Hydrophobic surface modification of ramie fibers by plasma-induced addition polymerization of propylene

Abstract

The low affinity between hydrophilic cellulose fibers and hydrophobic matrices leads to poor interfacial bonding, reducing the mechanical performances of natural cellulose fiber-reinforced composites. This study illustrates plasma-induced addition polymerization of propylene to create a hydrophobic surface on ramie fibers for enhancing their bonding with polypropylene (PP). Plasma treatment with propane is applied for comparison. The advancing contact angles of the plasma-treated ramie fibers are raised from 66.3° to 106.1° and the interfacial shear strengths with PP are enhanced up to 36.4%, likely resulted from the increase in fiber surface roughness observed under a scanning electron microscope and the introduction of plasma-grafted PP and alkyl groups on fibers surfaces proven by X-ray photoelectron spectroscopy. It is also revealed that plasma treatment with propylene is highly effective in increasing surface carbon content (from 68.3% to 82.4% in 0.5 min) and more efficient than the treatment with propane, though both plasma treatments show substantial modification efficacies to the fiber surfaces. The treatment duration affects surface roughness more than surface chemical composition, and the optimized treatment time is around 1 min. The modification method developed in this research has the potential to be used for surface modification of fibers for many applications.

Keywords:

• hydrophobic surface modification
• plasma treatment
• ramie
• propylene
• propane

Additional information

Funding

This project was jointly sponsored by the National High Technology Research and Development Program of China (No. 2007AA03Z101); the State Key Program of National Natural Science of China (No. 51035003); Chinese Universities Scientific Fund [grant number CUSF-DH-D-2013024]; Fundamental Research Funds for the Central Universities [grant number NS2013 and KLTST201304]; Shanghai Natural Science Foundation for the Youth [grant number 12ZR1440500]; and Doctoral Scientific Fund Project of the Ministry of Education of China [grant number 20120075120016].