【作者】 李建；

【导师】 黄志雄；

【作者基本信息】 武汉理工大学 ， 材料学， 2006， 硕士

【摘要】 低压片状模塑料(Low Pressure Molding Compound,简称LPMC)是20世纪90年代发展起来的新一代模压料,其成型压力和成型温度均非常低,可以大大减少对设备和模具的投资成本,是一种经济效益比相当高的新型SMC成型技术,该技术具有广阔的应用前景。 本论文合成了熔点在45～89℃之问、结晶度高、有良好的物化性能和机械性能、适用于低压片状模塑料物理增稠剂的结晶性不饱和聚酯树脂。研究表明,当结晶树脂质量百分含量为10%时,结晶树脂的增稠效果最好;而在结晶树脂的增稠过程中,存在溶胀、氢键和诱导结晶三种作用,其中溶胀和诱导结晶作用最为明显。该研究为LPMC生产工艺的制定提供了理论依据。 此外,本论文研究了LPMC的增稠体系,讨论了增稠剂用量对不饱和聚酯树脂增稠性能的影响。分析了增稠剂在增稠过程中的优缺点,最后决定采用联合增稠剂的方法,即将碱土金属氧化物或氢氧化物(一般用氧化镁)与结晶树脂联合增稠不饱和聚酯树脂体系。研究表明,联合增稠剂的增稠效果比单一增稠剂的增稠效果要好,更加符合低压模塑粘度和工业化生产低成本的要求。 论文还对纯不饱和聚酯树脂的几种单组分引发体系和复合引发体系进行了研究,结果表明:1,1—二(叔丁基过氧基)环己烷/叔丁基过氧化—2—乙基己酸酯(质量比为80:20,总含量为树脂1%)复合引发体系能使树脂充分固化,在相同的成型温度下,使用该复合引发体系所得制品的表观性能高于单组分引发体系,而且制品具有良好的力学性能,是一种适于LPMC成型的中温固化引发体系。 本文中树脂糊的制备主要采用连续计量混合法。另外,为了保证结晶树脂的物理增稠作用,在制备LPMC片材时需要在一部分辊子上进行加热,这样颗粒状结晶树脂遇热熔化为液体状,从而与不饱和聚酯树脂混合均匀,同时也能降低树脂糊粘度以更好地浸渍纤维。收卷处,结晶树脂冷却结晶使树脂糊粘度上升到可模压的粘度,以达到增稠的目的。更多还原

【Abstract】 LPMC, a new generation of molding compounds developing in 1990s, has outstanding properties such as low molding pressure and temperature, greatly saves great of the investment in the equipments and mould, and in favor of the development of molding products, which means a wide application field.The crystalline unsaturated polyesters were synthesized by applying the method of "gradient rising temperature" . The melt points of these crystalline unsaturated polyesters vary from 45℃ to 89℃. They have high crystallinity, excellent heat stability and nice physical and chemical properties. These crystalline unsaturated polyesters were suitable to be used as physical thickener in low pressure sheet molding compound. The melt point of crystalline polyester could be controlled by regulating the mol ratio of the two glycols, saturated diacid and unsaturated diacid, and when the proportion of neopentyl glycol in the system was increased, the values of mechanic properties of crystalline unsaturated polyester improved first, and then dropped.The thickening effect of resin paste was investigated by varying the amount of crystalline polyester resin and the thickening mechanism of crystalline polyesters using in low pressure sheet molding compounds was studied, too. Results show that the thickening effect is excellent when the amount of crystalline polyester resin using in resin paste is 10%, and there are three kinds of functions acting in the processing of thickening. That is: swelling, hydrogen bonds and induction crystallization. The research supports the producing processing for low pressure SMC with theory basement.Several single thickening systems were studied in this paper. The effect of the using amount of each thickener on the thickening property of unsaturated polyester resin were discussed and the superiorities and inferiorities of each thickener in the process of thickening were analyzed and compared, too. By means of using combined thickeners, the earth oxide thickening agent was combined with crystalline polyester to thicken the UP resin system, the thickening effect was improved. The results showed that the thickening effect of combined thickeners which were well suitablefor viscosity conditions of low pressure molding and low cost conditions of industrialized production, was better than single thickener.A serial of single-initiator systems and combined-initiator systems using in unsaturated polyester resin were studied in this paper, too. It was discovered that the gel time and the curing time of resin can be shortened by using combined-initiator systems, compared with single-initiator systems. Besides, the exothermic peak of the curing system of resin can be varied and the productivity can be proved, too. In the same combined-initiator system, the changing amount of low temperature initiator or high temperature initiator has little affection on the storing period of resin. Among all the combined-initiator systems, the system of l,l-Bis( tert-butyl peroxy) cyclohexane / Tert-butyl peroxy-2-ethyl hexanoate is the better. By means of using this system, the resin can be well cured and the apparent properties of products are better than that with single-initiator systems in the same molding temperature. Further more, it makes the products have a good mechanical property. In a word, l,l-Bis( tert-butyl peroxy) cyclohexane / Tert-butyl peroxy-2-ethyl hexanoate is a suitable moderate temperature curing system for low pressure sheet molding compound.In order to ensure the physical thickening effect of crystalline polyester, several rolls in the machine must be heated up, then the grain crystalline polyesters turn into liquid state and flow together, which drops the viscosity of resin paste to better swell fibers. In the end of rolls, crystalline polyesters turn to solid state again, and the viscosity of resin paste rises to a level to be molded, and then the aim of thickening is attained.更多还原