Modelling, processing and mechanical properties of aspartic polyurea

Nowadays, polymers are used widely in almost every up-to-date industry. They show high levels of strength-to-weight ratios. Polyurea is a kind of polymer that made of reaction between pre-polymers and specific hardener (diisocyanate). Today's industries are particularly interested in replacing components of their vehicles and parts with reinforced polymers like polyurea and polyurethan. Polyurea has attracted both academic and industrial interests because of capacity to create a dramatic enhancement in properties at various of compounds of diisocyanate and polyamines. Generally, in current study we tried to derive mechanical properties of aspartic polyurea and then attempted to build a proper mechanical model for fabricated material properties. Polyurea has many applications such as coating. For instance, at sport saloons the floor coating must have maximum stiffness beside flexibility. Somewhere else may be there is a need to have a good strength beside sufficient softness against impact loads. During this research the major problem was the creation of gas foams. By studying the stoichiometry and chemometric observations of the reaction it was obtained that these foams were made of carbon dioxide. There were many methods to omit these foams such as using anti-foam additives, carbon dioxide absorber additives, decreasing viscosity and using bubble evacuation system (vacuum). According to our available facilities and tools, we were just able to use anti-foam additives and unfortunately we were unable to omit this malfunction completely, but by controlling process conditions we reduced the amount of bubbles to the lower level. We performed two kinds of experimental test on various polyurea samples. Also different fabrication methods and composition ratio have been used to fabricate modified aspartic polyurea. Uniaxial tension and uniaxial compression tests were performed to characterize the behavior of the materials. In order to choose the appropriate manufacturing protocol and the suitable enhancement for industrial usage a parametric analysis utilized to choose best material in aspect of strength and mechanical properties. Then the extracted data were imported into ABAQUS to capture a suitable hyperelastic model. The evaluated model gave us the ability of future and complex analysis of polyurea in the several mechanical conditions. We were able to produce different kind of polyurea by interfering and changing initial chemical and manufacturing parameters. We aimed on exchanging three parameters of polyurea. These parameters were composition, polymerization mixing speed and polymerization temperature. We attempted to produce different mechanical behavior and measured these parameters to select and compare them with their manufacturing parameters. The best ones contained suitable property of flexibility, strength and stiffness. To achieve these features, after manufacturing several unique samples, the standard mechanical tests carried out. After analyzing the experimental procedures in the result chapter the engineering stress vs, engineering strain curves represented for each sample. By performing data curve fitting process the material coefficients extracted. These coefficients can be recorded as material properties and they would be used instead of raw experimental data. For instance, to analyze a composite plate made of two layers of steel and polyurea there won't be need to insert uniaxial test data to our finite element analyzer machine and these elicited material coefficients would be adequate. As a discussion, we debated about selecting best manufacturing parameters among outputs. By comparing differences between each sample we chose the appropriate manufacturing protocol. It was resulted that polyurea was mechanically strong, specifically in terms of strength to weight. The results showed that the materials have interesting behavior when they uniaxialy compressed, in other word polyurea had very high compressive strength and after unloading the material showed its viscoelastic nature. Polyurea was able to support million times its own weight. we concluded that the polyurea can be utilized to applications that requires high compressive strength and high strain values. The results expressed that the Yeoh and Ogden hyperelastic models can predict the elastic mechanical behaviour of polyurea samples even under large strain compression. Also it is notable that the Observations through the tests showed that the polyurea was strong and useful for static load aspects, also whole tests carried out in room temperature and constant strain rates, so then for those applications which are under dynamic loads or in intense load conditions (impact, explosion and thermal stress-strain problems), extended tests are required. In other words, dynamic mechanical analysis should take place for understanding strength and strain at various strain levels and temperatures. In the next studies the viscoelastic behaviors also should be considered and relative parameters should be obtained then joint with available hyperelastic parameters in this study to build up a very constitutive hyper-viscoelastic model.