International Journal of Pure and Applied Sciences and Technology

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), pp. 36-44 International Journal of Pure and Applied Sciences and Technology ISSN 2229-6107 Available online at www.ijopaasat.in Research Paper Polyamide/Clay Nanocomposites Film, Synthesis and Mechanical Testing S.S. Bhattacharya 1 and Aadhar Mandot 1,* 1 Department of Textile Engineering, Faculty of Technology & Engineering, The M.S. University of Baroda, Vadodara 390001, India * Corresponding author, e-mail: (aadharmandot@yahoo.com) (Received: 12-5-13; Accepted: 17-6-13) Abstract: An inorganic-polymer composite film was formed through nanosize clay filler particles that were incorporated inside a nylon-6 matrix. The montmorillonite clay was modified and converted to organoclay at laboratory in optimized condition. The Polyamide/Clay nanocomposite films were prepared by simple dissolution technique using different concentration of nanoclay. Morphology of composite film was examined with SEM which revealed that clay particles were well dispersed and non-aggregated. The film was also characterized by FTIR spectra and further analyzed by EDX. This composite film was evaluated for the change in their mechanical and thermal properties compared to the pure nylon-6 film. The increased tensile strength of the composite film was observed which was further supported by thermal analysis, which shows higher H value. Keywords: MMT, Mechanical properties, Nanocomposite film, Polyamide/nano clay, Thermal analysis. 1. Introduction: Polymer nanocomposites are the type of materials where inorganic fillers (having at least one dimension in nanometer range) are added to polymer matrix. The properties of a polymer reinforced composite are mostly influenced by its size, shape, composition, state of agglomeration and degree of matrix-filler adhesion [1-3]. Reducing the size of particle to nano range large surface area is created which enhances its properties dramatically and in all influences the macroscopic properties of the polymer. Applications of such composites are found in fields of optics, mechanics, flame retardants, etc. [4-6]. Polyamides, and in particular the nylon series of thermoplastics, constitute a family of compounds with exceptional mechanical properties [7, 8], which are widely used by the automotive

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 37 industry. However, the main challenge still remains in terms of incorporating nanoparticles inside the polymer matrix, as these particles try to agglomerate. The problem becomes more adverse during their higher concentration, prolong heating and mixing. In this study an attempt has been made to explore the feasibility of producing film from polyamide / clay nanocomposite. The montmorillonite clay was modified and converted to organoclay in laboratory as per the method described by Mansor et al. [9]. The Polyamide/Clay nanocomposite films were prepared by solvent dissolution technique where nanoclay concentration was varied in the range of 0.1 to 0.8% by weight. The characterization of prepared polyamide/clay nanocomposite film was done using, FTIR analysis, the thermal behavior was studied using Differential Scanning Calorimetric (DSC) analysis and the morphology was observed under scanning electron microscopy (SEM). The polyamide/clay films have also been evaluated for their mechanical properties. 2. Materials and Experimental Methods: 2.1 Materials Polyamide granules of moulding grade were supplied by Fairdeal filament and reagent grade formic acid was obtained from Durga chemicals. MMT organo clay was prepared in laboratory. 2.2 Experimental Methods 2.2.1 Preparation of Polyamide/Nanoclay Composite Film The polyamide/nanoclay composite film was prepared by a simple solvent dissolution technique. In an atmospheric condition nylon-6 of 10 gms was added to formic acid 100 ml and stirred for about 2 hrs until a clear solution immerged. The ph of the solution was tested with universal indicator and if necessary, lowered with a drop or two of concentrated aqueous HCL until finally ph 2 was reached. The MMT clay solution of different concentration (i.e 0.1, 0.5 and 0.8% on weight of granules, as shown in Table 1) was added to nylon solution and stirred gently (rapid stirring enhance aggregate formation) at room temperature for 2 hrs. The solution was then cast on to clear glass flat bottom petridis and the solvent evaporated under atmospheric condition. Further vacuum and heat (60 80 C) treatment formed dry, translucent composites consisting of organo clay and nylon-6. The composite films were compared with the film prepared without addition of MMT clay. Table 1- The composition of nanocomposites preparation by formic acid mixing Recipe S1 S2 S3 Organo clay (wt %) 0.1 0.5 0.8 Polyamide (g) 10 10 10 Formic acid (ml) 100 100 100 2.3 Testing and Analysis 2.3.1 Characterization of Film The dispersion of clay nanoparticles on polyamide film were observed through Scanning Electron Microscope Model JSM-5610 LV, Version 1.0, Jeol Japan. The amount of MMT Clay as element in the polymer structure was detected and measured on SEM using oxford Inca software (Oxford, U.K.). The chemical composition of prepared composite film was further evaluated using FTIR Spectroscopy Nicolet is10 FT-IR Spectrometer (Thermo Scientific).

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 38 2.3.2 Determination of Mechanical Properties The specimens were conditioned at 65 ± 2 % relative humidity and 27 ± 2 C before physical testing. The breaking strength in gf/mm 2 of films with different concentration was measured on tensile tester (LRY model, Lloyd, U K), with 50 mm/min speed and 20 mm gauge length. 2.3.3 Determination of Thermal Behavior The thermal characterizations of film were analyzed using DSC model 6000 from PerkinElmer, Singapore temperature range from 50 C to 300 C. 3. Results and Discussion: 3.1 Preparation of Polyamide/Nanoclay Composite Film The aim of the present investigation was to establish simple technique to prepare polyamide / nanoclay composite film with improved mechanical and thermal properties compared to the pure polyamide film. Figure 1- SEM images of (a) pure PA-6 and (b) nylon-6/mmt clay nanocomposite film (0.5 wt. - %) As seen from figure 1, composite film exhibits good dispersion of organo clay particles. It is seen that, if any properties are to be further improved, then the distribution of the inorganic filler particles in the polymer matrix has to be as homogeneous as possible. In this work we have incorporated MMT particles from aqueous medium to formic acid as bulk solvent. Addition of small amount of aqueous HCL was added to maintain ph 1-2. Such a low ph was necessary since the iso-electric point of silica in MMT is in the ph 2-3 range. Solvent use was kept to a minimum to ensure concentrated, highly viscous solutions could be cast on clean glass surfaces followed by a combination of vacuum and heat (60 80 C) treatments to remove solvent. The PA/MMT composite film was prepared by using formic acid as organic solvent which also prevents gel formation addition of mmt nanoparticles to pa solution. The pure polyamide solution was obtained by ternary phase system [10] of polyamide: formic acid: water. For the preparation of PA / MMT nanocomposite solution 0.1 %, 0.5% and 0.8% of organoclay was added to the above obtained pure polymer solution respectively. The solution mixture was continuously stirred for 1hr to obtain clear solution, which is necessary for ensuring mechanical reinforcement properties to be investigated. 3.2 Characterization of PA6/MMT Composite Film The pure polyamide and PA film contains the smallest MMT nanoparticles with negligible aggregation were observed by SEM. SEM pictures taken from different sample localities revealed an even distribution of the MMT nanoparticles throughout the film. The SEM micrographs indicated that

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 39 the MMT particles were non- aggregated and well dispersed on the PA6 film. Figure 2 shows the SEM picture of a sample containing 0.1 to 0.8% nano MMT. Figure 2- SEM micrographs of pure PA6, 0.1%, 0.5% and 0.8 wt. % MMT loaded PA6 films Element Weight % Atomic % C K 13.24 19.65 O K 55.14 61.46 Mg K 5.87 4.31 Al K 6.51 4.30 Si K 11.90 7.56 K K 1.95 0.89 Ca K 0.87 0.39 Fe K 4.53 1.45 Total 100.00 Figure 3- Elemental analysis of PA/nanoclay film

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 40 Elemental analysis of PA6 / MMT nanocompsite film was performed on oxford inca software using SEM. Figure 3 shows the image analysis result of MMT incorporated film. The elemental analysis results presented in the figure confirms the presence of MMT particles. Peaks for SI, AL, and other elements were also observed being part of organoclay. Further the chemical composition of prepared PA6 / MMT nanocomposite film was investigated by FTIR. Figure 4- IR absorption spectra of PA/MMT nanocomposite film FTIR spectra are used in this study as a qualitative measurement to analyze the chemical structure of polyamide clay nano composite film. From the FTIR spectra presented in figure 4 it has been seen that the major peaks associated were hydrogen bonded N-H stretching 3294 cm -1 and 3700 cm -1, anti symmetric CH 2 stretching at 2935 cm -1, symmetric CH 2 stretching at 2867 cm -1, C=0 stretching at 1634 cm -1 which also indicates O-H deformation of water in clay, in plane N-H bending at 1538 cm -1, CH 2 symmetric bending at 1463 cm -1, at 1477cm -1 C=C stretching, at 1416 cm -1 O-H bending of carboxylic acid, at 1200 cm -1 C-N stretching of amine, at 1029 cm -1 and 1107 cm -1 Si-O stretching, at 928 cm -1 AlAlOH deformation due to the clay, and at 686cm -1 represent Si-O stretching coupled out of plane and N-H bending confirms the presence of MMT clay in polyamide matrix. 3.3 Effect on Mechanical Properties The tensile strength of a composite film with 0.1, 0.5 and 0.8 wt % addition of MMT organoclay were evaluated and compared with virgin polyamide film. It has been observed from figure 5 the specific strength of the film increases with increase in filler concentration up to 0.5% wt (i.e 83% increase in sp. Strength was observed compared to pure film) but marginal decrease in sp. Strength was observed with 0.8% wt filler loading. It may be attributed due to the water suspended MMT nano particles make composite film brittle. Similar observation is reported by F. Yang et al. [11].

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 41 Figure 5 Specific strength of composite with 0.1, 0.5 and 0.8 Wt % filler compared to pure polyamide The trend is further supported by stiffness of the film. It is observed that up to 0.5 wt% of filler loading the composite film gives better results compared to pure film but as we increase the loading the film becomes brittle and breaks easily, which also seen from the SEM micro photograph figure 2. Figure 6 Stiffness of composite with 0.1, 0.5 and 0.8 Wt % filler compared to pure polyamide Further there was a distinct decrease in young modulus from 60 Mpa for polyamide composite film with 0.5 wt% loading to 20 Mpa 0.8wt % clay nanocomposite film [figure 7], which is a promising result with respect to impact toughness up to 0.5 wt%.

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 42 Figure 7- Variation in elastic modulus for composites with different filler percentage 3.3 Effect on Thermal Property From figure 8 (a), the thermal degradation behaviour of pure PA6 film was followed with DSC. The onset degradation temperature of pure PA6 film was found to be 205.26 C and at 213.99 C the maximum of endothermic peak was observed. On inclusion of 0.5 wt. % of MMT to PA6 film (Figure 8 b), the onset temperature was found increased by 4 C, and the maximum peak temperature was also increased by 4 C, which shows PA6 film containing MMT nano presents higher thermal stability then pure PA6 film due to formation of nano composite. Improvement in thermal stability was also supported by higher delta H value of the composite film. This may be due to the catalysis effect of clay towards the degradation of the polymer.

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 43 4. Conclusions: Figure 8- DSC curve of PA6 (a) and PA6 0.5 wt. % nano clay film (b) The solution dissolution method for the preparation of PA6 based composite film can successfully utilized for the production of industrial composite film. There is an increase in tensile strength and young modulus as a function of filler % added [0 to 0.8 %]. A small decrease in mechanical property was observed at 0.8 % addition of MMT in pa film. The thermal stability of composite film increases with addition of MMT nano clay in polyamide film this type of film can be used for food packaging as well as for medical and biological applications. References [1] W. Helbert, J.Y. Cavaillé and A. Dufresne, Thermoplastic nanocomposites filled with wheat straw cellulose whiskers Part I: Processing and mechanical behavior, Polym. Compos., 17(1996), 604-611. [2] B.H. Patel and D.P. Chattopadhyay, Nano-particles & their uses in textiles, The Indian Textile Journal, 118(2007), 23-31. [3] A.A. Mandot, S.B. Chaudhari and B.H. Patel, Nanocomposite: Manufacturing and applications in textiles, Melliand International, 18(3) (2012), 188-189. [4] D. P. Chattopadhyay and B.H. Patel, Preparation, characterization and stabilization of nano sized copper particles, International Journal of Pure Sciences and Technology, 9(1) (2012), 1-8. [5] D.P. Chattopadhyay and B.H. Patel, Improvement in physical and dyeing properties of natural fibres through pre-treatment with silver nanoparticles, Indian Journal of Fibre & Textile Research, 34(2009), 368-373. [6] D.P. Chattopadhyay and B.H. Patel, Effect of nanosized colloidal copper on cotton fabric, Journal of Engineered Fiber Fabrics, 5(2010), 1-6. [7] M.I. Kohan, Nylon Plastics Handbook, Hanser Publishers, Cincinnati, 1995. [8] S.M. Aharoni, n-nylons: Their Synthesis, Structure and Properties, John Wiley and Sons, Chichester, 1997. [9] M.B. Ahmad, W.H. Hoidy, N.A. Bt Ibrahim and E.A.J. Al Mulla, Modification of montmorillonite by new surfactants, Journal of Engineering and Applied Sciences, 4(2009), 184-188. [10] L.P. Cheng, A.H. Dwan and C.C. Gryte, Membrane formation by isothermal precipitation in polyamide-formic acid-water systems I: Description of membrane morphology, J. Polym. Sci., Part B: Polym. Phys., 32(1994), 1183.

Int. J. Pure Appl. Sci. Technol., 17(2) (2013), 36-44 44 [11] F. Yang, Y. Ou and J.Z.Z. Yu, Polyamide 6/silica nanocomposites prepared by in situ polymerization, Appl. Polym. Sci., 69(1998), 355.