Thickness swelling of the wood-PP composites has a similar trend as the water absorption and composites
with high water absorption also showed higher thickness swelling.
The thickness swelling values for the 2 h immersion varied from 0.01 to 0.32%, and these values are
increased after 24 h immersion, varying from 0.02 to 1.21% depending on the composite formulation.
Samples made with lower content of wood flour have the lowest thickness swelling as for the water
absorption. However, MAPP coupled composites showed less thickness swell than composite samples
without the coupling agent at the same wood content. In general, the composite made of virgin and recycled
PP has similar dimensional stability properties without adding the coupling agent. However, the stability
properties of these composites are improved by adding 3-5 wt. % MAPP coupling agent. The impact of