Incorporation of flame retardancy in bio‐resourced mannitol based curing agent for clear pressure‐sensitive adhesive

Abstract

Recently, the flame retardancy of the pressure‐sensitive adhesive acquired a large amount of research interest because of their ability to cease the effect of fire on products, which are widely used for high‐temperature applications. The current study comprises the addition of the phosphorus modified mannitol (PMM) in a clear acrylic pressure‐sensitive adhesive (CPSAs). Mannitol indulges the replacement of the petroleum‐based crosslinking agent used for CPSAs, and phosphorus modification imparts the inherent flame retardancy. The process includes two parts, the first part comprises the conversion of D‐mannitol into 2,4:3,5‐di‐O‐methyl‐D‐mannitol followed by the modification through phosphorus oxychloride (POCl3) and the second part includes the addition of the PMM in CPSAs. The qualitative analysis of the formed compound was done with Fourier transform infrared spectroscopy (FT‐IR), and nuclear magnetic resonance spectroscopy (NMR). To understand the dependency of the PMM dose on adhesive performance, glass transition temperature (Tg) was measured through dynamic mechanical thermal analysis (DMTA). The performance of adhesive was evaluated by determining optical and adhesion properties such as refractive index, impact resistance, peel strength, the probe tack, and the shear adhesion failure temperature. Thermogravimetric analysis (TGA) was used to understand the thermal degradation of the adhesive. Successively, it was observed that the Tg and other properties are the functions of PMM concentration. Adhesive shows the excellent flame retardancy with maximum limiting oxygen index (LOI) value of 48 and a self‐extinguishing behavior, as confirmed by the UL‐94 test. The extinguishing of the fire occurs with the formation of the 0.9 to 6 mm char with a closed cell‐like structure confirmed through SEM.Highlights Research involves the preparation of phosphorus modified curing agents of bio‐based resources and understand in the application in the clear pressure‐sensitive adhesive. A bio‐based curing agent has synergic behavior of flame retardancy. The use of a bio‐based curing agent imparts thermal stability in the adhesive. The presence of phosphorus in the structure allows the formation of intumescent char.