Micromechanics of Mechanical, Thermomechanical, and Chemi-Thermomechanical Pulp from Orange Tree Pruning as Polypropylene Reinforcement: A Comparative Study

Abstract

This work explores the use of mechanical (MP), thermomechanical (TMP), and chemi-thermomechanical (CTMP) pulps from orange tree pruning fibers (OPF) as reinforcing elements of polypropylene (PP) composites. Due to the nature of the natural fibers, the use of a coupling agent is needed to attain a good interface and to prevent fiber slippage from the matrix. The main objective of the present work was to investigate the orientation factor, the interfacial shear strength, and the intrinsic strength of the OPF. Coupled and non-coupled composites were formulated and tested, optimizing the coupling agent content with the objective of maximizing the tensile strength of the composites. Hirsch and Kelly-Tyson models and the Bowyer-Bader methodology were used to compute the micromechanic properties. The contribution of subcritical, supercritical fibers, and matrix were also calculated.

Tensile Properties of Polypropylene Composites Reinforced with Mechanical, Thermomechanical, and Chemi-Thermomechanical Pulps from Orange Pruning

“…Consequently, the use of waste from agriculture seems favorable. Specifically, the use of citrus pruning ensures an annually renewable source of materials, as the amount produced in Spain represents 1.15 x 10 9 kg/year (Reixach et al 2013b). Additionally, and from a strategic point of view, extending the value chain of the agroforestry industries by the valorization of co-and by-products would enhance the profitability of these industries (Mishra and Sain 2009).…”

Starch-Based Biopolymer Reinforced with High Yield Fibers from Sugarcane Bagasse as a Technical and Environmentally Friendly Alternative to High Density Polyethylene

“…The 6% coupling agent (MAPE) by weight of HDPE was added to the mixer with the HDPE pellets. The MAPE percentage was chosen based on the available literature and experience of the research group (Reixach et al 2013).…”

“…The mean length of the resulting fibers for MP, TMP, and CTMP were observed to have increased with the aggressiveness of the treatments. The reason for this could be due to the initial extraction of lignin and extractives from the fiber's surface, based on thermal processes in the case of the TMP, and chemical and thermal processes in the case of the CTMP (Reixach et al 2013). As lignin is one of the main adhesives in the fiber bundles, this initial extraction resulted in an easier final mechanical individualization.…”

“…However, the MP, TMP, and CTMP were expected to noticeably increase tensile strengths. The aforementioned statement is only true when the other parameters affecting the tensile strength of a composite, particularly a good interphase, are guaranteed (Reixach et al 2013(Reixach et al , 2015.…”

“…This value is within the range (6.22 to 7.18) defined by the Tresca (t m /2) and the Von Mises criteria (t m /3 1/2 ), respectively. The Von Mises value defines an upper bound for the shear forces that an interphase is able to transmit from the matrix to the fiber, and it is difficult to reach higher values (Reixach et al 2013;Serrano et al 2013). Consequently, the obtained value can be considered to have belonged to a good quality interphase.…”