We report the utilization of a melt-stable lignin waste-stream from biorefineries as a renewable feedstock, with acrylonitrile-butadiene rubber and acrylonitrile-butadiene-styrene (ABS) polymer to synthesize a renewable matrix having excellent 3D-printability.
While the initial low melt viscosity of the dispersed lignin phase induces local thermo-rheological relaxation facilitating the composite’s melt flow, thermal crosslinking in both lignin and rubber phases as well as at the lignin-rubber interface decreases the molecular mobility. Consequently, interfacial diffusion and the resulting adhesion between deposited layers is decreased.
However, addition of 10 wt.% of discontinuous carbon fibers (CFs) within the green composites not only significantly enhances the material performance but also lowers the degree of chemical crosslinking formed in the matrix during melt-phase synthesis.
Furthermore, abundant functional groups including hydroxyl (from lignin) and nitrile (from rubber and ABS) allow combinations of hydrogen-bonded structures where CFs play a critical bridging role between the deposited layers.
As a result, a highly interfused printed structure with 100% improved inter-layer adhesion strength was obtained. This research offers a route toward utilizing lignin for replacement of petroleum-based thermoplastics used in additive manufacturing and methods to enhance printability of the materials with exceptional mechanical performance.
Read more: 3D-printability and adhesion in lignin-based composites
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