环氧树脂(EP)具有粘接力强，粘接面广，固化物尺寸稳定性好，收缩率低，优异耐化学腐蚀性能，力学强度高，高绝缘电阻，易加工等优势，广泛应用于机械、电子电气、航空航天、先进复合材料等工业领域。但由于EP固化物自身交联密度高，导致其脆性较大，冲击韧性差，限制了其实际工程应用。此外，EP还存着介电常数和损耗相对较高的缺陷，绝缘电阻也需进一步提高。当前高速发展的微电子信息技术使得电子产品向缩微化、便携式、多功能和高可靠性等方向发展，对在该领域应用的EP的电性能提出更高要求，要求EP具备更低介电常数和损耗，利于信号快速传递和减少信号畸变；以及更高绝缘电阻和击穿强度，利于提高器件的使用安全可靠性。因此，提高EP的力学冲击韧性和绝缘电阻及击穿强度，降低介电常数和损耗的研究显得尤为重要。极性液体橡胶如CTBN、HTBN等改性EP的韧性是过去30年来较成功的方法，但改性后EP的电绝缘性下降，介电常数和损耗有所升高。 本研究采用弱极性端羟基聚丁二烯液体橡胶(HTPB)改性EP。首先用二聚脂肪酸二异氰酸酯(DDI)对HTPB进行封端，制备了端异氰酸酯基HTPB预聚物(ITPB)，再分别以HTPB和ITPB为改性剂，甲基六氢苯酐为固化剂对EP进行改性研究，考察了HTPB和ITPB对EP物理性能的影响情况，重点探讨了改性剂用量对EP固化物微观结构、热、力和电性能影响。对反应过程和试样的微观结构形貌，以及热、力学性能(冲击，拉伸，弯曲)和电性能(体积和表面电阻率，击穿强度，介电常数和损耗)的研究发现： (1) 红外及核磁分析表明EP的环氧基团和HTPB的-OH发生化学反应；ITPB改性EP体系中，DDI的-NCO先与HTPB的-OH发生反应，ITPB/EP中出现了噁唑烷酮的-C=O吸收峰。结果表明HTPB、ITPB的活性官能团均与EP发生了化学反应，显著强化了二者间相界面作用力和相容性。 (2) HTPB和ITPB的加入均使EP热稳定性有所下降，ITPB/EP的热稳定性降低程度较小，比HTPB/EP热稳定性优异。 (3) 加入HTPB和ITPB，EP力学性能获得不同程度改善，在10～20 phr用量范围内EP获得优异的综合力学性能，10 phr HTPB/EP体系的冲击强度最高达16.4 kJ/m2，15 phr ITPB/EP体系的冲击强度最高达18.5 kJ/m2，EP韧性显著提高。 (4) 扫描电镜(SEM)观察到HTPB、ITPB均匀分散于EP基体中，橡胶相与EP相形成“海-岛结构”，ITPB/EP体系中橡胶分散相粒子尺寸更细小，归因于良好的界面作用。 (5) HTPB/EP和ITPB/EP改性体系的体积电阻率和表面电阻率均显著增大；20 phr HTPB及ITPB用量时，EP电击穿强度分别提高到38.22 kV/mm及43.57 kV/mm，ITPB改性EP体系呈现更高绝缘电阻。室温下，HTPB、ITPB的加入均降低EP介电常数和损耗，两种体系的介电损耗在宽频范围内都处于较低水平(<0.021)，但ITPB/EP体系介电常数随ITPB用量增加而降低幅度更为显著。随频率升高，界面极化和偶极子无法跟上外电场变化，介电常数下降。EP、HTPB/EP及ITPB/EP的交流电导率均随频率直线上升，呈现典型的绝缘体行为，电模量结果进一步证明了材料的介电响应行为及机理。 (6) 对改性EP的动态介电性能的研究发现，低温下，被冻结的链段难以对施加的外电场作出响应，纯EP、HTPB/EP、ITPB/EP的介电常数和损耗在低温段对频率及温度的依赖性较弱。在较高温度下，链段运动性逐渐增强，介电常数和损耗随温度升高而增加，并表现出较强频率依赖性。低介电常数的HTPB及ITPB使用限制了EP分子链段在高温下的运动，抑制和减少体系中的界面极化，降低材料介电常数及在高温下引起的介电损耗。另外，HTPB/EP体系介电常数和损耗对温度的依赖性比ITPB/EP体系的更加明显，在较高温度时，ITPB/EP的介电常和损耗均低于HTPB/EP的，表明ITPB/EP体系的电性能的温度稳定性更优异。电模量分析进一步佐证了材料的介电响应行为及机理。 本研究中采用的两种改性剂均同时提高了EP体系力学冲击韧性和绝缘电阻、击穿强度，降低了介电常数和损耗，相比而言，ITPB/EP综合性能相对更优异。所制备的HTPB/EP和ITPB/EP改性体系在高频微电子封装及覆铜板领域具有潜在的应用价值。

Epoxy resin (EP) have been widely used in the field of mechanical, electrical and electronic, aerospace industry, and advanced composites due to their good adhesion, dimensional stability, low shrinkage on cure, good chemical resistance, high mechanical strength, excellent electrical insulation properties, and good process ability and so on. However, due to the high crosslinking density of the EP cured product, the brittleness is large and the impact toughness is poor, which limits its practical engineering application. In addition, the dielectric constant and loss of epoxy resin is relatively high, and the insulation resistance needs to be further improved. The current high-speed development of microelectronics information technology makes the development of electronic products towards the micro-miniaturization, portable, multifunctional, high reliability and other direction，which poses a higher demand for EP electrical performance. EP used in the microelectronic engineering is expected to have lower dielectric constant and loss, resulting in a rapid signal transmission and suppression of signal distortion of electronic devices; Furthermore, EP is expected to have enhanced insulation resistance and electrical breakdown strength, which can improve the safety and reliability of electronic devices. Therefore, it is very important to improve the mechanical impact toughness, electrical insulation and breakdown strength of EP, and to reduce the dielectric constant and loss of EP. Over the past 30 years, modifuon of EP toughness with the polar liquid rubber such as CTBN, HTBN are very successful methods. But the modifications lead to a decrease in the electrical insulation and an increase in dielectric constant and loss. In the present study, the weakly polarized hydroxyl-terminated polybutadiene (HTPB) liquid rubber was employed to modify EP. HTPB was first reacted with dimer fatty acid diisocyanate (DDI) to prepare the isocyanate group HTPB prepolymer (ITPB). Then, HTPB and prepared ITPB were employed to modify EP with methyl hexahydrophthalic anhydride as a curing agent, respectively. The effects of HTPB and ITPB on the physical properties of EP cured networks were discussed. The chemical reactions, morphological, thermal properties, mechanical properties (including impact, flexural, and tensile) and electric properties (including volume and surface electric resistivity, dielectric breakdown strength, dielectric constant and loss) of neat EP, andmodified EP were investigated. The following conclusions can bedrawn based on the experiments: (1) The Fourier transform infrared (FTIR) and nuclear magnetic resonance analysis evidenced the occurrence of a chemical reaction between the oxirane ring of EP and the hydroxyl functional group of HTPB. The -C=O absorption peak of the oxazolidinone appeared in ITPB/EP, which indicated that the -NCO of DDI reacted with the -OH of HTPB. The active functional groups of HTPB and ITPB reacted with EP, which significantly enhanced the interaction and compatibility of two phases between HTPB and EP and between ITPB and EP. (2) TGA analysis confirmed that the addition of HTPB or ITPB decreased the thermal stability of EP. Comparably, the thermal stability of ITPB/EP is superior to that of HTPB/EP. (3) The mechanical results showed that HTPB or ITPB modified EP were superior to that of pure EP, and all the best overall mechanical properties were normally achieved with 10~20 phr of modifier content. EP’ toughness significantly was improved. At the dosage of HTPB about10 phr, the highest impact strength of HTPB/EP can be obtained at 16.4 kJ/m2, and the 15 phr ITPB modified EP exhibited the maximum impact strength of 18.5 kJ/m2. (4) Scanning electron microscopic (SEM) micrographs showed that: 1) HTPB and ITPB particles were uniformly dispersed in the EP matrix. The rubber phase formed a "sea-island structure" in EP matrix; 2) the particle size of ITPB was smaller in the ITPB/EP system compared with the HTPB-EP system due to good interface interaction between ITPB and EP. (5) The results demonstrate that: 1) the HTPB or ITPB modified EP has higher surface and volume resistivity and dielectric strength as compared to the neat EP; 2) The dielectric breakdown strength of 20 phr HTPB modified EP is 38.22 kV/mm, in comparision with 43.57 kV/mm of 20 phr ITPB modified EP. 3)enhnaced electric insulations of ITPB/EP, for examples, at room temperature, the dielectric constant and dissipation factor of HTPB/EP or ITPB/EP decreases with increasing the HTPB or ITPB concentration, and the dielectric loss of the two systems is remained at a rather low level (<0.021) at wide frequency range. Moreover, the dielectric constant of the ITPB/EP is less than that of the HTPB/EP. With an increase in frequency, the interface polarization and dipoles can not keep up with the changes of external electric field, resulting in decreased dielectric constant. The AC conductivities of EP, HTPB/EP and ITPB/EP increase linearly with the frequency, suggesting the behavior of typical insulators. The results of electrical modulus further verify the analysis of the materials’ dielectric response. (6) Dynamic dielectric properties of the modified EP confirmed that the segments of matrix are frozen at low temperatures. The modified EP is difficult to respond to the applied electric field. The all pure EP, HTPB/EP, and ITPB/EP show weak temperature and frequency dependences of dielectric constant and loss. The motion of the segments increases gradually at higher temperatures, so, the dielectric constants and losses increase with increasing temperature, thus exhibiting strong frequency dependence. The interface and dipole polarizations can not catch up with the change of applied electric field at higher frequencies, thus reducing the dielectric constant and the loss of the composites. The low permittivity and loss of HTPB and ITPB effectively inhibit the movement of the EP molecules at high temperature, thereby reducing the interface polarization, which leads to the decreased dielectric loss at high temperatures. In addition, dependence of the dielectric constant and loss on temperature of HTPB/EP system are more prominent compared with ITPB/EP system. The dielectric constant and loss of ITPB/EP are lower than that of HTPB/EP at higher temperature, indicating that the good dielectric stability of ITPB modified EP system. The analysis of electrical modulus also further reaffirms the mechanism of dielectric response for the materials. The two modifiers used in this study both improved the mechanical impact toughness, electrical insulation and breakdown strength of EP system, and reduced the dielectric constant and loss of EP. The comprehensive performance of ITPB/EP is relatively more prominent compared with HTPB/EP. The prepared HTPB/EP and ITPB/EP system have potential applications in the fields of high frequency microelectronics packaging and printed circuit boards industry.