Surface Plasma Modification of LLDPE for Biomedical Applications

Linear low density polyethylene (LLDPE) surface was modified by water plasma treatment to functionalized with oxygen-containing functional groups and to improve wettability. The LLDPE surface was treated at 10 and 20 W discharge power at various exposure times. A laboratory scale Megatherm radio frequency (RF) plasma apparatus that operates at 27 MHz was used to generate the water plasmas. Comparative studies were also made on LLDPE by using Argon plasma discharge followed by exposure to oxygen. The changes in chemical structure of the LLDPE polymeric chain upon plasma treatment were characterized by FTIR and XPS techniques. The selectivity of trifluoroacetic anhydride (TFAA) toward hydroxyl groups is used to quantify the hydroxyl groups formed on the polymer surface upon plasma treatment. The surface wettability of the samples was evaluated by measuring water contact angle of the samples before and after modification. In an attempt to understand the effect of surface modification of polymers on organopolysiloxane coating, selected samples were coated with SIGMACOTE. After exposition to the plasma discharge a decline in water contact angle were observed. FTIR and XPS measurements indicate an oxidation of degraded polymeric chains and creation of hydroxyl, carbonyl, ether, ester and carboxyl groups. Chemical derivatization with TFAA of water plasma treated polymer surfaces has shown that under the conditions employed, a very small (less than 5%) of the oxygen introduced by the water plasma treatment was present as hydroxyl group. The XPS results revealed that, under the plasma condition utilized, the surface modification of LLDPE using water plasma improves the wetting of polysiloxane onto the LLDPE surface.