【作者】 唐晓东；

【导师】 徐建军；

【作者基本信息】 四川大学 ， 高分子科学与工程， 2007， 硕士

【摘要】 近年来通讯设备如个人手持系统(personal handyphone system，PHS)、便携式电话、计算机中央处理器时钟等电信号已经达到GHz的波段，而且这种趋势正在加强。因为电信号的介电损耗正比于所用材料的介电常数的平方根，正比于所用材料的介电损耗角，正比于电信号的频率。所以电信号频率越高，其介电损耗越大。电信号的损耗越大，就越失真，因此有必要找到一种在高频下仍具有较低的介电常数和介电损耗的材料。交联聚苯乙烯塑料，是一种热固性树脂。其在高频下具有较低的介电常数和介电损耗、高电压绝缘性、高抗辐射能力、高模量和空间稳定性等特点；同时其耐热性较好，力学强度也较高。因此交联聚苯乙烯能满足在高频下仍具有较低介电常数和介电损耗的要求。本论文以苯乙烯(St)和二乙烯基苯(DVB)为单体，偶氮二异丁腈(AIBN)为引发剂，采用本体聚合分步升温的方法进行聚合制备低介电损耗交联聚苯乙烯板材。本论文首先通过对聚合体系的凝胶百分率、溶胶百分率和转化率的测量来研究体系的放热规律。发现，对于DVB含量较小的体系，在凝胶点后，体系温度应相对不宜过高；对于DVB含量较大的体系，在凝胶点前，体系温度相对不宜过高，过高则可能导致暴聚，聚合后期，其聚合温度应适当升高或适当延长聚合时间。其次，在放热规律的指导下，设计一聚合条件方案，在此方案下成功的制备了四个配比即St：DVB：AIBN分别为(a)99：1：0.05(b)97.5：2.5：0.05(c)98.5：1.5：0.05(d)98：2：0.05的板材。最后，对制备的板材进行了测试和表征。傅立叶红外光谱显示所合成板材聚合物分子结构上具有苯环和双键结构即所用单体的特征结构。网络分析仪，万能材料实验机，冲击试验机，动态力学分析仪表明，随着DVB含量的增加，交联聚苯乙烯的介电常数、介电损耗、冲击强度和损耗模量峰值均逐步降低，而玻璃化温度逐渐上升；同时，随着DVB含量的增加，交联聚苯乙烯的拉伸强度和断裂伸长率的变化趋势均是先增加后减小，在DVB含量约为1.8％时，出现最大值。最后，我们用扫描电镜对板材的拉伸断裂形貌进行了分析，发现，(1)板材的内部结构从中心到边缘是不均一的，(2)四个体系的板材内除(d)体系即St：DVB：AIBN=98：2：0.05外，其余均有微小空隙出现。因此，预设聚合方案，对于(d)体系的单体配比来说，是比较合适的。所以说，聚合条件对板材的内部结构有很大影响，具体为分段聚合法中的各阶段温度的控制对板材内部结构有决定性的影响。更多还原

【Abstract】 In recent years, the signal band of information communication apparatuses, such as PHS and portable telephones, and the CPU clock time of computer have reached the GHz band, and the trend toward higher frenquency is increasingly obvious. The dieletric loss of an electric signal is proportional to the square root of dielectric consant of the insulating material constituting the circuit and to the product of the dieletric loss tangent and the frenquency of the signal used. Therefore, the higher the frequency of the signal, the larger is the dielectric loss. Since dielectric loss causes attenuation of electric signals to lower the reliability of the signals, it has been necessary to select as an insulator a material which has a low dielectric constant and low dielectric loss tangent. The cross-linking polysterne is a sort of thermosetting resin, which is characteristic of the low dielectic constant, low dielectric loss even in the high frenquency, high voltage and radiation resistance, rigidity and dimensional stability, easy handling in all machining operations, good chemical and heat-resistant, and excellent mechanical properties. So the cross-linking polystyrene is a proper material for low dielectric constant and loss in the band of microwave frenquency.In the thesis, the low dielectric loss cross-linking polystyrene is prepared using styrene(St) and divinylbenzene(DVB) as monomers, azo-bis-isobutyronitrile(AIBN) as initiator, via the bulk polymerization under a controled temperature programming.Firstly, it is necessary to know the exothermal characteristic of the polymerization. The gel effect may be the main feature of bulk polymerization. So the method that is measuring the history of the gelation and the solation can be used to investigate the exothermic law of the bulk polymerization. It is found that when the ratio of DVB is small, the temperature of the system should be low after the gel point, and when the ratio of DVB is large, the temperiture of the system in the pre-gelation period should not be too high, while after the gel piont the temperature should be higher and the reaction time should be prolonged.Secondly, based on the exothermic rule of copolymerization of styrene and divinylbenzene, the proper polymerization process is designed to prepare for low dielecltric loss cross-linking polystyrene. Four recipes for preparing such polystyrene plank are used. The corresponding the ratios of St:DVB:AIBN are (a) 99:1:0.05, (b)97.5:2.5:0.05, (c)98.5:1.5:0.05 and(d)98:2:0.05.Finally, the planks were tested and chatacterized. FITIR spectroscopic study of the broad surface of cross-linking polystyrene indicates that benzene ring and double band are located on the network structure. The dielectric and mechanical properties of the plank was characterized by Network Analyzer, Izod Impact Tester and Dynamic Mechanic Analyzer. The result shows that the impact intensity and the loss modulus are decreased gradually and the glass transition temperature is increased slowly, as increasing of the content of DVB in the copolymer. Meanwhile, the tensile strength and the breaking elongation of the cross-linking polystyrene firstly increases and then decreases with the increase of DVB content, and the maximum is present at around 1.8% of DVB content. Finally, from the SEM photographs of the tension fracture of the planks, the heterogenous interior structure is observed, except of recipe (d). So the polymerization process is a applicable to the (d) systeme. The polymerization process has a great effect upon the interior structure of the plank, namely, the temperature in each step of the polymerization process can definitively affect the interior structure of the plank.更多还原