烧结工艺对聚四氟乙烯长丝力学性能的影响

Effect of Sintering Process on the Mechanical Properties of Polytetrafluoroethylene Filament

采用差示扫描量热仪、小角/广角X射线散射仪、万能材料试验机等,研究了烧结过程中温度、时间及冷却方式对聚四氟乙烯(PTFE)长丝结构与力学性能的影响;进一步探究了长丝成型加工过程中拉伸比的影响。结果表明,烧结温度过低,结晶度较高,而烧结温度过高,材料过度烧结导致结晶度下降;断裂强力随温度升高呈现先上升后下降趋势,断裂伸长率明显降低。烧结时间不同,结晶度变化较小,但断裂强度和断裂伸长率均随时间延长而降低。退火制品结晶度高,拉伸强度大,断裂伸长率低;而淬火制品结晶度较低,力学性能较差。其次,随着拉伸比增加,结晶度降低,取向度提高,部分非晶态链沿拉伸轴定向排列,使得长丝断裂强力明显提高,断裂伸长率明显降低。

By means of differential scanning calorimetry,small angle/wide angle X-ray scattering and universal material testing machine,the effects of different sintering temperature,sintering time and cooling methods on the structure and mechanical properties of polytetrafluoroethylene(PTFE)filament were studied.Moreover,the influence of stretching ratio during the filament forming process was further investigated.The results indicate that the crystallinity is higher when the sintering temperature is too low.While the sintering temperature is too high,the material undergoes excessive sintering and the crystallinity decreases.The breaking strength increases firstly and then decreases with the increase of temperature,and the elongation at break decreases obviously.The crystallinity changes slightly with different sintering times,but the fracture strength and elongation at break both decrease with the extension of time.Annealed products have high crystallinity,high tensile strength and low elongation at break,while quenched products have low crystallinity and poor mechanical properties.In addition,with the increase of drawing ratios,the crystallinity decreases and the orientation degree increases,and some amorphous chains are easily aligned along the tensile axis after stretching,which makes the breaking strength of the filament significantly increase and the breaking elongation significantly decrease.