Thermoplastic Characteristics Research Articles

Melt processing of chemically modified cellulosic fibres with only water as plasticiser: Effects of moisture content and processing temperature

To replace petroleum-derived polymers with cellulose fibres, it is desirable to have the option of melt processing. However, upon heating, cellulose degradation typically starts before the material reaches its softening temperature. Alternatives to plastics should also, ideally, be recyclable via existing recycling streams. Here, we address the problem of melt processing cellulose as fibres while preserving recyclability. Native cellulose fibres were partially modified to dialcohol cellulose to impart thermoplastic characteristics. We demonstrate melt processing of these modified fibres with only water as plasticiser. Processability was investigated at selected processing temperatures and initial moisture content by monitoring the axial force of the extruder screws as a rheological indicator. The effects on molecular structure, fibre morphology and material properties were characterised by NMR spectroscopy, microscopy, tensile testing, fibre morphology analysis and X-ray diffraction. When comparing the melt-processed extrudate with handsheets, the already exceptional ductility was further increased. Moderate losses in tensile strength and stiffness were observed and are attributable loss of crystallinity and fibre shortening. This is the first report of strong and durable extrudates using cellulosic fibres as the only feedstock. Finally, the potential for recycling the processed material with unmodified fibres by paper recycling procedures was demonstrated.

Synergistic effect of Polyvinyl Acetate (PVA) and Enzyme-Induced Carbonate Precipitation (EICP) on the mechanical properties of natural sands

Effective enhancement of the mechanical properties of cohesionless soils is crucial for diverse geotechnical applications, given their inherent vulnerability to load-induced failure due to the absence of inter-particle bonding. Soil failures pose significant risks to both human lives and infrastructure, necessitating the development of environmentally friendly soil improvement methods. Conventional techniques often entail invasive processes and substantial carbon emissions. In response, contemporary approaches seek to minimize environmental impact while preserving organic material characteristics. This study investigates the synergistic effect of polyvinyl acetate (PVA) and enzyme-induced carbonate precipitation (EICP) treatment for enhancing the mechanical properties of cohesionless natural sands. Beach and river sands were treated with varying proportions of PVA in conjunction with an optimized EICP solution for yielding the best results. Unconfined compressive strength (UCS) tests were conducted at 7, 14, and 28-day curing intervals to assess the performance of the soil-polymer-EICP composites (SPEC). The results demonstrated substantial improvements in compressive strength and elastic modulus with increasing PVA content. For beach sand, after 7 days of heat curing, the peak strength increased from 0.89 MPa to 11.07 MPa for composites with 1% and 11% PVA, respectively. Similarly, for river sand, the peak strength increased from 0.87 MPa to 8.96 MPa under the same conditions. The findings also highlighted the softening behavior induced by PVA with heat curing over the period. This softening phenomenon was attributed to the thermo-plastic characteristics of the polymer film induced by temperature conditions.

Catalyst-Free α-Acetyl Cinnamate/Acetoacetate Exchange to Enable High Creep-Resistant Vitrimers.

Vitrimers represent an emerging class of polymeric materials that combine the desirable characteristics of both thermoplastics and thermosets achieved through the design of dynamic covalent bonds within the polymer networks. However, these materials are prone to creep due to the inherent instability of dynamic covalent bonds. Consequently, there are pressing demands for the development of robust and stable dynamic covalent chemistries. Here, we report a catalyst-free α-acetyl cinnamate/acetoacetate (α-AC/A) exchange reaction to develop vitrimers with remarkable creep resistance. Small-molecule model studies revealed that the α-AC/A exchange occurred at temperatures above 140 °C in bulk, whereas at 120 °C, this reaction was absent. For demonstration in the case of polymers, copolymers derived from common vinyl monomers were crosslinked with terephthalaldehyde to produce α-AC/A vitrimers with tunable thermal and mechanical performance. All resulting α-AC/A vitrimers exhibited high stability, especially in terms of creep resistance at 120 °C, while retaining commendable reprocessability when subjected to high temperatures. This work showcases the α-AC/A exchange reaction as a novel and robust dynamic covalent chemistry capable of imparting both reprocessability and high stability to cross-linked networks.

Catalyst‐Free α‐Acetyl Cinnamate/Acetoacetate Exchange to Enable High Creep‐Resistant Vitrimers

AbstractVitrimers represent an emerging class of polymeric materials that combine the desirable characteristics of both thermoplastics and thermosets achieved through the design of dynamic covalent bonds within the polymer networks. However, these materials are prone to creep due to the inherent instability of dynamic covalent bonds. Consequently, there are pressing demands for the development of robust and stable dynamic covalent chemistries. Here, we report a catalyst‐free α‐acetyl cinnamate/acetoacetate (α‐AC/A) exchange reaction to develop vitrimers with remarkable creep resistance. Small‐molecule model studies revealed that the α‐AC/A exchange occurred at temperatures above 140 °C in bulk, whereas at 120 °C, this reaction was absent. For demonstration in the case of polymers, copolymers derived from common vinyl monomers were crosslinked with terephthalaldehyde to produce α‐AC/A vitrimers with tunable thermal and mechanical performance. All resulting α‐AC/A vitrimers exhibited high stability, especially in terms of creep resistance at 120 °C, while retaining commendable reprocessability when subjected to high temperatures. This work showcases the α‐AC/A exchange reaction as a novel and robust dynamic covalent chemistry capable of imparting both reprocessability and high stability to cross‐linked networks.

Manipulating the Properties of Polymer Vitrimer Nanocomposites by Designing Dual Dynamic Covalent Bonds.

Polymer vitrimer is a novel material that contains dynamic covalent bonds (DCBs) allowing it to combine the desirable characteristics of both thermoplastics and thermosets. Similar to the traditional polymer nanocomposites, introducing nanoparticles into polymer vitrimer is also an effective strategy to further enhance its properties. However, a comprehensive understanding of matrix and interfacial bond exchange reactions (BERs) to tailor the properties of polymer vitrimer nanocomposites (PVNs) is still lacking. Herein, we utilized coarse-grained molecular dynamics simulations to investigate model PVNs in which there are two different kinds of DCBs in the vitrimer matrix and at the interface. Our results show that the normalized bond autocorrelation function (Csw) confirms the independence of BERs in the vitrimer matrix and in the interface. By varying the bond swap energy barrier () in the matrix or in the interface , or in both , a maximum mechanical property is observed at the moderate value of , , or. Meanwhile, the effect of on the stress relaxation and the bond orientation as a function of the time under a fixed strain is well probed, which both decay more slowly at greater . We simulated the tension-recovery curve to examine the effect of on the hysteresis loss and permanent deformation of PVNs, finding an optimal value to achieve its minimum energy dissipation and maximum recovery ratio. Lastly, we investigated the efficiency of self-healing by building and removing walls from the system. Interestingly, a maximum self-healing efficiency of the stress-strain behavior is observed at moderate . Overall, this study provides valuable insights into the relationship between the structure and properties of PVNs, offering implications for the manipulation of their mechanical properties and enhancement of their self-healing capabilities.

Spectroscopic Investigation of Li3PS4-LiI Sulfide-Based Glass-Ceramic Solid Electrolytes after Moisture Exposure

Sulfide-based solid electrolytes (SEs) have been extensively studied because of their high lithium-ion conductivities. Among the solid electrolytes, glass or glass-ceramic SEs have suitable thermoplastic characteristics for battery manufacturing processes. However, sulfide-based SEs react strongly with moisture, resulting in toxic H2S gas generation and reduced lithium-ion conductivity. Although the effects of moisture exposure on sulfide-based SEs have been investigated by some researchers, related studies are scarce and further research is required. In this study, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were performed to investigate the structural changes in a glass-ceramic sulfide-based SE, viz., Li3PS4-0.2LiI before and after exposure to moisture, focusing on the changes in the surface chemical species, adsorbed H2O, and related species. In addition, SE samples exposed to moist air were subjected to recovery treatment by vacuum heating. XPS and DRIFTS analyses revealed that the main reason for the decrease in the lithium-ion conductivity of the glass-ceramic SE after moisture exposure is the adsorption of water onto the SE surface and/or its hydration. In particular, the H2O layer adsorbed to the SE surface physically and/or chemically decreases the lithium-ion conductivity at the grain boundaries (i.e., SE/SE interface), although the bulk conduction is maintained.

Mechanical and Tribological Performances of Thermoplastic Polymers Reinforced with Glass Fibres at Variable Fibre Volume Fractions.

High wear rates and frictional coefficients have always been the primary reasons for limiting the service life of critical elements such as pumps, couplings, bushings, bearings and gears. The premature and erratic failures are costing the industries extensive amounts of money every year. Additionally, under severe service conditions, the wear resistance requirements are higher, which greatly hinders the application of neat thermoplastics in different sectors. Hence, it is vital to enhance the tribological characteristics of thermoplastics. The mechanical and tribological properties of Polyamide 6, Thermoplastic Polyurethane, and glass fibre reinforced (GFR) Polyadmide 6 Composites of variable fibre volume fractions were investigated. Pin specimens of Polyamide 6 reinforced with (25%, 33%, and 50%) by volume of fibres were fabricated by an injection moulding process. The specimens were tested for tensile, compression, hardness, and wear under dry abrasive conditions using a pin-on-disc setup. Furthermore, the samples were scanned using micro-computed tomography (micro-CT), and the worn-out samples were analysed using field emission scanning electron microscopy. The experimental results showed that the fibre volume fraction was inversely proportional to the wear resistance of the prepared composite materials. This research will enable the industry partners to supply cutting-edge technologies to the global oil and gas industry that not only minimizes the well running cost but also improves the well resilience.

Instrumento de avaliação prática empírica de materiais termoplásticos para órteses

Abstract Introduction After the advent of low-temperature thermoplastics, their prevalence in the manufacture of orthoses for upper limbs has been identified by several authors. The understanding of their properties by occupational therapists and other professionals working in this field is important in the process of selecting the thermoplastic, which follows a logic to match the material’s characteristics to the desired function for each orthosis. Objectives Systematize the characteristics of low-temperature thermoplastics and, from that, develop an instrument for carrying out practical empirical tests with the materials, to establish criteria for their handling and evaluation. Method Exploratory study consisting of the creation of testing procedures and, consequently, the development of a qualitative assessment instrument that values the practical experience of the professional who handles the material and evaluates each requirement. Results The created instrument includes 14 material characteristics, accompanied by a definition, a procedure with recommendations for the practical testing, and a field for filling in response alternatives. Conclusions The instrument considers important characteristics to be verified during the evaluation of materials and can direct the professional’s observations and records, aiding in clinical decision-making. This will be important to improve the quality of orthoses and other assistive technology devices made with these thermoplastics. In addition, the systematization of the practical evaluation of thermoplastic materials can assist in the development of health studies and research involving materials for orthoses.

Thermo-stamping shear characteristics of thermoplastics based on X-ray micro-CT

ABSTRACT Understanding the thermo-stamping shear characteristics is not only essential to improve the forming quality of the glass fiber reinforced polypropylene (GFRPP) products but also critical to ensure their structure design reliability. Most previous studies primarily focused on the fiber yarn shear characteristics in the outer surface of the composite product, and omitted the shear angle variations of the inner layers, which might increase the failure risk to the product design. In this study, the U-shaped GFRPP rail was manufactured by the thermo-stamping process and scanned layer-by-layer through the X-ray micro-CT technology. Based on the scanning results, the differences in the shear angle variations of different layers at the same position, and within the same layer but different zones were analyzed, respectively. Finally, the effect of the temperature variation on the shear angle variation was analyzed by the simulation method. Results indicate that the interlaminar shear forces and slippages lead to the differences in shear angle variations among different layers. Intralaminar fiber yarn slippages and bending deformations caused the differences in shear angle variations within the same layer. The heat loss of the stamping molds resulted in a lower stamping temperature and further led to shear angle variation reduction.

A tunable magnetorheological electromagnetic absorber based on multiscale design and topology optimization

Electromagnetic (EM) absorbers consisting of micro and macroscopic structures have attracted significant interest because of their high-performance absorption characteristics. However, difficult structural design and complex tunable methods limit the application of EM absorbers. Due to multiscale controlled property under magnetic field, magnetorheological (MR) materials can be an appropriate solution. Therefore, this paper demonstrates a tunable MR electromagnetic absorber based on multiscale design and topological optimization. Microscopically, by incorporating multi-walled carbon nanotubes (MWCNTs) into MR absorbers, the dielectric loss is reinforced while ensuring magnetic loss. Meanwhile, advanced microcomputed tomography (μ-CT) illustrates that applied ball milling and magnetic field can effectively design the particles and microstructures, enhancing the absorption and attenuation characteristics. Macroscopically, based on EM parameters, the thickness and mass can be reduced while improving the absorption property through topology optimization. The results show that the peak value of reflection loss (RLmin) can reach −19.04 dB and effective absorption bandwidth (EAB, RL below −10 dB) reach 6.72 GHz with a thickness of 2.6 mm and magnetic flux density up to 563 mT. In addition, based on the thermoplastic characteristics of MR absorbers, the multiscale structures can be reconfigured under the combined effect of thermal and magnetic field, achieving tunable absorption properties. The results demonstrate that RLmin still achieved −9.33 dB after three reconfigurations. This work not only provides a strategy for multiscale structural design of EM absorbers, but also offers an efficient and convenient method for preparation with high-performance and tunable MR absorbers.

LPKF-LDS technology for the production of three-dimensional schemes on plastics

A promising technology for the production of three-dimensional circuits on plastics, the scope of its current application and prospects for its further development in the radio-electronic industry are considered. The analysis of current opportunities and limitations is carried out. It is shown that the key component of the technology is the correct choice of thermoplastics with suitable characteristics for the intended object, taking into account the resistance to external factors. An analysis of the international and domestic regulatory framework for thermoplastics was conducted. This allowed to determine the key characteristics for 3D-MID-technology and to make a comparison. A classification is proposed on the basis of the key characteristics of thermoplastics for making a decision when choosing materials on the market, taking into account the application in the radio-electronic industry using 3D-MID technology, which is currently either absent or not fully represented. Methods of testing materials for use in the production technology of three-dimensional circuits on plastics and ensuring the quality of manufacturing of radio engineering products, allowing to confirm the compliance of key parameters of materials are studied. The article considers the order of the build process with the application of the LPKF-LDS technology production of three-dimensional circuits on plastics, which allows building a sequence of processes with particular implementation as an example. The considered LPKF-LDS technology as part of the 3D-MID line is planned in the new laboratory “Threedimensional circuits on plastics and flexible media” at the Department of Design and Production of Radioelectronic Devices of the Institute of Radio Engineering and Telecommunications Systems of MIREA – Russian Technological University.

Thermoplastic Deformation of Ladle-Treated Hadfield Steel with Free Crack Susceptibility

Ladle treatment technology is expected to be a new approach for prevailing over the hot crack susceptibility of conventional high-manganese steel. The liquefaction and solidification mechanisms of the conventional and ladle-treated high-manganese steel were detected by DTA. Their solidification structures were observed by optical microscope and scanning electron microscope. Multistage deformation process of the two steels was carried out by using thermomechanical simulator (Bahr TTS-820) from 700 to 1200 °C. In addition, their thermoplastic character was detected by dilatometer (DIL-805/D) from 800 to 1200 °C. On the other hand, TEM was used for explaining the nucleation of cementite and austenite at magnesium sulfide nuclei in ladle-treated high-manganese steel. The results refer to the peculiar microstructure after ladle treatment of high-manganese steel causes a great enhancement in the hot forming character of high-manganese steel in terms of crack susceptibility and flow stress. In addition, the good formability of the ladle-treated high-manganese steel was confirmed by comparing with the low-carbon steel at hot working temperatures.

Thermoplastic Characteristics of Polymer Composite Materials Used for the Manufacture of Ship Systems Pipelines

The article presents thermoplastic characteristics of polymer composite materials developed on domestic raw materials on a thermoplastic matrix-injection material of the VTP-7 brand based on polyaryl sulfones (polysulfone PSU) plastic and sheet material of the VKU-44 brand based on PSU and carbon unidirectional tape ELUR 0.08 PA. In the article, the author considered the modification method of thermoplastic polymers to impart functional properties and mechanisms of their action. It is shown that the developed materials have no analogues in the domestic industry. According to the level of physical and mechanical characteristics, fire-hazard properties and heat resistance, the developed polymer composite materials (PCM) fully meets the requirements for modern thermoplastic PCM, and is not inferior to foreign analogues.

Synthesis of Thermoplastic Poly(2-methoxyethyl acrylate)-Based Polyurethane by RAFT and Condensation Polymerization.

Thermoplastic solid poly(2-methoxyethyl acrylate) (PMEA)-based polyurethane (PU) is synthesized through the reversible addition-fragmentation chain transfer (RAFT) polymerization and the condensation polymerization, using hydroxyl-terminated RAFT reagents and diisocyanate, respectively. Neat PMEA is a promising antithrombogenic liquid used in the medical fields. The thermoplastic property of the solid PMEA-based PU due to hydrogen bonding is confirmed by the dynamic mechanical analysis (DMA) at temperature below 72 °C. The antithrombogenic property of PMEA-based PU is also analyzed by the platelet adhesion test. The number of platelets on PMEA-based PU is 17 cells per unit area, which is smaller than that on the fluorinated diamond-like carbon (F-DLC), a well-known highly antithrombogenic material. It is concluded that a newly synthesized PMEA-based PU exhibits thermoplastic characteristics with excellent antithrombogenicity.

Commercial Marine-Degradable Polymers for Flexible Packaging.

SummaryPlastic pollution is entering the world's oceans at alarming rates and is expected to outweigh fish populations by 2050. This plastic waste originates from land-based applications, like consumer product packaging, and is composed of high-durability polyolefins. These conventional plastics possess desirable properties, including high chemical stability, moisture barrier, and thermoplastic characteristics. Unfortunately, if these materials reach marine environments, they fragment into microplastics that cannot be biologically assimilated. The aim of this review is to investigate commercial polymers that are biodegradable in marine environments but have comparable product stability and moisture barrier properties to polyolefins. Among commercially available biopolymers, thermoplastic starches (TPS) and polyhydroxyalkanoates (PHAs) have been shown to biodegrade in marine environments. Moreover, these biopolymers are thermoplastics and possess similar thermoforming properties to polyolefins. At present, TPS and PHAs have limitations, including chemical instability, limited moisture barrier properties, and high production costs. To replace conventional polymers with PHAs and TPS, these properties must be improved.

Review on the fabrication of fused deposition modelling (FDM) composite filament for biomedical applications

Filament wire is used in fused deposition modelling (FDM) 3D printers as ink for 3D printing purposes. This filament is melted and extruded through the nozzle to print the 3D model. Polymers are widely used to fabricate filament owing to its thermoplastic characteristics. Nowadays, filament wire is made of composite materials that have been extensively studied as its properties are tailored to fulfill the chemical, physical, and mechanical requirements for biomedical applications. The composite material is designed to mimic the tissues or organs and is compatible with in vivo environments without any toxic effects or inflammations. However, there are numerous challenges when fabricating the composite filament to be used as feedstock for the FDM 3D printer, such as limited choices of biocompatible and bioactive materials, as well as difficulty in producing a filament with a constant diameter. Thus, this article reviews and discusses the current progress on fabrication of FDM composite filaments for biomedical applications.

Thermal Properties of Thermoplastic Rubber (TPR) Reinforced with Polytetrafluroethylene (PTFE) Particle Polymer Composite

Thermal exploration of thermoplastic rubber (TPR) and its composites has been playing a vital role in polymer industries during the past few decades. TPR is a compound which shows a thermoplastic character over its melting temperature and has elastomeric conduct within its design temperature range without cross-linking during fabrication. PTFE particles have a high temperature application and discover the best filler particle in the composite. Samples of 100% TPR and 10% PTFE by weight, 20% PTFE by weight mixed specimens with TPR were prepared by utilizing Injection molding strategies. Test results demonstrate PTFE filler included composites displaying high thermal conductivities.

Theoretical and Experimental Review of Applied Mechanical Tests for Carbon Composites with Thermoplastic Polymer Matrix

Abstract This article has a theoretical and experimental character. It presents the characteristics of two main thermoplastics used in the aerospace industry – poly ether ether ketone (PEEK) and poly phenylene sulphide (PPS). The selected materials are compounds for the production of thermoplastic polymer matrix composites. The paper presents a literature review of the application of thermoplastic polymer matrix composite materials in aviation. Additionally, the paper focuses on the characteristics of carbon fibre-reinforced polymer (CFRP) which plays an important role in the production of aerospace components. Testing methods have been chosen on the basis of the type of composite matrix. The article contains the most important mechanical properties and general characteristics of thermoplastics used as a matrix for CFRP type composites used in the aerospace industry. Individual test procedures which allow for the evaluation of mechanical properties of composite materials on a thermoplastic polymer matrix, have been described. Mechanical tests such as static tensile test and bending of short beams were carried out in order to examine CFRP composites.

Failure analysis of thermoplastic composite pipe (TCP) under combined pressure, tension and thermal gradient for an offshore riser application

Useful characteristics of fibre-reinforced thermoplastics, including high specific strengths and moduli and excellent corrosion resistance, make them ideal candidates for offshore riser pipe applications. When in operation, risers are subjected to combined mechanical and thermal loading. In the present paper, a 3D finite element (FE) model is used to analyse stress state in a section of thermoplastic composite pipe (TCP), consisting of a fibre-reinforced thermoplastic laminate fully bonded between inner and outer thermoplastic liners, under conditions illustrative of a deepwater riser application. The effects of varying combinations of pressure and thermal differentials on the distribution of stress-based failure coefficient are examined. Failure responses under different axial tensions at low/high pressures and temperatures are assessed for configurations with different laminate ply stacking sequences. Temperature-dependent material properties are considered in the thermomechanical analysis.

Fracture mechanism characteristics of ultra-thin chopped carbon fiber tape-reinforced thermoplastics hat-shaped hollow beam under transverse static and impact loadings

This paper aims to experimentally and numerically explore fracture mechanism characteristics of ultra-thin chopped carbon fiber tape-reinforced thermoplastics (UT-CTT) hat-shaped hollow beam under transverse static and impact loadings. Three distinct failure modes were observed in the impact bending tests, whereas only one similar progressive collapse mode was observed in the transverse bending tests. The numerical model was to incorporate some hypothetical inter-layers in UT-CTT and assign them with the failure model as cohesive zone model, which can perform non-linear characteristics with failure criterion for representing delamination failure. The dynamic material parameters for the impact model were theoretically predicted with consideration of strain-rate dependency. It shows that the proposed modeling approach for interacting damage modes can serve as a benchmark for modeling damage coupling in composite materials.