试验参数对滚塑制品低温冲击强度影响

Effects of Test Parameters on Low Temperature Impact Strength of Rotomolded Products

在滚塑制品低温冲击强度的国外测试标准中,对试样的冷冻时间、取出时间和冲击质量三个试验参数的要求各异。考察了这三个试验参数对低温冲击强度的影响规律。结果表明,低温冲击强度随着冷冻时间的延长先增大后减小,最后趋于稳定。低温冲击强度存在极值,该极值出现的时间和试样厚度有关,极值大小和试样厚度及制样方式有关,现有各标准对冷冻时间的规定均不能使低温冲击强度稳定化,测试存在缺陷,建议试样的冷冻时间的小时数不小于试样厚度毫米数的2倍;试样取出时间应不大于15 s,现有国际滚塑协会标准的规定仅能满足厚度不小于21 mm试样的测试要求;低温冲击强度和应变速率的对数呈线性关系,随着应变速率的增加,低温冲击强度降低,这种变化在t检验下显示差异不显著。

In the foreign testing standards for low temperature impact strength of rotational molded products,the requirements of three test parameters for freezing time,taking out time and impact mass of specimen are different.The law of influence of three test parameters on the low temperature impact strength was investigated.The results show that the low temperature impact strength increases first and then decreases with the extension of freezing time,and finally tends to be stable,there is an extreme value of low temperature impact strength,the occurrence time of the extreme value is related to the thickness of specimen,and the size of the extreme value is related to the thickness of specimen and the way of specimen preparation,the rules of existing standards on freezing time can not stabilize the low temperature impact strength,there are defects in testing,it is recommended that the number of hours of the freezing time for the specimen should be no less than 2 times the millimeter number of the thickness for the specimen.The taking out time of freezing specimen should not more than 15 s,the existing association of rotational molders international standard can only meet the test requirement of the specimen which thickness is not less than 21 mm.There is a linear relationship between the low temperature impact strength and the logarithm of strain rate,with the increase of strain rate,the low temperature impact strength decreases,the difference is not significant under t-test.