NANOCOMPOSITE ELASTOMERS

Abstract

A composite material comprising an elastomer and nanocellulose. The nanocellulose may comprise a nanocellulose material derived from plants having C4 leaf anatomy, or a nanocellulose material derived from a plant material having a lesser amount of lignin than hemi-cellulose, or a nanocellulose having a hemicellulose content of from 25% to 55% by weight of the nanocellulose material, or a nanocellulose comprising nanofibrils having a diameter of up to 5 nm, or a nanocellulose comprising nanocellulose material of plant origin comprising nanocellulose particles or fibres having an aspect ratio of at least 250, or the composite material having a stiffness of not greater than 2.5 times the stiffness of the elastomer without the nanocellulose material being present, or the nanocellulose particles or fibres being derived from a plant material having a hemicellulose content of 30% or higher (w/w). The nanocellulose may be derived from arid Spinifex.

Claims

1. A composite material comprising an elastomer and nanocellulose, the nanocellulose comprising a nanocellulose material derived from plants having C4 leaf anatomy.

2. A composite material comprising an elastomer and nanocellulose, the nanocellulose comprising a nanocellulose material derived from a plant material having a lesser amount of lignin than hemicellulose.

3. A composite material comprising an elastomer and nanocellulose, the nanocellulose having a hemicellulose content of from 25% to 55% by weight of the nanocellulose material.

4. A composite material comprising an elastomer and nanocellulose, the nanocellulose comprising nanofibrils having a diameter of up to 5 nm, preferably a diameter within the range of 3-4 nm.

5. A composite material comprising an elastomer and nanocellulose, the nanocellulose comprising nanocellulose material of plant origin comprising nanocellulose particles or fibres having an aspect ratio of at least 250.

6. A composite material comprising an elastomer and nanocellulose, the composite material having a stiffness of not greater than 2.5 times the stiffness of the elastomer without the nanocellulose material being present.

7. A composite material as claimed in claim 1 wherein the nanocellulose comprises a nanocellulose material of plant origin comprising nanocellulose particles or fibres derived from a plant material having a hemicellulose content of 30% or higher (w/w).

8. A composite material as claimed in claim 7 wherein the plant material has a hemicellulose content of from 30 to 55% w/w, or from 30 to 50% w/w, or from 36 to 48% w/w, or from 40 to 48% w/w or from 42 to 47% w/w, or any intermediate range within the ranges set out above.

9. A composite material as claimed in claim 1 wherein the nanocellulose has a hemicellulose content of 30% or higher (w/w), or a hemicellulose content of at least 36wt %, or at least 40wt % or at least 42wt % and not more than 55wt %, or not more than 50wt %, or not more than 48wt %, or not more than 47wt %, or from 30 to 55% w/w, or from 30 to 50% w/w, or from 36 to 48% w/w, or from 40 to 48% w/w or from 42 to 47% w/w.

10. A composite material as claimed in claim 1 wherein the nanocellulose comprises nanocellulose particles or fibres have an aspect ratio of between 250 to 10,000, or between 250 to 5000, or between 250 to 1000.

11. A composite material as claimed in claim 10 wherein the range of the aspect ratio of the nanocellulose particles or fibres has a lower limit of 250, or 266, or 280, or 300, or 400, or 500.and the upper range of the aspect ratio of the nanocellulose particles or fibres is 10,000, or 5000, or 4000, or 3000, or 2000, or 1000, or 958, or 800, or 700, or 600, or 550.

12. A composite material as claimed in claim 10 wherein the nanocellulose particles or fibres have an aspect ratio of between 260 to 1000, or between 266 to 1000, or between 266 to 958.

13. A composite material as claimed in claim 1 wherein the nanocellulose comprises nanocellulose particles or fibres having a diameter of up to 20 nm, or up to 15 nm, or up to 10 nm, or up to 8 nm, or up to 6 nm, or up to 5 nm.

14. A composite material as claimed in claim 1 wherein the nanocellulose comprises nanocellulose particles or fibres comprising primary nanofibrils having a diameter of 3-4 nm.

15. A composite material as claimed in claim 1 wherein the nanocellulose comprises nanocellulose particles or fibres including essentially no particles or fibres having a diameter of greater than 20 nm.

16. A composite material as claimed in claim 1 wherein the nanocellulose comprises nanocellulose particles or fibres having a length that falls within the range of from 200 nm up to 10 μm.

17. A composite material as claimed in claim 1 wherein nanocellulose is derived from a grass species having C4 anatomy, or derived from a drought-tolerant grass species, or derived from an arid grass species.

18. A composite material as claimed in claim 17 wherein the nanocellulose is derived from Australian native arid grass known as “spinifex' from the genera comprising Triodia, Monodia, or from Digitaria sanguinalis (L.) Scopoli, Panicum coloratum L. var. makarikariense Goossens, Brachiaria brizantha (Hochst. Ex A. Rich) Stapf, D. violascens Link, P. dichotomiflorum Michaux, B. decumbens Stapf, Echinochloa crus-galli P. Beauv., P. miliaceum L., B. humidicola (Rendle) Schweick., Paspalum distichum L., B. mutica (Forsk.) Stapf, Setaria glauca (L.) P. Beauv, Cynodon dactylon (L.) Persoon, Panicum maximum Jacq., S. viridis (L.) P. Beauv, Eleusine coracana (L.) Gaertner, Urochloa texana (Buckley) Webster, Sorghum sudanense Stapf, E. indica (L.) Gaertner, Spodiopogon cotulifer (Thunb.) Hackel, Eragrostis cilianensis (Allioni) Vignolo-Lutati, Chloris gayana Kunth, Eragrostis curvula, Leptochloa dubia, Muhlenbergia wrightii, E. ferruginea (Thunb.) P. Beauv., Sporobolus indicus R. Br. var. purpureo-suffusus (Ohwi) T. Koyama, Andropogon gerardii, Leptochloa chinensis (L.) Nees and Zoysia tenuifolia Willd, or from Anigozanthos, Austrodanthonia, Austrostipa, Baloskion pallens, Baumea juncea, Bolboschoenus, Capillipedium, Carex bichenoviana, Carec gaudichaudiana, Carex appressa, C.tereticaulis, Caustis, Centrolepis, Chloris truncate, Chorizandra, Conostylis, Cymbopogon, Cyperus, Desmocladus flexuosa, Dichanthium sericeum, Dichelachne, Eragrostis, Eurychorda complanata, Evandra aristata, Ficinia nodosa, Gahnia, Gymnoschoenus sphaerocephalus, Hemarthria uncinata, Hypolaeana, Imperata cylindrical, Johnsonia, Joycea pallid, Juncus, Kingia australis, Lepidosperma, Lepironia articulate, Leptocarpus, Lomandra, Meeboldina, Mesomelaena, Neurachne alopecuroidea, Notodanthonia, Patersonia, Poa, Spinifex, Themedo triandra, Tremulina tremula, Triglochin, Triodia and Zanthorrhoea, Aristida pallens (Wire grass), Andropogon gerardii (Big bluestem), Bouteloua eriopoda (Black grama), Chloris roxburghiana (Horsetail grass), Themeda triandra (Red grass), Panicum virgatum (Switch grass), Pennisetum ciliaris (Buffel grass), Schizachyrium scoparium (Little bluestem), Sorghatrum nutans (Indian grass) and Stipa tenacissima (Needle grass), wheat straw, or Esparto (provided by Stipa tenacissima and Lygeum spartum, both Poaceae family), Oyat (which is the French common name for Ammophila arenaria, also from the Poaceae family), Miscanthus and plants that form tumbleweeds, including tumbleweed forming plants form the families Amaranthaceae and Chenopodiaceae), Amaryllidaceae, Apiaceae, Asphodelaceae, Asteraceae, Brassicaceae, Boraginaceae, Caryophyllaceae, Fabaceae, Lamiaceae and Poaceae.

19. A composite material as claimed in claim 18 wherein the nanocellulose is derived from T. pungens, T. shinzii, T. basedowii, or T. longiceps.

20. A composite material as claimed in claim 1 wherein the nanocellulose comprises a nanocellulose material of plant origin comprising nanocellulose particles or fibres derived from a plant material having a hemicellulose content of 30% or higher (w/w), or a hemicellulose content of from 30 to 55% w/w, or from 30 to 50% w/w, or from 36 to 48% w/w, or from 40 to 48% w/w or from 42 to 47% w/w, or any intermediate range within the ranges set out above.

21. A composite material as claimed in claim 1 wherein the amount of nanocellulose that is present in the composite material ranges from 0.05% wt to 25% wt (calculated as a weight percentage of the total weight of the nanocellulose and elastomer components, that is, excluding other chemicals added during compounding such as vulcanising agents, surfactants and accelerators), or from 0.1% wt to 25% wt, or from 0.2% wt to 20% wt, or from 0.3% wt to 15% wt, or from 0.5% wt to 10% wt, or from 0.5% wt to 7.5% wt, or from 0.5% wt to 7% wt, or from 0.5% wt to 5% wt, or from 0.5% wt to 2.5% wt, or about 0.5% wt, or about 1% wt, or less than 5% wt nanocellulose or between 0.1% to 5% wt or from 0.1 to 4% or from 0.1 to 3%, or from 0.1 to 2% or from 0.1 to 1% or from 0.2 to 0.9% or from 0.2 to 0.8% or from 0.25 to 0.75% or from 0.05 to 0.5% wt or from 0.1 to 0.4% wt nanocellulose.

22. A composite material as claimed in claim 1 wherein the elastomer comprises natural rubber or a polyurethane or polyisoprene (synthetic natural rubber), polybutadiene, polychloroprene, butyl rubber, styrene-butadiene rubber, nitrile rubber, hydrogentated nitrile rubber (HNBR), ethylene propylene rubber, ethylene propylene diene rubber (EPDM), chlorosulphonated polyethylene (CSM), chlorinated polyethylene, polysulphide rubber, ethylene acrylic rubber, fluorocarbon rubber, polytetrafluoroethylene-propylene, epichlorohydrin rubber, polyacrylic rubber, silicone rubber, fluorosilicone rubber, polyphosphazene rubber, polyoctenylene, polypropylene oxide rubber, polynorbornene, polyether block amides, EVA rubber, styrenic block copolymers such as SEBS (styrene, ethylene-co-butylene, styrene blocks), SEPS (styrene, ethylene-co-propylene, styrene blocks), SIS (styrene, isoprene, styrene blocks) or other segmented elastomers such as copolyester thermoplastic elastomers (TPEs), or any combination of the above elastomers.

23. A composite material as claimed in claim 1 wherein the composite material further comprises one or more additives selected from zinc oxide, surfactants including but not limited to stearates, anti-oxidants, waxes, vulcanising agents and vulcanising accelerators.

24. An article made from a composite material as claimed in claim 1.

25. An article as claimed in claim 24 wherein the article comprises condoms, gloves, catheter balloons, vehicle tyres, components for shoes, conveyor belts, wear liners, components for furniture (such as armrests), suspension bushes, or blades for windscreen wipers.

26. A dipped article comprising a composite material as claimed in claim 1.

27. A dipped article as claimed in claim 26 wherein the dipped article comprises a condom, glove or catheter balloon.

28. A condom made from natural rubber latex or polyisoprene with tensile strength greater than 31 MPa, or greater than 35 MPa or greater than 40 MPa or greater than 45 MPa.

29. A condom as claimed in claim 28 wherein the condom has a maximum tensile strength of up to 60 Mpa, or up to 55 Mpa, or up to 50 MPa, or up to 45 Mpa.

30. A condom made from natural rubber latex or polyisoprene with a normalised air burst pressure of greater than 0.036 kPa/μm or greater than 0.040 kPa/μm or greater than 0.045 kPa/μm or greater than 0.050 kPa/μm.

31. A condom as claimed in claim 30 wherein the condom has a maximum normalised air burst pressure of up to 0.007 kPa/μm, or up to 0.065 kPa/μm, or up to 0.060 kPa/μm, or up to 0.055 kPa/μm.

32. A condom made from natural rubber latex or polyisoprene with tensile strength greater than 31 MPa, or greater than 35 MPa or greater than 40 MPa or greater than 45 MPa or a normalised air burst pressure of greater than 0.036 kPa/μm or greater than 0.040 kPa/μm or greater than 0.045 kPa/μm or greater than 0.050 kPa/μm and a tensile stress at 500% extension of lower than 10 MPa or lower than 8 MPa or lower than 6 MPa or lower than 4 MPa or lower than 2 MPa or lower than 1.5 MPa or lower than 1 MPa.

33. A condom as claimed in claim 32 wherein the condom has a maximum tensile strength of up 50 MPa.

34. A condom as claimed in claim 32 wherein condom has a maximum normalised air burst pressure of up to 0.060 kPa/μm, or up to 0.055 kPa/μm.

35. A condom as claimed in 28 having a thickness of from 50-90 microns, or a thicknesses in the range 36-50 microns, or a thickness of less than 45 μm or less than 40 μm or less than 35 μm or less than 30 μm or less than 25 μm in the case that these are made using natural rubber latex or polyisoprene.

36. A condom made from polyurethane having a thickness of less than 10 μm and a normalised air burst pressure of greater than 0.036 kPa/μm or greater than 0.040 kPa/μm or greater than 0.045 kPa/μm or greater than 0.050 kPa/μm.

37. A method for producing an article from a composite material as claimed in claim 1, the method comprising forming a mixture of the nanocellulose and a suspension or solution of elastomeric material, dipping a mould or a former into the mixture, removing the mould or the former from the mixture such that an adherent layer of the mixture is formed on a surface of the mould or the former and allowing the adherent layer of the mixture to dry or set.

38. A method as claimed in claim 37 comprising dipping the mould former back into the mixture one or more further times to form additional layers of adherent mixture, the additional layers of adherent mixture forming on an underlying layer of adherent mixture.

39. A method as claimed in claim 38 wherein the mould or former is dipped back into the mixture after a previous adherent layer has dried or set.

40. A method as claimed in claim 37 wherein the nanocellulose has a hydroxylated surface, or the surface of the nanocellulose is modified to attach functional groups to the surface of the nanocellulose, or the surface of the nanocellulose is modified by TEMPO oxidation, carboxymethylation, adsorption of surfactants, adsorption of macromolecules, esterification, acetylation, acylation, cationisation, silylation, carbamination, click chemistry, molecular grafting, or polymer grafting.

41. A condom as claimed in claim 36 wherein the condom has a maximum normalised air burst pressure of up to 0.007 kPa/μm, or up to 0.065 kPa/μm, or up to 0.060 kPa/μm, or up to 0.055 kPa/μm.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0072] FIG. 1 shows a graph of tensile stress vs tensile strain for a polyurethane rubber having (a) no nanocellulose added and (b) 0.5% wt nanocellulose added;

[0073] FIG. 2 shows a graph of tensile stress vs tensile strain for a natural latex having (a) no nanocellulose added and (b) 1.0% wt nanocellulose added; and

[0074] FIG. 3 shows a graph of tensile curves of neat TPU and CNC-TPU nanocomposite material as described in example 15.

DESCRIPTION OF EMBODIMENTS

[0075] It will be appreciated that the following examples have been provided for the purpose of illustrating preferred embodiments of the present invention. Therefore, it would be understood that the present invention should not be considered to be limited solely to the features as described in the examples.

EXAMPLE 1

[0076] Nanocomposites were prepared via reactive extrusion of a stable, very dry (<300 ppm water) PTMEG 1000 polyol-CNC suspension with dimethyl diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO). Table 1 summarizes the amount of each components used for making blank TPU and its nanocomposites with CNC (CNC was obtained from acid hydrolysis of Spinifex pulp using 40% (v/v) sulphuric acid for 3 hours at 45° C.).

TABLE-US-00001 TABLE 1 CNC Hard Polyol content Isocyanate segment flow rate Sample Polyol type (%) index ratio Stoichiometry (g/h) X1 PTMEG1000 — 1 0.44 1 1797.6 X2 PTMEG1000 + CNC 0.465 1 0.44 1 1812.5 X3 PTMEG1000 + CNC 0.465 1 0.44 1.01 1812.5 X4 PTMEG1000 + CNC 0.465 1 0.44 1.02 1812.5 X5 PTMEG1000 + CNC 0.465 1 0.44 1.03 1812.5 BDO Die MDI flow flow rate Torque pressure Sample rate (g/h) (g/min) (%) (bar) X1 1157.6 254.8 26-27 15 X2 1157.6 254.8 26 16 X3 1169.1 254.8 30-31 21-22 X4 1180.7 254.8 39-40 32-33 X5 1192.3 254.8 43 37-38 Young's Modulus Tensile strain Tensile stress Work at fracture Sample (MPa) (go) (MPa) (MJ m-3) X1 14.5 ± 1.2 1124 ± 31 41 ± 3 237 ± 10 X2 16.6 ± 0.3 1115 ± 41 43 ± 1 237 ± 6  X3 14.5 ± 0.4 1098 ± 21   48 ± 1.2 257 ± 6  X4 14.5 ± 0.6 1023 ± 11 54 ± 2 250 ± 9  X5   16 ± 0.7 1012 ± 25   59 ± 3.2 256 ± 14

[0077] Nanocellulose was present in an amount of 0.5% wt by weight of the composite (see X5 in table 1 above. X1 being the unfilled control).

[0078] In order to reduce the effect of moisture, PTMEG and stable PTMEG/CNC suspensions were dried using thin/wiped film evaporator (VTA, Niederwinkling, Germany) achieving water contents of below 300 ppm, and purged with nitrogen gas before storage in an air-tight bottle until required for reactive extrusion. The dispersion of spinifex CNC in PTMEG was prepared using 0.83% (w/w) CNC using a proprietary mixing process. Before doing the extrusion, PTMEG and MDI both were melted at 55° C. overnight and the chain extender (BDO) was dried using molecular sieve in a bottle, then all of these precursors were sealed with an air-tight lid and nitrogen gas purge.

TABLE-US-00002 Composition used for producing TPU based on blank PTMEG 1000 Hard segment Isocyanate Stoichi- Polyol BDO ratio ratio ometry (wt %) MDI (wt %) (wt %) 0.44 1 1 56 36.06 7.94

[0079] FIG. 1 shows a graph of tensile stress vs tensile strain for the base TPU (with no nanocellulose), which is the lower curve in FIG. 1 and for the nanocellulose/TPU composite material, which is the upper curve in FIG. 1. As can be seen from FIG. 1, there was no increase in stiffness of the composite material, when compared to the base TPU, at low strain. A 45% increase in toughness was observed. There was no reduction in elongation to break.

EXAMPLE 2

[0080] In example 2, a composite material was produced from nanofibrillated cellulose and natural rubber latex (non-vulcanised). Nanocellulose was present in an amount of 1% wt of the composite.

[0081] The nanocellulose suspension (0.3-1%) was obtained via high-pressure homogenisation of spinifex pulp (T. Pungens) fibre. The nanocellulose used had a hemicellulose content of 42% w/w and a fibre diameter of 3.5 nm. Prior to mixing, the pre-vulcanized rubber latex (Gedeo concentrated mould making formula, Pebeo, France) was diluted to 20-50 mg/mL (on dry weight basis) depending on final composition (0.25, 0.5 and 1 wt. %). Both the suspensions were mixed together by magnetic stirring for 2-3 h, homogenised (using a hand held rotor-stator homogeniser) for 1-2 minutes and allowed to gently stir for another hour to degas. After degassing, the homogeneous mixture was cast onto Teflon petri-dishes, dried at 40° C. for 12 h-50 h (depending on nanocellulose content and volume) to obtain control and nanocomposite films.

[0082] FIG. 2 shows a graph of tensile stress vs tensile strain for the base natural rubber (with no nanocellulose), which is the lower curve in FIG. 2 and for the nanocellulose/natural rubber composite material, which is the upper curve in FIG. 2. FIG. 2 shows that although there was some increase in stiffness at low strain, this increase is not significant. However, toughness increased by 125%. There was no reduction in elongation to break.

EXAMPLE 3

Nanocellulose Reinforced Synthetic Rubber (Polyisoprene)

[0083] A composite of synthetic rubber (Cariflex IR401 polyisoprene latex in water) and nanocellulose (NFC with 42 wt. % hemicellulose content and 3-4 nm fibre diameter) was fabricated where the NFC was present at a loading of 0.53 wt. % (dry NFC mass) and rubber made up 99.47 wt. % (dry rubber mass) of the total nanocellulose plus rubber dry mass. The NFC was well dispersed as a 3.5% w/v aqueous dispersion and this was added to the Cariflex IR401 latex dispersion which had a solids content of 66% wt. Addition was done at room temperature and the mixture was stirred gently for 1 hour after addition. Sulfur (0.6% wt. of total solids mass), ZnO (0.2% wt. of total solids mass) and zinc diethyl dithiocarbamate (ZDEC, 0.5% wt.) were then added slowly to the dispersion to avoid shocking the latex. After all additions were completed, stirring was continued for 1 hour. After that stirring was stopped and stirred just once a day for 30 min. The latex was kept for 48 hours at room temperature before casting. The composite was cast into a glass petri dish and was cured for 20 minutes at 125-130° C. in casting oven under the flow of nitrogen.

EXAMPLE 4

Nanocellulose Reinforced Nitrile Butadiene Rubber (NBR)

[0084] A composite of nitrile butadiene rubber and nanocellulose (NFC with 42 wt. % hemicellulose content and 3-4 nm fibre diameter) was fabricated where the NFC was present at a loading of 6.5% wt. (dry NFC mass) and rubber made up 93.5% wt. (dry rubber mass) of the total nanocellulose plus rubber dry mass.

[0085] 5 g of solid NBR was dissolved in 100 mL of dimethylformamide (DMF). NFC was then dispersed in a separate quantity of DMF and 10 mL of a 3.5 w/v % NFC in DMF dispersion was added to the NBR/DMF dispersion and stirred overnight at room temperature. The mixture was cast onto a glass surface, allowed to dry and curing was then done at 45° C. in casting oven under the flow of nitrogen for 48 hours.

[0086] Various methods for modifying the nanocellulose surface chemical functionality prior to incorporation with an elastomer, as specified in examples 5 to 10 set out below.

EXAMPLE 5

Sodium Hydroxide Treated (Delignified) NFC (NFC Produced After Delignification Process)

[0087] Triodia pungens water-washed ground grass was treated with a 2% (w/v) sodium hydroxide solution at 80° C. for 2 hours followed by rinsing with hot water (60° C.). The alkali treated fibres contained 31% (w/w) cellulose, 43% (w/w) hemicellulose and 26% (w/w) lignin. An aqueous dispersion of these fibres with 0.5% (w/v) concentration, was then passed through a high pressure homogeniser (Panda 2 K NS1001L, GEA Niro Soavi S.p.A, Italy) at a pressure of 700 bar for 2, 4 or 8 passes.

EXAMPLE 6

Bleached NFC

[0088] Alkali treated (delignified) fibres were bleached twice using a 1% (w/v) aqueous solution of sodium chlorite at 70° C. for 1 h with a 30:1 solvent to fibre ratio at pH 4 (pH adjusted with addition of a few drops of glacial acetic acid). The bleached pulp contained 55% (w/w) cellulose, 42% (w/w) hemicellulose and 3% (w/w) lignin. A 3 wt % dispersion of bleached pulp in water was then passed through high pressure homogeniser (Panda 2 K NS1001L, GEA Niro Soavi S.p.A, Italy) at 700 bar pressure two times. The average diameter of individual nanofibres and bundles of nanofibres were 4.5±1.5 nm and 9.7±7.1 nm, respectively.

EXAMPLE 7

NFC Obtained After Carboxymethyl Treatment of Both Sodium Hydroxide Treated (Delignified) and Bleached Fibres

[0089] Both delignified and bleached fibres were pretreated with the carboxymethylation procedure. Briefly, about 5 g of each fibre sample was solvent exchanged with ethanol using a centrifuge for 10 min with 5 repeats. Then fibres were impregnated in a 2% (w/v) solution of monochloroacetic acid in 45 mL of isopropanol for 30 minutes followed by addition to this mixture of a 2.5% sodium hydroxide solution in methanol and 180 mL of isopropanol at 80° C. for 1 h. The carboxymethylated fibres were washed with 2 L of deionised water, then a solution of 0.5 mL of acetic acid in 180 mL of deionised water and finally with deionised water. The surface carboxyl groups on the nanocellulose were converted to sodium form by soaking treated fibres in a solution of 8.3 g of sodium bicarbonate in 200 mL of deionised water. Treated samples were finally filtered and washed with deionised water. Dispersions of 5 mg/mL of alkali treated (delignified) and 10 mg/mL bleached fibres after carboxymethyl treatment were homogenised using a laboratory table top GEA homogenizer at 700 bar pressures with two passes. The average NFC diameter of alkali and bleached carboxymethylated samples was 5.6±1.1 nm and 4.2±1 nm, respectively. The introduction of carboxylate ions via this partial carboxymethylation of cellulose fibres resulted in electrostatic repulsion between the nanofibrils and this repulsion makes the nanofibres easier to disperse in elastomer formulations and also limits aggregation of the nanofibres.

EXAMPLE 8

NFC Obtained After Choline Chloride/Urea Treatment on Sodium Hydroxide Treated (Delignified) Fibres

[0090] Sodium hydroxide treated (delignified) fibre was added to a solution prepared by heating a choline chloride and urea mixture with a 2:1 molar ratio at 100° C. with the final concentration of 3.7 wt % and stirred for 2 hours at that temperature followed by rinsing with hot water. Dispersions of 0.5 wt % treated fibres in water were then homogenised using a GEA homogenizer at 700 bar pressure for 2 or 4 passes. The average diameter of nanofibers produced from 2 passes of homogenisation was 9±3.2 nm.

EXAMPLE 9

Bleached CNC

[0091] Bleached fibres of nanocellulose were hydrolysed using a 40% (v/v) sulphuric acid solution at 45° C. for 3 hours. To remove excess aqueous acid and the dissolved amorphous segments of the fibres, the digested suspension was centrifuged 4 times at 4750 rpm for 20 minutes, and then dialysed in deionised water until the pH reached 7. The hydrolysed fibre was then re-suspended in deionised water using an ultrasonic probe (Model Q500 Sonicator, from QSonica, Newtown, United States) at 25% amplitude, with a frequency of 20 kHz for 20 minutes with an output energy of 500 W. The obtained nanocrystals had an average diameter of 3.45±0.75 nm and length of 497±106 nm.

EXAMPLE 10

Positively Charged Bleached NFC using PDDA

[0092] A solution of poly (diallyldimethylammonium chloride) (PDDA) (20 wt%, pH 10) was dropped into a suspension of bleached NFC at the ratio of 1:10 and stirred for 30 min followed by ultasonication for 5 min. In order to remove excess PDDA that was not effectively absorbed on the surface of the NFC, the NFC/PDDA dispersion was centrifuged at a speed of 20,000 rpm followed by rinsing with deionised water. These steps were repeated 3 times. The rinsed NFCs with the positive charge were then redispersed in deionised water using ultrasonication and magnetic stirring.

[0093] Some examples for manufacture of nanocomposite elastomer condoms will now be provided.

EXAMPLE 11

Fabrication of a 0.1 wt. % Nanocellulose (Delignified)-Latex Composite Condom

[0094] Pre-vulcanised natural rubber latex (supplied by Synthomer) was diluted to 45 wt. % solids content by adding to it a dispersion of delignified nanocellulose derived from Spinifex grass (nanocellulose described in Example 5) in alkali water (pH 10.5) so that the amount of nanocellulose in the dispersion was 0.1 wt. % of the latex solids content. The latex-nanocellulose dispersion was then stirred using an overhead stirrer at 50 rpm overnight at 25 to 30° C.

[0095] Following stirring, a condom-shaped glass former was immersed slowly into the latex-nanocellulose dispersion followed by slow and gradual removal from the latex. The film was dried using hot air and the dipping process was repeated. Following the second dip, the latex-nanocellulose film was dried on the former at 50° C. for 5 minutes in an oven, followed by 125° C. for 5 minutes. The film was then leached in water and final drying at 125° C. was carried out for 25 minutes in an oven. Following drying, the latex-nanocellulose composite condoms containing 0.1 wt. % nanocellulose were removed from the glass formers and their mechanical properties tested. The resultant condoms were parallel-side with smooth texture and 54 mm nominal width. Condom membrane thickness was 45 μm. Air burst pressure was 1.4 kPa with an air burst volume of 38.5 L as tested according to the ISO4074:2002 standard. Tensile testing of the condoms showed stress at break to be 27 MPa and the stress at 500% elongation was 1.9 MPa.

EXAMPLE 12

Fabrication of a 0.1 wt. % Nanocellulose (Choline Chloride Treated)-Latex Composite Condom

[0096] Pre-vulcanised natural rubber latex (supplied by Synthomer) was diluted to 45 wt. % solids content by adding to it a dispersion of choline chloride-treated nanocellulose derived from Spinifex grass (nanocellulose described in Example 8) in alkali water (pH 10.5) so that the amount of nanocellulose in the dispersion was 0.1 wt. % of the latex solids content. The latex-nanocellulose dispersion was then stirred using an overhead stirrer at 50 rpm overnight at 25 to 30° C.

[0097] Following stirring, a condom-shaped glass former was immersed slowly into the latex-nanocellulose dispersion followed by slow and gradual removal from the latex. The film was dried using hot air and the dipping process was repeated. Following the second dip, the latex-nanocellulose film was dried on the former at 50° C. for 5 minutes in an oven, followed by 125° C. for 5 minutes. The film was then leached in water and final drying at 125° C. was carried out for 25 minutes in an oven. Following drying, the latex-nanocellulose composite condoms containing 0.1 wt. % nanocellulose were removed from the glass formers and their mechanical properties tested. The resultant condoms were parallel-side with smooth texture and 54 mm nominal width. Condom membrane thickness was 45 μm. Air burst pressure was 1.3 kPa with an air burst volume of 33 L as tested according to the IS04074:2002 standard. Tensile testing of the condoms showed stress at break to be 27 MPa and the stress at 500% elongation was 0.7 MPa.

COMPARATIVE EXAMPLE 13

Fabrication of a Nanocellulose-Free (Latex Only) Condom (for Comparison Purposes)

[0098] Pre-vulcanised natural rubber latex (supplied by Synthomer) was diluted to 45 wt. % solids content using alkali water (pH 10.5) and stirred using an overhead stirrer at 50 rpm overnight at 25 to 30° C.

[0099] Following stirring, a condom-shaped glass former was immersed slowly into the latex dispersion followed by slow and gradual removal from the latex. The film was dried using hot air and the dipping process was repeated. Following the second dip, the latex film was dried on the former at 50° C. for 5 minutes in an oven, followed by 125° C. for 5 minutes. The film was then leached in water and final drying at 125° C. was carried out for 25 minutes in an oven. Following drying, the latex condoms were removed from the glass formers and their mechanical properties tested. The resultant condoms were parallel-side with smooth texture and 54 mm nominal width. Condom membrane thickness was 45 μm. Air burst pressure was 1.1 kPa with an air burst volume of 37.5 L as tested according to the ISO4074:2002 standard.

EXAMPLE 14

Fabrication of a 0.4 wt. % Nanocellulose (Delignified)-Latex Composite Condom

[0100] Pre-vulcanised natural rubber latex (supplied by Synthomer) was diluted to 45 wt. % solids content by adding to it a dispersion of delignified nanocellulose derived from Spinifex grass (nanocellulose described in Example 5) in alkali water (pH 10.5) so that the amount of nanocellulose in the dispersion was 0.4 wt. % of the latex solids content. The latex-nanocellulose dispersion was then stirred using an overhead stirrer at 50 rpm overnight at 25 to 30° C.

[0101] Following stirring, a condom-shaped glass former was immersed slowly into the latex-nanocellulose dispersion followed by slow and gradual removal from the latex. The film was dried using hot air and the dipping process was repeated. Following the second dip, the latex-nanocellulose film was dried on the former at 50° C. for 5 minutes in an oven, followed by 125° C. for 5 minutes. The film was then leached in water and final drying at 125° C. was carried out for 25 minutes in an oven. Following drying, the latex-nanocellulose composite condoms containing 0.1 wt. % nanocellulose were removed from the glass formers and their mechanical properties tested. The resultant condoms were parallel-side with smooth texture and 54 mm nominal width. Condom membrane thickness was 60 μm. Air burst pressure was 1.1 kPa with an air burst volume of 31.5 L as tested according to the ISO4074:2002 standard.

[0102] Some examples of thermoplastic polyurethane (TPU)/nanocellulose composite made by solvent casting will now be provided.

EXAMPLE 15

Preparation of T. pungens CNC-Based Nanocomposite

[0103] In order to evaluate the property performance of T. pungens CNC, a nanocomposite of CNC and an aliphatic TPU (Tecoflex EG-80A with the specific gravity of 1.04 g/cm3 was purchased from Lubrizol (Lubrizol Advanced Materials, Cleveland, Ohio, United States)) was produced. T. pungens CNC and TPU were vacuum-dried at 70° C. for 24 hours and TPU polymer was consequently dissolved in dimethylformamide (DMF-EMD chemicals, Saudi Arabia) at room temperature by stirring. A dispersion of freeze-dried CNC in DMF was stirred for 1.5 hours then subjected to ultrasonication at 25% amplitude for 5 minutes, whereby the nanocellulose gel was formed. This procedure was repeated three times until the stable dispersion of CNC in DMF was obtained. Cellulose dispersion was subsequently added to the TPU polymer solution at 1 wt % concentration and mixed overnight at room temperature using a magnetic stirrer. To ensure a high level of mixing prior to casting, the nanocomposite was mixed for a further 5 minutes with an ultrasonic probe at 25% amplitude, followed by stirring for a further 2 hours. Prior to casting, the solution was left to stand, unstirred, for a few minutes in order to degas then casted into a glass mold and oven dried at 60° C. under a nitrogen gas purge for 72 hours. It was important to ensure that the moisture was carefully excluded during casting; otherwise this can result in low-quality cloudy films with inferior mechanical properties. The solvent cast film was then annealed under vacuum at 70° C. for 6 hours to ensure complete removal of any residual solvent. Same procedure was used to cast blank TPU for comparison with the nanocomposite.

[0104] Tensile properties of nanocomposite and blank TPU films were measured at room temperature using Instron model 5543 universal testing machine (Instron Pty Ltd., Melbourne, Australia) equipped with a 500 N load cell. Samples were cut into dumbbell shape according to ASTM d-638-M-3 and test was performed with a gauge length of 14 mm and crosshead speed of 50 mm/min. For each sample, five strips were tested. Modulus was determined from the slope of initial low strain meanwhile toughness by integrating the area under the curve.

[0105] A nanocomposite film was prepared from a clear and stable dispersion of strong and high aspect ratio spinifex CNC (CNC was obtained from acid hydrolysis using 40% (v/v) acid for 3 hours at 45° C.) in a medium hardness aliphatic thermoplastic polyurethane (TPU) using the solvent casting method. The nanocomposite was then tested under uniaxial extension at room temperature and the results of mechanical properties including ultimate tensile stress, tensile strain at break, Young's modulus and work at fracture (toughness) are presented in FIG. 3 and Table 2, with the neat TPU as a reference. In FIG. 3, the neat TPU is the lower curve and the CNC-containing nanocomposite elastomer is the upper curve. The neat TPU film possessed a typical high elongation at break of about 1268%, a high tensile strength of 61 MPa, and a Young's modulus of 7 MPa. The Young's modulus of this host TPU was increased from 7 MPa to 11.3 MPa by adding 1 wt % CNC due to some stiffening of the elastomer through reinforcement and load transfer by the cellulose crystals network, and the toughness was increased by about 20%. The increases in the modulus and toughness of the composite can be due that the CNC preferentially interacted with the more polar hard segments of the host polyurethane rather than the more hydrophobic soft segments, consequently avoiding the undesired stiffening of the soft microdomains and thereby retaining the large and desirable elongation of polyurethane nanocomposite.

TABLE-US-00003 TABLE 2 Mechanical properties of neat TPU and CNC-TPU nanocomposite Young's Tensile Work at Modulus Tensile strain stress fracture Sample (MPa) (m/m) (MPa) (MJ m.sup.-3) TPU    7 ± 0.95 1256 ± 30 59 ± 4.4 245 ± 23 TPU, 1 wt% 11.3 ± 0.3  1191 ± 23 67 ± 1.5 299 ± 19 CNC

[0106] Without wishing to be bound by theory, the present inventors have postulated that the nanocellulose used in the examples given above comprise CNCs and NFCs that have been formed by processing of material derived from arid Spinifex. It is possible that these nanocellulose materials have a relatively flexible and amorphous hemicellulose region surrounding the bundle of fibres or individual elementary cellulose nanofibrils and that this hemicellulose region provides an intermediate region between the cellulose fibres and the elastomer which, in turn, allows for flexing between the elastomer and the cellulose fibres. Here, the hemicellulose may be acting as a lubricant between the cellulose fibres and the elastomer molecules, allowing slippage between the two. Thus, although the nanocellulose reinforces the elastomer to result in production of a composite having increased strength, stiffness does not unduly increase. In addition to the high hemicellulose content that may be acting as a lubricant between the cellulose fibres and the elastomer molecules, the hemicellulose which may be present in between elementary cellulose nanofibrils in a nanocellulose fibre may act to render the cellulose fibre itself more flexible. This enhanced flexibility that may be present in nanocellulose with high hemicellulose content makes such nanocellulose materials more suitable than other nanofiller reinforcing agents for use in elastomers where flexibility and elasticity are desired to be retained. The composite material of the present invention may be used in a wide variety of potential uses, including condom manufacture, medical gloves, industrial seals, wear liners in mining applications, tyres, conveyor belts, and balloon manufacture. The material may also be used in other applications. By having increased strength and toughness without unduly increased stiffness, it may be possible to use thinner layers of the composite material to form products such as condoms without weakening the condoms and without increasing the risk of breakage rupture.

[0107] The nanocellulose used in the present invention may comprise nanocellulose made in accordance with the methods described in our international patent application number PCT/AU2014/050368, the entire contents of which are incorporated by cross-reference.

[0108] In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0109] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0110] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.