Abstract
Multilayered polymer films with biomimicking, layered structures have unique microstructures and many potential applications. However, a major limitation of polymer films is the deterioration of mechanical properties in working environments. To facilitate the design and development of multilayered polymer films, the impact of thermal aging on the mechanical behavior of micro- and nano-layered polymer films has been investigated experimentally. The composition of the polymer films that have been studied is 50 vol% polycarbonate (PC) and 50 vol% poly(methyl methacrylate) (PMMA). The current study focuses on the effect of film and layer thickness and temperature on the mechanical properties of the materials subjected to thermal aging. To study the effect of film and layer thickness, films with the same thickness, but various layer thicknesses, and films with the same layer thickness, but various film thicknesses, were thermally aged at 100 °C in a constant temperature oven for up to six weeks. The results show that as the layer thickness decreases to 31 nm, the film has a higher stiffness and strength, and the trend of the mechanical properties is relatively stable over aging. The ductility of all of the films decreases with aging time. To study the effect of temperature, the films with 4,096 layers (31 nm thick for each layer) were aged at 100 °C, 115 °C and 125 °C for up to four weeks. While the 100 °C aging results in a slight increase of the stiffness and strength of the films, the higher aging temperature caused a decrease of the stiffness and strength of the films. The ductility decreases with the aging time for all of the temperatures. The films become more brittle for higher aging temperatures.
Highlights
Polymers have a wide range of applications due to their inherent properties, such light-weight, strength, resistance to chemicals, thermal resistance, etc
The microstructural features start to play a role as the layer thickness reduces to a certain level, which is very important for applications, such as in gradient refractive index (GRIN) lens designs
It is observed from the results that the material layered structure has a great effect on the mechanical properties and aging
Summary
Polymers have a wide range of applications due to their inherent properties, such light-weight, strength, resistance to chemicals, thermal resistance, etc. Multilayered polymers have been reported to have improved mechanical properties, such as ductility and impact strength, as the layer thickness is reduced [7,8,9]. The 3M Company adopted multilayered polymers for light management in mirrors and the screens of laptop computers These types of polymer films have some unique properties in their applications. The layer thickness ranges from 31 nm to 1,984 nm with a 5-μm film thickness and a film thickness of 31.8 μm to 508 μm with a 496-nm layer thickness These films were thermally aged at 100 °C in a constant temperature oven for up to six weeks. Their mechanical properties, including the modulus of elasticity, tensile strength and ductility, were compared. The microstructural features start to play a role as the layer thickness reduces to a certain level, which is very important for applications, such as in GRIN lens designs
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