Effect of RF-plasma deposition parameters on the composition and properties of organic layers deposited on glass fibers

Thin films were deposited from vinyltriethoxysilane (VTES) and tetravinylsilane (TVS) by radio frequency (RF) cold plasma operated in a pulsed mode on the surface of E-glass fibers. Film thickness and molecular structure was controlled by the length of plasma cycle expressed as ratio of time on/time off (ton/toff). It was found that ton as short as 1 ms was long enough for vinylsilane precursor gas fragmentation. Time toff was the main parameter controlling structural variables of the deposited films. Short toff led to apparently disordered and cross-linked structure. Increased toff led to more uniform films with enhanced properties compared to the short toff deposited films. Only films prepared under long toff improved adhesion between the glass fiber and polyester resin as measured employing the micro-droplet test. Strong effect of the molecular structure of the vinylsilane precursor has also been observed under the conditions used. VTES film deposited under ton/toff = 1:999 increased interfacial adhesion only by 20%, TVS film deposited at 1:99 improved adhesion by 48%, compared to the solution deposited coating of the VTES used commercially.