2.4.1 Flexural properties

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

SW � 100 (1)

DSW � 100 (3)

<sup>4</sup> <sup>þ</sup> <sup>0</sup>:<sup>0076</sup> FC

FC <sup>þ</sup> <sup>0</sup>:<sup>0051</sup> VM

� 0:7223

A VM <sup>2</sup>

A

FC <sup>2</sup>

A VM <sup>3</sup>

(5)

DSW � 100 (2)

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 equa-

4239-14. A weight sample of 0.1 g was used on both equipments.

Parameter Equation

VSW: devolatilized sample weight (gr).

Thermosoftening Plastics

%EXTwater <sup>¼</sup> PEXTwater

%EXTethanol <sup>¼</sup> PEXTethanol

%LGN <sup>¼</sup> PLGN

%HCL <sup>¼</sup> PHCL

%CEL <sup>¼</sup> PCEL

Table 4.

92

PR�%MS � 100 (7)

PRlEXT�%MS � ð Þ <sup>100</sup> � %EXT (9)

%EXT ¼ %EXTwater þ %EXTethanol (8)

%HMC ¼ %HCL � %CEL (12)

HMC: proportion of hemicellulose.

Table 3.

Moisture content at 105°C %M<sup>105</sup> <sup>¼</sup> SW�DSW

Volatile matter %VM <sup>¼</sup> DSW�VSW

Equations used in the proximate analysis of lignocellulosic residues.

Fixed carbon %FC ¼ 100 � %M<sup>105</sup> � %A � %VM (4)

�11:2277

<sup>þ</sup>0:<sup>0383</sup> <sup>A</sup> VM

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

A VM <sup>þ</sup> <sup>4</sup>:<sup>4953</sup>

Superior calorific power SCP <sup>¼</sup> <sup>20</sup>:<sup>7999</sup> � <sup>0</sup>:<sup>3214</sup> VM

Ash %<sup>A</sup> <sup>¼</sup> ACW�CW

tions used for structural composition calculation of CHF and CCF.

Equation Reference

PR�%MS � 100 (6) [33]

PRlEXT�%MS � ð Þ <sup>100</sup> � %EXT (10) [32, 33]

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), %

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

PHCL � %HCL (11) [32]

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.


#### Table 5.

Injection molding parameters used.

#### Figure 1.

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