Search

In the present study we demonstrate how the sensitive property of the constituent parts of silkworm silk fiber can be applied to the field of soft composite materials. It concerns the structural and intrinsic functional characteristics of silk vs. the macroscopic property and the realization of functional composites. Silk fiber reinforced silicone rubber (SR) composites have been fabricated with different fiber lengths. The key structural features of silk made of stiff nanocrystals, including hydrogen bonded β-strands and β-sheet nanocrystals, when embedded in a softer matrix demonstrate that the tensile strength as well as the stiffness of the composites are higher than those measured for SR reinforced with synthetic polyether-ether-ketone fibers. Moreover, the intrinsic luminescence of protein nanocrystals permits the direct observation of the deformation with accurate measurement of the strain in the composite. Based on the intrinsic properties of such natural hierarchical material, these findings will allow to transfer the engineering of composite materials, particularly, soft functional composites, to a new applications ranging from strain measurements in biological tissue to monitoring tool in structural composites.

Parafilm is a soft, solvent-proof and self-sealant thermoplastic material obtained by blending paraffin wax and polyolefin and that displays irreversible elongational thinning as the material is stretched. In this paper a lamination process was used to transfer graphene nanoplatelets (GNPs) on self-adherent Parafilm substrate and we show that a high-strain state of such conductive Parafilm/GNPs film is reversible when the film is transferred by lamination to a fluoroelastomer (FKM) substrate. The stretching of GNP network stuck on viscoelastic Parafilm gave rise to regions of high and low GNP concentrations with increasing the electrical resistance upon stretching. Upon relaxation from a high-strain state, the composite film on FKM substrate maintain the initial electrical conductive state. Finally it was shown the reduction of the ethanol corrosion action in terms of swelling and mechanical performance of the neat FKM when the Parafilm/GNPs film is used for its packaging. In view of the low cost thermoplastic polymer used for the transferring and the lamination method proposed, these findings represent a facile and an industrial scalable approach to realize novel multifunctional elastomer composites., NMP is supported by the European Research Council (ERC PoC 2015 SILKENE nr. 693670) and by the European Commission H2020 under the Graphene Flagship (WP14 “Polymer composites”, n. 696656) and under the FET Proactive (“Neurofibres” no. 732344). Nanesa srl is acknowledged for supporting us with FESEM analysis.