (T_g) and lower cross‐linking density for shape memory function. Furthermore, the fold‐deploy shape memory tests prove that the materials possess excellent shape memory properties. They can be deformed into different shapes and recover their original shapes fully within 2 min at T_g, while they are hardly affected by ninefold‐deploy cycles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Bio-based elastomeric hyperbranched polyurethanes for shape memory application

The bio-based shape memory hyperbranched polyurethanes (HBPUs) have attracted tremendous attention both from academic and industrial researchers due to their strong potential in biomedical and other advanced applications. In the present investigation HBPUs have been synthesized from poly(??-caprolactone)diol as a macroglycol, butanediol as a chain extender, triethanolamine as a branch generating moiety, monoglyceride of Mesua ferrea L. seed oil as a bio-based chain extender, at different percentages and toluene diisocyanate by a two step one pot A₂?+?B₃ approach. The structure of the synthesized hyperbranched polyurethane was characterized by FTIR, ^IH NMR, XRD and SEM studies. ¹H NMR study indicates the formation of highly branched structure with degree of branching 0.93 for polyurethane with 5?wt% monoglyceride. TGA results indicated the increment of thermal stability from 185 to 240?°C with the increase of monoglyceride content from (0?C15) wt% for the HBPUs. The shape memory effect of the hyperbranched polyurethane increased with the increase of monoglyceride in the polymer. However, mechanical properties like tensile strength and elongation at break decreased from 19.31 to 11.48?MPa and 835 to 497%, respectively, with the increase in amount of bio-based component. Excellent impact strength and very good chemical resistance were also observed for the hyperbranched polymers. The studied bio-based HBPUs exhibit excellent shape fixity (95?C99)% as well as shape recovery 100%. Thus, the studied HBPUs have the potential to be used as advanced shape memory materials.     

Modeling attempt of shape memory performance of epoxy resin with experimental methods

Epoxy resin samples with low cross-linking density were prepared, and their shape recovery rate and glass transition were studied. The results showed that the shape fixity ratio was over 99 % for all of the samples. Without constraint, the final recovery ratio was approximate to 100 % for all of the samples. The temperature with rapid recovery rate for different samples changed in accordance with T _g. Under a constant temperature, the folding angle for the samples of EP80 decreased with the increase in time rapidly, at first, and then tended to level off. Curves can be fitted with the formula of $ y + A_{0} = A/(1 + \exp ((t - t_{0} )/\tau )) $ with R ² higher than 99.9 %. The fitting results demonstrated that the value of τ decreased from 15.1 to 6.39 when the temperature increased from 88 to 98 °C for EP80. The recovery rate decreased a little by extending the holding time from 10 to 60 s. By keeping the testing temperature constant, glass transition temperature (T _g) decreased with the increase in curing agents, and the value of τ reduced with the decrease in T _g. Usually, when temperature was close to T _g, segments of macromolecules were idle to move, and then, the relaxation process, τ, was lengthened and the shape recovery rate decreased accordingly. In a word, τ showed the similar change rules with that of relaxation process of polymers; therefore, the shape recovering process could be predicted with the model of relaxation time and modulus according to relaxation formulas.     

溴化马来松香环氧树脂的制备及阻燃性

以马来松香和液溴为原料,合成了溴化马来松香;再与环氧氯丙烷发生酯化反应、闭环反应,合成了溴化马来松香环氧树脂。结果表明,在适宜的条件下,合成的环氧树脂的环氧值为0.30 mol·（100 g）^-1。 用红外光谱（FT-IR）、核磁共振谱（¹H NMR）和元素分析法对产物进行了表征。采用固化剂4,4′–二氨基二苯甲烷（DDM）对产物进行了固化。实验证明,溴化马来松香环氧树脂固化物具有较好的阻燃性。     

松香基环氧树脂的合成及性能研究

通过丙烯酸松香(AR)分别与1,4-丁二醇二缩水甘油醚(BDGE)、1,6-己二醇二缩水甘油醚(HDGE)酯化反应合成出松香基环氧树脂预聚体ARBDGE和ARHDGE,丙烯酸松香分别与二乙烯三胺(DETA)、四乙烯五胺(TEPA)酰胺化反应合成出松香基聚酰胺固化剂ARDETA和ARTEPA,测试了理论配比下反应生成固化物的玻璃化转变温度(Tg)及性能;结果表明,松香基固化物硬度中等、划格实验≤3级、T-弯均为0级、耐冲击性能≥5.88 J,耐化学腐蚀合格,紫外加速老化30 d无任何变化。     

Progress in shape memory epoxy resins

This review analyses the progress in the field of shape memory epoxy resins (SMEPs). Partial crystallisation and vitrification are the basis of shape memory effect in SMEPs. Several synthetic approaches for SMEPs, their composites and foams have been reviewed. Strategically incorporated thermally reversible segments induce the shape memory effect in epoxy resins. By varying the nature and concentration of shape memory segments, wide range of shape memory properties and transition temperatures (shape memory temperatures) can be achieved. Triple shape memory, self-healability and electroactive capability are some of the additional features that can be created in SMEPs. Among the thermoset resins, shape memory epoxies are the most attractive systems because of the ease of processability, composite forming properties and dimensional stability. Shape memory epoxy polymers that can be processed into elastic memory composites are candidate materials in the processing of many smart engineering systems. In this background, a review consolidating the progress in SMEP has contemporary relevance. The present article takes a stock of the trend in SMEP with a view to assess the direction of future initiatives in this area. It is concluded that there is tremendous scope for research leading to technological evolution in the field of SMEP.     

甲基丙烯酸改性环氧树脂改进环氧胶膜性能研究

甲基丙烯酸(MAA)和环氧树脂(EP)进行反应后,添加偶氮二异丁腈(AIBN)和丙烯酸异辛酯,合成的含有丙烯酸树脂链段的环氧树脂作为增韧剂,制备成环氧胶膜。改性后的环氧树脂胶膜剪切强度及剥离强度明显提高,DSC测试显示体系的耐热性能损失不大,用红外光谱分析了固化过程及其改性过程中的反应情况。结果表明,改性后的EP制备出的树脂固化物具有良好的力学及耐热性能。     

Self‐synthesized epoxy terminated polydimethylsiloxane with various molecular weights toughening epoxy resin

Polydimethylsiloxane terminated by epoxy group (EP‐PDMS) with various molecular weight ( ) were synthesized by 1,3‐bis[3‐(2,3‐epoxypropoxy)‐propyl]‐1,1,3,3‐tetramethyldisiloxane (DOTMDS) and dimethylcyclosiloxane (D_n). The epoxy value measured by potentiometric titration, were 0.161, 0.092, 0.065, 0.044 mol/100 g, and the (calculated from epoxy value) 1,242, 2,174, 3,077, 4,545 g/mol, respectively (corresponding to EP‐PDMS1, 2, 3, 4). With the increasing ratio of D_n/DOTMDS, we can see the increase of and the decrease of epoxy group content according to FTIR result. Then these EP‐PDMS were used to improve the toughness of the epoxy resin (diglycidyl ether of bisphenol A, DGEBA). Mechanical tests showed that, the impact strength of the epoxy resin was improved by EP‐PDMS. The toughening effect was decreased when EP‐PDMS with relative higher was used. This was ascribed to that the EP‐PDMS with high was easier to agglomerate, and the active group was easier to be embedded which in turn resulted in lower toughening efficiency. This was also confirmed by scanning electron microscopy results. J. VINYL ADDIT. TECHNOL., 24:268–274, 2018. © 2016 Society of Plastics Engineers     

High‐performance biobased epoxy derived from rosin

Great achievements have been made in the research of biobased thermoplastic polymers, but the progress concerning thermosetting resins has been minor. In particular, research on high‐performance thermosetting polymers from renewable feedstock has not been reported elsewhere. A novel biobased epoxy was synthesized from a rosin acid. Its chemical structure was confirmed using ¹H NMR, ¹³C NMR and Fourier transform infrared spectroscopy. The results indicated that the rosin‐based epoxy possessed high glass transition temperature (T_g = 153.8 °C), high storage modulus at room temperature (G′ = 2.4 GPa) and good thermal stability. A rosin‐based epoxy with excellent properties was achieved. The results suggest it is possible to develop high‐performance thermosetting resins from renewable resources. Copyright © 2010 Society of Chemical Industry     

Characterization of viscoelastic behavior of shape memory epoxy systems

Viscoelastic behavior has a remarkable impact on the functional realization of shape memory polymers and their composites. Our previous work reported that a series of shape memory epoxies with varied curing agents and contents were synthesized and exhibited higher shape fixture and recovery rates. The viscoelastic behavior of the materials at different temperatures is experimentally investigated in this study. Stress–strain hysteresis under uniaxial tension, stress relaxation, and creep tests are performed. The energy dissipation factor and residual strain factor as functions of temperatures are presented in the basis of stress–strain hysteresis tests. Moreover, the effects of test temperature, curing‐agent type, and content on the viscoelastic behavior of these materials are discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

UV curable micro-structured shape memory epoxy with tunable performance

Micro-structured shape memory polymer (SMP) surfaces are indispensable in various applications. Epoxy polymer emerged as an ideal candidate for SMP surfaces due to its low curing shrinkage and superior thermo-mechanical properties. In this study, we develop a UV curable epoxy system with tunable glass transition temperature and superior shape memory performance. The glass transition temperatures can widely range from 49 to 164°C by simply tuning the ratio of two comonomers. All samples possess excellent shape fixity, shape recovery ratios, and cycling stability. The synergy of the moldable liquid epoxy precursors and the spatiotemporal UV light allows shape memory epoxy with both surface microstructures and complex macro-geometries. We anticipate this UV curable epoxy will expand the scopes of surface shape memory applications.     

Bio-based flexible polyurethane foam synthesized from palm oil and natural rubber

As environment friendly polymers are required to reduce the green-house gas emissions and global warming, bio-based polyurethane foam (PUF) is attracting interest from the industrial sector and researchers. Bio-based polyols for PUF have been synthesized from various renewable resources, mostly plant oils. The present study explored a novel bio-based PUF produced from a mixture of bio-based polyols synthesized from palm oil and natural rubber. Palm oil-based polyol (POP) was synthesized via an epoxidation reaction of double bonds of palm oil followed by complete oxirane ring-opening. Hydroxy telechelic natural rubber (HTNR) was synthesized by oxidative degradation using periodic acid and sodium borohydride. For comparison, two diisocyanates were used: toluene-2,4-diisocyanate and polymeric methylene diphenyl diisocyanate. POP and HTNR were miscible and all PUFs showed polyhedral semi-closed cells and hardness was in the flexible foam range. One possible application of the novel PUF could be thermal insulation.     

Characterization of shape memory behaviour of CTBN-epoxy resin system

The temperature-responsive poly(vinyl alcohol)/ poly(N-isopropylacrylamide) hydrogel was prepared as a drug delivery carrier. The vitamin B12 release behavior of hydrogel was controlled by direct oxyfluorination. The oxyfluorination of hydrogel changed the surface characteristics to have hydrophilic functional groups. On the other hand, the hydrophobicity of hydrogel increased by fluorination treatment due to the induced hydrophobic functional groups. C-O bond and C-F bond were mainly formed by oxyfluorination and fluorination, respectively. The surface morphology showed the significant variation depending on the oxyfluorination conditions. Both swelling ratio and drug release rate were strongly dependent on the oxyfluorination conditions. The swelling of hydrogel increased further by the surface modification with oxyfluorination in a higher oxygen content to give more hydrophilic properties. The drug release from hydrogel also increased as more hydrophilic functional groups were introduced by oxyfluorination because the favorable affinity at the interface resulted in a higher swelling ratio. On the other hand, the relatively low swelling ratio and slower drug release from hydrogel were observed with more hydrophobic functional groups introduced by fluorination.     

In situ synthesized and dispersed melamine polyphosphate flame retardant epoxy resin composites

The dispersion of flame retardants in polymer matrix has significant impact on the final properties of the final materials. Homogenous dispersion for additive type flame retardant powder in polymer melt or solution with high viscosity is a challenge all the time. In the present research, melamine polyphosphate (MPP) is employed to flame-retard the epoxy resin (EP). Different from direct addition of MPP powder in viscous EP glue like conventional means, MPP is firstly synthesized by melamine and polyphosphoric acid in a good solvent for EP. Keeping fine and even dispersion of the produced MPP particles, EP prepolymer is added into the MPP containing solution. By this way, perfect dispersion of the flame retardant can be achieved both in the glue and the cured resin. A series of tests such as the particle size analysis, flammability evaluation, and mechanical properties tests are conducted to compare the MPP flame retardant EP obtained by this method and the conventional one. It shows that the in situ synthesis and compounding method can endow the MPP incorporated EP glue system with better homogeneity and stability, hence leading to higher flame retardancy and obviously improved mechanical performance of the final composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47194.     

富马酸改性松香树脂的合成

介绍了由天然松香通过富马酸加成改性、再与季戊四醇发生酯化反应合成富马酸改性松香水性树脂的方法.探讨了Diels-Alder加成反应及醇、酸聚合反应的机理,确定了最隹投料比等反应条件.     

水相中合成木质素环氧树脂及其在木材胶黏剂中的应用

以木质素为原料,在水相中合成一种适用于木材胶黏剂的木质素环氧树脂。为了考察木质素环氧化反应条件对木质素环氧树脂的羟基和环氧基的影响,以及对胶合板的胶合强度的影响,采用FT-IR和31PNMR对木质素环氧树脂结构进行表征,并用TG和DTG对木质素环氧树脂的热稳定性进行分析。结果表明,环氧化反应主要发生在酚羟基上,在反应过程中,相比环氧氯丙烷,NaOH的加入量对木质素环氧树脂结构和胶合板的胶合强度影响更大。随NaOH加入量增加,木质素环氧树脂中环氧基团逐渐增多,胶合板的胶合强度呈现先升高、后降低的趋势。当木质素的羟基与NaOH摩尔比为1:1时,由木质素环氧树脂制得的胶合板胶合强度达到最大,湿强度达1.61 MPa,超过国家标准II类板的要求(≥0.7 MPa)。采用扫描电镜研究了黏接机理,发现环氧化程度提高时,固化后的木质素环氧树脂的结构更加稳定且致密,导致胶合板的胶合强度也提高。但过高的环氧化程度会增大胶黏剂的粒径,导致胶黏剂与木板不能形成更好的机械互锁结构,从而降低胶合板的胶合强度。还进一步简化了木质素环氧树脂木材胶黏剂的合成工艺,使环氧化反应后的体系无需处理即可直接应用于木材胶黏剂,减少了胶合板生产工艺流程。此外,经过30天的储存期,胶黏剂黏合强度没有明显下降。通过与商业脲醛树脂木材胶黏剂对比,其黏接强度可以达到商业脲醛树脂的水平。     

Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters

Epoxy resins are increasingly finding applications in the field of structural engineering. A wide variety of epoxy resins are available, and some of them are characterized by a relatively low toughness. One approach to improve epoxy resin toughness includes the addition of either a rigid phase or a rubbery phase. A more recent approach to toughen brittle polymers is through interpenetrating network (IPN) grafting. It has been found that the mechanical properties of polymer materials with an IPN structure are fairly superior to those of ordinary polymers. Therefore, the present work deals with epoxy resin toughening using a polyurethane (PU) prepolymer as modifier via IPN grafting. For this purpose, a PU prepolymer based on hydroxyl-terminated polyester has been synthesized and used as a modifier at different concentrations. First, the PU-based hydroxyl-terminated polyester has been characterized. Next, an IPN (Epoxy–PU) has been prepared and characterized using Fourier transform infrared (FTIR) spectroscopy, thin-layer chromatography (TLC), and scanning electron microscopy (SEM) prior to mechanical testing in terms of impact strength and toughness. In this study, a Desmophen 1200-based PU prepolymer was used as a modifier at different concentrations within the epoxy resin. The results also showed that, further to the IPN formation, the epoxy and the PU prepolymer reacted chemically (via grafting). Compared to virgin resin, the effect on the mechanical properties was minor. The impact strength varies from 3–9 J/m and K_c from 0.9–1.2 MPa m^1/2. Furthermore, the incorporation of a chain extender with the PU prepolymer as a modifier into the mixture caused a drastic improvement in toughness. The impact strength increases continuously and reaches a maximum value (seven-fold that of virgin resin) at a modifier critical concentration (40 phr). K_c reaches 2.5 MPa m^1/2 compared to 0.9 MPa m^1/2 of the virgin resin. Finally, the SEM analysis results suggested that internal cavitation of the modifier particles followed by localized plastics shear yielding is probably the prevailing toughening mechanism for the epoxy resin considered in the present study. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2603–2618, 1998