小直径全氟乙烯丙烯共聚物薄壁管的热弯成型工艺

为了解决小直径热塑性塑料薄壁管热弯成型过程中易发生凹陷变形及成型后回弹问题,以外径12mm、壁厚1mm的全氟乙烯丙烯共聚物(FEP) 90°弯管为例,通过研究一次热成型温度、穿芯工艺、弯曲半径及二次热处理温度等工艺参数对弯管成型角度精度的影响提出了一种改进的热弯成型工艺。该工艺流程为:FEP管坯经直径9.5mm的聚四氟乙烯软轴穿芯后,以一定的弯曲半径限位定型并加热至240℃,保温30min;空冷至170℃,再水冷至常温,于装夹状态下去芯处理;二次加热至90℃,并保温30min后水冷至常温。通过该工艺成型的FEP弯管具有较高的成型精度,且无凹陷、无褶皱、并在70℃的模拟工况下应用30min无回弹。经分析FEP成型管性能,成型时的两次加热均未对其力学和电气应用性能造成明显影响。

Hot Bending Process of Minor Diameter FEP Thin-walled Tubes

In order to solve the problems of sagging deformation and rebounding after forming in the hot bending process of minor diameter thermoplastic thin-walled tube,taking fluorinated ethylene propylene(FEP)90°bent tube with 12 mm outer diameter and 1 mm wall thickness as example,a modified hot bending process was proposed through studying the effects of the hot forming temperature,core-through technology,bending radius and secondary heat treatment temperature on the forming angle precision of the tube.The modified process procedure is that,first,the core-through of the FEP tube is done with polytetrafluoroethylene flexible shaft with 9.5 mm diameter and fixed according to a certain bending radius,next,the tube was heated to 240℃and kept for 30 minutes,then it is cooled to 170℃by air cooling and continues to be cooled to room temperature by water,and core-removal is done under clamping,at last,the FEP tube is reheated to 90℃and kept for 30 minutes,then cooled by water to normal temperature.The FEP tube formed by the modified hot bending process has high forming precision and no depression,no wrinkle,no rebounding phenomena occur in the 70℃working conditions for 30 min.By analyzing the properties of the FEP forming tube,twice heating processes have slight significant impact on its mechanical and electrical application performance.