Melt Extrusion Method Research Articles

A novel melt extrusion method for efficient and large-scale in-situ exfoliation of boron nitride to prepare high performance thermal conductive polymer composite

The polymer/hexagonal boron nitride (h-BN) thermal conductive composite an excellent candidate for thermal management materials due to its insulation properties. However, it is a challenge to achieve efficient large-scale exfoliation of h-BN through melt blending to balance thermal conductivity and mechanical properties. In this work, an innovative melt mixing strategy using the co-rotating non-twin screw extruder (NTSE) was developed to prepare the high-density polyethylene (HDPE)/h-BN composites with excellent overall performance. The results were well compared with those of conventional twin screw extruder (TSE). The NTSE triggers chaotic mixing and provides a strong elongation flow field capable of h-BN efficiently exfoliating into a few layers, while simultaneously ensuring uniform dispersion and distribution within HDPE. The in-plane thermal conductivity and elongation at break of the NTSE composite with 10 wt% h-BN addition were 7.63 W∙m−1 K−1 and 653.1 %, which were 74.7 % and 70.3 % higher than those prepared by TSE, while the enhancement rates rose to 174.6 % and 74.4 % when 30 wt% h-BN was added, respectively. The in-plane thermal conductivity enhancement ratio of NTSE was more than 3000 % when the h-BN content was higher than 10 wt%. Besides, the thermal stability, crystallinity, and thermal diffusion of the NTSE composites were also enhanced to different degrees. This strategy is efficient to coordinating the conflicting between the comprehensive performance and large-scale preparation of thermally conductive polymer composites.

Biodegradable antimicrobial films prepared in a continuous way by melt extrusion using plant extracts as effective components

Packaging plays an important role in delaying food spoilage. However, conventional packaging films do not have antimicrobial properties. Films with antimicrobial components are receiving growing research interest. However, many of the reported studies use conventional non-degradable polymers during film preparation, posing a significant threat to the environment and sustainable development. Furthermore, conventional inorganic antibacterial agents are commonly used during film preparation, posing a risk to food safety. In this study, antibacterial compounds were extracted from diverse plants, and then biodegradable antimicrobial films were prepared in a continuous way via the melt extrusion method. Especially, films prepared using Vernicia fordii and Phyllanthus urinaria extracts showed effective antibacterial activities against common foodborne pathogens. This study is the first to prepare antibacterial films in a continuous way using natural plant extracts as the effective components, and may shed new light on future research in preparing green antibacterial films via environment-friendly approaches.

Improved Performance of Polylactic Acid Biocomposites at High Lignin Loadings through Glycidyl Methacrylate Grafting of Melt-Flowable Organosolv Lignin.

Glycidyl methacrylate (GMA) was grafted onto a melt-flowable organosolv lignin, called bioleum (BL), using a melt mixing process. Then, up to 40 wt % of BL-g-GMA was blended with polylactic acid (PLA) in the presence of dicumyl peroxide as a free radical initiator utilizing a melt extrusion method. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and tensile testing were performed to characterize the biocomposites' performance. The FTIR results revealed a successful grafting of GMA onto BL. Overall, BL and PLA compatibility increased significantly with the grafting and resulted in decreased domain size of BL-g-GMA and thus enhanced all the tensile properties (strength, modulus, and elongation at break) at BL loadings as high as 40 wt %. For instance, in the biocomposites containing 30 wt % BL, the GMA grafting increased the tensile strength by 23%. The presence of BL and BL-g-GMA hindered PLA's crystallization even when it was cooled at a rate of 1 °C/min. However, the composites with BL-g-GMA showed a crystallinity value comparable to that of PLA during isothermal crystallization, but with a slower crystallization rate. This work reveals a facile and scalable method that can be adopted to enhance the performance of lignin-based biocomposites.

Fabrication of multi-layered polymer-based polypill using single-nozzle Fused Deposition Modeling and its dissolution mechanism

The meteoric rise of additive manufacturing has enabled it to create remarkable feats in the field of pharmaceutics and drug delivery applications. The main objective of this study was to print a polypill, having two drugs of common ailments in different layers, using a single nozzle Fused Deposition Modeling (FDM), instead of using a complex and cost-intensive dual extrusion printer. This was accomplished through a thermally fused filament. Myo-inositol (MI) and methylcobalamin (MCB) were the two drugs used for the present study. Initially, polyvinyl alcohol (PVA) filaments have been loaded with these drugs using Hot Melt Extrusion (HME) method and then, fused using heat and this blended filament has been fed into the FDM printing apparatus. These filaments have been used to finally obtain a polypill containing drugs in an alternate layer fashion. Various tests related to the filaments and tablets have been carried out to analyse the chemical, physical and thermal feasibility of this research attempt. The thermal analysis like Differential Scanning Calorimetry (DSC), Thermogravimetric (TGA) analysis tests confirmed filaments to be stable at printing temperature and FTIR results affirmed non-existence of any adverse degradation reaction in the drugs or other constituents. In-vitro dissolution studies were also conducted on the polypill and it was revealed that the dissolution rate for MI has been significantly higher than that of MCB drug. MI drug released completely in 5 h while MCB part was complete by 6.5 h. Finally, the drug dissolution behaviour was examined based on the dissolution data.

Fluorescent Polylactic acid composite incorporating lignin-based carbon quantum dots for sustainable 4D printing applications

Fluorescent 4D printing materials, as innovative materials that combine fluorescent characteristics with 4D printing technology, have attracted widespread interest and research. In this study, green lignin-derived carbon quantum dots (CQDs) were used as the fluorescent module, and renewable poly(propylene carbonate) polyurethane (PPCU) was used for toughening. A new low-cost fluorescent polylactic acid (PLA) composite filament for 4D printing was developed using a simple melt extrusion method. The strength of the prepared composite was maintained at 32 MPa, while the elongation at break increased 8-fold (34 % increase), demonstrating excellent shape fixed ratio (∼99 %), recovery ratio (∼92 %), and rapid shape memory recovery speed. The presence of PPCU prevented fluorescence quenching of the CQDs in the PLA matrix, allowing the composite to emit bright green fluorescence under 365 nm ultraviolet light. The composite exhibited shear thinning behavior and had an ideal melt viscosity for 3D printing. The results obtained demonstrated the versatility of these easy-to-manufacture and low-cost filaments, opening up a novel and convenient method for the preparation of strong, tough, and multifunctional PLA materials, increasing their potential application value.

Thermal and Mechanical Properties of Bio‐Based Polyamide 56/6 Filled with Talc

AbstractPolyamide composites with varying filler concentrations are prepared using the hot melt extrusion method, employing polyamide 56/6 (PA56/6) and modified talc as fillers. Initially, the thermal characteristics of PA56/6 composites (PA56/6‐talc) are examined through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), encompassing parameters such as melting temperature, crystallinity, and decomposition temperature. The hydrophilicity and barrier properties of PA56/6‐talc are assessed using an optical contact angle meter, a water vapor transmission rate tester, and an oxygen transmission rate tester. Furthermore, the mechanical properties of PA56/6‐talc are also scrutinized. The results indicate that PA56/6 exhibits superior hydrophobic, barrier, and mechanical properties, thereby demonstrating its immense potential in garment fabrics and packaging materials.

The Role of a Silane Coupling Agent in Common Photovoltaic Encapsulation Systems

Grafts of silane coupling agent EVA and POE were prepared by twin-screw melt extrusion method to obtain grafts EVA-g-KH171 and POE-g-KH171. The effect of silane coupling agent KH171 on the properties of two commonly used encapsulants in the photovoltaic field was investigated. The changes in the melt index of the grafts were tested by different dosages of silane coupling agents to explore further the effect of the changes in the melt index of the two grafting products, namely, EVA and POE, on the peeling strength. With the addition of the silane coupling agent, the melt index of the grafting product of EVA and POE increased. The peel strength test showed that the silane coupling agent KH171 had a more significant improvement in the adhesion of EVA and POE, proving the feasibility of its application in practical conditions.

Preparation of nano-CuO@BaSO4 under room temperatures and its application in PA6 composites

In this work, by simply using barium hydroxide (Ba(OH)2·8H2O) to react with cupric(II) sulfate pentahydrate (CuSO4.5H2O) in methanol under room temperatures, cupric oxide and barium sulfate co-precipitates (CuO@BaSO4) were one-step prepared, and the methanol can be recycled after separating the co-precipitates. The CuO@BaSO4 co-precipitates were then blended with polyamide 6 (PA6) to prepare PA6-CuO@BaSO4 composites and composites fiber via melt extrusion and melt spinning methods to improve the mechanic and antibacterial properties synchronously. The as-prepared CuO@BaSO4 co-precipitates have a regular size of 30–50 nm and are highly compatible with the PA6 matrix. Further investigations disclosed that the CuO@BaSO4 co-precipitates had a good dispersion in the PA6 matrix and synchronously improved the mechanical properties and thermal stability. What’s more, the PA6-CuO@BaSO4 composites showed excellent antibacterial performance and high spinnability. The bactericidal rate reached 100% when adding tiny content (0.24 wt%) of Cu2+ into PA6 fibers.

High strength and water tolerance fish gelatin-xanthan gum acid-induced electrostatic film by melt extrusion method

Gelatin is a biodegradable natural polymer that can be utilized in preparing edible films, and its films tend to have defects in mechanical properties and water tolerance, limiting their application. In this study, we combined the acid-induced electrostatic system to prepare the gelatin extruded film, and the relevant mechanisms were explored. The films' thermal stability, microstructure, mechanical properties, water tolerance, and degradability were also evaluated. Films were prepared by adding different levels of xanthan gum and malic acid to the film substrate. Compared to FG-M-0%, FG-MX-0.5% showed a 120.61% increase in tensile strength, a 9.79 °C and a 16.72 °C increase in melting temperature and glass transition temperature, respectively, the acidified FG-MX group as a whole had a higher water contact angle and lower swelling rate. FTIR and XRD confirmed that acid induction enhanced the electrostatic interactions and hydrogen bonding between gelatin-xanthan gum. The results showed that the melt-extruded gelatin film could also maintain the acid-induced electrostatic effect well, with stronger physical properties and better water tolerance, and were conducive to the efficient preparation of gelatin films with desirable properties and the expansion of their range of applications.

Development of nanocomposite with LDPE and Graphene nanoparticles by means of melt extrusion method

Graphene nanoparticles have found an important role in the field of nano composites as a potential filler material through enhancement of the matrix property. In the present study graphene nanoparticles in varying amounts are mixed with low density polyethylene, the most extensively used polyolefin using melt extrusion method. This manufacturing process imposes strong anisotropy on the sample’s morphology where the filler particles are oriented along the extrusion direction. The nano composite prepared was found to exhibit excellent thermal withstanding behaviour. The Differential Scanning Calorimetry (DSC) study results had shown that as the amount of filler is varied, the thermal properties material is found to be enhanced compared with the virgin polymer. The absorption properties of the composite were verified using UV visible photometer. As the amount of graphene nanoparticles is increased the intensity of absorption of the composite is also found to be increased. Developed material with enhanced thermal stability can find applications in electric and electronic devices specifically in biomedical field where soft and flexible material are required.

Preparation and applicability of polylactic acid/polyethylene glycol/nanoclay composite films for smart steam release in microwave packaging

Smart materials are developed to serve additional functions in food packaging, including self-release features depending on temperature. Typically, phase change materials (PCMs) are used to impart smart functions to packaging materials. In this study, self-steam-releasing films were developed by compounding polylactic acid (PLA) with PCM derived from polyethylene glycol (PEG) and nanoclay using the melt-extrusion method. PEG as the PCM in the inner gallery of nanoclay endowed the nanocomposite film (PLA-G-C) with the steam-release behavior. The oxygen transmission rate of the nanocomposite films was strongly dependent on temperature, and a rapid increase in permeability was observed in the vicinity of the PEG melting point. In the microwave application test, the built-up steam inside the packaged container during microwave heating was safely released through the PLA-G-C nanocomposite films without bursting the package. Therefore, the as-developed temperature-responsive PLA-G-C nanocomposite films can be potentially used as smart steam-release materials for microwave food packaging.

Creep behavior of 3D printed polymer composites

AbstractThe creep behavior of polymer composites containing different weight percentages of poly(lactic) acid (PLA), thermoplastic polyurethane (TPU), and poly(ethylene) glycol (PEG) is experimentally characterized and computationally modeled using finite element analysis (FEA). The composite filaments are manufactured with melt extrusion method by using twin‐screw extruders, and then are employed in the 3D printing of creep samples. The samples are tested under a constant tensile load of 100 N. In this study, the computational model is developed by using the Generalized Voigt‐Kelvin solid model and three terms in Prony series. The equations of Prony series were obtained by the Laplace transformation of Kelvin model. The experimental creep displacements and strains are compared with computational results, and a good agreement between them is observed. The maximum error percentage in computational result is approximately 6% as compared to the experimental result. Hence, it can be said that the relatively simple computational models developed are reliable and can be used to study the creep behavior of similar polymers. The error percentages can still be reduced by considering a higher number of terms of Prony series in the model.Highlights Studied creep behavior for additively manufactured thermoplastic polymer composites. Developed computational model using three terms of relaxation modulus. The experimental results correlate very well with the computational model. Computational models can be used for other polymers.

The Use of Hot Melt Extrusion to Prepare a Solid Dispersion of Ibuprofen in a Polymer Matrix.

In this work, we report the use of the hot melt extrusion method in harsh extrusion conditions, i.e., screw rotation speed of 250 rpm, temperature above 100 °C, and two mixing zones, in order to obtain an amorphous dispersion of an active pharmaceutical ingredient (API) that is sparingly soluble in water. As a polymer matrix Eudragit EPO (E-EPO) and as an API ibuprofen (IBU) were used in the research. In addition, the plasticizer Compritol 888 ATO (COM) was tested as a factor potentially improving processing parameters and modifying the IBU release profile. In studies, 25% by weight of IBU, 10% of COM and various extrusion temperatures, i.e., 90, 100, 120, 130, and 140 °C, were used. Hot melt extrusion (HME) temperatures were selected based on the glass transition temperature of the polymer matrix (Tg = 42 °C) and the melting points of IBU (Tm = 76 °C) and COM (Tm = 73 °C), which were tested by differential scanning calorimetry (DSC). The thermal stability of the tested compounds, determined on the basis of measurements carried out by thermogravimetric analysis (TGA), was also taken into account. HME resulted in amorphous E-EPO/IBU solid dispersions and solid dispersions containing a partially crystalline plasticizer in the case of E-EPO/IBU/COM extrudates. Interactions between the components of the extrudate were also studied using infrared spectroscopy (FTIR-ATR). The occurrence of such interactions in the studied system, which improve the stability of the obtained solid polymer dispersions, was confirmed. On the basis of DSC thermograms and XRPD diffractograms, it was found that amorphous solid dispersions were obtained. In addition, their stability was confirmed in accelerated conditions (40 °C, 75% RH) for 28 days and 3 months. The release profiles of prepared tablets showed the release of 40% to 63% of IBU from the tablets within 180 min in artificial gastric juice solution, with the best results obtained for tablets with E-EPO/IBU extrudate prepared at a processing temperature of 140 °C.

The effect of diatomite dosage on physical, mechanical, and rheological creep properties of poplar wood/polypropylene composites

AbstractThe present study investigates the influence of micron‐sized diatomite dosage on the physical, mechanical, rheological, and creep properties of poplar wood/polypropylene (PW/PP) composites to enhance their toughness and practicality. The diatomite‐PW/PP composites were prepared using the melt extrusion method, replacing different proportions of PW with diatomite, and subsequently evaluated for their properties. The results indicate that adding diatomite enhances the density while reducing the brightness and water absorption of the composites. Scanning electron microscopy, analysis reveals a uniform distribution of diatomite in the range of 5–10 wt%, which effectively serves as a filler and reinforcing agent, consequently improving the toughness of the composite system. Specifically, the impact strength, tensile strength, and elongation at break are enhanced by 25.9%, 9.5%, and 35.7%, respectively. Furthermore, creep rheological analysis demonstrates improved processability and creep resistance in the composite system.

Properties of polyphenylene sulphide/glass fibre composites with negative thermal expansion ceramic fillers

The high coefficient of thermal expansion (CTE) of polymeric composites can cause large deformation under temperature changes, affecting coupling with devices made of other materials in radio frequency (RF) communication systems and limiting their application in RF systems. In order to obtain polyphenylene sulphide (PPS)-based composites with low CTE, a series of PPS-based composites containing different loadings of ceramic powders (including Zr2WP2O12, BN, AlN, Al2O3) were fabricated by melt extrusion method using PPS with 40 wt% glass fibre (GF) as matrix material. The experimental results showed that the PPS composites with Zr2WP2O12 (ZWP) as a filler had a lower CTE compared to the samples with other fillers at the same filler loading. The CTE of PPS/GF/ZWP steadily decreased with increasing ZWP addition. At 20 vol% ZWP loading, a 67% (about 18 ppm/°C) reduction of CTE compared to the PPS/GF was achieved. The addition of ZWP powder to PPS/GF also led to an improvement in the dielectric loss of the composite. When the ZWP content is 20 vol%, the dielectric loss of the composites is about 0.0035, which is 24.4% lower than PPS/GF. Hence, the PPS/GF/ZWP composites have great potential for applications in RF communication systems.

Polylactic acid biocomposites with high loadings of melt-flowable organosolv lignin

Polylactic acid (PLA) was blended with a new type of organosolv lignin, called Bioleum (BL) using a melt extrusion method to obtain biocomposites with BL loadings as high as 40 wt%. Two plasticizers, namely polyethylene glycol (PEG) and triethyl citrate (TEC) were also introduced to the material system. Gel permeation chromatography, rheological analysis, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy and tensile testing were performed to characterize the biocomposites. The results revealed that BL exhibits a melt-flowable characteristic. The biocomposites' tensile strength was found to be higher than most of the previously reported cases. Overall, the BL domain size increased as the BL content was increased, causing a drop in the strength and ductility. Even though the addition of both PEG and TEC improved the ductility, PEG proved to significantly outperform TEC. With the introduction of 5 wt% PEG, the elongation at break of PLA_BL20 was increased >9 times, even exceeding that of the neat PLA by several folds. Consequently, PLA_BL20_PEG5 produced a toughness that is twice as the of the neat PLA. The findings suggest a great promise of BL to develop scalable and melt processable composites.

Polydopamine surface functionalized submicron ZnO for broadening the processing window of 3D printable PLA composites

The “catalytic degradation” of metal oxides limits the wide application of PLA when PLA needs to be modified by adding metal oxides to achieve desired properties. Zinc oxide (ZnO) is a common and widely used agent as it can be used for many properties, such as antioxidant, antibacterial, etc. However, detrimental effects often exist on the properties of polymers after introducing the ZnO, due to the catalytic degradation. In this study, we used polydopamine (PDA) to construct ZnO@PDA core-shell submicron particles via the self-polymerization of dopamine (DA) in alkaline solution, aimed to produce a surface functionalization that would be used to control the rate of degradation of PLA by ZnO during thermal processing, and promote the preservation of mechanical properties. PLA with different contents of ZnO and ZnO@PDA were prepared by a simple melt extrusion method. The degradation behavior, mechanical properties and antibacterial activity of ZnO/PLA and ZnO@PDA/PLA were investigated. It was found that the incorporation of ZnO@PDA in PLA at different contents exhibits a dramatic control over the degradation rate when compared to that of the ZnO/PLA with the same filler content. Notably, the T5% and T50% of 3%-ZnO@PDA/PLA increased by 36.4 oC and 31.9 oC. GPC results showed the molecular weight of 3%-ZnO@PDA/PLA was only reduced by 15.8% after thermal processing. In addition, 3%-ZnO@PDA/PLA can be 3D-printed smoothly. That is to say, the introduction of ZnO@PDA can increase the processing window of PLA/ZnO composites, providing the possibility for materials that need to be included in civil application. Accordingly, ZnO@PDA/PLA samples showed higher tensile strength and elongation at break than that of corresponding ZnO/PLA samples. Regarding the antibacterial behavior, the ZnO@PDA/PLA have more bacterial growth disability effect against Gram(+) bacteria than that of pure PLA.

Fabrication and characterization of polylactic acid/natural fiber extruded composites

AbstractIn this work, the fabricated polylactic acid (PLA) and hybrid natural fiber (NF) biocomposites via a melt extrusion method were investigated. NFs from locally grown plants were utilized as fillers. Polyethene glycol (PEG) was used as the plasticizer to improve the processability of the PLA. The effect of PLA/NF biocomposite processing was assessed by mechanical characterization (tensile, modulus, strain at break, and impact tests), and thermal properties (thermogravimetric analysis and differential scanning calorimetry [DSC] analysis). The dynamic mechanical analysis (DMA), and thermo‐mechanical analysis (TMA) of the samples were also analyzed. The mechanical properties of PLA/NF biocomposites improved as compared with that of PLA. The DMA findings show that the storage modulus and loss modulus exhibited a slight reduction for PLA/NF biocomposites compared with the PLA sample. In opposite, the glass transition temperature (Tg) from DSC thermogram results showed no obvious changes in values compared with the PLA sample. Furthermore, the findings of TMA showed a significant decrease in coefficient of thermal expansion values of PLA/NF biocomposites compared with those of PLA samples. The overall findings from this work indicated that PLA/NF biocomposites have the potential to make novel biocomposites and suitable for further application especially in biomedical applications due to its good stiffness, tensile strength, and dimensional stability.

Effervescence-induced amorphous solid dispersions with improved drug solubility and dissolution

The current study aimed to investigate drug carrier miscibility in pharmaceutical solid dispersions (SD) and include the effervescent system, i.e. Effervescence-induced amorphous solid dispersions (ESD), to enhance the solubility of a poorly water-soluble Glibenclamide (GLB). Kollidon VA 64, PEG-3350, and Gelucire-50/13 were selected as the water-soluble carriers. The miscibility of the drug-carrier was predicted by molecular dynamics simulation, Hansen solubility parameters, Flory-Huggins theory, and Gibb’s free energy. Solid dispersions were prepared by microwave, solvent evaporation, lyophilization, and Hot Melt Extrusion (HME) methods. The prepared solid dispersions were subjected to solubility, in-vitro dissolution, and other characterization studies. The in-silico and theoretical approach suggested that the selected polymers exhibited better miscibility with GLB. Solid-state characterizations like FTIR and 1H NMR proved the formation of intermolecular hydrogen bonding between the drug and carriers, which was comparatively higher in ESDs than SDs. DSC, PXRD, and microscopic examination of GLB and SDs confirmed the amorphization of GLB, which was higher in ESDs than SDs. Gibb’s free energy concept suggested that the prepared solid dispersions will be stable at room temperature. Ex-vivo intestinal absorption study on optimized ESDs prepared with Kollidon VA64 using the HME technique exhibited a higher flux and permeability coefficient than the pure drug suggesting a better drug delivery. The drug-carrier miscibility was successfully studied in SDs of GLB. The addition of the effervescent agent further enhanced the solubility and dissolution of GLB. Additionally, this might exhibit a better bioavailability, confirmed by ex-vivo intestinal absorption study.

Mechanical properties and injection molding processability of glass fiber modified polylactic acid composites

In order to promote the development and application of environment-friendly plastics, a glass fiber-modified starch/polylactic acid composite was prepared by the melt extrusion method. The influence of glass fiber content on the mechanical and thermal properties of the composite was studied, and multi-objective optimization of the injection molding process was carried out with consideration of the influence of material properties. The results show that with the increase of glass fiber content from 0 to 5%, the tensile strength of the composite decreases first and then increases to an average of 60Mpa, which is about 30% higher than that of pure polylactic acid. The elastic modulus and thermal stability increase, while the elongation at break and flow rate decrease with the increase of glass fiber content. In addition, the optimized injection parameters are obtained, which can effectively reduce the warping deformation, volume shrinkage, and residual stress of injection parts. Glass fiber modified starch/polylactic acid composites show great potential in engineering application, and may provide a reference for the development and application of high-performance and green degradable materials.