Abstract: A process for forming a foamed thermoplastic material in which a carrier member made, for example, of a vegetable material such as lignocellulose-containing fibers or cork particles, and having bonded thereto, by either capillary bonding or molecular bonding, a gas bubble forming medium, such as water or aqueous dispersions, is added to the plastic material, whereby, when the temperature of the plastic is raised above the temperature at which the medium forms bubbles, gas bubbles, are formed and form cavities in the plastic. The carrier can also act as a reinforcing agent for the plastic.