炭纤维上浆剂对浮沉法体密度测试的影响

Effect of sizing agent on carbon fiber density measurements using a floatation method

对上浆剂去除前后的炭纤维进行了体密度、上浆剂含量和微观形貌测试分析。结果表明,未除浆样品在浮沉法体密度测试时分层,上层样品絮集严重,上浆剂在纤维表面堆积明显,含量约为2.17%;下层样品轻微絮集。采用丙酮萃取法除浆,测得上浆剂含量为1.20%,除浆样品在浮沉法体密度测试时依然分层,上层样品轻微絮集,有少量上浆剂堆积,下层样品分散均匀。采用450℃热解法除浆,测得上浆剂含量为1.53%,除浆样品在密度液中分散均匀,表面无上浆剂堆积。扫描电镜观察及理论分析表明,炭纤维表面上浆剂残留及不均匀分布引起样品密度不均一,是导致浮沉法体密度测试分层的主要原因;表面上浆剂去除越充分,体密度测试结果准确性越高;比较而言,高温热解是去除炭纤维表面上浆剂的更有效方式。

The density of T300 carbon fiber, as well as the amount of sizing and micro-structure were measured, before and after removing the sizing. The results showed that there was apparent stratification when measuring the density of the carbon fiber by the sink/float method, without removing the sizing. The upper sample layer was seriously flocculated with an excessive sizing amount of 2.17%, while the bottom-layer also flocculated. Two methods including acetone extraction and pyrolysis, were conducted to removing the sizing. It was shown that the measured amounts of sizing for the two methods were 1.20% and 1.53%, respectively. For the sample after immersion in acetone, there was still stratification in the sink/float test, with the upper sample layer flocculated because of the remaining sizing;while samples at the bottom dispersed relatively well. However, for the thermally treated samples the sizing was adequately removed, which resulted in the uniform density and dispersion during the test. This indicates that the non-uniform distribution of sizing agent on the surface of the CFs is the main reason for stratification during the density measurement. Therefore, the sizing must be fully removed in order to obtain an accurate density for the carbon fibers. Moreover, it can be seen that pyrolysis is an effective way to remove the CF sizing agent.