Bonding SAN (Styrene-Acrylonitrile)
What is SAN?
SAN is a type of plastic material based on styrene chemistry. It is similar to polystyrene but has improved temperature performance, chemical resistance and toughness. It is sometimes blended with other plastics such as ABS. It can also contain fillers such as glass fibre to help strengthen it but in its normal state it is fairly brittle. Luran® SAN and Lustran® SAN are popular tradenames.
Where is SAN used?
Common applications include food processor bowls, salad crispers in refrigerators, disposable medical devices and viewing window on meters to name a few. It has high optical clarity but is also available as opaque/ coloured material.
Surface preparation and adhesive selection to bond SAN
SAN is normally easy to bond with industrial adhesive in its “as received” condition. In fact, using cleaners, solvents or primers can be detrimental – the substrate can become weakened or stress cracked. For this reason, it is a good idea to select an adhesive that cures rapidly to minimise risk of uncured adhesive attacking the SAN. How to bond SAN?
UV cure adhesives are ideal as they give excellent optical clarity and cure fully in seconds on exposure to UV light, opt for a clear grade with longer wavelength photoinitiators. This will allow the adhesive to cure even if the SAN is UV stabilised.
2-part epoxies and 2-part polyurethane industrial adhesives can be considered, try to choose a fast curing grade to minimise risk of stress cracking and make sure the adhesive is properly mixed in the correct mix ratio. Single part heat cure epoxies are probably unsuitable due to the high temperature cure (SAN softens at about 105°C so it would be advisable to cure at a lower temperature).
Toughened, structural acrylic industrial adhesives could be considered, but steer clear of the no-mix resin and brush on initiator systems as surplus initiator could attack the SAN. Use a system with a proper mixing nozzle (rather than bead-on-bead) to make sure all adhesive is 100% reacted. Crystal clear structural acrylic adhesives would make a good choice for bonding SAN.
In every case, it is important any surplus adhesive be removed ASAP and allow the bonded assembly to ventilate properly before bagging and sealing.
Luran® SAN and Lustran® SAN tradenames of INEOS ABS (USA) CORP and INEOS-BASF.