Coating of polymers with titanium-based layers by a novel plasma-assisted chemical vapor deposition process

Chemical vapor deposition (CVD) is an excellent technique to coat complex substrates like fibers or inner surfaces of tubes. However, CVD often suffers from high coating temperatures which makes it impossible to coat temperature-sensitive materials like polymers, e.g. with titanium-based layers. A new plasma-assisted CVD (PACVD) process has been developed to coat polymers at very low temperatures with titanium-based layers. The coating temperature could be lowered to approximately 60 degreesC (140 degrees F), so that a variety of different polymers can be coated without undesired damaging. In this work, polyethylenetherephthalate (PET), polyethersulfone (PES), polyvinylchlorine (PVC), polytetrafluoroethylene (PTFE), polyethylene (PE) and polypropylene (PP) have been used. Very smooth (R-a = 3 mm) and thin (5-100 nm) layers show a very good adherence (>10 N/mm(2)) when examined using tensile tests. It could be demonstrated that all kinds of geometries such as tubes or textile structures can be coated. The coating has the huge potential to improve the bio- and bloodcompatibility of polymers for medical devices. This could be shown by a significant higher cell vitality and growth of the cells on Ti(C,N)-coated polymers compared with uncoated polymers (using fibroblasts and endothelial cells). Moreover, the coagulation of blood is less effected if polymers are coated with the Ti(C,N) layers. It could be demonstrated, that the Ti(C,N)-coating is an effective diffusion barrier to prevent leaching of plasticizers or additives, e.g. from PVC which is advantageous for many medical devices as well as for a lot of other applications where PVC is used. Besides the medical applications many other improvements of polymers are possible by this new coating process. Examples are surfaces with a higher wettability, corrosion stability or electrical conductivity. (C) 2000 Elsevier Science B.V. All rights reserved.