Twin-screw Extruder Research Articles

Study on distribution of hydroxyapatite (HA) in twin screw extruded cum injection moulded polylactic acid (PLA) composites and their effect on mechanical property

Hydroxyapatite (HA) reinforced polylactic acid (PLA) composite is the most investigated material for biodegradable implant applications such as screws and plates. The objective of this work is to test hypothesis of distribution of HA in PLA composite influence on the variations in the properties of the composites. Investigation was done for the distribution of HA in PLA injection mould (IM) composites for the various concentrations (2 to 8 wt.%) and their effect on mechanical properties such as flexural and tensile test. Proportionate quantity of HA was introduced at fixed intervals in a twin screw extruder for the preparation of PLA composites pellets containing in various wt.% of HA. The distribution of HA in IM PLA composite specimens was analysed by elemental mapping using scanning electron microscope (SEM) and also by estimation of residue (HA) after burn out test of sampling of specimens. Differential scanning calorimetry (DSC) was used for the study of effect of HA in PLA composites. The value of standard deviations of mechanical properties, taken as a rudimentary measure of reliability of IM PLA-HA composites, was found to have influence from the distributions of HA. Among the composites studied, PLA-HA composite with 4 and 5 HA wt.% found exhibiting reliable mechanical property due to crystallinity of 31.83% and a comparatively better homogenous dispersion of HA in PLA. A case study of distribution of HA in a product, namely, bone screw, promulgated the issues of IM PLA-HA composites for biomedical applications.

Thermomechanical-chemical devulcanization of ground tire rubber

Abstract We developed a thermomechanical devulcanization process of ground tire rubber (GTR) by incorporating chemicals to achieve better devulcanization. The samples were devulcanized in a twin-screw extruder with the help of three types of chemicals that aid devulcanization: N-(cyclohexylthio) phthalimide (PVI), dibenzamid diphenyl disulfide (DBD) and dialkyl-pentasulfide (DPS, commercialized as Aktiplast 79). We characterized the resulting devulcanizates by Soxhlet-extraction, and produced vulcanized sheets, which we characterized mechanically and examined the vulcanization process. We found that all chemicals facilitated better devulcanization and the devulcanizate had a more rubber-like behavior during mixing. Vulcanization was also slightly improved and reversion was reduced. When revulcanized, the rubber had improved strain at break and tear strength.

Compatibility study of recycled Polypropylene (PP)/Poly(ethylene terephthalate) (PET) blends nanocomposites with PP‐g‐MAH: Modeling of twin screw extrusion

AbstractAlthough the utilization of recycled polymers is essential to sustain the environment, conventional recycled polymers face limitations in application due to the degradation of their properties caused by impurities. To solve the problem the performance deterioration of these recycled polymers, this study aimed to enhance their compatibility by chemically adding polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) and physically manipulate a screw profile by using an extrusion simulation program. As a result of applying the optimized extrusion process set by the simulation program, significant improvements in the compatibility and dispersion of fillers within the polymer were observed through scanning electron microscopy image analysis. In addition, through detailed analysis of rheological data, the positive impact of adding compatibilizer and changing screw profile on rheological properties was demonstrated. As the compatibility of recycled polymer blends improved, tensile strength increased by approximately two‐fold and thermal conductivity was significantly improved, which were decisive factors in dramatically enhancing the performance of recycled polymers. These improved polymer properties provide an opportunity for recycled polymers to be applied more broadly and will expand the potential for new applications in various industrial fields.

Effect of twin-screw extrusion pretreatment on starch structure, rheological properties and 3D printing accuracy of whole potato flour and its application in dysphagia diets

Twin-screw extrusion pretreatment has great potential for the development of three-dimensional (3D) printed food as dysphagia diets. This study aimed to investigate the effect of twin-screw extrusion pretreatment on starch structure, rheological properties and 3D printing accuracy of whole potato flour and its application in dysphagia diets. The results indicated that twin-screw extrusion pretreatment was found to change chain length distributions, short-range ordered structure and relative crystallinity of whole potato flour (WPF), thereby improving its 3D printing performance. With the increasing proportion of long linear chains (DP > 12), the intensity of hydrogen bonds, linear viscoelastic region, storage modulus (G′), loss modulus (G″), viscosity and n of whole potato flour paste were increased, enhancing high printing accuracy and shape retention of 3D printed samples with a denser microstructure and smaller pore diameter distribution. The whole potato flour paste extruded with a peristaltic pump speed at 5.25 mL/min (WPF-4) displayed the highest printing accuracy with excellent rheological properties, good water distribution state and dense network structure, which classified as class 5 level dysphagia diets. This research provides an effective guidance for the modification of whole potato flour using twin-screw extrusion pretreatment as 3D printed food inks for dysphagia patients.

Ultrasound-Assisted Extrusion Compounding of Nano Clay/Polypropylene Nano Compounds.

The incorporation of nanoparticles can significantly enhance the properties of polymers. However, the industrial production of nanocomposites presents a technological challenge in achieving the proper dispersion of nanoparticles within the polymer matrix. In this work, a novel device is presented that can be seamlessly integrated with standard twin-screw extruders, enabling the application of ultrasonic vibration to molten polymeric material. The primary objective of this study is to experimentally validate the effectiveness of this technology in improving the dispersion of nanoparticles. To accomplish this, a comparative analysis was carried out between nanocomposites obtained through conventional compounding extrusion and those processed with the assistance of ultrasonic vibrations. The nanocomposites under investigation consist of a polypropylene (PP) matrix reinforced with nano clays (Cloisite 20A) at a target loading ratio of 5% by weight. To comprehensively evaluate the impact of the ultrasound-assisted compounding, various key properties were assessed, such as the melt flow index (MFI) to characterize the flow behavior, mechanical properties to evaluate the structural performance, oxygen barrier properties to assess potential gas permeability, and microstructure analysis using Scanning Electron Microscopy (SEM) for detailed morphology characterization. The results suggested an improvement in nanoparticle dispersion when using the ultrasound device, particularly when the intensity was adjusted to 60%.

Functional Upcycling of Polyurethane Thermosets into Value-Added Thermoplastics via Small-Molecule Carbamate-Assisted Decross-Linking Extrusion.

The cross-linked structures of most commodity polyurethanes (PUs) hinder their recycling by common mechanical/chemical approaches. Catalyzed dynamic carbamate exchange emerges as a promising PU recycling strategy, which converts traditional static PU thermosets into reprocessable covalent adaptable networks (CANs). However, this approach has been limited to thermoset-to-thermoset reprocessing of PU CANs, accompanied by their well-preserved network structures and extremely high viscosities, which pose challenges to processing and certain applications. This study reports a catalytic decross-linking extrusion process aided by small-molecule carbamates, which can upcycle PU thermosets into easily processable and functional PU thermoplastics in a solvent-free and high-throughput manner. Key to this process is the employment of small-molecule carbamates as decross-linkers to simultaneously deconstruct cross-linked PUs and functionalize the decross-linked PU chains, through catalyzed carbamate exchange reactions in a twin-screw extruder. This strategy applies to both aromatic and aliphatic cross-linked PU films and foams, and the amount of small-molecule carbamates required to decross-link PU networks is determined through thermal, chemical, and structural analyses of the resulting extrudates. This approach is generalizable to small-molecule carbamates with various steric/electronic structures and chemical functionalities including methacrylate, anthracene, and stilbene groups. The chain-end functionalization is confirmed by analyzing the purified decross-linked extrudates after dialysis. This thermoset-to-thermoplastic extrusion process represents a powerful approach for upcycling postconsumer PU thermosets into a library of thermoplastic PUs with controlled molecular weights and chain-end functionalities for diverse applications, including adhesives, photoresins, and stimuli-responsive materials, as demonstrated herein. In the future, this strategy could be extended to upcycle many other step-growth networks capable of undergoing catalytic bond exchange reactions, such as cross-linked polyureas and polyesters, contributing to plastic waste management in general.

Process stability optimization of the twin-screw extrusion adapted for concentrated cellulose fibrillation

Process stability optimization of the twin-screw extrusion adapted for concentrated cellulose fibrillation

Effects of Carbon Fiber Content on the Crystallization and Rheological Properties of Carbon Fiber-Reinforced Polyamide 6.

Carbon fiber (CF)-reinforced polyamide 6 (PA6) composites have an excellent performance, attributed to properties such as light quality, high strength, and vibration reduction, and they are widely used in fields such as aerospace and transportation. Four kinds of carbon fiber-reinforced polyamide 6 (CF/PA6) composite pellets with carbon fiber contents of 20, 30, 40, and 50 wt.% were prepared using twin screw extrusion. The results were characterized using a simultaneous thermal analyzer, capillary rheometer, electronic universal material testing machine, and scanning electron microscope (SEM); their crystallization, rheological behavior, mechanical properties, surface structure, etc., were studied. DSC results indicate that an increase in carbon fiber content enhances the thermal stability of CF/PA6 and narrows the crystallization window but has a minor effect on the molecular chain diffusion time. The crystallinity reaches its maximum at a carbon fiber content of 40 wt.%, reaching 55.16%. The steady-state rheological behavior reveals that CF/PA6 behaves as a pseudoplastic fluid, exhibiting shear-thinning behavior. When the carbon fiber content is 40 wt.%, the power law exponent (n) reaches its maximum, and the consistency coefficient (K) decreases by 300 Pa⋅sn compared to the 30 wt.% content. With increasing temperature, n increases while K decreases. SEM observations reveal that samples with carbon fiber contents of 20 wt.% and 40 wt.% exhibit better fiber dispersion and orientation. However, the interfacial bonding strength is superior in the 40 wt.% sample. When the carbon fiber content reaches 50 wt.%, significant injection molding defects occur at the clamping end, leading to extensive matrix tearing during tension testing.

High-strength, impact-resistant PP/PTFE composite foam with enhanced surface appearance achieved through mold-opening microcellular injection molding

Poor surface appearance and decreased mechanical performance are critical factors limiting the broad application of Microcellular injection molding (MIM) in foamed polymer products. Herein, in-situ polytetrafluoroethylene (PTFE) nanofibrils reinforced polypropylene (PP) foams with high strength, impact resistance, and enhanced surface quality were prepared by mold opening microcellular injection molding (MOMIM). PTFE nanofibers with different diameters were introduced into the PP matrix via twin screw extrusion and significantly enhanced the crystallinity and viscoelasticity of the PP matrix with the enhancement being more pronounced for the finer PTFE fibers. High-density oriented cellular structures were formed in the MOMIM PP/PTFE foams owing to the heterogeneous nucleation of PTFE and the stretching effect of the mold opening process. The optimum MOMIM PP/PTFE foam fabricated possesses a high cell orientation angle close to 90° and a large cell aspect ratio of 5.3, which reached a 34.37 % increase in tensile strength and a 73.08 % increase in impact strength owing to the synergetic effects of the PTFE network and the highly oriented fine cell structure, which effectively dissipated the tensile stress and impact stress by cell wall twisting and folding deformation. Furthermore, the MOMIM PP/PTFE foam showed a significantly enhanced surface quality compared to the MIM foam due to the reduced dragging flow in MOMIM, which greatly hindered cell rupture on the foam surface. Therefore, this work provides insights into the MOMIM of polymer composites containing fibrous fillers and the enhancement of tensile properties, impact resistance, and surface quality of foam products.

Innovative use of fluorescent grafting for damage and morphological monitoring during the extrusion process of PCL-flax fibre-reinforced composites

Limiting plant fibre damage during industrial processing is challenging for biobased composite development due to plant cell wall sensitivity to temperature and shear. This study developed an innovative fluorophore grafting method to indirectly monitor flax fibre morphological damage during twin-screw extrusion in a poly-(caprolactone) matrix. Results showed the fluorophore was strongly degraded after severe process conditions, with −87.1 % and −72.2 % changes in fluorescence intensity at 240 °C and 300 rotations per minute, respectively, compared to native fluorescence. The fluorescence intensity correlated well with the fibre aspect ratio and length, making it a reliable indicator of the fibre’s morphology degradation.

Analisis Gugus Fungsi dan Sifat Termal Limbah Jaring Ikan Untuk Produk Otomotif

Plastic has been used in daily life due to its durability. Fishing net waste is a type of plastic waste that is dangerous. Fishing net waste can also damage marine biota, such as coral reefs and marine animals. One type of polyamide that is widely used is nylon. Fishing net waste containing nylon has the potential to be recycled. In this research, fishing net waste is used for automotive product applications using a twin-screw extruder. There are five variations: pure polyamide (PA), recycled polyamide (rPA), PA-rPA 50:50, PA-rPA 75:25, and PA-rPA 25:75. To be able to determine the characteristics of the mixed product, several tests were carried out, including testing the thermal properties of the final product with DSC and FTIR testing to identify functional groups. Based on the research results, it was found that all variations contained polyamide polymers, which were characterized by a melting temperature of 218.8–224.4 °C and obtained carbonyl functional groups (C=O) and secondary amine functional groups (N–H) in the FTIR test results, which indicated the presence of amide bonds in the samples.

Use of commercial synthetic filament waste to reinforce biobased poly(butylene succinate) with the aid of compatibilizers

Since poly(butylene succinate) (PBS) has low rigidity for engineering application, this research attempted to reinforce PBS with poly(ethylene terephthalate) (PET) and polyamide-6 (nylon6) filaments with the reservation of polymer toughness. Filaments were chopped to be short fibers (length of 2 mm to 4 mm) and melt compounded with PBS pellets in the weight ratio of 1 wt%, 5 wt%, and 7 wt% using a twin-screw extruder that the temperature profile was set high enough for melting only PBS matrix. Two types of compatibilizers; hexamethylene diisocyanate (HMDI) or hexamethylene diamine (HMDA) of 0.05 wt% were used to treat fiber surface. It was found that tensile modulus of PBS increased with respect to fiber concentration, which untreated PET fibers provided higher tensile modulus about 2% to 7%. Surface treatment of fibers with either HMDI or HMDA increased rigidity of the composites, while elongation at break and impact strength were also improved with respect to fiber concentration. Also, shifting in glass transition temperature of PBS by DMA indicated improved interfacial interaction, which HMDA treatment gave the best benefit for mechanical properties. Number-average molecular weight of HMDI-treated composites was closed to extruded PBS, however, those of HMDA-treated composites were reduced dramatically implying chain scission highly occurred. SEM micrographs revealed good interfacial adhesion obtained after fiber treatment. Crystallization of PBS studied by XRD showed that the crystal form was not affected by the compatibilizer.

A comprehensive review on residence time distributions in co-rotating twin-screw extrusion

Abstract The concept of residence time distribution (RTD) is crucial in many chemical engineering applications. In the case of co-rotating twin-screw extrusion, it is an important process parameter, particularly when dealing with reactive systems, degradation issues, or scale-up problems. In this review paper, after introducing the basic notions concerning RTD, the various measurement methods are detailed. Then, experimental results on the influence of the main parameters of the extrusion process (screw speed, feed rate, barrel temperature, screw profile, etc.) are presented. Finally, the various theoretical approaches to describe and/or predict RTD are reviewed.

Mechano-chemical, high-consistency activation of kraft pulp in deep eutectic solvent of choline chloride and urea

Deep eutectic solvents (DESs) offer an appealing green medium for the activation of cellulose fibres to promote their swelling, reactivity, hydrolysis, disintegration, and solubility for further processing. Typically, DES treatments are carried out below 5 wt% consistency even though a higher solids content could enhance the fibre activation and reduce the solvent consumption. In this work, a high-consistency (HC) mechano-chemical activation of bleached softwood kraft pulp was elucidated using a simultaneous fibre treatment with DES of choline chloride-urea and a sigma-type kneader or a twin-screw extruder at a solids content of 15–35 wt% and 30 wt%, respectively. Both HC treatments efficiently triggered fibre swelling, which was indicated by an increase in the fibre width, and loosened the cell wall structure which was indicated by an increase in the mesopore volume. Mechano-chemical HC processing generated fibre fines and external fibrillation, while the molecular-level structural alteration or changes in chemical composition were minor; the intrinsic viscosity and the crystallinity of the pulp remained at their initial level and only a small amount of xylan was dissolved. Overall, HC treatment in a twin-screw extruder caused notably more severe morphological changes in the fibres than batch treatment in a sigma-type kneader. Thus, the mechano-chemical HC treatment with DES provides an industrially relevant technology for cellulose modification and opens possibilities to enhance heterogeneous cellulose modification processes in which the highly available surface area of pulp is a key parameter.

Multi-walled carbon nanotube-enhanced polyurethane composite materials and the application in high-performance 3D printed flexible strain sensors

Flexile strain sensors hold vast potential for applications in monitoring human motion, enabling human-machine interaction, and facilitating information transfer, etc. However, the available materials and manufacturing techniques for fabricating flexible strain sensors with high sensitivity and extended sensing range still face significant challenges. By utilizing solution casting and twin-screw extrusion techniques, this study prepared high-performance thermoplastic polyurethane/multi-walled carbon nanotube (TPU/MWCNT) nanocomposite 3D printable filaments, and employed material extrusion 3D printing technology to facilely fabricate flexible strain sensors. The 1-pyrene carboxylic acid (PCA)-modified TPU/MWCNT(3 wt%) nanocomposite exhibited outstanding mechanical properties, with a tensile strength of 24.3 ± 0.5 MPa and a fracture elongation of 625.8 ± 12.3 %. The 3D printed TPU/MWCNT(3 wt%)/PCA flexible strain sensors demonstrated amazing sensitivity (GFmax = 10279.95) within a wide strain range (0–300 % strain). The addition of PCA brings the benefits of improved dispersion of MWCNTs in the TPU composite, as well as enhanced thermal stability, and upgraded mechanical and electrical properties under different tensile strains. Meanwhile, the 3D printed samples displayed remarkable durability and reproducibility. Finally, the flexible strain sensors fabricated from this nanocomposite material could accurately perceive human motion, providing great prospects for wearable device applications.

The Effect of Zn2(BDC)2 Metal Organic Framework on the Miscibility and Properties of Poly(Lactic Acid)/Poly(Butylene Adipate-co-Terephthalate) Biodegradable Blends

In our research described in this paper, the metal-organic framework MOF-2 [Zn2(BDC)2] was used to enhance the properties of a biodegradable blend based on poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). PLA/PBAT/(1, 3, 5, and 7 wt%) MOF-2 blends were prepared using a melt blending technology with a twin-screw extruder. The phase morphology, rheological behavior and barrier properties of the blends were studied. X-ray diffraction (XRD) showed a slight increase in the crystalline content of the PLA/PBAT matrix with increasing MOF-2 content. Scanning electron microscopy (SEM) revealed that the PLA/PBAT blend was immiscible, and the phase morphology improved with MOF-2 by enhancing the interfacial compatibility, reducing the size of micro-domains and cavities, and promoting a transition to a co-continuous morphology, indicating better miscibility. The ternary nanocomposites with 5 and 7 wt% MOF-2 showed increased complex viscosity (η*) and storage modulus (G′) compared to those with 1 and 3% MOF-2, indicating stronger percolated networks. The thermal and barrier properties and water absorption capacity were also improved, confirming the rheological measurements. All the results showed that the PLA/PBAT/MOF-2 nanocomposites could be used in the field of packaging.

Evaluation of the effects of extrusion parameters on the swelling of extruded filament in an innovative 3D printer containing a vertical co-rotating twin-screw extrusion unit

Evaluation of the effects of extrusion parameters on the swelling of extruded filament in an innovative 3D printer containing a vertical co-rotating twin-screw extrusion unit

Identifying the location and micellization of PEG-b-PCL multiblock copolymers in PLA/PCL blends via AFM nanoscale IR spectroscopy

The IR absorption mapping of two multiblock copolymers based on poly(ethylene glycol) and poly(ε-caprolactone) segments (PEG-b-PCL) in poly(acid lactic) and poly(ε-caprolactone) blends (PLA/PCL) was performed via AFM nanoscale IR spectroscopy. These copolymers, having the same number average molar masses (Mn‾) but varying block sizes, were added into the blend in different amounts (1 and 5 wt%) using a co-rotating twin-screw extrusion. The results revealed that copolymers with smaller blocks are preferentially located near the interface when incorporated in small quantities. Increasing the copolymer content led to preferential diffusion into the PLA matrix. Compatibilization with the longer block-size copolymers also led to preferential diffusion in the PLA matrix, albeit with a tendency to form micelles. This hampers the overall mechanical properties of the blend, making the compatibilized blend more brittle than neat PLA. Compatibilization with the short block-size copolymers showed no micellization and improved the mechanical behavior of PLA/PCL.

Twin-screw extrusion optimization and study of morphological, thermal, mechanical and fracture properties of sustainable Poly(lactic acid) (PLA) and Poly(butylene sebacate) (PBSe) blends

The pursuit of sustainability in material science forces the utilization of bio-based and/or biodegradable alternatives to fossil-based plastics. With growing attention in recent years, particularly in applications like packaging and agriculture, biodegradable and bio-based polymers offer potential solutions to mitigate environmental concerns associated with plastic disposal. In this context, Poly(butylene sebacate) (PBSe), a commercially available biobased and biodegradable aliphatic polyester derived from sebacic acid and 1,4-butandiol, presents a promising innovation due to its flexibility, availability in the market and compatibility with poly(lactic acid) (PLA). Up to day few works investigated the addition of PBSe to PLA, for this reason the present work focuses on comprehensively characterizing PLA/PBSe blends (with different PBSe amounts from 10 up to 40 wt%). The blends have been produced through extrusion compounding after a careful Design of Experiment for optimizing process parameters to efficiently improve mixing and energy consumption. Thermal, mechanical, and morphological properties were evaluated, combined with micromechanical analysis employing dilatometric tests. Additionally, an elasto-plastic fracture mechanics protocol was applied to quantify toughness and energy absorption capabilities, demonstrating the potential of PLA/PBSe blends in sustainable material applications. In this work also emerged the great capacity of PBSe in acting as toughener for PLA especially when is present in low amount.

Enhancing nutritional and functional properties of gluten-free Riceberry rice pasta supplemented with cricket powder using D-optimal mixture design

The study aimed to develop gluten-free Riceberry rice pasta supplemented with cricket powder using a twin-screw extruder, contributing valuable knowledge to increasing the nutritional value of pasta through sustainable practices, nutritional enhancement, and novel ingredients. The D-optimal mixture design, an effective statistical tool for optimizing formulation, was used to determine the optimal proportions of Riceberry rice flour (RF, 75–90%), cricket powder (CP, 5–20%), and xanthan gum (XG, 1–5%). The results showed that all predictive models were statistically significant with satisfactory coefficients of determination (R2 ≥ 0.75), and exhibited a non-significant lack of fit. The contour plot demonstrated that pasta with high RF, XG, and low CP contents had the lowest L* and highest a* values. The incorporation of XG increased firmness, while an increase in CP led to higher protein and fat contents in the pasta. A decrease in RF resulted in reduced total phenolic content (TPC), anthocyanin content (ATC), and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activity (AOA). The sensory evaluation scores of the pasta, in terms of the texture attribute and overall acceptance, decreased as the proportion of XG increased. The optimization analysis showed that the highest desirability was achieved with RF, CP, and XG at 84.10, 14.45, and 1.45%, respectively. The optimally desirable product had the following properties: L* at 22.60, a* at 4.80, b* at 4.78, firmness at 3.41 N, protein content at 12.57%, fat content at 4.68%, TPC at 360.13 mg GAE/100 g dw, ATC at 476.24 mg C3G/100 g dw, AOA at 25.10 mg TE/100 g dw, texture rating at 7.40, and overall acceptance rating at 7.01. This study highlights the potential of cricket powder as a protein source in gluten-free Riceberry rice pasta. It offers insights into the effects of ingredients on pasta quality and facilitates the development of nutritious and appealing gluten-free pasta.