Gen Engg - IJGET - DEVELOPMENT - T Karthik - Unpaid

International Journal of General Engineering and Technology (IJGET) Vol.1, Issue 1 Aug 2012 26-43 © IASET

DEVELOPMENT OF ECOFRIENDLY TEXTILE COMPOSITES FROM CALOTROPIS GIGANTEA BAST FIBRE T.KARTHIK & P.GANESAN Department of Textile Technology, PSG College of Technology, Coimbatore, India

ABSTRACT In the latest years industry is attempting to decrease the dependence on petroleum based fuels and products due to the increased environmental consciousness. This necessitates an investigation on investigate environmentally friendly, sustainable materials to replace existing ones. Calotropis Gigantea is a soft shrub that can grow in dry habitats and in excessively drained soils. In this work, stem fibre of Calotropis Gigantea and PLA have been used as a reinforcement and matrix respectively and are compared with Flax / PLA composites. The chemical treatments such as alkali treatment and acetylation were done to improve the mechanical properties of the composites. The results showed that the mechanical properties of Calotropis Gigantea were less than the flax fibre composites which is expected due to better flax fibre properties compared Calotropis Gigantea. The suitable coupling agent and its concentration can be used out to improve its mechanical properties. The Calotropis Gigantea composites can be used as low end applications in automotive industry.

KEY WORDS: Ecofriendly, Calotropis Gigantea, Fibre-Reinforced Composite, Thermoplastics.

INTRODUCTION The interest in using natural fibres such as different plant fibres and wood fibres as reinforcement in plastics has increased dramatically during recent years. The need for materials having specific characteristics for specific purposes, while at the same time being non-toxic and environmentally friendly, is increasing, due to a lack of resources and increasing environmental pollution. Studies are ongoing to find ways to use lingo-cellulosic materials in place of synthetic materials as reinforcing fillers. Thus, research on the development of composites prepared using new fibrous materials is being actively pursued.

Bio-fibres like sisal, coir, hemp, oil palm are now finding applications in a wide range of industries. The field of bio-fibre research has experienced an explosion of interest, particularly with regard to its comparable properties to glass fibres within composites materials. The main area of increasing usage of these composites materials is the automotive industry, predominantly in interior applications. Material revolution of this century may be provided by green composite materials.

Sustainability, ‘cradle-to-grave’ design, industrial ecology, eco-efficiency, and green chemistry are not just newly coined buzz words, but form the principles that are guiding the development of a new generation of ‘green’ materials.

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

Although biofibre reinforced polymer composites are gaining interest, the challenge is to replace conventional glass reinforced plastics with biocomposites that exhibit structural and functional stability during storage and use and yet are susceptible to environmental degradation upon disposal. An interesting approach in fabricating biocomposites of superior and desired properties include efficient and cost effective chemical modification of fibre, matrix modification by functionalizing and blending and efficient processing techniques. Another interesting concept is that of ‘‘engineered natural fibres’’ to obtain superior strength biocomposites. This concept explores the suitable blending of bast (stem) or leaf fibres. This research work explores the possibility of using bast fibre obtained from giant milkweed to produce composites. The milkweed fibre is seen as a possible raw material for reinforcements in composites. This work will increase the application of milkweed fibre in industrial textiles.

MATERIALS AND METHODS Fibre Extraction In hand extraction, the outer bark of the stem is initially removed from the half dried calotropis gigantea followed by extraction of fibre through simple scraping with a sharp knife.

Analysis of Chemical Composition of Fibre The fibre extracted was treated to determine the fibre composition.

Extractible Content The air dried sample of 5g was weighed in an extraction thimble and placed in Soxhlet extraction unit. A mixture of ethanol and toluene (1:2) was used as solvent and extraction process continued for a period of five hours at 900 C. After extraction the sample was rinsed with ethanol and hot water and dried up to constant weight at the temperature of 60°C. The extractibles were calculated as a percentage of the oven dried test sample and the method has been repeated for each sample.

Lignin Content Two grams of extracted sample were placed in a flask and 15ml of 72% sulphuric acid was added. The mixture was stirred frequently for two and half hours at 25°C and 200ml of distilled water were added to the mixture. Then the mixture was boiled for next two hours and cooled. After 24 hours, the lignin was transferred to the crucible and washed with hot water repeatedly until becoming acid free.

The collected lignin was dried at 105°C and cooled down in desiccators and weighed. The drying and weighing were repeated until constant weight.[17] Holocellulose Content Three grams of air dried stem fibre were weighed and placed in an Erlenmeyer flask and then, 160ml of distilled water, 0.5ml of glacial acetic acid and 1.5g og sodium chloride were added successively. The flask was placed in water bath and heated up to 75°C for an hour and then additional 0.5ml of glacial acetic and 1.5g of sodium chloride were repeated two times hourly. The flask was placed

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in an ice bath and cooled down below 10°C. The holocellulose was filtered and washed with acetone, ethanol and water respectively and at the end, sample was dried in oven at 105°C before weighed. α –Cellulose Content Two grams of holocellulose were placed in a beaker and 10ml of sodium hydroxide solution (17.5%) was added. The fibres were stirred up by glass rod so that they could be soaked with sodium hydroxide solution vigorously. Then sodium hydroxide solution was added to the mixture periodically (once every five minutes) for half an hour. The holocellulose residue was filtered and transferred to the crucible and washed with 100ml of sodium hydroxide (8.3%), 200ml of distilled water, 15ml of acetic acid (10%) and again water successively. The crucible with α – cellulose was dried and weighed.

Hemicellulose Content The content of Hemicellulose of stem fibre was calculated from the equation Hemicellulose = Holocellulose – α-Cellulose Physical Properties of Fiber The untreated and treated fibers were tested to determine the physical properties.

Single Fibre Strength and Elongation The single fiber strength, an average (±0.4) value for twenty five samples was determined using instron instrument (5500R), on 15 mm fibre length fixed between the movable and fixed clamps provided in the instrument. The weight of the above clamped fibre is sensed automatically by a microbalance online with the equipment. The average single fibre strength (±0.5%) on twenty five fibre samples for the raw fibres were measured using the above instrument as per ASTM standards using testing speed and gauge length values of 100 mm/min and 100 mm respectively after conditioning the samples at the standard temperature and relative humidity (27.0 ± 0.2 °C and 65 ± 1%). Stress–strain curves for the fibres were recorded by performing the tests as described above on the random fibre samples.

Fiber Diameter The diameters of the fibres were measured using the Projection Light Microscope (WESWOX, Optic Model 385/385 A) with a magnification of 200x. Averages of fifty randomly chosen readings were taken to compute the mean fibre diameter with an accuracy of ±1.5%. Longitudinal optical micrographs of fibre samples with a magnification of 200 were photo- graphed on the Optical Microscope.

Moisture Regain The conditioning oven is used to determine the moisture regain and moisture content of the fibre. Two grams of the sample was taken in a bottle and placed in the main chamber. The oven was switched on and the thermostat set at 110°C. Heating was continued for 2 h, the material weighed, and the reading noted. It was again switched on and after heating for 30 min the material was weighed. This was carried on till the values stabilized.

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

Then using the following formula the moisture content and moisture regain were calculated.

Weight of bottle + stopper = W1 Weight of bottle + stopper + sample (moist) = W2 Weight of bottle + stopper + sample (dry) = W3 Moisture regain (R) = (W2 - W3) x 100 (W3 -W1)] Composite Fabrication Manufacturing process of composites was done at Composite Fabrication Centre, IIT Madras.

The resin polylactic acid with synthetic bio-degradable mixture (BF 703 B grade) was used for the composite preparation. Initially, fibres were chopped into 30-50 mm in length converted into web form to get uniform distribution of the fibre. The prepared web was cut in 30×30 cm dimension and laid on the mold surface. Polylactic acid resin and its mixture in granule form were randomly distributed and one more web layer was spread to form a sandwich distribution. It was noted to spread aluminum foil sheet above and below sandwich for proper composite releasing from the mold. Core was prepared to get a volume fraction of fibre-resin in the ratio of 40/60 .Compression molding technique was used for manufacturing fibre matrix composite. The melt temperature of the die was maintained at 180- 200ºC and at a pressure of 40-60 bar and core material was allowed to remain in this condition for one hour.

After compounding the core compounds were allowed to cool in room temperature for 2 hours. The sample conditions was followed to prepare composites of raw fibre , alkaline treated and acetylation treated fibre of Calotropis and flax with PLA resin mixture and for compounding two samples were prepared .

CHEMICAL TREATMENT Alkali Treatment In this process untreated calotropis gigantea stem fibres were dipped in 10% NaOH solutions at room temperature for an hour maintaining fibre weight to liquor ratio of 1:50. After treatment, the fibres were neutralized with 5% acetic acid solution and thoroughly washed with distilled water. The washed samples were dried at 85ºC until obtaining a constant weight Acetylation Process The calotropis gigantea stem fibres were soaked in demineralised water for an hour, filtered and placed in a round bottom flask, containing acetylating solution. Acetylating solution consist of 250 ml toluene, 125 ml acetic anhydride (2:1) and a small amount of catalyst H2SO4. The process temperature of acetylation was 60°C and duration was 30min. After modification, the fibre was washed periodically with distilled water until acid free. Finally modified fibres were air dried for certain time and then at 85ºC until obtaining constant weight.

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Testing of Composites The fabricated composites were tested for various mechanical properties such as tensile, flexural and impact testing.

Tensile Testing Tensile test is to analyze the compression resistance (the property of a material to oppose its change in dimension under compaction) and recovery properties (the property of a material to regain its original dimensions after release from compaction).The results obtained are essentially dependent on the type of compression fixture used. Also, the gauge length is conical, as if it is too long, the specimen will buckle and flex, resulting in premature failure. If it is too short, then the proximity of the tabs will adversely affect the stress state, resulting in artificially high values. Cylindrical in design, a small specimen sits within a set of trapezoidal grips, encased in collars and an alignment shell. The gauge length depends on the type of test material and varies between 12.7mm for longitudinal specimens and 6mm for transverse specimens.

Tensile testing utilizes the test specimen as Shown in the Fig. 1, it consists of two regions: a central region called the gauge length, within which failure is expected to occur, and the two end regions which are clamped into a grip mechanism connected to a test machine INSTRON 5500R. These ends are usually tabbed with a material such as aluminum, to protect the specimen from being crushed by the grips.

Fig: 1 Specimen Size for Tensile Testing The test specimens were conditioned at 23±2 ºC, 50±5 % RH for at least 40 h according to ASTM D-3039.Tensile properties of Calotropis Gigantea and flax composites were measured using an Instron Universal Testing Machine Model 3365 in accordance with ASTM Standards D-3039. The instrument was calibrated with a gauge length of 50 mm with a sample size of 300 ×25 mm. The test was

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

repeated for 5 times each for untreated, alkaline treated and acetylated specimens of Calotropis and flax composites.

Flexural Rigidity The flexural test measures the force required to bend a beam under three point loading conditions. The data is often used to select materials for parts that will support loads without flexing.

Flexural modulus is used as an indication of a material’s stiffness when flexed. After molding, test specimens were conditioned at 23±2 ºC, 50±5 % RH for at least 40 hours according to ASTM D790.Flexural properties of Calotropis Gigantea and flax composites were measured using an Kalpak Universal Testing Machine Model (KIC-2-0200-C capacity 20kN) in accordance with ASTM Standards D-790 as shown in the Fig. 2. The instrument was calibrated with a span length of 50 mm at a sample size of 12 ×120 mm.

Fig: 2 Three-Point Flexural Rigidity Testing Machine Impact Testing Notched Izod Impact is a single point test that measures a materials resistance to impact from a swinging pendulum. Izod impact is defined as the kinetic energy needed to initiate fracture and continue the fracture until the specimen is broken. Izod specimens are notched to prevent deformation of the specimen upon impact. This test can be used as a quick and easy quality control check to determine if a material meets specific impact properties or to compare materials for general toughness.

Fig: 3 Izod Sample Geometry

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The test specimens were conditioned at 23±2 ºC, 50±5 % RH for at least 40 hours according to ASTM D-256. The result of the Izod test is reported in energy lost per unit of specimen thickness (such as ft-lb/in or J/cm) at the notch ('t' in graphic at right ) as shown in the figure 3. Additionally, the results may be reported as energy lost per unit cross-sectional area at the notch (J/m² or ft-lb/in²). Impact properties of Calotropis Gigantea composites and flax composites were measured with an Frank Testing Machine in accordance with ASTM Standards D-256.The sample composites were analyzed with a gauge weight of 25J with a sample size of 13×65 mm. Both raw and NaOH treated fibre produced composites of Calotropis and flax were tested

RESULTS AND DISCUSSIONS The stem of giant milkweed plant has been collected from Sankari and Udumalpet. The outer skin of the bark was peeled from the stems of the plant by hand and the fibre was extracted. The extracted fibre was tested for fibre properties such as fibre length, fibre diameter, strength, elongation and moisture regain. The fibre composition was determined by various experiments and the results are discussed below.

Fibre Composition The different elements in the fibres were calculated by Percentage fibre composition = (a-b)/a× 100 Where a - Initial fibre weight, b - Extract weight Table 1: Calotropis Gigantea and Flax Fibre Composition (%)

S. No

Fibre composition

Calotropis Gigantea fiber % composition

Flax fiber % composition

1

Wax content

2.98

1.57

2

Lignin

3.5

6.5

3

Holocellulose

79

65

4

α-cellulose

51.5

47

5

Hemicellulose

27.5

18

6

Ash

2.2

-

A good understanding of the composition of fibre is needed to develop fibre reinforced composites. From the Table 1 it is understood that the fibre contains nearly 80% of cellulose content.

Thus the investigation shows that fibres obtained from milkweed stems have much higher cellulose and lower lignin content than the flax fibres. The cellulose content of the milkweed stem fibres is much higher than that in the flax fibres but lower than that of cotton. The milkweed stem fibres also have much lower lignin content when compared with the flax fibres but higher than the lignin content in cotton. This property makes it a suitable raw material to produce composites with adequate strength and durability.

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

The study showed us that, milkweed stems are very sensitive to the alkaline treatment.

Relatively mild treatments using alkali alone have produced milkweed stem fibres with high cellulose content .In addition to the treatment conditions, the chemical composition of the milkweed stems influences the amount of cellulose in the fibres obtained.

Physical Properties of Fibres Fibre diameter The fiber diameters of Raw, NaOH treated and Acetylated fibre samples are given in Table 2.

Table: 2 Fibre Diameter of Raw, NaOH Treated and Acetylated Fibre

SL.No

Fiber Particulars

Calotropis Gigantea Dia (Âľm)

Flax Dia (Âľm)

1

Untreated fiber

134.87

131.642

2

NaOH treated fiber

140.026

136.871

3

Acetylated fiber

139.738

135.942

From the results, it was observed that the diameter of fibre after alkaline treatment increases due to the fiber swelling action in both calotropis and flax. It was also observed that the untreated fibre surface was rough, exhibiting waxy and protruding parts. The partial removal of lignin content is shown by change in colour of the fibre. After the acetylation treatments the non-cellulosic content present in the fiber is removed and the fibrillation is more which leads to increased amount of surface damage of the fiber. The hydroxyl group is replaced by the acetyl groups and this can also be the reason for the decrease in moisture absorption. It can be seen that the variations in diameter after acetylated treatment is very minute and not much significant in the fibers.

Single fibre strength The fibre extracted from the stem of Calotropis stem was tested for its Single Fibre Strength using INSTRON 5500R are given in Table 3.

Table: 3 Fibre Properties

Parameters

Breaking strength(g)

Raw Fibre

Calotropis 427.7

Breaking Elongation (%) Flax 740.75

Calotropis 1.6

Flax 2.34

NaOH Treated

400.28

707.95

2.9

2.94

Acetylated

267.85

415.87

1.27

1.98

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T.Karthik & P.Ganesan

Milkweed stem fibres have strength higher than milkweed floss, similar to that of cotton as determined in the stress–strain curves. However, the strength of the milkweed stem fibres is similar or higher than that of other common bast fibres such as jute and the fibres obtained from various agricultural by-products. Breaking elongation of the milkweed stem fibres is higher than that of milkweed floss and most other bast fibres but lower than the elongation of the cotton fibres. The high elongation of the milkweed stem fibres indicates that the fibres may have a higher microfibrillar angle than the common bast fibres. The flax fibres have better fibre properties when compared to Calotropis Gigantea as shown in Table 3. The NaOH treated fibres have less strength compared to raw fibres due to partial removal of lignin and the acetylated fibres significantly losses the strength both in calotropis gigantea and flax fibres due to breaking of –OH bonds and replaced with acetyl groups.

Moisture regain The moisture regain of the fibres was determined according to ASTM standard method 2654 using standard conditions of 21°C and 65% relative humidity .The moisture regain of the Calotropis Gigantea milkweed fibre and flax fibre are shown in Table 4.

Table: 4 Comparison of Moisture Regain Values of Calotropis Gigantea and Flax Fibre Calotropis Gigantea Parameters Raw Fibre NaOH Treated Acetylated

Flax

(% Moisture Regain) 9.7

(% Moisture Regain) 12

13.5 6.3

15.4 8.5

The alkaline treated fibers show a more moisture regain compared to untreated fiber. This can be due to the removal of waxy content and other impurities like fat, proteins etc which reduces the moisture absorbency. The reduction in moisture regain after acetylation process is due to the modification of cellulosic fibres and hydroxyl groups of the cell wall replaced by acetyl groups, which modify the properties of these fibers so that they become hydrophobic which could stabilize the cell wall against moisture, improving dimensional stability and environmental degradation.

FTIR analysis of fibre FT-IR microscopy is a well-established method for the chemical identification of particles or contaminants and for visualizing the distribution of certain substances in complex compounds.

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

Table: 5 FTIR Chart Fibre Component

Cellulose

Hemicellulose

Lignin

Wave number (cm-1) 4000-2995 2890 1640 1270-1232 1170-1082 1108 4000-2995 2890 1765-1715 1108 4000-2995 2890 1730-1700 1632 1613, 1450 1430 1270-1232 1215 1108 700-900

Functional Group OH H-C-H Fibre-OH C-O-C C-O-C OH OH H-C-H C=O OH OH H-C-H C=C C=C O-CH3 C-O-C C-O OH C-H

Compounds Acid, Methanol Alkyl, aliphatic Adsorbed water Aryl-alkyl ether Pyranose ring skeletal C-OH Acid, methanol Alkyl, aliphatic Ketone and carbonyl C-OH Acid, methanol Alkyl, aliphatic Aromatic Benzene stretching ring Aromatic skeletal mode Methoxyl-O-CH3 Aryl-alkyl ether Phenol C-OH Aromatic hydrogen

Due to the usage of modern focal plane array detectors, this technology has advanced to a new imaging technique during the last few years. It allows for the measurement of even large sample areas with a very high lateral resolution within a few minutes. The assignments of wave numbers for different functional groups are given in the Table 5.

(a)

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T.Karthik & P.Ganesan

The effectiveness of chemical treatments carried out on the fibre was assessed by FTIR spectroscopy, which yields the progress of the chemical reaction in time. The FTIR spectra of untreated, alkali-treated and acetylated fibers are shown in the Fig.4. It can be noted that there is an absorption band at~1700-1750 cm-1 and 1316 cm-1 for the treated fiber is reduced compared to the raw fibers. This shows that there is partial reduction in the lignin content. The vibrations at 2880-2850 cm-1 indicate CH and CH2 symmetrical stretching formed from the wax variations due to the treatment.

(b)

(c) Fig: 4 FTIR of (a) Raw (b) Alkali Treated (c) Acetylated Fibre Also the absorption at 1716 cm-1 is reduced which means the acid carbonyl absorption is reduced indicating the corresponding reduction in hemicelluloses (xylans) content. Alkali treatment is expected to reduce the hydrogen bonding in cellulosic hydroxyl groups by the removal of the carboxyl group by the alkali, thereby increasing the OH concentration due to the changes in the spiral angle and

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

higher exposition of OH, when cellulose I changes to cellulose II. The increased intensity of the OH revealed by FTIR results indicates that the alkali treatment was effective.

After acetylating reaction, new acetyl groups were added to cellulose, as indicated in curve, with the vibrations at 1732 cm-1 (–C=O) and 1108.06 cm-1 (C=O). The spectrum of unmodified cellulose shows an absorption peak at 1315 cm-1 attributed to the –C–H bending vibration. The spectra at 12401350 indicate C=O aryl and C=O aromatic group indicating change in the lignin and cellulose part due to the acetylation process. As the reaction progresses the content of acetyl groups increases which is revealed by an increase in the intensity of the peak at 1732 cm-1.

Composite Fabrication Manufacturing process of composites was done at IIT Madras, Composite Fabrication Centre.

Extracted fibre was compounded with Polylactic acid resin with its synthetic bio-degradable mixture in compression molding manufacturing technique. A total of 12 samples were fabricated using raw, alkaline treated, acetylated treated of calotropis gigantean (Fig. 5) and flax fibre along with PLA and its synthetic biodegradable formulation mixture as matrix.

(a)

(b)

(c) Figure: 5 Calotropis Gigantea Fibre Composites (a) Untreated,(b) NaOH Treated (c) Acetylated

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T.Karthik & P.Ganesan

Composite Testing Tensile Testing The results of tensile testing of calotropis and flax fibre composites are shown in Table 6 and Fig.6.

Table: 6 Tensile Strength of Calotropis and Flax Fibre Composites Tensile Strength (MPa) Material

Calotropis

Flax

32

34.9

NaOH treated

35.07

37.2

Acetylated fiber

36.26

38.25

Raw fiber

Two different surface modification methods (alkalization and acetylation) were applied on the extracted fibre. Alkali treatment removes hemicelluloses, lignin from the fibre and became more thermally stable than untreated fibres. Acetylation treatment on alkali treated fibres caused further purification on the removal of hemicelluloses, lignin components from the fibre and the chemical treatment also increases the fibre individualization (fibrillation).

Fig: 6 Tensile Properties of composites From the table we are able to determine the tensile strength of composites were found to increase with increasing degree of surface modification up to some extent and then decreased with further increasing degree of chemical concentration. The increase in tensile strength could be due to the more fibre-matrix interfacial strength because of the modified fibre surface and increased surface free energy which shows increased tensile strength of composites. It shows that the alkali treated and acetylated composites have higher tensile strength of about 9% and 12% compared to untreated fibre composites respectively for calotropis gigantea fibre composites and about 6% and 9% for flax fibre composites.

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

Flexural Testing Flexural properties of untreated and treated fibre composites are shown in Table 7 and Figure 7 Table: 7 Flexural strength of Calotropis and Flax Fibre Composites

Flexural Strength (MPa) Material

Calotropis

Flax

Raw fiber

49.238

83.635

NaOH treated

52.435

85.241

Acetylated fiber

53.841

89.235

Flexural testing gives a positive study into the structural comparison of the fibre structure.

Chemical treatment changes the amorphous regions and arrests the random movement of the fibrous structure improving the elastic nature of the fibre. The improvement of flexural properties of treated fibre composites is likely to be due to removal of outer surface. The possible reason for this improvement is the alkalization helps to improve fibres hydrophobicity by removing hemicelluloses, lignin and other cellulosic matters from the fibre. As a result compatibility between the fibre and resin were improved which resulted superior mechanical properties. It shows that the alkali treated and acetylated composites have higher flexural strength of about 6% and 8.5% compared to untreated fibre composites respectively for calotropis gigantea fibre composites and about 2% and 6% for flax fibre composites. There is also fibrillation and diameter reduction of fibre due to acetylation that may have influence on modulus properties of composites. The flexural strength of flax composites are much higher than the calotropis gigantean composites as shown in Fig. 7.

Fig: 7 Flexural strength of composites

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T.Karthik & P.Ganesan

Impact Testing Impact properties of untreated and treated fibre composites are shown in Table 8 and Figure 8.

Table: 8 Impact strength of Calotropis and Flax Fibre Composites

Energy (Joule) Material Raw fiber NaOH treated Acetylated fiber

Calotropis

Flax

0.895

0.909

807

0.826

0.797

0.813

The impact strength of a composite is usually influenced by many factors, including the toughness properties of the reinforcement, the nature of interfacial region and frictional work involved in pulling out the fibre from the matrix. The nature of the interface region is of extreme importance in determining the toughness of the composite. The impact testing shows a close relationship with both raw and NaOH treated composite. It does not show much variation because the alkali treatment does not change the load distribution properties of the fibre. Impact testing gives a close value between the composites. Acetylation treatment decreases the impact strength of both calotropis and flax fibre composites .This could be may be due to the brittleness increase of fibre matrix material and local internal deformation in composite material.

Fig: 8 Impact Strength of composites From the figure 8, it is observed that the calotropis gigantea and flax composites shows more or less same impact properties. This shows that calotropis gigantea fibre can used in application where flax is used. The impact strength properties are very important for the high end industrial

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Development of Ecofriendly Textile Composites from Calotropis Gigantea Bast Fibre

applications. However chemical treatment reduces the impact strength in the composite due to surface damage. For applications preferring high impact properties it is recommended to use untreated fibre [17].

CONCLUSIONS The concept of bio-based materials is now becoming a key important factor due to the ultimate need to preserve our environment. Study into bio-composites investigated different matrix components and research conducted found that polylactic acid and its synthetic bio-degradable formulation is a ecofriendly matrix. The stem of Calotropis gigantea is a soft shrub that can grow in dry habitats and in excessively drained soils. Stems of Giant Milkweed plant can be used to obtain natural cellulose fibers with good strength and elongation. Study investigated the fiber composition and physical properties of the extracted stem fiber and found that the fiber is having properties suitable for composite application.

The composite have been fabricated using calotropis gigantea stem fiber and the resin mixture formulation of PLA using compression molding. The PLA resin mixture formulation was found to be having a good bonding strength with the calotropis gigantea stem fiber. The resin formulation is having a good adhesion property and is able to withstand high temperature. Further study in the composite manufacturing found that hydrophilic character of the fiber affects the composite durability. To improve the hydrophilic character the fiber was given chemical treatments. This research work also conducted comparative analysis of the fiber diameter and mechanical properties of raw fiber and chemically treated fiber.

From the research work, it is observed that the mechanical properties of calotropis gigantea composites are slightly inferior compared to flax fibre composites due to better fibre properties of flax. It is also clear that, the chemical treatments of fibres improved the adhesion between matrix and resin and thus improved the mechanical properties of fibres.

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