Twin-screw Extruder Research Articles

Post-consumer high-density polyethylene matrix reinforced by sugarcane bagasse fibers treated in stearic acid solution

The study aimed to advance composite technology by exploring the potential of recycled materials, specifically high-density polyethylene (HDPE) composites reinforced with sugarcane bagasse fibers. This research not only addresses environmental concerns by utilizing recyclable materials but also aims to offer significant technical, economic, and social advantages. The investigation focused on formulating and evaluating these composites, considering varying proportions of untreated sugarcane bagasse fibers and examining the effects of chemical treatment with stearic acid at different temperatures. Using a conical twin-screw extruder and injector, the researchers produced and analyzed the composites both morphologically and mechanically. The principal findings indicated that the inclusion of untreated fibers improved the stiffness and tensile strength of the composites. Nevertheless, adhesion between the fibers and the matrix was compromised, especially with higher fiber concentrations. Chemical treatment at 40 °C significantly improved fiber/matrix interactions, thereby enhancing the reliability and mechanical properties of the composites. This treatment led to substantial increases in tensile and compressive strengths, particularly noticeable in composites containing 10%–15% fiber by weight. These results not only demonstrate the feasibility of using recycled HDPE and sugarcane bagasse fibers in composite materials but also suggest avenues for further exploration. Future research could delve deeper into optimizing chemical treatment processes to achieve even better adhesion and mechanical performance. Moreover, exploring broader applications in industries such as automotive, aerospace, naval, civil engineering, and packaging could unlock new opportunities for these sustainable composites. This study thus paves the way for advancing composite technology towards more environmentally friendly and economically viable solutions.

Chitin Nanocomposites for Fused Filament Fabrication: Flexible Materials with Enhanced Interlayer Adhesion.

In this work, we present a series of nanocomposites for Fused filament fabrication (FFF) based on polycaprolactone (PCL) and chitin nanocrystals (ChNCs). The ChNCs were synthesized by acid hydrolysis using HCl or lactic acid (LA). The approach using LA, an organic acid, makes the ChNCs synthesis more sustainable and modifies their surface with lactate groups, increasing their compatibility with the PCL matrix. The ChNCs characterization by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that both ChNCs presented similar morphologies and crystallinity, while differential scanning calorimetry and thermogravimetric analysis proved that they can bear temperatures up to 210 °C without degrading, which allows their processing in the manufacturing of PCL composites by twin-screw extrusion. Therefore, PCL composites in the form of filaments containing 0.5-1.0 wt % ChNCs were produced and used as feedstock in FFF, and standard tensile and flexural specimens were printed at different temperatures, up to 170 °C, to assess the influence of the ChNCs in the mechanical properties of the material. The tensile testing results showed that the presence of ChNCs enhances the strength and ductility of the PCL matrix, increasing the elongation at break around 20-50%. Moreover, the vertically printed flexural specimens showed a very different bending behavior, such that the pure PCL specimens presented a brittle fracture at 7% strain, while the ChNCs composites were able to bend over themselves. Hence, this work proves that the presence of ChNCs aims to improve the interlayer adhesion of the objects manufactured by FFF due to their good adhesive properties, which is currently a concern for the scientific community and the industrial sector.

Aqueous Pretreatment of Lignocellulosic Biomass for Binderless Material Production: Influence of Twin-Screw Extrusion Configuration and Liquid-to-Solid Ratio.

This study was carried out to investigate the continuous aqueous pretreatment of sugarcane bagasse (SCB) through twin-screw extrusion for a new integrated full valorization, where the solid residue (extrudate) was used for the production of bio-based materials by thermocompression and the filtrate for the production of high-value-added molecules. Two configurations, with and without a filtration module, were tested and the influence of the SCB composition and structure on the properties of the materials were determined. The impact of the liquid-to-solid (L/S) ratio was studied (0.65-6.00) in relation to the material properties and the biomolecule extraction yield in the filtrate (with the filtration configuration). An L/S ratio of at least 1.25 was required to obtain a liquid filtrate, and increasing the L/S ratio to 2 increased the extraction yield to 11.5 g/kg of the inlet SCB. The extrudate obtained without filtration yielded materials with properties equivalent to those obtained with filtration for L/S ratios of at least 1.25. Since the molecule extraction process was limited, a configuration without filtration would make it possible to reduce water consumption in the process while obtaining high material properties. Under the filtration configuration, an L/S ratio of 2 was the best tradeoff between water consumption, extraction yield, and the material properties, which included 1485 kg/m3 density, 6.2 GPa flexural modulus, 51.2 MPa flexural strength, and a water absorption (WA) and thickness swelling (TS) of 37% and 44%, respectively, after 24 h of water immersion. The aqueous pretreatment by twin-screw extrusion allowed for the overall valorization of SCB, resulting in materials with significantly improved properties compared to those obtained with raw SCB due to fiber deconstruction.

Photocatalytic films with high ethylene degradation efficiency for strawberry preservation

The preservation of fruits has always been a research hotspot. In this research, titanium dioxide(TiO2) exhibiting diffraction peaks characteristic of both anatase and rutile phases was synthesized. Subsequently, photocatalytic films loaded with the TiO2 were fabricated using a twin-screw extruder combined with an extrusion casting technique. The films demonstrated a highest ethylene photocatalytic degradation efficiency of 88.57 %. The addition of TiO2 significantly enhanced the hydrophilicity of the films, with a maximum increase of 8.08 %. The tensile strength and elongation at break of the films were also improved. The optical properties, barrier properties and mechanical properties revealed that the film may make contributions to slowing down light aging, reducing weight loss of strawberries and increasing the load-bearing property. Furthermore, fresh-keeping experiment proved that the photocatalytic films could markedly slow down the appearance change, reduce weight loss and TBARS accumulation while decelerating the decline of TSS and antioxidant capacity in strawberries.

Heterodox Torrefaction of the Forest Residue with a Twin-Screw Extrusion Reactor

Heterodox Torrefaction of the Forest Residue with a Twin-Screw Extrusion Reactor

Fabrication of biopolyethylene-based biocomposites with coffee ground waste: Effect of polyethylene-graft-maleic anhydride

The production of plastic products from non-renewable raw materials, such as petroleum, damages the environment. Consequently, biocomposites have aroused interest from industry and researchers due to their ecologically correct characteristics, mainly because they come from renewable sources. Therefore, this study aimed to produce biopolyethylene/coffee ground waste (BioPE/CGW) biocomposites and analyze the impact of CGW and polyethylene-graft-maleic anhydride (PE-g-MA) on BioPE. The biocomposites were prepared in a co-rotational twin-screw extruder equipped with a side feeder to feed the CGW. The materials were subsequently injection molded to produce the impact, tensile, and HDT samples. The temperature profiles used during extrusion and injection were between 170 and 180°C. The BioPE and biocomposites were investigated for the vibrational (Infrared Spectroscopy - FTIR), thermal (differential scanning calorimetry), mechanical (tensile, impact, and hardness), thermomechanical (heat deflection temperature (HDT) and Vicat softening temperature (VST)), and morphological (scanning electron microscopy (SEM)) properties. The compatibilizer improved the interface between phases, promoting mechanical and thermomechanical improvements in the biocomposites. PE-g-MA promoted increments in tensile strength and elastic modulus of up to 38% and 25% in the BioPE/CGW30 and an increase of 44% in the elastic modulus compared to BioPE. The thermomechanical investigations showed that HDT increased by 8.8 and 3.3°C and VST increased by 2.5 and 6.6°C compared to BioPE and the BioPE/CGW30, respectively. Biocomposites from renewable and biodegradable sources align with a sustainable development concept.

Compounding and Dispersion Technology for Nanocomposites and Polymer Blends by Using Extensional Flow in Twin-Screw Extruder

Compounding and Dispersion Technology for Nanocomposites and Polymer Blends by Using Extensional Flow in Twin-Screw Extruder

Flow Analysis and Shear Rate Comparison of Counter-rotating and Co-rotating Intermeshing Twin-screw Extruders for Filament Extrusion of Polypropylene-based Biocomposites

This study investigates and compares the performance of counter-rotating and co-rotating intermeshing twin-screw designs in filament extruder machines. The research sought to determine whether the counter-rotating intermeshing design with its opposite flow direction offers advantages over the co-rotating intermeshing design in terms of flow analysis and shear rates. Flow analysis was conducted to examine the velocity of the polypropylene-based biocomposite material inside the barrel. Shear rate data was obtained by evaluating the relationship between shear rate and screw speed to assess the stability and maximum shear rate of the twin-screw extruders. The results revealed that the counter-rotating intermeshing twin-screw extruders exhibited higher shear rates and more consistent pressure compared to the co-rotating intermeshing design. The superiority of the counter-rotating extruder was attributed to its opposite flow direction and distinct thread shapes, facilitating efficient material compression and improved dispersion of polymer-based biocomposite materials. The study suggested the potential for further exploration and refinement of the counter-rotating intermeshing twin-screw extruder design, particularly in producing polypropylene-based biocomposite filaments for Fused Deposition Modeling (FDM) machines.

Environmental Assessment on Fabrication of Bio-composite Filament Fused Deposition Modeling Through Life Cycle Analysis

The environmental effect of a manufacturing or service method is determined by the resource and energy inputs and outputs at each point of the product’s life cycle. In Fused Deposition Modeling (FDM), generally, the material used for fabrication is plastic, and the raising of interest from different backgrounds of users could increase the issue of plastic pollution. Therefore, many scholars have proposed an initiative to employ bio-composite in FDM. In this study, an environmental assessment of global warming potential and fine particulate matter emission from the fabrication of bio-composite filament FDM was performed through its life cycle analysis using GaBi Software. Initially, data on resources and energy inputs and outputs were gathered. The functional unit in this study was the 1.0 kg wood/PLA composite filament extruded using a twin-screw extruder. All wastes were collected and recycled. The fabricated composite filaments were transported by container ship with a capacity of 5000 – 200 000 dwt gross weight for 100 km within Malaysia. Based on the results from the GaBi dashboard, the FDM process of bio-composite filament has contributed as much as 138.7 kg CO2 eq on the global warming potential and 1.71e-4 kg N eq. on fine particulate matter by the electricity power generation in extrusion and printing processes. The main factor for this issue is the consumption of coal in electric power generation, which is considered a non-renewable resource. Therefore, it is recommended that natural fibers such as wood fiber be employed in the filament of FDM to reduce the environmental impact. As shown in the study, the materials contribute less to the impact. Further study is suggested to compare the FDM technology with conventional technology using similar materials.

Tuning the Structure-Property Relationships in Binary and Ternary Blends of PLA/PBAT/PHBH.

While the brittle polylactide (PLA) has a high durability among bioplastics, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with certain ductility exhibits facile compostability. The addition of polybutylene adipate terephthalate (PBAT) may also be used to improve the ductility and toughness of brittle bioplastics. Binary and ternary blends of PLA/PBAT/PHBH based on either PLA or PHBH as the matrix have been manufactured using a twin-screw extruder. The melt rheological, mechanical, and morphological properties of the processed samples were examined. Binary blends of PLA/PHBH show superior strength, with the PLA75/PHBH25 blend exhibiting a tensile strength of 35.2 ± 3.0 MPa, which may be attributed to miscible-like morphology. In contrast, blends of PLA with PBAT demonstrate low strength, with the PLA50/PBAT50 blend exhibits a tensile strength of 9.5 ± 2.0 MPa due to the presence of large droplets in the matrix. PBAT-containing blends exhibit lower impact strengths compared to PHBH-containing blends. For instance, a PLA75/PBAT25 blend displays an impact strength of 1.76 ± 0.1 kJ/m2, whereas the PHBH75/PBAT25 blend displays an impact strength of 2.61 ± 0.3 kJ/m2, which may be attributed to uniformly dispersed PBAT droplets.

Extrusion foaming of Poly(lactic acid)/Rice straw composites: Opposing effects of eco-friendly physical/chemical treatment and compatibilization methods

In this study, the effects of two environmentally-friendly pulping methods along with two different reactive compatibilization methods on the foamability of poly (lactic acid) (PLA)/rice straw (RS) biocomposites have been investigated. RS as an annually renewable agricultural waste is low-cost and available. Melt-compounding and melt-foaming processes were performed through a twin-screw extrusion processing. The correlations between processing and microstructure were studied. The findings show that the RS pulping with sodium bicarbonate (SB) solution leads to the lignocellulosic particles with a porous structure. The structure causes the filler/matrix mechanical engagement and improves the interfacial adhesion and rheological properties, hence forming smaller cells with the narrowest cell size distribution. In contrast, applying ultrasound waves on the RS pulp brings the particles to very smooth surfaces. These surfaces have the highest activity at the cell nucleation stage and considerably increase the foam’s cell density. The reactive compatibilizers based on epoxy and maleic anhydride groups show opposing effects on the biocomposite microstructure, depending on the RS pulp type. The use of the reactive compatibilizers in the PLA/RS pulp treated with SB led to lighter foams with larger cells and higher cell densities and void fractions. Whereas the incorporation of the compatibilizers into the biocomposites containing RS pulp treated with SB and ultrasonic waves resulted in noticeably lower cell density and larger foam density. The extruded biocomposite foams with closed-cell microstructure can be used in insulation and packaging applications.

The effect of mixing sequence on synthesis of PP-g-GMA compatibilizer for multilayer packaging (MLP) compounding

Melt recycling Multilayer Packaging (MLP) waste is difficult due to challenging separation procedures. However, blending techniques with compatibilizers can simplify MLP waste melt recycling. PP-g-GMA is a common compatibilizer in polyolefin and PET blends. PP-g-GMA compatibilizer was synthesized by utilizing an internal mixer at 175℃, 50 rpm, and 10 min using styrene as a comonomer. Titration was a method to examine effect of three different sequences of adding the BPO initiator on GMA grafting. Each sequence's PP-g-GMA samples were compounded with MLP waste using a twin-screw extruder and injection molded to make tensile test specimens. FTIR analysis shows that the GMA and Styrene monomers had grafted onto the PP polymer backbone, with the GMA grafting degree by varying mixing sequence. Sequence 3, which introduced initiator, GMA, and styrene simultaneously to PP melt, yielded PP-g-GMA with the most significant GMA grafting degree of 5.11%. Adding PP-g-GMA produced from sequence 3 into the MLP melt enhanced the highest increase in tensile strength and elongation at break of the MLP/PP-g-GMA compound.

Mixing performance in an asymmetrical non-twin kneading element channel

Abstract The kneading elements play a crucial role in the distributive and dispersive mixing in the conventional co-rotating twin screw extruders. A novel kind of asymmetrical dual-speed co-rotating non-twin kneading elements (NTKE) with a zero staggered angle was designed to introduce symmetry break to improve mixing. Finite element method was applied to solve the time-dependent flow field where mesh superposition technique was used to impose the boundary conditions of moving parts and further to avoid the remeshing at every time steps. The flow and mixing of several fluids obeying the Carreau constitutive model with the different power law exponents were investigated numerically and compared with the conventional co-rotating twin kneading elements (TKE). Distributive mixing was evaluated through evolution of tracer droplets and decaying of variance index with time. Moreover, the dispersive mixing was examined in terms of the statistical distributions of mixing index. An integral function with regard to the mixing index was proposed to evaluate the proportion of tracer particles subjected to the elongation.

Characteristics Of Partially Pregelatinized Sago Starch Extruded Under Various Conditions Using A Twin Screw Extruder Without A Die

Abstract This study aims to obtain the characteristics of PPSS as a binder extruded in a twin-screw extruder (TSE) without a die under 9 extrusion conditions selected from a systematic review. The Successive conditions: moisture content, last zone of barrel temperature, and screw speed for each condition were recorded. Respectively, the values were 32%, 60⁰C, 100 rpm for PPSS 1; 22%; 120⁰C; 250 rpm for PPSS 2; 22%, 100⁰C, 250 rpm for PPSS 3; 16%, 135⁰C, 150 rpm for PPSS 4; 10%, 160⁰C, 200 rpm for PPSS 5; 28.8%;, 100⁰C, 220 rpm for PPSS 6; 30%, 80⁰C, 200 rpm for PPSS 7; 25.2%, 97.5⁰C, 250 rpm for PPSS 8, and 30%; 135⁰C; 160 rpm for PPSS 9. The study informed that the degree of gelatinization (DG), water solubility index (WSI), water absorption index (WAI), and swelling power (SP) of PPSS 6 were the highest among the others but its bulk density (BD), degree of whiteness (DW), maximum viscosity (MV), and enthalpy were the lowest. Scanning electron microscopy showed that PPSS granules were irregular compared to their natural oval shape. Starch granule crystallinity indicated that some crystallines became amorphous and some increased (PPSS 3 and 4) while birefringence properties almost disappeared entirely.

Effects of extrusion conditions on the morphological, functional, and sensory properties of soy press cake extrudates

Abstract: We developed and applied 4 extrusion regimens (moisture content between 30 % and 60 % and temperature from 110 °C to 120 °C) with twin-screw extruder for valorising soy press cakes, byproduct of soy drink (Soyd) and tofu (Soyt) manufacturing processes, by varying physical conditions of extrusion for improving their morphological, functional, and sensory parameters. The valorised soy press cakes were compared to their respective control samples (Soyd or Soyt) both before and after extrusion. Two quantities (3%–6%) of untreated and extruded soy press cakes were utilised to develop meat analogues. Extrusion introduced striations and reduced flakiness on the surface of extruded press cake samples. Press cakes extruded at higher moisture indicated improved water holding and oil holding capacity. Interestingly, the same press cake samples also scored higher for positive indicators (e.g., juiciness) during sensory assessment. Compared with meat analogue control matrix, all meat analogue samples containing varying amounts of extruded press cake exhibited reduced chewiness, with other parameters relatively unchanged. Our results indicate that extrusion of soy press cakes of both Soyd and Soyt origin at 120 °C with 60 % moisture results in improving the morphological, functional, and sensory properties of press cakes, making them suitable for development of meat analogues.

Upscaling cellulose oxidation: Integrating TEMPO-mediated oxidation in a pilot-plant twin-screw extruder for cellulose nanofibril production

(TEMPO)-mediated oxidation (TMO) is a widely recognized pretreatment for producing highly fibrillated cellulose nanofibrils (CNFs) because of its efficiency and selectivity. However, the challenges of scaling up this process is limiting its implementation. This study explores enhancing the production of oxidized pulps (OPs) by performing the TMO reaction within a pilot-plant twin-screw extruder (TSE). This approach aims to oxidize large volumes of cellulose at high concentrations while simultaneously applying a soft mechanical fibrillation, making the upscaling process more sustainable and feasible. OPs and CNFs were characterized and compared to those obtained from the traditional TMO pretreatment in a stirred reactor as well as those pretreated by mechanical TSE. Results demonstrate that TMO within the TSE is more efficient and increase the yield fibrillation using 0.8, 0.08 and 2 mmol/g pulp of NaBr, TEMPO and NaClO, respectively. Multiple TSE steps decrease polymerization degree, enhance the process yield, and reduce the number of large fibers. Gradual addition of oxidants in multiple TSE steps prevents harsh reaction conditions and avoids yellowing of the final products.

The Effect of Sodium Tripolyphosphate and Guar Gum on Physical Characteristics of Analog Rice from Gaplek Flour

Gaplek flour is a processed product of cassava preservation abundant during the harvest season in Lampung Province. The high carbohydrate content in cassava facilitates the processing of gaplek flour into carbohydraterich food source, such as analog rice. Therefore, this study aimed to investigate the effect of adding STPP and guar gum on the formulation of analog rice made from 70% gaplek flour and 30% corn flour. Analog rice was produced using the extrusion method with a twin-screw extruder. The results showed that the addition of STPP did not affect water absorption characteristics. The solubility of rice in deep water also decreased with increasing amounts of STPP and guar gum. Meanwhile, guar gum significantly increased water absorption and reduced the solubility of rice in water. The degree of gelatinization decreased with the addition of both materials. The addition of 0.3-0.5% STPP and 0.5-2% guar gum had no significant effect on hardness, stickiness, elasticity, and cohesiveness of analog rice prepared using a cooker.

Self-Formation of Lignin Particles Through Melt-Extrusion for Active Biodegradable Food Packaging.

This study presents a method for the self-formation of lignin particles within a polylactic acid (PLA) matrix during melt-extrusion, eliminating the need for separation and drying steps typically associated with submicro-size lignin particles. This method effectively mitigates the problem of agglomeration often associated with the drying step. Softwood kraft lignin, guaiacyl lignin (GL-lignin), was dissolved in low-molecular-weight poly(ethylene glycol) (PEG) and was introduced into a twin-screw extruder using a liquid feeder. Lignin particles within a particle size range of 200-500 nm were observed in the extrudate of the PLA/PEG/GL-lignin composites. PLA/PEG/GL-lignin composite films were produced through blown film extrusion. These composite films demonstrated superior ultraviolet (UV)-barrier and antioxidant properties compared to neat PLA films, with optical and mechanical characteristics comparable to those of neat PLA. Moreover, migration values of the composite films in various food simulants were below regulatory limits, suggesting their potential for food packaging applications. This self-formation process offers a promising approach for utilizing lignin for PLA applications.

Optimization of an Industrial Recycling Line: The Effect of Processing Parameters on Mechanical Properties of Recycled Polyethylene (PE) Blends

This study concerns the optimization of an industrial recycling line; in other terms, this paper aims to find the optimal processing parameters that allow for a decrease in the loss of stress crack resistance (SCR) using a notched crack ligament stress (NCLS) test and an increase in the gain of the elongation at break, flexural modulus, and Izod impact strength of a polyethylene (PE) blend before and after recycling. The recycling line is composed mainly of a mono- and twin-screw extruder and a filtration system. Hence, the research question is as follows: How can we optimize the recycling process, without compromising the mechanical properties of recycled polyethylene (PE) blends? To answer the research question, Taguchi’s design of experiment and grey relational analysis (GRA) for multiobjective optimization was applied. Experiments were performed according to L16 standard orthogonal array based on five process parameters: mono-screw design, screw speed of the mono- and twin-screw extruder, melt pump pressure, and filter mesh size. Based on grey relational analysis (GRA), the optimal setting of process parameters was identified, and a barrier screw and a higher screw speed for both extruders were allowed to have optimal mechanical properties. Furthermore, the analysis of variance (ANOVA) indicated that the mono-screw design and screw speed of the mono- and twin-screw extruder significantly impact the mechanical properties of recycled polyethylene (PE) blends.

Influence of Screw Design and Process Parameters on the Product Quality of PEO:LiTFSI Solid Electrolytes Using Solvent-Free Melt Extrusion

All-solid-state battery (ASSB) technology is a new energy system that reduces the safety concerns and improves the battery performance of conventional lithium-ion batteries (LIB). The increasing demand for such new energy systems makes the transition from laboratory scale production of ASSB components to larger scale essential. Therefore, this study investigates the dry extrusion of poly(ethylene oxide):lithium bis (trifluoromethylsulfonyl)imide (PEO:LiTFSI) all-solid-state electrolytes at a ratio of 20:1 (EO:Li). We investigated the influence of different extruder setups on the product quality. For this purpose, different screw designs consisting of conveying, kneading and mixing elements are evaluated. To do so, a completely dry and solvent-free production of PEO:LiTFSI electrolytes using a co-rotating, intermeshing, twin-screw extruder under an inert condition was successfully carried out. The experiments showed that the screw design consisting of kneading elements gives the best results in terms of process stability and homogeneous mixing of the electrolyte components. Electrochemical impedance spectroscopy was used to determine the lithium-ion conductivity. All electrolytes produced had an ionic conductivity (σionic) of (1.1–1.8) × 10−4 S cm−1 at 80 °C.