A new strengthening process of thermoplastic polypropylene reinforced by interlayered activated sizing film-free carbon fiber treated by electron beam irradiation under oxygen-rich nitrogen gas prior to assembly and hot-press

Abstract

A new process of activating sizing film free (removed sizing) carbon fiber (SFF-CF) mats directly with electron beam irradiation (EBI) under oxygen-rich nitrogen gas prior to lamination assembly and hot-press was found to increase bending strength of CFRTP (CF reinforced thermoplastic polypropylene (PP)) interlayered composite composed of 3 SFF-CF mats between 4 PP sheets, [PP]4[SFF-CF]3. The hot-press fabrication was performed under 4.0 MPa at 473 K for 1 min. Experimental results showed optimal condition of 0.22 MGy-EBI under 2,000 ppm-O2-rich, protective N2 atmosphere improved bending strength, σb at all accumulative probabilities, Pf over that of untreated. This could be explained by maximum number of the strong covalent bonds of CF:C:C:PP and oxygen assisted CF:C:O:C:PP bonds adhering bare SFF-CF surface to PP, instead of the weak intermolecular bonding of CF(H2O, N2, O2)PP of untreated. The optimal concentration of O2 molecules together with the EBI probably purified the SFF-CF surface simultaneously generating dangling bonds, which already naturally exist in SFF-CF as evidenced by the highest intensity ESR peak whose inflection point was at B = 323 mT. This, along with attaching O groups to the SFF-CF surface can explain the increased SFF-CF to PP adhesion sites and bending strength increase. Fracture analysis showed the optimum condition prevented ply delamination and reduced damage area along sample length appearing to increase cohesion between the difficult to adhere thermoplastic PP and SFF-CF plies to take on higher loads. Although bending strength was increased, carefulness is always highly recommended when investigating unsized CF composites.

Interfacial Engineering Methods in Thermoplastic Composites: An Overview

“…CF was electron beam irradiated under oxygen-rich nitrogen gas before hot pressing with PP sheets to form CF-reinforced PP composites [ 120 ]. The electron beam irradiation created strong covalent bonds between the carbon atoms present in CF and PP matrix.…”

Significant enhancement of mechanical properties for glass fiber fabric‐reinforced polyamide 6 composites by improving interfacial bonding

“…[11][12][13][14] Therefore, various modification techniques were adopted to enhance the interfacial bonding between the polymer matrix and fibers. These technologies include chemical modification methods such as coupling and grafting, [15][16][17][18][19] surface irradiation methods, [20][21][22][23][24] incorporation of nanomaterials, [25][26][27][28][29] and plasma treatment. [30][31][32][33][34][35] Lee 15 treated glass fiber fabric (GFF) with γ-methacryloxypropyltrimethoxysilane (γ-MPS) to fabricate GFF-reinforced unsaturated polyester composites.…”

“…The modified composite exhibited a remarkable 90% increase in flexural strength and an 80% increase in flexural modulus compared to the unmodified composite. Kitagawa 23 irradiated carbon fiber fabric (CFF) with an electron beam and subsequently hot‐pressed it with polypropylene (PP) sheets to produce CFF‐reinforced PP composites. The electron beam irradiation facilitated the formation of covalent bonds between the carbon fiber and PP, resulting in a notable 26% enhancement in flexural strength compared to the untreated composite.…”