相容剂的选择

Selection of compatibilizer

这种材料的制备同样面临着相容性问题，木粉中主要的成分是植物纤维，植物纤维中含有大量的羟基，极性大，吸湿性强，与塑料的相容性差，必须添加合适的相容剂。用于塑木复合材料加工的相容剂一般为反应型相容剂，特点是由极性和非极性两部分部分组成的嵌段共聚物或者是接枝共聚物。相容原理是利用相容剂的极性部分与植物纤维中的羟基形成氢键或发生酯化反应成酯建链接，而相容剂的非极性部分则与聚合物有良好的相容性，可以溶入聚合物中，这样相当于在植物纤维与聚合物之间搭建桥梁的方式降低了木粉的极性和吸湿性，从而使木粉与聚合物很好的相容在一起。这类相容剂可以是极性单体与非极性单体的低聚物也可以是一些聚烯烃和热塑性弹性体接枝极性单体得到的共聚物。非极性单体通常是一些烯烃，如PP、PE，极性单体用得最多的是马来酸酐。

The preparation of this material is also faced with the problem of compatibility. The main component of wood powder is plant fiber. The plant fiber contains a large number of hydroxyl groups, has large polarity, strong hygroscopicity, poor compatibility with plastic, and a suitable compatibilizer must be added. The compatibilizer used in the processing of plastic wood composites is generally a reactive compatibilizer, characterized by a block copolymer consisting of two parts of polar and nonpolar parts or graft copolymers. The compatibility principle is to use the polar part of the compatibilizer to form the hydrogen bond with the hydroxyl group in the plant fiber or the esterification reaction to the ester, while the non polar part of the compatibilizer has good compatibility with the polymer, which can be dissolved in the polymer, which is equivalent to the way that the bridge between the plant fiber and the polymer is reduced. The polarity and hygroscopicity of wood flour make wood flour compatible with polymers. This kind of compatibilizer can be a oligomer of polar monomers and non polar monomers, or a copolymer of polyolefin and thermoplastic elastomer graft polar monomers. Nonpolar monomers are usually olefins, such as PP and PE, and the most frequently used monomers are maleic anhydride.