Al2Mo3O12/polyethylene composites with reduced coefficient of thermal expansion
- 472 Downloads
Recently, polymer composites reinforced with low fractions of thermomiotic nanoceramics have triggered a lot of research. The efforts have been focused on achieving considerable reduction of the coefficient of thermal expansion (CTE) of polymeric materials without deterioration of other physical properties. In this context, polyethylene (PE) composites reinforced with different loads of Al2Mo3O12 nanofillers (0.5–4 mass %) were fabricated by micro-compounding. To enhance the interfacial interaction between the two components, chemical functionalization of Al2Mo3O12 was performed with vinyltrimethoxysilane (VTMS) prior to micro-compounding. Infrared spectroscopy and thermogravimetry demonstrated the successful grafting of VTMS on the Al2Mo3O12 surface. The composites showed strongly decreased CTEs, up to 46 % reduction for loadings of 4 mass % compared with neat PE, suggesting intimate filler–matrix interactions. The variation of CTEs of the composites in terms of the filler fraction was successfully described by Turner’s model allowing calculation of the bulk modulus of monoclinic Al2Mo3O12 (13.6 ± 2.6 GPa), in agreement with the value obtained by an ultrasonic method. The thermal stability of the composites was improved, although the addition of functionalized fillers decreased the degree of crystallinity of the PE to a small extent. The Young’s modulus and yield strength of the composites increased from 6.6 to 19.1 % and 4.0–6.0 %, respectively, supporting the existence of strong filler–matrix interactions, contributing to an efficient load transfer. Finite element analysis of thermal stresses indicated absence of plastic deformation of the matrix or fracture of the nanofillers, for a 100 K temperature drop.
KeywordsBulk Modulus Negative Thermal Expansion Vinyltrimethoxysilane Physical Entanglement Efficient Load Transfer
B.A. Marinkovic and J.R.M. d’Almeida are grateful to CNPq (National Council for Scientific and Technological Development) for a Research Productivity Grants. Patricia I. Pontón is also grateful to CNPq for scholarship. M.A. White acknowledges support of NSERC through the Discovery Grants program. We thank J.W. Zwanziger for use of the ultrasonic transducer.
- 10.Kim IJ, Gauckler LJ (2008) Excellent thermal shock resistant materials with low thermal expansion coefficients. J Ceram Process Res 9:240–245Google Scholar
- 32.Take WA, Watson E, Brachman RW, Rowe RK (2012) Thermal expansion and contraction of geomembrane liners subjected to solar exposure and backfilling. J Geotech Geoenviron 138:1287–1397Google Scholar
- 47.http://www.paralab.pt/sites/default/files/pdf/DIL402C.pdf. Accessed 17 Feb 2014
- 56.Varga T, Wilkinson AP, Lind C, Bassett WA, Zha C (2005) High pressure synchrotron x-ray powder diffraction study of Sc2Mo3O12 and Al2W3O12. J Phys: Condens Matter 17:4271–4283Google Scholar
- 61.Chrissafis K, Bikiaris D (2011) Can nanoparticles really enhance thermal stability of polymers? Part I: An overview on thermal decomposition of addition polymers, Thermochim Acta 523:1–24Google Scholar
- 63.Aizan W, Rahman WA (2006) Design of silane crosslinkable high density polyethylene compounds for automotive fuel tank application. Universiti Teknologi Malaysia, Proyect ReportGoogle Scholar
- 65.Li S, Chen H, Cui D, Li J, Zhang Z, Wang Y, Tang T (2010) Structure and properties of multi-walled carbon nanotubes/polyethylene nanocomposites synthesized by in situ polymerization with supported Cp2ZrCl2 catalyst. Polym Compos 31:507–515Google Scholar
- 68.Zebarjad SM, Sajjadi SA, Tahani M, Lazzeri A (2006) A study on thermal behaviour of HDPE/CaCO3 nanocomposites. J Achiev Mater Manuf Eng 17:173–176Google Scholar