Plasma enhanced chemical vapor deposition of SiO_x coatings for gas diffusion barrier enhancement of flexible polymerized compounds

摘要

Airco-Coating Technology(ACT)has developed production-scale,plasma enhanced chemical vapor deposition(PECVD)SiO_x coating equipment for flexible food packaging.In 1987 ACT began the development of this process to reduce the oxygen and water vapor transmission rates of plastics by coating 10 cm x 10 cm polymer sheets in a 0.3 m wide coater at 0.3 m/min.ACT has scaled-up this process to 1.5m wide widths at web speeds up to 100 m/min.ACT's SiO_x coatings decrease the oxygen transmission rate(O2TR)on polyethylene terepthalate)(PET),low density polyethylene(LDPE),oriented polypropylene(OPP),and biaxially oriented nylon(BON)by typically more than two orders of magnitude.A statistical process control(SPC)chart shows the O2TR of ACT's SiO_x coated PET rolls,coated on a research and development coater,is in control and has a mean permeation rate of 0.9 cmVmVday with an upper control limit(UCL)of 1.0 cmVmVday.A similar SPC chart for H2OTR has a mean of 1.5 cmVmVday with an UCL of 2.3 cmVmVday and LCL of 0.7 cmVmVday.ACT developed a new coating characterization test to predict durability in which coated polymers were progressively stretched and the O2TR was measured at each stretching step.These stretching tests show that the high gas diffusion barrier PECVD SiO_x films on PET can be stretched to a greater extent before the O2TR increases,compared with evaporated coatings of SiO_x and Al2O3.