Interfacial adhesion of pine wood filled PP compounds via effects of volatile extractives

Effects of volatile extractives in pine wood (PW) particles are investigated upon interfacial adhesion, nucleation behavior and mechanical properties in polypropylene (PP) matrix. Various concentrations of the PW are filled in PP, i.e. PP/PW [90/10 (PP10), 75/25 (PP25) and 50/50 wt% (PP50)]. As the concentration of the PW particles is increased, the crystalline peak temperature is increased, the melting peak temperature is decreased, the elongation strain is decreased and the amount of volatile extractives in the PW is increased. Few spherulites are locally developed at the interface between the PW and the PP. The PW acts as a nucleating agent; however, it does not help reinforcing of the PP/PW compounds. The volatile extractives in the PW particles seems to evaporate- and migrate-out during the processing and then coats the pine wood surface, trapped in the compound, and migrats out to the wall surface. This results in a poor interfacial adhesion between the PW and the PP.