The 3D print material Rigid Polyurethane or RPU70 is tough and has the ability to withstand heat. Products with this material are manufactured in a two-stage dual-curing process. A green product is generated using photo-polymerization in layers within the system applying a UV-light source reflected via Digital Light Processing as planar exposure source. Because of a range of materials with mechanical properties similar to conventional polymers and the smooth part surfaces, DLS demonstrates high potential to be used as a technology for final part (series) production. To record the first, light-induced photo-polymerization reaction of the material, a Photo-differential scanning calorimeter (Photo-DSC) is used. Then, standard DSC measurements are performed with the UV-cured RPU 70 sample. In order to analyze the influence of different exposure times on the final component properties, a tensile test is performed to acquire tensile strengths and elongation at break values. Photo-DSC measurements performed with different exposure times followed by thermal curing show the dependence of the thermal cross-linking reaction on the previously formed network, made in the first process step during photo-polymerization. The trend was validated with standard DSC measurements, showing a strong correlation between thermal cross-linking in the second process step and exposure time settings for parts produced with DLS. Read the complete article: Science Direct
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