Miscanthus stem fragment – Reinforced polypropylene composites: Development of an optimized preparation procedure at small scale and its validation for differentiating genotypes

Abstract

International audienceThe production of ligno-cellulosic biomass-based composites requires the development of new methodologies to evaluate the reinforcement potential of a given biomass, such as miscanthus studied in the work. Miscanthus stems from thirteen genotypes were broken into elongated fragments and mixed with polypropylene composites in an internal mixer. The aim is to find the best protocol able to discriminate miscanthus genotypes for their reinforcement capability. The following process parameters were optimized in order to maximize the reinforcement effect of the stem fragment filler: mixing parameters (mixing time, rotor speed and chamber temperature), temperature, fragment content, size and length distributions and coupling agent. The relationship between the process parameters and the mechanical properties of composites were analyzed to evaluate the influence of genotype on reinforcement performance, showing the robustness of the protocol in effectively discriminating genotypes according to their reinforcing capacity

Increase of Miscanthus Cultivation with New Roles in Materials Production—A Review

“…The biomass particle parameters of size, alignment, and dispersion in the matrix determine the degree of mechanical reinforcement that is possible [50,52,74,76]. A strong influence of fine particles via the reduction of mechanical properties and the necessity of the removal of irregular dust was reported by Girones et al [50]. A homogeneous dispersion of fibers is required as reinforcement effects are anisotropic and the misalignment of fibers can lead to a weaker specimen [51].…”

“…The feedstock parameters can be divided into three main fields: the macroscopic scale, the microscopic scale, and the molecular scale. The macroscopic scale consists of demands to the transport qualities, including the bulk density [39,48], or the culm and chip size [22], moisture content [4,35,48,49], and the aspect ratio [50][51][52] of the biomass. Onthe microscopic scale, the surface properties, in terms of roughness [50,53,54], pore sizes [54,55], surface chemistry [22,52,56], and fibrillation of particles [57], could be relevant.…”

“…Difficulties in the reinforcement mechanisms are caused by the fiber to matrix compatibility [52], the dispersion of the fibers within the matrix [52], and possible degradation of the fiber during the processing [35,49,74]. The fiber to matrix bond may be strongly influenced by hydrophilic particles and hydrophobic polymers, leading to insufficient adhesion [50,52,56,73]. Matrix compatibilizers can be used to improve the interface adhesion by blending the polymer with a co-polymer, such as maleic anhydride [50,52,75], grafted polypropylene, or by reactive activation with a peroxide [76].…”

“…The fiber to matrix bond may be strongly influenced by hydrophilic particles and hydrophobic polymers, leading to insufficient adhesion [50,52,56,73]. Matrix compatibilizers can be used to improve the interface adhesion by blending the polymer with a co-polymer, such as maleic anhydride [50,52,75], grafted polypropylene, or by reactive activation with a peroxide [76]. However, the necessity for compatibilization is dependent on the specific polymer system as a good interfacial bond was reported in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) [56,77].…”

“…A homogeneous dispersion of fibers is required as reinforcement effects are anisotropic and the misalignment of fibers can lead to a weaker specimen [51]. Smaller fibers with a high length to width aspect ratio are related to tensile strength increases, due to the higher specific surface area [50].…”