**1. Introduction**

Since several decades ago, biocomposites have emerged as an option aimed to solve several issues within the composite materials science. In most of published cases in the literature, the use of natural fibers in combination with polymers is carried out to achieve some degree of reinforcement from the fibers to the polymer. Many studies report the use of natural fibers such as flax, hemp, jute, sisal, coconut fiber, banana, and fique, among many others [1], using

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

an extensive variety of polymer matrices like polyethylene [2, 3], polypropylene [4], polystyrene [5], polyester resins [6], and natural rubber [7]. Clear effects have been seen in the improvement of mechanical performance. For example, usually Young's modulus and tensile and flexural strength increase when natural fibers are compounded in percentages from 10 to 40%, which make the composites stiffer than its matrix counterpart [8]. Also, improvement in impact strength has been observed [9]. These findings give to the natural fibers a real opportunity to replace to some extent the use of fiberglass, aramid, and other synthetic fibers usually used for polymer reinforcement since, on top of their reinforcement ability, natural fibers are also cheap and have a much lower density than fiberglass, as previously stated in literatures [10–12]. However, the interest in utilization of natural fibers in biocomposites goes beyond their advantages for formulating new and mechanically improved materials. Interest is also driven by a global concern about the impact of plastics in the environment and a growing consciousness of the need for establishing a circular economy where residues like biomass and lignocellulosic can be valued and used as new raw material for industrial processes [13, 14]. In that regard it makes sense to use the agroforestry residues of extensive crops in a way that results in a neutral CO2 process, like the fabrication of composites, instead of using them for energy production through combustion. An example of the potential of lignocellulosic materials is the region of Valle del Cauca in the South West of Colombia, which has a large influence of the sugarcane industry. It produces 80% of all Colombian sugar, and also it counts for 50% of all local agricultural production. This industry produces a lot of agroforestry residues, approximately 6 million tons of sugarcane bagasse a year [15]. The availability and low cost of this residue are thought as competitive advantages for the development of sustainable biocomposites in this region. That is the main reason behind of our resent research: the valorization of sugarcane residues by their use in natural fiber reinforced polymer composites (NFPC). In regard to the use of sugarcane bagasse, some studies have reported its use as reinforcement for polypropylene, polyester, recycled PET, PVC, HIPS, and HDPE and as agents and/or compatibilizing treatments such as aluminates and mercerization (NaOH treatment) and the use of ethylene and methyl acrylate as copolymers and benzyl chloride [16–19]. However, to the best of our knowledge, there have been no reports of the use of silanes as compatibilizing agents in sugarcane bagasse microfibers, in order to improve their adhesion to polymer matrices. In this chapter, polypropylene bagasse (PP bagasse) biocomposites prepared through extrusion, injection, and thermocompression molding will be evaluated. The morphology as well as the mechanical, thermal, and thermomechanical properties of the biocomposites will be investigated with the aim to understand the effect of the chemical treatments of the bagasse fibers on the polypropylene (PP) matrix properties.

**2.2. Preparation and characterization of sugarcane bagasse microfibers**

a solution of 2 × 10−<sup>3</sup>

2 mL of HF (48–50%) and 98 mL of H<sup>2</sup>

**2.3. Preparation of the biocomposites**

performed using a nitrous oxide/acetylene flame.

Sugarcane as received was cleaned with distilled water in order to take off soil and residues from the lignocellulosic material. Clean bagasse was later dried at 60°C for 6 h until constant weight. Around 500 g of bagasse was then grounded using a Kinematica™ Polymix™ PX-MFC 90 D Lab mill drive and a sieve size of 200 μm. The sample was divided in three groups: one used as it was obtained after milling with no further treatment. A second group was treated with an aqueous solution of 8% NaOH using a 1:1 bagasse/solution ratio during 2 h, in order to remove lignin from the bagasse's surface. A third group of fibers were silanized after lignin removal. For silanization,

prepared. The pH of solution was kept at 3 using acetic acid. A time of 10 minutes was allowed for hydrolysis after addition of silane and before the solution was sprayed over bagasse fibers using a plastic spray bottle. Wet fibers were allowed to dry at 90°C for 24 h in a forced air oven. After drying, fibers were kept in plastic bags until used in the composition process with polypropylene. Each group of fibers was characterized by thermal gravimetric analysis (TGA) using a nonreactive atmosphere (N2 at 50 mL/min) from 25 to 650°C at a heating rate of 10°C/min using a TGA/DSC 2 STAR system, from Mettler Toledo. Surface structure of fibers was characterized by scanning electron microscopy (SEM), and chemical maps are also obtained by electron dispersed spectroscopy (EDS) using an ultra-high-resolution analytical FE-SEM SU-70 from Hitachi. All samples were sputtered with gold before analysis. Silicon content on fibers was quantified by flame atomic absorption spectrometry (FAAS). Around 0.5 g of fibers was calcinated at 550°C for 4 h in porcelain crucibles. After calcination each sample was treated with

containers for 24 h and then filtered. Quantification using Analist 800 from Perkin Elmer was

Biocomposites were compounded in a counter-rotating twin screw extruder Thermo Scientific HAAKE™ Polylab. In all cases fibers were physically premixed with polypropylene pellets in a plastic bag using 20% of fiber in weight. About 500 g of fiber-polypropylene mix was introduced in the extruder at 70 rpm. A temperature gradient from 140 to 170°C from the feeder to the melting zone was used. The outcoming cord of composite from the extruder was

After the pelletization process, the PP and PP-bagasse biocomposite samples were dried in an oven at 85°C followed by injection molding process at 180°C. A BOY XS (BOY Machines, Inc., USA) microinjection molding machine was used to prepare samples (3\*12.7\*60 mm) for flexural and impact tests. An injection pressure of 68 bar and a back pressure of 18 bar were used. Also, sheets of the different samples were obtained using a hot-plate press and a forced water circulation cooling system (LabPro 400, Fontijne Presses). To shape the specimens, stainless steel molds were used. The molding was conducted at a temperature of 185°C, with a pressure of 50 kN and a 15 minute cycle. Finally, the sheets were demolded and adjusted to the required dimensions for DMA tests (1.7\*12.7\*60 mm) using a computer numerical control

SO4

pelletized using a rotating cutter which produced pellets of about 5 mm long.

router. **Figure 1** shows the injected specimens of PP and a PP-bagasse biocomposite.

M of octadecyltrimethoxysilane in an 8:2 ethanol/water ratio as solvent was

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0.08 M. Samples were kept for 24 h in polypropylene
