Effect of the presence of silica nanoparticles in the coefficient of thermal expansion of LDPE

• Published in: European polymer journal Vol. 47; no. 8; pp. 1495 - 1502
• Main Authors: Olmos, D., Martínez, F., González-Gaitano, G., González-Benito, J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2011; Elsevier
• Subjects: AFM (atomic force microscopy); Aluminum oxide; Applied sciences; Coefficient of thermal expansion (CTE); Composites; Exact sciences and technology; Forms of application and semi-finished materials; LDPE (low density polyethylene); Microparticles; Nano-composites; Nanocomposites; Nanoparticles; Nanostructure; Polyethylenes; Polymer industry, paints, wood; Silicon dioxide; Technology of polymers; Thermal expansion; LDPE (low density polyethylene); Coefficient of thermal expansion (CTE); AFM (atomic force microscopy); Nano-composites; Atomic force microscopy; Film; Experimental study; Silica; Thermal properties; Low density ethylene polymer; Thermal expansion coefficient; Nanocomposite; Measurement method; Alumina
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2011.06.003

[Display omitted] ► A new method based on the use of AFM was proposed to measure CTE of thin films. ► The effect of the presence of silica nanoparticles on the CTE of LDPE was evaluated. ► The presence of silica nanoparticles reduces the thermal expansion of LDPE. ► Constraint effects on the LDPE seem to be the cause of its CTE reduction. The effect of the presence of alumina microparticles and silica nanoparticles on the coefficient of thermal expansion (CTE) of films of low density polyethylene (LDPE) based composites was investigated. A new method based on the use of an atomic force microscope (AFM) is proposed for measuring nano-thermal expansion of films to finally obtain the CTE in polymer based materials. Nanocomposites based on silica nanoparticles and LDPE were prepared by mixing those constituents by high energy ball milling (HEBM). Pure alumina microparticles come from the milling tools used to mix the components of the composites. When silica nanoparticles are used as nanofiller of LDPE the effectiveness on reducing the CTE (about a 40% of CTE reduction) is higher than that obtained when high amount of alumina microparticles are present in the LDPE. Only when high amount of silica nanoparticles and low amount of alumina microparticles are present, the reduction of CTE expected from the Levin model is in accordance with the experimental results. This effect was associated to the high surface to volume ratio of nanoparticles considering uniform dispersions of them within the polymer. The region of polymer between particles must be so thin (few nanometers) that constraint effects must play an important role on reducing the chain mobility and therefore the thermal expansion.