Biocomposite

Abstract

A composite comprising a particulate and cellulose binders, in particular a primary binder (e.g. potato starch) and a secondary binder (e.g. a first and a second cellulose material). This may be a hy

Description

Field of invention The present invention relates to bio-composites and methods for making biocomposites. More particularly, but not exclusively, the invention relates to biocomposites formed using a cellulose binder. Background Concrete and other strong, rigid composites are widely used in various industries, such as manufacturing and art. However, the traditional materials used in these processes pose significant environmental challenges. Notably, these materials are generally non-biodegradable, non-recyclable, and have a highly polluting manufacturing process. The non-recyclability of conventional composites is a major concern. Once a composite has served its purpose, it typically becomes waste. As a result of the fact that conventional materials are non-recyclable and non-biodegradable, used products often end up in landfills or have to broke down and disposed of in an expensive and energy-intensive manner. Further, the manufacturing process for conventional concrete creates large quantities of Carbon Dioxide and other greenhouse gases, thereby contributing to the greenhouse effect and leading to environmental damage. Given these significant drawbacks, there is a need for the development of alternative composite materials. However, thus far, composites created to be biodegradable have failed to provide the required mechanical properties, and / or cannot be manipulated easily enough to be shaped as required. The present invention was derived with the foregoing in mind. Summary of invention According to a first aspect of the invention, there is provided a composite. The composite may comprise: a particulate substance; a primary binder; and a secondary binder, wherein the secondary binder is, or comprises, a cellulose material. Using cellulose as a secondary binder may provide the benefit of strengthening the binding between the particulate substance and the primary binder. The use of a cellulose material may make the composite more environmentally friendly as cellulose is a renewable material. The use of cellulose may ensure that the composite is biodegradable. For example, the addition of water to the composite may dissolve the cellulose and enable the composite to break down into constituent parts. The particulate substance may be, or comprise, a granular material. The particulate substance may be, or comprise, sand. The sand may be silica sand. The constituent particles of the particulate substance may have an average diameter between 1cm and 1pm. The constituent particles of the particulate substance may have an average diameter between 1mm and 1pm. The constituent particles of the particulate substance may have an average diameter between 1mm and 0.1mm. The primary binder may be, or comprise, starch. The starch of the primary binder may be, or comprise, potato starch. The use of starch and cellulose, which are both renewable materials, may ensure the composite is environmentally friendly, non-toxic, and biodegradable. The starch and the cellulose may both act as binders to fix the particulate substance into a solid composite. The ratio of the primary binder to the particulate substance may be between 1:4 to 1:6 by weight. The ratio of the primary binder to the particulate substance may be substantially 1:5 by weight. The secondary binder may comprise a first cellulose material and a second cellulose material which is different to the first cellulose material. The first cellulose material may be a cellulose powder. The first cellulose material may be hydroxylated cellulose. The first cellulose material may be Hydroxypropylmethylcellulose (HPMC). The second cellulose material may be, or comprise, cellulose fibres. The second cellulose material may be, or comprise, cellulose fibres with an average length between substantially 100-300pm. The second cellulose material may be, or comprise, cellulose fibres with an average length of substantially 200pm. According to a second aspect of the invention, there is provided a method of forming a composite. The method may be used to form the composite of the first aspect of the invention. The method may comprise: providing a particulate substance; providing a primary binder; combining the particulate substance with the primary binder to form a dry mixture; applying a binder solution to the dry mixture to form a wet mixture, wherein the binder solution comprises a solvent and a cellulose material; and forming a composite by drying the wet mixture to remove the solvent. Applying a binder solution to the dry mixture may convert the resultant wet mixture into a gel or clay which is more easily workable into a desired shape or structure. The binder solution may comprise: the solvent; a first cellulose material; and a second cellulose material which is different to the first cellulose material. The solvent may be water. The first cellulose material may be, or comprise, a cellulose powder. The first cellulose material may be hydroxylated cellulose. The first cellulose material may be a hydroxylated cellulose powder. The first cellulose material may be Hydroxypropylmethylcellulose (HPMC). The first cellulose material may be a Hydroxypropylmethylcellulose (HPMC) powder. The second cellulose material may be, or comprise, cellulose fibres. The proportion of cellulose powder in the binder solution may be between substantially 0-5% by weight of the solvent. The proportion of cellulose fibre in the binder solution may be between substantially 0-2% by weight of the solvent. Forming the binder solution may comprise: dissolving the cellulose powder in the solvent; and mixing the cellulose fibres into the solution comprising the dissolved cellulose power. Dissolving the cellulose powder in the solvent may comprise dissolving the powder in the solvent with the solvent temperature less than, or equal to, 30°C. Dissolving the cellulose powder in the solvent may comprise dissolving the powder in the solvent with the solvent temperature less than, or equal to, 25°C. The ratio of the binder solution to the dry mixture may be between substantially 30-35:100 by volume. Having a ratio of the binder solution to the dry mixture in this range may ensure the wet mixture is sufficiently loose to be used for 3D printing. For greater proportions of binder solution, the wet mixture may become too viscous to be 3D-printable. For lesser proportions of binder solution, the wet mixture may become too dry to be 3D-printable. Applying the binder solution to the dry mixture may comprise kneading the dry mixture with the binder solution. Kneading the dry mixture with the dry solution may enable the binder solution to be dispersed uniformly throughout the mixture. The method may comprise 3D printing the wet mixture into a desired composite shape or structure. The ratio of the binder solution to the dry mixture may be between substantially SO-55:100 by volume. Having a ratio of the binder solution to the dry mixture in this range may ensure the wet mixture is sufficiently viscous to be suitable for brushing onto the surface of a mould and may enable the wet mixture to remain stuck onto vertical or near vertical surfaces. With a lesser proportion of binder solution, the wet mixture may become too dry for application to a surface of a mould, and it may become too prone to crumble whilst drying. With a greater proportion of binder solution the wet mixture may become too prone to movement down the surface of the mould. Applying the binder solution to the dry mixture may comprise mixing and folding the dry mixture with the binder solution. The method may comprise applying a wet mixture to the surface of a mould. Applying the wet mixture to the surface of a mould may comprise brushing the wet mixture on the surface of a mould. Drying the wet mixture to remove the solvent may comprise heating the wet mixture. Heating the wet mixture may comprise placing the wet mixture inside an oven. Heating the wet mixture may comprise heating the wet mixture with a heat gun. According to a third aspect of the invention, there is provided a binder. The binder may be for use in a composite. The binder may be the secondary binder of the composite of the first aspect, or the binder solution used in the method of the second aspect. The binder may comprise: a first cellulose material; and a second cellulose material which is different to the first cellulose material. Optional features of any of the above aspects may be combined with the features of any other aspect, in any combination. Features which are described in the context or separate aspects and embodiments of the invention may be used together and / or be interchangeable wherever possible. Similarly, where features are, for brevity, described in the context of a single embodiment, those features may also be provided separately or in any suitable sub-combination. Brief description of the drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a flowchart representing a method of forming a composite; Figure 2 shows a flowchart representing the final steps of a method of forming a composite according to an example; Figure 3 shows a perspective view of a composite being manufactured via a 3D printing process; Figure 4 shows a perspective view of a composite being manufactured via a 3D printing process; Figure 5 shows a flowchart representing the final steps of a method of forming a composite according to an example; Figure 6 shows a perspective view of a composite manufactured via a brushing process; and Figure 7 shows a flowchart representing the final steps of a method of forming a composite according to an example. Detailed description Figure 1 shows a flowchart representing a method 100 of forming a composite. The method 100 comprises providing 110 a particulate substance. In some examples, the particulate substance is, or comprises, a plurality of solid particles. The constituent particles of the particulate substance can be formed of one or more materials. In some examples, the particulate substance is, or comprises, a granular material. In some such examples, the granular material is sand. In some such examples, the granular material is silica sand. In some examples, the constituent particles of the particulate substance can have an average diameter between 1cm and 1pm. In some examples, the constituent particles of the particulate substance can have an average diameter between 1mm and 1pm. In some examples, the constituent particles of the particulate substance can have an average diameter between 1mm and 0.1mm. In some examples, the particulate substance is, or comprises, wood dust, wood powder, or wood shavings. In some examples, the particulate substance is, or comprises, egg shell pieces. In some examples, the particulate substance is, or comprises, coffee grounds. The method 100 comprises providing 120 a primary binder. In some examples, the primary binder is a material derived from plants or other biomaterial. In some examples the primary binder is, or comprises, starch. The starch can be derived from any suitable source, such as, but not limited to, corn, tapioca, or potato. In other examples, the primary binder is, or comprises, an alternative material, such as a gum (such as Guar Gum, or Xanthan Gum), Gelatin, or Pectin. The method 100 comprises combining 130 the particulate substance with the primary binder to form a dry mixture. Combining 130 the particulate substance with the primary binder to form a dry mixture can comprise stirring or agitating the dry mixture to evenly disperse the primary binder throughout the dry mixture. In some examples, the ratio of the primary binder to the particulate substance in the dry mixture is substantially between 1:4-1:6 by weight. In some examples, the ratio of the primary binder to the particulate substance in the dry mixture is substantially 1:5 by weight. The method 100 comprises applying 140 a binder solution to the dry mixture to form a wet mixture. The terms “dry mixture” and “wet mixture” used herein are intended to respectively refer to the mixture of the particulate substance with the primary binder before and after the addition of the binder solution. The binder solution comprises a solvent and a cellulose material. The term “cellulose material” used herein is intended to refer to materials formed of, or comprising, cellulose or materials derived from cellulose. In some examples, the solvent is water. In other examples, the solvent can be glycerine, acetone, Isopropyl alcohol, or any other known solvent. In some examples, the binder solution comprises: the solvent; a first cellulose material; and a second cellulose material which is different to the first cellulose material. In some examples, the first cellulose material is, or comprises, hydroxylated cellulose. In some examples, the first cellulose material is, or comprises, Hydroxypropylmethylcellulose (HPMC). In some examples, the first cellulose material is, or comprises, a cellulose powder. The cellulose powder can be, or comprise, hydroxylated cellulose. The cellulose powder can be, or comprise, Hydroxypropylmethylcellulose (HPMC). In some examples, the proportion of the first cellulose material in the binder solution is between substantially 0-5% by weight of the solvent. In some examples, the second cellulose material is, or comprises, cellulose fibres. In some examples, the second cellulose material is, or comprises, pure cellulose fibres. In some examples, the proportion of the second cellulose material in the binder solution is between substantially 0-2% by weight of the solvent. In some examples, the method 100 further comprises forming the binder solution. In some examples, the binder solution is formed by dissolving the first cellulose material (which can be a cellulose powder) in the solvent, and mixing the second cellulose material (which can be cellulose fibres) into the solution comprising the dissolved first cellulose material. In some examples, dissolving the cellulose powder in the solvent comprises blending, or stirring, the cellulose powder in the solvent. In some examples, dissolving the cellulose powder in the solvent comprises introducing the cellulose powder to the solvent whilst the solvent is at temperature less than, or equal to, 30°C. In some examples, dissolving the cellulose powder in the solvent comprises introducing the cellulose powder to the solvent whilst the solvent is at temperature less than, or equal to, 25°C. The method 100 comprises forming 150 a composite by drying the wet mixture to remove the solvent from the wet mixture. In some examples, drying the wet mixture comprises heating the wet mixture. For example, the wet mixture can be heated to between 100-140°C for a time period of between 1-2 hours. In some examples, the wet mixture can be heated using an oven. In some examples, the wet mixture can be heated using a heat gun. The method 100 can be used to create composites with a variety of different shapes and for a variety of different applications. Accordingly, different methods can be used to shape the composite. Depending on the method used to shape the composite, different amounts of binder solution can be added to the dry mixture, and different binder solution compositions can be used. Depending on the amount of binder solution used, different methods can be used to add the binder solution to the dry mixture. Some specific examples are discussed below. Figure 2 shows a flowchart representing the final stages of a method 200 of forming a composite, according to a first example which uses 3D printing. In this example, the particulate substance is silica sand, and the primary binder is potato starch. In this example, the binder solution comprises HPMC powder as the first cellulose material, cellulose fibres as the second cellulose material, and water as the solvent. The average length of the cellulose fibres is 200pm. The composition of the binder solution is such that, for every 100 grams of water, there are 5 grams of HPMC powder and 2 grams of cellulose fibres. In this example, in the step of applying the binder solution to the dry mixture, the volume of binder solution added to the dry mixture is between 30-35% of the dry (i.e., initial) mixture volume. That is to say, for every 1 litre of dry mixture, between 300-350ml of binder solution is added. In a more specific example, for every 1 litre of dry mixture volume, 347.2ml of binder solution is added. In this example, to apply 240 the binder solution to the dry mixture, the dry mixture is kneaded with the binder solution. After applying the binder solution to the dry mixture, the method 200 comprises 3D printing 245 the wet mixture into a desired composite shape / form. In some examples, the wet mixture is 3D printed using a 3mm nozzle compressed air cylinder ceramic clay 3D printer. After the wet mixture 245 is printed into a desired shape / form, the wet mixture is dried to remove the solvent to form the composite. Composites 1000, 2000 shown in Figures 3 and 4 are examples of composites formed using the method 200 of Figure 2. Figure 5 shows a flowchart representing the final stages of a method 300 of forming a composite, according to a second example which uses a brushing technique. In this example, the particulate substance is silica sand, and the primary binder is potato starch. In this example, the binder solution comprises HPMC powder as the first cellulose material, cellulose fibres as the second cellulose material, and water as the solvent. The average length of the cellulose fibres is 200pm. The composition of the binder solution is such that, for every 100 grams of water, there is 5 grams of HPMC powder and 2 grams of cellulose fibres. In this example, rather than 3D printing the wet mixture into a desired shape, the wet mixture is applied to a surface of a mould. For example, the wet mixture can be brushed onto the surface of a mould. To make the wet mixture suitable for brushing applications, it is required to be more viscous, as it needs to be able to support its own weight when applied to vertical, or near vertical, surfaces. To make the wet mixture more viscous, greater amounts of binder solution are added to the dry mixture. In this example, the volume of binder solution added to the dry mixture is between 50-55% of the dry mixture volume. That is to say, for every 1 litre of dry mixture, between 500-550ml of binder solution is added. In this example, to apply 340 the binder solution to the dry mixture, the dry mixture is folded and stirred with the binder solution. After applying 340 the binder solution to the dry mixture, the method 300 comprises brushing 345 the wet mixture onto the surface of a mould with a desired shape / form. After the wet mixture is brushed 345 onto the mould, the wet mixture is dried to remove the solvent to form the composite. Composite 3000 shown in Figure 6 is an example of a composite formed using the method 300 of Figure 5. Figure 7 shows a flowchart representing the final stages of a method 400 of forming a composite, according to a third example in which the wet mixture is poured into a mould. In this example, the particulate substance is silica sand, and the primary binder is potato starch. In this example, the binder solution comprises HPMC powder as the first cellulose material, cellulose fibres as the second cellulose material, and water as the solvent. The average length of the cellulose fibres is 200pm. In this example, rather than 3D printing, or brushing, the wet mixture into a desired shape, the wet mixture is poured into a mould. To make the wet mixture suitable for poring applications, it is required to be less viscous, as it needs to be able to run freely. To make the wet mixture less viscous, the proportion of the first and second cellulose materials can be reduced in the binder solution, relative to the examples discussed above. For example, the composition of the binder solution can be such that, for every 100 grams of water, there is less than 5 grams of HPMC powder. For example, there can be 1 gram, or 0.5 grams, of HPMC powder for every 100 grams of water. The composition of the binder solution can be such that, for every 100 grams of water, there is less than 2 grams of cellulose fibres. In a particular example, for every 100 grams of water, there is 0.2 grams of HPMC power and 0.08 grams of cellulose fibres. In this example, to apply 440 the binder solution to the dry mixture, the dry mixture can be folded and stirred with the binder solution. In this example, the volume of binder solution added to the dry mixture is between 20-25% of the dry mixture volume. After applying 440 the binder solution to the dry mixture, the method 400 comprises pouring 445 the wet mixture into a mould with a desired shape / form. After the wet mixture is poured 445 onto the mould, the wet mixture is dried to remove 450 the solvent to form the composite. For any of the composites described herein, post processing steps can be performed after the wet mixture is dried to form the composite. For example, the composite can be sanded to create a smooth surface finish. As another example, the composite can be water-proofed, for example, with a wax spray coating. From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art of composite and bio composites and which may be used instead of, or in addition to, features already described herein. Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. The applicant hereby gives notice that new claims may be formulated to such features and / or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

1. A composite comprising:a particulate substance;a primary binder; anda secondary binder, wherein the secondary binder is, or comprises:a first cellulose material; anda second cellulose material which is different to the first cellulose material.

2. The composite of claim 1, wherein the particulate substance is, or comprises, sand.

3. The composite of claim 1 or claim 2, wherein the primary binder is, or comprises, starch.

4. The composite of claim 3, wherein the starch of the primary binder is, or comprises, potato starch.

5. The composite of any preceding claim, wherein the ratio of the primary binder to the particulate substance is between 1:4 to 1:6 by weight.

6. The composite of any preceding claim, wherein the secondary binder consists of:the first cellulose material; andthe second cellulose material which is different to the first cellulose material.

7. The composite of claim 6, wherein the first cellulose material is a cellulose powder.

8. The composite of claim 6 or claim 7, wherein the first cellulose material is hydroxylated cellulose.

9. The composite of claim 8, wherein the first cellulose material is Hydroxypropylmethylcellulose (HPMC).

10. The composite of any of claims 6 to 9, wherein the second cellulose material is, or comprises, cellulose fibres.

11. A method of forming a composite, comprising:providing a particulate substance;providing a primary binder;combining the particulate substance with the primary binder to form a dry mixture;applying a binder solution to the dry mixture to form a wet mixture, wherein the binder solution comprises a solvent, a first cellulose material, and a second cellulose material which is different to the first cellulose material; andforming a composite by drying the wet mixture to remove the solvent.

12. The method of claim 11, wherein the binder solution consists of:the solvent;the first cellulose material; andthe second cellulose material which is different to the first cellulose material.

13. The method of claim 10, wherein the first cellulose material is, or comprises, a cellulose powder.

14. The method of claim 12 or claim 13, wherein the first cellulose material is Hydroxypropylmethylcellulose (HPMC).

15. The method of claim 13 or claim 14, wherein the proportion of the first cellulose material in the binder solution is between substantially 0-5% by weight of the solvent.

16. The method of any of claims 12-15, wherein the second cellulose material is, or comprises, cellulose fibres.

17. The method of any of claims 12-16, wherein the proportion of the second cellulose material in the binder solution is between substantially 0-2% by weight of the solvent.

18. The method of any of claims 11-17, wherein the ratio of the particulate substance to the primary binder in the mixture is substantially between 1:4-1:6 by weight.

19. The method of any of claims 12-18, further comprising, forming the binder solution by:dissolving the first cellulose material in the solvent; andmixing the second cellulose material into the solution comprising the dissolved first cellulose material.

20. The method of any of claims 11-19, wherein the ratio of the binder solution to the dry mixture is between substantially 30-35:100.

21. The method of claim 20, wherein applying the binder solution to the dry mixture comprises:kneading the dry mixture with the binder solution.

22. The method of claim 21, further comprising 3D printing the wet mixture.

23. The method of any of claims 11-19, wherein the ratio of the binder solution to the dry mixture is between substantially 50-55:100.

24. The method of claim 23, wherein applying the binder solution to the dry mixture comprises:mixing and folding the dry mixture with the binder solution.

25. A binder for use in a composite, the binder consisting of:a first cellulose material; anda second cellulose material which is different to the first cellulose material.A

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