Short Carbon Fiber Reinforced Polymers: Utilizing Lignin to Engineer Potentially Sustainable Resource-Based Biocomposites

Abstract

Carbon fiber reinforced composites have exceptional potential to play a key role in the materials world of our future. However, their success undoubtedly depends on the extent they can contribute to advance a global sustainability objective. Utilizing polymers in these composites that can be potentially derived from biomasses would be certainly vital for next-generation manufacturing practices. Nevertheless, deep understanding and tailoring fiber-matrix interactions are crucial issues in order to design carbon fiber reinforced sustainable resource-based biocomposites. In this study, cellulose derivatives (cellulose propionate and cellulose acetate butyrate) are utilized as model polymer matrices that can be potentially fabricated from biomasses, and the mechanical properties of the prepared short carbon fiber reinforced composites are engineered by means of a functional biobased lignin coating on the fiber surface. Furthermore, polyamide 6 based composites are also prepared, the monomer of this polymer could be obtained using C6 sugars derived from lignocellulosic biomasses in the future (through 5-hydroxymethylfurfural). Lignin was successfully immobilized on the carbon fiber surface via an industrially scalable benign epoxidation reaction. The surface modification had a beneficial impact on the mechanical properties of cellulose propionate and polyamide 6 composites. Furthermore, our results also revealed that cellulose-based matrices are highly sensitive to the presence of rigid fiber segments that restrict polymer chain movements and facilitate stress development. It follows that the physicochemical properties of the cellulosic matrices (molecular weight, crystallinity), associated with polymer chain mobility, might need to be carefully considered when designing these composites. At the same time, polyamide 6 showed excellent ability to accommodate short carbon fibers without leading to a largely brittle material, in this case, a maximum tensile strength of ~136 MPa was obtained at 20 wt% fiber loading. These results were further contrasted with that of a petroleum-based polypropylene matrix exhibiting inferior mechanical properties. Our study clearly indicates that carbon fiber reinforced polymers derived and designed using biomass-derived resources can be promising green materials for a sustainable future.

Mussel-Inspired Design of a Carbon Fiber–Cellulosic Polymer Interface toward Engineered Biobased Carbon Fiber-Reinforced Composites

“…It follows that again fiber volume fraction (which determines the number of fiber ends given that the size of the fibers is relatively similar) influences mostly this parameter. 45 , 55 , 57 , 58 Similar results were found in our previous study. 45 The parameters influencing the tensile strength of a short CF-reinforced composite are usually discussed using the modified rule of mixture theory according to eq 1 ( 45 , 59 ) where σ cu , σ l , and σ m are the tensile strength of the composite, fiber, and resin, whereas V f and V m denotes the volume fraction of the fiber and matrix, respectively.…”

“…The rigid fiber segments facilitate microcrack formation and confine polymer chain mobility, which is the underlying reason for the brittleness. 45 , 57 The strain at break value is tightly connected to the number of fiber ends as stress accumulates at these locations, serving as nucleation sites for microcracks. It follows that again fiber volume fraction (which determines the number of fiber ends given that the size of the fibers is relatively similar) influences mostly this parameter.…”

“… 42 , 63 As a model cellulosic resin, cellulose propionate ( M w ≈ 200,000 g mol –1 according to the producer; Scientific Polymer Products, Inc., Ontario, NY, USA; catalogue number 321), a thermoplastic cellulose ester was chosen exhibiting excellent processability and mechanical characteristics in our previous studies. 45 The degree of substitution was determined to be 2.76 elsewhere. 42 A carbon disk (99.98% purity; 1 mm thick, 50 mm diameter) for the contact angle measurements was ordered from The Nilaco Corporation (Tokyo, Japan).…”

“…A rotation speed of 60 rpm (co-rotating twin-screw), 203 °C processing temperature, and 5 min retention time was applied according to our previous reports. 45 Flow characteristics of CP can be found elsewhere. 45 Standard dumbbell-shaped specimens (JIS K 7161-2:2014 1BA) were made using an Imoto IMC-5705 injection molding machine (Imoto Machinery Co., Ltd., Kyoto, Japan).…”

“… 45 Flow characteristics of CP can be found elsewhere. 45 Standard dumbbell-shaped specimens (JIS K 7161-2:2014 1BA) were made using an Imoto IMC-5705 injection molding machine (Imoto Machinery Co., Ltd., Kyoto, Japan). The following conditions were applied: barrel temperature: 210 °C; mold temperature: 140 °C; and injection pressure: 0.6 MPa.…”