Graphene as the Disperse Phase in the Polyamide Matrix

Transcription

1 Machine Dynamics Research 2016, Vol. 40, No 2, Graphene as the Disperse Phase in the Polyamide Matrix Anna Makuch *1, Marcin Bajkowski 2, Maria Trzaska 1, and Konstanty Skalski 1 1 Warsaw University of Technology, Institute of Precision Mechanics 2 Warsaw University of Technology, Department of Construction Engineering and Biomedical Engineering Abstract This paper presents the results of investigations into the development of a new composite material with polyamide matrix and multilayer graphene as the disperse phase. Consolidation of the new material was preceded by the selection of appropriate parameters of the process of preparation of powders (elements of composite material). Mechanical and structural properties of the new composite in form of PA-G strips were assessed at the microstructural level using nanoindentation test, optical techniques (3D microscope), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of the tests showed that adopted technologies of production allow to obtain material with improved mechanical properties and homogeneous deployment of strengthening phase in the soft polyamide matrix. These features allow to apply new material in special constructions, especially in regard to load-bearing elements of small arms, butt and additional equipment. Keywords: graphene, PA-G composite, polyamide, nanoindentation, X-ray diffraction, scanning electron microscopy. 1 Introduction Composite materials are constructed of various phases and have properties that are unachievable in case of conventional "materials with monolithic construction" (Makuch et al., 2015). In recent years, graphene as the material with the unique physicochemical properties (Kuilla et al., 2010) holds the special position in this branch of science. Researches on the new polymer-based composite materials supplemented by the carbon allotrope (fullerene, graphene, nanotubes) are recently carried out in scientific centers worldwide (Cheng et al., 2013; Hekner et al., 2014; Kelar, 2006; Kim et al., 2013; Kuilla et al., 2010). The results of this tests indicate that supplemented polymer materials (i.a. aniline, polyethylene, ethyl methacrylate, nylon) have *a.makuch1309@gmail.com

2 90 Makuch A., Bajkowski M., Trzaska M., Skalski K. increased mechanical, physical, and in particular, thermal properties (Araby et al., 2013; Gonçalves et al., 2010; Zhu et al., 2012), provided that components were adequately prepared and appropriate technological parameters were used. At the same time, in this case more than in other materials, it is possible to shape and design the properties of such material by the appropriate selection of components, shape and size of elements in disperse phase (Kuilla et al., 2010). Combinations of such diverse materials in the composite allow to clearly supplement them, while the interaction between the phases induces a modification of these properties. In case of each disperse phase there is a possibility to design adequate properties of composite material through the selection of size and shape of elements and their content in the material and also through the selection of method and the parameters of the consolidation process (Makuch et al., 2015). In order to obtain preferred physicochemical properties of new composite, due to the nature of the technological process, it is crucial to obtain homogeneous composite powder followed by the thermal consolidation with appropriate parameters. The percentage of components and the method of their preparation for the consolidation process determine the porosity and the proper structure of the obtained composite material. During such researches (Makuch et al., 2015) tests were conducted in order to verify what is the impact of the method and parameters of mixing of polyamide powder and graphene flakes on their morphology and structure, as well as the homogeneity of blends intended for the production of a new PA-G composite. In this study an attempt was made to produce the PA-Graphene composite strips on the basis of PA-G composite powder using the thermal method. The assumption of the project is to ensure the possibility to use this type of the material in the form of strips as potential material able to strengthen the load-bearing elements of the bodies in shoulder stocks equipped with shock absorbers and magnetorheological dampers (Bajkowski et al., 2015). Due to the potential application range, mechanical and structural properties of new composite in form of PA-G stripes were verified at the microstructural level, using optical techniques (3D microscope), X-ray diffraction (XRD) and scanning electron microscopy (SEM) test, and in particular nanoindetation, which is increasingly used to assess i.a. the parameters of hardness, elasticity and energy effects in the deformation process of heterogeneous materials using the indenter tip (Yan et al., 2012; Schuh, 2006). 2 Material In order to produce PA-G composite, the PA-G-8 powder was used Makuch et al. (2015), i.e. the one homogenized for 8 hours by a rotary blender. The composite powder includes polyamide powder type 12 (1% of weight) with 3D spherical shape of particles with a diameter of approx. 60 [µm] (Fig. 1) and powder consisting

3 Graphene as the Disperse Phase of graphene flakes (99% of weight), produces by Grafen Chemical Industries Co., with the thickness of graphene flakes approx. 5-8 [nm] and surface area of [m 2 /g] (Fig. 2). The method and the parameters of the process of the preparation of the composite powder (Fig. 3) and the results of the study were presented in the paper (Makuch et al., 2015). The researches on the composite strips (PA-G) were carried out through the optical microscope 2D (NICON ECLIPSE LV150 coupled with the computer image analysis tool NIS-Elements BR 3.0), microscope 3D (Keyence vhx 5000), ZEISS scanning electron microscope (SEM) and Raman spectrometer. Fig. 1. Picture of particles (a) and Raman spectrum (b) of polyamide powder. Fig. 2. Picture of particles (a) and Raman spectrum (b) of graphene flakes. Composite PA-G powder (Fig. 3) was applied as a thin layer (0,020 [m]) on the ceramics and thermally consolidated under controlled compression at 175 [ C].

4 92 Makuch A., Bajkowski M., Trzaska M., Skalski K. Fig. 3. PA-G-8 - composite powder (a) and composite in the form of strip after thermal consolidation Results Tests of mechanical properties at the microstructural level Tests of mechanical properties (at the microscopic level) were carried out using DSI (Depth Sensing Indentation) method (Oliver and Pharr, 2004; Sneddon, 1965) which, on the basis of the indenter tip able to immerse into the material to a depth of microor nanometers under a given load of milinewtons, allows to determine the parameters of hardness, elasticity and energy (Fig. 4) on the basis of the PN-EN ISO standard (ISO, 2005). Fig. 4. Relationship between load and depth during the penetration of the indenter tip into the material. Examination of both, the reference material, i.e. polyamide foil type 12 and nylon PA-G composite strips was performed on the Nanoindentation Tester device (NHT) produced by CSM Instruments, under the constant environmental conditions. Berkovich diamond indenter tip (B-N90) was used in this study. The following parameters were assumed: Maximum load: [mn], deformation velocity: [mn/min], retention time τ = 10.0 [s]. The figure 5 illustrates, respectively, the diagrams of changes in force of load/unload and depth vs. time for PA foil (5a) and PA-G composite (5b) in the course of nanoin-

5 Graphene as the Disperse Phase dentation test. Thereafter (Fig. 6) load force vs the depth of the indentation obtained for polyamide foil (6a) and PA-G composite foil (6b) with max. load force: Pmax = 50 [mn], retention time: τ = 10 [s], and the deformation velocity: v = 100 [mn/min]. At the end, the comparison of the 7 nanoindentation tests for new composite were presented (Fig. 7), the force of which vs depth indicate the high homogeneity of the produced material. Fig. 5. Diagrams of changes of loading/unloading force and depth vs. time for PA foil (a) and PA-G composite (b) Pmax = 50 [mn], v = 100 [mn/min], τ = 10 [s]. Fig. 6. Curves: loading force - the depth of the indentation obtained for polyamide foil (a) and PA-G foil (b) - individual test; Pmax = 50 [mn], v = 100 mn/min, τ = 10 [s].

6 94 Makuch A., Bajkowski M., Trzaska M., Skalski K. Fig. 7. Comparison of the curves: loading force - the depth of the he indentation obtained for PA-G foil with a maximum loading force Pmax = 10 [mn], v = 20 [mn/min], τ = 10 [s]. The tables 1 and 2 show the results of measurements (considering 5 tests) of microhardness, elasticity and energy for PA polyamide foil. Due to the fact that the test no. 5 was carried out under other conditions (10 times higher speed and power of loading / unloading), it is only the point of reference, but it is not taken into consideration in the statistical comparisons. Table 1. Results of measurements of microhardness and elasticity for PA polyamide foil - conditions of measurements: v = 20 [mn/min], Pmax = 10 [mn], τ = 10 [s]. Test Microhardness H IT [MPa] Modulus of Elasticity E IT [GPa] Modulus of Elasticity E [GPa] Modulus of Elasticity E r [GPa]

7 Graphene as the Disperse Phase Table 2. Results of measurements of Energy parameters for PA polyamide foils - conditions of measurement: v = 20 [mn/min], Pmax = 10 [mn], τ = 10 [s]. Test W elast [nj] W plast [nj] W total [nj] Fig. 8. Comparison of H IT hardness (a) and modulus of elasticity E IT (b) for pure polyamide PA in every test; v = 20 [mn/min], Pmax = 10 [mn], τ = 10 [s]. The tables 3 and 4 show the results (considering 8 tests) of measurements of microhardness, elasticity and energy for PA-G foil. Due to the fact that the test no. 1 was carried out under other conditions (higher speed and power of loading / unloading), it is only the point of reference, but is not taken into consideration in the statistical comparisons.

8 96 Makuch A., Bajkowski M., Trzaska M., Skalski K. Table 3. Results of measurements of microhardness and elasticity for PA polyamide foil - conditions of measurements: v = 20 [mn/min], Pmax = 10 [mn], τ = 10 [s]. Test Microhardness H IT [MPa] Modulus of Elasticity E IT [GPa] Modulus of Elasticity E [GPa] Modulus of Elasticity E r [GPa] Table 4. Results of measurements of energy parameters for PA polyamide foils - conditions of measurement: v = 20 [mn/min], Pmax = 10 [mn], τ = 10 [s]. Test W elast [nj] W plast [nj] W total [nj] Fig. 9. Comparison of H IT hardness (a) and elasticity (b) for stripes of PA-G composite in every test; v = 20 [mn/min], Pmax = 10 [mn], τ = 10 [s].

9 Graphene as the Disperse Phase Structural tests Structural tests on the PA-G composite strips and the comparative ones made of pure polyamide were carried out using 3D Keyence VHX 5000 digital microscope with camera and 3D software for the purpose of carrying out the measurements of profiles using XY multi-angle stand. Used magnification range Optical analysis allowed to assess the homogeneity of the formed composite, but also to verify the thickness of the produced strips. The measurements were carried out for the reference material - polyamide (Fig. 10) and for new PA-G composite material (Fig. 11). Fig. 10. Picture of polyamide strip (a) and optical measurement of thickness g = [µm] (b). Fig D and 3D picture of G deployment in the composite material PA-G. 4 Conclusions The researches enabled to develop a new PA-Graphene composite material and initially verify it in terms of possibilities to apply it as the material for load-bearing elements of butt treated with high-energy impulses and equipped with magnetorheological systems designed to minimize the impact of the butt on shooter s shoulder. The analysis of the mechanical and structural properties of the new material in reference to pure matrix material, ie. polyamide. The comparative analysis of the structure and mechanical properties of the PA-G

10 98 Makuch A., Bajkowski M., Trzaska M., Skalski K. composite with matrix material - PA - was carried out. The analysis reviews the mixing parameters impact on the structure and plasticity of the PA-G composite material: homogenization of the structure of the PA-G composite powder, fragmentation flakes of graphene on the surface of the polyamide, change of shape of matrix units and the nature of the deployment of nano-flakes of the graphene on its surface, plasticization of the polyamide and initiation of the bonding process (Fogagnolo et al., 2003). Research showed that adopted method of rotational prepare of the composite powder and applied parameters provide relatively uniform deployment of flakes of graphene in polymeric matrix of PA-G composite material (Makuch et al., 2015). The test of microhardness of the composite using the DSI method proved that, PA-G composite material is characterized by the greater hardness and elasticity in comparison to the polyamide. Commonly approved DSI method of measurement of microhardness indicates that assumptions made during its analysis could lead to significant differences in determining rigidity dp/dh, thereby could significantly influence the test results for the modulus of elasticity. The hysteresis curves have also significant effect on the mechanic properties of new composite materials based on the polyamide and graphene. DSI method for measurement od hardness and for determining the Young s modulus is very useful while measuring the properties of composites of the basis on graphene in polyamide graphene at the micro level, in particular in the form of thin strips (Schuh, 2006; Yan et al., 2012). In further research special attention should be paid to the relation between energy of deformation and hardness and Young s modulus. The results of the tests showed that adopted technologies of production allow to obtain material with preferred mechanical properties (improved hardness and elasticity) and homogeneous deployment of strengthening phase in the soft polyamide matrix. These features suggest that it is possible to apply it in the elements of special objects treated with high-energy, quick-exchange impulses of force. Acknowledgments The research was carried out within the project (IMP 2015) and project PBS1/A6/10/2012 supported by the NCBiR. References Araby, S., Zaman, I., Meng, Q., Kawashima, N., Michelmore, A., Kuan, H.-C., Majewski, P., Ma, J., and Zhang, L. (2013). Melt compounding with graphene to develop functional, high-performance elastomers. Nanotechnology, 24(16): Bajkowski, M., Kaniewski, J., and Radomski, M. (2015). Dynamika układu mechanicznego: strzelec: amortyzator odrzutu: broń palna. Problemy Mechatroniki: uzbrojenie, lotnictwo, inżynieria bezpieczeństwa, 6:41 56.

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