Polystyrene-grafted Carbon Fibers: Surface Properties and Adhesion to Polystyrene

Abstract

It is highly desirable to improve attractive interactions between carbon fibers and unreactive thermoplastic matrices to the possible maximum. This could be achieved by a simple grafting process to create a covalently bonded interface or interlayer, which should result in cohesive interactions between the polymer-grafted fibers and the same matrix material, leading to a better adhesion strength in the obtained composite material. Here, we are describing the grafting of styrene onto unmodified and unsized carbon fibers via free-radical bulk polymerization in the presence of fibers. After grafting, the surface properties of the carbon fiber *Author to whom correspondence should be addressed. E-mail: a.bismarck@imperial.ac.uk approach those of pure polystyrene which was proven by contact angle and zeta (-) potential measurements. As indicated by the water contact angle, the carbon fiber surface becomes more hydrophobic. Scanning electron microscopy (SEM) provides evidence of grafted polymer. This simple procedure results in a continuous polystyrene coating. The fiber diameter increases significantly after polymer grafting. The adhesion and fracture behavior between the original and polystyrene-grafted carbon fibers to a polystyrene (VESTYRON Õ ) matrix was characterized using the single-fiber pull-out test. There is a considerable increase in the measurable adhesion, i.e., the interfacial shear strength IFSS , by almost 300% between the grafted fibers and polystyrene as compared to untreated original fibers. Two planes of interfacial failure could be distinguished; first in the fiber coating interface leading to lower interfacial shear strength and second in the PS-matrix-PS-coating interphase resulting in a higher interfacial shear strength. In addition to the improved adhesion, there are also clear differences in the pull-out behavior between the nongrafted and grafted fibers. After the initial debonding process corresponding to the maximal pull-out force is completed, the pull-out force is increasing again.

Recent advances in fiber/matrix interphase engineering for polymer composites

“…Note that this value is still at about the half that was measured for PP-sized GF in a PP matrix containing maleic anhydride grafted PP (PP-g-MA) that might be considered as the state-of-the-art coupling agent [82]. Bismarck et al [83] grafted polystyrene (PS) via bulk radical polymerization of styrene to CF surface. The contact angle and zeta-potential measurements confirmed that the surface of the grafted CF was PS-like.…”

Continuous Atmospheric Plasma Oxidation of Carbon Fibres: Influence on the Fibre Surface and Bulk Properties and Adhesion to Polyamide 12

“…However, due to the un-reactive nature of thermoplastic polymers and the nature of commercially applied carbon fibre surface treatments, the adhesion between commercial fibres and thermoplastic matrices is usually low [21]. Therefore, additional modification techniques have been introduced in order to optimise the fibre/thermoplastic adhesion, which includes electro-coating [22] and polymer grafting [23,24]. The problem with these methods is that they require potentially harmful chemicals.…”

Polyamide‐12/Functionalized Carbon Nanofiber Composites: Evaluation of Thermal and Mechanical Properties

“…CNFs have been successfully compounded with different thermoplastic14, 16, 18–31 and thermoset32, 33 matrices using conventional polymer processing technology such as high‐shear mixing or extrusion, demonstrating the feasibility of such methods for effective dispersion and orientation of the nanofibers. Unfortunately, the mechanical performance of these composites have been limited by the lack of an adequate interface strength, which results in poor interlaminar adherence and fiber pull‐out 15, 34…”