Effect of nano-SiO2 on physical and mechanical ... - Springer Link

J Indian Acad Wood Sci (December 2014) 11(2):116–121 DOI 10.1007/s13196-014-0126-y

ORIGINAL ARTICLE

Effect of nano-SiO2 on physical and mechanical properties of fiber reinforced composites (FRCs) S. Behnam Hosseini • Sahab Hedjazi • Loya Jamalirad • Alireza Sukhtesaraie

Received: 24 February 2014 / Accepted: 19 August 2014 / Published online: 3 September 2014 Ó Indian Academy of Wood Science 2014

Abstract This study evaluated reinforcing effect of waste lignocellulosic material (bagasse) and nano-SiO2 powder on physical and mechanical properties of nano-biocomposites. In the specimen preparation, three levels of nanoSiO2 (0, 2, and 5 wt%) and 40 wt% of fibers were used. In order to increase the interphase adhesion, polyethylene grafted with maleic anhydride was added as a coupling agent to all composites studied. The results showed that while tensile, flexural, and hardness properties were moderately improved by adding bagasse fibers and increasing nano-SiO2 (NDS) content, Izod impact strength decreased dramatically, but fibers filled composite with 5 wt% nanoSiO2 showed similar impact strength value to pure HDPE specimen. Natural fibers and increasing levels of nanoSiO2 particles led to an upward trend for water absorption, while thickness swelling sharply increased and leveled off with adding these fillers. The results of study demonstrate positive effects of waste lignocellulosic material and nanoSiO2 particles on physical and mechanical properties of composites. Keywords Fiber reinforced composite (FRC) Bagasse flour Nano-SiO2 HDPE

S. B. Hosseini S. Hedjazi (&) A. Sukhtesaraie Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran e-mail: [email protected] L. Jamalirad Faculty of Agriculture and Natural Resources, Gonbad Kavous University, Golestan, Iran

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Introduction Wood fiber and polymers such as PVC, HDPE and PP comprise wood-plastic composites (WPCs). The major application of WPCs in North America include decking, siding, railing, fences, window and door frames, etc. These outdoor applications expose WPCs to moisture, fungi, freeze–thaw actions, and ultraviolet light in sunlight. The presence of the hydrophobic polymer phase in WPC, improves the durability in terms of resistance to water absorption and biological decay compared to that of solid wood (Pilarski and Matuana 2005, 2006; Dawson-Andoh et al. 2004, 2005). Now-a-days the use of wood polymer composite (WPC) has tremendously increased due to their different advantages (Ayrilmis et al. 2010). With increased wood costs and competition of wood resources from traditional wood sectors, developing alternative, cheap, and environmentally friendly natural fiber sources for plastic composite is highly needed. The plant fiber used as a reinforcing agent rapidly improves the mechanical, thermal as well as other properties of the composite (De Rosa et al. 2010; Sui et al. 2009). There are a large variety of natural fibers such as rice straw, rice husk, palm, bagasse, hemp, flax, and other agricultural residues (Jiang and Kamdem 2004; Joo and Cho 1999; Ayora et al. 1997; Sombatsompop et al. 2003). These cheap natural fibers are normally made from waste part of the produces. As different natural fibers have different chemical compositions, physical structures, and mechanical properties, variation of properties can be expected from the composites resulted from different natural fibers (Bledzki and Gassan 1999). Blending of different polymers to achieve superior properties is a widely used process (Park 2008). Solution blending is one of the processes that are used for blending varieties of polymers and making polymer composite

J Indian Acad Wood Sci (December 2014) 11(2):116–121

(Deka and Maji 2010, 2011; Deka et al. 2011). But the major problems to make composite are the immiscibility among different polymers and decrease in interfacial adhesion between polymers and wood. This results in the formation of inferior composites. In order to improve the miscibility among the polymers as well as with wood, a third component called compatibilizer is used (Ashori 2008). Compatibilizer is such a compound which can interact with the hydrophobic polymer through their non polar group and with the hydrophilic wood flour (WF) through their polar group. This leads to an improvement in interfacial adhesion that enhances the properties (Chiu et al. 2010). Different types of compatibilizer like glycidyl methacrylate (GMA), polyethylene grafted glycidyl methacrylate (PE-g-GMA), maleic anhydride grafted polypropylene (MAPP), maleic anhydride grafted polyethylene (MAPE), etc. are widely used to enhance the compatibility among different polymers and WF (Devi and Maji 2007; Dikobe and Luyt 2007; Kim et al. 2007). Nanocomposites provide a new way to overcome the limitation of traditional counterparts. Because of significantly increased interfacial interaction between inorganic and organic phases and size-dependent phenomena of nanoscale particles, polymer nanocomposites are capable of dramatically improving the mechanical and thermal properties including stiffness and heat resistance, gas and solvent barrier property, flame retardance without losing good ductility of polymer (i.e. toughness) as compared with either homopolymer or traditional microcomposites. A number of polymer nanocomposites based on montmorillonite have been reported (Liang et al. 2004; Ding et al. 2008; Yarahmadi et al. 2010). Among different available nano-particle, silica nanoparticles are more useful for the fabrication of composites due to their amorphous structure, SiO2 content (more than 99 % purity in most products), and highly specific surface area (which leads to the super pozzolanic property) (Bahadori and Hosseini 2012). This study aims to produce green composites by presenting a hybrid composite system of natural fiber and silica nano-particles. Effect inclusion of nano-SiO2 on different properties of the composite has also been highlighted in the present study.

Materials and methods Injection molding grade high-density polyethylene (HDPE) was supplied by Jam Petrochemical Co. (Iran), with melt flow index of 18 g/10 min and density of 0.952 g/cm3. The coupling agent, maleic anhydride polyethylene (MAPE) was obtained from Kimiajavid chemical products (Iran), with trade name PE-G 101, melt flow index of 50–80 g/

117 Table 1 Composition of the studied formulation Composites

FRCs compositions (g) Nano-SiO2 (NDS)

MAPE

HDPE (PE)

Bagasse (B)

B/PE

165

120

–

B/PE ? 2 % NDS

165

114

6

15

B/PE ? 5 % NDS PE

165 300

105 –

15 –

15 –

15

10 min, and maleic anhydride content 0.8–1.2 %. Bagasse fibers as a lignocellulosic material, with average diameter of 28.53 lm and average length of 1,896.76 lm were investigated in this study. Bagasse was ground into flour, with particle size of 40 mesh. Nanoparticles of SiO2 (NDS), a product of Degussa Co., Germany, were used as nano-reinforcement for this study. The average diameter, density and specific surface of the SiO2 nanoparticles were 12 nm, 0.37 g/cm3, and 200 m2/g, respectively. Before specimen preparation, bagasse flour was dried in an oven at 103 ± 2 °C for 24 h. Formulation of the mixes and abbreviations used for the respective mixes prepared are given in Table 1. Composites were prepared by following processes: The compositions were extruded by Collin twin screw extruder (screw speed of 60 rpm, L/D 16, Germany, 1990), then they were grounded to prepare the granules using a pilot scale grinder (WIESER, WGLS 200/200 model). Experimental specimens were prepared by injection molding (Imen Machine, Iran) according to ASTM standard. Injection-molded specimens were tested fallowing ASTM standards, D 638 for tensile properties, D 790 for flexural properties, D 256 for notched Izod impact strength and D 2240 for hardness test. The flexural properties were measured in three-point bend tests. Flexural and tensile tests were conducted using an Instron Universal Testing Machine (model 4486) at crosshead speed of 8 mm/min at room temperature. Impact test was performed with a digital impact test machine (SANTAM, SIT-20 D model) using conventional V notched specimens. The hardness test was measured with a testing machine (SANTAM, SHD-05 model). Three replicates were tested for every property under each formulation. Physical properties, namely, water absorption (WA) and thickness swelling (TS) were tested in according to ASTM D 570. Before testing, the weight and thickness of each specimen were measured. Conditioned specimens of each type of composite were soaked in distilled water at room temperature for 2 and 24 h. For each measurement, specimens were removed from water, patted dry and then measured again. Each value obtained represented the

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Fig. 1 a Tensile strength as function of bagasse fibers and nano-SiO2 contents. b Tensile modulus (MOE) as function of bagasse fibers and nano-SiO2 contents

average of three specimens. WA and TS were calculated according to Eqs. (1) and (2). WA ð%Þ ¼ TS ð%Þ ¼

Wf Wi 100 Wi

Tf Ti 100 Ti

ð1Þ ð2Þ

where Wf (g) and Tf (mm) are the weight and thickness at given time, and Wi (g) and Ti (mm) are the initial weight and thickness, respectively.

Results and discussion The investigated waste lignocellulosic material is clearly distinguishable by their chemical composition, and different mechanical behavior can therefore be expected. HDPE was filled with various mixtures of bagasse fibers and nanoSiO2 to produce FRCs. Physical and mechanical properties of the produced composites are shown in Figs. 1 and 2.

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Fig. 2 a Flexural strength as function of bagasse fibers and nanoSiO2 contents. b Flexural modulus (MOR) as function of bagasse fibers and nano-SiO2 contents

Figure 1 shows FRCs results of the tensile strength and modulus of elasticity (MOE) with varying amount of nanoSiO2 compared to HDPE specimen. It is evident that moderate increase in tensile strength occurred upon filling the polymer matrix with bagasse fibers and nano-SiO2, indicating a reinforcing effect from theses fillers. Salemane and Luyt (2006) studied the improvement in mechanical properties of wood/polypropylene composite after the incorporation of wood flour. Generally, the tensile properties of composites are markedly improved by adding fibers to a polymer matrix since fibers have much higher strength and stiffness values than those of the matrices (Malkapuram et al. 2008; Holbery and Houston 2006). It is to be noted that as nano-SiO2 content increases, tensile strength increases up to load of 38.82 MPa for bagasse filled composite reinforced with 5 wt% nano-SiO2. On the other hand, it is obvious from Fig. 1a that adding bagasse fibers regardless nano-SiO2 content and increasing nano-


SiO2 content from 2 to 5 wt% led to increase tensile strength in fiber reinforced composites (FRCs) up to 15.10 and 71.46 % in comparison with HDPE specimen, respectively. Increasing Tensile strength by adding bagasse fibers is in line with the results obtained by Malunka et al. (2006). As can be seen from Fig. 1b, the composite made using 5 wt% nano-SiO2 has the highest tensile modulus value among the composites evaluated in this investigation. Maximum tensile modulus range from 2,120 to 3,718.3 MPa for nano-biocomposites, while maximum tensile modulus of pure HDPE is approximately 1,155.3 MPa. Moreover, the tensile modulus of pure HDPE is enhanced threefold (221.84 % increase of MOE in comparison with pure HDPE) when bagasse fibers and nano-SiO2 (5 wt%) were added. Tensile moduli of composites have increased with the increasing nano-SiO2 content. Bagasse fibers regardless nano-SiO2 content increased tensile modulus and this is because natural fillers are normally stiffer than the polymer matrix and this naturally increases the stiffness of the composites (Salemane and Luyt 2006). Figure 2 presents results of the flexural strength and modulus of rupture (MOR) of nano-biocomposites. The flexural strength of composites (Fig. 2a) slightly varies with adding natural fiber (bagasse) and nano-SiO2 particles, while differences are significant. Composites made with natural fibers and nano-silica show the highest strength and modulus of flexural, whereas pure HDPE exhibit the lowest properties. The strength of fiber reinforced composites depends on the properties of constituents and the interface interaction. However, when considering the flexural properties, homogeneity of the overall composite needs to be taken into account (Balasuriya et al. 2001). Modulus of rupture of composites increased with increasing nano-SiO2 content. Comparison of the results for composites with varying nano-SiO2 content shows that the flexural strength and MOR of the composites increase with increasing nanoSiO2 content. When the amount of 5 wt% nano-SiO2 and bagasse fibers are added, flexural strength and MOR shows the highest value, increasing by about 103.16 and 243.06 % compared with specimen without nano-SiO2 particles, respectively. It is also noteworthy that the flexural strength and MOR of composites are significantly greater than the pure HDPE (two and threefold, respectively). Researchers who have measured flexural properties of natural fiber nanocomposites have reported similar trends. The notched Izod impact tests were conducted at room temperature. Figure 3a illustrates the impact strength of the composites made with the natural fibers (bagasse) and different levels of nano-SiO2 content. The impact

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Fig. 3 a Comparison of impact strength of the composites as function of bagasse fibers and nano-SiO2 contents. b Comparison of hardness of the composites as function of bagasse fibers and nanoSiO2 contents

properties of composites vary significantly with fibers and nano-SiO2 particles. Pure HDPE exhibited the highest impact strength, whereas bagasse filled composite reinforced with 2 wt% nano-SiO2 showed the lowest properties, and bagasse filled composite treated with 5 wt% nanoSiO2 showed as draw impact strength as pure HDPE (62.66 J). Thus, addition of nano-SiO2 led to different results in impact strength of composites, both negative and positive effect depend on addition of 2 and 5 wt% nanoSiO2, respectively. The Izod impact strength of composites decreased with adding natural fibers. Lignocellulosic flour is a kind of stiff organic filler, so adding flour could decrease the impact strength of composite since the debonding behavior between the interface of fiber and HDPE matrix absorbs larger impact energy in modified composites than the unmodified ones. Hardness results of pure HDPE and FRCs with different percentage of nano-SiO2 loading were presented in Fig. 3b.

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Fig. 4 a Comparison of water absorption (WA) of the composites as function of bagasse fibers, nano-SiO2 contents, and time. b Comparison of thickness swelling (TS) of the composites as function of bagasse fibers, nano-SiO2 contents, and time

It was observed that hardness value of the pure HDPE increased after the addition of bagasse fibers and increasing nano-SiO2 content. At the higher nano-SiO2 loading (5 wt%), hardness value showed the highest value (58 Shore A) compared to other composites. Fiber filled composite in comparison with pure HDPE did not show significant difference in hardness value, while with adding nano-SiO2 powder, the hardness value increased up to 8.07 %. The improvement was due to the filling role of nano-SiO2 particles and their high specific surface. Deka et al. (2011) reported that with incorporation of nanoparticles to WPC, hardness value was found to increase. Water absorption is one of the key parameters in quality assessment of FRCs. Hydrophilicity represents a characteristic of the filler surface induced by the hydroxyl groups capable of interacting with one another to from inter and intramolecular hydrogen bonds. In this respect, chemical compositions of fillers play an important role in water absorption properties of FRCs (Gwon et al. 2010). Lignocellulosic materials contain cellulose, hemicellulose,

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lignin, and extractive in various amounts and chemical composition. Cellulose, the most abundant biopolymer on earth, is a natural polymer containing many hydroxyl groups, and these groups and their ability to from hydrogen bonds govern the physical properties of cellulose. In addition, non-cellulosic carbohydrates or hemicelluloses have amorphous structure and hydrophilic characteristic, so water can be absorbed in hemicellulose. However, lignin is totally amorphous and hydrophobic, therefore water absorption cannot occur in lignin. The extractives are comprised of tannins, pectins, fats, waxes, gums, essential oils and volatile materials, and thus these cannot absorb water, either. Figure 4a shows the percentage of the water absorption (WA) for the nano-biocomposites, which vary depending upon the nano-SiO2 contents. The water absorption of pure HDPE increased with adding natural fibers and increasing nano-SiO2 content. It is due to hydrogen bonding of the water molecules to the free hydroxyl groups present in the cellulosic cell wall material and the diffusion of water molecules into the filler-matrix interface. Many studies have supported the above observation (Panthapulakkal and Sain 2007). However, the water absorption of composites were less than 0.35 % even in long time (24 h), due to filling gaps by nano-SiO2 particles and appropriate graft between fibers and polymer matrix with coupling agent (5 wt% MAPE). The effect of natural fibers and nano-SiO2 on the thickness swelling of composites is presented in Fig. 4b. The thickness swelling of the composites increases with the water absorption, but without similar trend to the water absorption. The bagasse filled composite with 2 wt% nanoSiO2 exhibited maximum thickness swelling after 2 h (0.81 %). The trend of thickness swelling after 24 h is completely different, a similar value of thickness swelling for all nano-biocomposites. However, the TS of composites were less than 1 % which is low notable TS for FRCs.

Conclusions The present study shown that waste lignocellulosic material along with mineral filler (nano-SiO2) can be successfully utilized to make FRCs with useful physical and mechanical properties. Higher nano-SiO2 content generally improves the mechanical properties of all the composites reinforced by lignocellulosic material. Sample made pure HDPE has inferior mechanical properties compared to fiber filled composites. All the composites absorbed water to certain extent which is quite marginal and that can be attributed to content of lignocellulosic material present in the composites. In general, fiber filled composites with 5 wt% nano-SiO2 loading showed maximum mechanical


properties, water absorption, and acceptable thickness swelling in nano-biocomposites. The water absorption and thickness swelling of the composites increased as the fibers and nano-SiO2 content added. Acknowledgments The authors gratefully acknowledge Department of Wood and Paper Science and Technology, Natural Resources Faculty, University of Tehran, Iran for the testing equipment used in this investigation. Further acknowledgement goes to Iran Polymer and Petrochemical Institute (IPPI) for the laboratory equipment used in the FRC panel manufacture.

References Ashori A (2008) Wood–plastic composites as promising greencomposites for automotive industries. Bioresour Technol 99(11):4661–4667 Ayora M, Rios R, Quijano J, Marquez A (1997) Evaluation by torquerheometer of suspensions of semi-rigid and flexible natural fibers in a matrix of poly(vinyl chloride). Polym Compos 18(4):549–560 Ayrilmis N, Buyuksari U, Dundar T (2010) Waste pine cones as a source of reinforcing fillers for thermoplastic composites. J Appl Polym Sci 117(4):2324–2330 Bahadori H, Hosseini P (2012) Reduction of cement consumption by the aid of silica nano-particles (investigation on concrete properties). J Civil Eng Manag 18(3):416 Balasuriya PW, Ye L, Mai YW (2001) Mechanical properties of wood flake–polyethylene composites. Part I: effects of processing methods and matrix melt flow behavior. Compos A 32(5):619–629 Bledzki AK, Gassan J (1999) Composites reinforced with cellulose based fibres. Prog Polym Sci 24:221–274 Chiu FC, Yen HZ, Lee CE (2010) Characterization of PP/HDPE blend-based nanocomposites using different maleated polyolefins as compatibilizers. Polym Test 29(3):397–406 Dawson-Andoh B, Matuana LM, Harrison J (2004) Mold susceptibility of rigid PVC/wood-flour composites. J Vinyl Addit Technol 10(4):179–186 Dawson-Andoh B, Matuana LM, Harrison J (2005) Susceptibility of high-density polyethylene/wood-flour composite to mold discoloration. J Inst Wood Sci 17(2):114–119 De Rosa IM, Kenny JM, Puglia D, Santulli C, Sarasini F (2010) Morphological, thermal and mechanical characterization of okra (Abelmoschus esculentus) fibres as potential reinforcement in polymer composites. Compos Sci Technol 70(1):116–122 Deka BK, Maji TK (2010) Effect of coupling agent and nanoclay on properties of HDPE, LDPE, PP, PVC blend and Phargamites karka nanocomposite. Compos Sci Technol 70(12):1755–1761 Deka BK, Maji TK (2011) Effect of TiO2 and nanoclay on the properties of wood polymer nanocomposite. Compos A 42:2117–2125 Deka BK, Mandal M, Maji TK (2011) Study on properties of nanocomposites based on HDPE, LDPE, PP, PVC, wood and clay. Polym Bull. doi:10.1007/s00289-011-0529-5 Devi RR, Maji TK (2007) Effect of glycidyl methacrylate on the physical properties of wood–polymer composites. Polym Compos 28(1):1–5

121 Dikobe DG, Luyt AS (2007) Effect of poly(ethylene-co-glycidyl methacrylate) compatibilizer content on the morphology and physical properties of ethylene vinyl acetate–wood fiber composites. J Appl Polym Sci 104(5):3206–3213 Ding C, He H, Guo B, Jia D (2008) Structure and properties of polypropylene/clay nanocomposites compatibilized by solidphase grafted polypropylene. Polym Compos 29(6):698–707 Gwon JG, Lee SY, Chun SJ, Doh GH, Kim JH (2010) Effects of chemical treatments of hybrid fillers on the physical and thermal properties of wood plastic composites. Compos A 41(10):1491–1497 Holbery J, Houston D (2006) Natural-fiber-reinforced polymer composites in automotive applications. JOM 58(11):80–86 Jiang H, Kamdem DP (2004) Development of poly(vinyl chloride)/ wood composites. A literature review. J Vinyl Addit Technol 10(2):59–69 Joo YL, Cho MH (1999) Utilization of rheology control to develop wood grain patterned PVC/wood flour composites. Int Polym Proc 14:10–20 Kim HS, Lee BH, Choi SW, Kim S, Kim HJ (2007) The effect of types of maleic anhydride-grafted polypropylene (MAPP) on the interfacial adhesion properties of bio-flour-filled polypropylene composites. Compos A 38(6):1473–1482 Liang G, Xu J, Bao S, Xu W (2004) Polyethylene/maleic anhydride grafted polyethylene/organic-montmorillonite nanocomposites. I. Preparation, microstructure, and mechanical properties. J Appl Polym Sci 91(6):3974–3980 Malkapuram R, Kumar V, Yuvraj SN (2008) Recent development in natural fibre reinforced polypropylene composites. J Reinf Plast Compos 28:1169–1189 Malunka ME, Luyt AS, Krump H (2006) Preparation and characterization of EVA–sisal fiber composites. J Appl Polym Sci 100(2):1607–1617 Panthapulakkal S, Sain M (2007) Agro-residue reinforced highdensity polyethylene composites: fiber characterization and analysis of composite properties. Compos A 38(6):1445–1454 Park ES (2008) Morphology, mechanical and dielectric breakdown properties of PBT/PET/TPE, PBT/PET/PA66, PBT/PET/LMPE and PBT/PET/TiO2 blends. Polym Compos 29(10):1111–1118 Pilarski JM, Matuana LM (2005) Durability of wood flour-plastic composites exposed to accelerated freeze–thaw cycling. Part I. Rigid PVC matrix. J Vinyl Addit Technol 11(1):1–8 Pilarski JM, Matuana LM (2006) Durability of wood flour-plastic composites exposed to accelerated freeze-thaw cycling. Part II. High density polyethylene matrix. J Appl Polym Sci 100(1):35–39 Salemane MG, Luyt AS (2006) Thermal and mechanical properties of polypropylene–wood powder composites. J Appl Polym Sci 100(5):4173–4180 Sombatsompop N, Chaochanchaikul K, Phromchirasuk C, Thongsang S (2003) Effect of wood sawdust content on rheological and structural changes, and thermo-mechanical properties of PVC/ sawdust composites. Polym Int 52:1847 Sui G, Fuqua MA, Ulven CA, Zhong WH (2009) A plant fiber reinforced polymer composite prepared by a twin-screw extruder. Bioresour Technol 100(3):1246–1251 Yarahmadi N, Jakubowicz I, Hjertberg T (2010) Development of poly(vinyl chloride)/montmorillonite nanocomposites using chelating agents. Polym Degrad Stab 95(2):132–137

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