The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Highly Viscous Polyamides Made Of Cast Polyamide 6 Recyclates
Cast polyamide 6 is anionically polymerized from ε-caprolactam. Its good properties are mainly caused by the higher molecular weights, compared to standard polyamide 6. Because of sprues and post-processing, a larger amount of scrap is produced. This scrap is typically incinerated without sufficient use of its high quality properties.However, cast polyamide 6 also offers great potential for material recycling, particularly if its high molecular weight can be retained. As cast polyamide decomposes during processing as well, it is necessary to add some additives during compounding. It is the aim of the presented work, to recycle cast polyamide to highly viscous materials. This is done by adding a polyester-modified wax and a carboxylic acid. It can be shown that it is possible to get materials having viscosities of up to two magnitudes higher compared to a typical extrusion polyamide.The high molecular weight of cast polyamide can be maintained or even outperformed. While Young’s modu-lus and tensile strength remain unchanged, the used wax causes some crosslinking of the polyamide and thus also leading to higher impact strength.
Effect Of Foam Density On Elastomeric Nanocomposite Foams Based On Polyisoprene Rubber
Elastomeric polyisoprene rubber nanocomposite foams were prepared via compression molding at different relative foam density 0.4, 0.5, 0.6 and 0.7. Effect of relative foam density on foam morphology and mechanical properties were studied. The results showed that degradation of chemical blowing agent Azodicarbonamide (ADC) and curing of IR compound occurred simultaneously. Light microscopy results showed that increasing foam density from 0.4 to 0.7 gave rise to a decrease in the average cell size from 530µm to 230µm while it led to an increase of cell density from 25 cell/mm3 to 195 cell/mm3. The compression behavior of foams was studied so as to calculate the normalized elastic modulus as a function of the relative density. Several models of cellular materials and polymer composites were used to understand and predict foams’ compression behavior. Results showed that Gibson Ashby model, having pressure parameters, had the best accordance with the experimental data.
Influence Of The Compounding Process Parameters On The Dispersion And Material Properties Of Graphene-Based Pp Composites Using A Twin-Screw Extruder Under Industry Related Conditions
Ideal graphene has excellent mechanical, electrical and thermal properties and is therefore potentially suitable as a functional filler in thermoplastics. Laboratory tests have already shown that very low filler contents are sufficient to achieve a significant improvement of the material properties. However, the investigations carried out so far have been based on experiments on the laboratory scale. These results cannot be transferred to an industrial scale. This is mainly due to the changed geometric conditions as well as the different shear energy inputs and residence times. Therefore, the focus of this work is on the influence of manufacturing conditions on the dispersion and the resulting material properties of graphene-based composites, which are produced by the use of a co-rotating twin screw extruder under near-industrial conditions.The results show that the processing of graphene-based composites in industrial scale is possible. Nevertheless, the effect of graphene on the mechanical properties is less pronounced compared to the properties of graphene-based composites that are produced in laboratory scale, due to a low degree of dispersion. The investigations concerning the influence of the machine parameters throughput, speed, screw configuration and the addition position of the graphene on the properties of graphene-based PP composites demonstrate that the mentioned machine parameters have a significant influence on the process parameters specific mechanical energy input (SME), melt temperature and the residence time of the melt in the twin screw extruder. The quality of the graphene dispersion is generally improved by long residence times and high shear energy inputs, which are achieved by low throughputs and high screw rotation speeds or by the use of a screw configuration with a high energy input. However, the differences in the degree of dispersion shown do not lead to significant differences in the mechanical properties of the nanocomposites. It can be concluded that the residence times and SME are not sufficient to achieve an adequate dispersing quality in the melt mixing process using a twin-screw extruder under near-industrial conditions to achieve significant property improvements.
Effect Of Soft Segments And Nucleation Agents On The Properties Of Thermoplastic Polyurethane Foam
It is known that the properties of thermoplastic polyurethane (TPU) are related to its constituents. Different soft segments, hard segments and chain extenders offer different physical properties. However, very few studies have investigated the effect of the constituents on the properties of TPU foam. In this study, thermoplastic polyurethanes (TPUs) containing different soft segments were synthesized using a pre-polymer method. The samples were foamed, using CO2 as the blowing agent, by one-step batch foaming. The expansion ratio was controlled by varying the foaming temperature (Tf). The role of nucleation agents was also investigated. The shrinkage of the TPU foam was observed by monitoring the foam density. Due to the high diffusivity nature of CO2, significant shrinkage was observed within several hours. In our case, a stable expansion ratio of 4 times was observed.
Open-Cell Foaming Of PP/PTFE Fibrillated Composites
In the study, PP/PTFE composites with different degree of fibrillation are prepared. Crystallization and rheology behavior are investigated. PTFE is easily deformed into fiber during compounding. The presence of PTFE fiber enhances the kinetics of isothermal crystallization of PP. The second modulus plateau at the low ω and a tan δ peak indicate the existence of a three dimensional networks. Extrusion foaming results show a 2 orders increase in cell density and 10-fold decrease in expansion ratio due to addition of PTFE compared to that of PP. With PTFE nanofiber, open-cell content of the composites is increased.
An Applicantion Of Thermoplastic Polyurethane Foaming In Handrail Extrusion
This study investigated an application of making thermoplastic polyurethane (TPU) foam using Expancel® microspheres  as blowing agent in handrail production at EHC Canada, Inc. The optimized Expancel® content was found and all properties (especially the mechanical properties) of the foamed handrail were tested. The results reveal that the current extrusion processing parameters do not need to be changed for producing the new foamed handrails with Expancel® microspheres. All foamed handrails passed mechanical tests. This foaming of handrail material resulted in 14% reduction in use of that TPU material and a 10% saving in its cost.
Flexural Testing Of Pet-Nanofiber And Pp Foamed Composites
In this work, in-situ nanofibrillated PET is used to reinforcing a PP matrix to enhance the final mechanical properties and foam structure quality of an injection molded sample. Although there have been many approaches to reinforce a polymer matrix to increase the melt strength of PP. Long-chain branching, micro- and nano-scale additives and crosslinking approaches each have their own separate drawbacks. However, the use of nanofibrillated composites is a highly efficient and effective method for foam processing. By fibrillating the PET nanofibers (NF) within the PP matrix, fiber breakage from compounding processes can be avoided. To create the PET-NF, PET and PP were first mixed in a twin-screw extruder to disperse the PET as small spherical domains. Afterwards, this blend of spherical PET in PP is melt drawn through a fiber spinning machine to stretch the PET into fibrils with nanoscale diameters and high aspect ratios. As the PET and PP are melt spun together, the nanofibers are well dispersed in the matrix material and ready to be used as a masterbatch. The PET-NF masterbatch is then diluted from 5% to 0.5 and 0.5%, and used in an injection molding (IM) machine. Using foam injection molding (FIM) with mold-opening (MO), foams of various thicknesses and expansion ratios were created with and without the PET. When high-pressure FIM was compared, the foam quality with the PET-NF was higher than the neat PP matrix. The presence of the PET-NF acted as cell nucleating agents which lowered the energy barrier to nucleation by affecting the interfacial energies and inducing local pressure variations. In addition, the PET-NF likely acted as crystal nucleating agents. With use of MO-FIM, the PET-NF showed a three to four magnitude improvement in the cell density. When the flexural properties of the solid and foamed, with and without PET-NF, samples were compared, the PET-NF samples demonstrated higher flexural strength and toughness. Using PET-NF to reinforce the PP matrix increased the both the solid flexural strength and the flexural modulus of the samples by 5 to 10%. However, when HP-FIM is included, the stiffness decreased as toughness increased, which is typical for most foamed samples. Between the foamed PET-NF samples and neat PP, the foamed samples exhibited an increase of up to 40% for both the flexural modulus and strength. When MO-FIM was used, the results showed that the PET-NF increased the flexural modulus between 23 to 46% and the flexural strength between 15 and 25%. This work demonstrated that PET can effectively be fibrillated in a PP matrix. Using injection molding, the PET nanofibers were effective in increasing both the cell density of the final composites. In addition, the PET nanofibers reinforced the PP matrix to increase the flexural strength and modulus.
Theoretical And Experimental Investigation Of Bubble Growth In High-Pressure Foam Injection Molding
We researched a novel simulation strategy that predicts bubble growth phenomenon tailored to high-pressure foam injection molding (HP-FIM) processes. This was done via systematic HP-FIM experiments using a visualization technique. The mathematical model that we developed was based on the well-known “cell model”. To improve the model’s robustness and accuracy, we used the Simha-Somcynsky equation of state for the PS/CO2 mixture, which in turn offers an accurate prediction of the initial bubble radius. Moreover, to capture the fluid flow and mass transport behavior during bubble growth, the transport and rheological properties (that is, its diffusion coefficient, surface tension, viscosity, and relaxation time) that were adopted in this work were functions of the temperature, the pressure, and the gas concentration. In this work, instead of solving the cavity temperature and pressure separately, the temperature and pressure profile inside the cavity were respectively simulated using MoldFlow and experimentally obtained. By inputting the initial gas concentration and the transient pressure and temperature profiles, the proposed model could accurately predict the bubble growth profile under different HP-FIM conditions. The proposed model was validated using experimental data obtained from a series of visualized HP-FIM trials. In both cases, qualitative and good quantitative agreements were achieved between the simulated and the measured bubble growth data.
Protected Biofilm Growth In Macroporous Polyvinilidene Fluoride Carriers For Biological Organic Removal From Municipal Wastewater
Attached growth bioreactor process provides surface area to support the growth and attachment of bacteria, and thereby a means to biologically remove organics from wastewater. In this work, an open-cellular polyvinylidene fluoride (PVDF) foams consisted of macroporous structures were designed and fabricated to promote the efficiency of existing biofilm carriers for wastewater treatment. A manufacturing approach that integrated compression molding and particulate leaching was employed to fabricate the PVDF foams. Different contents of salt were used as leaching agent to fabricate PVDF foams with macroporous structures of different total protected surface areas. Experimental studies were conducted to elucidate the structure-to-performance relationships of these macroporous PVDF carriers in terms of bacteria-to-carrier interaction and organic removal efficiency.
Impact Management And Protection For Playing Surfaces Using Expanded Polyolefin Particle Foam – New Materials And Designs
This paper provides details on the topic of impact management and injury mitigation for playing surfaces, including Football Fields, Soccer Fields, Playgrounds and other playing surfaces both indoors and outdoors and the use of Expanded Polyolefin Particle Foam in their design and construction.The design and construction of sports surfaces plays an important role in playability, performance, injury reduction, and overall impact management and shock mitigation. Expanded Polyolefin Particle foams are being used to fulfill this role. The properties of Expanded Polyolefin Particle Foams allow for designs which take advantage of the isotropic nature of particle (bead) foams, the highly efficient energy management properties, and the ability to manage energy and mitigate impact with a combination of compression, flex and tension. The ability to shape mold the material allows for the most efficient three-dimensional and multi-axis design for energy management. It also allows further performance optimization through changes in geometry and changes in density.This paper will present recent sports surface design innovations and provide case studies vs. competitive technology. Other benefits of Expanded Polyolefin Particle Foam will be presented including 100% recyclability, water-resistance, chemical resistance, long term performance, and the ability to meet the ever increasing rigorous standards for restricted chemicals. This paper will also explore the latest development in the area of soft bead foam technology. New materials beyond the existing Expanded Polypropylene (EPP) such as advanced thermoplastic polyolefins, elastomers, vulcanizates, and polyurethanes are now being used to manufacture expanded particle foam which provide enhanced benefits in the area of energy management and safety. The benefits of these new materials, which include Expanded Thermoplastic Olefins (ETPO), Expanded Thermoplastic Urethanes (ETPU), Expanded Thermoplastic Elastomers (ETPE), Expanded Thermoplastic Vulcanizates (ETPV), and other expanded material blends will also be shown.
Strain Hardening Of Linear Polymer Enhanced By Heat Shrinking Fibers
The strain hardening behavior of polymers has important roles in processing such as foaming, film formation, and fiber spinning. The most common method to enhance strain hardening is to introduce a long-chain branching structure on the backbone of a linear polymer, but this method is costly and challenging to tailor the behavior. We hypothesized that in situ shrinking fibers can increase the strain hardening of linear polymers, and the degree can be efficiently controlled. In this study, we show that heat-activated shrinking fibers compounded in linear polypropylene enhance strain hardening and foamability. Moreover, changing processing conditions, such as temperature, can amplify the degree of enhancement. Rheological measurements and physical foaming tests are shown to support our hypothesis.
A System For Visualizing And Measuring Stress Of Plastic Flows Under Shear Conditions
Shear stress on polymers has been shown to have a strong effect on morphological and thus mechanical properties of the final structure. In this study, an in-situ visualization system was developed to i) visualize crystal nucleation and growth with high spatial and temporal resolutions and ii) have capability to measure the local shear stress and viscosity of a saturated polymer in isolated, simple shear. The system allows for easy control of experimental parameters: applied shear strain, shear strain rate, temperature, heating/cooling rate, pressure, polymer, and saturation gas. An early verification of the shear stress measuring capability was conducted of the This visualization/measuring system provides a reliable way of determining both rheological and optical properties of plastics simulated under dynamic conditions like that of industrial plastic processes.
Ulta-Low Density Foams Of Nanocrystalline Cellulose Reinforced With Polyvinyle Alcohol
Environmentally friendly thermal insulation and energy saving materials are in high demand for buildings, packaging, and other applications. Here, we report ultra-low density composite foam materials that are mainly composed of cellulose, an abundant degradable and recyclable green material. Nanocrystalline cellulose (NCC) was mixed with 0-20 wt.% polyvinyl alcohol (PVA) in an aqueous solution, followed by ice crystallization and freeze drying processes to fabricate the NCC/PVA cellular structures. Ultralight foams with densities as low as 0.026 g.cm-3 (porosities as large as 98.22%) were successfully prepared and their compression and thermal conductivity behaviors were characterized. The results revealed that the compressive stiffness and strength of NCC foams can be significantly enhanced (about an order of magnitude) by the introduction of 20 wt.% PVA as an elasticity enhancer. The thermal conductivity of NCC/PVA foams remained approximately unchanged with an increase in the PVA content and varied only between 0.037 and 0.041 W/mK, a range that is common for commercially available insulation materials. A relatively low thermal conductivity with enhanced mechanical properties of these NCC-based foams offers a potential bio-based material composition for insulation applications.
Enhancing Electromagnetic Shielding Performance Of Pvdf/Mwcnt Composites Through Foaming
The relationship between Electromagnetic interference shielding effectiveness and void fraction of foamed PVDF polymer-based composites with 1 wt% MWCNTs is investigated in this paper. The specimens are prepared through the film casting, compression molding, and batch foaming processes. The composite is advantageous to EMI shielding when the foaming technique is incorporated to reduce weight. It is found out that a 0.62 ~ 0.96 g/cm3 composite achieves an overall EMI SE of 10.5 ~ 25.4 dB in the frequency range of 26 ~ 40 GHz, since increased interfacial surface area from internal gas bubbles contributes to a rise in EMI shielding via absorption.
Resorcinol Formaldehyde Aerogel Nano-Network Structural Assembly And Its Thermal Properties Correlation
When organic aerogel particles are polymerized, a complex three-dimensional (3-D) nano-network is generated. This network is composed of randomly assembled nanoparticles, which form many-branched nanoclusters with unique morphological features. The organic aerogels that result from this process have exceptional properties, which supersede those of the current materials used. We studied the morphological features of an organic aerogel (resorcinol-formaldehyde, RF) and correlated each feature to the sample thermal insulation properties. Several RF aerogels were synthesized with different morphological features and structural assemblies. This was done by changing the catalyst percentages and the void fractions at the polymerization stage. Then, each morphological feature was assessed and categorized using two scales: the macro scale and the micro scale. We found that the macro-features were independent of the catalyst percentages and depended only on the void fractions. However, the micro-features were highly sensitive to any changes during the polymerization process. These changes altered the samples’ three main structural factors: (i) The structural assembly, (ii) The porous structure, and (iii) The fractal parameters. Thus, we characterized and quantified each component within these areas. Then, we assessed the structure’s heat transfer modes and classified them as follows: (i) Solid conductivity through the solid particles, (ii) Gas conductivity through the gas molecules, and (iii) Thermal radiation. We identified the morphological features that governed each mode. For example, the samples’ solid conductivity was highly dependent on the fractal parameters of our structure; that is, the particles’ roughness, the structural complexity, and the structural homogeneity. For those samples with extremely rough particles and a complex structure, the solid conductivity reached the lowest possible point. We also found that the total thermal conductivity was mainly controlled by the micro-morphological features, and that the solid conductivity was the most dominant heat transfer mode.
Modeling Of Cell Growth Effects On The Percolation Threshold Of Rod-Like Fillers In Conductive Polymer Composite Foams
In the conductive polymer composite (CPC) foams, the cell growth can make the rod-like conductive filler rotate and translate due to the force exerted on the polymer matrix. This may influence the percolation threshold of the fillers in CPC foams. This study explores a mathematic model to estimate the effects of cell growth on the percolation threshold.At first, the rod-like filler in the 3-dimensional Cartesian coordinate system was defined using six parameters (i.e., the three coordinates of the filler mid-point, filler length and the two angles between filler and two coordinate planes). The defined filler in 3-dimension was then converted into a 2-dimensional plane using the Euler angels. Then, the filler rotation and translation caused by a single cell growth on that 2-dimensional plane was calculated based on a previously developed mathematical model by our group (Compos Part A, 88). The filler after rotation and translation in 2-dimension was converted into the initial corresponding 3-dimensional Cartesian coordinate system using the Euler angels, again. Finally, with the initial and final filler coordinates before and after cell growth, we can use a Monte Carlo model to simulate the effects of cell growth on the filler percolation threshold.The single-cell-growth effects in a polymer foam containing MWCNTs was calculated as an example. Comparing to the solid system without foaming, in which the MWCNTs percolation threshold was also calculated by the Monte Carlo model, the foam system exhibited lower percolation threshold of MWCNTs. This indicates that foaming may have positive impact on the percolation threshold of conductive fillers in CPC foams.
Poly(Vinylidene Fluoride)/ Graphene Nanoplatelets Composites With Microcellular Structure To Enhance Electromagnetic Shielding Properties
It is well accepted that the microcellular structure can enhance electromagnetic interference shielding (EMI) properties due to the multiple reflection and scattering in the microcells. Moreover, the foams were proved to be the competitive materials owing to the savings of energy and raw materials. In this study, the poly(vinylidene fluoride)/ graphene nanoplatelets (PVDF/GnP) composite foams were successfully prepared through a facile home-made batching foaming avenue. The microcellular structure of PVDF/GnP foams can be tuned by the batching foaming temperature. We can notice that the void fraction of foams firstly increased and then decreased with increasing temperature. In addition, we also investigated the electrical conductivity and electromagnetic shielding properties of PVDF/GnP foams. The results revealed that the electrical conductivity and EMI properties can be effectively monitored, and the PVDF/GnP foam with low void fraction exhibited the high electrical conductivity and EMI properties. The optimal EMI values of PVDF/GnP foams with a thickness of 2.5 mm were 27.4 dB. An analysis of the shielding mechanism showed that the main contribution to the EMI shielding came from the absorption mechanism, and that the EMI shielding could be tuned by controlling the foams’ thickness. Thus, these PVDF/GnP foams could be considered as the high-efficiency EMI materials.
Mining The Value From Oil Sands Tailings Ponds
In Canada, the cleaning cost of 340 billion gallons of oil sands tailings ponds is estimated to be over $27 billion. There is a need for cost-effective technologies for removal and recovery of oil from these ponds. Previously, we reported foams application for absorption and adsorption of crude oil from water. This works aims to develop effective method for foam reuse and oil recovery to improve the benefits of the treatment process. The polyester polyurethane (PESPU) foam with pH-responsive wetting properties and crude oil were used to assess the effectiveness of mechanical compression, pH-swing method, and chemical wash method. The mechanical compression is a simple, environmental friendly, and easy to implement method. This process was effective in recovery of the absorbed oil, where the oil uptake mechanism is reversible superhydrophobic forces and pore filling. However, for adsorbed oil recovery it was less effective. According to pseudo-second-order kinetic model, the oil droplets were adhered to the sponge surface by physical forces. As a result, mechanical forces were weak in shearing-off the thin oil film. Based on pH-responsive wetting property, the oil adsorption was effective at acidic conditions. Therefore, the oil recovery was performed at basic conditions by introducing new “pH-swing” technique. This method produced minimal waste and sustainable, but materials reusability declined to ~70% within three cycles. Finally, chemical wash method was applied to recover the adhered oil from the surface. According to surface chemical displacement principles, a solvent with appreciably low surface tension than the foam and similar molecular structure the crude oil was used to wash the sponge at ambient conditions. Due to enhanced solubility and flowability, the crude oil was readily recovered from the foam surface. The cleaned foam as well exhibited over 99% efficiency over multiple reuses. Our finding show that the foam is a promising solution to remediate detrimental oil sands tailings and for recovery of the residual crude oil from water leading to environmental and economic benefits.
In-Situ PP/PET Nano-Fibrillated Composites: The Effect Of Viscosity Ratio On Fibrillation And Foaming Behavior
It is widely accepted that the manufacturing of high expansion PP foams with fine cell morphology is a challenging task due to the low melt strength and the weak rheological behavior of the linear polypropylene. In this study we present a novel method to manufacture high cell density, large expansion microcellular foam through nano-fibrilation PP/PET composites. Various studies have been conducted to improve the processability of linear PP foams. Until now, the most successful industrial approach is using the branching PP as it expressed the strain hardening response and the increased melt strength behavior. However, the commercial price of branching PP resins are still doubled or even tripled comparing with linear PP resins, which dramatically limits the branching PP’s applications. Inducing chemical cross-linking is proven to be another effective way to improve the melt strength of PP. However, the cross-linked structure causes difficulty in recycling PP resins. Furthermore, the cross-linking reaction is not evenly initiated throughout the matrix rendering non-uniform cell structure in the final foam product. Implementing inorganic/organic filler is another alternative route for enhancing the foamability. PP reinforced with those fillers has higher viscosity and better elasticity at melting state. Nonetheless, the well-recognized challenging issue is to achieve well distribution and dispersion of nano-size fibers inside the polymer matrix. Because of the large surface to volume ratio, the nano-fibers tend to agglomerate. The well-established methods usually requires complex experimental conditions and normally involves dealing with chemical hazards. By implementing nano-fibrillation technology, all above mentioned draw-backs were overcome. The nano-fibrillation technology is used to manufacture polymer-polymer fibril composite in this study. The nano-fibrillation technology can generate high aspect ratio nano-fibrils uniformly dispersed inside the polymer matrix. The processing can be briefly summarized as: (i) blending immiscible polymer matrix (A) and polymer reinforcement (B) to make polymer (B) dispersed in spherical shape (the melting temperature of polymer B should be at least 30oC higher than polymer A); (ii) applying large deformation on the polymer extrudate by either hot stretching or cold stretching; (iii) carefully choosing a temperature between the melting temperature of polymer A and polymer B to melt the composite without damaging the fibril morphology of polymer B. In this study, three kinds of PPs with different viscosity are reinforced with PET nano-fibrils via melt spinning. The study shows that the high viscosity PP is preferred to generate low diameter nano-fibrils (~200 nm) in a wide concentration range; while the diameter of fibrils in low viscosity PP decreased with raising PET concentration. The oscillatory shear behavior is studied by comparing the storage modulus (G’) and phase angle (tanδ) of the non-fibrillated and fibrillated samples. Differential scanning calorimetry and birefringence optical microscope were employed to study the crystallization kinetics of PP/PET fibril composites. The rheological properties and crystallization kinetics were significantly improved with the presence of PET fibrils. Crucially, benefit from the strengthened rheological behavior and crystallization kinetics, the batch foaming of PP/PET nano-fibril composite is able to product a high cell density polymer foams.
Innovative And Useful Characteristic Values For The Pro-Cessing Of Thermosetting Molding Compounds
Due to their complex flow and curing behavior the quality of parts made from thermosetting molding compounds depends to a high degree on the reactive and viscous char-acteristics during their processing. In the study at hand a newly developed test procedure was applied to examine the dependence of these characteristics on the composition of the pourable molding compound, the amount of hard-ener, the present material humidity and the process pa-rameters. Three thermosetting molding compounds were purposefully impinged with high air moisture, the amount of hardener was partially increased and the resulting flow and curing behavior was determined with the implement-ed testing sensors. A distinct dependence of the flow re-sistance and the reaction kinetics on the tool temperature, the amount of hardener and the material moisture was detected. These results are discussed and the potential of the developed testing device is pointed out.
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