Treated aramid fibers as reinforcement in nonpolar matrices

Crosslinked polyethylene finds extensive use in applications where improved thermal resistance is required. Furthermore, reinforced and crosslinked polyethylene presents high strength at elevated temperatures, so that the field of applications of such materials is considerably enlarged. Aramid fibers seem to be a promising reinforcement for the above materials since they combine high modulus with thermal resistance and light weight. The development of an adequate adhesive bond between aramid fiber and polyethylene matrix is of course the main problem, taking into consideration that both polyethylene and aramid present reduced chemical affinity to other substances. Thus, fiber pretreatment was performed in order to insert unsaturated groups in the aramid chain. These groups could be, in turn, grafted in the polyethylene backbone during the crosslinking reaction. The aramid fibers were treated with methacryloyl chloride, and then dispersed under stirring in 2% aqueous sodium hydroxide containing 0.5% of a nonionic surfactant. After washing and drying, the fibers were dry blended with polyethylene powder containing 2 phr dicumyl peroxide. The mixture was melt‐blended in a Brabender plasticorder and tensile specimens were prepared. Tensile measurements and microscopy on the fracture surface were carried out in order to evaluate changes introduced in the fiber by surface treatment.