Bac2 paper at ‘Composites Innovation 2012’ shows how latent catalyst cuts energy and boosts productivity in resole processing
Southampton, UK, July 03, 2012: Bac2, the polymer materials company, has developed a white paper that describes how the use of a novel latent acid catalyst can cut energy requirements and improve both yield and storage stability in the manufacture of resole-based products. The paper will be presented by the company’s CTO, Dr. Graham Murray, as Composites Innovation 2012, 4-5th July, 2012, National Composites Centre, Bristol, UK.
Despite their superior fire properties, phenolic resole based sheet moulding compounds (SMC) are not commonplace due to poor storage and processing. Phenolic SMC is produced using liquid resole resins, chopped glass and filler sandwiched between an upper and lower protective film. The resin layer must thicken during storage to allow ease of cutting and handling at the moulders. Metal oxide is added to thicken the resin but the resulting sheet has to be stored below 0°C because the sheet becomes unusable if left at room temperature for more than a few days. Bac2 has developed novel latent acid catalyst systems for use in the production of resole-based products in applications such as abrasives, pultrusion, adhesives and moulding products including BMC and SMC.
The novel feature of patented CSR latent catalysts is the use of hydroxylamine as the base in association with a strong acid to give a stable adduct. Unlike all other bases, hydroxylamine is thermally unstable and decomposes around 120°C producing gaseous decomposition products and water vapour, leaving the acid completely free to begin the catalysis. By controlling the ratio of acid to hydroxylamine, a wide range of reactivities and tight control of storage stability can be achieved.
When used in the SMC production process, the CSR catalysts enable phenolic SMC to be formed into rolls that thicken via a pseudo B-stage and require no cold storage. The pseudo B-stage thickening step is achieved without the need for metal oxide additives and after a few days at room temperature the SMC is at a consistency that allows easy cutting, stripping and moulding of GRP parts. The rolls can be stored at ambient temperature for up to 2 months. The sheets are cut to size and compression moulded at temperatures between 120°C and 150°C with minimal breathing required. Mechanical and fire properties are excellent for the newly-developed phenolic moulded parts.
CSR catalysts demonstrate that, for the first time, a phenolic option for storage stable SMC is available and can produce, at high volume, mechanically strong, fire safe products.