Engineering, Technology & Applied Science Research Vol. 8, No. 2, 2018, 2814-2817 2814 www.etasr.com Alghamdi: Synthesis and Mechanical Characterization of High Density Polyethylene/Graphene … Synthesis and Mechanical Characterization of High Density Polyethylene/Graphene Nanocomposites Abdulaziz S. Alghamdi Mechanical Engineering Department College of Engineering, University of Hail Hail, Saudi Arabia asbg945@hotmail.com Abstract—The purpose of this work is to investigate the effects of graphene nanosheets (GNSs) addition on the mechanical and thermal properties of high density polyethylene (HDPE). The HDPE/Graphene nanocomposites were synthesized using solution blending approach. HDPE was incorporated with graphene nanosheets in a solvent at various weights of fractions (0.1, 0.2, 0.4 and 0.5 wt%), and then the micro-hardness, elastic modulus, tensile strength, strain at break and thermal properties of the nanocomposites were measured and compared. The results showed that the use of Xylene solvent at high temperature combined with mechanical stirring can fully dissolve HDPE pellets. Scanning electron microscope (SEM) showed that GNSs were homogenously dispersed in the polyethylene matrix at low weights of fractions. The addition of just 0.2 wt% GNSs resulted in 100% increase in the micro-hardness value. The elastic modulus and tensile strength properties are proportionally increased with increasing GNSs content up to 0.4 wt%. However, at higher weight of fraction, a reduction in these properties is observed. The crystallinity and strain at break properties are reduced with the addition of GNSs. Keywords-HDPE; polymer; graphene; nanocomposite; thermal; mechanical I. INTRODUCTION Polymer-based nanocomposites of current academic interest are finding an increasing range of industrial applications, making them the most widely commercialised class of nanocomposites [1]. The incorporation of low weight of fraction of nanoparticles or nanosheets can lead to a significant improvement in the polymer properties like tensile strength, elastic modulus, wear and scratch resistance, electrical and thermal conductivity, thermal and flammability resistance and impact strength [2-5]. In addition, many polymer nanocomposites can be fabricated and processed by the use of methods similar to those used for standard polymers, which is important from an economic point of view. In recent years, researchers have focussed on the synthesis of new nanocomposites, starting from careful material selection and process control either by the direct use of an existing technique or by modified and adapted techniques. Various types of nanofillers have been used in polymer-based nanocomposite fabrication, such as exfoliated clay, modified carbon nanotubes and graphene [6-15]. However, achieving the uniform dispersion of the nanofillers is still an important scientific and technological challenge in nanocomposite fabrication. Graphene nanosheets, with their outstanding thermal, electrical, optical, and mechanical properties as well as their low cost compared to carbon nanotubes can be a cost-effective alternative to carbon nanotubes and can be widely used for the fabrication of polymeric nanocomposites [16-18]. Graphene nanosheets are relatively easier to disperse homogeneously in the neat polymer matrix compared to carbon nanotubes and possess a higher surface area to volume ratio that improves bonding and load transfer properties, and consequently increases the strength [19-21]. High-density polyethylene (HDPE) is a thermoplastic polymer that can be blended with different reinforcement materials to further enhance its overall properties like strength and thermal properties [16, 21, 22]. The mechanical, thermal, electrical and surface hydrophobic properties of HDPE can be improved with the addition of 1 to 8 wt% graphene nanoflakes to the matrix using solution blending [16]. However, using large quantities of graphene nanosheets can increase the production cost. Therefore, in this research, small quantities of graphene nanosheets (0.1-0.5 wt%) were incorporated with HDPE in a proper solvent, and then the mechanical and thermal properties of the resultant nanocomposites were determined using various techniques. II. EXPERIMENTAL WORK A. Materials The polymer-based nanocomposite presented in this work is high density polyethylene (HDPE) with the addition of graphene nanosheets (GNSs) at various weight percentages (0.1, 0.2, 0.4 and 0.5 wt% GNSs). HDPE pellets were purchased from SABIC Company, Saudi Arabia in 2016. Graphene nanosheets were purchased from Graphene Laboratories Inc., USA, with average thickness<3nm (between 3-8 graphene monolayers) and lateral dimensions 2-8 microns. B. Processing An in-house solution blending technique was used to perform a well dispersed GNSs into the HDPE matrix. Graphene nanosheets were dispersed in alcohol using sonicator for 30 minutes. Then, the mixture was dried for 24 hours. GNSs were dispersed again in Xylene for 30 min using son dis and hot app dri pla usi pre Wa tes C. usi Mi Co (U ana of hea ma the the car Ins tem 1m tem +1 Ex per ind and A. cal see po add wit add nan B. com of po roo Ho fas sho nan hom Ho agg Engineer www.etasr nication, and spersions. In o d the dispersio t plate at 130 plied simultan ied for 24 hou aced in a squ ing furnace t essed using h ater was used st specimens w Mechanical T The morpho ing a Philip icroscope-Fiel ompany (Eindh USA). DSC, (T alyze the effe HDPE. The s ated from 35 ass fraction of e heat of fusio e equilibrium rried out using stron Corpor mperature (22± mm/s. FLIR ca mperature distr 50C and acc xcel to study th rformed using denter (Vicker d average was I Thermal Ana Figure 2 an lorimetry resu en that the ad ints. However dition of 0.1 th the increa dition of GN nocomposites. Graphene Na The use of X mbined with m HDPE in a lyethylene ma om temperatu owever, the ap ster dissolving ows the SEM nocomposites. mogenously in owever, at 0.5 gregations of ring, Technolog r.com then HDPE order to improv on of GNSs, a 0C and mec neously for 2 h urs at 150C. uare steel mou o 220°C for hydraulic pres d to cool the m were cut to the Testing and C ology of the n ps XL30 Env ld Emission hoven, The N TA instrument ct of GNSs ad specimens we to 200°C at f crystallinity on with that fo melting point g an Instron 5 ration (Norw ±2ºC). The sp amera was use ribution, with curacy of ±1C he material be g force of 1 rs test), the in s taken. III. RESULT alysis nd Table I p ults for HDPE ddition of GN r the crystallin wt% graphen ase of graphe NSs has no ef . anosheets Disp Xylene as chem mechanical sti short period aterials, large ure combine pplication of g as well as le images for the . It can be n the HDPE m 5 wt% graphe graphene nan gy & Applied Sc Algh E pellets wer ve the dissolvi and also reduc hanical stirrer hours. Then, th The nanocom uld (100×100 30 min. The ss machine at mould to room dimensions sh Characterizatio nanocomposite vironmental Gun (ESEM Netherlands) an ts, Shimadzu D ddition on the re sealed in a a rate of 10° is then determ or fully crystal t (290kJ/Kg). 5969 tensile te wood, MA, peed rate used d to measure t temperature r C. All results ehavior. Micro 100g for 5 s ndentation wa TS AND DISCUS present the di and its nanoco NSs has no eff nity is reduce ne. Further red ene percentag ffect on the persion mical solvent rring resulted d of time. U quantities of s d with high specific temp ess quantity of e microstructu seen that GN matrix up to 0. ene, some ca nosheets can cience Researc hamdi: Synthesi re added int ing of HDPE p ce the time ne r at 100r.p.m he dispersions mposite materia ×1mm) and h en, the mould t 7MPa for 1 m temperature hown in Figure on. es was invest Scanning Ele M-FEG) from nd FEI Quant Dsc60) was u e thermal prop aluminium pan °C per minute mined by comp line polyethyl Tensile tests esting machine USA) at d in this work the sample's su range from -20 were plotted ohardness tests econds with as repeated 5 SION ifferential sca omposites. It c ffect on the m ed by 14% wi duction is occ ge. However, crystallinity o at high tempe in 100% disso Usually, to dis solvents are u h speed agit perature can le f solvents. Fig ure of HDPE a NSs are disp 4 wt% of grap avitations and be observed ch V is and Mechani to the pellets eeded, m were s were al was heated d was 10min. e. The e 1. tigated ectron m FEI ta 250 sed to perties ns and e. The paring lene at s were e from room k was urface 0C to using s were sharp times anning can be melting ith the curred more of the erature olving ssolve used at tation. ead to gure 3 and its persed phene. large in the mic volu cap Fig. wt% HDP nano Vol. 8, No. 2, 20 ical Characteri crostructure. T ume ratio an pacity between TABLE I. THE Materials HDPE HDPE-0.1 wt G HDPE-0.2 wt G HDPE-0.4 wt G HDPE-0.5 wt G F Fig. 2. 3. SEM imag % graphene (c) HD PE-0.5 wt% gra osheets or agglom 18, 2814-2817 ization of High This can lead nd consequen n graphene and ERMAL PROPERTIE s Cry E Graphene Graphene Graphene Graphene ig. 1. Dimens DSC results for H ges for the micros DPE-0.2 wt% gra aphene (the arrow meration) Density Polyet to reduction ntly reduction d HDPE matrix ES OF HDPE BASED ystallinity % 59.22 50.97 43.02 43.67 44.54 sions of the specim HDPE and its nan structure of (a) H aphene (d) HDPE ws indicate the 2815 thylene/Graphe in surface ar of load car x. D NANOCOMPOSIT Melting Point ( 136.76 134.78 136.52 136.39 133.57 men nocomposites HDPE and (b) HDP E-0.4 wt% graphe presence of gra ene … rea to rrying TES C) PE-0.1 ene (e) aphene C. 0.2 val ma nan attr ma ho res we the red D. gen me res nan gen me ma rea pro pla the It sig 0.2 red occ the inc 0.4 ela Th wh con the Engineer www.etasr Microhardne It can be see 2 wt% resulted lues. The emb atrix almost nocomposites ributed to the atrix and the g sting material sulted in a red ere almost sim e existence o duction in the Fig. 4. Eff Tensile Test During the neration durin echanical pro searches [6, 7 nofillers in th neration durin easured to av aximum tempe ached 35˚C, w operties. Ther astic deformat e effect of GN can be seen gnificant reduc 2 wt% of GN duction in the curs with the e elastic mod creased with in 4 wt%. At 0.5 astic modulus his is probably hich affected nsequently the e tensile load. ring, Technolog r.com ess Results en from Figur d in a significa bedding of jus doubled the comparing e well dispers good interactio l. Increasing t duction in the milar the neat m of nanoplatele surface to volu ffect of GNSs add Results tensile test ng plastic defo operties of 7, 10] provide he polyethylen ng plastic def void such in erature generat which has no s refore, the ef tion is neglect Ss addition on that the prese ction in the st NSs into the e strain at bra addition of 0.5 dulus and ten ncrease of the 5 wt% GNSs, and tensile str y due to the pr the surface e stress distri gy & Applied Sc Algh re 4 that the a ant increase in st 0.2 wt% GN micro-hardne to pure HD sion of GNSs on between the the weight of e micro-hardne material. This ts aggregates ume ratio. dition on the micro ting, the ph ormation can p polymeric d evidence th ne matrix can formation. Th nfluences. It ted during the significant effe ffect of heat ted in this wo n the percentag ence of these train at break. HDPE matri ake. More red 5 wt% GNSs. nsile strength weight percen a reduction i rength values resence of GN e area to v ibution during cience Researc hamdi: Synthesi addition of GN n the micro-har NSs into the H ess values o DPE. This ca s into the po e nanosheets an f fraction of ess values and s is probably d and therefor o-hardness values henomena of potentially affe materials. S hat the existen n increase the herefore the h is found tha plastic deform fects on the ma generation d ork. Figure 5 s ge of strain at b nanofillers c The embeddi ix resulted in duction up to On the other of the HDP ntage of GNSs is observed in as seen in Fig NSs agglomera volume ration g the applicati ch V is and Mechani NSs to rdness HDPE of the an be olymer nd the GNSs d they due to re the s. f heat ect the everal nce of e heat heat is at the mation aterial during shows break. caused ing of n 30% o 60% hand, E are s up to n both gure 5. ations, n and ion of Fig. stren 1) 2) 3) 4) 5) [1] [2] [3] [4] [5] [6] Vol. 8, No. 2, 20 ical Characteri 5. Effect of ngth, (c) on the el The main find The use o temperature in fully HD compared to The addition a remarkabl which reache only 0.2 wt% The heat g measured an The addition percentage o Elastic modu the addition fraction (0.5 observed. R. Bogue, “Nan Assembly Auto M. Alexandre “Polyethylene techniques: syn 8, pp. 2123-213 S. S. Ray, M. review from pr Vol. 28, No. 11 K. Yusoh, J. polyurethane/or nanoindentation 224, 2010 Z. Z. Wang, P nano-SiO2/poly Wear, Vol. 269 A. S. Alghamd strain rate effec polyethylene/ca No. 6, pp. 1105 18, 2814-2817 ization of High GNSs addition lastic modulus IV. CO dings in this w of solution combined wi DPE pellets the use of thi n of low weigh le increase i ed double that % GNSs. generation dur nd the effect w n of GNSs cau of strain at bre ulus and tensi of reinforcem 5 wt%), a red REFER nocomposites: a r omation, Vol. 31, , P. Dubois, T layered silicate nthesis and mecha 32, 2002 Okamoto, “Poly reparation to pro , pp. 1539–1641, Jin, M. Song, rganoclay nano n”, Progress in Or P. Gua, Z. Zhang ycarbonate comp , No. 1-2, pp. 21– di, I. A. Ashcrof cts on heat gener arbon black nano –1113, 2013 Density Polyet (a) on strain at NCLUSION work are summ blending ap ith mechanica dissolving in s method at ro ht fraction of in the micro t of HDPE wi ring plastic d was ignored. used significan ak. ile strength ar ments, however duction in th RENCES review of techno No. 2, pp. 106-11 T. 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