Generation Of Pvc Polymerization Of Xylene Film Deposition And Annealing Studies

Much attention has been focused on the applications of the poly(chloro-p-xylylene), or named as PPXC films in semiconductor, microelectronics, sensor, magnetism materials, because of their excellent physical and mechanical properties, high solvent resistance, low dielectric constant, good barrier properties, biocompatibility. PPXC films are widely utilized as the moistureproof coating for microelectric devices, solid particles, historical materials and books because of their excellent moisture and gas insulation properties.There are some reports on the preparation and applications of PPXC films. However, a basic understanding is needed to correlate the structure and physical and mechanical property, permeation property in order to fully exploit the properties of the PPXC films. PPXC films were prepared through chemical vapor deposition method. The deposition pressure, the substrate temperature have dominant effects on the depositon rate, microstructure and properties of the films. In this paper, PPXC films were prepared at different deposition pressure, substrate temperature. Some films were annealed in the argon and air atmosphere at different temperature and time. Crystallinity, microstructure, thermal properties and moisture permeation rate of films were analyzed by X-Ray Diffraction(XRD), Scan Electron Microscope(SEM), Polarized Optical Microscope(POM), Fourier Transform Infrared Spectroscopy(FT-IR), Thermogravimetry(TG), Differential Scanning Calorimetry(DSC), Pyrolyzate Mass Spectrometer (PMS), Water Permeation Instrument, et al. The results showed as follws.Deposition rate, crystal morphology, microstructure are effected obviously by the deposition pressure and substrate temperature. Deposition rate of PPXC fims increases with the increase of deposition pressure, the decrease of substrate temperature obviously when the sublimation temperature, pyrolysis temperature are invariable. The crystal structure of films was monoclical a phase under different conditions. Polymer molecule chains align more regular at lower deposition pressure, and the degree of relative crystallinity of films is much higher. As the substrate temperature is increased, the morphology of crystal partical turns from irregular polyhedron to spherical, and the size of particals increass initially, decreases later. The (020) diffraction plane dominanted when the substrate temperature was more than 30°C, that is to say, The plane of the phenyl group oriented more perpendicular to the plane of the substrate during vapor deposition polymerization at the higher substrate temperature.The physical and mechanical properties, thermal stablility, moisture permeation property of PPXC films vary with the variation of crystallinity and microstructure. The tensile strength, the thermal degradation temperature of films increase with the increase of degree of crystallinity. The crystallinity of films prepared at the relative higher pressure is lower, and the protion of the freedom space between molecule chains is higher, which lead that moisture diffuse more easier through the films. Mositure permeation rate decrease initially, then increased with the increase of substrate temperature, and the minimum is obtained at approximate 30℃.There are two processes during annealng of ppxc films in the atmosphere of both argon and air. The first is the process of crystallization, and the second is the process of thermal degradation. Polymer molecular chains can be broken during long period of annealing in argon because of heat energe, however, the films degrade at a more severe degree because of their oxidation in the air.The crystallinity of ppxc films can be improved with the increase of anneal temperature in the both of argon and air, which don't change their crystalline state. The rate of crystallization in the argon is slow, compared with in th air, but the degree of crystallization of films is more high.The tensile strength, moisture permeation property, thermal stability of PPXC films are effected by the microstructure of films. The variation of the tensile strength and the moisture permeation property are effected by the phase, in which films experience crystallization or degradation. The tensile strength and moisture and gases insulation properties of films increase gradually in the initial period of time, when films are at the process of crystallization. Then the tensile strength and moisture and gases insulation properties of films begin to decrease when the process of crystallization is completed, followed by the oxidation and degradation. The trendency of the variation in the argon is smaller, compared with in the air. The thermal stability of PPXC films can be improved through isothermal annealing under two atmospheres.