Effect of thermal crosslink conditions on dynamic mechanical behaviors of flexible epoxy

The dynamic mechanical behavior of a new kind of flexible epoxy FE-1,which was crosslinked under four different thermal crosslink conditions,was studied.Dynamic mechanical measurement was carried out from 10 ℃ to 120 ℃,and loss factor,tan δ and the storagemodulus as functions of temperature were presented under five different frequencies of 0.1 Hz, 1 Hz,5 Hz,50 Hz and 100 Hz. The experimental results show that temperature has dramatic effects on the dynamic mechanical behavior of flexible epoxy. Compared with other common available epoxy, the flexible epoxy has higher loss factor over broad frequency and common temperature range. Activation energy corresponding to glass transition process of FE-1 was calculated from the temperature corresponding to tan 8 rna~ values, obtained at different measurement frequencies. The maximum value of loss factor is 0.75 and the Tg varies from 6 ℃ to 50 ℃, indicating the flexible epoxy can be used as damping polymer materials at common temperature or frequency range.     

Influence of annealing time on the microstructure and properties of Pb(Zr0.53Ti0.47)O3 thin films

The PZT thin films were prepared on (111)- Pt/Ti/SiO2/Si substrates by sol-gel method, and lead acetate [Pb(CH3COO)2], zirconium nitrate [Zr(NO3)4] were used as raw materials. The X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were used to characterize the phase structure and surface morphology of the films annealed at 650 ℃ but with different holding time. Ferroelectric and dielectric properties of the films were measured by the ferroelectric tester and the precision impedance analyzer, respectively. The PZT thin films were constructed with epoxy resin as a composite structure, and the damping properties of the composite were tested by dynamic mechanical analyzer (DMA). The results show that the films annealed for 90 minutes present a dense and compact crystal arrangement on the surface; moreover, the films also achieve their best electric quality. At the same time, the largest damping loss factor of the composite constructed with the 90 mins-annealed film shows peak value of 0.9, higher than the pure epoxy resin.     

端异氰酸酯基聚醚接枝环氧树脂的性能研究

合成了端异氰酸酯基聚醚（ITPs）改性双酚A型环氧树脂，通过红外光谱（IR）、动态热机械分析（DMA）研究了ITPs和EP之间的化学反应及改性环氧树脂酸酐固化体系的热性能，并测试了固化体系的力学性能。结果表明：ITPs作为枝链接枝到环氧树脂上：随着加入ITPs质量分率增加，其固化体系的冲击强度和弯曲强度上升，当ITPs含量为10％时，两者达到最大值：动态热机械分析（DMA）结果表明改性环氧树脂固化体系的玻璃化转变温度（Tg）随ITPs的含量增大而降低：当ITPs质量分率大于15%时，过量的ITPs与改性环氧树脂会形成相分离。     

Isocyanate-terminated Polyethers Toughened Epoxy Resin:Chemical Modification,Thermal Properties,and Mechanical Strength

The toughening of the diglycidyl ether of bisphenol A epoxy resin with isocyanate-terminated polyethers(ITPE)was investigated.The progress of the reaction and the structural changes during modification process were studied using FTIR spectroscopy.The studies support the proposition that TDI(tolylene diisocyanate)acts as a coupling agent between the epoxy and polyethers,forming a urethane linkage with the former and the latter,respectively.Me THPA-cured ER/ITPs blends were characterized using dynamic mechanical analysis(DMA)and thermogravimetric analysis(TGA).It is indicated the glass transition temperature(T g )of systems was lower than the T g of pure epoxy resin and overfull ITPE separated from the modified epoxy resin and formed another phase at an ITPE-content of more than 10wt%.The thermal stability was decreased by the introduction of ITPE.The impact strength and the flexural strength of the cured modified-epoxy increased with increasing the ITPE content and a maximum plateau value of about 24.03 kJ/m2 and 130.56 MPa was measured in 10wt%ITPE.From scanning electron microscopy(SEM)studies of the fractrue surfaces of ER/ITPE systems,the nature of the micromechanisms responsible for the increases in toughness of the systems was identified.     

Damping properties of fly ash/epoxy composites

An inexpensive fly ash (FA), which is from a waste product, was employed to prepare fly ash/epoxy composites. The purpose of this study is to characterize the contributions of matrix viscoelasticity, hollow structure characteristic (porosity), and filler/matrix interface friction to the high vibration damping capacity of such composites. The damping properties of the composites were investigated in the temperature range of -40 to 150°C and in the frequency range of 10 to 800 Hz by using a tension-compression mode. The results indicate that the peak value of damping loss factor (tanδ) for the fly ash/epoxy composites can reach 0.70-0.90 in test specification, and the attenuation of damping loss factor is inconspicuous with increasing frequency. In addition, scanning electron microscope (SEM) was used to observe the morphology of the fly ash as well as its distribution in the matrix, which will help to analyze the effect of fly ash on the damping properties of the fly ash/epoxy composites.     

Isocyanate-terminatcd Polyethers Toughened Epoxy Resin： Chemical Modification, Thermal Properties, and Mechanical Strength

The toughening of the diglycidyl ether of bisphenol A epoxy resin with isocyanateterminated polyethers （ITPE） was investigated. The progress of the reaction and the structural changes during modification process were studied using FTIR spectroscopy. The studies support the proposition that TDI （tolylene diisocyanate） acts as a coupling agent between the epoxy and polyethers, forming a urethane linkage with the former and the latter, respectively. Me THPA-cured ER/ITPs blends were characterized using dynamic mechanical analysis （DMA） and thermogravimetric analysis （TGA）. It is indicated the glass transition temperature （T） of systems was lower than the T of pure epoxy resin and overfull ITPE separated from the modified epoxy resin and formed another phase at an ITPE-content of more than 10wt%. The thermal stability was decreased by the introduction of ITPE. The impact strength and the flexural strength of the cured modifiedepoxy increased with increasing the ITPE content and a maximum plateau value of about 24.03 kJ/m^2 and 130.56 MPa was measured in 10wt% ITPE. From scanning electron microscopy （SEM） studies of the fractrue surfaces of ER/ITPE systems, the nature of the micromechanisms responsible for the increases in toughness of the systems was identified.     

The influence of fiber type and conformation on the damping property of FRP composite

In order to get a fiber reinforced plastic(FRP) composite with good damping property as well as good mechanical properties, different types of reinforcing materials were used to reinforcing a damping resin. The influence of fiber types and conformation on the damping property of the composite are tested. Compared to the glass fiber(GF), carbon fiber(CF) can improve the damping factor of the composites; the highest tanδ value is 0.827 while the Tg is 22.5 ℃. The style of the fibers also influences the damping factors of the composite. The composite reinforced with mat has higher loss factors than that composite reinforced with clothe for the reason that the former has the ability to deform and the composite has higher resin content. The loss factor of GF mat reinforced composite is 0.704 while the Tg is 27 ℃. Both composite has good damping properties and can be used as the damping layer of the structural damping composite.     

高断裂伸长率柔性环氧树脂体系的研究

将端羧基柔性扩链剂用于环氧树脂/酸酐固化体系中,制备中温固化高断裂伸长率柔性环氧树脂.考察了柔性扩链剂用量对固化物力学性能的影响.研究结果表明,较少固化剂用量、较多柔性扩链剂用量和适宜的促进剂用量有利于获得高断裂伸长率的固化物.固化物断裂伸长率可达236％,拉伸强度为6.08 MPa.     

Decomposition behavior and decomposition products of epoxy resin cured with MeHHPA in near-critical water

A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The decomposition rate of epoxy resin raised rapidly as the reaction time and reaction temperature increased. The decomposition reaction products were characterized by infra-red spectra and gas chromatography-mass spectrometry. The phenol, isopropylphenol, 4, 4′-(1-methylethylidene) bis-phenol were found as the main compounds in liquid products, which were common monomers from epoxy resin. When reaction was carried out at the temperature of 260 °C–300 °C, the decomposition mechanism of epoxy resin was envisaged as the ether and ester bonds cracking.     

新型环氧树脂固化剂的性能

采用亲核取代反应合成了新型含有醚酮键的芳香胺固化剂(BADK),并对其结构进行了表征。选用BADK作为固化剂,对含有联苯结构的环氧树脂和通用型环氧树脂E-51的固化条件、固化物耐热性和吸湿性进行了研究。实验结果表明:新型固化剂的使用提高了通用型环氧树脂E-51的热性能;含联苯结构的环氧树脂固化物与E-51相比,无论是热性能还是耐湿性都有很大的提高。     

水性环氧乳液的制备与性能

采用丁二酸酐对聚乙二醇单甲醚(mPEG)进行改性,得到羧酸型mPEG⁃COOH,将mPEG⁃COOH与环氧树脂反应,得到水性环氧树脂乳化剂。环氧树脂乳化剂与环氧树脂混合,通过相反转技术,得到稳定的水性环氧树脂乳液。采用红外光谱、高效液相色谱、粒度分析仪等对该乳化剂的结构及环氧树脂乳液的稳定性、粒径分布等进行表征。研究了乳化剂合成时甲氧基聚乙二醇相对分子质量、环氧树脂相对分子质量、乳化剂浓度等对乳液稳定性的影响。结果表明,成功制备出了水性环氧乳化剂及水性环氧乳液。水性环氧乳液的粒径分布在0.8~1.5 μm,且乳液稳定性良好。该水性环氧树脂乳液与胺类固化剂室温固化后,所得涂膜具有较好的耐水、耐污性能,其吸水率和耐水失重率分别为0.35%和0.25%。     

含柔性链SiO_2/EP纳米杂化材料的固化动力学

采用溶胶-凝胶法制备了聚硅酸溶胶,在其表面接枝柔性链段并以此为前驱物,通过原位聚合法制备了SiO2/EP纳米杂化材料。利用差示扫描量热仪对杂化材料的固化动力学进行了研究。采用Kissinger和Crane等方法,利用不同升温速率下的DSC曲线,分别求出固化体系的表观活化能Ea、反应级数n和频率因子A等参数,得出了固化体系的反应动力学方程。     

环氧树脂用作不锈钢管表面应变片防水材料的可靠性试验研究

在对土体中不锈钢管桩身应变测量时,环氧树脂常常被用于应变片的防水,然而环氧树脂在空气中或者受水作用时呈现低收缩性,该收缩应变往往会对桩身真实应变带来一定误差。另外环氧树脂剪切强度和开裂应变较低,其受到偶然外力作用时可能会剥离不锈钢管,同时剥离包含其中的应变片,这会导致部分测点失测,这两个细节有时会被忽视。文章实测环氧树脂在空气中和受水作用时给不锈钢管表面应变片带来的收缩应变,与钢管表面的裸片应变进行对比,分析环氧树脂应用于该情况时的可靠性。     

二氧化硅改性环氧树脂胶黏剂性能研究

采用聚氨酯增韧环氧树脂,并利用有机化的纳米SiO2为改性剂制备纳米改性环氧树脂胶黏剂.利用扫描电子显微镜( SEM)观察无机纳米粒子在聚合物基体中的分散性及复合材料的断面形貌,结果表明无机纳米粒子在复合材料中分散性良好,而且聚氨酯在环氧树脂基体中形成了“孔洞结构”.采用电子拉力机、TGA以及介电谱仪等方法测试了复合材料...     

不饱和树脂绝缘阻燃漆的合成与性能研究

通过在环氧树脂中引入双键合成不饱和环氧树脂,加入稀释剂苯乙烯制备无溶剂型绝缘漆,通过电阻率和介电损耗对其绝缘性能进行表征.研究不同阻燃剂对绝缘漆体系的阻燃性能、电性能和力学性能的影响.通过DSC研究绝缘漆体系的固化工艺条件.实验结果表明,绝缘漆体系中当三聚氰胺磷酸盐（MP）质量分数为30%时,体系的阻燃性能达到UL0-94 V-0级,绝缘阻燃漆的电阻为7.8×10^13Ω,电阻率为4.36×10^15Ω.·cm,介电损耗为0.014 5,此时拉伸强度为3.34MPa,冲击强度为0.71 kJ/m^2.     

丙烯酸酯改性己二胺固化剂对环氧树脂性能的影响

利用丙烯酸酯类对己二胺进行改性,作为环氧树脂的室温固化剂。利用红外光谱分析了固化剂的氨解变化,讨论了改性固化剂对环氧树脂固化反应产物的拉伸、弯曲、冲击等性能的影响。实验结果表明,丙烯酸酯改性的己二胺固化剂可以在室温下固化环氧树脂,所得的环氧树脂具有较好的力学性能。     

AA/AMPS接枝环氧树脂E-44的水性化改性研究

为改善环氧树脂E-44的水溶性,以丙烯酸（AA）和2-甲基-2-丙烯酰胺基-丙磺酸（AMPS）为接枝共聚的单体对环氧树脂进行水性化改性.研究了引发剂、不同单体及比例和反应条件对接枝共聚物水分散稳定性的影响并通过红外光谱对产物进行了表征.结果表明,以2.71 wt％的BPO为引发剂、以体积比1∶1的无水乙醇-乙二醇单甲醚为混合溶剂,在接枝共聚反应温度110℃,下用质量比为1∶1的AA/AMPS对等质量的环氧树脂E-44进行改性,得到的改性环氧树脂水性化改性效果最好,乳液离心稳定性和贮存稳定性最高.     

间甲苯胺改性双氰胺固化环氧树脂的DSC研究

采用化学改性合成的间甲苯胺改性双氰胺衍生物作为环氧树脂潜伏性固化剂，通过差示扫描量热法（DSC）研究了间甲苯胺改性双氰胺／环氧树脂E-44体系的固化反应。结果表明，间甲苯胺改性双氰胺与双氰胺相比，具有较高的固化反应活性，显著降低了固化反应的温度，而且间甲苯胺改性双氰胺／环氧树脂E-44体系也具有较好的贮存稳定性。同时间甲苯胺改性双氰胺／E-44环氧树脂体系的动力学研究也表明该固化体系的活化能明显降低，固化反应活性与未改性前相比，有很大程度的提高。     

桐油改性酚醛环氧树脂合成及室温固化物性能

以桐油与苯酚在酸催化下反应生成桐油-苯酚取代物,并进一步在酸性条件下与甲醛反应生成桐油改性二阶酚醛树脂。利用FTIR,GPC等对其结构进行了表征。FTIR分析证明,桐油与苯酚的反应破坏了桐油的共轭双键,形成了新的取代产物。当该产物在酸性条件下与甲醛反应并进一步进行环氧化后,形成桐油改性酚醛环氧树脂。GPC研究表明,所形成的树脂是桐油改性环氧树脂与普通二阶酚醛环氧树脂的复合物。其中桐油改性环氧树脂的数均相对分子质量为3 482,二阶酚醛环氧树脂的数均相对分子质量为619。选用了不同的室温固化剂对所合成的桐油改性酚醛环氧树脂和E-44环氧树脂复配物进行固化性能研究。研究表明,所合成的桐油改性酚醛环氧树脂与E-44质量比在0.5~2.0进行复配,固化后可获得较好的力学性能。     

辐射热流强度对塑料燃烧裂解的影响

应用锥形量热仪研究了环氧树脂、酚醛树脂、EVA和PA6 4种塑料的燃烧裂解行为,得到了在不同辐射热流强度(25 kW.m-2、50 kW.m-27、5 kW.m-2)下材料的点燃时间、热释放速率、质量损失速率、燃烧剩余物的含量等燃烧性能参数,分析比较了不同塑料的燃烧裂解行为,实验结果发现,成炭性的材料在燃烧裂解过程中表现出了较低的可燃性。