in situ composite formation

https://doi.org/10.1351/goldbook.IT07624
Process for preparing a polymer composite by
  1. forming the filler or reinforcement in an existing polymer or
  2. polymerizing monomers in the presence of dispersed filler.
Source:
PAC, 2007, 79, 1801. 'Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007)' on page 1823 (https://doi.org/10.1351/pac200779101801)