Moisture absorption and mechanical properties of chemically modified linen/polypropylene composites

To decrease the moisture absorption and improve the mechanical properties of linen/polypropylene(PP) composites, linen was modified with silane N-[3-(trimethoxysilyl) propyl]ethylenediamine(AAPTS), surfactant tri-methyloctadecylammonium bromide(STAB), and both AAPTS and STAB, respectively. Fourier transform infrared(FTIR) spectra showed that the linen was successfully modified and alkyl chains were attached through different treatments. The linen and PP were compounded by melt compressing. The moisture absorption of linen was decreased after STAB and AAPTS-STAB modifications. The moisture absorption, mechanical property and thermal property of the composites were also characterized. The results show that the moisture absorption of the AAPTS-modified linen(F1) reinforced PP(PPF1) is 8.09%, which is higher than that of the unmodified linen reinforced PP(PPF)(7.89%). The moisture absorption of the STAB-AAPTS-modified linen(F3) reinforced PP(PPF3) is 6.58%. The tensile strengths of PPF1 and PPF3 are 33.7 and 35.8 MPa, which are improved by 22.5% and 30% compared with that of PPF(27.5 MPa), respectively. Nevertheless, the moisture absorption of the STAB-modified linen(F2) reinforced PP(PPF2) is decreased by 22.4%, and the tensile strength is improved by 30% compared with those of PPF. Scanning electron microscopy(SEM) analysis of the fractured surface confirms the good interfacial adhesion of PPF2 compared with those of other composites. Furthermore, the 5% mass loss temperatures of the composites are all higher than 290 °C. Thus, linen modified with STAB is a promising reinforcement for biocomposites.