Use of Preimpregnated Sisal Yarn in Woven Reinforced Polypropylene Sheets: Thermoformability and Mechanical Properties.

L.M. ARZONDO, C.J. PÉREZ

POLYMER ENGINEERING AND SCIENCE

Wiley

Año: 2005 vol. 45 p. 976 - 983

0032-3888

Thermoplastic composites were made from polypropylene (PP) and long sisal fibers (SF) by using different processing techniques. Four sets of composites specimens were made with a 60/40 (wt/wt) SF/PP ratio: one first set was made by melt blending PP and SF and compression molding 2 mm thick flat sheets; a second set was made by melt blending PP, SF and maleic anhydride grafted polypropylene (MA-g-PP); the third set was made by compression molding knitted SF yarns -pre-impregnated with PP- between PP sheets; the fourth set was also made by compression molding knitted SF yarns -pre-impregnated with diluted MA-g-PP- between PP sheets. The bi-directional array of fibers -containing 60 % of SF well impregnated with a small quantity of MA-g-PP- increases the flexural modulus by 600 %, the tensile modulus by 475 % and the tensile strength by 300 % compared with unfilled PP. The composites sheets were successfully thermoformed with small wall thickness reductions to obtain a 3D shape with very low forming energy, outstanding mechanical properties, and excellent surface finish.