Plasticiser migration is a huge topic, but as we are The Glue People, this article is just focussed on the bonding of plasticised PVC, or Vinyl as it is more commonly known.
To make unplasticised PVC (uPVC) into something more flexible, a plasticiser is added during the manufacturing process. Generally speaking the more flexible a material is, the more plasticiser it will contain.
These plasticised vinyls can be used for vinyl flooring, door cards and other trim in vehicles including seats, household furniture, truck curtains, hoses, rigid inflatable boats (RIBs), tents & marquees, banners & signage, etc.
Plasticiser migration is the unwanted movement of a plasticiser component out of a substrate (e.g. vinyl, PVC, etc) into the glue-line. If conditions allow, the migration will start, leaving the vinyl a bit less flexible, and the glue a bit more. If it continues, the glue line will get softer and softer and eventually can turn back into a liquid, causing a bond failure. When pulling the vinyl from the substrate, the adhesive will ‘string’ as if it hasn’t cured, this is a sign of plasticiser migration. The vinyl can also get less flexible, change colour and in extreme cases can split.
Some adhesives are very good at stealing the plasticiser from the vinyl. The speed and amount of migration depends on the type of adhesive, ambient heat, amount of plasticiser in the vinyl, heat resistance of the adhesive and the quality of the backing material if there is one. Adhesives based on SBR (styrene butadiene rubber) are generally the quickest at migrating the plasticiser and a basic aerosol upholstery adhesive bonding a non backed vinyl into a vehicle left in the sun, can cause problems within a few days. A high quality, high heat, hand applied polychloroprene such as Tradegrip HH on a well backed vinyl like the vinyl roof on a car, can last for years but can suffer from plasticiser migration eventually. Saying that, Trade Grade’s own classic car, a Rover P6, had the vinyl roof bonded with Tradegrip HH in February 2012 and is still perfect in 2023.
The fastest plasticiser stealers are low heat resistance SBRs such as economy aerosols, then higher grades of SBR, followed by polychloroprenes (often called Neoprene). The higher the heat resistance of these two, the better they are at resisting the migration of plasticisers from the substrate. Acrylic adhesives are not as strong, but do not cause plasticiser migration, and also Polyurethanes (both solvented contact types, and moisture curing) and Nitrile contact adhesives are very good at resisting migration.
We have many adhesives in our range with varying degrees of plasticiser resistance but for the highest level of resistance we would make the following recommendations: