Bast fibers for plastics reinforcement and preparation method thereof

Abstract

The present invention refers to bast fibers for plastics reinforcement and preparation method thereof. The bast fibers are composed of the following components by weight ratio; 100 pts.wt. chopped bast fibers, 0.1˜100 pts.wt. bast fiber treating agent, 1˜10 pts.wt. Functional Polyolefin wax, 0.1˜10 pts.wt. coupling agent and 0.1˜0.5 pts.wt. antioxidant. The method includes the steps of: firstly, cut chopped bast fibers and soak them in sodium hydroxide solution, agitate the mixture, after rinse and drying of water, soak the fibers in the aqueous solution of bast fiber treating agent, then dry them and obtain surface-treated chopped bast fibers; secondly, add in order the chopped fibers, the coupling agent, the Functional Polyolefin wax and the antioxidant to a preheated kneader, agitate the mixture and thus obtain bast fibers for plastics reinforcement. Chopped bast fibers according to the invention present good color, rigidity and heat resistance, as well as excellent compatibility with plastics, and can be used in the preparation of high-performance short-bast-fiber\plastic composites, as reinforcement in the plastic matrix.

Description

FIELD OF THE INVENTION[0001]The invention refers to the natural fiber composite materials and wood-plastic composite materials, especially refers to bast fibers for plastics reinforcement and preparation method thereofBACKGROUND OF THE INVENTION[0002]In recent years, research in natural plant fiber composite materials and wood-plastic composite materials has been in the ascendant. This is on the one hand because of the wide range of sources of natural plant fibers and relatively lower prices, and on the other hand due to the trend of natural plant fiber reinforced plastics being used as a replacement of mineral fiber reinforced plastics.[0003]Most natural plant fibers are, in long fibrous form or after being formed into a fiber mat, compiled into hot press molding with thermosetting resin, while can not be added directly into thermoplastic plastics for injection molding as glass fibers; in addition, on the one hand, natural plant fibers show strong polar and hydrophilic qualities du...

AI Technical Summary

Benefits of technology

[0018]The principle of the invention is as follows: through washing away the impurities on fiber surface with dilute alkali, and then processing the fibers in aqueous solution of the treating agent, such as urea-formaldehyde resin prepolymer, trimethyl melamine resin or hexamethyl melamine resin, etc., where hydroxyl groups on the fiber surface react with hydroxymethyl groups of the treating agent, coating the fiber surface with a layer of urea-formaldehyde resin or melamine resin, thus the surface polarity of the bast fibers is reduced and the water absorption rate of the bast fibers also reduced, while the rigidity and heat resistance of the bast fibers increased; further, the coupling agent helps improve compatibility between bast fibers and plastics, and the Functional Polyolefin wax favors the amelioration of lubrication and dispersion inside the fibers.

[0019]Compared with the existing technology, Chopped bast fibers according to the invention present good color, rigidity and heat resistance, as well as excellent compatibility with plastics, and can be used in the preparation of high-performance short flax fiber\plastic composites, as reinforcement in the plastic matrix.

Problems solved by technology

Most natural plant fibers are, in long fibrous form or after being formed into a fiber mat, compiled into hot press molding with thermosetting resin, while can not be added directly into thermoplastic plastics for injection molding as glass fibers; in addition, on the one hand, natural plant fibers show strong polar and hydrophilic qualities due to the high density of hydroxyl groups on fiber surface, which induces plant fibers to be poorly compatible with non-polar or weakly polar plastics and further leads to rather poor performance of composite materials thus made; on the other hand, plant fiber reinforced plastics are difficult for processing, in particular for injection molding, in light of the large volume and high filler content of plant fibers, as well as strong frictions existing between fibers and plastics, fibers and equipment, and among fibers.

For one thing, most of the coupling agents are in liquid form with less dosage, difficult for even dispersion in plant fibers and thus weaking the coupling effect, so special processing equipment is required for industrial applications; for another, most grafts or copolymers of maleic anhydride with polyolefin are in granular form, easy for dispersion in plastics and plant fibers, but the low grafting ratio brings negative effects on the improvement of the interface bond strength.

Even so, composites filled with a large number of plant fibers and plastics further presents the difficulty in extrusion or injection molding.

Various processing aids, such as olefin wax, amide wax, stearic acid, zinc stearate, calcium stearate, etc., have been developed to solve the problems in processing composite materials of plant fibers and plastics, but adding too much processing aids will also lower the performance of the composite materials.