SAME

Field

Embodiments generally relate to bark fibre products, bark composite materials, and to processes for producing such materials and products.

Background

Composite materials are combinations of two or more different constituent materials, in which the constituents remain distinct within the structure of the final material, and in which the composite often has improved properties over those of materials formed of the individual components. Composite materials have a wide variety of applications in fields such as the construction industry (e.g. facade panels, moulded sheet panels, structural sections), transportation (e.g. car chassis, aircraft components), domestic goods (e.g. protective cases for electronic devices, containers and packaging) and sporting equipment (e.g. bicycle frames, helmets). Examples of composite materials include fibreglass and fibre -reinforced concrete.

Human activity has had a significant impact on the environment and the need to fulfil human needs from renewable resources has never been more important. Most bio-composites used to date, at least in the construction industry, contain either a synthetic matrix or fibre. It would be desirable to identify composite materials which have properties such that they are suitable for use in a wide variety of applications and which contain matrix and fibre materials which are renewable and sustainable, it would further be advantageous to identify a renewable feedstock for fibres having properties such that they are suitable for use in a range of composite materials.

Carbon fibre composite materials are known for their high tensile strength and low weight, and are frequently used in aerospace and construction applications. However, carbon fibres are expensive to produce, requiring the use of energy intensive processes and non-renewable feedstocks for their production. It would also be desirable to identify fibres which are suitable as replacements for carbon fibre in composite materials, but which can be obtained from renewable sources, which do not require such energy intensive processes for their production, and which can be produced comparatively inexpensively.

Summary

In a first aspect there is provided a bark fibre composite material comprising: a) bark fibres derived from a feedstock rich in tree bark; and

b) a matrix comprising a bio-based polymer.

Preferably the fibres are derived from a feedstock rich in Eucalyptus tree bark, in a second aspect there is provided a bark fibre composite material comprising: a) bark fibres derived from a feedstock rich in Eucalyptus tree bark; and

b) a matrix comprising a polymer.

In either the first or second aspect, preferably the fibres are derived from a feedstock rich in Eucalyptus globulus and/or Eucalyptus regnans tree bark.

In either the first or second aspect, preferably the fibres are derived from a feedstock rich in Eucalyptus globulus tree bark.

in either the first or second aspect, preferably the fibres are derived from a feedstock rich in Eucalyptus regnans tree bark.

In either the first or second aspect, preferably the matrix comprises a bio-based polymer selected from poly(lactic acid), poiy(3-hydroxybutyrate), poly(3- hydroxybutyrate-co-3-hydroxyvalerate), poly(ethylene succinate) and a furan resin.

In either the first or second aspect, preferably the bark fibres are fibre ribbons which have been derived by a process comprising:

providing a feedstock rich in tree bark;

subjecting the feedstock to mechanical cleaning; and

cutting cleaned tree bark into fibre ribbons.

In either the first or second aspect, preferably the bark fibre composite material is a structural member.

In a third aspect there is provided a process for producing a bark fibre composite comprising a) bark fibres derived from a feedstock rich in tree bark, and b) a matrix comprising a bio-based polymer; the process comprising:

i) pro viding a feedstock rich in tree bark; ii) subjecting the feedstock rich in tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and either

iii) contacting the bark fibres with a hardenable matrix comprising a bio-based monomer, and polymerising the bio-based monomer thereby producing the bark fibre composite material; or

iv) contacting the bark fibres with a hardenable matrix comprising a bio-based polymer at elevated temperature, and reducing the temperature of the mixture so as to produce the bark fibre composite material.

in a fourth aspect there is provided a process for producing a bark fibre composite material comprising: a) bark fibres derived from a feedstock rich in Eucalyptus tree bark, and b) a matrix comprising a polymer; the process comprising: i) providing a feedstock rich in Eucalyptus tree bark;

ii) subjecting the feedstock rich in Eucalyptus tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and either

iii) contacting the bark fibres with a hardenable matrix comprising a monomer, and polymerising the monomer thereby producing the bark fibre composite material; or iv ) contacting the bark fibres with a hardenable matrix comprising a polymer at elevated temperature, and reducing the temperature of the mixture so as to produce the bark fibre composite material,

In a fifth aspect there is provided a process for producing a bark fibre composite material comprising a) bark fibres derived from a feedstock rich in tree bark, and b) a matrix comprising a bio-based polymer; the process comprising:

i) providing a feedstock rich in tree bark;

ii) subjecting the feedstock rich in tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and

iii) contacting the bark fibres with a hardenable matrix comprising a bio-based polymer and producing the bark fibre composite material by injection moulding or extrusion.

In a sixth aspect there is provided a process for producing a bark fibre composite material comprising: a) bark fibres derived from a feedstock rich in Eucalyptus tree bark, and b) a matrix comprising a polymer; the process comprising:

i) providing a feedstock rich in Eucalyptus tree bark; ii) subjecting the feedstock rich in Eucalyptus tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and

iii) contacting the bark fibres with a hardenable matrix comprising a polymer and producing the bark fibre composite material by injection moulding or extrusion.

In a seventh aspect there is provided a bark composite material comprising: a) a bark material; and

b) a matrix comprising a bio-based polymer.

In an eighth aspect there is provided a bark composite material comprising: a) a bark material derived from a feedstock rich in Eucalyptus tree bark; and b) a matrix comprising a polymer.

In a ninth aspect there is provided a bark fibre product which is a yarn, twine, rope or mat.

In a tenth aspect there is provided a process for producing a bark fibre product which is a yarn, twine, rope or mat, the process comprising:

i) providing a feedstock rich in tree bark;

ii) subjecting the feedstock rich in tree bark to chemical and/or mechanical processing, thereby producing bark fibres;

iii) spinning the bark fibres to produce a yam or twine; and optionally

iv) converting the yarn or twin into a rope or mat.

Brief Description of the Drawings

Figure 1 shows representations of products producible from the bark fibre composite material according to some embodiments.

Figure 2 shows a photograph of bark fibre ribbons used to produce the bark fibre composite materials according to some embodiments.

Figure 3 shows a photograph of a bark fibre composite material according to some embodiments.

Figure 4 shows a graph showing the variation of the fibre length factor as a function of the length ratio (L,/L, _c ).

Figure 5 shows a graph showing the calculated tensile strength of a bark fibre composite material according to some embodiments as a function of the fibre volume fraction. The different curves represent various values of the parameter L/L _c as follows

Figure 6 shows a graph showing the calculated tensile strength of a bark fibre composite material according to some embodiments as a function of fibre length ratio for three different fibre volume fractions Vf = 0.6 (a), 0.4 (b) and 0.2 (c). In each group of curves, the curves descend in the order: poly(lactic) acid, poly(butylene succinate), poiy(3 -hydroxybutyrate) , poly(hydi'oxybu tyr ate-co-hydroxy valerate), modified acryiated epoxidised soy oil.

Figure 7 shows a picture of a structure produced using a bark fibre composite material according to some embodiments.

Figure 8 shows an embodiment of a process for producing a bark fibre composite material according to the present disclosure.

Detailed Description

Embodiments generally relate to bark fibre products, bark composite materials, and to processes for producing such materials and products.

The bark fibre composite material comprises bark fibres derived from a feedstock rich in tree bark. Australia has a large forestry industry comprising of native and plantation forest assets. The Australian forestry and logging industry generated $3,567 million in sales and service income between 2009-10 and together with agriculture and fisheries represent 2% of Australia's GDP (Australian Bureau of

Statistics 2012, Year Book Australia 2012, viewed 19/03/15

htrp://www.abs.gov.au/ausstats/abs@.nsf/Lxx)kup /by%20

Subject/1301.0~2012~Main%20Featui-es--Forestry%20aiid%20fish ing~28) For years, wood processing industries have grappled with ways to manage the residual bark and mill waste which typically requires continuous removal from processing sites.

Currently the most commercially viable uses of forestry and timber waste are in energy generation, e.g. through direct combustion or co-firing with coal.

The inventor has identified that bark fibres obtained from certain tree bark feedstocks, in particular feedstocks rich in bark from a peeling bark tree, are particularly suitable for use in the bark fibre composite materials. A peeling bark tree is a tree having hark which naturally peels off in strips. Examples of such trees are Eucalyptus trees. Examples of suitable Eucalyptus species include Eucalyptus delegatensis, Eucalyptus bicostata. Eucalyptus pseudoglobulus, Eucalyptus globulus, Eucalyptus baxteri. Eucalyptus rubida, Eucalyptus fasti gata, Eucalyptus cypellocarpa, Eucalyptus dairymple ana, Eucalyptus denticulate. Eucalyptus regnans, Eucalyptus obliqua, Eucalyptus dives, Eucalyptus radiata, Eucalyptus elata, Eucalyptus macrorhyncha, Eucalyptus nitens, Eucalyptus botryoidies, Eucalyptus sieberi, Eucalyptus vitninalis, Eucalyptus globoidea, Eucalyptus consideniana, Eucalyptus tnuelleriana, Eucalyptus leucoxylon, Eucalyptus tnaidenii and Eucalyptus saligna. in some embodiments, the bark fibres are derived from a feedstock rich in tree bark from a Eucalyptus species selected from the group consisting of Eucalyptus delegatensis, Eucalyptus bicostata, Eucalyptus pseudoglobiilus, Eucalyptus globulus, Eucalyptus baxteri, Eucalyptus rubida, Eucalyptus jastigata, Eucalyptus cypellocarpa, Eucalyptus dalrympleana, Eucalyptus denticulate, Eucalyptus regnans, Eucalyptus obliqua, Eucalyptus dives, Eucalyptus radiata, Eucalyptus elata, Eucalyptus macrorhyncha, Eucalyptus nitens, Eucalyptus botryoidies, Eucalyptus sieberi, Eucalyptus viminalis, Eucalyptus globoidea, Eucalyptus consideniana and Eucalyptus tnuelleriana. Particularly preferred feedstocks are those rich in Eucalyptus globulus (known as the Tasmanian Bluegum, Southern Bluegum and Bluegum) and/or Eucalyptus regnans (known as the Victorian Mountain Ash, Mountain Ash, Swamp Gum and Stringy Gum).

In 2009, Australia was reported to have two million hectares of plantation forests, 900,000 ha of which were hardwood. Eucalyptus Globulus (Tasmanian Bluegum) fails under this category. In Australia's green triangle (SA, VIC) and Albany (WA), Eucalyptus Globulus plantations comprise some 109882 hectares (Australian Bluegum Plantations 2014, "Plantation Management Plan for Australian Bluegum

Plantations Albany and the Green Triangle Region' , viewed 20/03/15

<http://www.austgum.com.au/australian-plantations- woodchips/documents/Plantation%20Management%20Plan%202014.pd f>). Typically these plantations are harvested using clear felling. When felled, the trees are defoliated and de-barked in preparation for milling or chipping. It is during this process that large volumes of waste timber - including bark - are separated from the main timber feed.

As discussed above, the inventor has found that tree baik obtained from such sources provides bark fibres particularly suitable for use in the bark fibre composite materials. For example, as a result of bark peeling, the feedstock for use in producing the bark fibre composites may readily be gathered from plantations without destruction of trees. In addition, the collection of bark feedstocks from the ground would remove a significant component of feedstock for bushfires. Alternatively, the feedstock may be waste bark from harvesting of such trees for use in the lumber or paper industries.

The bark obtained from trees such as Eucalyptus globulus and Eucalyptus regnans is also particularly suitable for use in producing the bark fibre composite materials, since it is recoverable in large strips or pieces. The use of such bark fibre sources may enable preparation of long fibres, particularly relative to other natural fibre products. Shorter fibres require more interweaving and concatenation which acts to reduce their strength. Thus the long fibre forms translate to a higher relative tensile strength of bark fibre, resulting in bark fibre composite materials with excellent properties, particularly with regard to tensile strength. Given those properties, it is envisaged that the bark fibre composite materials may replace for carbon fibre composite materials in a range of applications. In contrast to carbon fibres, which are obtained from petrochemical feedstocks, the bark fibres are obtained from renewable sources. In addition, the bark fibres may be produced relatively inexpensively using processes having low environmental impact.

in some embodiments, the bark fibres are derived from a feedstock rich in peeling tree bark. In some embodiments, the bark fibres are derived from a feedstock rich in Eucalyptus tree bark. In some embodiments, the bark fibres are derived from a feedstock rich in Eucalyptus globulus and/or Eucalyptus regnans tree bark. In some embodiments, the bark fibres are derived from a feedstock rich in Eucalyptus globulus tree bark. In some embodiments, the baik fibres are derived from a feedstock rich in Eucalyptus regnans tree bark. Some embodiments relate to a bark fibre product formed using such a feedstock. The bark fibre product may be or include a bark fibre yarn or rope or a mat formed using such a yarn or rope, for example. The bark fibre yarn or rope may be formed into a. spool or coil of such yam or rope, for example, before being applied to a particular use, such as weaving it into a mat. in some embodiments the bark fibre product may be an intermediate product that can be used to produce a final bark composite material. For example, the bark fibre product may be a woven mat, which can subsequently be contacted with a matrix to produce a composite material.

Whilst in some embodiments the feedstock rich in tree bark may consist of or consist essentially of tee bark, in other embodiments the feedstock may also contain other materials, for example the feedstock may contain some foliage or tops. In some embodiments, the feedstock comprises at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% by weight tree bark. In the case where the feedstock is one which is rich in bark from peeling bark trees, Eucalyptus trees, Eucalyptus globulus trees or Eucalyptus regnans trees, in some embodiments the feedstock comprises at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% by weight tee bark from the specified source.

It is envisaged that the bark fibre composite materials may be utilised in a range of different applications in areas such as construction, domestic goods, military materials, sporting equipment, transport and the medical sector. Examples of applications of the bark fibre composite materials are provided in Table 1 below:

Table 1

Examples of such products are shown in Figure 1. In some embodiments the bark fibre composite material is a structural member. In some embodiments the bark fibre composite material is a rigid bark fibre composite material. In some embodiments the bark fibre composite material is a resilient bark fibre composite material. In some embodiments the bark fibre composite material consists of or consists essentially of materials derived from renewable sources, i.e. from non-petrochemical sources.

Prior to producing the bark fibre composite material, the bark fibres must be obtained from the feedstock rich in tree bark. Typically, the feedstock rich in tree bark (e.g. Eucalyptus tree bark, and in particular Eucalyptus globulus and/or Eucalyptus regnans tree bark) is subjected to one or more chemical and/or mechanical processing- steps, thereby producing bark fibres. A range of fibre types may be produced from the tree bark feedstock, enabling production of a variety of bark fibre composite materials.

In some embodiments, the bark fibres are in the form of long fibre bundles or bark fibre ribbons. Such bark fibre ribbons may for example be obtained by mechanically cleaning the feedstock rich in tree bark to remove non-bark material (e.g. by scraping), and by cutting the cleaned bark into bark fibre ribbons. In some embodiments bark fibre ribbons are obtained by a process comprising: subjecting a feedstock rich in tree bark to chemical and/or biochemical processing; and cutting the resulting product into bark fibre ribbons. For example, such a process may comprise subjecting a feedstock rich in tree bark to hydration conditions (e.g. contacting the feedstock with an aqueous medium such as water, for example in a retting-type process, or by use of high pH conditions), and then cutting or shredding the resulting material to form bark fibre ribbons. In some embodiments the bark fibres are bark fibre ribbons having a mean length to width ratio in the range of from 5 to 1 to 100 to 1, or from 5 to 1 to 50 to 1 , or from 5 to 1 to 20 to 1. In some embodiments the bark fibres are bark fibre ribbons having a mean length in the range of from 5 cm to 15 cm, or from 7.5 cm to 12.5 cm, or a mean length of about 10 cm. In some embodiments the bark fibres are bark fibre ribbons having a mean length in the range of from 5 cm to 15 cm, or from 7.5 cm to 12.5 cm, or a mean length of about 10 cm; and a mean length to width ratio in the range of from 5 to 1 to 20 to 1.

In some embodiments, bark fibre ribbons may optionally be further processed to form a mat of bark fibre ribbons.

In some embodiments, the bark fibres are in the form of long wool-like fibres/ bark fibre filaments. Such bark fibre filaments may be obtained by mechanical, chemical and/or biochemical processing steps. For example, in the case of mechanical processing, scutching-type (beating or striking the natural material to remove non- celiulosic components) and/or hackling-type (passing the natural material through one or more combs, thereby aligning the celiulosic fibre filament) mechanical processing may be carried out. In the case of chemical/biochemical processing, the feedstock rich in tree bark may for example be processed by subjecting it to hydration conditions (e.g. contacting the feedstock with an aqueous medium such as water). For example, the feedstock rich in tree bark may be subjected to a retting-type process in which the feedstock is contacted with water for an extended period of time (e.g. at least several days) and the action of water, and bacteria present in the water, results in at least partial separation of fibres from surrounding lignin and pectin. Chemical and/or biochemical agents may also be used to aid separation of bark fibres in an aqueous medium. For example detergents, high pH conditions (e.g. using an alkali such as sodium hydroxide), elevated temperature (e.g. a temperature in the range of from 50 to 95°C, or from 75 to 90°C) and/or chelating agents may be utilised. Enzymes may also be used to aid separation of bark fibres. In some embodiments, the feedstock rich in bark fibre is contacted with aqueous alkali (e.g. aqueous sodium hydroxide) at elevated temperature (e.g. at a temperature in the range of from 50 to 95°C, or from 75 to 90°C). The bark fibre feedstock may for example be subjected to steam explosion conditions. A further example of chemical processing involves contacting a feedstock rich in bark with an ionic liquid at elevated temperature, i.e. an ionic liquid capable of selectively dissolving lignin over cellulose, such as imidazolium acesulfamate ionic liquids (e.g. 1- butyi-3-methylimidazolium acesulfamate, 1 -ethyl-3-methylimidazolium acesulfamate). During chemical or biochemical processing, the mixture may be agitated, or the liquid component circulated within or re-circulated through the vessel or tank. Since fibre filaments are less likely to be broken during chemical/biochemical processing than during mechanical processing, a particular advantage of using chemical and/or biochemical processing of feedstocks is that it facilitates maintenance of fibre strand length and production of bark fibres filaments of long length. Thus in some embodiments, the feedstock rich in tree bark is subjected to chemical and/or biochemical processing. Such processing is expected to facilitate the production of bark fibres in long wool-like fibres or bark fibre filaments. In some embodiments, the bark fibre filaments have a mean length to diameter ratio in the range of greater than 25 to 1 , or greater than 50 to 1.

In some embodiments, the bark fibre filaments have a mean length of at least lcm, at least 2cm, at least 3cm, at least 4cm, at least 5cm, at least 7.5cm, at least 10cm, or at least 15cm. In some embodiments, the bark fibre filaments have a mean length of at least lcm, at least 2cm, at least 3cm, at least 4cm, at least 5cm, at least 7.5cm, at least 10cm, or at least 15cm; and a mean length to diameter ratio in the ratio of greater than 25 to 1 , or greater than 50 to 1.

In some embodiments, a combination of chemical, biochemical and/or mechanical processing steps may be used. For example, the feedstock rich in tree bark, may be subjected to hydration conditions, and the resulting material then cut or shredded to form bark fibre filaments. Prior to the hydration step, the feedstock rich in tree bark may also be subjected to mechanical cleaning to remo ve non-bark material.

Natural fibres tend to be hydrophilic/ contain polar moieties, in contrast to the matrices typically used in producing composite materials. In addition, unlike synthetic fibres such as glass and carbon, natural fibres can absorb significant quantities of moisture, which may affect interfacial bonding between the bark fibres and matrix. In some embodiments, the bark fibres (e.g. bark fibre filaments) are dried at elevated temperature (e.g. at a temperature in the range of from 60 to 100°C, from 70 to 90°C, or about 80°C). A stream of air may be passed over the material during drying. For example a forced air oven may be used to dry the bark fibres.

Alternatively or in addition to the drying step discussed above, to improve interfacial bonding between the bark fibres and matrix, and to improve degradation, dimensional stability, and final end-use performance of the bark fibre composite materials, it may be preferable to subject the bark fibres to chemical modification to improve interfacial bonding, prior to contacting with a hardenable matrix or resin. For example the bark fibres may be subjected to acetylation or sialylation conditions. Other surface treatment of the fibres may be carried out. The hardenable matrix or resin may contain an additive which improves interfacial bonding between the matrix and the bark fibres.

Where the bark fibres are in the form of long wool-like fibres or bark fibre filaments, prior to production of the bark fibre composite material the bark fibre filaments may optionally be processed so that they adopt a desired configuration. For example bark fibre filaments may be aligned or formed into a twine or yarn, e.g. by spinning, and optionally further processed to form a mat of aligned fibres or woven twine.

For example a spinning-type process may be used to process bark fibre filaments/fine fibres into a bark fibre yarn. In such processes, a fibre-bonding enhancer which promotes bonding of bark fibre filaments may optionally be added, for example during the spinning step, e.g. by injection of the fibre-bonding enhancer onto/into the bark fibre filaments. It is believed that, in the presence of friction-induced heat generated during the spinning process, the fibre-bonding enhancer promotes bonding of the bark fibre filaments to one another to generate bark fibre yarns in which the fibres adhere strongly to one another. Examples of suitable fibre-bonding enhancers include resins, such as almond resin.

As discussed above, the bark fibre yarn or twine may optionally be processed further to form further bark fibre materials, prior to contacting with a hardenable matrix and producing the hark fibre composite material. For example, the bark fibre yarn or twine may be woven into a woven mat.

In some embodiments, the feedstock rich in tree bark is subjected to hydration conditions (optionally following mechanical cleaning to remove non-bark material from the feedstock), and then cut or shredded to produce bark fibre filaments/fine fibres; the bark fibre filaments/fine fibres are spun into a bark fibre yarn or twine (optionally with addition of a fibre-bonding promoter such as almond resin); and the bark fibre yarn or twine is optionally woven into a woven mat. If desired, the woven mat may be cut or to the desired shape/size before carrying out additional processing to produce the bait fibre composite material.

As discussed above, some embodiments of the present disclosure relate to a bark fibre product which may be a bark fibre yarn, twine, or rope, or a mat formed using such a yarn, twine or rope (e.g. an intermediate product which can be used for producing bark fibre composite materials). In some embodiments the bark fibre product (e.g. yarn, twine, rope, mat or the like) is produced from, a feedstock rich in Eucalyptus tree bark (e.g. Eucalyptus globulus and/or Eucalyptus regnans tree bark). In some embodiments the bark fibre product (e.g. yarn, twine, rope, mat) comprises bark fibre and a fibre -bonding enhancer (e.g. a resin, such as almond resin). In some embodiments the bark fibre product is produced by a process comprising: spinning bark fibre to produce a yarn or twine, and optionally further processing the yarn or twine into a rope or mat. In some embodiments the bark fibre product is produced by a process comprising: contacting bark fibre with a fibre-bonding enhancer (e.g. a resin such as almond resin) and spinning to produce a yarn or twine, and optionally further processing the yarn or twine into a rope or mat.

In some embodiments, the bark fibres are in the form of bark fibre particles, such as chips, flakes or dust. Such particles may for example be obtained as byproducts when preparing bark fibre ribbons or "wool-like" bark fibre filaments. Such particles may be used for preparing isotropic composite products having characteristics similar to particle board. If desired bark fibre particles may be subjected to mechanical processing, such as milling, to reduce the average particle size (e.g. mean diameter) prior to use. Bark fibre particles having a desired size distribution may for example be obtained by using one or more meshes. In some embodiments, the bark fibre particles are 10-20 mesh particles (US mesh scale), in some embodiments, the bark fibre particles are 20-40 mesh particles. In some embodiments, the bark fibre particles are 40-60 mesh particles.

In some embodiments, the bark fibres are in the form of wet-spun ceiiulosic fibres. For example bark fibre filaments may be obtained as described above and then subjected to further chemical treatment to remove lignin and hemicellulose, thus providing ceiiulosic fibres. Wet-spinning or similar cellulose-regeneration processing may then be carried out on the ceiiulosic fibres to produce a preform or fabric weave.

A combination of different types of bark fibres may be used in the same bark fibre composite material. For example, a combination of bark fibre filaments and bark fibre particles (e.g. dust) may be used in the same bark fibre composite material.

Once the bark fibres have been obtained (e.g. in the form of a woven mat), they are used to prepare the bark fibre composite material. The bark fibres are contacted with a hardenable matrix (also known as a resin), and the resulting mixture is set/hardened, so as to produce the bark fibre composite materia!.

Accordingly there is also provided a process for producing a bark fibre composite material comprising a) bark fibres derived from a feedstock rich in Eucalyptus tree bark; and b) a matrix; the process comprising:

i) providing a feedstock rich in Eucalyptus tree bark;

ii) subjecting the feedstock rich in Eucalyptus tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and

iii) contacting the bark fibres with a hardenable matrix material and hardening the matrix material so as to produce the bark fibre composite material.

Whilst in some aspects the use of polymerised matrices other than those containing bio-based polymers is contemplated, more preferably the bark fibre composite material comprises a matrix comprising a bio- based polymer. The term bio- based polymer refers to a polymeric material prepared using a renewable source, i.e. a non petrochemical-derived source. For example a bio-based polymer may be a polymer prepared using a bio-based monomer. A bio-based monomer is a monomer derived from a renewable source such as a plant source, i.e. a source that is not a petrochemical-derived source. Examples of suitable bio-based polymers include polyesters derived from renewable inputs such as polyilactic acid), poly(3- hydroxybuyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly-(ethylene succinate), furan resins, lipid-based bioplastics (biopolymers formed by polymer reactions involving triglycerides or other fatty acids sourced from vegetable oils, e.g. modified acrylated epoxidised soy oil), and renewable polyurethanes and polyolefins. Poly(ethylene succinate) is produced from feedstocks such as ethylene glycol and succinic alcohol, which can be sourced renewably. Furyi resins are comprised of feedstocks such as furfuryl alcohol, and/or furfural. A multi-component hardenable matrix may be used if desired.

The preparation of the bark fibre composite material may be carried out in a variety of ways, depending on the nature of the bark fibres, the component(s) of the hardenable matrix, and the intended product/application. Processes such as casting into blocks, compression moulding, injection moulding, extrusion and spray casting may be used. Such processes may for example be carried out at temperatures just above the melting point of the hardenable matrix and for as short a duration as possible to prevent degradation of fibres. Where the hardenable matrix is present in liquid form and contains components which cure at or above a particular- temperature, such processes may be carried out at the curing temperature of the hardenable matrix.

In some embodiments, the bark fibre composite material may be produced by contacting the bark fibres with a hardenable matrix comprising a monomer (e.g. a bio- based monomer), and polymerising the monomer so as to produce the bark fibre composite material. Depending on the components used, polymerisation may be carried out at elevated temperature, in the presence of a catalyst and/or an initiator and/or a hardener.

In other embodiments, the bark fibre composite is produced by contacting the bark fibres with a hardenable matrix comprising a polymer (e.g. a. bio-based polymer) at elevated temperature, and reducing the temperature of the mixture so as to produce the bark fibre composite material. This type of approach may for example be used with bio-based polymers such as poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3- hydroxyvalerate). Such bio-based polymers may be produced by microorganisms under conditions known in the art.

The bark fibres may for example be contacted with a hardenabie matrix comprising a polymer (e.g. a bio-based polymer), and the bark fibre composite material produced by injection moulding. Alternatively, bark fibres may for example be contacted with a hardenabie matrix comprising a polymer (e.g. a bio-based polymer), and the bark fibre composite material produced by extrusion. These types of processes may for example be used with bio-based polymers such as poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(iactic acid).

Accordingly, also provided herein is a process for producing a bark fibre composite material comprising a) bark fibres derived from a feedstock rich in tree bark, and b) a matrix comprising a bio-based polymer; the process comprising:

i) providing a feedstock rich in tree bark;

ii) subjecting the feedstock rich in tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and

iii) contacting the bark fibres with a hardenabie matrix comprising a bio-based polymer and producing the bark fibre composite material by injection moulding or extrusion.

Also provided herein is a process for producing a bark fibre composite material comprising: a) bark fibres derived from a feedstock rich in Eucalyptus tree bark, and b) a matrix comprising a polymer; the process comprising:

i) providing a feedstock rich in Eucalyptus tree bark;

ii) subjecting the feedstock rich in Eucalyptus tree bark to chemical and/or mechanical processing, thereby producing bark fibres; and

iii) contacting the bark fibres with a hardenabie matrix comprising a polymer and producing the bark fibre composite material by injection moulding or extrusion.

In some embodiments, bark fibres (e.g. bark fibre bundles, bark fibre ribbons, woven mat, or bark fibre particles) and a hardenabie matrix may be introduced into a mould, and the resulting mixture set/hardened so as to produce the bark fibre composite material, e.g. whilst applying pressure to the mould. For example, where the hardenabie matrix comprises a monomer (e.g. a bio-based monomer), the mixture may be subjected to polymerisation conditions. Alternatively, where the hardenabie matrix comprises a bio-based polymer, the harder-able matrix and bark fibres may be introduced into a mould and contacted at elevated temperature such that the hardenable matrix is fluid (e.g. just above the melting temperature of the hardenable matrix), the temperature of the resulting mixture then being reduced, e.g. whilst applying pressure to the mould, resulting in solidification/hardening of the mixture and production of the bark fibre composite material.

In some embodiments the bark-fibre composite material is preparable by a process comprising mechanically cleaning the feedstock rich in tree bark to remove non-bark material (e.g. by scraping); cutting the cleaned bark into bark fibre ribbons; contacting the bark fibre ribbons in a mould with a hardenable matrix; subjecting the mixture to conditions so as to set or harden the mixture, e.g. whilst applying pressure to the mould, thereby producing the bark fibre composite material.

In some embodiments, the bark-fibre composite material is preparable by a process comprising subjecting the feedstock rich in tree bark to chemical processing conditions and producing bark fibre filaments (for example contacting the feedstock rich in tree bark with aqueous alkali (e.g. aqueous sodium hydroxide) at elevated temperature (e.g. at a temperature range of from 50 to 95°C, or from 75 to 90°C)); drying the bark fibre filaments at elevated temperature (e.g. at a temperature in the range of from 60 to 100°C, from 70 to 90°C, or about 80°C) whilst passing a stream of air over the bark fibre filaments (for example using a forced air oven); optionally aligning the bark fibre filaments and forming a mat of aligned fibres, or optionally forming the bark fibre filaments into a twine and further processing the twine to form a woven twine; optionally subjecting the processed bark fibre filaments to chemical modification so as to improve interfacial bonding between the bark fibre and the matrix; and contacting the bark fibres filaments with a hardenable matrix, the hardenable matrix optionally containing an additive which improves interfacial bonding between the bark fibre and the matrix, and subjecting the mixture to conditions so as to set or harden the mixture, thereby producing the bark fibre composite material. In those embodiments, the hardenable matrix and the bark fibre filaments may for example be formed into a composite material by compression moulding, injection moulding or extrusion. In some embodiments, the bark-fibre composite material is preparable by a process comprising providing bark fibre particles (such as chips, flakes or dust obtained for example as byproducts when preparing bark fibre ribbons or bark fibre filaments); contacting the bark fibre particles with a haraenable matrix; and subjecting the mixture to conditions so as to set or harden the mixture, thereby producing the bark fibre composite materia!. In those embodiments, the hardenable matrix and the bark fibre particles may for example be formed into a composite material by casting into blocks, spray casting, or injection moulding.

in some embodiments the bark-fibre composite material is preparable by a process comprising subjecting the feedstock rich in tree bark to chemical processing conditions and producing bark fibre filaments (for example contacting the feedstock rich in tree bark with aqueous alkali (e.g. aqueous sodium hydroxide) at elevated temperature (e.g. at a temperature range of from 50 to 95°C, or from 75 to 90°C)); drying the bark fibre filaments at elevated temperature (e.g. at a temperature in the range of from 60 to 100°C, from 70 to 90°C, or about 80°C) whilst passing a stream, of air over the bark fibre filaments (for example using a forced air oven); subjecting the bark fibre filaments to chemical treatment to remove iignin and hemiceliulose thereby providing ceiluiosic fibres; wet-spinning the cellulosic fibres; contacting the wet-spun cellulosic fibres with a hardenable matrix; and subjecting the mixture to conditions so as to set or harden the mixture, thereby producing the bark fibre composite material, in those embodiments, the hardenable matrix and the wet-spun cellulosic fibres may for example be formed into a composite material by injection moulding, spray casting or extrusion.

An embodiment is set out in Figure 8. In that embodiment a feedstock rich in tree bark (e.g. a feedstock rich in Eucalyptus globulus and/or Eucalyptus regnans tree bark) is optionally first subjected to mechanical, cleaning to remove non-bark material (not shown). The feedstock is subjected to hydration conditions (10) and the resulting material then cut or shred into fine bark fibres or bark fibre filaments (20). The fine bark fibres/bark fibre filaments are then spun into a bark fibre yarn or twine (30). During the spinning process a fibre-bonding enhancer such as almond resin is added (40) to improve adherence of the bark fibres. The resulting bark fibre yarn or twine is then weaved to produce a woven mat (50). If necessary, the woven mat is cut to the desired size (not shown). The woven mat is then contacted with a hardenabie matrix in a mould (60), and the mixture is subjected to conditions so as to set or harden the mixture (70), thereby producing the bark fibre composite material.

It will be understood that the use of bark materials of different forms, including bark strands, bark strips, bark ribbons and bark filaments, is encompassed by the present disclosure. Accordingly there is also provided a bark composite material comprising: a) a bark material (e.g. bark strands, bark strips, bark ribbons and/or bark filaments); and b) a matrix comprising a bio-based polymer. There is also provided a bark composite material comprising: a) a bark material derived from a feedstock rich in Eucalyptus tree bark; and b) a matrix comprising a polymer. In either case, preferably the bark material is derived from a feedstock rich in Eucalyptus globulus and/or Eucalyptus regnans tree bark.

The present disclosure is further described by the following examples. It is to be understood that the following description is for the purpose of describing particular embodiments only and is not intended to be limiting with respect to the above description.

Example 1

Eucalyptus globulus trees are harvested and stripped. The resulting waste, which is rich in bark, is used as a feedstock for producing a bark fibre composite material. The bark feedstock is mechanically cleaned by scraping or similar- to remove non-bark material. The cleaned bark is then cut into long fibre bundles or ribbons of approximately 10 cm in length (see e.g. Figure 2). The fibre bundles are introduced into a mould. A hardenabie matrix is also introduced in the mould and covers the fibre bundles. Pressure is applied and the mixture is subjected to conditions such that it cures/hardens and results, once set, in a bark fibre composite material containing the long fibre bundles within a bio-based polymer matrix. The bark fibre composite material is then removed from the mould. A photograph of the bark fibre composite material is shown in Figure 3. Example 2

Natural fibres are filamentary materials sourced from plants or animals, below provides some examples of fibres and their categorisation: Table 2

Natural fibres are also classified according to their fibre length, which tends to dictate dependence of material properties on orientation (Madsen, B & Gamstedt, EK 2013, 'Wood versus plant fibers: similarities and differences in composite applications' , Advances in Materials Science and Engineering), These are summarised in Table 3:

Table 3

In this context, the bark obtained from trees such as Eucalyptus globulus and Eucalyptus regnans can be classified as a long stalk, woody natural plant fibre which as a composite is likely to give rise to an anisotropic material. Example 3

The mechanical properties of a selection of natural and manufactured fibres are shown in Table 4:

Table 4

(Miao, M & Finn, N 2008, 'Conversion of Natural Fibres into Stractural Composites' , Journal of Textile Engineering, vol. 54, no. 6, pp. 165-177)

The tensile strength of carbon fibre (4000 MPa) indicates that it is significantly stronger in tension relative to any of the natural fibres (393- 1500 MPa). However, the tensile strength of carbon fibre far exceeds that required for many applications. A more apt benchmark is that of a commonly used structural steel tensile member. A comparison of the specific tensile strengths of carbon fibre, flax fibre and a commonly used steel reinforcing bar is shown in Table 5. Note that flax fibre was used as it gives a good indicative range of natural fibres' strength, and values are normalized by material density to permit comparison.

Table 5

These values support that the present bark fibre composite materials are sufficiently strong for a wide range of applications, and in fact exceed those of other widely used materials such as tensile steel.

Example 4

Details are provided regarding bio-based polymer-containing matrix materials used in the bark fibre composite material. Table 6 provides details of biopolymers and their physical properties:

Table 6

Example 5

The strength of the composite material can further be predicted using the modified "method of mixtures" equation. According to the method of mixtures the tensile strength of the composite, δ _c depends on the tensile strength of the fibre, Of, and the matrix, σ,„, and the fibre volume fraction V _f through the liner interpolation formula

Since the composite strength is known to depend on the fibre length and the fibre orientation, two additional factors are introduced, the fibre length factor, Tj] and the fibre orientation factor, η ₀ . The modified equation becomes

The tensile strength of cellulose fibre is taken to be 750 MPa (Lilholt et al } and for the matrix the value for the commercial product TechniGlue CA is used {data sheet ref } of 25 MPa. The fibre volume fraction is treated as a variable ranging from 0 to 0.6. Above 0.6 the clustering of fibres begins to create voids which weakens the physical characteristics of the composite {Lilholt et a! }. For randomly oriented short fibres the value for the orientation factor is ηο = 0.2.

The fibre length factor is more complicated; the commonly used value depends upon the average fibre length, L and a critical length Lc as follows

In what follows the ratio L/Lc is treated as a variable. The fibre length factor varies between 0 and 1 and its variation wi th the length ratio is shown in Figure 4.

With these values the tensile strength of the composite is calculated as a function of the fibre volume fraction, as shown in Figure 5. The values of the physical parameters used to generate Figure 5 are very conservative yet they demonstrate that the addition of cellulose fibres from tree bark can increase the tensile strength of the matrix material by a factor of three. An upper limit to the gain obtained by using cellulose fibres can be obtained using the unmodified method of mixtures formula from which an increase of over 18 fold is found. Consequently, the cellulose fibres will increase the tensile strength of the composite by a factor between three and eighteen. Example 6

The effect of changing the biopolymer matrix material in a bark fibre composite was examined. The biopolvmers listed in Table 7 below were considered. The average values of tensile strength are shown. Table 7

The assumed nominal value for the bark fibre tensile strength is taken to be 750 MPa and a fibre length factor (appropriate for long fibre bundles) as 0.75. Then using the modified method of mixtures formula above, the tensile strength of each of the biopolvmers in the table above is calculated as a function of the fibre length ratio, as shown in Figure 6. The curves denoted (a) correspond to a fibre volume of 0.6, those denoted (b) to 0.4, and those denoted (c) to 0.2. In each group of curves, the curves descend in the order: poly(lactic) acid, poly(butylene succinate), poly(3- hydroxybutyrate), poly(hydroxybutyrate-co-hydroxyvalerate), modified acrylated epoxidised soy oil.

The general monotonic growth of these curves show that increasing the fibre length increases the composite's tensile strength as does increasing the fibre volume fraction (up to the practical limit of 0.6).

Tree bark fibre, and in particular peeling tree bark fibre such as that obtained from Eucalyptus globulus and/or Eucalyptus regnans, is a suitable replacement for materials such as glass fibre and, in particular, carbon fibre, substantiated by significant cost, mechanical and environmental advantages. There are a wealth of applications stemming from the use of this material in composite materials, ranging from construction, transport, sporting and domestic industries. For example, Figure 7 shows a structural panel containing a bark fibre composite material according to the present disclosure.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.