Oil-based acrylic adhesives are widely used in electronic packaging, power batteries, label tapes, and other fields, but their limiting oxygen index is relatively low, making them difficult to self-extinguish when exposed to fire, and they cannot meet the UL94 V-0 flame retardant requirement. To make oil-based acrylic adhesives reach the V0 rating, the key lies in the precise coordination of flame retardant selection, dosage, and dispersion process.<\/p>\n
In terms of flame retardant selection, phosphorus-nitrogen halogen-free flame retardants are currently the mainstream solution. Its flame retardant mechanism is that upon heating it decomposes to generate phosphoric acid derivatives, catalyzing the dehydration of acrylic resin into char, forming a dense char layer that isolates oxygen and heat; the nitrogen component releases inert gas to dilute the concentration of combustibles. Traditional brominated flame retardants have gradually been phased out due to environmental risks. Hongtaiji Company's FR-131A is a phosphorus-nitrogen halogen-free flame retardant developed specifically for oil-based acrylic coating products. It appears as a white powder, with phosphorus content >=18.5% and nitrogen content >=19.5%, and an average particle size D50<=5.0\u03bcm, enabling single-sheet products to achieve UL94 V-0 flame retardant rating.<\/p>\n
In terms of dosage, depending on the system formulation, the flame retardant dosage for oil-based acrylic adhesives is generally 30%~43% of the adhesive amount. Under the condition of a total tissue paper thickness of 100 microns, usually adding 25-35% can achieve the V0 rating. It is worth noting that the addition of flame retardant will reduce properties such as initial tack and peel strength by about 10%, and the balance needs to be tested in the actual formulation.<\/p>\n
In terms of process, because the flame retardant is in powder form, directly adding it to the adhesive tends to cause agglomeration. The correct operation is to first wet and disperse the flame retardant with a solvent (such as toluene, ethyl acetate), stir thoroughly, and then add it to the adhesive system to ensure uniform dispersion. Hongtaiji recommends conducting a small-scale test first and determining the precise dosage with effect testing. In addition, the flame retardant particle size needs to be controlled below 5\u03bcm; if the particle size is too large, it will lead to a rough coating surface or uneven flame retardancy.<\/p>\n