document6

Journal of Basrah Researches ((Sciences)) Volume 37. Number 3A/ 15 June ((2011))

36

Water absorption and mechanical properties of high density polyethylene/egg shell composite

Abdullah A. Hussein 1, Rusel D. Salim2 and Abdulwahab A. Sultan31Department of Material Science, Polymer Research Centre,

2 Department of Physics, College of Education, University of Basrah3 Basra Technical College

ISSN???1817???2695 ((Received 20/3/2011, Accepted 15/5/2011))

ABSTRACT: In this research, the water absorption and mechanical properties of (high-density polyethylene/egg shell) composites as a function of egg shell powder weight content in the grain size (75,125 ?m)were investigated. Polymer composite was fabricated by mixing (HDPE) with (5, 10, 15, 20, 25) wt.%of egg shell powder to obtain desirable properties. The parameters such as tensile strength, tensilemodulus, elongation at break and impact test were carried out on the prepared samples. It was foundthat the addition of egg shell powder to the polymer leads to decrease the tensile strength, modulus ofelasticity, shore-D hardness on other hand it increases the % elongation at break, and for the impactstrength. Water absorption of the composites behaviours as function of days has also beeninvestigated, and it increases by increasing exposure time for the same filler content, while theabsorbed amount of water increases, by increasing the wt.% of egg shell constant exposure time.

Keywords: HDPE, Egg shell, water absorption, Mechanical properties.

INTRODUCTION:-

A composite is a heterogeneous substanceconsisting of two or more materials which donot lose the characteristics of each component.This combination of materials brings about newdesirable properties [1]. Polymer compositesconsist of a polymer resin as the matrix, withfibers as the reinforcement medium [2].Considerable interest has been generated in themanufacture of thermoplastic composites due totheir unique properties, including their goodmechanical properties, their thermal stability,and a reduced product cost [3]. Due to thecombination of more than one material, theproperties of composites are influenced by manyfactors such as filler characteristics, fillercontent, and interfacial adhesion [4]. This cancause the behaviour of filled polymers to bemore complex than their unfilled counterpart[5]. Mechanical properties of polymericmaterials are important for nearly allapplications in industry, technology, and thehousehold. Particularly, stiffness, strength, andtoughness are decisive properties in many uses.Mechanical properties depend strongly onchemical as well as on supermolecular structure

of the polymeric material [6]. While thechemical, molecular structure defines somebasic properties such as rigidity, thermalsoftening, and melting behavior, the ultimatemechanical properties are fixed by thesupermolecular structures or morphology. Thesame molecular structure can yield to manyvaried morphologies dependent on factors suchas orientation due to fabrication, differentcooling rates, changes in thermal history, andsecondary crystallization [7].

High density polyethylene (HDPE) isan important commercial polymer which iswidely used for different engineeringapplications in modern technology [8]. HDPE isused in a variety of applications and industrieswhere excellent impact resistance, high tensilestrength, low moisture absorption, excellent lowtemperature toughness, relatively high softeningtemperatures and chemical and corrosionresistance properties are required [9]. In order toreduce the cost or enhance the physical andmechanical properties of HDPE, some additivescan be added. Fillers and reinforcement usedinclude talc, calcium carbonate, mica,

Hussein, Salim & Sultan

37

wollastonite, glass fiber, glass bead, jute, etc.[10]. Egg shell is a biomaterial containing 95% byweight of calcium carbonate in the form ofcalcite and 5% by weight of organic materials,such as (Al2O3 , SiO2 , S, Cl , Cr2O3 , MnO )[11].The generalized egg shell structure, whichvaries widely among species, is a protein matrixlined with mineral crystals, usually of a calciumcompound such as calcium carbonate[11].

It is clear that the egg shell can change themechanical properties of high densitypolyethylene, because of its nature, size, shapeand distribution. This study focused on theeffect of compositing on the water absorptionand mechanical properties of High densitypolyethylene .The optimized percentage wasidentified and its proper applications wereproposed.

EXPERIMENTAL:Materials: The material used in the study was HDPE(density =0.96 gm /cm3) supplied by the statecompany of petrochemical industries (SCPI),Basra Iraq. The egg shell powder was obtainedfrom a local market. The samples used in thisinvestigation were prepared by compressionmolding method [7].Sample preparation: First, raw material eggshells were subjectedto cleaning, dried and ground to a powder usingthe blender. A sieve was used to obtain averagegrain sizes of (75,125 ?m). The egg shellpowder was dried in an oven to eliminatecontaminants and odour. After that powder was

treated with a solution of 5% NaOH [12], it wasadded to the polymer in different weight fraction(5, 10, 15, 20, 25) wt.%. The egg shell powderas a fine powder was mixed with HDPE usingmixer 600 instrument attached to HaakeRehochard meter with following conditions;mixing time 15 min; mixing temperature 1750C ;mixing velocity 32 RPM . The final moldproduct was introduced in a laboratory compressunder 5 ton at 1750C for (2-5) minutes in asquare frame .The pressure then rises graduallyup to 15 ton for a (5) minutes and after thisperiod the sample was cooled up to reach roomtemperature .

Table (1) : The specification of HDPE and egg shell powders.Sample No. HDPE (%) Egg shell (%)

1 95 52 90 103 85 154 80 205 75 25

Characterization and measurements:Tensile tests

In order to measure the mechanicalproperties, samples with a respective shape(Dumbbell-shaped specimens) were prepared(20*20) cm2 and (2&3 mm) thickness. Tensilestrength (ASTM D638) was determined using anInstron testing machine at a crosshead speed 20cm/min and chard speed (10) cm/min. Theimpact strength (ASTM D256-87) was

determined using Charpy impact test instrument.Hardness type shore D (ASTM Test Load) wasused to measure the hardness of the polymermaterials. The average reading of samples testswere considered. The mechanical testsinstruments used for this purpose are availablein the state company of petrochemical industries(SCPI) and the University of Basra Laboratories.

Table (2): The instrument has the fallowing specificationTensile load range 0 - 2500 kgCross head speed 0.0 - 500 mm/minCross head travel 980 mm

Chart speed 10 mm/min.

Water absorption and Mechanical properties of High density polyethylene/ egg shell

38

Water Absorption Test Water absorption test (ASTM D750-95) wasdone by total immersion of three samples indistilled water at room temperature. The waterabsorption was determined by weighing thesamples at regular intervals (Weight gain). ASartorius balance in the range (0.0001-200 gm) .

The percentage of water absorption (M %), wascalculated by [12]:

W (%) = [(W2-W1)/W1]*100% (1)

where W1 and W2 are the dry and wet weights,respectively.

Results and Discussions: Figure 1 shows the tensile strength as afunction of filler content. It is observed that thetensile strength for the composites decreaseswith increasing filler content. The decreases intensile strength are due to the poor adhesion ofthe filler-matrix and the agglomeration of fillerparticles. The strength of particulate-filledpolymer composites depends, to a great extent,on the interfacial adhesion between the matrixand the filler which will facilitate the transfer ofa small section of stress to the filler particleduring deformation [13]. The tensile modulus can be calculated fromthe slope of linear region for stress strain curveusing tensile test. Figure 2 shows the tensilemodulus as a function of filler content. Thetensile modulus varied between 450 to 340 foregg shell weight ratio between 5 to 25%respectively. This decrement in tensile moduluscan refer to increase the resistance of material todeformation. The increased moduluscorresponds to more filler where its intrinsicproperties as a request agent exhibit highstiffness (modulus) compared to polymericmaterial [14]. This is because at a high fillerloading, the composite will be able to withstandgreater loads [15].

The effect of egg shell on the elongation atbreak of HDPE is shown in Figure 3.From thisfigure It can be seen that, the elongation at thebreak for the composites increasing withincreasing filler content because the addition ofegg shell powder causes an increase in theelasticity which leads to reduce the strength ofthe material. Increase of the elongation breakwith the increasing filler loading indicates thecapability of the filler to support the stresstransfer from polymer filler to matrix [16].

Figure 4 shows the Impact strength as afunction of filler content. As expected, theaddition of the egg shell increased the stiffnessof the HDPE gradually with increasing filler

content. This increase in impact strength mayrelate to the fact that when egg shell powder isadded to polymer it acts like a solid"Plasticizer", therefore the flexibility of thepolymer increases and its ability to absorb anddissipate energy increases, so the polymer needshigh impact energy to fracture. From the result itcan be concluded that HDPE / egg shell powdercomposite exhibit synergistic improvement inimpact strength, the synergy might be explainedby the fine dispersion of the second component(egg shell) achieved due to a good viscositymatch with HDPE [17].

Figure 5 shows the effect of filler content onthe (Shore-D Hardness) of egg shell powderfilled HDPE composites. It is obvious that,Shore-D Hardness decreases with increasingfiller content. This may be attributed to the factthat the hardness is generally considered to be aproperty of the surface therefore this behaviourof hardness is expected [18]. The addition of theegg shell leads to an increase in the elasticityand a decrease in the matrix surface resistance tothe indentation [19]. Figure 6 (a&b) show the variation of ratio ofwater absorption versus exposure time for(HDPE / egg shell powder) composite withdifferent fillers content and grain size (75,125?m). It can be seen from the figure that, thecomposites with higher filler content show morewater absorption. This is due to the highercontents of filler content in the composites thatcan absorb more water. As the filler contentincreases, the formation of agglomerationsincreases due to the difficulties of achieving ahomogeneous dispersion of filler at high fillercontent. The agglomeration of the filler incomposites increases the water absorption of thecomposites. The figures also show that the ratioof water absorption by grain size (75?m) washigher than for grain size (125 ?m) for all fillerscontent, because of the surface area [20].


39

CONCLUSION The addition of egg shell filler has resulted insome improvement in the mechanical propertiesof HDPE. The tensile strength, modulus ofelasticity and shore-D hardness elongation atbreak of (HDPE / egg shell powder) compositewere slightly reduced with the incorporation of

the filler. Elongation at break and the impactstrength increase gradually with increasing fillercontent. Water absorption of the compositesbehaviours as function of days has also beeninvestigated.

0 5 10 15 20 250

10

20

30

40

50

60

70

tens

ile s

tren

gth(

Mpa

)

wt.% Filler

PURE 75?m 125?m

Figure 1: Effect of filler content on the tensile strength of (HDPE /egg shell) composites.

0 5 10 15 20 250

50

100

150

200

250

300

350

400

450

500

Tens

ile m

odul

us (M

pa)

wt.% filler

PURE 75?m 125?m

Figure 2: Effect of filler content on the tensile modulus of (HDPE /egg shell) composites.


40

0 5 10 15 20 250

100

200

300

400

Elon

gatio

n at

bre

ak (%

)

wt.% filler

PURE 75?m 125?m

Figure 3: Effect of filler content on the Elongation (%) of (HDPE /egg shell) composites.

0 5 10 15 20 250.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

Impa

ct s

tren

gth

(J/m

m2 )

wt.% filler

PURE 75?m 125?m

Figure 4: Effect of filler content on the Impact strength of (HDPE /egg shell)) composites.


41

0 5 10 15 20 250

1

2

3

4

5

6

7

Shor

e D

Har

dnes

s

wt.% filler

PURE 75?m 125?m

Figure 5: Effect of filler content on (Shore-D) Hardness of (HDPE /egg shell) composites.

1 2 3 4 5 6-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

(a)75?m

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

wat

er a

bsor

ptio

n (%

)

exposure time (days)1 2 3 4 5 6

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07(b)

125?m0%5%10%15%20%25%

wat

er a

bsor

ptio

n (%

)

exposure time (days)

Figure 6: Effect of exposure time on the water absorption of (HDPE /egg shell) composites with differentfiller content (a) 75?m and (b) 125 ?m.

References:[1] D. Stauffer, "Introduction to percolation

theory". Taylor and Francis, London(1985).

[2] J. A. Brydson, "Plastics materials" , seventhedition, Butterworth- Heinemann, (1999). [3]E. Riando, " Electric Properties of Polymer",Marcel Dekker, Inc, (2004).

[4] W. A. S. Abdul Ghafor, "Ph.D. Thesis,University of Basrah ", Basrah , Iraq, (1996).[5] H. R. Kricheldorf, O. Nuyken and G. Swift"

Hand book of Polymer Synthesis, SecondEdition", Marcel Dekker, (2005).

[6] L.H. Sperling, " INTRODUCTION TOPHYSICAL POLYMER SCIENCE", A


42

JOHN WILEY & SONS, INC.PUBLICATION, (2006).[7] M. F. Ashby, "Materials selection inmechanical design, Second education ", MichaelF. Ashby (1999).[8] E. J. F. Shackelford and W. Alexander,

"Materials Science and EngineeringHandbook ", Boca Raton: CRC PressLLC, (2001).

[9] H.Q.PHA and M. J. MARKS, "Encyclopedia of polymer science andtechnology" a division of J. Wily and sons,Inc ,New York, 9, (2002).

[10] S.M. Zebarjad a,*, S.A. Sajjadi a, M.Tahani b, A. Lazzeri, " J. Achiev. in Mat.Manuf. Eng. ", 17 , (2006).

[11] . L. Arias, R. Quijada, M. Yazdani-Pedram,P. Toro.," Patent Appl. US", Universidadde Chile, invs. J, 2006-068185-A1,(2006).

[12] S.Shuhadah, M., Supri, A.G. &Kamaruddin, H. (2008). Thermal analysis, waterabsorption and morphology properties of egg-shell powder filled low density polyethylene

composites. Proceeding of MUCET 2008,UniMAP, Kangar, Perlis, 1516 (2008).[13] Dorsherman, David Brandon, "Mechanical

Properties of hard materials and theirrelation to microstructure", Advancedengineering material, 1, 1999.

[14] C. W.Shyang," Malay. Polym. J".l (MPJ),Vol 3, No. 1, p 1-13, (2008).

[15] C.T. Ratnam*1, Radin Siti Fazlina2 andShuhaily Shamsuddin, Malay. Polym. J, l. 5, 1,17-25, (2010).[16] H. R. Kricheldorf, O. Nuyken and G.

Swift" Hand book of Polymer Synthesis,Second Edition", Marcel Dekker, (2005).

[17] N.J.Saleh and Nabeela A. Mohammed,"Eng. & Tech.", 27, 9, (2009).

[18] M T,Malik,Property stabilization in filled,drawn polyethylene ,43, 3, 543-551,(1991).

[19] N. .J.saleh and Z.Y.shnean," Eng. &Tech.", Vol. 26, No.9, (2008).

[20] S.Shuhadah* and A.G. Supri, "J. Phys.Sci.,Vol. 20(1), 8798, (2009).

?????????????????????????????????? ???????????????????????????????????????? /??????????

??????: ?????????????????????????????????????????????????? ??????????? ?????????? ???????????????????????????? ???????

????????????????????????(75,125 ?m) . ??????????????????????????????????????? ??????????????????????(5%,10%,15%,20%,25%)????????????????????????????????????? .????????????????????????????????????????

?????????????????????????????)??????????????????????????????????????????????????????? .( ??????????????? ??????????????????????????????????????????????? ????????????????????????? ??????????? .??????????????????????????

?????????????????????????? ?????????????????? . ???????????????????????????????????????????????????????????????.???????????????????????????????????????????????????????????????????????????????????????????????????)?????????? (????????

???????????????????????????????????.

document6

Documents