Study On Modification Of PBO Fibers By Atmospheric Pressure Plasma

Poly (1,4-phenylene-cis-benzobisoxazole) (PBO) fiber is one of the liquid crystalline heterocyclic polymers. It is the new generation of high performance fibers after Kevlar fiber and is the organic fiber which has the best comprehensive properties currently. It is widely used in military protective clothing, communications materials, heat-resistant protective clothing and sports products attributed to its excellent mechanical properties, chemical resistance and heat resistance. However, the use of PBO fibers as reinforcements in advanced composites has been limited by the poor fiber-matrix interfacial adhesion due to the relatively smooth and chemically inactive fiber surfaces which prevent efficient chemical and physical bonding at the interface. Surface modification of PBO fibers becomes the key for the wide application of PBO fiber.The PBO fibers were studyed by a continuous atmospheric pressure plasma treatment system (PLA-PLA). Then the modified surfaces under different plasma treatment time, power and the ratio of the gas mixture of Ar/O2 were studied by SEM, AFM, CA and IFSS. The results indicated that the contact angle of the PBO fiber decreased after the treatment. However, the contact angle increased when the treatment time was longer than 3min and the power was higher than 400W. The contact angle decreased from 84.7°to 68.38°after the treatment. The results showed that the PBO fibers became rougher after treatment and there were some pits and cracks on the surface of PBO fibers under short time and low power. However, the roughness decreased and the fiber was swelled by increasing the treatment time and power, which must be caused by the dramatic etching. Accordingly, the increase of IFSS indicated that the adhesive performance was improved under short time and low power, however, the IFSS decreased by increasing the treatment time and power. From the results of CA and IFSS, it can be concluded that the most suitable condition is 3 min,400 W and 100:1 of the ratio of Ar/O2.The duration effect of PBO fibers under plasma treatment was studied by the CA test. It showed that the contact angle increased immediately after the plasma treatment and reached a level when prolonging the storage time (when the time is longer than 65h).The change of the chemical structure of PBO fibers before and after the plasma treatment was carried out by XPS and FTIR. The ILSS of the PBO fibers/epoxy composites were examined as well. It was found that some polar groups were introduced on the surface of PBO fibers and the adhesive strength was improved after the plasma treatment (improved by 130% from 3.3 to 7.6 MPa).