Chapter 2. Palmyra Fiber Separation Process And Properties Of Fiber And. Polyester Resin

Transcription

1 Chapter 2 Palmyra Fiber Separation Process And Properties Of Fiber And Polyester Resin 1.1 Introduction Fibers of lightweight and high strength are embedded in the week matrix to get high strength composites materials. The properties of the composites depend upon the properties of the individual components in the composites. Hence it is essential that the strength of fiber and matrix have to be established. This chapter deals with the fiber separation process and their properties. Moisture absorption of the Palmyra fiber in water and in seawater at room temperature is also studied. The matrix material used is rooflight resin and its mechanical properties are studied and presented here. 2.2 Fiber Separation process The Palmyra tree (Borassus flabellifer) is found in abundance in the southern part of Tamilnadu and in Puthukottai district. This has been the main source of revenue for the people in this area for more than three decades. Loose red soil is best suited to the palmyra and it withstands worst drought condition and high wind force. In Srilanka the Palmyra tree is grown in large numbers and it gives good economic value to the people involved in the Palmyra related cultivation and other related work. Figure 2.1 shows the Palmyra tree and Fig 2.2 shows the leaf stem base and leaf stem of the Palmyra tree. The Palmyra wood has been used as building material for a very long period. The leaf has been used for thatching. Every

2 scrap of the tree can be utilized for some purposes. Rich quantities of fibers are available in leaf stem base and leaf stem. These fibers are separated out from leaf stem base / stem by crushing manually by hand beating and then cleaning manually with the help of a device called comber. This method has been traditionally followed for fiber separation. Also retting followed by hand beating and then washing in water is also used to separate the fibers. These fibers are also separated by mechanical crushing between the rollers and followed by cleaning with motorized combing device fabricated for this purpose. The separated fibers are then dried on open sky. During the separation of leaf stem base fiber, a large quantity of fibrous waste is produced, which has no value and creates environmental problems. Figure 2.3 shows the fiber obtained from leaf stem base, leaf stem and fibrous waste obtained during the separation of fiber from leaf stem base and leaf stem. For the present study the fibers are separated from the leaf stem by a mechanical crushing machine specially, designed for this purpose as shown in Fig 2.4.The fiber thus obtained has lot of spur / pith and these spurs are cleaned by the motorized combing device as shown in Fig 2.5. The fibers and the waste materials are collected separately and both of them are used in the present study. The fibers are subjected to different mechanical test and environmental condition to study their mechanical properties and the environmental effect on mechanical properties.

3 36 AN 4 F1g21. Palmyra tree too Fig. 22 Leaf stem and leaf stem base

4 37 (a) Leaf stem base and stem fiber (b) Fibrous waste Fig-2.3 Leaf stem base, stem fiber and fibrous waste

5 38 S I ptt.i, FV^ W, * I I - L Ei Fig. 24 Mechanical crushing device for fiber separation k -t r - k t1l 1: Fig25. Motorized combing device for cleaning the fibers

6 n 2.3 Fiber properties The leaf stem base fibers are strong stiff and dark brown / black in color. The shape varies from fiber to fiber, and also non uniform. Normally they are circular or elliptical. Fiber diameter is measured by an electron microscope for 50 samples and it is found to be varying between 0.5 mm to 1.5 mm, which depends on the age and area of cultivation of the plant. The density is calculated by Archimedes principle and it is found to be in the range of g/cc The fibers obtained from leaf stem base are wheatish in colour. They can be twisted in to yarns and ropes in wet conditions. Fiber diameter, length, and strength depend upon the age and location of the plant. The length varies from for 1 to 1.5m and diameter is between 0.3 mm mm. The density of the fiber is in the range of g/cc. 2.3.lTensile Strength The cleaned and dried single fiber is mounted along the centerline of a slotted paper window as shown in Fig 2.6. The ends of the paper window are clamped in the grips of the Instron-testing machine with gauge length of 50 mm and its mid section is cut off during loading. The load is applied with the crosshead speed of 1 mm / min till the fiber brakes and the load deflection curve is recorded. At least 25 samples are tested the results are tabulated in table 2.1.

7 From the load deflection curve the strength and modulus values are calculated. Figure 2.7 a, 2.7 b, 2.7 c and 2.7 d shows the load deflection curves of Palmyra leaf stem fiber. From the above figures it is observed that the strength of the fibers is not uniform and it varies from 70 MPa to 250 MPa. Variation in fiber strength is observed even in the same diameter fiber. The fiber sample 3 with diameter of 0.5 mm has the maximum strength of MPa, where as the fiber sample 1 with diameter of.03 mm has the strength of MPa. From this it is observed that the strength is not proportional to the diameter. The modulus is also in the range of 2.5 GPa tol 0 GPa. The % of elongation varies betweeni.5 and 3. Strength of the fibers depends mainly on the fibrillar structure, micro fibrillar angle and the cellulose content. The relation between the elongation and the fibrillar angle is given by [49] 278±7.28x108+77x10 (2.1) The strength of the fiber is related with micro fibrillar angle and the cellulose content and is given by [49]. a W (2.2) Fig. 2.6 Tensile specimen for single fiber test

8 z -o 30 Co 0 J 20 ber 10 er 0 w Deflection mm 60 Fig 2.7 a. Load deflection curves of leaf stem Palmyra fiber z 0 J ample 13 ample 14 ample 15 ample 19 ample 22 04_ Deflection mm Fig.2.7 b Load deflection curves for the fiber of 0.5 mm diameter

9 z40 -o 0J30 iple 5 iple 8 iple 21 iple Deflection mm Fig.2.7 c Load deflection curves for the fiber of 0.6 mm diameter sample 4 -'i z 0 -J r Deflection mm Fig.2.7 d Load deflection curves for the fiber of 0.4 mm diameter

10 A.-, Table2.1 Tensile Properties of Palmyra leaf stem fiber Sample Fiber Load Deflection Strength No. Dia mm N mm MPa of Modulus Strain n elongation GPa

11 ] J Water absorption kinetics of palmyra fiber Because of their lignocellulosic and organic origin, palmyra fibers exhibit a hydrophilic nature. To achieve the full potential of polymer composites, they must have a good environmental stability. As a raw material for polymer composites, the water-absorption behavior of this fiber has to be comprehensively investigated. Water-diffusion characteristics of palmyra fibers in water and seawater have been investigated and the results are discussed. About 0.5 g of dried and fiber having an approximate length of 5 cm is taken for the water-sorption examination. The samples are immersed in raw water and seawater at room temperature. Increase in weight of the samples is noted at specific time intervals. This process is continued until equilibrium is reached. The molar percentage uptake Q t for water for loog of polymer is plotted against the square root of time. The value is expressed as Q =w2-w1 18W1 2.3

12 45 Where 18 is the relative molecular mass of water. When equilibrium is reached, Q t is taken as the molar percentage uptake at infinite time, Q. [78]. The water sorption of fibers is calculated as the number of moles of water absorbed by bog of the fiber. The major factors that control the interaction between fibers and water are diffusion, permeability, and sorption. Palmyra fiber is lingo cellulose, they contain waxy material and water-soluble substances. The swelling behavior of natural fibers is greatly affected by its morphology as well as physical and chemical structures. The water penetration through the natural fiber can be explained using the diagram given in Fig 2.8 [79]. From the figure it is clear that the water penetration through the microspores of the fiber surface by capillary action is evident from the model. The fibers have a porous internal structure. The penetrating water enters onto the fiber structure and stay in the porous medium. The waxy materials present on the fiber surface help to retain the water molecules in to the fiber. The porous nature of the palmyra fibers accounts for the large initial uptake at the capillary region. Sreekala M.S. et.al [79] reported the water absorption of oil palm fiber. The water entering into the fiber produces an advancing front of water. The portion behind the advancing front is swollen relative to the portion ahead of the front and the outer layer of the fiber continuously changes to accommodate the further sorption. This process stops when the sorption reaches equilibrium.

13 Water Lacuna Micropores Waxy materials Fib iii Is Water penetration Cross section of fiber Fig2.8. Water sorption model The water molecule is small and strongly associated through hydrogenbond formation The initial hydrogen bonds in the water-accessible regions of the fiber are broken to form a sol-like structure that slowly is converted into a gel form with the reformation of inter chain of hydrogen bonds. They can form strong localized interactions with hydroxyl groups available on cellulose and lignin. Water sorption is mainly dependent on the penetrativity of water and radii of the capillaries. The length and radii of the capillaries determine the capillary action. The diffusion of water in water- cellulose system is reported to be non- Fickian or anomalous and two-stage absorption behaviour is reported in natural fibers [79]. In this case only single stage behaviour is observed in both water and seawater, which is shown in Fig 2.9. The initial stage of water penetration is by capillary action, which is shown by the linear portion of the curve, and the second nonlinear portion of the moisture absorption is due to the late filling of micro pores. The equilibrium sorption is higher for seawater, which is due to the presence of Na and Cl -. But in contrast to this Sreekala M.S. et.al [79] observed

14 Time (mm) Fig. 2.9.Moisture absorption curves lower equilibrium of sorption in sea water than distilled water at room temperature and higher equilibrium sorption than distilled water at high temperature for OPEFB fibers Matrix properties The physical properties of roof light resin as specified by the supplier is given in table 2.2 To find the mechanical properties a plate is cast with neat resin mixed with accelerator and catalyst in a mould of 150mm X 150mm X 3mm. Tensile samples of 150mm X 10mm are cut from plate and tested

15 48 INSTRON testing machine. Four specimens are tested and the average strength is estimated as 33MPa and the tensile modulus is 1000MPa. Impact samples of size 12.7mm X 65mm are tested by impact testing machine and the impact strength is observed as 0.4 J/cm 2. Bending samples of size 10mm X 80mm are tested by three-point loading and bending strength of 40MPa is observed. Shear specimens with length equal to 6 times of its thickness is tested by three points loading and shear strength is calculated as 4MPa. Table 2.2 properties of the Rooflight resin. Appearance Clear liquid Viscosity 270cps Acid value 23.68mg koh/gm Volatile content 40.59% Gel 14'20" Shelf life 3 months Specific gravity Conclusion The fiber separation process and its physical and mechanical properties are studied. From the test it is observed that the fiber size and the strength are not uniform. Variation in fiber strength is observed even in the same diameter fiber. The moisture absorption characteristic of the fiber is also studied. The mechanical properties of the matrix material are studied and presented in this chapter