A Simple Approach to Synthesize and Bond Organosiloxane Films on Injection-Molded Polyolefins

Abstract

A simple method was devised to fabricate and anchor organosiloxane coatings along low-surface-energy plastics without resorting to chemical pre-treatment of the polymer surface. Polypropylene tubes were purposely distended by exposure to toluene-based solutions. An established solvent of many organic polymers and compounds, toluene not only perfused into the plastic via gradual intercalation of accessible polymer chains, but it also facilitated the entry of less compatible reagents as co-perfusates. The reagents, typically aminoalkyl si lanes, were activated either concomitant to perfitsion of polypro-pylene or during a subsequent hydrolysis step. Freed silanol groups, interacting along and beneath the Surface of the plastic, reacted to form a network held together by siloxane bonds. The type of network formed and presented herein was interpreted as an amorphous aminopropylsiloxane-silanol hydrate film, with overall thickness partially submerged and caught in the matrix of the plastic. This concept to intertwine a growing organosiloxane network and a compliant matrix precluded the conventional methods normally used to improve bonding on hydrophobic plastics. A comparison of ninhydrin color yields suggested that films were more effectively and conveniently synthesized when aminopropyltri-methoxysilane was applied in water-saturated toluene. It follows that by integrating low-temperature hydrothermal processing into this strategy, inorganic-organic hybrids or inorganic oxide films may be formed oil pre-molded plastics and feature traits such as covalent-like fastness and gas impermeability.