Property Improvements of an Epoxy Resin by Nanosilica Particle Reinforcement for Tribological Applications
SUBMISSION OF MINOR PROJECT FOR THE DEGREE OF
BACHELOR OF TECHNOLOGY in
Mechanical Engineering By SACHIN CHAINTHA (06305)
AMAN CHANDEL (06318)
SAURABH GUPTA (06315)
ASHWANI THAKUR (06317)
Under the Guidance of Dr. AMAR PATNAIK
Department of Mechanical Engineering
Department of Mechanical Engineering National Institute of Technology Hamirpur April. 2009 1
Property Improvements of an Epoxy Resin by Nanosilica Particle Reinforcement for Tribological Applications
1. Introduction
Fibre reinforced polymer composites have many applications as a class of structural materials because of their ease of fabrication, relatively low cost and superior mechanical properties compared to polymer resins. A pre-requisite of most structural/engineering materials is that they have good stiffness and strength along with adequate toughness. Composites reinforced with man-made fibers like glass fibers usually fulfill this requirement, especially since they exhibit crack-stopping capability which makes them very attractive for structural or semi-structural applications. However, natural fiber reinforced materials have inferior mechanical and wear-resistance properties than conventional
glass-fibre
reinforced
composites.
In
order
to
overcome
these
disadvantages, several treatments have been proposed in the literature [1–4]. In spite of this, in recent years, there is an increasing interest in natural fibers as substitutes for glass fibers mainly because of their low specific gravity, low cost, as well as their renewable and biodegradable nature [5]. Among the naturally available fibers again, there has been a growing demand, more specifically, for the use of ligno-cellulosic fibers (derived from plant leaf or bark) as reinforcing elements in polymeric matrix [6-10]. Several types of natural fibres which are abundantly available like sisal, jute, coir, oil palm, bamboo, wheat and flax straw, waste silk, banana have proved to be good and effective reinforcement in the thermoset and thermoplastic matrices [11-19]. Sugarcane fibres are long plant fibres, like hemp, flax [20-22], and bamboo [16,17] that have considerable potential in the the manufacture of composite materials. Natural fibre-reinforced fibre-reinforced polymers exhibit very different wear properties, mechanical performances and environmental aging resistances depending on their inter-phase properties, but most studies available in the existing literature have been dedicated to fibre surface treatment [1-5]. And although reinforcement of these natural fibers has long been an attractive option in composite making, the potential of pine bark, as a reinforcing fiber has not been explored so far. Hence the present work is undertaken to investigate exclusively the tensile, flexural as well as the wear behaviour of this plant fibre (pine bark) reinforced composite. The
2
Himalayan subtropical pine forests are renowned for being the largest in the whole of Indo-Pacific areas. Various types of pine trees are found in this region; especially in Himachal Pradesh, wide ranging tracts of Chir Pine are seen. The scientific name of Chir Pine is Pinus is Pinus roxburghii. Over the years these forests have faced several threats from the modern day society. Overgrazing, cultivation, exploitation for fuel woods etc have brought about degradation of this eco region. Hence, there is an urgent need for plantation, preservation of this natural wealth and its utilization with great care and sensibility. Surprisingly, publications concerning the tribological behaviour of natural fiber reinforced polymers are rare in the tribology literature. Only few articles were concentrated on the use of sugarcane bagasse to reinforce low cost composites [23], and to reinforce cement composite [24]. Furthermore, a series of researches was focused on the study of abrasive wear behaviour of bamboo fibres [16-17, 25-28]. The work by ElTayeb [29] reports the adhesive behaviour of sugarcane reinforced polymer composites as compared to that of glass reinforced polymer composites. It is strange that despite the interest and environmental appeal of plant fibres, their use has been limited mostly to non-tribological applications. It may be due to their lower strength and stiffness compared with synthetic fiber reinforced polymer composites. However, the stiffness and strength shortcomings of bio-composites can be overcome by structural configurations and better arrangement in a sense of placing fibers in specific locations for highest strength performance and also by hybridization of the composites. Composites having two or more fillers contained in the same matrix are called hybrid composites [30,31]. Recently there is a growing interest in hybridizing different natural fibers in order to produce high performance composite materials. Against this background, the present investigation is undertaken to develop a new kind of hybrid composite consisting of pine-bark fibers as the reinforcement, cement-kiln-dust as the particulate filler and polyester as the matrix. Short fibers in the form of flakes of pine tree barks, which are abundantly available in the Himalayan valley in northern India are reinforced in polyester resin filled with a fixed quantity of cement kiln dust to prepare the composites. The cement kiln dust is a by-productof by-product of the manufacture of Portland cement. It is generated during the calcining process in the kiln. Apart from CaO, that constitutes
3
roughly 60 % of the dust, other compounds present in it include SiO2, Al2O3, Fe2O3, K 2O, –
Na2O, Cl , etc. The present work thus involves the development of this new class of particle filled plant fiber reinforced composites and reports on their sliding wear characteristics. Such multi-component hybrid composites form complex systems and there is inadequate research reported on their wear characteristics. To study the correlation between the wear properties and the characteristic parameters, e.g., the composition of the composite and the operating conditions is of prime importance for designing proper composites in order to satisfy various functional requirements. But visualization of impact of any individual control factor in an interacting environment really becomes difficult. To this end, an attempt has been made in this study to analyze the impact of more than one parameter on abrasive wear behavior of the epoxy based nanosilica filled composites. It is important as in actual practice the resultant wear rate is the combined effect of more than one interacting variable. An inexpensive and easy-tooperate experimental strategy based on Taguchi’s parameter design has been adopted to study the effect of various parameters and their interactions. This experimental procedure has been successfully applied for parametric appraisal in the wire electrical discharge machining (WEDM) process, drilling of metal matrix composites, and erosion behavior of polymer–matrix composites [32-37]. 2. Identified Research Gaps
At present, the incorporation of the SiO2, particles in a polymer matrix on a nanoscale level is a major challenge in this field. The formation of agglomerates which is observed in composites prepared by conventional techniques can deteriorate the final properties of the product. To overcome this problem, the sol-gel process for incorporating nanosilica particles into a reactive epoxy resin may try in the works presented here. By this process, inorganic or inorganic-organic materials can be produced from liquid starting materials via a low temperature process. By employing chemical methods, nanoparticles can be produced elegantly and free of agglomerates. The major challenge is to transfer these nanosilica particles from the aqueous medium into the prepolymer of a reactive epoxy ep oxy resin without affecting the particle distribution. In the liquid process, toxicological problems during handling of the pure nanoparticle substances do not exist or can be eliminated at the initial stage. The incorporation of
4
nanosilica particles also aims at a low shrinkage upon curing because this improves the toughness and ductility of the cured products and also prevents debonding of the casting compound from the matrix. The special nano-scaled design of the particles is the key to a property enhancement. The silica phase consists of surface-modified, synthetic SiO2, nanospheres with diameter of less than 50 nm and extremely narrow size distribution. 3. Specific objectives of this project work up to eight semesters
Keeping in view of the magnitude of the problem, current status of research and preliminary findings based on some of the commercial composites the following objectives are set in the scope of o f the present project work. •
Development of methods for the efficient fabrication of the SiO2 particles in a polymer matrix on a nanoscale level.
•
The formation of agglomerates which is observed in composites prepared by conventional techniques can deteriorate the final properties of the product or not.
•
To overcome this problem, the sol-gel process for incorporating nanosilica particles into a reactive epoxy resin may try in the works presented here.
•
By this process, inorganic or inorganic-organic materials can be produced from liquid starting materials via a low temperature process. By employing chemical methods, nanoparticles can be produced elegantly and free of agglomerates.
•
Study on Structural and Mechanical Analysis of the composites. Structural properties such as: Microstructure, Viscosity Studies of the Unfilled and Filled Resin and Mechanical Properties like Three-Point Bending, Micro-hardness, Fracture Toughness.
•
Study on the tribological properties of the prepared composites and their failure analysis (fracture surface).
4. Proposed Methodology
1. The raw materials needed for this work are epoxy resin, E-glass fibers and incorporation of SiO2 particle under different weight percentage. These are to be procured from different firms. 2. Composite slabs will be fabricated using injection molding technique following prescribed norms for loading and curing. Specimens for various characterization tests will be made as per required dimensions using a diamond cutter.
5
3. Friction and dry wear test will be carried out using abrasive wear test rig. Wear rate will be calculated on ‘mass loss’ basis under different operating conditions. Real time wear situations will be simulated by varying va rying the control factors such as: sliding velocity, normal load, erodent size, sliding distance etc. The influence of each factor on the material loss will be studied in an interacting environment. For this, the experimental schedule will be designed as per Taguchi’s methodology. This will lead to identify significant factors and the relative significance of their interactions. 4. The eroded samples will be examined under scanning electron microscope to get an insight to the damage mechanism as a result of solid particle impact. 5. Experimental details 5.1. Specimen preparation
Glass fiber are reinforced epoxy resin composite mixed with nano-silica powder with different weight percentage. The composites are cast by conventional hand-lay-up 2
technique so as to get square specimens (120x120 mm ). Composites of five different compositions (0 wt%, 4 wt%, 8 wt% and 12 wt% of nanoSiO2) are made with the weight fraction of glass fiber kept fixed (50 wt%) for all samples. Its common name is Bisphenol-A-Diglycidyl-Ether and it chemically belongs to the ‘epoxide’ family. The epoxy resin and the hardener are supplied by Ciba Geigy India Ltd. E-glass fiber and epoxy resin have modulus of 72.5 GPa and 3.42GPa respectively and possess density of 3
3
2590 kg/m and 1100 kg/m respectively. The composite slabs are made by conventional hand-lay-up technique followed by light compression moulding technique. A stainless 3
steel mould having dimensions of 210 × 210 × 40 mm is used. A releasing agent (Silicon spray) is used to facilitate easy removal of the composite from the mould after curing. The low temperature curing epoxy resin and corresponding hardener (HY951) are mixed in a ratio of 10:1 by weight as recommended. The mix is stirred manually to disperse the fibres in the matrix. Care is taken to ensure a uniform sample since fibres have a tendency to clump and tangle together when mixed. The cast of each composite is cured under a load of about 50kg for 24 h before it removed from the mould. Then this cast is post cured in the air for another 24 h after removing out of the mould. Specimens of suitable dimension are cut using a diamond cutter for physical characterization and
6
mechanical testing. Utmost care has been taken to maintain uniformity and homogeneity of the composite. 5.2. Abrasive wear test
The schematic representation of rubber wheel test set up is shown in Figure 1. In the present study, silica sand (density 2.6 g/cm3) is used as the abrasive. The abrasive particles of AFS 60 grade silica sand were angular in shape with sharp edges. The shape of the silica sand used for abrasive wear study is shown in Figure 2. The abrasive is fed at the contacting face between the rotating rubber wheel and the test sample. The tests were conducted at a rotational speed of 100 rpm. The rate of feeding the abrasive is 255±5 g/min. The sample is cleaned with acetone and then dried. Its initial weight is determined in a high precision digital balance (0.1mg accuracy) before it is mounted in the sample holder. The abrasives were introduced between the test specimen and rotating abrasive wheel composed of chlorobutyl rubber tyre (hardness: Durometer-A 58-62). The diameter of the rubber wheel used is 228 mm. The test specimen is pressed against the rotating wheel at a specified force by means of lever arm while a controlled flow of abrasives abrades the test surface. The rotation of the abrasive wheel is such that its contacting face moves in the direction of sand flow. The pivot axis of the lever arm lies within a plane, which is approximately tangent to the rubber wheel surface and normal to the horizontal diameter along which the load is applied. At the end of a set test duration, the specimen is removed, thoroughly cleaned and again weighed (final weight). The difference in weight before and after abrasion is determined. At least three tests were performed and the average values so obtained were used in this study. The wear rate is measured by the loss in weight, which is then converted into specific wear rate using the measured density data. The specific wear rate (WS) is calculated from the equation: WS = Δm/ρt VS.F N
(1)
where Δm is the mass loss in the test duration (gm) 3
ρ is the density of the composite (gm/mm )
t is the test duration (sec). Vs is the sliding velocity (m/sec) F N is the average normal load (N).
7
The specific wear rate is defined as the volume loss of the specimen per unit sliding distance per unit applied normal load. Abrasive hopper
Nozzle
. .. . .. . . .. . . . .. . . .. . . . . . . . . . . . . . .. .
Abrasive particles
Normal load
Rubber wheel Steel disc
Sample holder
.. Composite sample
.. . .. . . . . .. . . .. . .. .... ..
..
.. . .. .
Particle collecting bag
Figure 1. Schematic diagram of abrasive jet machine
5.3. Experimental design
Taguchi experimental design is a powerful analysis tool for modeling and analyzing the influence of control factors on performance output. This method achieves the integration of design of experiments (DOE) with the parametric optimization of the process yielding the desired results. The orthogonal array (OA) requires a set of well-balanced (minimum experimental runs) experiments. Taguchi’s method uses a statistical measure of performance called signal-to-noise ratio (S/N), which is logarithmic function of desired output to serve as objective functions for optimization. The S/N ratio considers both the mean and the variability into account. It is defined as the ratio of the mean (signal) to the standard deviation (noise). The ratio depends on the quality characteristics of the product/process to be optimized. The three categories of S/N ratios are used: lower the better (LB), higher-the-better (HB) and nominal-the best (NB). The experimental observations are transformed into a signal-to-noise (S/N) ratio. There are several S/N
8
ratios available depending on the type of characteristics. The S/N ratio for minimum erosion rate coming under smaller is better characteristic can be calculated as logarithmic transformation of the loss function as shown below Smaller is the better characteristic:
(2)
where ‘n’ the number of observations, and y the observed data. The most important stage in the design of experiment lies in the selection of the control factors. Exhaustive literature review on erosion behavior of polymer composites reveal that factors viz., impact velocity, filler content, erodent temperature, impingement angle, stand-off distance and erodent size etc largely influence the erosion rate of polymer composites [18]. Hence in the present work the impact of these five parameters are 5
studied using L16 (4 ) orthogonal design. In conventional full factorial experiment design, 5
it would require 4 = 1024 runs to study five factors each at four levels whereas, Taguchi’s factorial experiment approach reduces it to only 16 runs offering a great advantage in terms of experimental time and cost. The operating conditions under which erosion tests are carried out are given in Table 1. The tests are conducted as per experimental design given in Table 2 in which each column represents a test parameter whereas a row stands for a treatment or test condition which is nothing but combination of parameter levels [19]. The plan of the experiments is as follows: the first column is assigned to sliding velocity (A), the second column to normal load (B), the third column to nano-silica content (C), the fourth column to sliding distance (D) and the fifth column to erodent size (E), respectively to estimate specific wear rate. Table 1. Levels of the variables used in the experiment Control factor Level I II III A: Sliding velocity 60 120 180 B: Normal load 10 20 30 C: Fly ash content 75 70 65 D: Sliding distance 500 1000 1500 E: Erodent size 200 300 400
9
IV 240 40 60 2000 500
Units cm/sec N % m µm
Table 2. Orthogonal array for L16 (45) Taguchi Design Expt. No. A B C 1 1 1 1 2 1 2 2 3 1 3 3 4 1 4 4 5 2 1 2 6 2 2 1 7 2 3 4 8 2 4 3 9 3 1 3 10 3 2 4 11 3 3 1 12 3 4 2 13 4 1 4 14 4 2 3 15 4 3 2 16 4 4 1
D 1 2 3 4 3 4 1 2 4 3 2 1 2 1 4 3
E 1 2 3 4 4 3 2 1 2 1 4 3 3 4 1 2
6. Expected out come of this project work as:
The most important benefits expected from the nanosilica reinforcement are the following: (i) lower viscosity of the resin formulation compared to common reinforcing fillers and a complete suppression of sedimentation, (ii) increased fracture toughness, impact strength, and modulus, (iii) improved scratch- and abrasion-resistance, (iv) reduced shrinkage upon curing and reduction of the coefficient of thermal expansion, (v) improved dielectric properties, (vi) improvement of heat distortion, chemical resistance, glass transition temperature, durability and weathering stability, (vii) no adverse influence on the processing characteristics of the basic resin The following section deals with the exact description of the preparation of nanosilica-reinforced epoxies by the solgel technique, and of the relation of their structure to various rheological, mechanical, and tribological properties.
10
7. Road Map for project Work: Time period Up-to Sixth Sem. Jan-Mar-2009
Up-to Seventh Sem.
ay-2009 Jun-sept-09
Oct-09
Nov-Dec-09
Up-to Eight Sem. Jan-Mar-09
Literature Survey: Sample preparation Results and Analysis: Calculation of erosion rate and exposure towards SEM. Microstructure Observations/Aspects: will be done for all the three samples in order to asses the rate of erosion and type of fracture. Mechanical Properties study Computer Simulation of thermal properties by Ansys8 software and compare with experimental results. Report writing and presentation
References
[1] Mehta G, Drzal LT, Mohanty AK, Misra M. (2005).Effect of fiber surface treatment on the properties of biocomposites from nonwoven industrial hemp fiber mats and Sci., 99(2):1055–1068. unsaturated polyester resin, J resin, J Appl Polym Sci., [2] Ray D, Sarkar BK, Bose N. (2002).Impact fatigue behaviour of vinylester resin A, 33(2): 233–41. matrix composites reinforced with alkali treated jute fibres, Composites A, [3] George J, Sreekala MS, Thomas S. (2001). A review on interface modification and characterization
of
natural
fiber
reinforced
plastic
composites, Polym
Eng
Sci., Sci.,41(9):1471–1485. [4] Gassan J, Bledzki AK. (1999). Possibilities for improving the mechanical properties of jute/epoxy composites by alkali treatment of fibres, Compos Sci Technol., 59(9): 1303– 1309. [5] Aziz SH, Ansel MP (2004).The effect of alkalization and fibre alignment on the mechanical and thermal properties of kenaf and hemp bast fibre composites: Part 1 – polyester resin matrix. Comp Sci Techol., 64:1219–1230. [6] Felix JM, Gatenholm P. The nature of adhesion in composites of modified cellulose fibers and polypropylene. J Appl Polym Sci 1991;42:609.
11
Up to end Sem
[7] Dalvag H, Klason C, Stromwall HE. Effects of cellulose fibers in polypropylene composites. Int J Polym Mater 1985;11:9. [8] Hamada H, Ikuta N, Nishida N, Maekaewa Z. Effect of interfacial silane network structure on interfacial strength in glass fibre composites. Composites 1994;25:512. [9] Belgacem MN, Bataille P, Sapieha S. Effect of corona modification on the mechanical properties of polypropylene/cellulose composites. J Appl Polym Sci 1994;53:397. [10] Eichhorn SJ, Baillie CA, Zafeiropoulos N, Mwaikambo LY, Ansell MP, Dufresne A, et al. Current international research into cellulosic fibres and composites. J Mater Sci 2001;36:2107. [11] Jacob, M., Thomas, S., Varughese, K.T., 2004. Mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber composites. J. Compos Sci. Technol. 64, 955–965. [12] Joseph, K., Thomas, S., Pavithran, C., 1996. Effect of chemical treatment on the tensile properties of short sisal fiber-reinforced polyethylene composite. Polymer 37, 5139–5145. [13] Joseph, S., Sreekalab, M.S., Oommena, Z., Koshyc, P., Thomas, S., 2002. A comparison of the mechanical properties of phenol formaldehyde composites reinforced with banana fibres and glass fibres. Compos. Sci. Technol. 62, 1857–1868. [14] Varma, I.K., Ananthakrishnan, S.R., Krishnamoorthi, S., 1989. Comp of glass/modified jute fabric and unsaturated polyester. Composites 20, 383. [15] Pothana, L.A., Oommenb, Z., Thomas, S., 2003. Dynamic mechanical analysis of banana fiber reinforced polyester composites. Compos. Sci. Technol. 63 (2), 283–293. [16] Tong, J., Arnell, R.D., Ren, L., 1998. Dry sliding wear behaviour of bamboo. Wear 221, 37–46. [17] Tong, J., Ma, Y., Chen, D., Sun, J., Ren, L., 2005. Effects of vascular fiber content on abrasive wear of bamboo. Wear 259, 37–46. [18] Hornsby, P.R., Hinrichsen, E., Traverdi, K., 1997. Preparation and properties of polypropylene composites reinforced with wheat and flax straw fibres. Part I. Characterisation. J. Mater. Sci. 32, 443–449.
12
[19] Pothan, L.A., Thomas, S., Neelakantan, N.R., 1997. Short banana fibre reinforced polyester composites: mechanical, failure and aging characteristics. J. Reinf. Plast. Compos. 16, 744. [20] Hepworth, D.G., Bruce, D.M., Vincent, J.F.V., Jeronimidis, G., 2000. The manufacture and mechanical testing of thermosetting natural fibre composites. J. Mater. Sci. 35, 293–298. [21] Hepworth, D.G., Hobson, R.N., Bruce, D.M., Farrent, J.W., 2000, The use of untreated hemp in composite manufacture. Composites. Part A 31, 1279–1283. [22] Joseph, P.V., Kuruvilla, J., Thomas, S., 2002. Short sisal fibre reinforced polypropylene composite: the role of interface modification on ultimate properties. Compos. Interf. 9 (2), 171–205. [23] Monteiro, S.N., Rodriquez, R.J.S., De Souza, M.V., 1998. Sugar cane bagasse waste as reinforcement in low cost composites. Adv. Perform. Mater. 5, 1 83–191. [24] Aggarwal, L.K., 1995. Bagasse-reinforced cement composites. Cement Concrete Compos. 17, 107–112. [25] Tong, J., Ren, L.Q., Li, J.Q., Chen, B.C., 1995. Abrasive wear behaviour of bamboo. Tribol. Int. 28, 323–327. [26] Yahou, T., Sakamoto, S., 1993. Abrasive properties of bamboo. Jpn. J. Tribol. 38, 491–497. [27] Chand, N., Dwivedi, U.K., 2007. High stress abrasive study on bamboo. J. Mater. Process. Technol. 183, 155–159. [28] Chand, N., Dwivedi, U.K., Acharya, S.K., 2007. Anisotropic abrasive wear behaviour of bamboo ( Dentrocalamus Dentrocalamus strictus). strictus). Wear 262 (9/10), 1031–1037. [29] El-Tayeb, N.S.M., 2007. A study on the potential of sugarcane fibers/polyester composite for tribological applications. Wear, doi:10.1016/j.wear.2007.10.006. [30] Pavithran C, Muckerjee PS, Brahmakumar M, Damodaran A. Mater Sci Lett 1987;7:882. [31] Hancox NL. Fibre composite hybrid materials. Macmillan Publishers; 1981. [32] Mahapatra SS, and Patnaik Amar (2006). Optimization of Wire Electrical Discharge Machining (WEDM) process Parameters using Taguchi Method, Int. J.Adv. Manuf. Technol . DOI.10.1007/s00170-006-0672-6 .
13
[33] Mahapatra SS., Patnaik Amar, Khan MS (2006). Development and Analysis of Wear Resistance Model for Composites of Aluminium Reinforced with Redmud, The journal of Solid Waste Technology and Management , 32 (1):28-35. [34] Patnaik Amar, Biswas Sandhyarani, Mahapatra SS, (2007). An Evolutionary Approach for Parameter Optimization of Submerged Arc Welding in Hard facing Process, International Process, International Journal of Manufacturing Research, Research, 2 (4): 462-483. [35]Mahapatra SS, Patnaik Amar, Satapathy Alok, Dash RR, (2007). Taguchi Method Applied to Parametric Appraisal of Erosion Behavior of GF-Reinforced Polyester Composites, Wear doi: Wear doi:10.1016/j.wear.2007.10.001 . [36] Patnaik Amar, Satapathy Alok, Mahapatra SS, Dash RR, (2007). A Modeling Approach for Prediction of Erosion Behavior of Glass Fiber- Polyester Composites, Journal of Polymer Research, doi: 10.1007/s10965-007-9154-2 . [37] Patnaik Amar, Satapathy Alok, Mahapatra SS, Dash RR, (2008). Modeling and Prediction of Erosion Response of Glass Reinforced Polyester-Flyash Composites, Journal of Reinforced Plastics and Composites, Composites, doi: 10.1177/0731684407085728 .
14
