Thermoplastic Powder Research Articles

Facilitating aqueous powder impregnation for manufacturing thermoplastic composites: A prepreg rig design and process optimisation

This study investigates a novel thermoplastic prepreg rig and method of manufacturing prepregs using aqueous wet powder impregnation. The compact, easily maintained prepreg rig is suitable for rapid prepreg manufacturing in laboratory-scale research. The rig could be used with a wide range of thermoplastic powders and reinforcing fibres. Tests were conducted to study various settings and parameters, including the polymer–carrier ratio, winding speed and fibre tension. The study examined the effectiveness of the liquid carrier in suspending the polymer powder and tested the consistency of the rig in resin pick-up. The findings indicate that a winding speed of 4.2 to 5.7 m/min with a low fibre tension is ideal for producing S2-glass/PAEK prepregs. The amount of polymer pick-up by the fibre tow remained constant throughout the winding for 10, 20, and 30 wt% slurries. However, higher wt% slurry settings resulted in resin agglomeration on the rollers, causing significant fibre breakage.

Microbubble on fiber method to determine the contact angle between steel substrates and highly viscous molten PEKK and PA 6

AbstractDetermining the contact angle between a molten thermoplastic and a solid is important for the processing of thermoplastics and their composites. The well‐known sessile drop method can be used to determine the contact angle of thermoplastics. However, complex instrumental systems are needed due to the high viscosity and high melting point of thermoplastics. Inspired by the captive bubble method, a simple method based on the system of an air bubble on a substrate in the molten thermoplastic was proposed. This system is prepared by melting fibers and thermoplastic powder materials mixtures in between two glass plates using a hot stage. The contact angle of a microbubble in contact with fiber in molten thermoplastic is measured using an optical microscope. The system of a microbubble in molten thermoplastic can easily reach the equilibrium state. Two types of highly viscous thermoplastics in contact with stainless steel fibers are studied and the contact angle is sensitive to both the physicochemical properties of the fiber surface and the type of polymer matrix materials, which demonstrates the applicability of this method. Our proposed method is promising to be further developed into a general method to determine the contact angle between thermoplastics and solid surfaces.

A Comparative Assessment of the Influence of Modification with Thermoplastic Powders on the Residual Compressive Strength of the Carbon Fiber Reinforced Polymers

A Comparative Assessment of the Influence of Modification with Thermoplastic Powders on the Residual Compressive Strength of the Carbon Fiber Reinforced Polymers

Performance optimization of 3D printed polyamide 12 via Multi Jet Fusion: A Taguchi grey relational analysis (TGRA)

The multi jet fusion (MJF) additive manufacturing techniques enable producing different complex geometries quickly with a relatively inexpensive product development process, using a thermoplastic powder, specifically polyamide 12 (PA 12). The multi jet fusion additive manufacturing technology aims to enhance the quality of parts quickly and inexpensively compared to existing 3D printing technologies. In comparison with other polymer printing processes, MJF shows a much faster printing process with exciting potential. However, less studies discussed which input parameters have a significant impact on the printed part. This presented contribution used to participate in solving this issue, and investigates the effect of the two different printing orientations under different strain rates. Specimens were printed using polyamide by ASTM 638 type IV. The design of experiment for this study used Taguchi L8 four-factor design, that consist of two different orientations and four strain rates. This study aims to determine the optimal parameters for printing according to the mechanical properties of the polyamide 12 material using grey relational analysis. The results showed that the optimal results appeared with a 10 mm/min strain rate, and the building orientation was 25°, as the Grey relational grade improved by 0.141% with optimized parameters.

Simulation of Thermoplastic Powder Cold Spraying

The work is devoted to the deposition of composite powder materials by cold spray method. As a spraying material, a thermoplastic compound «WAY» for marking the roadway was used. An asphalt concrete was used as a substrate. As a result of experimental studies, the dependence of the deposition efficiency on the stagnation temperature of the working air in the ejector nozzle was obtained. The ANSYS Fluent package was used for evaluative modeling of the cold spraying process. Gas flow patterns were obtained in the computational domain without particles and taking into account the interaction of the flow with particles. The trajectory of the particles was calculated for various spraying parameters

Strontium Aluminate Compound as Road Line Materials Application

Road line marking are used as a mean of controlling traffic and road user safety. It is very significant on any roads and intersections as they promote road safety. They highlight a harmonious flow of traffic along guided paths of travel. The objectives of this study are to investigate the properties of road line materials and examine the illuminance properties of glow in the dark powder applied in road marking materials. The use of photoluminescent glow-in-the-dark material was tested in the lab for its suitability (luminosity and the glow duration). The methods involved are selection of suitable type of glow in the dark materials, selection of optimum mixing ratio of the glow in the dark powder with thermoplastic powder, and finally analyzed for the properties of the type of the material chosen. The fine granular strontium aluminate compound, SrAl2O4 was selected as the most suitable type of glow in the dark material. Based on the laboratory analysis, the optimum ratio of the glow in the dark material to be used with thermoplastic powder is 55% of total mix volume. The average visible light emission period is in acceptable range of 20 m. This is a suitable distance to implement the road line because of the high visibility on the road during dark or night.

Infiltration behavior of liquid thermosets in thermoplastic powders for additive manufacturing of polymer composite parts in a combined powder bed fusion process

AbstractPolymer‐based multimaterial additive manufacturing (AM) has developed into one of the most promising technologies of recent times. A processing concept was developed in previous studies, which targets the implementation of reactive liquids in a thermoplastic powder‐bed for the creation of multimaterial polymer composite parts. This process aims to be the first AM process of its kind to fully utilize the potentials of both thermoplastic and thermoset polymers simultaneously. A highly important aspect for this process is the investigation of the infiltration behavior of the reactive liquids within the powder bed, since premature or delayed curing of the liquids could lead to deviations from the intended geometry as well as process errors due to material protrusions. This investigation presents an experimental and a mathematical approach to describe and predict the time which a droplet needs to completely infiltrate the powder bed. The results showed, that the experimental setup is viable to observe the droplet height over time at temperatures of up to 105°C and infiltration times below 500 ms. The mathematical model proved to be a powerful approximation to describe the infiltration behavior of a reactive liquid within a thermoplastic powder bed once a material‐specific form factor is determined for each powder material. Through the process of elimination, the independence of the form factor was demonstrated for different powder parameters like the particle size. A theory is presented, which correlates the form factor to the microstructural shape and surface condition of the particles based on SEM images.

New Method for Optimization of Polymer Powder Plasma Treatment for Composite Materials

This paper describes a newly developed testing method for determination of the adhesivity of a film sintered from thermoplastic powder. This method is based on the modified EN 15337 standard. Application of this method enables an effective development of thermoplastic composites with enhanced adhesion between reinforcement and matrix and/or high-quality joints between plastics and dissimilar materials. The proposed method was successfully tested on a series of polyethylene powders treated in the oxygen atmosphere for 0–1200 s. Adhesion to metal and glass substrates in dependence on treatment conditions is described along with powder wettability and X-ray photoelectron spectroscopy analysis. The results show an increase in adhesion to metal by 580% and to glass by 1670% for the longest treatment time, compared to a nontreated powder. Sintering of treated powders revealed a strong influence of treatment time on the melting process. The XPS analysis confirmed the formation of new oxygen groups (C–O, C=O, O–C=O). The method reveals a specific behavior of powders based on treatment conditions, which is crucial for the optimization of plasma treatment for the improved adhesion, applicability of polymer powders, and a development of composite materials.

A Statistical Study of Surface Roughness for Polyamide 12 Parts Produced Using Selective Laser Sintering

Abstract Selective laser sintering (SLS) of thermoplastic powders allows for the creation of parts with complex geometries and functionally robust designs. Based on the principle of selectively fusing regions in a layer-by-layer process, SLS has gained increasing interest as an economical way to supplement small batch production for traditional manufacturing techniques. To introduce SLS parts into functionally demanding applications, it is imperative that they exhibit good surface quality to prevent wear caused by surface friction. Parts produced with SLS, however, typically have a higher surface roughness than those produced through traditional manufacturing techniques. Understanding the relationship between processing parameters and surface quality will allow one to better predict and control surfaces for end-use parts. A design of experiments was formulated to investigate the effects of four process parameters on parts produced across the powder bed: powder type, roller speed, laser power, and scan spacing. To analyze the surface roughness and area ratio of the parts, Focus Variation (FV) technology was implemented. Statistical models were developed to estimate the surface roughness and area ratio of manufactured specimens.

Investigation and Characterization of New Polyimide Powder for Selective Laser Sintering

Selective Laser Sintering (SLS) is close to be accepted as a production technique (Additive Manufacturing). However, one problem limiting employment of SLS for additive manufacturing in a wide-ranging industrial scope is the narrow variety of applicable polymers.In the present work, a thermoplastic semi-crystalline polyimide powder was synthesized.. The shape, size and fractional composition of such powder were investigated by scanning electron microscopy. As a result, polyimide powders with a fairly narrow particle size distribution were formed. On the basis of the polyimide powder, samples were obtained in the form of films by the method of selective laser sintering (SLS). The mechanical properties of these samples were investigated depending on a laser energy density. The morphological study of the films cross-sections showed that monolithic sample having insignificant pores and irregularities in the structure was formed

A novel approach for understanding laser sintering of polymers

Selective laser sintering (LS) of thermoplastic powders allows for the construction of complex parts with higher mechanical properties and durability compared to other additive manufacturing methods. According to the current model of isothermal laser sintering, semi-crystalline thermoplastics need to be processed within a certain temperature range, resulting in the simultaneous presence of the material both in a molten and solid state, which is present during part building. Based on this process model, high cycle times ranging from hours to days are a thought to be a necessity to avoid warpage.In this paper, the limited validity of the model of isothermal laser sintering is shown by various experiments, as ongoing solidification could be detected a few layers below the powder bed surface. The results indicate that crystallization and material solidification is initiated at high temperatures and further progresses throughout part build-up in z-direction. Therefore, a process-adapted material characterization was performed to identify the isothermal crystallization kinetics at processing temperature and to track changes of the material state over time. A dual approach on measuring surface temperatures by infrared thermography and additional thermocouple measurements in z-direction was performed to identify further influences on the material solidification. A model experiment revealed that a few millimeters below the surface, components produced by LS are already solidified. Based on these results, the authors present an enhanced process model of isothermal laser sintering, which considers material solidification in z-direction during part build-up. In addition, a new processing strategy is derived to increase the efficiency of LS processes significantly.

Cold spray deposition of thermoplastic powder for road marking

The work is devoted to the deposition of polymer powder materials by cold spray method. Preliminary experimental results show that although an increase in the working air temperature leads to a noticeable increase in the deposition efficiency of thermoplastic (up to 0.05), it still remains low for cold spray. In the future, the proposed method for applying road marking will allow to obtain a coating with high wear resistance, increased service life, which can be used in various climatic zones in the temperature range from -40 °C to +40 °C, which will allow replacing water and solvent based paints with least service life.

Investigation of thermoplastic powder synergizing polymorphic foam to inhibit coal oxidation at low temperature

An innovative method involving thermoplastic powder synergizing polymorphic foam (TPPF) is proposed to inhibit the self-heating of coal. The TPPF is synthesized by polycaprolactone, polyethylene, sodium silicate solution, sodium dodecyl sulfate, organic acid and water. It exhibits excellent performance in improving the thermal stability of coal, suppressing the coal self-heating process and extinguishing coal fire. This study includes the preparation process of the TPPF, and differential scanning calorimetry measurements, and a polarizing microscope linked to a thermal station, and simultaneous differential thermogravimetric scanning calorimetric analyzer linked to a mass spectrometer and electron paramagnetic resonance. A preparation device of the TPPF with gas as the sole power source and an optimal working pressure of 0.45 MPa was designed. The TPPF could absorb the heat generated by coal self-heating and was fused simultaneously into a colloid to wrap the coal surface to prevent oxygen ingress, resulting in that the initial reaction of carbon free radicals and methyne reacting with oxygen was controlled; the colloid could maintain extra water vapor to form a multilayer at the surface of coal pores and increase the diffusion resistance for the access of oxygen, leading to the peroxygen content decrease; it could also prevent bridge bonds and branched chain breakage to generate new active hydroxyl and alkyl groups, and consume alkoxy and peroxy radicals generated in the coal low-temperature oxidation process by the hydrogen ions. Therefore, The TPPF could decrease the free radicals concentration of coal and cut off the chain reactions of coal self-heating. The TPPT also decomposed large amounts of water, carbon dioxide and a weight of 80.8% non-flammable residue, mainly consisting of Na2CO3 and SiO2, to choke coal self-heating.

Enhancement of mechanical properties of carbon fiber reinforced thermoplastic using colloidal techniques

The composite using thermosetting resin, such as epoxy resin, as matrix was difficult to be recycled. The mechanical properties of the composite materials were deeply involved with the surface adhesion between the raw materials. Our attention was paid to the interfacial properties between the materials in the composite. To enhance the mechanical properties of the thermoplastics reinforced by carbon fibers, the surface adhesion between them should be improved. First, polymer colloids including the same components as the thermoplastic resin were synthesized through the soap-free emulsion polymerization, or using thermoplastic powder and surfactant. These polymer particles were adsorbed on the carbon fibers by electrodeposition. The amount of the adsorbed particles on carbon fibers were controllable with the applied voltage. The surface adhesion between the modified carbon fiber and thermoplastic resin were evaluated to measure the interfacial shear strength thorough the fragmentation test. As a result, interfacial shear strength was enhanced as the amount of the adsorbed particles increased. Using the modified carbon fibers, carbon fiber reinforced thermoplastic was prepared through hot press method with short reaction time. To investigate the mechanical properties of the carbon fiber reinforced thermoplastic, the three-point bending tests were carried out. Because the surface adhesion between carbon fibers and thermoplastic resin, such as poly(methyl methacrylate) or nylon, was improved using the colloidal techniques, the mechanical properties of the carbon fiber reinforced thermoplastic was also enhanced. Thus, the carbon fiber reinforced thermoplastic with high performance was synthesized with the fundamental colloidal techniques. Carbon fiber reinforced thermoplastic is expected to be used as the contractual and recyclable materials in the field of automobiles to realize the sustainable development.

Axalta purchases thermoplastic powder coatings supplier

Axalta purchases thermoplastic powder coatings supplier

Influence of Amphiphilic Plasticizer on Properties of Thermoplastic Starch Films

ABSTRACTThermoplastic starch powders and films were produced by using different combinations of hydrophilic (malic acid and water) and amphiphilic (isoleucine and butyric acid) plasticizers. Spray drying was used to produce thermoplastic starch powder followed by compression molding for the development of films. In all plasticized formulations, the rate of retrogradation was inhibited until the seventh day. The crystallinity and moisture sensitivity of the freshly prepared films were dependent on amphiphilic plasticizer quantity in formulation. Fourier transform infrared spectroscopy and thermogravimetric analysis showed an effective interaction of starch with isoleucine. Isoleucine formulated films showed the highest tensile strength, whereas malic acid-rich films showed better strain values.

Synergistic coal dust control using aqueous solutions of thermoplastic powder and anionic surfactant

For the control of pulverized coal, we propose a dust suppressant by applying a blend of mixed polyethylene oxide (g-PEO) and sodium dodecyl sulfate (SDS). In our experimental study, the thermal characteristics, critical micelle concentration (CMC), wettability and adhesion of the dust suppressant are investigated. It was found that g-PEO had a low fusing temperature and its combustion temperature was close to that of coal, thus, the solution containing g-PEO applied coal dust control did not affect the use of the coal. Based on steady-state fluorescence using pyrene as a fluorescent label, quantitative analysis revealed that the CMCs of g-PEO and SDS were 1 and 20g/L in g-PEO&SDS solution, respectively. The solution containing SDS had the best wettability, but it only had a short-term effect. The solution containing g-PEO showed negligible wetting ability to wet coal dust. The solution containing g-PEO&SDS had better wetting ability and adhesion. Scanning electron microscopy showed that the coal dust covered by g-PEO&SDS on its surface could form a thin layer of armor by holding the particles together after air-drying. It was concluded that the g-PEO&SDS solution containing g-PEO for 1g/L and SDS for 20g/L could suppress coal dust and maintain a long-term effect.

Characteristics of thermoplastic powder in an aqueous foam carrier for inhibiting spontaneous coal combustion

For retarding self-heating of coal, a technique is described by applying a blend of thermoplastic and coal powder (TCP) in a foam carrier. The experimental study includes the behavior, microstructure and evolution of the foam, and the properties of the thermoplastic powder (TP) for inhibiting the spontaneous combustion of coal. It was found that increased TCP concentrations led to decreased foamability, with the detrimental effect on foamability levelling of at concentrations above 30wt.%. The low fusing temperature and high heat of fusion of the TP absorbed the heat generated by the self-heating coal at low temperatures. The liquid fused TP sealed gaps and cracks in the coal dust from oxygen entry. Infrared spectra showed that the TP suppressed alkyl and hydroxyl functional groups in the coal powder (CP) at higher temperatures. It was concluded that TP retarded self-heating in coal, and that the combined thermoplastic and coal powder in a foam carrier has the potential to prevent and control the spontaneous combustion of coal.

Effectiveness of Thermoplastic Powder to Retard Self-Heating and Spontaneous Combustion of Coal

ABSTRACTTo meet the specific requirements for storage and transportation of coal, the use of thermoplastic powder (TP) is proposed for retarding or suppressing self-heating and spontaneous combustion of coal. Thermal behavior analysis of the materials by differential scanning calorimetry and thermal station showed that some of the heat generated during self-heating of coal was removed as TP fused at 39°C. The fused TP blocked pores and cracks in the coal, preventing heat and mass transfer between coal and oxygen. Thermogravimetric and mass spectrometer apparatus determined weight loss and evolved H2, H2O, CH4, CO, CO2, and O2. Absorbed oxygen increased by 0.6 wt% between 175°C and 272°C in coal, but TP/coal powder (TCP) showed no weight increase. Since TP prevented most of the moisture loss in the coal, the weight loss rate of TCP was significantly less than that of coal up to a temperature of 325°C. Mass spectrometry analysis showed that consumed O2 produced H2, CH4, CO, CO2, and H2O at temperatures below 400°C in coal, and above 400°C in TCP. In these experiments, TP retarded or in some cases prevented self-heating of coal at low temperatures, and also retarded coal pyrolysis without affecting the use of the coal.

Study Regarding the Specific Components Performance of Assistant Robots

This paper presents a comparative study regarding the specific components from thermoplastic polymers and ceramic powders for a assistant robot. Experimental research targets the testing of these materials in order to optimize the vertebrae of the robot. The vertebrae are part of a miniature robot (size, weight) for exploration and interventions in a limited space. The simplicity and small size are advantageous for reliability, safety, fast installation and ease of use. Knowing the friction coefficient shows a great importance, particularly in the friction coupling in which movement occurs with low speeds.