摘要
片状模塑料(Sheet Molding Compound，简称SMC)是一种加入不饱和聚酯树脂、有机添加剂、引发剂、碳酸钙、增稠剂和短切玻璃纤维等组分混合而成的热固性复合材料。与手糊等其它玻璃钢成型工艺相比，SMC成型技术较为复杂，过程中原材料或生产工艺参数的变化都会对最终制品产生影响。故SMC工艺对原材料和生产工艺参数的稳定性要求很高。中国加入WTO已有5年，汽车工业的竞争已经愈来愈激烈。为了降低油耗，减少环境污染，汽车轻量化是汽车工业发展的一个重要途径，采用玻璃钢制品是有效方法。同时随着SMC技术的不断进步，市场的不断扩大，越来越多的应用领域都对SMC提出了相当高的外观要求。因此如何降低乃至消除UPR的固化收缩，提高SMC模压制品的表面光泽度是我国复合材料工业所需研究解决的重要课题。
本文首先对自制的新型低收缩添加剂(LPA)的收缩机理进行了研究，随后重点研究了LPA、引发剂、氧化镁(增稠剂)、碳酸钙填料以及模压工艺参数对SMC制品表面光泽度的影响。研究发现，随着LPA加入量的增多，SMC制品的固化收缩率变小，表面变得光亮、平整；当LPA的加入量超过30份时，SMC制品表面的光泽度增幅减小；适中的过氧化二异丙苯(DCP)用量可以改善SMC制品的表面光泽度；随着MgO的加入量增多，制品的表面光泽度并非一直增加，而是有一个最佳值；平均粒径小于20μm(800目)的碳酸钙，适当的加入量可以提高制品的表面光泽度。模压工艺参数中，随着成型温度的提高，SMC制品的表面光泽度从130℃到140℃快速增大，当温度从150℃到160℃时，制品表面的光泽度增加趋于平缓，170℃时制品表面光泽度有下降趋势；而成型压力和保温保压时间对制品的表面光泽度影响不大。
利用SPSS13.0软件和二次多项式回归分析了SMC中增稠剂、固化剂对SMC制品表面光泽度的影响，得出了高光表面SMC制品表面光泽度的预测公式。结果表明低收缩SMC组分之间具有协同效应：随着MgO用量的增加，LPA的效率提高，制品光泽度增大；DCP含量越小，LPA的热膨胀效果越好，制品光泽度也就越高。通过回归分析，得到低收缩SMC制品表面光泽度的预测方程为：y=222.457+2.688X_2~2-12.949X_3~2(其中X_2：MgO的质量份数，X_3：DCP的质量含量(‰))。
结合制品的弯曲性能，发现随着LPA用量的增加，SMC制品的弯曲强度变化不大，而弯曲模量在LPA加入量超过30份时逐渐下降；SMC制品的弯曲强度和弯曲模量随CaCO_3含量的增加而增加，当CaCO_3用量超过200份时，制品
Sheet molding compound (SMC) is a thermosetting material made of unsaturated polyester resin, organic additives, the initiator, calcium carbonate, thickener and chopped glass fibres strands that are mixed and form sheets. Compared with made by hand and other FRP molding processes, SMC is a bit more complex. Any change in the material or the producing parameter would influence the final product. Thus SMC asks for stabilities of the material and the producing parameter. China has joined WTO for 5 years, the competition in automobile have become fiercer. In order to decrease the oil consumption, and to decrease the environment pollution, low weight is an important way for automobile development, and to use FRP products is the effective method. Meanwhile, along with the SMC technology increasing progress and the market increasing expansion, the quite high outward appearance of SMC are requested in the more and more application fields. So how to decrease and even eliminate the curing shrinkage of unsaturated polyester and to improve the surface finish of SMC are important subjects to our composite material industry.
We have researched contraction mechanism of self-made new low profile additive. Afterwards, we have major studied LPA, the initiator, MgO (thickener), CaCO_3 (filler) and the mould pressing technological parameter with emphasis influence to the surface finish of SMC product. The results show that SMC product has small shrinkage ratio and surface change luminously and smooth with the weight fraction of LPA increasing. When the weight fraction of LPA over 30, the surface finish of SMC product increased range reduces. The moderate weight fraction of dicumyl peroxide (DCP) used may improve the surface finish of SMC product. With the weight fraction of MgO increasing, the surface finish of product continuously increases by no means, but MgO has a best weight fraction. The surface finish of SMC product may improved by adding suitable weight fraction of CaCO_3 whose average grain diameter is smaller than 20μm. In the mould pressing technological parameter, mould temperature is more important influence than mould pressure and time to the surface finish of SMC product. The surface finish of SMC product fast increases with temperature from 130℃ to 140℃. When the temperature increases from 150℃ tol60 ℃, the surface finish of SMC has little increasing. It has a drop tendency, when the temperature is higher than 170℃.
The effect of thickener and the initiator on the surface finish of low profile SMC product were studied by using the SPSS13.0 software and polynomial regression theories. The predicting formula on the surface finish of low profile SMC product was derived. The results show that the synergies have occurred among ingredients of low profile SMC. LPA efficiency is increasing with weight fraction of MgO increasing, the surface finish of low profile SMC product is improving; DCP content is smaller, the LPA has better thermal expansion efficiency and the surface finish of product is higher. We obtain predicting formula about the surface finish of
引文
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