Effects of a borosiloxane oligomer on the properties of anaerobic adhesive

To improve the heat-resistance of anaerobic adhesives, a borosiloxane oligomer (BSi) was directly synthesized by the co-condensation of boric acid with phenyl triethoxysilane without any external addition of water, catalyst or solvent. The BSi-modified anaerobic adhesive based on ethoxylated bisphenol A dimethacrylate was prepared. The above-prepared BSi was characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The effects of BSi modification on the bonding strength of the anaerobic adhesives were investigated using dynamic mechanical analysis (DMA), TGA, scanning electron microscopy (SEM), FTIR and strength testing. The curing behavior was evaluated using differential scanning calorimetry (DSC) analysis. The results showed that the BSi-modified anaerobic adhesive exhibited an increase in the bonding strength at room temperature. The bonding strength decreased as the testing temperature increased. However, the BSi polyblended adhesive showed a significant enhancement in the bonding strength at 400 °C because of the further formation of a Si-O-B crosslinked structure. BSi can be used as a potential heat-resistant additive that is available for threadlocking and retaining applications at 400 °C; in addition, the curing reaction of anaerobic adhesives can be promoted using BSi.