This use is justified by their durability in the textile field, their availability and their specific properties. However, with the increase of demand in green materials combined to the decrease of growing space for these common plant fibers, and the race towards new tropical species which are accessible and at lower cost, some recent scientific works have been carried out in this field. Researches enabled to study new plant fibers such as those derived from pineapple leaves, Rhectophyllum camerunense roots ,Okra stems , Triumfetta cordifolia , Sida cordifolia , Arundo donax, Lygeum spartum , Coccinia grandis for their use as reinforcement for composite materials.They are characterized in order to choose the resin and the process for manufacturing a composite membrane reinforced by this tropical fiber. In South Cameroon, they are traditionally used to make hood ropes because of their resistance and work ability.In this article, the fiber extraction procedure was presented.
The real density was assessed by using the helium pycnometry technique. Porosity was evaluated by density methods. Water content, organic and mineral matter content and water absorption capacity were calculated according to ASTM D1576-13, ASTME1755-01 and ASTM D 5229 standards, respectively. Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance was used to determine chemical structure and crystallinity index of the fiber. Cellulose, hemicellulose,pectin, lignin and extractives contents were determined by using TAPPI test methods. Chemical composition of CL fibers was carried out in accordance with methods based on successive extraction of the components of the fibrous material by solvents as described by Sango . This technique consits in isolating the different substances contained in the fiber. Ethanol-benzene extraction was first done. It was used to remove components such as dyes, wax, fats and lipids which are generally found in vegetable fibers. It was carried out with Soxhlet on previously dehydrated and crushed fibers.
Then, hot water extraction was carried out to remove the residues of extractables still present in the sample obtained after extraction with ethanol-benzene and to solubilize all the mineral matter contained in the fiber. The pectin extraction was the third to be carried out. The residue from the previous extraction was heated in a water bath under reflux at 80˚C while stirring with 2% of hydrochloric acid solution. Then, holocelul lose was extracted by total delignification of the sample obtained after extraction of the pectins by using 1% sodium hydroxide solution. The extraction of cellulose was the last step of the process: the previous holocel lulose sample was dissolved in a17.5%NaOH solution and then diluted in the same 8.75%NaOH solution. The solid residue obtained was successively washed with 1% acetic acid solution and distilled water. Hemicellulose content was deduced directly by subtracting cellulose content from that of holocellulose. A mass of 5 g of ground and dried fiber was used.Lignin content was determined by the KLASON method .
A sample of 1g of residue taken after pectins extraction was hydrolysed in 72% sulphuric acidsolution, then heated under reflux in 3% sulphuric acid solution before being cooled and rinsed thoroughly with hot distilled water. The average moisture content of CL fibers is 6.47%. This relatively low value content would predispose to good fiber-resin interaction in the manufacture of composite materials reinforced with the new lignocellulosic resource. A product made from this fiber would offer good comfort feeling because it will absorb less than 7% moisture content, very close to that of cotton and flax . It is reported in litterature that high moisture content undermine the stability of the composite in terms of dimensions, tensile strength, swelling behaviour and porosity formation .
Therefore, lower moisture content is desirable. Applying Equation , porosity fraction of CL fiber is between 13% and 47%.Although useful in applications where shock and vibration damping are required,and in resin impregnation during composite manufacturing, large porosities have detrimental impact on the mechanical properties of composite materials because they promote early failure of the parts due to the appearance areas of stress concentration and the reduction of effective cross-section.Table 1 shows porosities and densities of some common natural fibers used as reinforcement in composite materials. With the advancement in our time, people have placed a great emphasis on environment-friendly materials and processes.