2. Materials and methods

### 2.1 Materials

environmental impacts derived from raw material acquisition, operation life of the product, and end of life processes. Since natural fibers are in most cases residues from agricultural practices, their incorporation on an industrial processes serves as a waste management alternative where the fibers are recycled as reinforcement for plastic materials, helping to minimize environmental burdens from their primary process in agriculture where they are treated as conventional waste. Also, the reincorporation of these residues contributes to assess environmental impacts of raw material transportation at a local scale. Furthermore, this material fraction substitution reduces the amount of plastic material needed to fabricate one product, and as a consequence, less quantity of polymers are demanded for production, and less extraction of fossil resources has to be made in order to supply this productive sector. Regarding processing, biocomposites offer a wide amount of advantages related to processing techniques. These materials not only can reduce the melting temperatures on the process, contributing to lower the embodied energy of the product and consequently the carbon emissions of the product, but also can be processed with existing tools and procedures, which means that the producer does not have to make major adjustments on his production line to work with them.

Thermosoftening Plastics

Nevertheless, not every composite is easy to process, and so traditional material may have a favored position related to biocomposites due to its advanced and wellstudied processing techniques, and as direct result, fewer residues can be achieved during the fabrication process. Still some experiences with biocomposites have led to significant reduction of Greenhouse Gasses during processing and transformation stages [26]. In the case of thermoformed trays, it was found that by replacing talc fillers with starch fibers, the carbon footprint for this product was reduced

Other outstanding characteristic of biocomposites compared to their traditional counterparts is the reduction of weight for the final product. For automotive applications, this characteristic could allow savings of carbon emissions by reducing the total weight of the vehicle and thus consuming less fuel without compromising the integrity of the material properties and the security guidelines of the automotive industry. Materials that possess high specific stiffness and specific strength are often very valuable in applications in which weight will be a critical factor [25], which makes biocomposites ideal candidates for automobile design and spare parts production. Different automakers believe that all advanced composite car bodywork could be around 50–67% lighter than current similarly sized steel auto-body, 40–55% lighter than an aluminum auto-body, and 25–30% lighter than a steel autobody. Nevertheless, there are not bio-based materials on commercial use or development that can be fully considered sustainable [28]. It is a fact that products derived from renewable resources tend to be competitive in the market if they prove to be similar or better than other products regarding performance and price. In fact, Reinders et al. [29] said that full bio-based brands usually have stronger purchase intentions than other brands, including those that are partially composed by bio-based products. However, the fact that a product has a renewable origin does not mean that its environmental performance is better when comparing it to traditional products in the market. A case-based evaluation is necessary to define the environmental aspects of a product and thus the sustainable nature of the product [30]. Virtually, biocomposites can be considered sustainable materials compared to traditional composites or fossil-based polymeric materials. The renewable provenance of these materials and the availability of the resource can suggest better environmental performance among its life cycle, easing pressures over the natural systems. However, critical aspects of the elaboration process during the materials life cycle can lead to different types of environmental impacts, which in turn, may

around a 20% regarding gas emissions from processing [27].

be worse than the ones derived from traditional composite elaboration.

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Coconut coir (CCF) was obtained from "Kiero Coco" S.A (Manizales-Colombia), and coffee husk fiber (CHF) was obtained from a local coffee mill located in Tuluá-Colombia. Recycled polypropylene (rPP) was a postindustrial waste collected from extrusion and injection processes carried out in the materials laboratory of the Autónoma de Occidente University (Cali, Colombia). Maleic anhydride grafted polypropylene (Licocene MAPP 6452 by Clariant) was used as coupling agent.

#### 2.2 Natural fibers characterization

The time between the generation of the different fiber waste and its storage (at 20°C) was less than 8 hours, in order to minimize biochemical changes in the fibers. After separation, the fibers were dried in an oven at 45°C until reaching constant weight. Drying process was carried out at this temperature in order to avoid the elimination of volatile compounds and degradation of the lignocellulosic composition. After drying, the samples were milled (particle size <1 mm) in an impact mill (Retsch SR200). The milling time was 15 minutes for CHF and 30 minutes for CCF. Finally, fibers samples were stored in polyethylene bags with a hermetic seal at room temperature. After the characterization, the fibers were sieved in ASTM sieves, with the purpose of reaching a 60 mesh particle size, established by the ASTM standards for the analysis of solid samples.

The fibers (CHF and CCF) were characterized by proximate and elemental analysis, calorific power, and structural composition. These analyzes were performed in triplicate. Through the proximate analysis, the percentage of moisture content (M), volatile matter (VM), ash (A), and fixed carbon (FC) was determined according to ASTM D7582-12 [31]. These analyzes were performed using approximately 1.0 g of sample in a Leco brand thermogravimetric analyzer, TGA-601. Table 3 shows the equations used in the determination of the proximate analysis of CHF and CCF. The calorific value was calculated using 1.0 g of sample in a Leco AC-350 calorimeter pump, following the ASTM 5865-13 standard. The calorific value establishes the amount of energy per unit mass that the waste can deliver when it is completely oxidized. This property was calculated using the equation also presented in Table 3.


2.3 Preparation of the biocomposites

DOI: http://dx.doi.org/10.5772/intechopen.81635

r-PP-CCF biocomposites.

2.4.1 Flexural properties

Table 5.

Figure 1.

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Injection molding parameters used.

2.4 Characterization of the biocomposites

r-PP and its biocomposites were compounded in a co-rotating twin screw extruder (Harden Industries Ltd., China). For each case, MAPP, CCF, and CHF fibers were physically premixed with r-PP pellets in a plastic bag using 30% of fibers and 4% of MAPP in weight. A temperature gradient from 140 to 170°C from the feeder zone to the die was used. The rotation speed of the twin-screw was 50 rpm. The outcoming cord of r-PP and its biocomposites from the extruder were pelletized using a mill which produced pellets of about 5 mm long. After the pelletization process, the r-PP and its biocomposites samples were dried in an oven at 85°C followed by an injection molding process. A BOY XS (BOY Machines, Inc., USA) microinjection molding machine was used to prepare samples for flexural and impact tests. Table 5 summarizes the injection-molding processing parameters used. Figure 1 shows the injected specimens of neat PP, r-PP, r-PP-CHF, and

Recycled Polypropylene-Coffee Husk and Coir Coconut Biocomposites: Morphological…

Three point bending flexural tests were performed with an INSTRON universal testing machine model 3366 according to the ASTM D 790-17 as shown in Figure 2.

Parameter Value Barrel temperature(°C) 185 Nozzle temperature (°C) 180 Injection time (s) 3.8 Cycle time (s) 37.5 Screw travel (mm) 18.7 Back pressure (bar) 60 Injection pressure (bar) 80

Injected specimens of: (a) neat PP, (b) r-PP, (c)-PP-CHF and (d) r-PP-CCF biocomposites.

SW: sample weight (gr), DSW: dry sample weight (gr), ACW: crucible weight + ashes (gr), CW: crucible weight, VSW: devolatilized sample weight (gr).

#### Table 3.

Equations used in the proximate analysis of lignocellulosic residues.

The elemental analysis was carried out in a Leco CHN-628 analyzer to determine the content of carbon (C), hydrogen (H), and nitrogen (N) according to ASTM D 5373-14 and in a Leco S-632 to quantify the sulfur content (S) according to ASTM D 4239-14. A weight sample of 0.1 g was used on both equipments.

The structural composition of the fibers was determined by the quantification of extractive compounds (EXT), lignin (LGN), cellulose (CEL), hemicellulose (HMC), and inorganic compounds (ashes). The preparation of the fibers was carried out following the standard NREL/TP-510-42620. In order to obtain the percentages of CEL, HMC, and LGN, it is necessary to perform two Soxhlet extractions to the fibers using water and ethanol as solvent, as indicated in the NREL/TP-510-42619 standard. The insoluble acid lignin percentage (LGN) or Klason lignin was calculated according to the standard NREL/TP-510-42618. The holocellulose percentage (HLC) was determinate by following the ASTM D1104 standard, while the cellulose percentage was determinate following the Han and Rowell methods [32]. Table 4 shows the equations used for structural composition calculation of CHF and CCF.


Where, % EXT: proportion of total extractives, % EXTwater: proportion of extractives in water, % EXTethanol: proportion of extractives in ethanol, PEXTwater: weight of extractives in water (gr), PEXTethanol: weight of extractives in ethanol (gr), PR: dry sample weight (gr), % MS: percentage of dry matter, % LGN: proportion of lignin, PLGN: weight of lignin (gr), PRlEXT: weight of the sample free of extractives (gr), % HCL: proportion of holocellulose, PHCL: weight of holocellulose (gr), % CEL: percentage of cellulose, PCEL: weight of cellulose (gr), % HMC: proportion of hemicellulose.

#### Table 4.

Equations used in the determination of the structural composition of lignocellulosic residues.

Recycled Polypropylene-Coffee Husk and Coir Coconut Biocomposites: Morphological… DOI: http://dx.doi.org/10.5772/intechopen.81635
