Polyethylene terephthalate(PET) was extruded by single-screw extruder, twin-screw extruder and reactive extruder, respectively. Intrinsic viscosity change of PET extruded at different temperatures and screw rotational speeds was studied. PET extruded with twin-screw extruder degraded the most seriously, and its intrinsic viscosity was reduced by 23.5% averagely. PET extruded by single-screw extruder degraded little at low temperature, while the degradation turned obvious at high temperature with the intrinsic viscosity reduced by 5.8% averagely per 10 ℃ rise; high screw rotational speed was of benefit to preventing the product from degradation; the lower the moisture content of the raw material was, the more difficultly the PET molecular degraded. The degradation level of PET extruded by reactive extruder was higher than that of PET extruded by single-screw extruder. Single-screw extruder is the most appropriate for drying PET processed under the condi-tions of low temperature and high screw speed.% 分别使用单螺杆挤出机、双螺杆挤出机、反应型挤出机挤出聚对苯二甲酸乙二酯（PET），研究其在不同挤出温度、不同螺杆转速下熔融挤出后PET的特性黏数变化情况。使用双螺杆挤出机时，PET降解最严重，特性黏数平均降低23.5%。使用单螺杆挤出机：在较低挤出温度时挤出产物基本不降解；在高温时挤出产物降解明显，挤出温度每提高10 ℃，产物特性黏数平均降低5.8%；较高的螺杆转速有利于防止PET的降解；原料含水量越低，PET分子越不易降解。使用反应型挤出机时，PET热降解程度大于使用单螺杆挤出机。PET最适合使用单螺杆挤出机，在较低挤出温度、较高螺杆转速、物料经过烘干的情况下进行熔融挤出加工。
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