Interphase Engineering of a Cellulose‐Based Carbon Fiber Reinforced Composite by Applying Click Chemistry

Abstract

Given our possible future dependence on carbon fiber reinforced composites, the introduction of a renewable matrix might be advantageous for the vision of a sustainable world. Cellulose is a superior green candidate and provides exceptional freedom in composite design as the free OH groups can be conveniently functionalized to give tailor‐made materials. To obtain a high‐performing carbon fiber reinforced cellulose propionate composite, we accurately tailored the interfacial adhesion by invoking click chemistry. The synthetic strategy involved grafting of a phenylacetylene structure onto the carbon fiber surface, onto which O‐acylated 6‐azido‐6‐deoxycellulose and a number of aromatic azides could be covalently attached. Single‐fiber fragmentation tests indicated that the lipophilicity and size of the substituent on the deposited structure played a crucial role in determining molecular entanglement and mechanical interlocking effects, as penetration into the cellulose propionate matrix was of utmost importance. Enhanced interfacial shear strength was obtained for the carbon fiber covalently functionalized with the cellulose derivative. Nevertheless, the greatest increase was observed for the derivative substituted with a compact and highly lipophilic CF3 substituent. In a broader sense, our study provides a synthetic platform to bind cellulose derivatives to graphitic surfaces and paves the ways towards the preparation of innovative cellulose‐based carbonaceous materials.

Lignin as a Functional Green Coating on Carbon Fiber Surface to Improve Interfacial Adhesion in Carbon Fiber Reinforced Polymers

“…Dumbbell specimens for the fragmentation test were prepared using injection molding technique according to our previous studies [7,8]. As a green thermoplastic matrix, cellulose propionate was chosen for these experiments due to its superior properties among cellulose-based matrices available on the market (high molecular weight, good processability [7,8]). Epoxy resin was not used for the fragmentation test (difficulties in preparing single fiber composite for the test), but it was involved in the microdroplet experiment.…”

“…Cellulose propionate ( M w ≈ 200,000 g mol −1 according to the manufacturer) was supplied by Scientific Polymer Products, Inc. (Ontario, NY, USA), the degree of substitution was determined to be 2.76 in our previous publication (92% of hydroxyl groups are substituted) [7,8]. The matrix has a tensile strength of ~80 MPa and a glass transition temperature ( T g ) of ~132 °C (Shimadzu DSC-60A Plus, Kyoto, Japan).…”

“…Carbon fiber T700SC-12000-50C (~7 μm fiber diameter; ~4.9 GPa tensile strength) was purchased from Toray Industries (Tokyo, Japan). The fibers have nominally ~1% sizing agent on the surface, therefore, in order to access the graphitic surface for the grafting reactions, a cleaning procedure was applied [7,8], the removal of the commercial coating was evidenced in our previous report [7].…”

“…Fragmentation test was conducted according to our previous studies using cellulose propionate as polymer matrix [7,8]. A hydraulic hot-press machine (Type MH-10, Imoto Machinery Co., Kyoto, Japan) was used to prepare polymer films and single fiber composites (10 specimens from each type of carbon fibers).…”

“…On the other hand, special emphasis has been placed on changing the thermoset matrix (dominating the CFRPs market with ~70% contribution [4]) to environmentally more benign thermoplastic polymers [6]. Furthermore, cellulose-based carbon fiber reinforced polymers are also gaining attention [7,8], and advances in this field open the gates for the preparation of fully biomass-derived CFRPs.…”