热蠕变性对除尘滤袋PTFE缝线强力的影响

缝线是影响除尘滤袋寿命及可靠性的重要因素之一,缝线在长期热烟气作用下失效的案例愈来愈引起业界的关注。通过热态拉伸试验研究了热蠕变性对袋式除尘器滤袋用PTFE缝线强力的影响。在持续高温下对PTFE缝线进行拉伸试验,结果表明:PTFE缝线的拉伸断裂强力随温度升高而大幅下降,试验温度在250℃以上时,其拉伸最大载荷仅1~3 N(线密度1 200~1 250 den);PTFE缝线的拉伸断裂伸长率随温度升高呈现先上升后下降的趋势,在120℃左右达到最大值;高温环境对PTFE缝线的使用寿命有较大影响,缝线能在软化后受到外力作用而断裂失效,在实际工业生产中应给予关注。

Effect of the thermal creep on the strength of the PTFE suture

The present paper is aimed at investigating the chief factors that may bring about negative influence on the service life and the reliability of the dust filter bags from the point of view of the climatic and surrounding temperature changes.As is known,hot gas flow can become a major problem for the industrial smoke dust control technology,particularly in the bag dust running system,whereas sewing thread can be one of the principal factors leading to the breakdown of the filter bags.In the long run,the quality of the suture breakage has already been one of the greatest worries and urgent concerns of the bag-producing industry.In spite of this,what this paper can do is just to focus its main concern on the effect of the thermal creep on the strength of PTFE suture of filter bags through a high temperature tensile test.As a matter of fact,the tensile strength of the PTFE suture can usually be measured by the INSTRON 3365 at a constant high temperature.The results of our experimental measurement show that the tensile strength of PTFE suture tends to decrease with the increase of the temperature range from 19 ℃to 300 ℃.For accuracy,it would be convenient to divide the temperature range into 14 temperature grades between 19-300 ℃ for purpose of the tensile test.For a PTFE thread with a linear density of 1 200-1 250 den,the maximum tensile load from the temperature grates of 250 ℃ on is only 1-3 N.And,next,the tensile elongation at the break of PTFE suture may tend to increase first and then decrease with the temperature going-on rise,till it reaches its maximum grade at about 120 ℃,whereas its suture would only be reduced by about 43％.Furthermore,at the temperature of 300 ℃,the tensile load would only be reduced and left by about 12％,which implies that the glass transition temperature of PTFE is about 120 ℃.In actual industrial application,it is absolutely necessary to try to avoid such a creep effect.If such a high temperature condition is applied,it literally means to apply the composite suture or alkali-free glass fiber suture.In so-doing,the results of the experiments and the related industrial examples would suffer terrible impact on the service lifetime of PTFE suture,for the PTFE suture would be softened at high temperatures,and then would get broken under such external force.Therefore,serious concern and enough attention should be given to the condition of PTFE suture in the actual industrial production.