Phenolic-based metamaterials and methods of forming phenolic-based metamaterials

A method according to any preceding claim, wherein the viscosity controlling agent is a liquid, preferably selected from one or more of butanol, chloroform, ethanol, water, acetonitrile, hexane and isopropyl alcohol.

A method according to any one of the preceding claims, wherein the phenolic resin is a phenolic resole resin, preferably a phenolic resole resin that includes less than 10% by weight of free formaldehyde, preferably less than 1% by weight, more preferably less than 0.5% by weight, for example less than 0.1% by weight.

A method according to any one of the preceding claims, wherein the metal hydroxide comprises particles having a particle size distribution with a D90 from 50 to 70 μm, and/or a D50 from 15 to 35 μm, and/or a D10 from 1 to 10 μm.

A method according to any one of the preceding claims, wherein the metal of the metal hydroxide is one or more of scandium, vanadium, chromium, manganese, iron, cobalt and aluminium.

A method according to any one of the preceding claims, wherein the metal hydroxide is of the formula M(OH)3, wherein M is a metal.

A method according to any one of the preceding claims, wherein the metal hydroxide is aluminium hydroxide.

A method according to any one of the preceding claims, wherein the step of heating the phenolic resin mixture at a temperature of greater than 200° C. is conducted in the substantial absence of oxygen.

A method according to any one of the preceding claims, wherein the heating is at a temperature of around 300° C. or greater, preferably around 400° C. or greater, more preferably 500° C. or greater, for example 600° C. or greater.

A method according to any one of the preceding claims, wherein the phenolic resin mixture is heated for at least about one minute, preferably at least about 5 minutes, more preferably at least about 10 minutes, for example at least about 15 minutes.

A method according to any one of the preceding claims, further comprising applying the phenolic resin mixture to a substrate prior to heating the mixture at a temperature of greater than 200° C. to form a composite material.

A method according to any one of the preceding claims, further comprising adding fibres to the phenolic resin mixture.

A method according to any one of the preceding claims, wherein the phenolic resin mixture has a viscosity of from 200 to 10,000 mPa·s at 20° C.

A method according to any one of the preceding claims, wherein the phenolic resin mixture is caused or allowed to at least partially set prior to heating the mixture at a temperature of greater than 200° C.

A method according to any one of the preceding claims, wherein the phenolic resin mixture is moulded or shaped prior to the step of heating the phenolic resin mixture to form the phenolic metamaterial.

rial according to claim 37 and bonding the material to a substrate.

A method for making a composite material comprising providing a phenolic

Use of a transition metal hydroxide and/or aluminium hydroxide to increase the hardness of a cured or uncured phenolic resin material, wherein the phenolic resin material comprising a transition metal hydroxide and/or aluminium hydroxide is heated to a temperature of greater than 200° C.