Mechanistic studies of adhesion promotion by γ‐aminopropyl triethoxy silane in α‐Al₂O₃/polyethylene joint

Abstract

In order to understand the mechanism of adhesion promotion by organo silane in joints where its chemical reaction with a polymer matrix may be negligible, we studied the role of γ‐aminopropyl triethoxy silane (γ‐APS) in α‐Al2O3/ polyethylene joints. When adsorbed or deposited on α‐A12O3/ and moderately dried, γ‐APS forms a multimolecular film that is not fully cured. Drying at elevated temperatures for an extended time leads to further curing, resulting in a glassy silane film with a Tg around 108°C, while prolonged dry may cause some degradation. Joint strength is markedly improved by the application of a γ‐APS film with a maximum peel strength of 2.3 kg/cm when the silane is applied from a 2 percent aqueous solution. Drying the silane at an elevated temperature prior to joint formation reduces joint strength and also changes the failure mode from cohesive failure through the polyethylene to a mixed mode. Evidence of interdiffusion between γ‐APS film and polyethylene at a temperature (149°C) that is above the melting point of polyethylene and the Tg of the silane film was obtained by measuring the Si concentration profile across the interface of the laminate of polyethylene/γ‐APS/polyethylene. Diffusion constants in the order of 10−12 cm2/s were obtained, with a teridency toward reduced diffusion as a consequence of extensive drying. DSC results indicate at least partial miscibility of the silane polymer in the amorphous region of polyethylene. It is proposed that the interdiffusion between γ‐APS silane film and polyethylene is an important mechanism for adhesion promotion of the joints investigated in this study.

Retention of poly(N-isopropylacrylamide) on 3-aminopropyltriethoxysilane

“…7,15,16,18,29,30 B. Retention of the pNIPAAm film and PS on the APTES layer When pNIPAAm films ($30 nm) were placed on top of the APTES layers and allowed to interdiffuse at 160 C ($25 C above the T g of pNIPAAm) for 3 days, pNIPAAm retention on the APTES layers was clearly evidenced as shown in Fig.…”

“…for the advancing and static angles, respectively), especially the receding angles (reduced by 30 ), for all the APTES layers [ Fig. 2(b)].…”

The adhesion promotion mechanism of organofunctional silanes

“…They found interfacial toughness to increase with chain length and dedrying temperature may restrict interdiffusion with the polymer and limit formation of an IPN, crease with areal attachment density, attributing the former to increased molecular penetration resulting in a corresponding drop in bond strength with increased drying temperature. 3,4,6 Compatiand the latter to exclusion of the polymer chains with high areal density. bility between the silane organofunctional group and polymer is an important consideration, as recThese studies support an argument that the adhesion promotion comes about from chemical ognized by Plueddemann 1 and studied by Gentle and colleagues, 8 who investigated the relationcompatibility between the silane organofunctional group and the corresponding penetration ship between the penetration distance and similarity in solubility parameter between the silane into the polymer.…”

“…14 Lin and colleagues 15,16 attached polymeric chains to glass fibers, discondensation reactions to produce a more highly crosslinked matrix and corresponding reduction persed the fibers in a polystyrene matrix, and studied the effects of tethered chain length and in film thickness with increasing drying temperature. 3,[5][6][7] The increased crosslinking with higher areal attachment density. They found interfacial toughness to increase with chain length and dedrying temperature may restrict interdiffusion with the polymer and limit formation of an IPN, crease with areal attachment density, attributing the former to increased molecular penetration resulting in a corresponding drop in bond strength with increased drying temperature.…”

“…Previous workers and colleagues 13 attempted to enhance the yield strength of a flax fiber/polypropylene layered have reported that the adhesion promotion is due to interdiffusion of the polymerized silane film and composite by treating the fibers with silanes featuring nonpolar organofunctional groups of varypolymer, and the resulting formation of a so-called ''interpenetrating polymer network'' (IPN). [1][2][3][4][5] ing length to match the nonpolar polymer matrix. Despite the nonpolar nature of both silane and They conclude that the silane must be applied in amounts sufficient to produce a silane film of fipolymer, the composite yield strength was not improved, and there was no dependence on organonite thickness (multiple monolayers) that can interdiffuse with the polymer and increase bond functional group length.…”