Sara Liparoti

The energy‐intensive residential sector critically requires sustainable and highly efficient thermal insulation solutions. Due to the increasing demand for complex‐shaped parts, it remains challenging to give them insulating properties. Indeed, traditional processing methods for foam production offer limited control over the internal architecture, a key factor in performance. This paper aims to fill that gap by using Material Extrusion Additive Manufacturing (MEAM) as a new technique to produce tailored atactic Polystyrene components, leveraging additive manufacturing's ability to create complex geometries and control the internal structure (lattice)—capabilities that are usually restricted by traditional methods. Polystyrene is a favored material due to its lower thermal conductivity compared to other polymeric materials; however, conventional manufacturing processes, such as extrusion foaming or foam injection molding, are limited to standardized geometries and lack precise control over the internal cellular structure, a critical factor in determining thermal insulating capabilities. The MEAM process was optimized, revealing that a bed temperature above the glass transition temperature (T _g ) is crucial for interlayer adhesion, while moderate printing speeds (e.g., 2200 mm/min) yielded the best mechanical performance. Thermal conductivity was found not to be linearly dependent on the infill density, showing a minimum of 0.03 W/(mK) at 25% infill density for the octahedral structure. Numerical simulations, validated against experimental heat flux data, confirmed the significance of natural convection within the air‐occluded cells, supported by high Jeffreys’ numbers (∼10 ⁵ ). The closed‐cell structure obtained by MEAM positively contributes to thermal insulation by reducing the effects of natural convection within the cells. This work established MEAM as a promising pathway for fabricating structurally optimized insulators with performance that can rival or be tailored beyond traditional foams.

Colon-targeted delivery systems offer a promising approach for local drug administration. In this study, we developed a customized polymeric blend for this purpose, combining polyethylene glycol (PEG), polycaprolactone (PCL), and hydroxypropyl methylcellulose (HPMC). Although PEG and PCL have been extensively studied, the inclusion of HPMC in such blends remains underexplored; however, its use in this context shows significant potential due to its pH sensitivity. To achieve this, various formulations were tested to optimize the thermomechanical and release characteristics of capsules produced through injection molding. Three blends containing 22, 24, and 34 wt% HPMC were processed and analyzed using rheological methods, ATR-FTIR, TGA, DSC, SEM, and in vitro release tests with methylene blue as a model compound. Simulated pH-release tests (pH 2.5, 5, and 6.8) showed minimal release in gastric and intestinal environments, with controlled and sustained release under colonic pH conditions. It was also observed that the initial HPMC content affects the release rate of the model compound. Specifically, when the blend contains 34% HPMC, approximately 38% of the compound is released within 12 h and 73% within 24 h. These results highlight the potential of pH-sensitive polymer blends as effective platforms for colon-targeted drug delivery. A model illustrating how the release rate depends on pH value and HPMC amount was also proposed and validated. The process was considered to happen in two stages: initially, the release medium penetrates the capsule and solubilizes the model compound; then, the model compound is released into the surrounding environment.

Material Extrusion Additive Manufacturing (MEAM) offers the ability to manufacture complex geometries through layer‐by‐layer deposition. MEAM involves fast heating and cooling of polymers, processes that involve thermal expansion and contraction of materials that may undergo phase transitions. These phenomena may lead to warpage: distortion of the printed parts or deviation from the intended geometry, which significantly compromises the dimensional accuracy and functionality of parts. Mitigation or even cancelling warpage has become one of the roadblocks toward further widespread application of MEAM technology, a target that requires a thorough understanding of the phenomenon. To contribute to this goal, this review presents and discusses the current knowledge of warpage in MEAM, starting with a general presentation of the technology and its intrinsic features, followed by details of the fundamental mechanisms of warpage, highlighting the crucial interaction between processing parameters, material characteristics, and part geometry. A thorough analysis of the experimental methodologies used to quantify warpage is presented, alongside a comparative exploration of warpage behavior in amorphous and semicrystalline polymers. The state‐of‐the‐art of current modeling approaches aimed at predicting the warpage phenomenon is also presented and discussed, with a focus on the capability to effectively consider the complex thermo–mechanical history specific to MEAM.

Fused filament fabrication (FFF) is an inexpensive and flexible additive manufacturing technology, widely used for thermoplastic polymers to produce parts with complex geometry. However, some thermoplastics may undergo thermal degradation upon FFF, with loss of material properties. This is the case of poly( L ‐lactic acid) (PLLA), a biodegradable and bio‐based semicrystalline polyester, largely used in FFF. For the temperature‐sensitive polymers, FFF processing should be optimized, to limit as much as possible thermal degradation. In this work, the minimum temperature and time needed to melt PLLA, thus the best conditions to limit thermal degradation, have been determined by calorimetry. The attained results were used to produce 3D printed parts using a PLLA filament: the analysis of the effect of nozzle temperature and extrusion rate (the main processing parameters linked to polymer melting kinetics) on the thermal properties of the printed parts confirmed the need of proper setting of the melting conditions to optimize properties of FFF 3D printed products. Modeling and simulation of flow and temperature fields inside the liquefier, accounting for the filament melting, are also proposed and used to evaluate the molten fraction in several printing conditions.

When in contact with water, poly(lactic acid), PLA, undergoes several physical changes. A very evident one is opacification, namely the change from the typical transparent appearance to a white opaque color. This phenomenon is particularly significant for many applications, including packaging, since opacity hinders the possibility of a clear look of the packed goods and also worsens the consumers’ perceptions. In this work, we report an analysis of the time evolution of the phenomenon in different conditions of temperature and water concentration. The results allow us to define a time-scale of the phenomenon and to put it in relationship with the temperature and water content inside the material. In particular, opacification proceeds from the outer surface of the specimens toward the center. Both craze formation due to hydrolysis and crystallization contribute to the opacification phenomenon. Opacification becomes faster as temperature increases, whereas the increase in the solution density has the opposite effect. A model for describing the evolution of opacification was proposed and found to be consistent with the experimental data.

With the aim to produce solid fats with a high percentage of unsaturated fatty acids, oleogels based on olive and peanut oil with different concentrations of beeswax (BW) and glycerol monostearate (GMS) as oleogelators were studied and compared. The critical oleogelator concentration for both BW and GMS was 3%. Thermal properties of the developed GMS-based oleogels pointed to a polymorphic structure, confirmed by the presence of two exothermic and endothermic peaks. All developed oleogels released less than 4% of oil, highlighting their high oil binding capacity. A morphology evaluation of oleogels showed platelet-like crystals, characterized by a cross-sectional length of 50 μm in BW-based oleogels and irregular clusters of needle-like crystals with a higher diameter in GMS-based oleogels. BW-based oleogels showed a solid fat content ranging from 1.16% to 2.27%, and no solid fat content was found at 37 °C. GMS-based oleogels reached slightly higher values of SFC that ranged from 1.58% to 2.97% at 25 °C and from 1.00% to 1.75% at 37 °C. Olive oil-based oleogels with GMS showed higher firmness compared with BW-based ones. The stronger structure network in olive oil/GMS-based oleogels provided a real physical barrier to oxidants, showing a high oxidation stability.