Plastic Melt Research Articles

Laser assisted rapid 3D printing of continuous carbon fiber reinforced plastics: Simulation, characterization, and properties

Abstract3D printing of continuous fiber reinforce plastics (CCFRP) with fused deposition modeling is a burgeoning manufacturing method because of its exceptional mechanical properties. Nevertheless, it cannot manufacture parts at high speeds. Using laser heating instead of the traditional resistive heating in 3D printing of CCFRP has the potential to improve printing speed owing to its high heating efficiency. In this article, a process of laser‐assisted rapid 3D printing of CCFRP is proposed. The heating process of CCFRP by laser is analyzed and verified. The linear relation between printing speed and laser power is established. The experiments demonstrate that the printing speed is increased to 30 mm/s with the laser. The mechanical properties of printed parts, though enhanced as the printing speed and laser power increase, are better than those obtained by traditional methods. Scanning electron microscope images and experiments reveal that proper laser power is conducive to the melting of plastics, strengthening interlayer bonding, and reducing voids under roller pressure. Nonetheless, excessive laser power ablates the plastic, resulting in increased voids.

Paving Block from Residue of PS/LDPE/PP Plastic Pyrolysis Mixed with Palm Oil Bottom Ash (POBA)

The residue of plastic mixture pyrolysis can be used for making paving blocks. Fibers in plastics can be used as an adhesive against other materials and can increase the strength of paving blocks. Palm oil bottom ash (POBA) was added to replace the role of cement, which has the same content as cement, i.e., silica (Si). This study aimed to see the effect of palm oil bottom ash and sand added to the residue of plastic mixture pyrolysis (i.e., PS/LDPE/PP) on the quality of paving blocks. The paving block as a test object was made by combining two materials. The residue of plastic mixture pyrolysis and LDPE plastic melt was mixed with a mass ratio of 70:30%, referred to as material I. Furthermore, palm oil bottom ash and sand were mixed with a mass ratio of 100%, 80%, 60%, 40%, and 20%, referred to as material II. The ratio of ingredients I and II used was 1: 1. Testing of the quality of paving blocks includes a compressive strength test and a water absorption test. The test results showed that the ratio of PS/LDPE/PP mixture (50:25:25) had a compressive strength of 104.1 kg/cm2 or 102.08 MPa and the water absorption of 2.4% at the ratio of palm oil bottom ash and sand at 80:20%. Adding palm oil bottom ash can reduce the paving block’s compressive strength, and the residue’s LDPE content can affect water absorption because of its chemical structure properties. Therefore, a reduction in the amount of LDPE residue is needed to obtain optimal water absorption values in paving blocks and add palm oil bottom ash. Based on this compressive strength in this study and SNI 03-0691-1996, these paving blocks can be used for gardens.

Wear Behavior of Roller‐Burnished High Interstitial Austenitic Stainless Steel Parts in Glass‐Reinforced Plastic Melt

Herein this investigation, profiled high interstitial austenitic stainless steel parts are burnished on a profile‐rolling machine, and afterward, the wear behavior is analyzed in a melt of glass‐reinforced polypropylene. Wear and corrosion resistance are significant properties of steel parts in the plastics and food industries. The high work‐hardening ability of high interstitial austenitic stainless steel enables burnishing parts with a significant local hardness to increase up to maximum values of ≈600 HV 1. Wear tests on a recently developed test stand reveal that the burnished austenitic stainless steel surface performs similarly to a nitrided surface of the standard nitriding steel 31CrMoV9 + QT with a hardness of ≈830 HV 0.5. Regarding the given advantage of corrosion resistance, it is concluded that roller burnishing supports the applicability of high interstitial austenitic stainless steel in plastics and food industries.

Microwave assisted heating of plastic waste: Effect of plastic/susceptor (SiC) contacting patterns

Plastic accumulation is a growing sustainability challenge. Most plastics are thermally inert at room temperature, requiring high temperatures for depolymerization. In the quest for developing sustainable plastic upcycling, we investigate silicon carbide (SiC) as microwave absorbing susceptors for reaching depolymerization temperatures. We utilize three SiC topologies – particles, hot-pressed plastic films containing SiC particles, and monoliths. SiC particles of >0.5 mm in diameter can provide heating rates approaching ∼200 °C/min at modest powers. Still, physically mixed plastic-susceptor beds suffer from density differences, causing non-uniform contact during plastic softening and melting. Hot-pressed plastic films containing SiC particles allow uniform plastic-susceptor contact but suffer from slow heating as only a single layer of susceptors exists between polymer layers. SiC monoliths mitigate these challenges by preferentially dissipating the microwaves and rapidly heating the plastics independently of polymeric properties.

Insight into crosslinked chitosan/soy protein isolate /PVA plastics by revealing its structure, physicochemical properties, and biodegradability

Biodegradable plastics are attracting attention for their excellent performance and eco-friendliness. In this study, various ratios of cross-linked chitosan/soybean protein isolate (SPI)/PVA ternary hybrid plastics were prepared by casting, and their structures and physicochemical properties were characterized. Due to hydrogen bonding, FT-IR and XRD results indicated good compatibility between the hybrid plastics. The hybrid plastics surface and cross-section were smoother and evener with few cracks and small free particles at chitosan to SPI ratios of 1:3 and 1:1. AFM results further verified that the relative roughness of the hybrid plastic was lower. In addition, the light transmission and water absorption gradually decreased. Also, with increasing the ratio of chitosan and SPI, the hybrid plastic thermal properties, e.g., crystallization temperature, crystallization enthalpy, melting temperature and melting enthalpy were enhanced. Moreover, blended plastics chroma values exhibited differences under various ratios. Also, the ratio increases of chitosan and SPI improved the plastics' tensile strength and elastic modulus and reduced the elongation at break. Furthermore, the hybrid plastics after soil burial possessed more pores and cracks, implying better degradability. The results obtained in this study can help expand the application and fabrication of crop-based biomacromolecules to meet various packaging requirements such as water resistance, excellent bearing capacity, and favor biodegradability. • Adding chitosan and SPI can reduce plastic surface roughness by promoting compatibility. • Hybrid plastic exhibits superior water resistance compared to pure PVA . • The addition of chitosan and SPI enhances the mechanical properties of hybrid plastics. • After soil burial, the hybrid plastic exhibited desirable degradability.

Static Mixers Producible by Additive Manufacturing: Novel Rapid Automatic Optimisation and Practical Evaluation.

In the extrusion of plastics, the thermal and material homogeneity of the plastic melt at the die entry are of high importance for the extrudate quality. While static mixers are widely used to improve the melt homogeneity, previous attempts at optimisation for reduced pressure loss and improved mixing had to be performed by hand and human experience, limiting the degrees of freedom and efficiency. A new automatic optimisation method based on the open source software OpenFOAM was developed. Using immersed boundary methods, new target functions in the pre-existing routine adjointShapeOptimizationFoam and an additional algorithm checking the suitability for additive manufacturing and fixing the geometry during run-time is presented. The new algorithm is used to optimise an existing static mixer based on an X-type geometry with integrated oil channels, maximising the heat exchange between oil and melt. Based on the results of these simulative optimisations, the best candidates were manufactured using selective laser melting and experimental trials were run. Experimental validation shows that with our optimisation algorithm, a pressure loss reduction of 10% could be achieved. The core melt temperature was reduced by 6 ∘C, improving the thermal homogenisation as well. While the main advantage of this method is the rapid optimisation taking the operating point into account, the trials also showed positive results in off-design operating points. This allows the low-cost design and manufacture of individualised static mixers.

Study on the Sorting Process on the Basis of the Effect of Shrinkage and Melting of Plastics and Its Impact on Further Processing of the Materials

Study on the Sorting Process on the Basis of the Effect of Shrinkage and Melting of Plastics and Its Impact on Further Processing of the Materials

Flashpoint and burning of thin molten plastic pool above hot boundary

The melting and dripping of burning thermoplastics can cause a new ignition and form a plastic pool fire, resulting in a significant fire risk. This work investigates the burning dynamics of polyethylene (PE) vs polypropylene (PP) pools fully melted at 380–410 °C on a hot plate with a controlled area and initial temperature. For PE, three burning patterns are observed and defined under different bottom boundary temperatures. When the boundary temperature is lower than the melting point of thermoplastic, burning Pattern I (near-limit flame) appears shortly and extinguishes quickly. Above the melting point of PE, the flame becomes stronger and can last for the longest period before quenching (Pattern II: transitional flame). PP does not have this transitional-flame stage due to a higher melting point and lower pyrolysis point. When the plastic pool temperature exceeds its flashpoint of about 300 °C (∼60 °C below its pyrolysis point), the flame becomes intense and quickly burns out the molten pool (Pattern III: intensive flame). The burning processes of molten thermoplastics show a clear difference from the burning of ethanol and paraffin wax. This study promotes the understanding of the melting and burning of plastics in real fire scenarios and helps quantify the hazards of dripping and flooring fires.

Design of Deep Eutectic Systems: Plastic Crystalline Materials as Constituents.

Deep eutectic solvents (DESs) are a class of green and tunable solvents that can be formed by mixing constituents having very low melting entropies and enthalpies. As types of materials that meet these requirements, plastic crystalline materials (PCs) with highly symmetrical and disordered crystal structures can be envisaged as promising DES constituents. In this work, three PCs, namely, neopentyl alcohol, pivalic acid, and neopentyl glycol, were studied as DES constituents. The solid–plastic transitions and melting properties of the pure PCs were studied using differential scanning calorimetry. The solid–liquid equilibrium phase diagrams of four eutectic systems containing the three PCs, i.e., L-menthol/neopentyl alcohol, L-menthol/pivalic acid, L-menthol/neopentyl glycol, and choline chloride/neopentyl glycol, were measured. Despite showing near-ideal behavior, the four studied eutectic systems exhibited depressions at the eutectic points, relative to the melting temperatures of the pure constituents, that were similar to or even larger than those of strongly nonideal eutectic systems. These findings highlight that a DES can be formed when PCs are used as constituents, even if the eutectic system is ideal.

A Combined Thermal Spallation and Melting Technology by Plasma Jet for Deep and Hard Rock Reservoirs

Summary With the increasing demand for oil, gas, and geothermal resources worldwide, the efficient and economical construction of wells in deep and hard rocks has become very important, but conventional mechanical drilling technology cannot achieve this. In this paper, a new noncontact combined thermal spallation and melting technology by plasma jet is proposed. This technology can excavate rock materials by disintegrating brittle rocks into small fragments and melting plastic rock. Especially for hard granite, this method exhibits high rock removal efficiency with low specific energy. Furthermore, the plasma bit is not in contact with the rock, thus avoiding bit wear. A thermal spallation and melting experiment system is established, and laboratory tests are conducted. The influence of plasma current, plasma gas flow rate, confining pressure, and the types of rock-on-rock removal efficiency and specific energy are also researched. Results show that this novel technology can efficiently remove hard rocks, and hard granite is more likely to be removed under confining pressure than under the absence of confining pressure, indicating the feasibility of accessing geothermal, oil, and gas resources from deep and hard rock formations.

Utilization of Plastic Waste as Paver Block, Economic Potential, and Environmental Impact

One of the main factors that cause environmental damage in Indonesia is waste. Reducing waste by burning it directly without an incinerator will cause air pollution for the environment. CO2 is a substance produced by a complete combustion process. The amount of waste produced by Bandung Regency reaches 1,480.1 tons/day, with 20% of the waste being plastic waste. One way to utilize plastic waste is to recycle it into materials to produce paver blocks. Producing paver blocks requires a series of machines, such as crushing machines, plastic melting machines, and pressing machines. Plastic waste that has been sorted is put into a chopping machine and cut into 10 mm pieces. The plastic that has been cut is then melted down and printed, then re-pressed with a press machine. The type of plastic used in this research is polypropylene, with a melting point of 160-170°C. The size of the paver block produced is compatible with the market size. During the production of paver blocks, the CO2 concentration was monitored to see the effect of resin melting. In the analysis of paver blocks' economic potential, we found that the production cost using plastic waste is relatively expensive compared to conventional paver blocks. However, this type of paver block is not harmful to the environment. The results of this study indicate that plastic waste paver blocks can be used as paver block materials because they have quite an impact on the environment, although their economic value cannot compete with conventional paver blocks.

Analysis of Melt Front Behavior of a Light Guiding Plate during the Filling Phase of Micro-Injection Molding

When the size of a liquid crystal display (LCD) increases, the light guiding plate (LGP) as the main part of the LCD must adopt a wedge-shaped plate to reduce its weight (the thickness of the LGP decreases because of this) and guide the light to the LCD screen. Micro-injection molding (MIM) is commonly used to manufacture LGPs. During the filling phase of MIM, the entire entering polymer melt front of the LGP should reach the end of the mold cavity at the same time. In this way, there will be no shrinkage or warpage of the LGP in its subsequent application, but it is difficult for the wedge-shaped LGP to meet these requirements. Therefore, the authors hoped to investigate MIM process parameters to change this situation. Otherwise, the LGP is easily deformed during the manufacturing process. Flow characteristics of LGPs were investigated during the filling phase of MIM in this study. Experimental and 3D numerical simulations were used to analyze the hysteresis, i.e., the advance of the polymer melt front of the LGP in MIM. Study results showed that a low injection speed caused a hysteresis effect of the plastic melt front, the solution was to increase the injection speed to improve the situation and an injection speed of 10 cm/s could achieve uniformity of the melt front in MIM. The research results showed that the filling situation of the LGP of MIM in the experiment was very close to that of the 3D numerical simulation.

A 3D Printer in the Lab: Not Only a Toy.

Although 3D printers are becoming more common in households, they are still under‐represented in many laboratories worldwide and regarded as toys rather than as laboratory equipment. This short review wants to change this conservative point of view. This mini‐review focuses on fused deposition modeling printers and what happens after acquiring your first 3D printer. In short, these printers melt plastic filament and deposit it layer by layer to create the final object. They are getting cheaper and easier to use, and nowadays it is not difficult to find good 3D printers for less than €500. At such a price, a 3D printer is one, if not the most, versatile piece of equipment you can have in a laboratory.

The influence of laser etching biomimicking configuration on the strength of metal-plastic connection

This study uses a laser to etch biomimicking locking patterns on the surface of 304 stainless steel to strengthen the connection between metal-plastic products. Under heat and pressure from the device, the plastic melts into the pattern and coalesces it, while the burrs formed from the etching process lock the joint of the metal-plastic. Three biomimicking configurations, honeycomb, leaf vein, and dragonfly head-and-neck hair interlocking, are studied. As shear strength determines the connection strength, we simulate the tensile-shearing process of stainless steel and plastic connectors of the three biomimicking configurations on ABAQUS, and predict the effects of the configurations on their connection strength. Experiments show that the plastic and metal are effectively connected at a heating temperature of 400 °C and a pressure of 70 kN. When the burr rate is 7.66% and the coverage rate is 29.4 ± 0.5%, the three biomimicking connectors break at the plastic base material, and the dragonfly head-and-neck hair interlocking configuration can withstand a shear force of 942 ± 9.23 N.

Analysis of hypervelocity impacts: the tungsten case

The atomistic mechanisms of damage initiation during high velocity (v up to 9 km s−1, kinetic energies up to 200 keV) impacts of W projectiles on a W surface have been investigated using parallel molecular-dynamics simulations involving large samples (up to 40 million atoms). Various aspects of the high velocity impacts, where the projectile and part of the target material undergo massive plastic deformation, breakup, melting, and vaporization, are analyzed. Different stages of the penetration process have been identified through a detailed examination of implantation, crater size and volume, sputtered atoms, and dislocations created by the impacts. The crater volume increases linearly with the kinetic energy for a given impactor; and the total dislocation length (TDL) increases with the kinetic energy but depends on the size of the impactor. We found that the TDL does not depend on the used interatomic potential. The results are rationalized based on the physical properties of bcc W.

Measurement of material degradation in dependence of shear rate, temperature, and residence time

AbstractDuring processing, plastics are frequently exposed to high stresses. These include, above all, shear and temperature within the scope of the residence time of the manufacturing process in order to achieve a homogeneous plastic melt for further processing. The stress of the manufacturing process can lead to molecular degradation, which can have a negative effect on the product properties. Since it makes sense to take molecular degradation into account for many processes, a test stand for material characterization was designed and a regression equation was derived for the mathematical description of the degradation behavior. With the help of this regression equation, a prediction of the expected material degradation can be made, provided that the shear rate, the temperature and the associated residence time are known.

Investigation of Relaxation Time on Viscoelastic Two‐Dimensional Flow Characteristics Using FreeFem++

Viscoelastic fluid flow models have shown promising scope in modeling the behavior of many industrial materials such as polymeric materials, microfluidics, biological liquids, gels, plastic melts, and geomaterials. The relaxation time in these models is of great physical significance. In this article, we study the impact of relaxation time on the viscoelastic flow characteristics in a two‐dimensional baffled cavity. To the best of authors’ knowledge, relaxation time impact on the chosen flow characteristics in the present context has not been studied and presented in the literature before. The constitutive theory of upper convected Maxwell viscoelastic flow incorporating the viscosity ad relaxation time is taken into consideration. To this account, the flow governing PDEs are derived, and an unsteady variational numerical approach based on classical variational setting is presented. A numerical algorithm based on characteristic Galerkin finite elements method is designed and implemented using the programming language FreeFem++. Computations are carried out and drag and lift forces along with other parameters of interests are calculated. Impact of relaxation time on these flow characteristics are studied and analyzed. The relaxation time Rf is assumed to be in the range of 0 ≤ Rf ≤ 1 × 10 − 3. The flow simulations are carried out for large Reynolds number in the range of 200 ≤ Re ≤ 5000. In addition to the application of FreeFem++, some new and interesting features of the flow characteristics are presented and discussed.

Optimization of process parameters in rapid heat cycle molding using heater system

Plastic injection molding (PIM) is a manufacturing technology to plastic products. In PIM, weldline that affects the strength and surface quality of products, and it is then important to determine the optimal process parameters for the weldline reduction. Rapid heat cycle molding (RHCM) is an attracted PIM technology for weldline reduction that by heating up the mold temperature, the melt plastic is smoothly flowed into the die cavity and consequently the weldline is well reduced. In RHCM, since various heating systems are adopted but which have problem that long cycle time. In this paper, to quickly heat up the mold temperature, a heater system is newly introduced and the process parameters in the RHCM using heater system are optimized. A multi-objective optimization for minimizing both weldline and cycle time is considered, and the ratio of mold temperature to injection time is maximized for the weldline reduction, whereas the cycle time is minimized for high productivity. Sequential approximate optimization that the response surface is repeatedly constructed and optimized is adopted for the design optimization, and the pareto-frontier is identified. Based on the numerical result, the experiment is also conducted to examine the validity of the proposed RHCM.

Hypervelocity impact behavior of projectile penetration on spacecraft structure: A review

Spacecraft structure has been protected against the space debris impact by using a bumper plate and main plate. When the debris impacts a thin bumper plate at hypervelocity, debris clouds form and the bumper cause the fragment to shatter and reduces the fragment's ability to penetrate the main structure. The size of the hole in the bumper plate indicates the level of damage to the primary structure. The projectile material's mass in the cloud creates a considerable ballistic threat to the main structure. Various stages of the penetration process have been discussed. The empirical and approximate theoretical formulations created to characterize many features of hypervelocity impact when the projectile and some of the target materials undergo enormous plastic deformation, breakdown, melting, or vaporization are reviewed. For the numerical simulation of hypervelocity impact of space debris on spacecraft structure, Johnson-Cook material and failure model along with Mie-Gruneisen equation of state are used. For the hypervelocity impact experiment, a two-stage light gas gun is mostly preferred.

Development of Leather Cutting Board from Plastic Waste

Cutting is the process in which goods or garment material are cut and converted into pattern shapes of the goods or garment components. There are two methods of Leather cutting, which are hand cutting and machine cutting. Hand cutting is done with the use of hand knife, cutting board and cutting patterns. Machine cutting can be done using semi-automatic cutting machines or fully-automatic cutting machines. Currently, in Ethiopia, different local and foreign investors are participating in leather products manufacturing. Most of the leather product manufacturing industry and some Small and Medium enterprise’s (SME’s) in the country are using leather cutting machines in order to cut leather goods or garment parts. Most of the industry and SMEs are using imported cutting board made of plastics and rubbers. However, these cutting boards are expensive.
 
 This research aimed at developing a cutting board made from HDPE (High-Density Polyethylene) plastic waste as main material, calcium carbonate as a filler and glass fiber as a reinforcing material. Primary and secondary data gathering techniques were applied simultaneously. Primary data were collected through interview and field observation. Secondary data was gathered by reviewing different literature. The cutting board developed through collecting HDPE plastic waste, washing, shredding and melting the shredded plastic with filler and reinforcing material. The melted plastic poured in to cutting board mold and cooled. The developed cutting board was compared with HDPE cutting board available in the local market. The developed board showed relative compression and hardness properties with the HDPE cutting board available in the market. In the cost analysis, the developed cutting board is cheaper than the cutting board which available in the market. However, the cutting board in the market has better surface texture and quality than the developed cutting board. Melting HDPE plastic waste using metal or clay cooking pots and charcoal fire is a tedious task and smoke from the fire will cause human health problem and will affect environment. Consequently, manual plastic melting method is not feasible for mass production, because it is difficult to control the amount of heat (charcoal fire) during melting process. Based on this the authors recommend using machine based plastic melting and molding during HDPE and related plastic recycling.