Method for preparing graphene-modified natural rubber with an interfacial interaction based on a free radical annihilation reaction

A method for preparing a graphene-modified natural rubber (NR) with an interfacial interaction based on a free radical annihilation reaction, comprising:

• (1) dissolving a free radical scavenger in water to obtain a solution;
• and adding a graphene oxide aqueous dispersion with a preset concentration to the solution followed by reaction to obtain a free radical scavenger-loaded reduced graphene oxide (rGO) aqueous dispersion;
• (2) adding deionized water to a natural rubber latex to obtain a latex emulsion, and mixing the free radical scavenger-loaded rGO aqueous dispersion with the latex emulsion under stirring to obtain a mixed emulsion, wherein rGO particles loaded with the free radical scavenger are bonded with rubber particles in the mixed emulsion to form bound particles under an action of an electrostatic attraction between rGO particles and negative ions from a protein-phospholipid membrane on a surface of the rubber particles;
• adding a flocculant to the mixed emulsion to obtain a crude rubber, wherein flocculation occurs due to a reduction of repulsion between negative charges of the rubber particles in the mixed emulsion that keeps the mixed emulsion stable, and the rubber particles in the mixed emulsion whose protection layers are damaged and the rGO particles further undergo mutual adsorption by means of T-x interaction, such that the bound particles and the rubber particles in the mixed emulsion are orderly aggregated and co-precipitated from an aqueous phase to obtain the crude rubber;
• and
• subjecting the crude rubber to water washing and drying to obtain a free radical scavenger-loaded rGO-modified NR masterbatch;
• and
• (3) sequentially adding a rubber additive and a reinforcing filler to the free radical scavenger-loaded rGO-modified NR masterbatch during an mixing process in an internal mixer to obtain a rubber mixture;
• and cooling the rubber mixture to room temperature, and subjecting the rubber mixture to a milling process in an open two-roll mill, mixing with a vulcanizing agent and mill run until there are no bubbles in the rubber mixture;
• and allowing the rubber mixture to stand for a period of time, and placing the rubber mixture in a mold followed by vulcanization to obtain the graphene-modified NR composite;
• wherein the free radical scavenger loaded on the rGO particles are capable of annihilating macromolecular free radicals generated by NR macromolecules due to an action of heat and/or force during mixing and milling processes, an enhancement effect of the free radical annihilation reaction on an interfacial interaction between graphene and NR is obtained, thereby increasing a bound rubber content of natural rubber, increasing a crosslinking density of graphene-modified NR composite, and improving a crosslinking network of graphene-modified NR composite.