PREPARATION OF LDPE-BLEACHED & GRAFTED PULQUE

FIBER COMPOSITE AND ITS PHYSICOCHEMICAL PROPERTIES

Shamim-Ara Pervin, Ayesha Akther Zaman and M. Maniruzzaman Department Applied Chemistry and Chemical Technology

Islamic University, Kushtia # 7003, Bangladesh

Submitted to Indian Journal of Fibre and Textile Research

Manuscript: Regular Articles

*To whom correspondence should be addressed.

Dr. M. Maniruzzaman

Associate Professor Department Applied Chemistry and Chemical Technology Islamic University, Kushtia # 7003, Bangladesh Tel: +880-71-53029 Ext. 2455 Fax: +880-71-54400 e-mail:manir@kushtia.com

PREPARATION OF LDPE-BLEACHED & GRAFTED PULQUE FIBER COMPOSITE AND DEETEMINATION OF ITS PHYSICOCHEMICAL

PROPERTIES

SHAMIM-ARA PERVIN, M. MANIRUZZAMAN, Department of Applied Chemistry and Chemical Technology, Islamic

University, Kushtia-7003, Bangladesh ABSTRACT A simple hot press molding process was used to produce LDPE-Pulque fiber reinforced composites using LDPE (Low density polyethylene) and Pulque fiber (raw, bleached and grafted with HEMA) varying the amount of fiber and LDPE. Various physical and mechanical properties were measured. The physical properties i.e., density is higher for composites of grafted fiber than that of raw and bleached fiber. Water absorption and moisture content are higher for composites of bleached fiber. The tensile properties i.e., stress-strain curve and UTS are high for composites of bleached fiber and increase with fiber addition to a maximum then decreases or remains more or less constant. The flexural properties ( flexural strength, tangent modulus and flexural strain) of composites of bleached fiber is higher than that of raw and grafted fiber composites and these properties increase with the increase of fiber content to a maximum and then decrease or remains fairly constant. INTRODUCTION Materials property combinations and ranges have been, and are being, extended by the development of composite materials. . Composite materials represent nothing but a giant step in the ever-constant endeavor of optimization in materials. Strictly speaking, the idea of the composite is not a new or recent one. Nature is full of example wherein the idea of composite is used. The coconut, plum leaf is nothing but a cantilever using the concept of fiber reinforcement. Wood is fibrous composite; cellulose fiber in lignin matrix. The cellulose fibers have high tensile strength but are very flexible. While the lignin matrix joins the fiber furnishes the stiffness. Natural fibers are a promising reinforcement to use in thermoplastic composites due to their low density and excellent mechanical properties. Further more the natural fibers such as sisal, jute hemp and flax are relatively cheap and obtained from renewable resources.1 For the manufacturing of reinforced composite materials, factors such as fiber content, fiber diameter, fiber length, void content matrix properties,

fiber-matrix bonding, fiber orientation and fiber properties are very important as they determine the final properties of the natural fiber reinforced composite components.2Composite is used to facilitate the use of its constituent materials. Main constituent of our composite is LDPE (Low density polyethylene) with the addition of chemically modified sisal fiber composite, which is strong and improved in quality than LDPE. The composite may be used as roofing materials, as well as for partition and other commercial and domestic uses.2 Incorporation with a natural fiber (sisal fiber), the polymeric matrix LDPE made our sample product. Heat and press molding process was used which is a very low cost process than the other process for fabrication of composite. Here the temperature and pressure are the two main parameters for the fabrication and the others are cooling time, additional pressure and retention time. Here the main drawback is consumption of long time. The density of sisal fiber is greater than matrix. Through changing the parameters of the fabrication, optimum condition for operation was decided, for the desired composite product. The intention of this thesis work is to achieve a natural fiber reinforced composite with high mechanical properties using chemically modified short Agave Atroverance fiber as reinforcement and a Low density Poly Ethylene (LDPE) as a polymer matrix.3 Experimental For composite preparation the chief raw materials used are LDPE, collected from local market and Agave Atroverance, are collected from rural area.Untreated (raw) light brown Agave Atroverance fiber, bleached pulque fiber and 2-Hydroxy ethylmethacrylate (HEMA) modified or grafted pulque fibers were used as reinforcement agent. In the thesis work no coupling agent is used. The samples were prepared by several steps such as pulque fiber cutting (to get sized pulque bundles were cut into different length of 2-3 mm, average, with its help of a knife) the sized pulque were manually agitated to make the pulque fiber loose with each other. This pulque kept at a dry environment for seven days for the partial removal of moisture. The samples were prepared by mixing, casting, curing and controlling, cooling and demolding. To evaluate the properties of prepared composite the following tests are performed –

1. Measurement of bulk density 2. Water intake/Water absorption

3. Tensile strength testing 4. Flexural testing

The samples were prepared by Weber Pressen Hydraulic Press Machine and the samples were tested by UTM Machine (Hounsfield test equipment). Bulk Density Calculation:4 D = Ws / V Where, D = Density of the specimen, Kg/m3

Ws = Weight of the specimen, Kg, and V = Volume of the specimen, m3.

Water absorption /Water in take:5 The total water absorption was calculated following the rules given below. 1. Increase in weight, %Wi = Ww-Wc ÷Wc×100 2. Soluble matter lost, %Ws = Wc-Wrc ÷Wc×100 3. % water absorbed, W= Wi + Ws In all cases a protective gel coat (araldite) was applied on the cut sides to prevent penetretion of water from cut sides.

Tensile Strength (i): Tensile specimen was prepared according to ASTM Method.

The test speed was 1mm/min.

Tensile Strength6 = Applied load

Cross sectional area of the load bearing area

6 = PA

= PA .

KNmm2

= 103 PA .

Nmm2

= 103 PA .

N10-6m2

= 103 PA .

Nm2 X 106

= 103 PA . Pa X 106

= 103 PA . M Pa

Tensile strain (ii): Tensile strain is calculated according to ASTM D-638M - 91a. Tensile strain = Flexural Strength7 (i): Flexural specimen was prepared according to ASTM D790M, 3 point loading. The specimen dimension was 125 x 10 x 6-8 mm and support span was 96 mm. The test speed was taken as 2 mm/min. The strength may be calculated for any point of the load deflection by means of the following equation- S = 3PL / 2BD2

Where, S = stress in the outer fibers at midspan, MPa, P = load at a given point on the load – deflection curve, N, L = support span, mm, B = width of specimen tested, mm, D = depth of tested specimen, mm. In this way the flexural strength of each sample is measured Flexural Strain (ii): Flexural specimen was prepared according to ASTM D790M, 3 point loading. The specimen dimension was 125 x 10 x 6-8 mm and support span was 96 mm. The test speed was taken as 2 mm/min. It may be able to be calculated for any deflection using the following equation-

fε = 6Dd / L2

Where,

fε = Main strain in the outer surface, mm/mm D = Maximum deflection of the center of the beam, mm L = Support span, mm. d = Depth, mm. Tangent Modulus (iii): To determine the Tangent Modulus at first the slope is calculated from the load deflection curve. If Sloe = K

Extension 25

Span = L Width = b Thickness =D Tangent Modulus = KL3/4bD3

Results and Discussion Physical Properties:

0.80.820.840.860.880.9

0.920.940.960.98

1

0 5 10 15 20 25

Fiber Content/%

Den

sity/

gm/c

c

GraftedBleachedRaw

Fig. 1: Effect of fiber addition on density for LDPE-pulque or Agave atroverance fiber composite for raw, bleached and grafted fiber.

Figure 1 shows the effect of fiber addition on density for LDPE-pulque fiber composite for different types of fiber as mentioned above. The curve shows that the density increases with the fiber addition and it increases up to 20% of fiber addition. It is seen that the density is high for grafted fiber and lower for raw fiber and the bleached fiber attain the medium value.

The relationships derived for different fiber are:

Density = 0.92+0.0001(% of raw fiber), Density = 0.92+0.0002(% of bleached fiber) Density = 0.92+0.0014 (% of grafted fiber)

Grafted fiber shows highest slope and raw fiber shows the lowest slope. From the data it is concluded that the slope is high for grafted fiber than for bleached and raw fiber.

0

5

10

15

0 100 200 300 400

Time/hrs

Wat

er A

bsor

ptio

n/%

GraftedBleachedRaw

Fig. 2 : Effect of immersion time on Water Absorption (WA) of LDPE-various types of such as raw, bleached and grafted Agave atroverance (pulque) fiber reinforced composites for 20 % of fiber addition.

Fig. 2 shows the effect of immersion time on water absorption of raw, bleached and grafted or 2-Hydroxy ethyl methacrylate(HEMA) modified fiber reinforced LDPE composites for 20% of fiber addition. It reveals that the water absorption depends on fiber addition and immersion of time. It can be seen that the percentage of water absorption for all percent of fiber addition increases with time as it is a diffusion phenomenon. Water absorption is responsible only for fiber addition and higher the fiber addition higher will be the water intake .The figure shows that the % of water absorption increases initially slowly and with increases of time it increases rapidly. The figure shows that the % of water absorption is high for grafted fiber, medium for bleached fiber and low for raw fiber.

Mechanical properties : Tensile Properties: The tensile properties of a material shown by the stress-strain curve.

0

2

4

6

8

10

12

14

0 0.2 0.4 0.6

Strain/mm/mm

Stre

ss/M

pa

5% fiber10% fiber20% fiber

Fig.1: Stress-strain curve(Tensile) for LDPE-raw Agave atroverance (pulque) fiber composite (% of fiber loading).

0

2

4

6

8

10

12

14

0 0.1 0.2 0.3 0.4 0.5

Strain/mm/mm

Stre

ss/M

pa

5% fiber

10% fiber

20% fiber

15% fiber

Fig.2: Stress-strain curve for LDPE-bleached Agave Atroverance (pulque) fiber composite (% of fiber loading).

0

2

4

6

8

10

12

14

0 0.1 0.2 0.3 0.4 0.5

Strain/mm/mm

Stre

ss/M

pa

5% fiber

10% fiber

15% fiber

Fig.3: Stress-strain curve(Tensile) for LDPE- grafted or 2-Hydroxy ethyl methacrylate (HEMA) modified Agave atroverance (pulque) fiber composite (% of fiber loading). Figure 1,2 and 3 shows the Stress-strain curve(Tensile) for LDPE-raw, bleached and grafted pulque fiber composite (% of fiber loading). The tensile properties of a material are shown by stress-strain curve. Here stress increases with the increase of strain. It reaches maximum and after that the stress falls down. The curves have two regions- one is the elastic region and another is plastic region. Initial region is the elastic region and after that samples deform plastic area. The figure shows that higher the percentages of fiber loading higher the maximum stresses (UTS) and lower the strain. That is with the increase of fiber addition the maximum stress (UTS) increases but ductility of composite decreases. UTS (Ultimate Tensile Strength):The strength of a material is the tensile stress under which it ruptures.

0

2

4

6

8

10

12

0% 5% 10% 15% 20% 25%Fiber Content/%

UTS

(MPa

)

RawBleachedGrafted

Fig.4: Effect of fiber addition on Ultimate Tensile Strength for LDPE- raw, bleached and grafted Agave atroverance (pulque) fiber reinforced composite. Figure 4 shows the effect of fiber addition on Ultimate Tensile Strength for LDPE- raw, bleached and grafted pulque fiber reinforced composite. Here the curves shows that the tensile strength is maximum at every treatment for 10% loaded fiber composite. But untreated fiber shows that the tensile strength decreases with the fiber loading. Ultimate tensile strength is higher for LDPE-bleached pulque fiber reinforced composite because of better bonding between fiber and matrix. For grafted fiber composite the strength is less than bleached fiber but higher than raw fiber. It means that the fiber matrix bonding increases for bleached fiber and simultaneously for grafted fiber and treated fiber matrix bonding is much better than raw one. Flexural Properties: The stress required to rupture a material under flexure is its flexural strength.

0

2

4

6

8

10

0% 5% 10% 15% 20% 25%

Fiber Content/%

Flex

ural

Stre

ngth

/MPa

Grafted

Bleached

Raw

Fig.1: Effect of fiber addition on Flexural Strength for LDPE-raw, bleaced and grafted Agave atroverance fiber reinforced composite. Figure 1 shows the effect of fiber addition on Flexural Strength for LDPE-raw, bleached and grafted pulque fiber reinforced composite. It reveals that the flexural strength increases with the increase of fiber addition up to certain percentage of addition fiber (10%), the strength is always higher for bleached than that for raw and grafted fiber. For 0% fiber the polymer strength was obtained 6.92 MPa. Up to 10% fiber addition both the fiber and matrix bear the load and make resistance to slip as in the case of age hardening of metals. Up to 10% the short fibers are finely distributed and the interfacial bonding between the fiber and matrix is high, after that fibers are present as bundle of fibers and fiber-fiber bonding strength is lesser and the interfacial bonding between the fiber and matrix is poor. After that the fiber are coagulated as bundle of fibers, bundle of fibers fractured during load to slips and does not make resistance to slips. Moreover, these also act as stress concentrator. Consequently, after 10% fiber addition the flexural strength decreases. Similar effect was found by Rashed and Rizvi8, Shabname Ele9,Bipasha Bose10 Asad 11.

0

2

4

6

8

0% 5% 10% 15% 20% 25%

Fiber Content/%

Flex

ural

Stra

in/m

m/m

m

RawBleachedGrafted

Fig.2: Effect of fiber addition on flexural strain for LDPE-raw, bleached and grafted Agave atroverance (pulque) fiber reinforced composite. The effect of fiber addition on flexural strain of LDPE-raw, bleached and grafted pulque fiber reinforced composites is shown in figure2. It reveals that the flexural strain of fabricated product decreases continuously with the increase of fiber addition. It is apparent that the elongation decreases very slightly with the increasing of fiber content. The presence of fiber restricts the slip resulting in lesser ductility and consequently the % of elongation decreases continuously with the increase of fiber addition. Strain is lesser for bleached fiber than that for raw and grafted fiber. Similar effect was found by Shabname Ele9, Asad 11. Conclusions

Our research work was conducted to make this type of (house wares, toys, and containers, lids, and closures, power coating, pipe, window and door, roofing in the developing countries, automobiles body etc.) high performance application materials, from low-density polyethylene and polypropylene reinforced with Agave Atroverance fiber. One of the most important objectives of our research work is to use Agave atroverance fibre, which is biodegradable. So, a definite amount of low-density polyethylene and polypropylene could be replaced by the Agave Atroverance fiber, which is very important to our environment. After use of the product manufacture by LDPE and pp reinforced by natural fiber rotten a certain percentage when goes to the environment. So, in the respect of our risky environment, it is suitable to use this type of composite materials, produced with polymer, which is reinforced by natural fibers such as Agave Atroverance. From this experiment it is concluded that the tensile and flexural properties of bleached pulque fiber composite is higher than that of raw and grafted fiber composite.

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7. ASTM (Reapproved 1991), Designation; F 417-78, Standard Test Method For Flexural Strength (Modulus Of Rupture) Of Electronic- Grade Ceramics.

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