Dry ball milling of graphite under carbon dioxide pressure affords multilayer-functionalized graphene (MFG) with carboxylic groups as nanofiller for composites of carbon and acrylonitrile–butadiene–styrene copolymers (ABSs). Produced in a single-step process without requiring purification, MFG nanoplatelets are uniformly dispersed in ABS even in the absence of compatibilizers. As compared to few-layer graphene oxide, much larger amounts of MFG are tolerated in ABS melt processing. Unparalleled by other carbon nanofillers and non-functionalized micronized graphite, the addition of 15 wt % MFG simultaneously results in a Young’s modulus of 2550 MPa (+68%), a thermal conductivity of 0.321 W∙m−1∙K−1 (+200%), and a heat distortion temperature of 99 °C (+9%) with respect to neat ABS, without encountering massive embrittlement and melt-viscosity build-up typical of few-layer graphene oxide. With carbon filler at 5 wt %, the Young’s modulus increases with increasing aspect ratio of the carbon filler and is superior to spherical hydroxyl-functionalized MFG, which forms large agglomerates. Both MFG and micronized graphite hold promise for designing carbon/ABS compounds with improved thermal management in lightweight engineering applications.

Graphite exfoliation by shear‐induced dry and wet processes and especially mechanochemistry represent attractive routes to carbon nanofillers. Dry ball‐milling of graphite in a planetary mill under gas pressure is a scalable and environmentally benign one‐step process, which requires neither hazardous solvents nor tedious separate functionalization and purification steps. Gas type, pressure, and milling duration govern average particle size, shape, and functionalization. Ball‐milling under Ar yields hydroxylated spherical carbon particle agglomerates, whereas ball‐milling under CO2 affords functionalized nanoplatelets without encountering agglomeration problems and highly exothermic post‐milling reactions with air. The carboxylation of graphene nanoplatelets enhances their dispersibility in various media including polypropylene (PP) even in the absence of compatibilizers. Large amounts of carboxylated nanoplatelets are dispersed in PP without massive viscosity build‐up. Functionalized carbon nanoplatelet fillers enable tailoring of recyclable lightweight carbon/hydrocarbon composites exhibiting an improved balance of stiffness, strength, toughness, electrical, and thermal conductivity.

The two-stage mechanochemical amination of graphite by dry ball milling of graphite in a planetary ball mill under Ar followed by NH 3 yields aminated multilayer graphene (AMFG) as intermediates for carbon/polymer hybrids and nanocomposites. Opposite to efficient edge-selective graphene functionalization under Ar, CO 2 and N 2 pressure, the onestage ball milling under NH 3 pressure affords rather low N content (<0.5 wt%) and fails to reduce the graphite platelet size. According to DFT (Density Functional Theory) calculations NH 3 exhibits low mobility between graphene layers and forms weak bonds to carbon which impair breakage of carbon bonds. In the two-stage ball-milling of graphite under Ar affords reactive carbon nanoparticles which react with NH 3 in the second stage. With increasing milling duration of the second stage the nitrogen content increases to 3.2 wt%. As verified by XPS (X-ray photoelectron spectroscopy) measurements primary amine groups are formed which couple with various dicarboxylic anhydride groups including maleated PP to produce imidefunctionalized graphene. This is of interest to produce compatibilizers and dispersing agents for carbon/PP nanocomposites exhibiting improved mechanical properties. Two-stage mechanochemistry holds promise for carbon nanoparticle functionalization well beyond amination.

Dry ball milling of graphite under CO2 pressure in a planetary ball mill affords carboxylated multilayer graphene nanoplatelets as carbon nanofillers (MFG‐CO2) for carbon/epoxy spray coatings combining electrical conductivity up to 0.09 S cm−1 with excellent adhesion and improved toughness. As confirmed by µCT‐imaging, the two‐stage homogenization by means of a speed mixer with subsequent shearing in a three‐roll mill uniformly disperses up to 60 wt% MFG‐CO2 in aqueous emulsions of epoxy resins and hardener without impairing spray coating. The MFG‐CO2 content governs surface roughness, as determined by 3D laser microscopy, gloss, electrical conductivity, and toughness without adversely affecting excellent adhesion. Mechanochemical tailoring MFG nanofillers holds great promise for the development of advanced epoxy spray coatings exhibiting an improved balance of thermooxidative, chemical and environmental stability, electrical and thermal conductivity, toughness, corrosion, and barrier resistance.