Biocomposite material

Abstract

A biocomposite material (1) and methods of production thereof are described. The biocomposite material (1) exhibits a physical stiffness, strength and toughness comparable to known glass fibre composites while its composition makes it inherently impermeable to water. A general formulation for the biocomposite material (1) is given by the expression: Cel(1-x-y)HPIx HPOy where “Cel” represents cellulose fragments (2), “HPI” represents hydrophilic binders (4), “HPO” represents hydrophobic binders (5) and (x) and (y) quantify the percentage by weight of the hydrophilic (4) and hydrophobic binders (5) present within a material, respectively. The described properties of the biocomposite material (1) are achieved when (x) is within the range of from 0.05 to 0.55 and (y) is within the range of from 0.05 to 0.65.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application is a division of U.S. application Ser. No. 11 / 791,221, filed Nov. 10, 2005, which is a National Stage Entry of International Application No. PCT / GB2005 / 004322, filed Nov. 10, 2005, which claims the benefit of GB Application No. 0425691.3, filed Nov. 23, 2004. The entire contents of the above-identified applications are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to the field of biocomposite materials and in particular to biocomposite materials produced through the extraction of cellulose from plants.[0003]The use of plant based long fibres such as hemp, flax, kanaf, cotton, jute, sisal and coconut fibre mats as reinforcement for polymer matrices such as polypropylene and epoxy resins are well known to those skilled in the art. These composites utilise fibres which are typically several centimetres long and hundreds of micrometers wide (usually in the form of bundles of sever...

AI Technical Summary

Benefits of technology

The patent text describes a method for creating a biocomposite material with desired properties such as stiffness, strength, and toughness. The method involves arranging hydrophobic binders to encapsulate cellulose fragments and render the material impermeable to water. Standing the mixture of pulp and bleach solution for at least thirty minutes helps reduce particle size. The technical effect of this method is the creation of a strong, stiff, and waterproof biocomposite material.

Problems solved by technology

Primarily these plant based long fibres have found applications in the automotive industry, but only for non-structural applications such as door liners and parcel shelves, due in part to the poor surface finish achieved with these materials, but mainly because of their reduced toughness when compared to glass fibre reinforced polymers (GFRP).

These materials are also known to exhibit inherent problems with water absorption and odour release.

However, these materials suffer from similar problems to the long plant fibre composites, being either brittle and water proof (e.g. Formica) or alternatively tough but water absorbent (e.g. MDF).

In general these materials are stiff and strong but only achieve toughness equal to or greater than glass fibre if the resin content is kept to less than 3%, so resulting in a highly hygroscopic material which losses strength as it absorbs water.

Also the method of manufacturing the materials, which involves impregnating sheets of dry fibres with dilute resin and then stacking many thin (<0.5 mm) sheets of impregnated material on top of one another and hot pressing at high pressure, is a very time consuming process, taking over 100 hours.

This severely increases manufacturing time compared to GFRP and so greatly limits the potential range of applications for these materials.

However, these materials exhibit a lower stiffness than GFRP which limits their applications to surface finishes.

Furthermore, such materials can only be classified as a partial biocomposite material due to the significant proportion of GFRP present.

Although these materials are water resistant they exhibit only limited modulus and strength.

Composite materials made from these animal and bacterial cellulose microfibrils have been shown to exhibit high stiffness and good strength but have inherently low failure strains which results in them being brittle in nature.

However, the tensile modulus of these composite materials is less than 5 GPa, which is no better than the levels achieved within non-reinforced plastics, and is too low to allow them to be employed within many structural applications.

However, this in itself is problematic because even when a few percent, by weight, of free cellulose microfibrils are added to a liquid, the viscosity of the liquid increases dramatically.

This is a complex and time consuming process involving many individual manufacturing steps and so the composite materials produced by this route consume large amounts of energy during manufacturing and therefore are not economical for commercial scale production.

To date the composite materials produced by this method exhibit very poor mechanical properties with low stiffness and poor strength.

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