Effects of screw speed and feed rate on residence time distribution and axial mixing of wheat flour in a twin-screw extruder

Continuous Direct Mechanocatalytic Suzuki-Miyaura Coupling via Twin-Screw Extrusion

This work establishes the first direct mechanocatalytic reaction protocol within an extruder, focusing on the Suzuki-Miyaura reaction. Through the coating of either the extruder screws or barrel with Pd, we executed the cross-coupling reaction without the reliance on molecular catalyst compounds or powders, and solvents continuously. We identified the influence and interplay of crucial reaction parameters such as temperature, mechanical energy input, residence time, rheology, and catalyst contact time and finally obtained 36 % and 75 % of the reaction product after one and four reactor passes respectively.

Can Continuous Manufacturing of Topical Semisolids by Hot Melt Extrusion Soon Be a Reality?

For more than five decades, pharmaceutical manufacturers have been relying heavily on batch manufacturing that is a sequential, multistep, laborious, and time-consuming process. However, late advances in manufacturing technologies have prompted manufacturers to consider continuous manufacturing (CM) is a feasible manufacturing process that encompasses fewer steps and is less tedious and quick. Global regulatory agencies are taking a proactive role to facilitate pharmaceutical industries to adopt CM that assures product quality by employing robust manufacturing technologies encountering fewer interruptions, thereby substantially reducing product failures and recalls. However, adopting innovative CM is known to pose technical and regulatory challenges. Hot melt extrusion (HME) is one such state-of-the-art enabling technology that facilitates CM of diverse pharmaceutical dosage forms, including topical semisolids. Efforts have been made to continuously manufacture semisolids by HME integrating the principles of Quality by Design (QbD) and Quality Risk Management (QRM) and deploying Process Analytical Technologies (PAT) tools. Attempts have been made to systematically elucidate the effect of critical material attributes (CMA) and critical process parameters (CPP) on product critical quality attributes (CQA) and Quality Target Product Profiles (QTPP) deploying PAT tools. The article critically reviews the feasibility of one of the enabling technologies such as HME in CM of topical semisolids. The review highlights the benefits of the CM process and challenges ahead to implement the technology to topical semisolids. Once the CM of semisolids adopting melt extrusion integrated with PAT tools becomes a reality, the process can be extended to manufacture sterile semisolids that usually involve more critical processing steps.

Conformational changes and physicochemical attributes of texturized pea protein isolate-konjac gum: With a new perspective of residence time during extrusion

The present study aimed to investigate the effects of different extrusion temperatures (110, 130 and 150 °C) and konjac gum addition (0.1 %, 0.2 %, and 0.3 %) on the flow behavior, physicochemical properties and microstructure of extruded pea protein isolate (PPI). The results showed that the textured protein could be improved by enhancing the extrusion temperature and adding konjac gum during extrusion. The water/oil holding capacity of PPI decreased and the SH content increased after extrusion. With temperature and konjac gum content increased, the β-sheet of extruded proteins transformed to other secondary structural components, and Trp residue transformed to a more polar environment, illustrating the changes in protein conformation. All extruded samples presented as yellow hue with little green and higher lightness, while excessive extrusion process reduced the brightness and promoted more formation of browning pigments. Extruded protein showed more associated layered with some air pores, and its hardness and chewiness increased with the increase of temperature and konjac gum concentration. Cluster analysis showed that the addition of konjac gum could effectively improve the quality characteristics of pea protein under low temperature extrusion, and the effect was similar to that of high temperature extrusion product. With the increase of konjac gum concentration, the flow pattern of protein extrusion gradually converted from plug flow to mixing flow, and the disorder degree of polysaccharide protein mixing system was enhanced. Moreover, Yeh-jaw model showed better fitting effect in F(θ) curves compared to Wolf-white.

Insights into Stoichiometry Adjustments Governing the Performance of Flexible Foamed Polyurethane/Ground Tire Rubber Composites

Polyurethanes (PU) are widely applied in the industry due to their tunable performance adjusted by changes in the isocyanate index—stoichiometric balance between isocyanate and hydroxyl groups. This balance is affected by the incorporation of modifiers of fillers into the PU matrix and is especially crucial for PU foams due to the additional role of isocyanates—foaming of the material. Despite the awareness of the issue underlined in research works, the contribution of additives into formulations is often omitted, adversely impacting foams’ performance. Herein, flexible foamed PU/ground tire rubber (GTR) composites containing 12 different types of modified GTR particles differing by hydroxyl value (LOH) (from 45.05 to 88.49 mg KOH/g) were prepared. The impact of GTR functionalities on the mechanical, thermomechanical, and thermal performance of composites prepared with and without considering the LOH of fillers was assessed. Formulation adjustments induced changes in tensile strength (92–218% of the initial value), elongation at break (78–100%), tensile toughness (100–185%), compressive strength (156–343%), and compressive toughness (166–310%) proportional to the shift of glass transition temperatures (3.4–12.3 °C) caused by the additional isocyanates’ reactions yielding structure stiffening. On the other hand, formulation adjustments reduced composites’ thermal degradation onset due to the inferior thermal stability of hard segments compared to soft segments. Generally, changes in the composites’ performance resulting from formulation adjustments were proportional to the hydroxyl values of GTR, justifying the applied approach.

Synergistic toughening of polypropylene with ultra-high molecular weight polyethylene and elastomer-olefin block copolymers

Blends of polypropylene (PP) and ultra-high molecular weight polyethylene (UHMWPE) with elastomer-olefin block copolymers (OBC) were prepared using an ultrasonic twin-screw extruder, and the mechanical, thermal, and rheological properties of the blends were investigated. The interfacial interactions among PP, OBC, and UHMWPE showed that the PP/OBC/UHMWPE blends formed a core–shell structure with UHMWPE as the core and OBC as the shell. The crystallization temperature and the crystallinity of the blends were improved for the heterogeneous nucleation between PP- and OBC-covered UHMWPE particles. Moreover, the mechanical and thermal properties of PP/UHMWPE blends have also been greatly improved by adding OBC. Furthermore, it was evident that the OBC-covered HHMWPE particles became smaller under the application of ultrasonic irradiation, so the interfacial interactions between the particles and the PP matrix were enhanced and the impact strength of the blends was improved.

Blends of polypropylene (PP) and ultra-high molecular weight polyethylene (UHMWPE) with elastomer-olefin block copolymers (OBC) were prepared using an ultrasonic twin-screw extruder, and their mechanical and rheological properties were investigated.

Determination of the Residence Time Distribution in Twin Screw Extruders via Free Radical Modification of PE

The main objective of the present work was to introduce an inline method for measuring the residence time distribution (RTD) of twin screw extruders on the basis of information obtained from the melt free radical modification of polyethylene in a modular intermeshing co-rotating twin screw extruder. The trend of increasing rate of the extruder total torque resulted from replacing the neat polyethylene feed by a mixture of polyethylene and reactants which are chemically capable of creating chainbranching and/or crosslinking reactions was considered as the main information source for evaluating the RTD of the extruder. The RTD results were compared with those obtained from the tracer pulse input method, and good agreement was found. It was also demonstrated that, the present in-line RTD measuring technique has reliability of following the effect of feeding rate, screw speed and reactant concentration on the RTD of the twin screw extruders. It was found that, increasing the feeding rate results in decreasing the minimum residence time, and results in a narrower RTD. At constant feeding rate increasing the screw speed decreased the minimum residence time and broadened the RTD. The results also showed that, reactant concentration and variation of the viscosity along the screw have not appreciable effect on the twin screw extruders RTD.