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Synthesis and characterization of zinc oxide (ZnO) filled glass fiber reinforced polyester composites
Materials and Design 67 (2015) 313–317
Contents lists available at ScienceDirect
Materials and Design journal homepage: www.elsevier.com/locate/matdes
Technical Report
Synthesis and characterization of zinc oxide (ZnO) filled glass fiber reinforced polyester composites Nafisa Gull a, Shahzad Maqsood Khan a,⇑, Muhammad Azeem Munawar a, Muhammad Shafiq a, Farheen Anjum a, Muhammad Taqi Zahid Butt b, Tahir Jamil a a b
Department of Polymer Engineering & Technology, University of the Punjab, Lahore, Pakistan College of Engineering and Emerging Technologies, University of the Punjab, Lahore, Pakistan
a r t i c l e
i n f o
Article history: Received 15 May 2014 Accepted 20 November 2014 Available online 27 November 2014
a b s t r a c t This study aims at fabrication of zinc oxide (ZnO) filled glass fiber reinforced polyester (GFRP) composites with varying concentrations of filler and investigation of their mechanical and thermal behavior. In this study, ZnO was dispersed in polyester, and laminates were fabricated by hand lay-up technique followed by compression molding. Mechanical properties were determined by flexural strength analysis, impact strength and hardness testing whereas thermal stability by thermogravimetric analysis (TGA). Flexural strength of 3 wt.% ZnO filled GFRP composite was improved significantly (up to 62.12%) in comparison to unfilled composite. Hardness, impact strength and thermal stability have also been found increased gradually with increase in ZnO loading. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Composites are in use as a substitute of conventional structural materials (steel, wood, ceramics and metals) due to their improved strength at small specific weight [1–4]. They are extensively used worldwide because of their distinct characteristics such as low density, high rigidity, eminent strength, greater specific modulus and ability to be tailored for specific purposes [5–8]. They have also amplified applications in several engineering fields because of their competent mechanical properties, excellent impact characteristics, elevated strength to weight ratio, outstanding resistance to corrosion, improved compressive and tensile strength, low coefficient of thermal expansion and better fatigue resistance [9–11]. One of the substantial benefit which directs the research workers to concentrate on composites is their versatile range of tribological and mechanical properties that can be achieved using multiple types of reinforcements in different orientations with variable volume fractions [12]. A fiber reinforced polymer (FRP) composite material comprises of a polymer which acts as a matrix and a reinforcing material which is selected as per desired applications and properties [13]. In conventional FRP composite, fiber behaves as standard load carrying candidate while the matrix is used to transfer the load to fiber and to shield it from any defect [14]. Glass fiber is a widely ⇑ Corresponding author. Tel.: +92 0300 7152120. E-mail addresses: [email protected], [email protected] (S.M. Khan). http://dx.doi.org/10.1016/j.matdes.2014.11.021 0261-3069/Ó 2014 Elsevier Ltd. All rights reserved.
used reinforcing material due to its excellent corrosion resistance, weight saving, high impact, greater tensile strength and low cost [15–17]. It is commonly used with polymer matrices such as vinyl ester, epoxy resin, unsaturated polyester resin and isophthalic polyester resin [18]. To cope with some limitations of polymers like low stiffness and decreased strength, ceramic fillers are employed to improve their mechanical, tribological, thermal, physical and electrical characteristics [19–21]. Fillers infused in polymeric composites, not only minimize the cost of composite material but also execute the high performance demands and improve the quality of polymeric composite [22,23]. A major problem to use filler in polymeric composites is the aggregation of filler and stabilization of its dispersion. This problem is solved by mechanical agitation [24] and ultrasonication [17,25]. ZnO is inorganic filler and semiconductor material existing in a diversity of structures. It is extensively used due to its distinctive optical, electrical, photocatalytic, optioelectronic, antibacterial and dermatological properties [26,27]. ZnO addition in polymer material increases hardness, impact, flexural properties and thermal stability of composite materials [28]. A lot of research work has showed the potential improvement in performance and properties of fiberous composites in which different filler particles were integrated. Madugu and co-workers [29] indicated that by increasing the amount of iron filler in fiber–polyester composites, a significant improvement of 77.8%, 55.6% and 30% was observed in hardness, porosity and density values respectively; and a considerable decrease of 17.1% and 37.55% was found in impact energy and linear shrinkage respectively. Garay et al.
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[30] evaluated the effect of calcium carbonate on polyester fiber composite and concluded that it caused improved elastic modulus, short beam strength and hardness; while decreased flexural, tensile and impact strength. Moorthy and Manonmani [24] studied that 10 wt.% titanium oxide (TiO2) addition in fiber–polyester composite resulted in noticeable increase in tensile strength, impact strength, hardness and chemical resistance. However research toward ZnO influence on the mechanical and thermal properties of composites is still novel and work is in progress in this field. In this study, GFRP composites with 1–5 wt.% ZnO were fabricated by hand lay-up technique followed by compression molding. The effect of ZnO on thermal and mechanical performance of synthesized composites was investigated.
without using ZnO in polyester resin. The formulation of various composites is given in Table 1. 3. Characterization 3.1. Flexural strength
2. Experimental details
Universal Testing Machine (UTM) Testometric UK Model Number FS100 CT with 100 KN load cell was used to determine the flexural properties under three-point bending configuration. Five individual samples (with dimensions of 127 14.5 2.5 mm as per ASTM) for all compositions were prepared according to ASTM: D790-10 to measure flexural strength and modulus. A span of 80 mm, containing a span to depth ratio 32:1, was used. The samples were positioned in the middle of the supports. UTM was operated at a speed of 1.0 mm/min at ambient temperature conditions.
2.1. Materials
3.2. Impact strength
E-glass roving strand mat was obtained from Taishan Fiberglass Inc., China. ZnO (melting point 1970 °C and 5.58 g/cm3 density) was purchased from Merck, Germany. Unsaturated polyester resin (with 42% styrene contents and 3% fumed silica flash point 35 °C, density: 1.11–1.23 g/cm3), Methyl ethyl ketone peroxide (MEKP) and Cobalt Naphthanate were purchased from local commercial market and were used in this study without any pre-treatment.
Pendulum Impact Tester Model CSI-137 of Custom Scientific Instruments (CSI) USA was used to determine the impact strength of fabricated composites. The impact strength of specimens was determined according to ASTM: D256-10 in Izod mode. Five individual samples (with dimensions of 63.5 12.7 2.5 mm) were prepared for impact testing and notched as per ASTM. 3.3. Hardness
2.2. Method 2.2.1. Dispersion of zinc oxide in polyester resin ZnO was dispersed in polyester matrix in different compositions (1–5 wt.%) using high speed disperser at 1000 rpm for 30 min. 2.2.2. Preparation of composite laminates Hand lay-up processing technique was used for composite formation. 1% MEKP catalyst was added to the prepared dispersion of ZnO filled polyester resin and stirred for 2 min. It was followed by addition of 0.5% Cobalt Naphthanate accelerator to initiate the curing of polyester resin prior to reinforcement. The mixture was stirred to mix the catalyst and initiator in the matrix. Four layers of cross plied woven roving glass fiber mat with dimensions of 178 mm 178 mm 20 mm were placed separately on aluminum foil at work table and ZnO filled polyester resin was poured on these layers uniformly. Finally, these layers were stacked on one another and were wrapped in aluminum foil. 2.2.3. Processing of composite materials The composite laminates were processed by hot compression molding technique. The mold of High Temperature Melt Press was made up of stainless steel having size of 178 mm 17 8 mm 20 mm. These composite laminates were placed in melt press under pressure of 2.844 psi at 80 °C for 1 h to obtain uniform thickness. Composite was post cured under same pressure for 1 h and was cooled to 60 °C and was removed out of the mold as final product. Control sample of GFRP composite was also fabricated
Table 1 Formulation of composites with different wt.% of filler. Sr. No.
Matrix content (wt.%)
Fiber contents (wt.%)
Zinc oxide (wt.%)
1 2 3 4 5 6
50 50 50 50 50 50
50 50 50 50 50 50
0 1 2 3 4 5
Hardness of samples (with dimension of 25.4 25.4 2.5 mm) was determined using a Bench Rockwell Hardness Tester Model NR3-DR Ernst Switzerland following ASTM: D785-08. A carbide ball indenter with spherical base of 2.5 mm diameter was penetrated into the material under applied load F. Preload was 1000 kp while applied load was 62.5 kp with ratio HB10. Brinell hardness was noted at ten different places on the specimen. 3.4. Thermogravimetric analysis (TGA) Simultaneous Differential Scanning Calorimeter Thermogravimetric Analyzer (SDT) Model Q600 of TA Instrument USA was used to perform TGA of fabricated composites. Thermal behavior of each sample (10 mg) was noted by heating across a temperature range of 30–800 °C, at heating rate of 10 °C/min in nitrogen environment. 4. Results and discussion 4.1. Flexural properties Flexural tests were conducted to examine the flexural strength and bulk stiffness of unfilled and ZnO filled GFRP composites. Figs. 1 and 2 show the changes in flexural strength and flexural modulus respectively due to ZnO contents on GFRP composites. Flexural strength was observed to be higher for ZnO filled GFRP composite than unfilled specimen. Plot of flexural strength vs. ZnO content (%) (Fig. 1) shows an initial increase in flexural strength of GFRP composite up to 3 wt.% of ZnO content followed by a decreasing trend. It has been observed that 3 wt.% is the optimal concentration for ZnO to be incorporated in GFRP composite. In flexural strength test, sample is positioned in the middle of the supports and force is applied from top of the sample. During this phenomenon, top layer of sample endures the compression while bottom layer goes through tensile loading. When the interfacial adhesion between matrix, fiber and filler increases, flexural strength increases. This strong adhesion transfers load from one end of the sample to other end which ultimately increases flexural strength. When concentra-
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80
72 66
65
58
60
56
50
40
4.3. Hardness 30
25 20 0
1
2
3
4
5
ZnO Content (%) Fig. 1. Flexural strength of ZnO filled composites.
10175
10000
Flexural Modulus (MPa)
9116
8874
8000
6806 6000
4.4. Thermogravimetric analysis (TGA)
4000
2000
The Brinell Hardness Value (BHV) of different composite materials with different weight percentages of ZnO is shown in Fig. 4. The hardness of composite materials has been observed to be increased gradually with increasing weight percentage of ZnO. For sample having 1 wt.% of ZnO, the hardness value was 131 BHV in comparison to 197 BHV while for 5 wt.% of ZnO filled GFRP composite, which is increased up to 48%. The reason behind resistance in penetration or increased hardness is ascribed to the fact that when compression stress is applied on the sample; matrix, fiber and filler are pressed simultaneously and contacted with each other more significantly. Therefore, interface will transfer pressure more effectively although the interfacial bond may be weak [33,37,38]. It is also due to increase in adhesion between matrix and reinforcements and reduced porosity due to addition of ZnO. As with increasing filler concentration in FRP composites, the inter particle distance is decreased which results in increased hardness [35,39].
3494 1947
0
1
2
3
4
5
ZnO Content (%) Fig. 2. Flexural modulus of ZnO filled composites.
tion of filler exceeds the optimum value, surface area increases but weight percentage of matrix contents decreases. This weakens bonding strength and load is not transferred uniformly throughout the specimen which results in decrease of flexural strength of composites. Also higher concentration of ZnO filler disturbs the continuity of matrix indicating poor adhesion between matrix, fiber and filler particles [31,32]. Decreasing trend is also imputed by the formation of aggregates of ZnO particles in different regions of polyester matrix when added in large amount. These aggregates of filler do not strongly interact with reinforcement and filler materials after a specific concentration resulting in the decrease of flexural strength of composites [17]. 4.2. Izod impact test The strength, weight fraction and orientation of filler affect the impact strength of fiber reinforced composite considerably. In this study, the orientation of glass fiber was kept constant in all samples and behavior of Izod impact strength was recorded with different filler contents. A significant improvement of the order of about 40% in impact strength is observed with the increase in filler loading up to 5 wt.% as shown in Fig. 3. Major factors which affect
TGA behavior of unfilled and ZnO filled GFRP composite was recorded to estimate the thermal stability of specimens (Fig. 5). During TGA, weight of the analyzed material decreased due to the decomposition or volatilization while increase in weight occurs due to the gas absorption or some chemical reaction [40]. Thermal decomposition profile of ZnO filled glass fiber reinforced polyester composites shows the weight loss in different steps. The weight loss in temperature range of 30–130 °C is attributed to the elimination of moisture and bound water gradually from composite materials [41,42]. The second phase weight loss with highest decomposition rate is associated with scission of weak bonds and unzipping of
0.55
Izod Impact Strength (J/m)
Flexural Strength (MPa)
70
the impact strength of composites are interfacial adhesion between matrix and inorganic filler, matrix fracture and fiber pullout [33,34]. Devendra and Rangaswamy and Jena et al. demonstrated that the impact energy values of GFRP composite increases with inclusion of filler is due to the improvement in bonding strength among inorganic filler, matrix and fiber. Thus ZnO filled GFRP composites has ability to absorb more energy, has greater fracture strength as compared to simple GFRP composite without filler and hence can stop crack propagation [35,36]. The behavior of impact test in present study depicts that ZnO will be promising filler in future composites.
0.54 0.49
0.50
0.46 0.45
0.41 0.40
0.38
0.35
0.32 0.30 0
1
2
3
4
ZnO Content (%) Fig. 3. Izod impact strength of ZnO filled composites.
5
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197
Brinell Hardness Values (BHV)
200
182 180
160
155
160
Acknowledgment 140
We are grateful for Department of Polymer Engineering & Technology, University of the Punjab, Lahore, Pakistan for help in completion of this research regarding all aspects of synthesis and characterization.
131 120
117 0
1
2
3
4
Appendix A. Supplementary material
5
ZnO Content (%)
Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.matdes.201 4.11.021.
Fig. 4. Brinell hardness values of ZnO filled composites.
0% ZnO 1% ZnO 2% ZnO 3% ZnO 4% ZnO 5% ZnO
100 90
Weight Loss (%)
Impact energy is enhanced gradually by increasing the filler concentration in fiber reinforced composites. Hardness also shows similar increasing behavior. Degradation temperature of ZnO filled composite has been found increased but amount of residue decreased up to 3 wt.%. Beyond this concentration negative effect was observed. Hence, it is concluded that ZnO is a promising filler for GFRP composite as it is responsible for the incremental modification in its mechanical and thermal behavior.
80
References
70 60
50 40 0
100
200
300
400
500
600
700
800
900
0
Temperature ( C) Fig. 5. Thermogravimetric analysis of ZnO filled composites.
highly strained cross links resulting in the formation of straight chains. Then linear polymer backbone chain decomposed into small fragments at higher temperature [16,43]. The residue after 800 °C is attributed to the left behind amount of glass fiber and ZnO filler after the entire burning of polyester matrix. Slight improvement in degradation temperature was observed up to 3 wt.% of ZnO incorporation after which decreasing trend was noted. Weight loss was less for 3 wt.% ZnO filled GFRP composite compared to the unfilled sample. This is due to the fact that filler is preventing the movement of molecular chains of polyester at higher temperature, thus minimizing the weakening of the interface between filler and matrix. This finding is in accordance with the study by Hossain and co-workers [25]. It was determined from this analysis that the 3 wt.% of ZnO showed the weight loss up to 47.71% which was increased up to 49.79% for 4 wt.% of ZnO. 5. Conclusion It is evident from this study that mechanical and thermal properties of GFRP composite are improved with incorporation of ZnO filler. Flexural modulus and flexural strength are enhanced by raising the filler loading up to 3 wt.% of ZnO and then decreased.
[1] Kim HG, Lee DG. Dielectric cure monitoring for glass/polyester prepreg composites. Compos Struct 2002;57:91–9. [2] Sul JH, Prusty BG, Ray T. Prediction of low cycle fatigue life of short fibre composites at elevated temperatures using surrogate modelling. Compos B 2011;42:1453–60. [3] Sakin R, Ay I. Statistical analysis of bending fatigue life data using Weibull distribution in glass–fiber reinforced polyester composites. Mater Des 2008;29:1170–81. [4] Guades E, Aravinthan T, Islam MM. Characterisation of the mechanical properties of pultruded fibre-reinforced polymer tube. Mater Des 2014;63:305–15. [5] Devendra K, Rangaswamy T. Evaluation of thermal properties of E-glass/epoxy composites filled by different filler materials. Int J Comput Eng Res 2012;2(5):1708–14. [6] Idicula M, Boudenne A, Umadevi L, Ibos L, Candau Y, Thomas S. Thermophysical properties of natural fibre reinforced polyester composites. Compos Sci Technol 2006;66:2719–25. [7] Sakin R, Ay I, Yaman R. An investigation of bending fatigue behavior for glass– fiber reinforced polyester composite materials. Mater Des 2008;29:212–7. [8] Shokrieh MM, Saeedi A, Chitsazzadeh M. Evaluating the effects of multi-walled carbon nanotubes on the mechanical properties of chopped strand mat/ polyester composites. Mater Des 2014;56:274–9. [9] Sutherland LS, Soares CG. Effects of laminate thickness and reinforcement type on the impact behaviour of E-glass/polyester laminates. Compos Sci Technol 1999;59:2243–60. [10] Rajamurugan TV, Shanmugam K, Palanikumar K. Analysis of delamination in drilling glass fiber reinforced polyester composites. Mater Des 2013;45:80–7. [11] Yao XF, Kolstein MH, Bijlaard FSK, Xu W, Xu M. Tensile strength and fracture of glass fiber-reinforced plastic (GFRP) plate with an eccentrically located circular hole. Polym Test 2003;22:955–63. [12] El-Sayed AA, El-Sherbiny MG, Abo-El-Ezz AS, Aggag GA. Friction and wear properties of polymeric composite materials for bearing applications. Wear 1995;184:45–53. [13] Pihtili H. An experimental investigation of wear of glass fibre–epoxy resin and glass fibre–polyester resin composite materials. Eur Polym J 2009;45:149–54. [14] Nirmal U, Low KO, Hashim J. On the effect of abrasiveness to process equipment using betelnut and glass fibres reinforced polyester composites. Wear 2012;290–291:32–40. [15] Mohebby B, Fallah-Moghadam P, Ghotbifar AR, Kazemi-Najafi S. Influence of maleic-anhydride-polypropylene (MAPP) on wettability of polypropylene/ wood flour/glass fiber hybrid composites. J Agric Sci Technol 2011;13:877–84. [16] López FA, Martín MI, Alguacil FJ, Rincón JM, Centeno TA, Romero M. Thermolysis of fibreglass polyester composite and reutilisation of the glass fibre residue to obtain a glass–ceramic material. J Anal Appl Pyrol 2012;93:104–12. [17] Hossain MK, Hossain ME, Hosur MV, Jeelani S. Flexural and compression response of woven E-glass/polyester–CNF nanophased composites. Compos A 2011;42:1774–82. [18] Tanoglu M, Seyhean AT. Investigating the effects of a polyester preforming binder on the mechanical and ballistic performance of E-glass fiber reinforced polyester composites. Int J Adhes Adhes 2003;23:1–8. [19] Sahu H, Rout A, Kumar A. Development and characterization of particulate filled glass fiber reinforced hybrid composites. Int J Mech Ind Eng 2012;2(3):89–93.
N. Gull et al. / Materials and Design 67 (2015) 313–317 [20] Detomi AC, Santos RMD, Filho SLMR, Martuscelli CC, Panzera TH, Scarpa F. Statistical effects of using ceramic particles in glass fibre reinforced composites. Mater Des 2014;55:463–70. [21] Raja RS, Manisekar K, Manikandan V. Study on mechanical properties of fly ash impregnated glass fiber reinforced polymer composites using mixture design analysis. Mater Des 2014;55:499–508. [22] Sathiyamurthy S, Thaheer ASA, Jayabal S. Prediction and optimization of mechanical properties of particles filled coir–polyester composites using ANN and RSM algorithms. Indian J Fiber Textile Res 2013;38:81–6. [23] Fu S-Y, Feng X-Q, Lauke B, Mai Y-W. Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites. Compos B 2008;39:933–61. [24] Moorthy SS, Manonmani K. Fabrication and characterization of TiO2 particulate filled glass fiber reinforced polymer composite. Mater Phys Mech 2013;18:28–34. [25] Hossain MK, Hossain ME, Dewan MW, Hosur M, Jeelani S. Effects of carbon nanofibers (CNFs) on thermal and interlaminar shear responses of E-glass/ polyester composites. Compos B 2013;44:313–20. [26] Loto CA. The foundation and the fundamental pillar of world technological civilization and economic development. Public Lecture Ser 2007;1(17). [27] Yahya N, Puspitasari P, Latiff NRA. Hardness improvement of dental amalgam using zinc oxide and aluminum oxide nanoparticles. Charact Dev Biosyst Biomater Adv Struct Mater 2013;29:9–32. [28] Hong JI, Winberg P, Schadler LS, Siegel RW. Dielectric properties of zinc oxide/ low density polyethylene nanocomposites. Mater Lett 2005;59:473–6. [29] Madugu IA, Abdulwahab M, Aigbodion VS. Effect of iron fillings on the properties and microstructure of cast fiber–polyester/iron filings particulate composite. J Alloys Compd 2009;476:807–11. [30] Garay AC, Heck V, Zattera AJ, Souza JA, Amico SC. Influence of Calcium Carbonate on RTM and RTM light processing and properties of molded composites. J Reinf Plast Compos 2011;30(14):1213–21. [31] Kaundal R, Satapathy PatnaikA. A comparison of the mechanical and thermomechanical properties of unfilled and SiC filled short glass polyester composites. Silicon 2012;4:175–88.
317
[32] Agarwal G, Patnaik A, Sharma RK. Thermo-mechanical properties of silicon carbide-filled chopped glass fiber-reinforced epoxy composites. Int J Adv Struct Eng 2013;5(21):1–8. [33] Kaundal R, Patnaik A, Satapathy A. Effect of SiC particulate on short glass fiber reinforced polyester composite in erosive wear environment. Walailak J Sci Technol 2012;9(1):49–64. [34] Fu S-Y, Feng X-Q, Lauke B, Mai Y-W. Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites. Composites Part B 2008;39:933–61. [35] Devendra K, Rangaswamy T. Strength characterization of E-glass fiber reinforced epoxy composites with filler materials. J Miner Mater Charact Eng 2013;1:353–7. [36] Jena H, Pandit MK, Pradhan AK. Study the impact property of laminated bamboo–fibre composite filled with cenosphere. Int J Environ Sci Dev 2012;3(5):456–9. [37] Raju BR, Swamy RP, Suresha B, Bharath KN. The effect of silicon dioxide filler on the wear resistance of glass fabric reinforced epoxy composites. Adv Polym Sci Technol: An Int J 2012;2(4):51–7. [38] Mohapatra S, Mantry S, Singh SK. Performance evaluation of glass–epoxy–TiC hybrid composites using design of experiment. J Compos 2014;2014:1–9. [39] Antunes PV, Ramalho A, Carrilho EVP. Mechanical and wear behaviours of nano and microfilled polymeric composite: effect of filler fraction and size. Mater Des 2014;61:50–60. [40] Salvador MV , Amigó V , Sahuquillo O, Antolinos CM, Segovia F, Vicente A, Sanz C. Thermal analysis of polymer resin matrix reinforced with E-glass fibers degradated in neutral environment. In: Proceedings of 11th European conference on composite materials; 2004. [41] Saravana BD, Mohan KGC. Thermal properties of maize fiber reinforced unsaturated polyester resin composites. World Congress on Engineering, London, UK, 2013. [42] Mulinari DR, Baptista CARP, Souza JVC, Voorwald HJC. Mechanical properties of coconut fibers reinforced polyester composites. Proc Eng 2011;10:2074–9. [43] Bansal RK, Mittal J, Singh P. Thermal stability and degradation studies of polyester resins. J Appl Polym Sci 1989;37:1901–8.
Contents lists available at ScienceDirect
Materials and Design journal homepage: www.elsevier.com/locate/matdes
Technical Report
Synthesis and characterization of zinc oxide (ZnO) filled glass fiber reinforced polyester composites Nafisa Gull a, Shahzad Maqsood Khan a,⇑, Muhammad Azeem Munawar a, Muhammad Shafiq a, Farheen Anjum a, Muhammad Taqi Zahid Butt b, Tahir Jamil a a b
Department of Polymer Engineering & Technology, University of the Punjab, Lahore, Pakistan College of Engineering and Emerging Technologies, University of the Punjab, Lahore, Pakistan
a r t i c l e
i n f o
Article history: Received 15 May 2014 Accepted 20 November 2014 Available online 27 November 2014
a b s t r a c t This study aims at fabrication of zinc oxide (ZnO) filled glass fiber reinforced polyester (GFRP) composites with varying concentrations of filler and investigation of their mechanical and thermal behavior. In this study, ZnO was dispersed in polyester, and laminates were fabricated by hand lay-up technique followed by compression molding. Mechanical properties were determined by flexural strength analysis, impact strength and hardness testing whereas thermal stability by thermogravimetric analysis (TGA). Flexural strength of 3 wt.% ZnO filled GFRP composite was improved significantly (up to 62.12%) in comparison to unfilled composite. Hardness, impact strength and thermal stability have also been found increased gradually with increase in ZnO loading. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Composites are in use as a substitute of conventional structural materials (steel, wood, ceramics and metals) due to their improved strength at small specific weight [1–4]. They are extensively used worldwide because of their distinct characteristics such as low density, high rigidity, eminent strength, greater specific modulus and ability to be tailored for specific purposes [5–8]. They have also amplified applications in several engineering fields because of their competent mechanical properties, excellent impact characteristics, elevated strength to weight ratio, outstanding resistance to corrosion, improved compressive and tensile strength, low coefficient of thermal expansion and better fatigue resistance [9–11]. One of the substantial benefit which directs the research workers to concentrate on composites is their versatile range of tribological and mechanical properties that can be achieved using multiple types of reinforcements in different orientations with variable volume fractions [12]. A fiber reinforced polymer (FRP) composite material comprises of a polymer which acts as a matrix and a reinforcing material which is selected as per desired applications and properties [13]. In conventional FRP composite, fiber behaves as standard load carrying candidate while the matrix is used to transfer the load to fiber and to shield it from any defect [14]. Glass fiber is a widely ⇑ Corresponding author. Tel.: +92 0300 7152120. E-mail addresses: [email protected], [email protected] (S.M. Khan). http://dx.doi.org/10.1016/j.matdes.2014.11.021 0261-3069/Ó 2014 Elsevier Ltd. All rights reserved.
used reinforcing material due to its excellent corrosion resistance, weight saving, high impact, greater tensile strength and low cost [15–17]. It is commonly used with polymer matrices such as vinyl ester, epoxy resin, unsaturated polyester resin and isophthalic polyester resin [18]. To cope with some limitations of polymers like low stiffness and decreased strength, ceramic fillers are employed to improve their mechanical, tribological, thermal, physical and electrical characteristics [19–21]. Fillers infused in polymeric composites, not only minimize the cost of composite material but also execute the high performance demands and improve the quality of polymeric composite [22,23]. A major problem to use filler in polymeric composites is the aggregation of filler and stabilization of its dispersion. This problem is solved by mechanical agitation [24] and ultrasonication [17,25]. ZnO is inorganic filler and semiconductor material existing in a diversity of structures. It is extensively used due to its distinctive optical, electrical, photocatalytic, optioelectronic, antibacterial and dermatological properties [26,27]. ZnO addition in polymer material increases hardness, impact, flexural properties and thermal stability of composite materials [28]. A lot of research work has showed the potential improvement in performance and properties of fiberous composites in which different filler particles were integrated. Madugu and co-workers [29] indicated that by increasing the amount of iron filler in fiber–polyester composites, a significant improvement of 77.8%, 55.6% and 30% was observed in hardness, porosity and density values respectively; and a considerable decrease of 17.1% and 37.55% was found in impact energy and linear shrinkage respectively. Garay et al.
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[30] evaluated the effect of calcium carbonate on polyester fiber composite and concluded that it caused improved elastic modulus, short beam strength and hardness; while decreased flexural, tensile and impact strength. Moorthy and Manonmani [24] studied that 10 wt.% titanium oxide (TiO2) addition in fiber–polyester composite resulted in noticeable increase in tensile strength, impact strength, hardness and chemical resistance. However research toward ZnO influence on the mechanical and thermal properties of composites is still novel and work is in progress in this field. In this study, GFRP composites with 1–5 wt.% ZnO were fabricated by hand lay-up technique followed by compression molding. The effect of ZnO on thermal and mechanical performance of synthesized composites was investigated.
without using ZnO in polyester resin. The formulation of various composites is given in Table 1. 3. Characterization 3.1. Flexural strength
2. Experimental details
Universal Testing Machine (UTM) Testometric UK Model Number FS100 CT with 100 KN load cell was used to determine the flexural properties under three-point bending configuration. Five individual samples (with dimensions of 127 14.5 2.5 mm as per ASTM) for all compositions were prepared according to ASTM: D790-10 to measure flexural strength and modulus. A span of 80 mm, containing a span to depth ratio 32:1, was used. The samples were positioned in the middle of the supports. UTM was operated at a speed of 1.0 mm/min at ambient temperature conditions.
2.1. Materials
3.2. Impact strength
E-glass roving strand mat was obtained from Taishan Fiberglass Inc., China. ZnO (melting point 1970 °C and 5.58 g/cm3 density) was purchased from Merck, Germany. Unsaturated polyester resin (with 42% styrene contents and 3% fumed silica flash point 35 °C, density: 1.11–1.23 g/cm3), Methyl ethyl ketone peroxide (MEKP) and Cobalt Naphthanate were purchased from local commercial market and were used in this study without any pre-treatment.
Pendulum Impact Tester Model CSI-137 of Custom Scientific Instruments (CSI) USA was used to determine the impact strength of fabricated composites. The impact strength of specimens was determined according to ASTM: D256-10 in Izod mode. Five individual samples (with dimensions of 63.5 12.7 2.5 mm) were prepared for impact testing and notched as per ASTM. 3.3. Hardness
2.2. Method 2.2.1. Dispersion of zinc oxide in polyester resin ZnO was dispersed in polyester matrix in different compositions (1–5 wt.%) using high speed disperser at 1000 rpm for 30 min. 2.2.2. Preparation of composite laminates Hand lay-up processing technique was used for composite formation. 1% MEKP catalyst was added to the prepared dispersion of ZnO filled polyester resin and stirred for 2 min. It was followed by addition of 0.5% Cobalt Naphthanate accelerator to initiate the curing of polyester resin prior to reinforcement. The mixture was stirred to mix the catalyst and initiator in the matrix. Four layers of cross plied woven roving glass fiber mat with dimensions of 178 mm 178 mm 20 mm were placed separately on aluminum foil at work table and ZnO filled polyester resin was poured on these layers uniformly. Finally, these layers were stacked on one another and were wrapped in aluminum foil. 2.2.3. Processing of composite materials The composite laminates were processed by hot compression molding technique. The mold of High Temperature Melt Press was made up of stainless steel having size of 178 mm 17 8 mm 20 mm. These composite laminates were placed in melt press under pressure of 2.844 psi at 80 °C for 1 h to obtain uniform thickness. Composite was post cured under same pressure for 1 h and was cooled to 60 °C and was removed out of the mold as final product. Control sample of GFRP composite was also fabricated
Table 1 Formulation of composites with different wt.% of filler. Sr. No.
Matrix content (wt.%)
Fiber contents (wt.%)
Zinc oxide (wt.%)
1 2 3 4 5 6
50 50 50 50 50 50
50 50 50 50 50 50
0 1 2 3 4 5
Hardness of samples (with dimension of 25.4 25.4 2.5 mm) was determined using a Bench Rockwell Hardness Tester Model NR3-DR Ernst Switzerland following ASTM: D785-08. A carbide ball indenter with spherical base of 2.5 mm diameter was penetrated into the material under applied load F. Preload was 1000 kp while applied load was 62.5 kp with ratio HB10. Brinell hardness was noted at ten different places on the specimen. 3.4. Thermogravimetric analysis (TGA) Simultaneous Differential Scanning Calorimeter Thermogravimetric Analyzer (SDT) Model Q600 of TA Instrument USA was used to perform TGA of fabricated composites. Thermal behavior of each sample (10 mg) was noted by heating across a temperature range of 30–800 °C, at heating rate of 10 °C/min in nitrogen environment. 4. Results and discussion 4.1. Flexural properties Flexural tests were conducted to examine the flexural strength and bulk stiffness of unfilled and ZnO filled GFRP composites. Figs. 1 and 2 show the changes in flexural strength and flexural modulus respectively due to ZnO contents on GFRP composites. Flexural strength was observed to be higher for ZnO filled GFRP composite than unfilled specimen. Plot of flexural strength vs. ZnO content (%) (Fig. 1) shows an initial increase in flexural strength of GFRP composite up to 3 wt.% of ZnO content followed by a decreasing trend. It has been observed that 3 wt.% is the optimal concentration for ZnO to be incorporated in GFRP composite. In flexural strength test, sample is positioned in the middle of the supports and force is applied from top of the sample. During this phenomenon, top layer of sample endures the compression while bottom layer goes through tensile loading. When the interfacial adhesion between matrix, fiber and filler increases, flexural strength increases. This strong adhesion transfers load from one end of the sample to other end which ultimately increases flexural strength. When concentra-
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72 66
65
58
60
56
50
40
4.3. Hardness 30
25 20 0
1
2
3
4
5
ZnO Content (%) Fig. 1. Flexural strength of ZnO filled composites.
10175
10000
Flexural Modulus (MPa)
9116
8874
8000
6806 6000
4.4. Thermogravimetric analysis (TGA)
4000
2000
The Brinell Hardness Value (BHV) of different composite materials with different weight percentages of ZnO is shown in Fig. 4. The hardness of composite materials has been observed to be increased gradually with increasing weight percentage of ZnO. For sample having 1 wt.% of ZnO, the hardness value was 131 BHV in comparison to 197 BHV while for 5 wt.% of ZnO filled GFRP composite, which is increased up to 48%. The reason behind resistance in penetration or increased hardness is ascribed to the fact that when compression stress is applied on the sample; matrix, fiber and filler are pressed simultaneously and contacted with each other more significantly. Therefore, interface will transfer pressure more effectively although the interfacial bond may be weak [33,37,38]. It is also due to increase in adhesion between matrix and reinforcements and reduced porosity due to addition of ZnO. As with increasing filler concentration in FRP composites, the inter particle distance is decreased which results in increased hardness [35,39].
3494 1947
0
1
2
3
4
5
ZnO Content (%) Fig. 2. Flexural modulus of ZnO filled composites.
tion of filler exceeds the optimum value, surface area increases but weight percentage of matrix contents decreases. This weakens bonding strength and load is not transferred uniformly throughout the specimen which results in decrease of flexural strength of composites. Also higher concentration of ZnO filler disturbs the continuity of matrix indicating poor adhesion between matrix, fiber and filler particles [31,32]. Decreasing trend is also imputed by the formation of aggregates of ZnO particles in different regions of polyester matrix when added in large amount. These aggregates of filler do not strongly interact with reinforcement and filler materials after a specific concentration resulting in the decrease of flexural strength of composites [17]. 4.2. Izod impact test The strength, weight fraction and orientation of filler affect the impact strength of fiber reinforced composite considerably. In this study, the orientation of glass fiber was kept constant in all samples and behavior of Izod impact strength was recorded with different filler contents. A significant improvement of the order of about 40% in impact strength is observed with the increase in filler loading up to 5 wt.% as shown in Fig. 3. Major factors which affect
TGA behavior of unfilled and ZnO filled GFRP composite was recorded to estimate the thermal stability of specimens (Fig. 5). During TGA, weight of the analyzed material decreased due to the decomposition or volatilization while increase in weight occurs due to the gas absorption or some chemical reaction [40]. Thermal decomposition profile of ZnO filled glass fiber reinforced polyester composites shows the weight loss in different steps. The weight loss in temperature range of 30–130 °C is attributed to the elimination of moisture and bound water gradually from composite materials [41,42]. The second phase weight loss with highest decomposition rate is associated with scission of weak bonds and unzipping of
0.55
Izod Impact Strength (J/m)
Flexural Strength (MPa)
70
the impact strength of composites are interfacial adhesion between matrix and inorganic filler, matrix fracture and fiber pullout [33,34]. Devendra and Rangaswamy and Jena et al. demonstrated that the impact energy values of GFRP composite increases with inclusion of filler is due to the improvement in bonding strength among inorganic filler, matrix and fiber. Thus ZnO filled GFRP composites has ability to absorb more energy, has greater fracture strength as compared to simple GFRP composite without filler and hence can stop crack propagation [35,36]. The behavior of impact test in present study depicts that ZnO will be promising filler in future composites.
0.54 0.49
0.50
0.46 0.45
0.41 0.40
0.38
0.35
0.32 0.30 0
1
2
3
4
ZnO Content (%) Fig. 3. Izod impact strength of ZnO filled composites.
5
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197
Brinell Hardness Values (BHV)
200
182 180
160
155
160
Acknowledgment 140
We are grateful for Department of Polymer Engineering & Technology, University of the Punjab, Lahore, Pakistan for help in completion of this research regarding all aspects of synthesis and characterization.
131 120
117 0
1
2
3
4
Appendix A. Supplementary material
5
ZnO Content (%)
Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.matdes.201 4.11.021.
Fig. 4. Brinell hardness values of ZnO filled composites.
0% ZnO 1% ZnO 2% ZnO 3% ZnO 4% ZnO 5% ZnO
100 90
Weight Loss (%)
Impact energy is enhanced gradually by increasing the filler concentration in fiber reinforced composites. Hardness also shows similar increasing behavior. Degradation temperature of ZnO filled composite has been found increased but amount of residue decreased up to 3 wt.%. Beyond this concentration negative effect was observed. Hence, it is concluded that ZnO is a promising filler for GFRP composite as it is responsible for the incremental modification in its mechanical and thermal behavior.
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References
70 60
50 40 0
100
200
300
400
500
600
700
800
900
0
Temperature ( C) Fig. 5. Thermogravimetric analysis of ZnO filled composites.
highly strained cross links resulting in the formation of straight chains. Then linear polymer backbone chain decomposed into small fragments at higher temperature [16,43]. The residue after 800 °C is attributed to the left behind amount of glass fiber and ZnO filler after the entire burning of polyester matrix. Slight improvement in degradation temperature was observed up to 3 wt.% of ZnO incorporation after which decreasing trend was noted. Weight loss was less for 3 wt.% ZnO filled GFRP composite compared to the unfilled sample. This is due to the fact that filler is preventing the movement of molecular chains of polyester at higher temperature, thus minimizing the weakening of the interface between filler and matrix. This finding is in accordance with the study by Hossain and co-workers [25]. It was determined from this analysis that the 3 wt.% of ZnO showed the weight loss up to 47.71% which was increased up to 49.79% for 4 wt.% of ZnO. 5. Conclusion It is evident from this study that mechanical and thermal properties of GFRP composite are improved with incorporation of ZnO filler. Flexural modulus and flexural strength are enhanced by raising the filler loading up to 3 wt.% of ZnO and then decreased.
[1] Kim HG, Lee DG. Dielectric cure monitoring for glass/polyester prepreg composites. Compos Struct 2002;57:91–9. [2] Sul JH, Prusty BG, Ray T. Prediction of low cycle fatigue life of short fibre composites at elevated temperatures using surrogate modelling. Compos B 2011;42:1453–60. [3] Sakin R, Ay I. Statistical analysis of bending fatigue life data using Weibull distribution in glass–fiber reinforced polyester composites. Mater Des 2008;29:1170–81. [4] Guades E, Aravinthan T, Islam MM. Characterisation of the mechanical properties of pultruded fibre-reinforced polymer tube. Mater Des 2014;63:305–15. [5] Devendra K, Rangaswamy T. Evaluation of thermal properties of E-glass/epoxy composites filled by different filler materials. Int J Comput Eng Res 2012;2(5):1708–14. [6] Idicula M, Boudenne A, Umadevi L, Ibos L, Candau Y, Thomas S. Thermophysical properties of natural fibre reinforced polyester composites. Compos Sci Technol 2006;66:2719–25. [7] Sakin R, Ay I, Yaman R. An investigation of bending fatigue behavior for glass– fiber reinforced polyester composite materials. Mater Des 2008;29:212–7. [8] Shokrieh MM, Saeedi A, Chitsazzadeh M. Evaluating the effects of multi-walled carbon nanotubes on the mechanical properties of chopped strand mat/ polyester composites. Mater Des 2014;56:274–9. [9] Sutherland LS, Soares CG. Effects of laminate thickness and reinforcement type on the impact behaviour of E-glass/polyester laminates. Compos Sci Technol 1999;59:2243–60. [10] Rajamurugan TV, Shanmugam K, Palanikumar K. Analysis of delamination in drilling glass fiber reinforced polyester composites. Mater Des 2013;45:80–7. [11] Yao XF, Kolstein MH, Bijlaard FSK, Xu W, Xu M. Tensile strength and fracture of glass fiber-reinforced plastic (GFRP) plate with an eccentrically located circular hole. Polym Test 2003;22:955–63. [12] El-Sayed AA, El-Sherbiny MG, Abo-El-Ezz AS, Aggag GA. Friction and wear properties of polymeric composite materials for bearing applications. Wear 1995;184:45–53. [13] Pihtili H. An experimental investigation of wear of glass fibre–epoxy resin and glass fibre–polyester resin composite materials. Eur Polym J 2009;45:149–54. [14] Nirmal U, Low KO, Hashim J. On the effect of abrasiveness to process equipment using betelnut and glass fibres reinforced polyester composites. Wear 2012;290–291:32–40. [15] Mohebby B, Fallah-Moghadam P, Ghotbifar AR, Kazemi-Najafi S. Influence of maleic-anhydride-polypropylene (MAPP) on wettability of polypropylene/ wood flour/glass fiber hybrid composites. J Agric Sci Technol 2011;13:877–84. [16] López FA, Martín MI, Alguacil FJ, Rincón JM, Centeno TA, Romero M. Thermolysis of fibreglass polyester composite and reutilisation of the glass fibre residue to obtain a glass–ceramic material. J Anal Appl Pyrol 2012;93:104–12. [17] Hossain MK, Hossain ME, Hosur MV, Jeelani S. Flexural and compression response of woven E-glass/polyester–CNF nanophased composites. Compos A 2011;42:1774–82. [18] Tanoglu M, Seyhean AT. Investigating the effects of a polyester preforming binder on the mechanical and ballistic performance of E-glass fiber reinforced polyester composites. Int J Adhes Adhes 2003;23:1–8. [19] Sahu H, Rout A, Kumar A. Development and characterization of particulate filled glass fiber reinforced hybrid composites. Int J Mech Ind Eng 2012;2(3):89–93.
N. Gull et al. / Materials and Design 67 (2015) 313–317 [20] Detomi AC, Santos RMD, Filho SLMR, Martuscelli CC, Panzera TH, Scarpa F. Statistical effects of using ceramic particles in glass fibre reinforced composites. Mater Des 2014;55:463–70. [21] Raja RS, Manisekar K, Manikandan V. Study on mechanical properties of fly ash impregnated glass fiber reinforced polymer composites using mixture design analysis. Mater Des 2014;55:499–508. [22] Sathiyamurthy S, Thaheer ASA, Jayabal S. Prediction and optimization of mechanical properties of particles filled coir–polyester composites using ANN and RSM algorithms. Indian J Fiber Textile Res 2013;38:81–6. [23] Fu S-Y, Feng X-Q, Lauke B, Mai Y-W. Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites. Compos B 2008;39:933–61. [24] Moorthy SS, Manonmani K. Fabrication and characterization of TiO2 particulate filled glass fiber reinforced polymer composite. Mater Phys Mech 2013;18:28–34. [25] Hossain MK, Hossain ME, Dewan MW, Hosur M, Jeelani S. Effects of carbon nanofibers (CNFs) on thermal and interlaminar shear responses of E-glass/ polyester composites. Compos B 2013;44:313–20. [26] Loto CA. The foundation and the fundamental pillar of world technological civilization and economic development. Public Lecture Ser 2007;1(17). [27] Yahya N, Puspitasari P, Latiff NRA. Hardness improvement of dental amalgam using zinc oxide and aluminum oxide nanoparticles. Charact Dev Biosyst Biomater Adv Struct Mater 2013;29:9–32. [28] Hong JI, Winberg P, Schadler LS, Siegel RW. Dielectric properties of zinc oxide/ low density polyethylene nanocomposites. Mater Lett 2005;59:473–6. [29] Madugu IA, Abdulwahab M, Aigbodion VS. Effect of iron fillings on the properties and microstructure of cast fiber–polyester/iron filings particulate composite. J Alloys Compd 2009;476:807–11. [30] Garay AC, Heck V, Zattera AJ, Souza JA, Amico SC. Influence of Calcium Carbonate on RTM and RTM light processing and properties of molded composites. J Reinf Plast Compos 2011;30(14):1213–21. [31] Kaundal R, Satapathy PatnaikA. A comparison of the mechanical and thermomechanical properties of unfilled and SiC filled short glass polyester composites. Silicon 2012;4:175–88.
317
[32] Agarwal G, Patnaik A, Sharma RK. Thermo-mechanical properties of silicon carbide-filled chopped glass fiber-reinforced epoxy composites. Int J Adv Struct Eng 2013;5(21):1–8. [33] Kaundal R, Patnaik A, Satapathy A. Effect of SiC particulate on short glass fiber reinforced polyester composite in erosive wear environment. Walailak J Sci Technol 2012;9(1):49–64. [34] Fu S-Y, Feng X-Q, Lauke B, Mai Y-W. Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites. Composites Part B 2008;39:933–61. [35] Devendra K, Rangaswamy T. Strength characterization of E-glass fiber reinforced epoxy composites with filler materials. J Miner Mater Charact Eng 2013;1:353–7. [36] Jena H, Pandit MK, Pradhan AK. Study the impact property of laminated bamboo–fibre composite filled with cenosphere. Int J Environ Sci Dev 2012;3(5):456–9. [37] Raju BR, Swamy RP, Suresha B, Bharath KN. The effect of silicon dioxide filler on the wear resistance of glass fabric reinforced epoxy composites. Adv Polym Sci Technol: An Int J 2012;2(4):51–7. [38] Mohapatra S, Mantry S, Singh SK. Performance evaluation of glass–epoxy–TiC hybrid composites using design of experiment. J Compos 2014;2014:1–9. [39] Antunes PV, Ramalho A, Carrilho EVP. Mechanical and wear behaviours of nano and microfilled polymeric composite: effect of filler fraction and size. Mater Des 2014;61:50–60. [40] Salvador MV , Amigó V , Sahuquillo O, Antolinos CM, Segovia F, Vicente A, Sanz C. Thermal analysis of polymer resin matrix reinforced with E-glass fibers degradated in neutral environment. In: Proceedings of 11th European conference on composite materials; 2004. [41] Saravana BD, Mohan KGC. Thermal properties of maize fiber reinforced unsaturated polyester resin composites. World Congress on Engineering, London, UK, 2013. [42] Mulinari DR, Baptista CARP, Souza JVC, Voorwald HJC. Mechanical properties of coconut fibers reinforced polyester composites. Proc Eng 2011;10:2074–9. [43] Bansal RK, Mittal J, Singh P. Thermal stability and degradation studies of polyester resins. J Appl Polym Sci 1989;37:1901–8.