Extrinsic toughening of recycled carbon fibers in polypropylene composites in the absence of plasticity penalty

Abstract

Advanced composite materials used in high-tech fields are widely reinforced with carbon fibers. One of the growing application areas for carbon fibers is their reinforced composites which are used to replace metallic automotive parts. This reduces carbon footprint through weight reduction, which is a strategy pursued globally to reduce the environmental impacts of passenger vehicles. In this study, we assess the reinforcement potential of recycled carbon fibers in a polypropylene (PP) homopolymer with high strength and flowability. The highly crystalline PP homopolymer with low impact properties was used to minimize intrinsic plasticity penalty associated with fiber reinforcement and ascribe the impact strength enhancement solely to extrinsic toughening mechanisms. The reinforced composites are manufactured through extrusion compounding followed by injection molding. Modification of the transition phase connecting the bulk matrix with the bulk carbon fibers led to 78% enhancement in the strength of the composites, compared to the unmodified composites, without any loss in other properties. Compared to a commercial steel bonnet, the compatibilized composites reinforced with recycled carbon fibers exhibited superior specific strength accompanied by ∼87% weight reduction. Morphological analysis showed that all the extrinsic toughening mechanisms are effectively used by the recycled fibers in the reinforced composites.

Development and characterization of a recycled nylon fiber reinforced and nano-fly ash hybridized high impact performance polypropylene composite for sustainability

“…There was a very insignificant increase in the melting point of the composites due to the addition of reinforcements. A similae extent of increase (maximum ∼3°C) in T m has been reported earlier by Karsli et al, 64 and Ghanbari et al 48 for carbon fiber reinforced PP composites. Likewise, maxima trough from cooling cycle of the composites demonstrates crystallization temperatures of the composites.…”

“…In the equation (1) X c , ΔH, and ΔH* represent the crystallinity, melting enthalpy of the samples, and melting enthalpy of the 100% crystalline PP. ΔH* for the 100% crystalline PP and NF is taken as 207 [47][48][49] and 190 J/g. 50 Also, dynamic mechanical thermal analysis was used to study the glass transition temperature of all the samples using ASTM D5576-00.…”

Mechanical Recycling of Carbon Fiber-Reinforced Polymer in a Circular Economy

“…For example, both acids and silane compounds used in alignment of CFs, widely used as coupling agents in CF-reinforced composites, form chemical bridges between the CF surface and the polymer matrix. These processes enhance adhesion, promote load transfer between the two components, and allow them to form a strong covalent bond [89][90][91][92]. For instance, Lee et al [90] explored the impact of silane coupling agents' chemical properties on the interfacial bonding strength between thermoplastic polymers (i.e., polyamide 6) and recycled CFs.…”

Transformation of waste carbon fiber prepreg into sustainable composites: Application in the automotive industry components

“…A standard MFI suggestion for polypropylene with chopped carbon fibers is 10-30 MFI. [55][56][57] However, this might vary based on the fiber content, fiber length, and desired end product qualities. The amount of chopped carbon fibers in the mixture affects the material's viscosity.…”