Study On High Performance Poly (Phenylene Sulfide) Materials For Electronic Encapsulation

Poly(phenylene sulfide) (PPS) is a high-performance engineering plastics with many excellent properties. In China, although PPS has already been produced in industrialized scale, the post-treatment process of produced PPS is not developed yet. In a sense, the post-treatment process of PPS is become the "bottleneck" for PPS industrialization. Because the commercial PPS has many impurities in it, it can't be used for some applications such as electronic encapsulation, fiber and film manufacture. In electronic encapsulation fields, the traditional thermosetting resin is gradually substituted by thermoplastic materials because the later is a recyclable materials, thus more and more countries developed many thermoplastic include PPS for electronic encapsulation. Because PPS can be used in the electromagnetic shielding, space flight and other military applications, the developed countries such as the United States, Japan forbid both the technique and the products to China strictly. Therefore, it is valuable to develop process for preparing PPS fine powder, high purity PPS and PPS based electronic encapsulation materials.This thesis consists of the following three parts. The first part introduces the properties and applications of PPS, the current situation of electronic encapsulation materials and their developing trends, PPS based electronic encapsulation materials, and the quality of PPS and fillers for producing electronic encapsulation materials.The second part concerns the preparation of the PPS fine powder and the purification process of PPS. Through mechanical grinding can produce PPS fine powder, the homogeneity of the obtained PPS fine powder is unsatisfactory, the resin after crushing needs to be sifted. So this method can only be used for studying, not suitable for industrial production. By treat with some organic amide and some otheraromatic solvents in high temperatures, we found that PPS can also be "crash" to fine powder with diameters less than 40uin. This process implies that it could be used for industrial production. The purification experiments shown that the mixture of PEG and NMP can eliminate the impurities contained in PPS effectively. The influence of PPS size, operating temperature, operating time and the ratio of two solvent have been investigated and the result shown that the best parameters for the purification of PPS are: PPS passing 80 mesh sieve, operating temperature 200-220 °C, operating time 2~4 hours, ratio of two solvents PEG/NMP=l/10. By treated under above-mentioned conditions, the purified PPS shows low impurity. The impurities contained in PPS is determined to be: Na'<30ppm , Li'<3ppm, oligomers<0.5%. These results are consistent with those for high purity PPS reported in literature, which suggest that the PPS by this treatment is suitable for electronic encapsulation. Repeat experiments show that this treatment has good reproducibility and is suitable for industrial production.The third part reported the research on the preparation of PPS based encapsulation materials. PPS .encapsulation materials are prepared by mixing purified PPS, fillers and other processing aids together by different ratio. The mixtures are extruded in two-screw extruder to strands and chopped to pellets, and then the pellets are injection molded to testing specimen for property measurements. The data of measurement shown that the thermal, mechanical, electrical properties and inflammability of obtained composite are similar to those of PPS electronic encapsulation materials reported by foreign company.