Thermo-mechanical and hygroscopic behaviour of semicrystalline polymer foils
Citation for published version (APA):
Poluektov, M., Dommelen, van, J. A. W., & Geers, M. G. D. (2010). Thermo-mechanical and hygroscopic behaviour of semicrystalline polymer foils. Poster session presented at Mate Poster Award 2010 : 15th Annual Poster Contest.
Document status and date: Published: 01/01/2010 Document Version:
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Thermo-mechanical and
hygroscopic behaviour
of semicrystalline polymer foils
M. Poluektov, J.A.W. van Dommelen, M.G.D. Geers
Mechanics of Materials, Holst Centre
/ department of mechanical engineering
Aim of the project
Semicrystalline polymers, particularly polyethylene
naphthalate (PEN) and polyethylene terephthalate (PET) foils, are widely used as substrates in manufacturing of plastic electronics, like the backplane of a flexible display or plastic memory for RFID (radio frequency identification), in cost-effective roll-to-roll processes (figure 1). Since the scale of technological processes is constantly decreasing, a tool is needed that precisely predicts thermo-mechanical as well as hygroscopic behaviour of substrates on a micro level in order to print electronics with high accuracy. The objective of this project is to develop such multiscale
modelling tool that would characterise dimensional stability of the foils during lithographic processing and foil handling.
Figure 1: Holst Centre roll-to-roll line (Holst Centre Executive Report 2009, Eindhoven).
Approach
Material structure. The PET and PEN foils are biaxially
oriented and thermally stabilised, with a typical thickness 25-125 µm. In unstretched material, on a small scale, a 2D spherulitic morphology can be observed. These spherulites are actually an assembly of radial crystalline lamellae
separated by amorphous layers [1]. Stretched films
possess a preferred orientation of molecular chains. Their elastic and viscoplastic behaviour depends on many
factors, such as crystallinity, the initial crystallographic and morphological texture, mechanical properties of individual phases [2].
Figure 2: A schematic representation of various levels involved in the multiscale model for unoriented semicrystalline polymer.
Modelling technique. During this research, a detailed
micromechanical model will be constructed. The starting point will be the creation of a model for unstretched foils (as is schematically represented in figure 2) and the next challenge will be to predict anisotropic properties of
oriented PET and PEN foils. Material is considered to be an assembly of two-phase layered composite inclusions consisting of crystalline and amorphous parts. Parts
themselves are supposed to deform homogeneously. A rigid amorphous layer (i.e. the “interphase”) can be
included there as well. This inclusion is a basic structural element of the material in any state, with spherulitic or
oriented morphologies. The most appropriate technique to link this microstructure with the macro-model will be
investigated.
Future work & Valorisation steps
The predictive tool for the thermo-hygro-mechanical response of semicrystalline materials will enable the
industrial partner to understand their material requirements for the roll-to-roll application and to develop the roll-to-roll process to be compatible with the material properties.
References
[1] B. J. Lee et al., Polymer (1993) 34, 3555–3575.
[2] X. Guan et al., Polym. Eng. Sci. (2004) 44, 433–451.
