Surface Energy Compatibilites of Cellulose and Polypropylene

Abstract

In addition to its use in recycled paper products, recovered lignocellulosic fiber can be used as a reinforcement filler in composites with polyolefins. However, problems in both processing and product performance are often caused by the incompatibilities of surface energies between hydrophilic cellulose and non-polar polyolefin. This poor match in surface polarities is detrimental to strong adhesive bonding between olefin and cellulose. This work examines the effect of surface energy on the adhesion properties of polypropylene and cellulose. In particular, three materials accepted as paper-sizing agents were used to change the cellulosic fiber's surface energy to make it more compatible with the surface energy of polypropylene.Cellulose fibers were treated by various methods with (1) alkyl ketene dimer, (2) alkenyl succinic anhydride, and (3) stearic acid and were characterized by their surface energies as determined by single fiber wettability measurements using the Wilhelmy technique. These measurements are discussed in detail. Results from these measurments can be related to differences in adhesion between treated cellulose and polypropylene, which can be measured by internal bond tests on hot-pressed composite sheets.Results indicate that the use of sizing agents reduces the acid/base (hydrogen bonding) character of the cellulose surface. Interactions involving hydrogen bonding are important in cellulose/modified-polypropylene composites. Reduction of these interactions appears to lead to a corresponding reduction in adhesion between cellulose and polypropylene.

Effect of fibre orientation on the mechanical properties of polypropylene–lyocell composites

“…Natural and regenerated fibre reinforced polymer composites also have some disadvantages such as the low adhesion between the hydrophilic natural fibres and the hydrophobic polymer matrix (Bledzki and Gassan 1999). In the literature, physical and chemical surface treatments of the reinforcing natural fibres are described to improve the adhesion between fibres and matrix (Belgacem et al 2003;Gray 2008;Joly et al 1996;Qiu et al 2003;Quan et al 2005;Quillin et al 1992Quillin et al , 1993. For example the hydrophilicity of polypropylene (PP) can be increased by modification with maleic anhydride, resulting in an improved adhesion between the matrix polymer and natural fibres (Bataille et al 1989;Joseph et al 2003;Khalid et al 2006;Shubhra et al 2011;Spoljaric et al 2009;Qiu et al 2005Qiu et al , 2006.…”

Structural Insights into LDPE/UHMWPE Blends Processed by γ-Irradiation

“…The liquids used were water, glycerol, and ethylene glycol with different surface tension values (72.8, 63.4, and 47.7 nN m −1 , respectively) [ 82 ], and they could describe the responses of materials related to aging evolution when these materials operated under unlikely conditions. The smallest differences between the values of surface tension could be noticed for the complete composition, where UHMWPE, Hap, and RM were included in the LDPE matrices.…”

Physical properties of lyocell-reinforced polypropylene composites from intermingled fibre with varying fibre volume fractions

“…The physical and chemical treatment of cellulose fibres, as well as the nucleation of transcrystalline layers of plastic on the fibre surface, can improve the adhesion between the two components. 4 –10 In particular, the chemical modification of PP by copolymerization with maleic anhydride has been studied to improve the adhesion properties of the cellulose. 11 –17 Preparation and properties of composites, consisting of PP plastic and cellulose 18 –23 or cellulose-based plant fibres like sisal 12 , bagasse 24 , jute 25 –30 and hemp, 31 have already been studied in the literature.…”