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In recent years, the drive to adopt sustainable practices and develop eco-friendly processes and products has gained significant momentum in the global polymer industry. A key component of this shift is the increased use of recycled materials, which not only align with environmental goals, but also offer considerable economic advantages. Integrating post-consumer recyclates (PCRs) into manufacturing processes, particularly in injection moulding, holds great potential for reducing CO2 emissions, decreasing reliance on virgin materials, mitigating waste and promoting a circular economy. Nevertheless, a switch to 100% recyclate has not yet been effective or economical in many areas of application, so mixtures of virgin and recyclate material represent a promising approach and must be analysed further. Therefore, this study examines the impact of different virgin/recyclate-mixture ratios on both injection moulding process stability and resulting part quality, focusing on high-density polyethylene (HDPE) and polypropylene (PP) blends. For this purpose, virgin/PCR mixtures are compounded, rheologically analysed using high-pressure capillary rheometry and processed via injection moulding. The process data are analysed, and the produced parts are mechanically and geometrically evaluated. The findings show that for PP, an increasing recyclate content results in a nearly linear improvement in tensile strength and modulus of elasticity without significantly affecting material viscosity, ensuring stable processing conditions. However, part warpage increases with higher recyclate content. In contrast, for HDPE, a higher recyclate content decreases the mixture viscosity, leading to decreased injection pressure and dosing torque during processing. Despite this, the tensile strength and modulus of elasticity improve, while part warpage decreases for HDPE. For both materials, though tensile strength and elasticity increase, higher recyclate contents negatively affect fracture behaviour, as evidenced by breakage patterns and strain at break. The study also demonstrates that the linear mixing rule can be applied to process parameters and part geometry characteristics for virgin/recyclate mixtures, facilitating the integration of recyclate content into product development.

Production Planning and Control involves combinatorial optimization problems subject to domain-related constraints. Hence, decision-support systems are required to support operators in finding suitable production scheduling models that match the conditions on the real shopfloor. Digital Shadows were introduced to solve this task by automatically gathering suitable models and the required input data to provide decision-support. Therefore, a standard definition of production scheduling models and their grouping within a model catalog is required in the virtual world. In this contribution, we introduce an Asset Administration Shell submodel that defines production scheduling models based on Graham’s three-field notation, which is independent of the underlying production process. We consider metadata, which ensures those models are FAIR, i.e. findable, accessible, interoperable, and reusable. In addition, we build a model catalog for production scheduling models in the injection molding domain as the foundation for implementing a decision-support system based on the Digital Shadows.

Plastic/metal hybrid components made of amorphous thermoplastics such as polycarbonate and light metals such as aluminum offer potential to be used in modern automotive headlights to meet the high requirements for tolerances and surface quality. A microform-fit joining approach is used to join plastics and metals, which combines the advantages of material-fit and form-fit joining processes while at the same time avoiding some of the disadvantages of the respective joining approaches, such as stress peaks or the use of additional chemicals. For this purpose, the light metal component is microstructured through laser ablation. To ensure the functional safety of electrical components, the media tightness of the hybrid component is tested with a pressure drop test. An influence of the structure arrangement, the structure spacing and the molding compound on the media tightness can be determined. The highest media tightness can be achieved with a ring-shaped structural arrangement in which the microstructures are orientated orthogonally to the outlet direction of the test medium. The media permeability of a ring-shaped structure arrangement with a structure spacing of 500 µm is 0.42 cm3/s for test specimens made of aluminum and polycarbonate. As the value is below the threshold value of 12 cm3/s, watertightness up to an overpressure of at least 0.5 bar can be concluded.

This paper investigates if the polar groups induced by a plasma treatment can increase the lap shear strength of laser-joined metal and plastic hybrids. Optimal laser joining parameters for cold-rolled AISI304–polyamide 6.6 and sandblasted AISI304–polypropylene hybrids were developed at 2.85 MPa and 4.22 MPa, respectively. The surface free energy was doubled for all used plasma gases to a value of ca. 80 mN m−1 at 180 s. The plasma-treated samples were joined and tested. The arithmetic means of the plasma-treated hybrids’ lap shear strength with polyamide 6.6 varied slightly, but all measured values were within the range of the untreated samples. Residue on the sheared metal samples indicated covalent bonds between AISI304 and polyamide 6.6. The lap shear strengths of the plasma-treated polypropylene hybrids were significantly reduced between −30.8% and −53.3%, depending on the used plasma gas. This was attributed to the over-aging and development of low-molecular-weight oxidized materials, which led to a weak boundary layer. No residue of polypropylene was found on treated or untreated lap shear samples. No correlation between the surface free energy and lap shear strength could be found.

Abstract One vision of industry 4.0 is an autonomous shopfloor configuration. A possibility to transfer this vision to reality is realizable with Digital Shadows. As Digital Shadows are well defined in research, challenges for seamless integration in production are still an open research topic. The main challenge is the enrichment of semantics on the domain in a standardized format that enables multilateral communication between all assets. To overcome these challenge, tools have to be developed to support domain experts in building and integrating Digital Shadows without knowledge of modeling and programming. This article demonstrates the main challenges of this objective and proposes a research agenda to close this research gap.

The material-inherent specific volume behavior of polymers is highly important for producing dimensionally accurate injection molded parts since the shrinkage and the shrinkage-induced warpage are attributable to the specific volume behavior. Thereby, the prevalent process parameters melt temperature and cavity pressure significantly influence the prevailing specific volume. Many empirical models describe this pressure-specific volume-temperature (pvT) behavior.To minimize part warpage, a segmented dynamic mold temperature control has been developed which aims to homogenize the specific volume of a platen-shaped geometry. The mold temperature control is thereby controlled by a model predictive control concept, which predicts the local specific volume using an empirical pvT-model. A modified Tait-pvT-model is used for the prediction, which considers the effect of the cooling rate on the specific volume. To achieve homogenization of the local specific volume, the pvT-model is validated regarding its prediction accuracy by comparing the predicted specific volumes with specific volume measurements of molded test specimens using processing points with varying cooling rates. For the predictions of the final specific volumes, two approaches regarding the selection of the cooling rate were used. The results show that the selection of the cooling rate within the modified Tait model has a significant impact on the calculated final specific volume.

The pressure-specific volume-temperature (pvT) diagram is well established in science and industry for plastics injection molding purposes. However, the exact specific volume during the process cannot be measured and the help of a pvT model is necessary. The pvT model is based on the data measured under standard conditions and might not reflect the specific volume at process level. In order to know the exact variation of the specific volume, a pvT testing device was used to simulate the injection molding process. Four parameters (starting temperature, holding pressure, holding-end temperature and cooling rate) corresponding to injection temperature, holding pressure, holding time and cooling time were considered. The semi-crystalline polypropylene (PP) and the amorphous acrylonitrile-butadiene-styrene (ABS) were employed. The design of experiments (DoE) method was applied to analyze the influences of these parameters on the changes of the specific volume during the simulated injection molding cycles. The results demonstrated that the specific volume especially at the phase transition and shrinkage stages is significantly influenced by the complicated injection molding process. The starting temperature has a great effect on the specific volume but has little effect on the shrinkage. The specific volume decreases non-linearly with decreasing cooling rate during the shrinkage stage.

Few studies have examined the process dependence of the pressure–specific volume–temperature (pvT) behavior of polymers. Especially, the specific volume variation during heating is often ignored, but for certain processing techniques such as plastic welding and additive manufacturing, special consideration should be given. In this study, a new pvT model was proposed to determine the specific volume evolution of polymers during cooling and heating processes. The process dependence of pvT behavior of polymers was discussed in theory, and the influences of starting temperature and cooling/heating rates were considered in the modeling. The pvT behavior of a semi-crystalline polymer, polypropylene (PP), was measured. Mathematical model parameters were determined through the fitting of the experimental pvT data. The fitted results were in good agreement with the experimental data, which showed that the proposed model is accurate and effective. The R2 value of 99.82% and the average absolute percent deviation of 0.21% were obtained. The process dependent pvT model is simple and has broad application prospects in polymer physics and polymer processing.

Distortion (1), residual stresses and hot cracks can facilitate significant decreases in quality characteristics of casting products. Their reduction by a suitable component design (2) and process control is therefore desirable. In the casting process, these characteristics are assumed as a result of the combination of solidification shrinkage paired with the local self-feeding and the geometric constraints imposed on the component by the mold. In gravity die casting (3) of aluminum (4) with thermally well conducting and rigid metal molds, the control of solidification through a localized adjustment of the heat balance (5) appears to be a suitable approach to minimize these effects. The development of an experimental setup for the assessment of the interdependencies of the alloy, casting geometry and cooling are described in this work. A first series of experiments with A356 aluminum alloy and the introduction to the different methods of evaluation are presented. Furthermore, an approach to improve the understanding of the underlying mechanisms is outlined.

The permeability of the semi-solid state is important for the compensation of volume shrinkage during solidification, since insufficient melt feeding can cause casting defects such as hot cracks or pores. Direct measurement of permeability during the dynamical evolution of solidification structures is almost impossible, and numerical simulations are the best way to obtain quantitative values. Equiaxed solidification of the Al-Si-Mg alloy A356 was simulated on the microscopic scale using the phase field method. Simulated 3D solidification structures for different stages along the solidification path were digitally processed and scaled up to generate 3D models by additive manufacturing via fused filament fabrication (FFF). The Darcy permeability of these models was determined by measuring the flow rate and the pressure drop using glycerol as a model fluid. The main focus of this work is a comparison of the measured permeability to results from computational fluid flow simulations in the phase field framework. In particular, the effect of the geometrical constraint due to isolated domain walls in a unit cell with a periodic microstructure is discussed. A novel method to minimize this effect is presented. For permeability values varying by more than two orders of magnitude, the largest deviation between measured and simulated permeabilities is less than a factor of two.

The absence of the influence of cooling rate in the pressure–specific volume–temperature (pvT) models makes them inadequate in the process simulation of injection molding. This work derived new equations of state (EoS) from the traditional two-domain Tait model that describes the pvT behavior of semi-crystalline polymers in both molten and solid state. Especially, the cooling rate was considered. The second aim of this work is to solve the discontinuity problem of the traditional two-domain Tait model. A continuous two-domain Tait EoS was developed. A good agreement between the calculations and experimental results was achieved. The new pvT models were successfully applied in the prediction of specific volume as a function of temperature, pressure and cooling rate during injection molding. A higher value of the specific volume was predicted when the cooling rate was considered. Combining the continuous two-domain Tait EoS, more accurate results can be obtained especially at the transition phase from melt to solid of the semi-crystalline polymer. Keywords: pvT, Specific volume, Semi-crystalline polymer, Equation of state, Cooling rate, Injection molding

Isosorbide-containing copolycarbonate (Bio-PC) is a partly biobased alternative to conventional bisphenol A (BPA) based polycarbonate (PC). Conventional PC is widely used in polymer processing technologies including thermoplastic foaming such as foam injection molding. At present, no detailed data is available concerning the foam injection molding behavior and foam properties of Bio-PC. This contribution provides first results on injection-molded foams based on isosorbide-containing PC. The structural foams were produced by using an endothermic chemical blowing agent (CBA) masterbatch and the low pressure foam injection molding method. The influence of weight reduction and blowing agent concentration on general foam properties such as density, morphology, and mechanical properties was studied. The test specimens consist of a foam core in the center and compact symmetrical shell layers on the sides. The thickness of the foam core increases with increasing weight reduction irrespective of the CBA concentration. The specific (mechanical) bending properties are significantly improved and the specific tensile properties can almost be maintained while reducing the density of the injection-molded parts.