TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias A1 - Bohmeyer, W. A1 - Lange, K. T1 - Investigation of the crosslinking behaviour of ehtylene vinyl acetate (EVA) for solar cell encapsulation by rheology and ultrasound N2 - EVA is a widely used material for the encapsulation of photovoltaic modules. It melts at elevated temperatures, and seals the module before it is crosslinked at temperatures above 130 °C by a peroxide-initiated crosslinking reaction. EVA has good optical properties necessary for application in solar modules. For process optimization and quality management, a method for the quick and reliable characterization of EVA crosslinking behaviour is of great value. Here, the practicability of ultrasound for online crosslinking monitoring is demonstrated. A sound velocity increase of about 8 m/s during the crosslinking reaction is found. The ultrasound results are compared with rheometer measurements performed with a curemeter typically used for the investigation of rubber crosslinking. KW - Ethylene vinyl acetate KW - EVA KW - Crosslinking KW - Ultrasound KW - Rheology KW - Curemeter KW - DSC PY - 2012 U6 - https://doi.org/10.1016/j.polymertesting.2012.07.004 SN - 0142-9418 VL - 31 IS - 7 SP - 904 EP - 908 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-26291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Stark, Wolfgang A1 - Bohmeyer, W. ED - Karbhari, V.M. T1 - Non-destructive evaluation (NDE) of composites: using ultrasound to monitor the curing of composites N2 - Typical composite materials for lightweight construction consist of a fibre (glass or carbon) reinforced thermosetting matrix. The impregnation of the fabric is made with liquid resin – usually epoxy resin or unsaturated polyester resin are used. The main processing methods are resin transfer moulding (RTM) and prepreg technology often used in combination with autoclave curing. After shaping, the resin must be cured. The final properties of the produced parts depend on the curing degree and the final glass transition temperature. Analytical methods and the use of ultrasound for online cure monitoring in the manufacturing process are introduced. Examples for the application of ultrasonic cure monitoring for the production of composite parts for traffic systems are also covered. KW - Epoxy KW - DSC KW - DMA KW - Kinetic KW - Autoclave KW - Curing KW - Glass transition KW - Curing behaviour KW - Curing degree KW - Rheology KW - Differential scanning calorimetry KW - Dynamic mechanical analysis KW - Sound velocity KW - Sound damping KW - Resin transfer moulding KW - RTM KW - Prepreg PY - 2013 SN - 978-0-85709-344-8 SN - 978-0-85709-355-4 U6 - https://doi.org/10.1533/9780857093554.1.136 SN - 2052-5281 SN - 2052-529X N1 - Serientitel: Woodhead publishing sereies in composites science and engineering – Series title: Woodhead publishing sereies in composites science and engineering VL - 43 IS - Part 1 / Chapter 7 SP - 136 EP - 181 PB - Woodhead Publishing Ltd CY - Cambridge, UK AN - OPUS4-28848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -