Hot Melt Research Articles

Comparison and investigation of H-bond assisted reusable PU adhesives with high shear strength

Hot-melt adhesive (HMA) is commonly used in industrial manufacturing due to its ease of use. However, the direct factors that affect shear strength have been unclear in recent years, making it difficult to prepare hot melt adhesives with high shear strength, which are mostly lower than 6 MPa. In this study, three types of polyurethane HMAs, differing in the position of H-bond motifs, ureidopyrimidinone (UPy), were synthesized and characterized, the most central factor for shear strength, Young's modulus, was firstly found out and proved. Side-chain UPy provides better flexibility and more chain entanglement. The lap shear strength of SPU was about 13.48 MPa, which was the highest shear strength of PU HMA, and remained 73.4 % even after 4 cycles. Compared to the other two samples, the side-chain motifs improved the possibility of forming hydrogen bonds with adherends and increased chain mobility. This led to a more efficient wetting process and strengthened Young's modulus directly, enhancing adhesive property incomparably. This work provides a satisfactory method for achieving high shear strength in HMA.

Amorphous solid dispersion of a binary formulation with felodipine and HPMC for 3D printed floating tablets

This study focuses on the combination of three-dimensional printing (3DP) and amorphous solid dispersion (ASD) technologies for the manufacturing of gastroretentive floating tablets. Employing hot melt extrusion (HME) and fused deposition modeling (FDM), the study investigates the development of drug-loaded filaments and 3D printed (3DP) tablets containing felodipine as model drug and hydroxypropyl methylcellulose (HPMC) as the polymeric carrier. Prior to fabrication, solubility parameter estimation and molecular dynamics simulations were applied to predict drug-polymer interactions, which are crucial for ASD formation. Physical bulk and surface characterization complemented the quality control of both drug-loaded filaments and 3DP tablets. The analysis confirmed a successful amorphous dispersion of felodipine within the polymeric matrix. Furthermore, the low infill percentage and enclosed design of the 3DP tablet allowed for obtaining low-density systems. This structure resulted in buoyancy during the entire drug release process until a complete dissolution of the 3DP tablets (more than 8 h) was attained. The particular design made it possible for a single polymer to achieve a zero-order controlled release of the drug, which is considered the ideal kinetics for a gastroretentive system. Accordingly, this study can be seen as an advancement in ASD formulation for 3DP technology within pharmaceutics.

Mechanochemical Evaluation of a Hot Melt Extruded Ready-to-Print Etoricoxib Macrofilament as Printing Ink for Additive Manufacturing

Mechanochemical Evaluation of a Hot Melt Extruded Ready-to-Print Etoricoxib Macrofilament as Printing Ink for Additive Manufacturing

Solvent-free synthesis of pendant crosslinked polyurethane hot melt adhesive via dynamic Diels-Alder reaction

Pendant cross-linked polyurethane hot melt adhesive was synthesized without any solvents via Diels-Alder reaction (DA reaction) and was coded as DAPU. Firstly, a chain extender containing furan ring was synthesized via Michale addition reaction between hydroxyethyl acrylate (HEA) and furfuryl amine (FA). Secondly, the polyurethane prepolymer with pendant furan rings was synthesized from the reaction between the chain extender and isocyanate-terminated polyurethane prepolymer. Finally, the hot melt adhesive was cross-linked via DA reaction between furan rings and bismaleimide (BMI) without organic solvents due to the viscosity inhibition at higher temperature. DAPU exhibited a higher bonding performance (11.2 MPa) than the commercial reactive polyurethane hot melt adhesive (PUR-Ausbond 3550) and can reach 10.2 MPa after three times break as thermoplastic polyurethane hot melt adhesive (TPU-XJU83), due to the higher cross-linked density and the thermal reversibility of DA adducts. This confirmed that DAPU combined the merits of the two kinds of polyurethane hot melt adhesives successfully without involving solvents.

Innovative material applications in clothing design research

With the improvement of living standards, there is a growing demand for clothing that offers both comfort and functionality. Nanomaterials have emerged as a hot topic in clothing design due to their unique structure and performance characteristics. In this study, we develop a composite nanofabric with exceptional water resistance and breathability using polyurethane (PU), fluorinated polyurethane (FPU), and polyvinyl butyral (PVB), namely PU-FPU-PVB composite nanofabric. The mechanical properties, wettability, waterproofing, and thermal comfort are evaluated. The results demonstrate that optimizing the TPU and PVB contents is crucial for obtaining PU-FPU-PVB composite nanofabrics with exceptional performance. Low TPU concentrations fail to provide sufficient viscosity for even dispersion within the hot melt adhesive mesh film, while higher concentrations enable better dispersion due to increased viscosity provided by TPU. Additionally, increasing the content of PVB from 0 wt% to 100 wt% led to decreased moisture permeability from 10.5 kg ·m−2 · d−1 to 3.0 kg ·m−2 · d−1 during thermal comfort testing. Its permeability dropped from 22.5 mm/s to 2.8 mm/s under these conditions. These findings indicate that our designed composite nanofabric exhibits excellent thermal comfort when incorporating appropriate levels of PVB into its composition, making it an ideal high-performance material for waterproof and breathable fabrics with superior comfort and functionality in clothing design applications. In conclusion, PU-FPU-PVB composite nanofabrics hold great potential for fostering the innovative advancement of nanomaterials in the realm of clothing design.

Hot Melt Extrusion Technology as a Modern Strategy for Improving the Bioavailability of Flavonoids

Hot Melt Extrusion Technology as a Modern Strategy for Improving the Bioavailability of Flavonoids

Design of melting parameters for safety airbag labels based on hot air welding technology: CFD simulation and experimental validation

This paper focuses on researching the various factors that influence the material melting rate during the hot air melting process. To achieve this purpose, the paper proposes a melting model for Acrylonitrile-Butadiene-Styrene (ABS) plastic under hot air heating based on Computational Fluid Dynamics (CFD). Orthogonal experiments were conducted based on the parameter range of each factor obtained in the pre-experiment. The results showed that the outlet distance, hot air velocity, hot air temperature, and their interaction items are important factors that affect the melting rate of ABS materials. Based on the simulation results, a multiple nonlinear regression model was constructed to predict the melting rate under different parameters. Comparing the simulation values with the predicted values of the multiple nonlinear regression model, the error between the two was no >10%, indicating the effectiveness of the prediction model. The research results can help guide the hot air welding melting process for different materials and characteristics, and provide a certain reference value for the development of hot air welding technology.

Energy Harvesting Floor Tile Using Piezoelectric Patches for Low-Power Applications

Abstract Purpose One of the sustainable energy sources derived from kinetic energy is human footsteps. This research sought to find a substitute for conventional power sources to lessen dependence on them. As a result, a floor tile excited by human footsteps was demonstrated and presented to generate usable electrical power. Methods Piezoelectric patches, hot melt glue sticks, wood plates, and foam plates are just a few of the commercially available materials used in the suggested technique, making it suitable and practical. In addition to the components, uncomplicated circuits like a voltage multiplier and rectifier with a capacitance filter were employed for the electrical power capture. The proposed prototype has a length of 455 mm and a width of 405 mm. Results Two LEDs were effectively illuminated as an actual load using electrical energy collected from human footsteps. The maximum useful power that could be harvested successfully via the proposed floor tile (one tile) was 246 mW, with an approximate cost of $10.2. Conclusions Designing an array of footsteps-based energy harvesting tiles covering broad areas to maximize the harvested power could be considered as a future work. Moreover, the number of pedestrians variable can be also studied for the proposed design of this study in a real excitation environment such as a railway station, subway station, street, discotheque, and wedding festival hall.

Evaluation of the Viability of 3D Printing in Recycling Polymers.

The increased use of plastics in industrial and agricultural applications has led to high levels of pollution worldwide and is a significant challenge. To address this plastic pollution, conventional methods such as landfills and incineration are used, leading to further challenges such as the generation of greenhouse gas emissions. Therefore, increasing interest has been directed to identifying alternative methods to dispose of plastic waste from agriculture. The novelty of the current research arose from the lack of critical reviews on how 3-Dimensional (3D) printing was adopted for recycling plastics, its application in the production of agricultural plastics, and its specific benefits, disadvantages, and limitations in recycling plastics. The review paper offers novel insights regarding the application of 3D printing methods including Fused Particle Fabrication (FPF), Hot Melt Extrusion (HME), and Fused Deposition Modelling (FDM) to make filaments from plastics. However, the methods were adopted in local recycling setups where only small quantities of the raw materials were considered. Data was collected using a systematic review involving 39 studies. Findings showed that the application of the 3D printing methods led to the generation of agricultural plastics such as Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Polyethylene Terephthalate (PET), and High-Density Polyethylene (HDPE), which were found to have properties comparable to those of virgin plastic, suggesting the viability of 3D printing in managing plastic pollution. However, limitations were also associated with the 3D printing methods; 3D-printed plastics deteriorated rapidly under Ultraviolet (UV) light and are non-biodegradable, posing further risks of plastic pollution. However, UV stabilization helps reduce plastic deterioration, thus increasing longevity and reducing disposal. Future directions emphasize identifying methods to reduce the deterioration of 3D-printed agricultural plastics and increasing their longevity in addition to UV stability.

Amphiphilic hot-melt pressure sensitive adhesives for transdermal administration made from low melt-processing temperature OSISO copolymers

Herein, an anionic polymerization method was employed to synthesize a series of amphiphilic poly(ethylene oxide-b-styrene-b-isoprene-b-styrene-b-ethylene oxide) penta-block copolymers (OSISO). Their molecular structure and properties were comprehensively characterized using GPC,1H-NMR, thermodynamic rheological testing and water contact angle test. Notably, the hydrophilic characteristics exhibited a proportional increase with the rise in poly(ethylene oxide) (PEO) content, ranging from 1.3 to 12.6 wt%. The polystyrene blocks with low number-average molecular weight (2000–3500) reduced the copolymer melt viscosity, surpassing a tenfold decrease than the control sample within the temperature range of 50–150 °C. Resultantly, this series of OSISO copolymers could be used to develop amphiphilic hot-melt pressure-sensitive adhesives (HMPSAs) by low temperature hot-melt processing method (<120 °C). HMPSAs loaded with 2 wt% of geniposide, prepared by an optimized composition formula of OSISO copolymers, tackifiers, and plasticizers (in a ratio of 5:5:2), displayed excellent in vitro drug release performance. Additionally, these adhesives presented impressive 180° peeling strength (0.05–0.14 kN/m) without residues left on the substrate in the 180° peeling tests. The incorporation of PEO block significantly enhanced both the adhesive properties and accumulative drug release. Geniposide showed a burst release behavior with a moderate accumulative drug release (15–30 wt%), attributed to the PEO phase without crystallization behavior of long PEO chains.

A DIRECT BONDING TECHNIQUE VERSUS AN INDIRECT BONDING TECHNIQUE - AN IN VIVO ANALYSIS

Objectives: The objectives of this study were to compare the clinical performance of an indirect versus a direct bonding technique in a split mouth study design and to develop a reproducible and cost efficient technique for indirect bonding for clinical use. Methods: This comparative study was conducted on Twelve patients (212 teeth; 106 each in direct and indirect group) who reported to the Department of Dentistry at Ruxmaniben deepchand gardi medical college, Ujjain, Madhya Pradesh. Transbond XT (3M Unitek) adhesive and primer were used to bond the brackets onto the teeth in both the direct and indirect bonding groups using split mouth study design. Transfer trays constructed using Thermal glue matrix applied through hot glue gun for indirect bonding. The clinical performance was assessed for 6 months. Results: In the 1st month was a failure of one lower 2nd premolar bracket from the indirect bonding group (p=1.00). There on in the subsequent months there were no failures for 6 months. The study showed no statistically significant differences in clinical performance in both group (p=NS). Conclusion: The failure rates for both the indirect and direct bonding techniques in this study were the same. Statistically, there was no significant difference between the two groups. The indirect bonding technique used in this study was found to be an effective and efficient means of bonding orthodontic brackets. Transbond XT and thermal glue matrix found to be suitable choice for use in indirect bonding technique for clinical use.

Preliminary study on terahertz non-destructive testing for defect detection in hot melt joints of polyethylene pipes

With the rapid development of the economy and society, non-metallic pipelines are more and more widely used in oil and gas fields, water supply projects, urban gas systems, and so on. Among the conventional nondestructive testing (NDT) methods, only ultrasonic, radiographic, and penetration testing tools are applicable to non-metallic pipe examination from a theoretical perspective, while their actual efficiency is quite low. In this work, terahertz (THz) non-destructive detection of typical welding defects in polyethylene-pipe hot melt joints is carried out. The characteristic THz wave signal is obtained, and the relationship between the THz wave and the defect type is established. Finally, a THz signal processing model for defect detection in polyethylene-pipe hot melt joints is established. Thus, this research lays a foundation for the application of the THz non-destructive testing technology to polyethylene pipeline engineering.

Formulation and Evaluation of Solid Dispersion of Felodipine by Hot Melt Extrusion for Enhancement of Solubility

ABSTRACT Background: Felodipine (BCS Class II) undergoes extensive first-pass metabolism with bioavailability of about 15% that creates problem in therapeutic efficacy after oral administration. Objective: Immediate release formulation of felodipine was developed using hot-melt extrusion (HME) technique in an attempt to improve solubility and dissolution of felodipine through the solid dispersion technique. Materials and Methods: The solid dispersion was prepared using Eudragit EPO, NE30D as a carrier with different drug polymer ratios using the HME technique. The optimized batch was made into tablets. The solid dispersion was characterized by solubility studies, drug content, and in vitro dissolution rate studies. Results: From the cumulative dissolution profile, it was observed that the drug and Eudragit EPO alone have the highest percentage of drug release compared to the other combinations of drug and Eudragit EPO, NE30D. It is also evident from the dissolution profile that with increase in the concentration of Eudragit NE30D, there is a decrease in the dissolution rate. There was a significant decrease in drug release even with increase in stabilizer in a smaller ratio. The dissolution profile showed that there is not much variation in the release profile of the solid dispersion alone and the solid dispersion tablets. Conclusions: Solid dispersion by the HME technique is an effective method to increase the dissolution rate of felodipine.

Understanding the Interaction of Thermal, Rheological, and Mechanical Parameters Critical for the Processability of Polyvinyl Alcohol-Based Systems during Hot Melt Extrusion.

Hot melt extrusion (HME) is a common manufacturing process used in the pharmaceutical industry to improve the solubility of poorly soluble active pharmaceutical ingredients (API). The goal is to create an amorphous solid dispersion (ASD) where the amorphous form of the API is stabilized within a polymer matrix. Traditionally, the development of pharmaceutically approved polymers has focused on requirements such as thermal properties, solubility, drug-polymer interactions, and biocompatibility. The mechanical properties of the material have often been neglected in the design of new polymers. However, new downstream methods require more flexible polymers or suitable plasticizer polymer combinations. In this study, two grades of the polymer polyvinyl alcohol (PVA), which is already established for HME, are investigated in terms of their mechanical, rheological, and thermal properties. The mechanical properties of the extruded filaments were tested by the three-point bending test. The rheological behavior was analyzed by oscillating plate measurements. Thermal analysis was performed by differential scanning calorimetry (DSC). In addition, the solid and liquid plasticizers mannitol, sorbitol, triacetin, triethyl citrate, polyethylene glycol, and glycerol were evaluated for use with PVA and their impact on the polymer properties was elaborated. Finally, the effects of the plasticizers are compared to each other, and the correlations are analyzed statistically using principal component analysis (PCA). Thereby, a clear ranking of the plasticizer effects was established, and a deeper understanding of the polymer-plasticizer interactions was created.

Seamless, Self-Transformation of Thermoplastic Polyesters into Vitrimers Through Bond Exchange-Triggered Cross-Linking.

In this study, a seamless, self-transformation system of linear thermoplastic polyesters into the sustainable cross-linked polymers, vitrimers, is demonstrated. The key is the use of polyesters bearing abundant hydroxyl side groups, which are synthesized via the reaction using dithiol molecules bearing ester units and diepoxy molecules. The polymerization reaction progresses efficiently at relatively low temperature due to the click nature of the thiol-epoxy reaction, which provides the hydroxyl side groups along the polyester chain. The tin catalyst (stannous octoate) is added in the initial polymerization, and the catalyst also works to cross-link the polyesters via intermolecular transesterification bond exchange simply by heating at high temperatures. By adjusting the degrees of cross-linking, the mechanical properties as well as the thermal properties are well tuned. The bond exchange can still be activated in the final cross-linked sample; and thus, the material behaves as vitrimers, exhibiting mechanical recyclability. The application of a new type of hot melt adhesive, where the post-coating tuning/enhancement of adhesion strength is realized, is also demonstrated. On the whole, the present system is very simple but proposes a new application window of bond exchange concept into self-transformation polymers.

Formulation and evaluation of inhaled Sildenafil-loaded PLGA microparticles for treatment of pulmonary arterial hypertension (PAH): A novel high drug loaded formulation and scalable process via hot melt extrusion technology (Part Ⅰ)

In recent years, several techniques were employed to develop a local sustained pulmonary delivery of sildenafil citrate (SC) as an alternative for the intravenous and oral treatment of pulmonary arterial hypertension (PAH). Most of these methods, however, need to be improved due to limitations of scalability, low yield production, low drug loading, and stability issues. In this study, we report the use of hot-melt extrusion (HME) as a scalable process for making Poly (lactic-co-glycolic acid) (PLGA) microparticles with high SC load. The prepared particles were tested in vitro for local drug delivery to the lungs by inhalation. Sodium bicarbonate was included as a porogen in the formulation to make the particles more brittle and to impart favorable aerodynamic properties. Six formulations were prepared with different formulation compositions. Laser diffraction analysis was used to estimate the geometric particle size distribution of the microparticles. In-vitro aerodynamic performance was evaluated by the next-generation cascade impactor (NGI). It was reported in terms of an emitted dose (ED), an emitted fraction (EF%), a respirable fraction (RF%), a fine particle fraction (FPF%), a mass median aerodynamic diameter (MMAD), and geometric standard deviation (GSD). The formulations have also been characterized for surface morphology, entrapment efficiency, drug load, and in-vitro drug release. The results demonstrated that PLGA microparticles have a mean geometric particle size between 6 and 14 µm, entrapment efficiency of 77 to 89 %, and SC load between 17 and 33 % w/w. Fifteen percent of entrapped sildenafil was released over 24 h from the PLGA microparticles, and seventy percent over 7 days. The aerodynamic properties included fine particle fraction ranging between 19 and 33 % and an average mass median aerodynamic diameter of 6–13 µm.

Dispersion state analysis in hot melt extruded, highly drug-loaded 3D printing filaments applying Raman microscopy

Abstract Objectives Highly drug-loaded polymer formulations are favorable intermediates in pharmaceutical applications, for example, for the individualized production of medicines via 3D printing with the maximum flexibility regarding dose strength and drug combination in a single dosage form. However, high-disperse drug loads are challenging for the process itself and the (intermediate) product properties, making the knowledge about the dispersion state of the drug particles achieved by the production process helpful to overcome such challenges. Methods Therefore, a novel dispersion state analysis technique based on scanning Raman microscopy is proposed in the present study and applied to HPMC filaments loaded with 20 wt%, 40 wt%, and 60 wt% theophylline. The qualitative and quantitative evaluations of the scans were correlated to melt viscosities, process data, and mechanical properties of the filaments. Key findings The analyses revealed not only an increasing particle size reduction with increasing drug load and thus increasing viscosity and mechanical energy input. The particle size reduction also caused a change in the filaments’ mechanical properties from elastic ductile to rigid brittle. Furthermore, an alignment of the elongated drug particles with the frozen three-dimensional flow pattern of the extruder and not only with the extrusion direction was elucidated. Conclusions Therefore, the necessity to investigate the dispersion state further is highlighted for future studies on highly drug-loaded polymer formulations, providing a novel measuring technique applicable to challenging pharmaceutical formulations.

Insights into Factors Affecting Ethylene-Vinyl Acetate Copolymer Crystallinity in Islatravir Implant.

Islatravir, a highly potent nucleoside reverse transcriptase translocation inhibitor (NRTTI) for the treatment of HIV, has great potential to be formulated as ethylene-vinyl acetate (EVA) copolymer-based implants via hot melt extrusion. The crystallinity of EVA determines its physical and rheological properties and may impact the drug-eluting implant performance. Herein, we describe the systematic analysis of factors affecting the EVA crystallinity in islatravir implants. Differential scanning calorimetry (DSC) on EVA and solid-state NMR revealed drug loading promoted EVA crystallization, whereas BaSO4 loading had negligible impact on EVA crystallinity. The sterilization through γ-irradiation appeared to significantly impact the EVA crystallinity and surface characteristics of the implants. Furthermore, DSC analysis of thin implant slices prepared with an ultramicrotome indicated that the surface layer of the implant was more crystalline than the core. These findings provide critical insights into factors affecting the crystallinity, mechanical properties, and physicochemical properties of the EVA polymer matrix of extruded islatravir implants.

Colon-targeted 3D-Printed mesalamine tablets: Core-shell design and in vitro/ex-vivo evaluation

ObjectivesThe present study is intended to develop a shell-core tablet using a hot melt extrusion (HME)-based dual-nozzle fused deposition modeling (FDM) three-dimensional (3D) printing approach. The primary objective was to establish a sustained-release colonic drug delivery system and improve mesalamine's permeability by incorporating Vitamin E TPGS as a permeation enhancer. MethodThe study utilized Kollidon® SR for sustained release, L-100, and HPMC HME L100 for the tablet's protective shell. Six filament formulations were tested, and the mechanical properties of the shell filaments, including the three-point bending, Hooke's law, and stiffness, were assessed. Drug release profiles of the tablets were evaluated using the USP-II dissolution apparatus, and permeability characteristics were gauged using the non-everted intestinal sac method. Solutions containing 5% w/v mesalamine and 2.5% w/v Vitamin E TPGS were employed, with pure mesalamine as a control. ResultsOptimal filament ratios were identified as 50:50 for the core and 30:70 for Eudragit L-100 to HPMC HME L100 for the shell. The resulting tablets achieved a prolonged drug release of up to 24 h for the core. They ensured minimal drug release in the upper gastrointestinal tract (∼5% in the first 5 h), effectively targeting the colon. Incorporating Vitamin E TPGS led to a 3.6-fold increase in mesalamine absorption compared to the control, and the addition of Kollidon® SR notably improved the flow properties of Mesalamine powder. ConclusionIn conclusion, this innovative approach has the potential to achieve a colon-specific drug delivery system.

Preparation of tofacitinib sustained-release tablets using hot melt extrusion technology

This study aimed to develop a tablet that shows a drug release profile similar to the tofacitinib sustained-release tablet (Xeljanz XR®; OROS™) using hot melt extrusion technology. Tofacitinib citrate was selected as the drug. HPMCAS, HPMCP, and Kollidon VA64 were used as thermoplastic polymers to prepare a hot-melt extrudate. The extrudate was obtained from a twin screw extruder and pelletizer. The granules were compressed using a single punch press machine and then coated. TGA, DSC, XRD, FT-IR, and SEM were performed on the hot melt extrudate to understand its physicochemical properties. Dissolution tests were performed using the paddle method (USP Apparatus II). The results showed that the crystallinity state of tofacitinib changed to amorphous after the hot melt extrusion process; however, no chemical change was observed. The drug release profile was similar to that of Xeljanz XR®, which has an initial lag time owing to its OROS™ formulation; a coating process was performed to obtain a similar drug release profile. The lag time was controlled by adjusting the thickness of the coating layer. Moreover, the extrudate size and compression force during tableting did not significantly affect drug release. In conclusion, the new tofacitinib sustained-release tablet prepared using hot melt extrusion showed a drug release behavior similar to that of Xeljanz XR®.