Adhesion of Photopolymer Materials to Thermoplastics and Thermosets: Solubility Parameters, Interdiffusion, Primers and Ageing

Adhesion of a photocurable material to a thermoplastic or thermoset depends on the state of both polymeric materials and the interphase produced between them. Surface energy and solubility parameters can screen candidate pairs, but they do not measure swelling, dissolution, interdiffusion, primer anchoring, cure arrest, environmental stress cracking or durable joint performance. A treatment that initially improves wetting can recover, contaminate or damage the substrate before bonding. This review defines a polymer-substrate qualification architecture. It requires polymer identity, grade, additives, crystallinity or cure state and prior ageing; separates thermodynamic screening from direct interdiffusion and mechanical evidence; records activation-to-bonding delay and hydrophobic recovery; verifies primer anchoring independently from adhesive-facing function; and resolves failure locus before and after environmental conditioning. The evidence supports substrate-family decision maps and shows why contact angle, surface energy, nanoscale adhesive work, peel and lap shear are non-equivalent. It does not establish a commercial treatment or primer recipe, universal Hansen or Hildebrand distance, surface-energy target, activation window, diffusion coefficient, adhesion threshold or ageing factor.