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The additive manufacturing of parts made from close-to-production materials poses a great challenge. One example are highly viscous silicones, as used in injection moulding. For small production quantities, the manufacturing of injection moulds is uneconomical. This paper presents tensile specimens printed with an in-house developed dispensing system, which are analysed for air cavities (micro-CT scans) and mechanical properties. Based on the results, advice for the design and slicing parameters of parts using high-viscosity silicones in AM by means of material extrusion are developed. [ABSTRACT FROM AUTHOR]

Despite extensive research on corporate social irresponsibility (CSI) and its repercussions, there is no straightforward answer to its impact on newly appointed CEOs. In this study, we seek to examine the consequences of firms deviating from their social responsibilities, particularly in the context of the new CEO's initial compensation. We argue that firms' engagement in CSI leads to higher initial pay for new CEOs. The higher pay can be seen as a form of compensation for the risk, as CEOs face considerable uncertainty about the potential negative impact on their own reputation by joining such firms. We further propose that this impact is contingent on new CEOs' tolerance for the risk of negative reputation spillover. Specifically, we posit that a positive association between CSI and new CEO compensation is stronger for CEOs with greater prosocial orientation but weaker for CEOs with higher career variety. We support our argument with 1,168 observations of firm-CEO year-level data from 2007 to 2019. Our findings show that socially irresponsible firms pay a premium for new CEOs and that the amount of this premium depends on the risk tolerance of the CEOs. [ABSTRACT FROM AUTHOR]

For the continuous production of foam products, the extrusion process is commonly used. Typical extrusion systems include an extruder for melting and mixing the thermoplastic material(s) as well as an extruder for cooling the melt. Both tasks can also be performed in one extruder. Between these extruders or extruder zones the blowing agent (e.g. CO2, N2) is injected into the melt with relatively high pressure. This study presents a foam extrusion process utilizing a twostage- screw in which the blowing agent is injected at a low-pressure range and extruded as a strand. The study uses PP as well as nitrogen and carbon dioxide as blowing agents which are widely used for foaming. The screw concept makes it possible to produce a blowing agent loaded polymer melt with the present pressure of a standard gas bottle (or other gas storage devices) thus eliminating the need for expensive gas cooling, dosing and pumping technology. The influence of melt temperature and gas injection pressure on foam quality (expansion ratio, cell structure) is investigated. The produced foam has a regular cell structure. [ABSTRACT FROM AUTHOR]

This study presents an improved VOIGT law based model which incorporates the surface tension between filler and matrix material. VOIGT law based models require perfect adhesion between fibers and plastic material, which not always occurs. This study deals with the adhesive bonding conditions between matrix and fibers. The harmonic arithmetic mean equation of surface tension by WU is incorporated into a VOIGT law based model. For the experimental validation of this model different fiber reinforced compounds and test specimens are produced. Young’s modulus, tensile strength as well as fiber length, orientations and surface tensions are measured. [ABSTRACT FROM AUTHOR]

In this study, the flow behaviour of low density polyethylene (LDPE) filled with different volume fractions of wood particles and glass beads have been investigated by means of high pressure capillary rheometry in consideration of different particle sizes. The strongly exhibited shear thinning flow behaviour of the investigated polymer-compounds can be well described by the Ostwald – de Waele power law relationship. The measurements showed that interparticle interactions are differently exhibited depending on the size and aspect ratio of the particles. Interparticle interactions can be taken into account by the interaction exponent, defined as the ratio between flow exponent of the suspension and flow exponent of matrix polymer. The interaction exponent shows a good correlation with the flow consistency index. Consequently, this correlation function can be described as an interaction function. On the basis of a generalized interaction function, that considers the transition from negligibly interactions to the domain of non-negligible interactions, the shift factor and the flow behaviour of the suspensions have been estimated with high accuracy. [ABSTRACT FROM AUTHOR]

The planetary roller extruder is well known for its superior mixing performance and its exact temperature control capabilities. Therefore it is widely used in the polymer industry for the compounding of shear- and temperature sensitive materials like PVC or Wood Plastic Composites. In contrast to the considerable amount of scientific work that deals with investigation, modeling or simulation of the process behavior of single and twin screw extruders, there are only few publications about the planetary roller extruder. Due to increased quality requirements and the trend to cost reduction by process optimization, this is increasingly becoming a problem for plant construction and processing companies. In our former work first analysis of the plastics melting process in planetary roller extruders were conducted and models describing these processes were published. However the influences of pellet diameter or inorganic filler were not considered. As a consequence the process models are only valid for a partial amount of the materials processed on planetary roller extruder. This paper presents experimental melting behavior investigations of powder, micro pellets and standard pellets. Furthermore the influence of filler amount is examined with standard pellets. At these experiments the melting initiation and the melting propagation is determined. Based on the experimental results, a theoretical consideration for melting in planetary roller extruders is proposed. [ABSTRACT FROM AUTHOR]