Charakterisierung des Lichtstreuverhaltens und der Morphologie von thermotropen Verglasungen auf Thermoplastbasis

Translated title of the contribution: Characterization of light scattering and morphology of thermotropic glazings based on thermoplasts

Michael Seemann

Research output: ThesisMaster's Thesis

Abstract

Thermotropic systems with fixed domains (TSFD) are functional polymer layers, which consist of a thermotropic additive dispersed in a matrix material (mostly a UV curable resin). The additive is serving as scattering domain. Upon reaching a certain threshold temperature (i.e. the melting temperature of the additive) the additive changes its refractive index, which causes the TSFD to change its light transmitting properties reversibly. This thesis is dealing with the production, and characterization of TFSD based on thermoplastic matrix materials. TSFD were prepared by compounding polymethylmethacrylate or cyclic olefin copolymers as matrix materials by various polar and non polar additives. The compounded granules were sheet molded at different processing temperatures. TSFD plates with a thickness of ~0.4 mm were obtained. The samples were characterized as to scattering domain size and distribution. Furthermore solar-optical properties as a function of temperature were analyzed applying UV/Vis/NIR spectroscopy. For layer heating two different heating stages were used and evaluated. Morphological investigations by light microscopy and Atomic Force Microscopy revealed randomly distributed, nearly spherical scattering domains with diameters between 200 nm and 12 µm. The scattering domain size was found to be dependent on the processing temperature. Also the transmittance for solar radiation of the investigated TSFD varied with varying processing temperature. However, no distinct correlation between scattering domain size and the light scattering characteristics of the layers was ascertained. The type of applied heating stage was shown to significantly affect the detected solar transmittance. In heating stage A the sample was heated all-over. Switching temperatures between 59 and 91 °C were recorded. However, this setup caused significant heating chamber recess error which in turn resulted in considerable deviations between the recorded values and the effective radiation transmitted by the sample (high scattering losses). Therefore a calibration of the recorded data was required. Below the switching temperature the TSFD exhibited a hemispheric solar transmittance between 56 and 81 %. Above the switching threshold the hemispheric solar transmittance changed to values between 73 and 90 %. With heating stage B the sample was heated just by one side, which resulted in a non-uniform temperature distribution across the layer thickness. Hence, the switching thresholds of the TSFD were shifted to higher temperatures, with no discrete switching temperature observable. With heating stage B no scattering losses were detectable. The hemispheric solar transmittance changed from 59 to 87 % below the switching temperature to values between 79 and 88 % above the switching threshold. The comparison of the switching characteristics of the TSFD with thermal transitions of the additives measured by Differential Scanning Calorimetry revealed an excellent correlation.
Translated title of the contributionCharacterization of light scattering and morphology of thermotropic glazings based on thermoplasts
Original languageGerman
Supervisors/Advisors
  • Resch-Fauster, Katharina, Co-Supervisor (internal)
  • Pinter, Gerald Gerhard, Supervisor (internal)
Award date17 Dec 2010
Publication statusPublished - 2010

Bibliographical note

embargoed until 17-11-2013

Keywords

  • overheating protection
  • sun protection
  • thermotropic
  • glazing
  • scattering
  • fixed domains
  • spectroscopy
  • atomic force microscopy
  • transmittance
  • treshold temperature
  • switching

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