Rheological and mechanical properties of wood fiber-PP/PE blend composites

Abstract

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites (WPCs), polypropylene/polyethylene (PP/PE) blends were grafted with maleic anhydride (MAH) to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region (<0.1%). The frequency sweep results indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt.%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interfacial adhesion between wood fiber and PP/PE blends.

Keywords

wood fiber / PP/PE blends / composites / rheological properties / mechanical properties

References

[1] ASTM D790-03. Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials Annual Book of ASTM Standards, 2004 Conshohocken: ASTM International

[2] Balasuriya P.W., Ye L., Mai Y.W. Mechanical properties of wood flake-polyethylene composites. Part 1: effects of processing methods and matrix melt flow behaviour Composites: Part A, 2001, 32: 619-629.

[3] Bengtsson M., Baillif M. L., Oksman K. Extrusion and mechanical properties of highly filled cellulose fibre-polypropylene composites Composites: Part A, 2007, 38: 1922-1931.

[4] Bledzki A.K., Reihmane S., Gassan J.J. Thermoplastics reinforced with wood fillers: a literature review Polymer Plastic Technology, 1998, 37(4): 451-468.

[5] Felix J.M., Gatenholm P. The nature of adhesion in composites of modified cellulose fibers and polypropylene J. Applied Polymer Science, 1991, 42: 609-620.

[6] GB/T 1043-1993. Plastics—determination of charpy impact strength of rigid materials National Standards of PRC, 1994 Beijing: State Technical Supervision Bureau 8

[7] Hon D.N.S., Ren S. Interfacial phenomena of newspaper fiber reinforced polypropylene composite, Part I: The development of interfacial interaction J Reinforced Plastics Composites, 2003, 22(11): 957-971.

[8] Karmarkar A., Chauhan S.S., Modak J.M., Chanda M. Mechanical properties of wood-fiber reinforced polypropylene composites: Effect of a novel compatibilizer with isocyanate functional group Composites: Part A, 2006, 38: 227-233.

[9] Karnani R., Krishnan M., Narayan R. Biofiber-reinforced polypropylene composites Polymer Engineer Science, 1997, 37(2): 476-483.

[10] Lu J. Z., Wu Q. L., Negulescu I. I. Wood fiber/High Density Polyethylene composites: coupling agent performance J. Applied Polymer Science, 2005, 96: 93-102.

[11] Maldas D., Kokta B.V. Walcott M.P. Role of coupling agents and treatments on the performance of wood fiber thermoplastic composites Wood fibres/polymer composites: fundamental concepts, processes, and material options, 1993 USA, Madison: Forest Product Society 112-120.

[12] Marcovich N.E., Reboredo M.M., Kenny J., Aranguren M.I. Rheology of particle suspensions in viscoelastic media. Wood flour-polypropylene melt Rheologica Acta, 2004, 43: 293-303.

[13] Nunez A.J., Sturm P.C., Kenny J.M., Aranguren M.I., Marcovich N.E., Reboredo M. M. Mechanical characterization of polypropylene wood flour composites J. Applied Polymer Science, 2003, 88: 1420-1428.

[14] Oksman K., Clemons C. Effects of elastomers and coupling agent on impact performance of wood flour filled polypropylene J Applied Polymer Science, 1998, 67(9): 1503-1513.

[15] Zadorecki P., Michell A.J. Future prospects for wood cellulose as reinforcement in organic polymer composites Polymer Composites, 1989, 10(2): 69-77.