8
它的化学结构与PE相似,只是聚乙烯中的全部氢原子都被氟原子所取代。由于C-F键键能高,性能稳定,因而其耐化学腐蚀性,能够承受除了熔融的碱金属、氟化介质以及**300℃的氢氧化钠之外的所有强酸(包括王水),以及强氧化剂、还原剂和各种的作用;PTFE分子中F原子对称,C-F键中两种元素以共价键结合,分子中没有游离的电子,使整个分子呈中性,因此它具有优良的介电性能,而且其电绝缘性不受环境及频率的影响。它的体积电阻大于1017健?m,介电损耗小,击穿电压高、耐电弧性好,能在250℃的电气环境下长期工作;因PTFE分子结构中没有氢键,结构对称,所以它的结晶度很高(一般结晶度为55%~75%,有时高达94%),使PTFE耐热性能好,其熔融温度为324℃,分解温度为415℃,使用温度为250℃,脆化温度为-190℃,热变形温度(0.46MPa条件下)为120℃。PTFE的力学性能良好,其拉伸强度为21~28MPa,弯曲强度为11~14MPa,伸长率为250%~300%,对钢的动静摩擦系数均为0.04,比尼龙、聚、聚酯塑料的摩擦系数都小。
3M™ Dyneon™ PTFE Compound TF 2274 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 3105 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 3215 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 3310 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 3311 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 3712 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4102 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4103 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4104 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4105 3M Advanced Materials Division PTF
M™ Dyneon™ TFM™ Modified PTFE Compound 4213 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 4215 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 4216 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 6105 BR 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 6220 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 6221 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 6302 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound 8854 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE Compound R4213 3M Advanced Materials Division PTFE
3M™ Dyneon™ TFM™ Modified PTFE TFR 1502 A 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4215 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4216 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4302 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4303 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 4705 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6105-N 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6220 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6221 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6302 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6404 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6406 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 6711 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 7149 3M Advanced Materials Division PTFE
3M™ Dyneon™ PTFE Compound TF 7921 3M Advanced Materials Division PTFE
⑶聚四氟乙烯的熔体粘度很高,在高温下也不流动。它在熔点(327℃)以上,熔体粘度达到1 010 Pa.s,即使加热到分解温度也不流动,这就使它不能采用一般热塑性塑料的成型方法,而要采用类似粉末冶金那样的烧结方法成型。 ⑷PTFE具有**的不粘性,限制了其工业上的应用。它是好的防粘材料,这种性能又使它与其他物件的表面粘合为困难。
若要充分烧结,必须使用程序控温烘箱。其温度将缓慢地从室温升高至363°到382°C (685°到720°F)。在这种温度下的维持时间因零件的几何形状和尺寸的不同而有所不同。然后,烤箱温度将会缓慢地降回至室温。未进行适当烧结的毛坯形状其物理性能(比重,拉伸强度,拉伸率,弯曲寿命)、电气性能以及耐渗透和耐化学性比较低劣。
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