EPDM绝热层低温拉伸力学性能研究

Study on tensile properties of EPDM insulation at low temperature

绝热层的低温力学性能决定了其最低使用温度。为改善三元乙丙(EPDM)绝热层的低温力学性能,研究了测试温度、拉伸速度和配方组成对其低温拉伸力学行为的影响。结果表明,测试温度对EPDM绝热层的拉伸力学行为影响明显,100 mm/min拉伸速度下,测试温度从室温降低至-60℃时,绝热层的抗拉强度不断增加(6→33 MPa),断裂伸长率显著下降(670%→42%),应力-应变曲线出现明显的应力屈服,初始模量显著提高。温度越低,拉伸速度对绝热层应力-应变曲线形态的影响越明显;应力屈服对拉伸速度具有更大的依赖性,提高拉伸速度与降低温度的效应相似。EPDM橡胶基材结构参数对绝热层低温力学性能的影响较明显,橡胶第三单体含量越高,乙烯含量越低,低温力学性能越差;纤维的加入进一步束缚了橡胶分子链段在低温下的活动能力,应力-应变曲线变化亦与降低温度效应相似;补强填料对绝热层的拉伸应力-应变曲线形态影响较小。总体而言,EPDM绝热层在其玻璃化转变温度-40℃附近仍具有较好的力学性能,断裂伸长率仍可达300%以上;当温度降至其脆性温度(约-55℃)以下,断裂伸长率降至极低值,材料不再具有高弹性。

The low-temperature mechanical properties of the insulation determine its minimum operating temperature.In order to improve the low-temperature mechanical properties of EPDM insulation,the effects of test temperature,tensile rate and formula composition on its low-temperature mechanical behavior were studied.The results show that test temperature has obvious effect on tensile mechanical behavior of EPDM insulation.Under the tension rate of 100 mm/min,when the test temperature drops from room temperature to-60℃,the tensile strength of the insulation increases continuously(6→33 MPa),the elongation at break decreases significantly(670%→42%),the stress-strain curve occurs obvious stress yield,and the initial modulus increases significantly.The lower the temperature is,the more obvious the effect of tensile rate on stress-strain curve shape of the insulation is.The stress yield is more dependent on tensile rate and the effect of increasing the tensile rate is similar to that of decreasing the temperature.The structural parameters of rubber base material have obvious influence on mechanical properties of the insulation at low temperature.The higher the content of the third monomer and the lower the content of ethylene,the worse the low temperature mechanical properties of the insulation.The addition of fiber further restricts the activity of rubber molecular chain segment at low temperature,and the change of stress-strain curve is similar to that under reducing temperature.The reinforcing filler has little influence on the stress-strain curve shape of the insulation.In general,the insulation still has good mechanical properties near its glass transition temperature of-40℃,the elongation at break can still reach more than 300%.When the temperature drops below its brittleness temperature about-55℃,the elongation at break drops to extremely low value,and the material no longer has high elasticity.