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This study explores the influence of mold temperatures below 60(C on thermoplastic polyurethane (TPU) properties during injection molding, focusing on phase separation and its impact on mechanical, thermal, and viscoelastic properties. Using a combination of micro-indentation, temperature scanning stress relaxation, and conventional characterization methods, the research highlights how increased mold temperatures promote more distinct phase separation, enhancing mechanical stability and physical properties. The novel use of micro-indentation revealed a gradient in material stiffness from the surface to the core of injection-molded samples, attributed to differential cooling rates and shear forces, which affect phase separation and crystallinity of the hard domains. These insights are critical for applications requiring specific surface properties and underscore the importance of understanding the interplay between chemical composition and processing conditions for optimizing TPU properties. Furthermore, the paper shows that tensile testing, differential scanning calorimetry, and Shore hardness cannot quantify the effects of mold temperatures below 60(C. The research highlights the influence and importance of chemical composition, rheological history, and thermal history on the properties of TPU. [ABSTRACT FROM AUTHOR]

There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are directly manufactured with a photopolymer material, integrated on an injection moulding tool and subsequently used for IM. Therefore, particular attention has to be paid in order to develop the soft tooling process chain and the IM experimental procedure as detailed in this study. Different combinations of IM parameters are investigated in this work in order to determine the influence of the various process settings on the inserts' performance (lifetime, crack propagation, consistency of the mould surface features). The mould inserts were analysed by three-dimensional optical metrology and evaluated with regard to the different surface features that were affected by the IM process. A three-dimensional thermo-mechanical with phase change model for the analysis of the effects of the IM process on the additive manufactured tools was accomplished in the FE software COMSOL Multiphysics. The potential causes for the insert failure are identified both by means of the IM experiments and the numerical model. The developed model could also predict the thermally induced deformations produced in the mould and identify where this phenomenon would eventually lead to defects in the shape of the parts. The influence of three different temperatures of the insert at 25 °C, 50 °C and 100 °C on the failure of the insert was investigated. Also a detailed discussion about the solidification and temperature changes is given. [ABSTRACT FROM AUTHOR]

The manufacturing of inserts for micro injection moulding made of mortar material is presented in this work. The fabrication of the mortar insert described in this publication relied on a versatile and relatively fast rapid prototyping process based on soft tooling. The mortar insert has a QR code with micro features on its surface, which was replicated in acrylonitrile butadiene styrene (ABS) polymer by the micro injection moulding process. With this approach, it is possible to fabricate hard inserts for micro injection moulding purposes that are able to compete with conventional-made inserts made of tool steel. [ABSTRACT FROM AUTHOR]

• Fabrication of the components with injection molding (IM), soft tooling method. • Influence of thermal ageing on the fracture and lifetime behavior of polymer printed inserts. • The surface roughness of the unaged, aged before IM and aged after IM experiments were evaluated. • Measurement and comparison of the IM unaged and aged parts components. • Thermal ageing leads to crack formations in different areas in the mold inserts. Due to the significant technical benefits of additive manufacturing (AM), its application has grown considerably in recent years. In this respect, the integration of AM in the injection molding (IM) process chain for tooling purposes is an ongoing research topic. In the current study, the design, fabrication and use of a tool inserts for injection molding process fabricated by a vat photopolymerisation technique. Since molds during the injection molding process are subjected to cyclic thermal variation, accelerated thermal ageing was applied on the AM mold inserts to emulate the effect of continuous production on the tool lifetime. The additively manufactured mold inserts were exposed to thermal cycling loading in the range between room temperature up to 100 °C, and then, they were used in the actual injection molding process. According to the obtained results, effects of thermal ageing on behavior of the mold inserts are demonstrated. Moreover, fractographic analysis is performed on the fractured surfaces to determine crack initiation and propagation on the mold inserts. The current study provides insight about ageing and fracture of IM mold inserts produced by vat photopolymerisation , and these results can be used for the development of computational models, future material design and load-carrying capabilities of additively manufactured mold inserts to expand the use of AM for tooling purposes. [ABSTRACT FROM AUTHOR]