Effect of the molecular weight of sizing agent on the carbon fiber surface and interface properties

The effects of three different molecular weight of sizing agent on the performances of carbon fiber and carbon fiber composites were studied. It was found that a number of grooves uniformly dispersed on the S_1 surface. The depth of grooves on the S_1 surface was smaller than that on the S_2, but bigger than that on the S_3. Small particles on the S_2 and S_3 surface were confirmed by AFM, SEM. XPS also confirmed that S_1 surface contained more O element than others. The results indicated that the high and low molecular weight of sizing agent decreased the interfacial shear strengths and ageing properties of carbon fiber composites, while the moderate molecular weight sizing agent (HIT-7) showed better interfacial adhesion and ageing property.