Effects of silica aerogel content on microstructural and mechanical properties of poly(methyl methacrylate)/silica aerogel dual-scale cellular foams processed in supercritical carbon dioxide

Abstract

A novel poly(methyl-methacrylate)/silica aerogel (PMMA/SA) dual-scale cellular foam was synthesized with internal mixing followed by the supercritical carbon dioxide foaming process. The effects of silica aerogel content on the microstructural and mechanical performance of the foams were investigated by SEM, TEM analysis, and mechanical tests. The experimental results suggest that the employment of silica aerogel granule as addictive can distinctly improve the morphological feature as well as the mechanical performance in comparison to neat PMMA foam by uniformizing cell size distribution, decreasing cell size and increasing cell density. And dual-scale cells including micrometric cells of 3-10 μm and nanometric cells of about 50nm existed in the structure of foams resulting from the retained original framework structure of silica aerogel, which has not been described in other studies with the addition of various fillers. Furthermore, the mechanical strength was significantly elevated even with a small amount of silica aerogel resulting from the unique microstructure, decreased cell size and enhanced cell walls. The compressive strength was 18.12 MPa and the flexural strength was 18.90 MPa by adding 5wt% and 2wt% silica aerogel, respectively. These results demonstrate the potential to synthesize PMMA/SA dual-scale cellular foams to be used as structural materials with the advantages of low density and high strength.

Keywords

PMMA / silica aerogel / supercritical carbon dioxide / microstructure / mechanical properties

References

[1] Zhao J, Jiang S, Ke Z, et al. Microcellular Foaming of Plasticized Thin PC Sheet I. Effects of Processing Conditions[J]. Journal of Wuhan University of Technology-Materials Science Edition, 2013, 28(2): 235-242.

[2] Han X, Koelling KW, Tomasko DL, et al. Continuous Microcellular Polystyrene Foam Extrusion with Supercritical CO₂[J]. Polymer Engineering and Science, 2002, 42(11): 2

[3] Reverchon E, Adami R, Cardea S, et al. Supercritical Fluids Processing of Polymers for Pharmaceutical and Medical Applications[J]. The Journal of Supercritical Fluids, 2009, 47(3): 484-492.

[4] Reverchon E, Cardea S. Production of Controlled Polymeric Foams by Supercritical CO₂[J]. The Journal of Supercritical Fluids, 2007, 40(1): 144-152.

[5] Ash BJ, Siegel RW, Schadler LS, et al. Mechanical Behavior of Alumina/Poly (methyl methacrylate) Nanocomposites[J]. Macromolecules, 2004, 37(4): 1358-1369.

[6] Fan Z, Gong F, Nguyen ST, et al. Advanced Multifunctional Graphene Aerogel-Poly (methyl methacrylate) Composites: Experiments and Modeling[J]. Carbon, 2015, 81: 396-404.

[7] Alzarrug FA, Dimitrijević MM, Heinemann RMJ, et al. The Use of Different Alumina Fillers for Improvement of the Mechanical Properties of Hybrid PMMA Composites[J]. Materials & Design, 2015, 86: 575-581.

[8] Tsimpliaraki A, Tsivintzelis I, Marras SI, et al. The Effect of Surface Chemistry and Nanoclay Loading on the Microcellular Structure of Porous poly (d, l lactic acid) Nanocomposites[J]. The Journal of Supercritical Fluids, 2011, 57(3): 278-287.

[9] Bledzki AK, Kirschling H, Rohleder M, et al. Correlation between Injection Moulding Processing Parameters and Mechanical Properties of Microcellular Polycarbonate[J]. Journal of Cellular Plastics, 2012, 48(4): 301-340.

[10] Reglero Ruiz JA, Viot P, Dumon M, et al. Microcellular Foaming of Polymethylmethacrylate in a Batch Supercritical Carbon Dioxide Process: Effect of Microstructure on Compression Behavior[J]. Journal of applied polymer science, 2010, 118(1): 320-331.

[11] Lee LJ, Zeng C, Cao X, et al. Polymer Nanocomposite Foams[J]. Composites Science and Technology, 2005, 65(15): 2344-2363.

[12] Zhai W, Yu J, Wu L, et al. Heterogeneous Nucleation Uniformizing Cell Size Distribution in Microcellular Nanocomposites Foams[J]. Polymer, 2006, 47(21): 7580-7589.

[13] Liu Y, Kontopoulou M, et al. The Structure and Physical Properties of Polypropylene and Thermoplastic Olefin Nanocomposites Containing Nanosilica[J]. Polymer, 2006, 47(22): 7731-7739.

[14] Tsivintzelis I, Angelopoulou AG, Panzyiotou C, et al. Foaming of Polymers with Supercritical Carbon Dioxide: An Experimental and Theoretical Study[J]. Polymer, 2007, 48(20): 5928-5939.

[15] Fazli Y, Kulani E, Khezri K, et al. PMMA-grafted Silica Aerogel Nanogranule Via in Situ SR&NI ATRP: Grafting Through Approach[J]. Microporous and Mesoporous Materials, 2015, 214: 70-79.

[16] Kim KS, Byun JH, Lee GH, et al. Influence of GMA Grafted MWNTs on Physical and Rheological Properties of PMMA-based Nanocomposites by in situ Polymerization[J]. Macromolecular Research, 2011, 19(1): 14-20.

[17] Jiao J, Wang L, Wu G, et al. Effects of Framework Structure and Coupling Modification on the Properties of Mesoporous Silica/poly (Methyl Methacrylate) Composites[J]. Journal of Reinforced Plastics and Composites, 2014

[18] Chang YW, Lee D, Bae SY, et al. Preparation of Polyethylene-octene Elastomer/clay Nanocomposite and Microcellular Foam Processed in Supercritical Carbon Dioxide[J]. Polymer international, 2006, 55(2): 184-189.

[19] Li M, Shen Q, Zhang L. Microstructure and Electrical Conductivity of CNTs/PMMA Nanocomposite Foams Foaming by Supercritical Carbon Dioxide[J]. Journal of Wuhan University of Technology-Materials Science Edition, 2016, 31(2): 481-486.

[20] Chen L, Goren B, Ozisik R, et al. Controlling Bubble Density in MWNT/Polymer Nanocomposite Foams by MWNT Surface Modification[J]. Composites Science and Technology, 2012, 72(2): 190-196.

[21] Zeng C, Hossieny N, Zhang C, et al. Synthesis and Processing of PMMA Carbon Nanotube Nanocomposite Foams[J]. Polymer, 2010, 51(3): 655-664.

[22] Shinzato S, Nakamura T, Ando K, et al. Mechanical Properties and Osteoconductivity of New Bioactive Composites Consisting of Partially Crystallized Glass Beads and Poly (Methyl Methacrylate)[J]. Journal of Biomedical Materials Research, 2002, 60(4): 556-563.

[23] Goren K, Chen L, Schadler LS, et al. Influence of Nanoparticle Surface Chemistry and Size on Supercritical Carbon Dioxide Processed Nanocomposite Foam Morphology[J]. The Journal of Supercritical Fluids, 2010, 51(3): 420-427.

[24] Zhang FA, Luo M, Chen ZJ, et al. Effects of Mesoporous Silica Granule on the Emulsion Polymerization of Methyl Methacrylate[J]. Polymer Engineering & Science, 2014, 54(12): 2746-2752.

[25] Ma Z, Zhang G, Yang Q, et al. Mechanical and Dielectric Properties of Microcellular Polycarbonate Foams with Unimodal or Bimodal Cell-size Distributions[J]. Journal of Cellular Plastics, 2014

[26] Notario B, Pinto J, Rodríguez-Pérez MA, et al. Towards a New Generation of Polymeric Foams: PMMA Nanocellular Foams with Enhanced Physical Properties[J]. Polymer, 2015, 63: 116-126.

[27] Mulik S, Sotiriou-Leventis C, Churu G, et al. Cross-linking 3D Assemblies of Nanogranule into Mechanically Strong Aerogels by Surfaceinitiated Free-radical Polymerization[J]. Chemistry of Materials, 2008, 20(15): 5035-5046.

[28] Zheng M, Wu J. Synthesis and Thermal Insulation Performance of Silica Aerogel from Recycled Coal Gangue by Means of Ambient Pressure Drying[J]. Journal of Wuhan University of Technology-Materials Science Edition, 2015, 30(5): 908-913.

[29] Maleki H, Durães L, Portugal A, et al. An Overview on Silica Aerogels Synthesis and Different Mechanical Reinforcing Strategies[J]. Journal of Non-Crystalline Solids, 2014, 385: 55-74.

[30] Gaspar A, Nagy A, Lazar I, et al. Integration of Ground Aerogel Granule as Chromatographic Stationary Phase into Microchip[J]. Journal of Chromatography A, 2011, 1218(7): 1011-1015.

[31] Schneider CA, Rasband WS, Eliceiri KW, et al. NIH Image to ImageJ: 25 Years of Image Analysis[J]. Nature methods, 2012, 9(7): 671-675.

[32] Kumar V, Suh NA, et al. A Process for Making Microcellular Thermoplastic Parts[J]. Polymer Engineering & Science, 1990, 30: 1323-1329.

[33] Colton JS, Suh NP, et al. Nucleation of Microcellular Foam: Theory and Practice[J]. Polymer Engineering & Science, 1987, 27(7): 500-503.

[34] Sun H, Sur G S, Mark JE, et al. Microcellular Foams from Polyethersulfone and Polyphenylsulfone: Preparation and Mechanical Properties[J]. European Polymer Journal, 2002, 38(12): 2373-2381.

[35] Yuanlu X, Qiang S, Huan Y, et al. Foaming of CNTs/ PMMA Nanocomposite with Supercritical Carbon Dioxide[J]. Key Engineering Materials, 2012, 508: 61.

[36] Chen L, Schadler L, Ozisik R, et al. An Experimental and Theoretical Investigation of the Compressive Properties of Multi-walled Carbon Nanotube/poly(Methyl Methacrylate) Nanocomposite Foams[J]. Polymer, 2011, 52(13): 2899-2909.