Hydrolytic Stability of 3-Aminopropylsilane Coupling Agent on Silica and Silicate Surfaces at Elevated Temperatures

Abstract

3-Aminopropylsilane (APS) coupling agent is widely used in industrial, biomaterial, and medical applications to improve adhesion of polymers to inorganic materials. However, during exposure to elevated humidity and temperature, the deposited APS layers can decompose, leading to reduction in coupling efficiency, thus decreasing the product quality and the mechanical strength of the polymer-inorganic material interface. Therefore, a better understanding of the chemical state and stability of APS on inorganic surfaces is needed. In this work, we investigated APS adhesion on silica wafers and compared its properties with those on complex silicate surfaces such as those used by industry (mineral fibers and fiber melt wafers). The APS was deposited from aqueous and organic (toluene) solutions and studied with surface sensitive techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), streaming potential, contact angle, and spectroscopic ellipsometry. APS configuration on a model silica surface at a range of coverages was simulated using density functional theory (DFT). We also studied the stability of adsorbed APS during aging at high humidity and elevated temperature. Our results demonstrated that APS layer formation depends on the choice of solvent and substrate used for deposition. On silica surfaces in toluene, APS formed unstable multilayers, while from aqueous solutions, thinner and more stable APS layers were produced. The chemical composition and substrate roughness influence the amount of deposited APS. More APS was deposited and its layers were more stable on fiber melt than on silica wafers. The changes in the amount of adsorbed APS can be successfully monitored by streaming potential. These results will aid in improving industrial- and laboratory-scale APS deposition methods and increasing adhesion and stability, thus increasing the quality and effectiveness of materials where APS is used as a coupling agent.

Towards greener stone shot and stone wool materials: binder systems based on gelatine modified with tannin or transglutaminase

“…Various silane-type coupling agents such as 3-aminopropylsilane are typically employed in combination with conventional binder systems to improve the adhesion to the inorganic stone surface. 27 Nevertheless, irreversible losses of around 30-50% of the initial strengths are commonly observed for these binder systems after ageing treatment as mentioned above. These strength losses become even more pronounced in the absence of the coupling agents.…”

Quantification of amine functional groups on silica nanoparticles: a multi-method approach

“…Silica functionalization by reaction of aminoalkylalkoxy silanes with silanols is widely used but known to suffer from challenges associated with polymerization of the initial silane in solution, possible formation of heterogeneous multilayers on the surface in the presence of excess silane and the lack of stability of the aminated surfaces. [21][22][23] In the present study we compare the results from two colorimetric assays for quantication of accessible surface amines to results obtained by labeling amines with tri-uoromethylated probes that provide high sensitivity for XPS and quantitative solid state 19 F NMR. 2,5,19,24,25 The two colorimetric assays are based on the reaction of ninhydrin with primary amines to generate a dye that is released from the surface and quantied in the supernatant and the reaction of an aldehyde with surface amines to generate an imine product that can be cleaved for quantication aer isolation of the NPs.…”

Impact of curing time on ageing and degradation of phenol-urea-formaldehyde binder

“…If detachment of PUF was caused by decomposition of bonds only between PUF and APS, which M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 23 would leave APS molecules on fiber surfaces, the IEP would shift to high pH because of APS basic amino groups. Previously, it was shown that APS coupling agent layers are not stable under the ageing conditions used in this study 12,13 . Figure 8.…”

“…In the case of mineral wool production, 3-aminopropylsilane (APS) coupling agent is used to enhance PUF adhesion to the mineral fiber surfaces 2 . APS reacts with mineral wool 12,13 or glass fiber [14][15][16][17][18][19][20][21] surface through silanol groups, -Si(OH) 3 , and with the polymer matrix 22 through its amino group -NH 2. This allows binding of mineral fibers together ( Figure 1) and creates the necessary mechanical properties for the mineral wool product, when the PUF binder is cured 2 . However, reactions between the silanol group of APS and polymer matrix have also been described [23][24][25] .…”

“…After ageing in the water bath or in the climate chamber, IEP for the mineral wool shifts toward lower pH. The surface of the untreated mineral wool fibres, that have not had oil added, has IEP close to pH 4.5 13 , thus the decrease of IEP after ageing indicates that the surface becomes more acidic, because of -SiOH terminations on the basaltic glass surface similar to glass fibers 19 . Therefore, the reason for the shift of IEP after ageing for the mineral wool fibers covered with PUF, from pH 4.5 toward pH 4, can be PUF detachment from fiber surfaces, which is indicated by XPS results, where C:Si and N:Si ratios decrease.…”