Wortmann Martin, Krieger Philipp, Frese Natalie, Moritzer Elmar, Hüsgen Bruno
Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, Interaktion 1, 33619 Bielefeld, Germany.
Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
ACS Omega. 2021 Feb 10;6(7):4687-4695. doi: 10.1021/acsomega.0c05436. eCollection 2021 Feb 23.
Polyurethane vacuum casting with silicone molds is a widely used industrial process for the production of prototypes and small batches. Since the silicone casting molds absorb the isocyanate component of the curing PUR casting resin at the cavity surface, the service life of the molds is typically restricted to very few casting cycles. The successive deterioration of the material properties results from the polymerization of the absorbed isocyanate with moisture to polyurea derivatives within the silicone matrix. In this study, we show for the first time the influence of isocyanate absorption on the mechanical properties of silicone elastomers as well as quantitative differences between commercial materials. The changes in mechanical properties were quantified in terms of Shore A hardness, Young's modulus, tensile strength, elongation at break, and complex shear modulus. It was found that the influence of the isocyanate type on the relative property changes of the silicone was significantly greater than that of the silicone used. The results show that, regardless of its hardness, the silicone absorbs considerably less methylene diphenyl diisocyanate (MDI) than hydrogenated MDI, although the latter causes less deterioration of the mechanical properties and achieves a longer mold service life.
使用硅胶模具进行聚氨酯真空铸造是一种广泛应用于原型制作和小批量生产的工业工艺。由于硅胶铸造模具在型腔表面吸收固化聚氨酯铸造树脂的异氰酸酯成分，模具的使用寿命通常限制在很少的铸造周期。材料性能的连续恶化是由于吸收的异氰酸酯与硅胶基质中的水分聚合形成聚脲衍生物所致。在本研究中，我们首次展示了异氰酸酯吸收对硅胶弹性体力学性能的影响以及商用材料之间的定量差异。力学性能的变化通过邵氏A硬度、杨氏模量、拉伸强度、断裂伸长率和复数剪切模量进行量化。结果发现，异氰酸酯类型对硅胶相对性能变化的影响明显大于所使用的硅胶。结果表明，无论硬度如何，硅胶吸收的二苯基甲烷二异氰酸酯（MDI）比氢化MDI少得多，尽管后者导致的力学性能劣化较小且模具使用寿命更长。
