Cellulosic inclusion thermoplastic composition and molding thereof

Abstract

A cellulosic inclusion-thermoplastic composition that includes cellulosic inclusions and a thermoplastic polyolefin that forms a matrix in which the cellulosic inclusions are dispersed. A maleated polymer and a polar thermoplastic polymer resin of a polyamide or polyester are provided to improve adhesion between the cellulosic inclusions and the thermoplastic polyolefin. The polar thermoplastic polymer resin is characterized by a melting temperature greater than that of the thermoplastic polyolefin. The composition as provided has increased break tensile strength relative to a composition devoid of the polar thermoplastic polymer resin but otherwise is unchanged. The break tensile is measured at 23° Celsius and at an elongation rate of 50 millimeters per minute.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority of U.S. Provisional Patent Application Ser. No. 61 / 021,734 filed Jan. 15, 2008, which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention in general relates to a composition containing cellulosic inclusions dispersed in a thermoplastic polymeric matrix and in particular to such a composition with improved distribution of the cellulosic inclusions and physical properties.BACKGROUND OF THE INVENTION[0003]It is typical in the plastics industry that reinforcements and fillers are used to improve the properties of said materials. Commonly, this is done to achieve improvement in physical properties such as tensile strength, flexural modulus and impact strength. Common fillers are talc, calcium carbonate and other minerals. By far the most common fibrous reinforcement is glass. Glass fibers impart high strength, dimensional stability and heat stability. There are commercial requi...

AI Technical Summary

Benefits of technology

The composition achieves superior mechanical properties, including increased break tensile strength, improved flexural strength, and reduced environmental impact, enabling the production of molded articles with enhanced performance and reduced processing issues.

Problems solved by technology

There are commercial requirements that glass fiber and other mineral fillers cannot fully meet.

For example, glass fibers increase the density and cost of the material and abrade processing equipment.

In addition, glass fibers are manmade, non-renewable materials with a considerable environmental impact.

When the wood fibers are processed with thermoplastic resins at temperatures that exceed 200° C., the fibers exhibit severe discoloration and thermal degradation.

There is also significant off-gassing and objectionable odors, principally due to impurities and the lignin that modify manufacturing process and create a worker safety concern.

It has also been shown that processing temperatures above 200° C. reduce the physical property improvements delivered by the fibers (Klason, et al., Inter.

Furthermore, when the moisture present during the processing of the cellulosic materials is not controlled and / or eliminated, performance of the resultant composite is compromised.

Management of moisture in the materials and the molded parts has proved costly and difficult, most commonly being achieved through fiber pre-processing or encapsulation of the fiber in the thermoplastic.

Wood fibers are hydrophilic materials that are poorly wet by molten hydrophobic thermoplastic polymers resulting in poor flow characteristics, difficult processability, and premature fiber pull-out, all of which leads to molded products with poor appearance and inferior mechanical properties.

The engineering of desirable processing and physical properties into a WPC is further complicated by the addition of other substances such as reinforcing glass fiber filler, non-cellulosic particulate fillers, colorants and mold release compounds.

None of the wood polymer composite materials that have been developed to date afford a completely satisfactory set of performance characteristics and as such are deficient for end-use applications in one or more of, e.g., poor physical properties, water resistance, undesirable odor, poor processability and / or excessive cost.

These shortcomings stem from drawbacks in a forming process having poor melt flow characteristics due to inadequate adhesion between the dispersed wood fibers and thermoplastic polymer matrix at high wood fiber loading levels.

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