Melt Flow Research Articles

Influencing mechanism of the active elements on the surface tension of the laser cladding molten pool and the determination of the critical concentration

The addition of active elements during cladding will affect the molten pool flow, and different concentrations have different flow states. In this paper, a numerical model of heat-flow coupling in the ASTM 1045 laser cladding Fe60 process was established and the effects of different concentrations of S, O, and Se elements on the molten pool flow state were calculated and revealed. The results show that there is a critical concentration (CC) when the active element affects the molten pool flow. When the concentration is lower than CC, the flow direction of the melt in the molten pool is from the center to the edge. With the increase in concentration, the flow velocity of the molten pool gradually decreases. When the concentration of active elements reaches CC, the flow direction of the melt changes, but the concentration will make the molten pool flow disorderly appear. The concentration at which the melt flow direction begins to change is called the initial critical concentration (ICC), and the concentration at the end of the change in the melt flow direction (completely reversed) is called the perfect critical concentration (PCC). In the experiment, ICC and PCC intervals are not suitable for concentration selection. When the concentration of active elements exceeds PCC, the flow direction of molten pool does not change. The flow velocity of the molten pool gradually increases with the increase in the active element concentration. The morphology and microstructure of the cladding layer were analyzed with the same technological parameters. The effectiveness of numerical simulation is verified.

Accurate Molar Mass Estimation of Polyolefin Blends Using High Temperature-size Exclusion Chromatography With Triple Detection: Insight Into Molecular Level Mixing of Polypropylene With Various Application Grades of Polyethylene.

In this study, a commercially available polypropylene homopolymer (H-PP) was blended with blow molding polyethylene (PE) grade via melt mixing using a compounding machine. The resulting blends were subjected to high-temperature size exclusion chromatography (SEC) analysis, coupled with infrared-5 (IR-5), viscometer (VISCO), and multi-angle laser light scattering (MALS) detectors. The molecular weight (MW) and MW distributions were investigated using SEC, and the exact blend compositions were evaluated using 13C nuclear magnetic resonance. The molecular-level mixing of the PP/PE blend composition was assessed by comparing the theoretical and measured weight-average MW (Mw) values obtained using different SEC detection modes. The measured average Mw values of different PP/PE blends obtained using VISCO and multi-angle light-scattering detection were found to be in close agreement with predicted blend ratios, compared to the conventional SEC technique (IR-5), with percentage errors ranging from -4.53 to -5.99 and 1.57 to 7.65, respectively. The linear relationship between the melt flow rate (MFR) and Mw was studied to assess the molecular-level mixing behavior of the prepared blends using different SEC detection modes. Furthermore, the SEC methodology was extended to other application grades of PE with varying MFRs to verify the blend mixing behavior with H-PP, and the obtained results are discussed.

Highly Filled Rubber Plastics for Soft Road Surfaces: Effect of a Matrix Composition on the Mechanical Properties

Today, rubber crumb is used as the main component in the compositions for construction of soft road surfaces. This report presents the results of investigations on the mechanical properties of rubber–plastic composites containing 80 and 90 wt % of rubber crumb, based on different polyethylene matrices. It was established that, at high contents of rubber particles, there is no need to control the following characteristics of the matrix polymer to obtain the rubber–plastic composites deformable to at least 150%: the melt flow index, the content of HDPE or LDPE in the mixed matrix. The prospects for using the composites obtained were outlined.

The Effect of Elastomer Content and Annealing on the Physical Properties of Upcycled Polyethylene Terephthalate-Maleated Styrene Ethylene Butylene Styrene Blends for Additive Manufacturing.

In the work presented here, we explore the upcycling of polyethylene terephthalate (PET) that was derived from water bottles. The material was granulated and extruded into a filament compatible with fused filament fabrication (FFF) additive manufacturing platforms. Three iterations of PET combined with a thermoplastic elastomer, styrene ethylene butylene styrene with a maleic anhydride graft (SEBS-g-MA), were made with 5, 10, and 20% by mass elastomer content. The elastomer and specific mass percentages were chosen based on prior successes involving acrylonitrile butadiene styrene (ABS), in which the maleic anhydride graft enabled compatibility between different materials. The rheological properties of PET and the PET/SEBS blends were characterized by the melt flow index and dynamic mechanical analysis. The addition of SEBS-g-MA did not have a significant impact on mechanical properties, as determined by tensile and impact testing, where all test specimens were manufactured by FFF. Delamination of the tensile specimens convoluted the ability to discern differences in the mechanical properties, particularly % elongation. Annealing of the specimens enabled the observation of the effect of elastomer content on the mechanical properties, particularly in the case of impact testing, where the impact strength increased with the increase in SEBS content. However, annealing led to shrinkage of the specimens, detracting from the realized benefits of the thermal process. Scanning electron microscopy of spent tensile specimens revealed that, in the non-annealed condition, SEBS formed nodules that would detach from the PET matrix during the tensile test, indicating that a robust bond was not present. The addition of SEBS-g-MA did allow for shape memory property characterization, where deformation of tensile specimens occurred at room temperature. Specimens from the 20% by mass elastomer content sample group exhibited a shape fixation ratio on the order of 99% and a shape recovery ratio on the order of 80%. This work demonstrates a potential waste reduction strategy to tackle the problem of polymer waste by upcycling discarded plastic into a feedstock material for additive manufacturing with shape memory properties.

Chitosan-polylactic acid composites: from seafood waste to advanced functional materials for 3D printing

The development of functional and sustainable materials for additive manufacturing is a rapidly expanding area of interest. In this context, composite blends of chitosan—including commercial low and medium molecular weight variants, as well as laboratory-extracted chitosan from shrimp head and shell waste—and polylactic acid (PLA) were prepared using extrusion molding. Filament characterization was conducted to explore the effects of chitosan molecular weight and content on the filament properties using melt flow index, tensile testing, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). The morphology of the extruded filaments was analyzed using scanning electron microscopy (SEM). Additionally, the possibility of incorporating a high ratio of metal into the composite filaments without compromising their printability and structural integrity was investigated. The results indicated that certain compositions of chitosan-PLA composite filaments enable the effective incorporation of nickel, highlighting their potential as innovative catalyst supports. The filaments were 3D printed in a molten state, and the resulting specimens were subsequently examined using micro-CT. This approach seeks to create an innovative material from food waste, offering a sustainable and circular solution for transforming seafood waste into advanced functional materials. The successful integration of shrimp waste-derived chitosan into PLA filaments not only enhances the material properties, but also demonstrates the potential for creating high-value products from bio-waste, contributing to environmental sustainability and advancing the field of eco-friendly additive manufacturing. This work highlights the promising application of composite filaments in various industrial sectors, emphasizing their role in promoting a circular economy.

Based on Orthogonal Experimental Analysis: Effects of Formulation Systems on the Mechanical, Heat Resistance, and Aesthetic Properties of High-Gloss Black PMMA/ASA Alloys

High gloss and heat resisting PMMA/ASA is applied in many fields such as automotive materials. There are many researches focusing on single properties but no comprehensive quantitative evaluation. In this work, we used orthogonal experiments and variance methods, along with a custom Python program, to conduct in-depth experimental analysis and provide a comprehensive evaluation of the performance of each component in the material system. The results demonstrate that this analysis method can appropriately assess the enhancements that each functional component contributes to corresponding performances. Additionally, it was observed that the strategy of blending high and low melt flow index PMMA affects the overall performance, as the application of high and low melt flow index PMMA changes the distribution and gradient of the functional components, significantly enhancing performance for certain surface or gradient-sensitive properties.

On secondary recycling of high-density polyethylene with reinforcement of stubble powder by a material extrusion process for construction applications

In the past two decades, several studies have been reported using agricultural waste as reinforcement in thermoplastic matrices for lightweight and tunable mechanical properties. However, the recycling of thermoplastic with reinforcement of agricultural waste has constraints in the form of the volume of recycled material to support the concept of a circular economy. One of the solutions for bulk consumption of such agricultural and thermoplastic waste is its use in construction applications. In the present study, high-density polyethylene (HDPE) was secondary (2°) recycled by reinforcement of stubble waste powder (SWP) through the material extrusion (MEX) process for possible applications in the construction industry. The melt flow index (MFI) investigation suggested the maximum loading of 15% SWP with the recycled HDPE matrix in the present case study. Further, the filament was prepared by using the design of experiment (DoE) with input parameters (heat treatment (pre-heat treatment (PreHT) and post-heat treatment (PostHT), barrel temperature (170–180°C) and screw speed (3–5 RPM) on single screw extruder). The results suggest that the combination of PreHT, 170°C-barrel temperature and 4 RPM screws speed resulted in a maximum Young’s modulus (E) of 1386.57 MPa. The PreHT has promoted the recrystallization of the HDPE-SWP blend, which has significantly increased E. The differential scanning calorimetry (DSC) reveals that the HDPE-SWP composite was more thermally stable after each thermal cycle. In addition, the results of this study were also supported and correlated with the observation of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface profiling and 3D printability with MEX.

STRUCTURAL EVOLUTION OF THE CHEKA PLUTON (SOUTHERN URALS): PETROMAGNETIC STUDIES AND FRACTURE ANALYSIS

The Cheka pluton, located in the Magnitogorsk megazone of the Southern Urals and composed of the alkaline granitoids, is meridionally elongated (1–2)×6.5 km. The fracture and anisotropy of magnetic susceptibility analysis was made on the Cheka pluton for the first time. The study materials comprise fracture measurements and core samples. The fractures were classified as either prototectonic or tectonic using the Stereonet software. The prototectonic fractures were classified into three standard types in accordance with the system proposed by G. Cloos: S, Q, and L. The system of tectonic fractures corresponds to the Riedel model, which confirms the formation of the pluton as a dextral magmatic strike-slip duplex supposed earlier. The analysis of magnetic mineralogy revealed that the most prevalent magnetic mineral is fine- to-medium-grained magnetite. Using the anisotropy of magnetic susceptibility data, the main direction of melt flow during the formation of the pluton was determined to be 36° NE. This direction is in close alignment with the orientation of one of the prototectonic fracture systems, which has a strike azimuth of 39° NE. The constructed complex structure model indicates that the Triassic granitoid plutons of the Magnitogorsk megazone were most likely formed during the right-lateral transpression, associated with a local strike-slip fault-related extension zone. These conditions are generally consistent with the Triassic rifting and dextral strike-slip motion in the Southern Urals.

Mechanical and Flow Properties of Virgin and Recycled Low-Density Polyethylene (LDPE) Blends Using Twin Screw Extrusion

The utilization of recycled materials in the production of plastic products is an environmentally conscious and economically viable approach. This study delves into the mechanical and flow properties of low-density polyethylene (LDPE) blends, comparing virgin low-density polyethylene (vLDPE), recycled low-density polyethylene (rLDPE) and vLDPE/rLDPE blends with different ratio (100/0, 75/25, 50/50, 25/75, 0/100) for the purpose of reprocess into variable high-quality end products with minimal modification. Mechanical properties, such as tensile strength, elongation at break, Young’s modulus, flexural strength, and flexural modulus, were examined to assess the suitability of rLDPE in comparison to its virgin counterpart. Our results demonstrate that vLDPE/rLDPE blend exhibits mechanical properties comparable to those of vLDPE, suggesting its potential as a sustainable alternative for reprocessing. Flow properties, specifically melt flow index (MFI), were also assessed to evaluate the processability of the LDPE blends. The findings reveal that the flow properties of LDPE blends are within an acceptable range for extrusion moulding, indicating that these materials can be effectively processed without major adjustments to manufacturing processes. This research underscores the feasibility of incorporating rLDPE into vLDPE for reprocessing into variable products, offering both economic and environmental advantages. By extending the lifecycle of LDPE materials through recycling, we can contribute to reducing waste and the overall environmental footprint while maintaining the desired mechanical and flow properties for high-quality end products.

Low-Cost Open-Source Melt Flow Index System for Distributed Recycling and Additive Manufacturing.

The increasing adoption of distributed recycling via additive manufacturing (DRAM) has facilitated the revalorization of materials derived from waste streams for additive manufacturing. Recycled materials frequently contain impurities and mixed polymers, which can degrade their properties over multiple cycles. This degradation, particularly in rheological properties, limits their applicability in 3D printing. Consequently, there is a critical need for a tool that enables the rapid assessment of the flowability of these recycled materials. This study presents the design, development, and manufacturing of an open-source melt flow index (MFI) apparatus. The open-source MFI was validated with tests on virgin polylactic acid pellets, shredded recycled poly(ethylene) terephthalate glycol flakes, and high-density polyethylene/poly(ethylene) terephthalate blends to demonstrate the range of polymer types and recyclability. The proposed MFI tool offers a user-friendly and cost-effective solution for evaluating the flow properties of materials from waste streams, thereby enhancing their viability for additive manufacturing applications.

Evaluating Processing Parameter Effects on Polymer Grades and Plastic Coloring: Insights from Experimental Design and Characterization Studies.

Resolving material and processing issues is essential to improving formulations and attaining accurate color matching in blending. Two transparent polycarbonate resins made up the blend: PC1, which made up 33% of the mixture with a Melt Flow Index (MFI) of 25 g/min, and PC2, which made up 67% of the mixture with an MFI of 65 g/min. This study employed data mining and a well-structured experiment using Design of Experiment (DoE) software-8 to investigate the effects of various processing temperatures on identical material formulations. The primary objective was to understand the influence of the operating conditions on the viscosity of a red letdown pigment made of polycarbonate, both with additive (WA) and without additive (WOA). The study analyzed the effects of processing parameters and rheological properties using a co-rotating twin-screw extruder. Rheology, Fourier-Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) were employed to compare results and evaluate their impact on minimizing color discrepancies and improving Single-Pass Color Uniformity.

Suppression of melt flow instabilities by amplifying high-frequency melt waves in laser fusion cutting

High-frequency resonant melt waves locally increase the stability of melt flow and enhance cut flank quality. To amplify these waves along the melt flow, an acoustically tuned cutting nozzle, termed the cutting whistle, generates gas flow oscillations based on a resonant cavity. The nozzle cavity is designed for 6 mm thick sheets, causing the gas flow to oscillate at 15 kHz within the kerf, creating a uniform melt flow with synchronized oscillating melt waves. Performance evaluations on stainless steel sheets show that, compared to a standard conical nozzle, the cutting whistle reduces surface roughness across the entire cutting depth and prevents coarse structures near the upper sheet surface and at the bottom in burr-free cuts.

The effect of assist gas type on nitinol microsecond laser cut edges: a study on the use of oxygen, argon, nitrogen, helium, and compressed air

Abstract Historically, the published literature for laser cutting atomically balanced nickel-titanium alloy (Nitinol) tubular devices assumes slow cut rates with an inert argon assist gas. Herein, a novel application of an exothermic reactive oxygen assist gas was employed during Nitinol laser micromachining, which enabled a 38.1 mm s−1 cut rate, a 4.5-times improvement from traditional argon cutting. Furthermore, this led to the realization of improved cut quality: 2-times less dross, a 2-times lower surface roughness, and a minimal heat-affected zone. Of the tested assist gases (oxygen, argon, nitrogen, helium, and compressed air), oxygen was found to provide the best cut quality, achieving dross-free cuts. Additionally, oxygen was shown to produce a relatively low arithmetic mean average surface roughness of 0.48 μm, when compared to argon at 0.85 μm. A decrease in surface roughness was found to be associated with an increase in cut rate. These findings suggest that assist gas melt flow dynamics has a higher contributing factor than laser pulse energy parameters. In-situ thermographic monitoring of the melt flow during processing demonstrated a clear difference in the melt flow pattern between a reactive oxygen assist gas and inert argon assist gas. Furthermore, with the culmination of nanoindentation analysis and microstructural characterization, it was concluded that long-pulse laser micromachining can produce cuts with negligible microstructural alterations to the bulk material. This study quantitatively demonstrates the benefits observed during laser cutting Nitinol with a reactive oxygen assist gas when compared to previous studies that employ an inert argon assist gas.

Effect of thermoplastic starch/poly(lactic acid) weight fraction on phase morphology and performance of biodegradable blends and their jute fiber composites.

The present work investigates the phase morphology and properties of biodegradable thermoplastic starch (TPS)-poly(lactic acid) (PLA) blends and their jute fiber (JF) biocomposites. The TPS/PLA blends and TPS/PLA/JF composites were fabricated using a twin-screw extruder and then injection molded into the test specimens, varying the TPS/PLA weight fractions (80/20, 60/40, 40/60, and 20/80) while keeping the JF content constant (10wt%). At 80wt% TPS, the TPS/PLA blend showed a co-continuous structure, whereas the remaining blends (20, 40, and 60wt% TPS) exhibited a TPS droplets-PLA matrix structure. The TPS/PLA/JF composites displayed a PLA droplets-TPS matrix structure at 80wt% TPS, a co-continuous structure at 60wt% TPS, and a TPS droplets-PLA matrix structure at 20 and 40wt% TPS. Increasing the proportion of PLA increased the melt flow ability, tensile strength, Young's modulus, storage modulus, thermal stability, and water contact angle of the blends and composites. The addition of jute fibers altered the phase morphology of the blends, enhanced their strength and stiffness, increased PLA nucleation, and improved the TPS-PLA phase compatibility. The blends and composites herein exhibit great potential in developing environmentally friendly injection-molded products, such as stationery, toys, gardening supplies, etc.

Rice Husk Filled PLA/PBAT Composites for Food Containers: Processability, Rheological and Thermal Properties

AbstractThis study explores the potential of using a composite material made of polylactic acid (PLA), polybutylene adipate‐co‐terephthalate (PBAT), and rice husk (RH) as an alternative for food containers. Two blends with 10 wt%–20 wt% of PBAT and four composites with 10 wt%–20 wt% of RH reinforcement are evaluated. The composite is created using an internal mixer and is analyzed using torque vs time mixing curves, melt flow index (MFI), thermogravimetric analysis, and differential scanning calorimetry (DSC). The blends exhibit higher crystallinity and superior mechanical properties compared to composites. Adding RH improves sustainability and decreases costs by utilizing agricultural waste but reduces flexural strength. However, the addition of PBAT increases flexibility, making it suitable for pliable material applications. The composite CO4 with 20 wt% of PBAT and RH demonstrates balanced performance in terms of lower MFI, thermal stability, and flexural strength, making it suitable for food tray applications. Further studies are needed to optimize the mechanical and barrier properties of these composites for specific applications.

Development of Polyurethane Elastomer-Based Bio-Composites Reinforced with Basaltic Pumice

Basaltic pumice has a black or gray appearance due to its iron and magnesium-rich komatiitic tuff composition. Pumice's porous structure allows the production of various polymer-based bio-composite materials for biomedical applications. This study developed bio-composite samples by incorporating basaltic pumice powder at 2.5, 5.0, 7.5, and 10.0 percent concentrations into an elastomeric polyurethane (EPU) matrix. The surface and elemental structure of basaltic pumice particles were investigated using the SEM/energy diffraction X-ray technique. The physical, mechanical, thermal, melt-flow, and morphological properties of bio-composites were studied experimentally. Findings showed a rise in Shore hardness and tensile modulus parameters and declined tensile elongation. According to the thermal study, introducing basaltic pumice resulted in a modest drop in the thermal stability of the EPU and an improvement in stability against mechanical deformations. Pumice loadings raised the melt flow and extrusion torque values of the EPU. The observation of the homogeneously distributed pumice particles in the EPU matrix is used as visual evidence to investigate the highest performance among the composites in the EPU sample with the lowest loading rate of 7.5% pumice. Overall, BP is effective as a reinforcing agent in EPU-based bio-composites at low additive percentages.

The influence of solid-state polycondensation of polyethylene terephthalate on its rheological properties

The influence of solid-state polycondensation conditions on the rheological properties of polyethylene terephthalate was determined. Mathematical models describing the dependence of the melt flow rate of both virgin and recycled polyethylene terephthalate on the time and temperature of the solid-state polycondensation process were developed. A correlation between the melt flow rate and the average molecular weight of polyethylene terephthalate was demonstrated. Experimental studies showed that conducting solid-state polycondensation of recycled polyethylene terephthalate at temperatures ranging from 1300C to 1600C for 3 hours produces polymeric materials with higher molecular weight and, consequently, improved performance properties.

Antibacterial Properties of PCL@45s5 Composite Biomaterial Scaffolds Based on Additive Manufacturing.

This study focuses on the development of polymer-bioglass composite bone scaffolds for the treatment of bone defects. PCL particles and 45s5 bioglass powder were employed as raw materials to fabricate PCL/45s5 composite wires with mass fractions of 5 wt%, 10 wt%, and 20 wt% via the twin-screw extrusion method. A cylindrical porous model was established using 3D modeling software, and a porous composite scaffold was constructed through the melt deposition manufacturing process. The macroscopical characterization of composite stock and composite powder was analyzed. The melt flow rate, water contact angle, elastic modulus, in vitro degradation rate, and antibacterial property of composite scaffold were measured. The experimental results showed that the incorporation of 45s5 bioglass into PCL material gave the composite better antibacterial properties, effectively reduced the flow rate of the material, increased the hydrophobicity of the material, and improved the rigidity and biocompatibility of the PCL material. This study offers initial insights into the use of synthetic bone tissue engineering scaffolds for clinical bone repair treatments.

Fabrication and characterization of a filament for 3D printing from polylactic acid with Cryptostegia grandiflora fiber

Abstract Additive manufacturing (AM), i.e., 3D printing, has seen significant growth in recent years in all industries due to its potential advantages, requiring the polymers that are adapted as for melt flow index (MFI) to this use to have adequate tensile strength as well. Hence, in this work, a novel ligno-cellulosic fiber from Cryptostegia grandiflora (CG) and polylactic acid (PLA) were blended to obtain a filament for AM using a twin screw extruder. To determine the filament’s suitability for the 3D printing process, MFI and thermal degradation were examined. In order to identify the distribution and the effect of CG fiber (CGF) filler on the matrix, the filaments were examined using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). CGF powder distribution was observed in the microstructure of the CGF/PLA composite filament. Due to the high compatibility between PLA and CGF, their blending slightly increased the degradation temperature, though did not lead to any crystallinity loss, and the CGF/PLA filament showed 12.5% better tensile characteristics than the pure PLA filament. Based on their performance, the CGF may represent a suitable and compatible filler to improve the properties of the PLA filament for 3D printing applications.

The Scheil–Brody–Flemings law and interdendritic spacing for steady-state crystallization in the presence of two-phase region and weak melt flow

The Scheil–Brody–Flemings law and interdendritic spacing for steady-state crystallization in the presence of two-phase region and weak melt flow