High-temperature Resin Research Articles

Design and Development of a Fully Printed Accelerometer with a Carbon Paste-Based Strain Gauge.

In this paper, we present a fully printed accelerometer with a piezoresistive carbon paste-based strain gauge printed on its surface, which can be manufactured at low cost and with high efficiency. This accelerometer is composed of two parts: a sensor substrate made from high-temperature resin, which is printed by a 3D printer based on stereolithography apparatus (SLA), and a carbon paste-based strain gauge fabricated by screen-printing technology and by direct ink writing (DIW) technology for the purposes of comparison and optimization. First, the structural design, theoretical analysis, simulation analysis of the accelerometer, and analyses of the conductive mechanism and the piezoresistive mechanism of the carbon paste-based strain gauge were carried out. Then the proposed accelerometer was fabricated by a combination of different printing technologies and the curing conditions of the carbon paste were investigated. After that, the accelerometers with the screen-printed strain gauge and DIW strain gauge were characterized. The results show that the printing precision of the screen-printing process on the sensor substrate is higher than the DIW process, and both accelerometers can perform acceleration measurement. Also, this kind of accelerometer can be used in the field of measuring body motion. All these findings prove that 3D printing technology is a significant method for sensor fabrication and verification.

Mechanical properties of pultruded high-temperature-resistant carbon-fiber-reinforced polymer tendons at elevated temperatures

Cable roof structures built with carbon-fiber-reinforced polymer (CFRP) cables instead of steel cables, which are called CFRP cable roofs, represent a new structure with great development potential. However, as one of the main stressed components of structures, CFRP cables are required to have better fire resistance. In this paper, the fire resistance of a type of high-temperature-resistant (HTR) CFRP tendon is studied. A total of 39 specimens with a diameter of 5 mm are performed in this study, among which 33 specimens are for steady-state tensile tests and 6 for transient state tests. Steady-state tensile tests are conducted over in the 20–600 °C range, and transient state tests are conducted for stress levels ranging from 0.19 to 0.57. The steady-state test results show that HTR CFRP tendons have excellent room-temperature and high-temperature mechanical properties. The strength remained 78% at 200 °C and the elastic modulus remained 82% at 300 °C, indicating the effectiveness of high-temperature resistant resin matrix. When the temperature reaches 600 °C, the strength remains 19%. The transient state test results show that the high initial stress (stress level of 0.57) can aggravate damage to CFRP tendons at high temperatures. Finally, a high-temperature equation is obtained for the temperature dependence of the strength and modulus of HTR CFRP tendons by developing a mathematical model that is fitted to the test data.

Design of Injection Mold from Plastic Material

This paper deals with the use of plastics for making injection molds. Mold production times reduced by 90% and costs cut by up to 75% are some of the benefits of prototype molds from plastic materials. Today, materials with melt temperatures above 300 °C are used for plastic molds. They include ABS, PE, PP and PA. In this study, testing of high-temperature resin from Formlabs was performed. Compression and tensile test data are compared with the datasheet values and with virtual simulations. The tests were carried out at different temperatures. Based on their results, one can identify a suitable molding process with molds from this material.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

A high sensitivity micro-pressure sensor based on 3D printing and screen-printing technologies

A 3D-printed micro-pressure sensor with high sensitivity is developed in this paper. It is a fully printed pressure sensor fabricated using a combination of digital light processing (DLP)-based printing and screen-printing technologies, with the advantages of high manufacturing efficiency and low cost. The pressure sensor consists of a sensor substrate with a circular diaphragm and a Wheatstone bridge on the surface. First, the pressure sensor was theoretically analyzed and then verified using the finite element method (FEM). During fabrication, the sensor substrate was made from a transparent high-temperature resin, which was printed by a DLP-based 3D printer. The resistors and leads of the Wheatstone bridge were made from carbon paste and silver paste, respectively, and printed by screen-printing technology. Then, the resistors were characterized to find the gauge factor and the print consistency between different resistors. Next, the experimental setup was established for the characterization of the pressure sensor. Three loops of pressurization and depressurization from 0 kPa to 2.4 kPa were applied to the pressure sensor continuously, and the output voltage was recorded. The experimental results show that the gauge factor of the carbon resistor is 17.01 ± 1.85, the sensitivity of the sensor is 4.5522 mV/kPa/5 V, the linearity error is 2.077% FS, the hysteresis error is 6.327% FS and the repeatability error is 5.708% FS. Also, it is very convenient to obtain pressure sensors with different sensitivities and measurement ranges by changing the thickness of the circular diaphragm. All these results prove that the proposed sensor provides a low cost and high sensitivity approach for micro-pressure measurement, and that 3D printing can be applied to the production of personalized sensors.

Experimental comparative study of the variants of high-temperature vacuum-assisted resin transfer moulding

A considerable collection of VARTM choices for composite manufacturing techniques can be both found in literature as well as in industry. Each manufacturing process provides different benefits that must be carefully considered depending on the final application of the desired composite. Here, we present a performance comparison in terms of process effectiveness related to fibre volume fraction, the magnitude of thickness variation, and void contents of 16 laminated composites manufactured by different variants of VARTM (DBVI, VAP, and CAPRI) as well as HIPRTM. Non-crimp carbon textile reinforcements and five-harness satin woven carbon textile reinforcements with a PRISM® EP2400 resin system as base constituents are used to produce composite panels. After manufacturing 16 composite panels, an evaluation of the pros and cons of the processing vs properties/performance obtained with each of them is discussed.

Design and Fabrication of 3D Printed Reconfigurable Metamaterial-inspired Structures

Abstract In this paper, 3D printing is used as an alternative manufacturing technique to fabricate metamaterial-inspired RF structures for liquid profiling. A dual split-ring resonator (SRR) based sensor tag is designed and integrated with a microfluidic channel for detecting different liquid samples. The sensor is 3D printed using a high-temperature resin and metallized using a custom developed metal patterning process. The sensor requires a very small volume of 8.6 μL of sample under test for detection. The resonance frequency of the SRR changes with change in sample loading and the shift is monitored for sample profiling. Different volatile organic compounds are introduced and the shift is monitored demonstrating the sensitivity of the proposed tag. The low-cost, real-time nature of the tag makes it an ideal choice for monitoring liquids along the supply chain.

Research of a Novel 3D Printed Strain Gauge Type Force Sensor.

A 3D printed force sensor with a composite structure developed by combining digital light processing (DLP) based printing and inkjet printing technologies is described in this paper. The sensor has cost effectiveness and time-saving advantages compared to the traditional sensor manufacturing process. During this work, the substrate of the force sensor was printed by a DLP based 3D printer using a transparent high-temperature resin, and the strain gauge of the force sensor was inkjet printed using poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT/PSS) conductive ink. Finite element (FE) simulation was conducted to find the print origin of the strain gauge. The relationship between the mechanical properties of the post-cured resin and the curing time was investigated and the resistance of the printed strain gauges was characterized to optimize process parameters. Afterward, the force sensor was characterized. Experimental results show that the sensitivity of the sensor is 2.92% N−1 and the linearity error is 3.1485% full scale (FS) within the range from 0 mN–160 mN, and the effective gauge factor of the strain gauge is about 0.98. The resistance drifting is less than 0.004 kΩ within an hour. These figures prove that the device can perform as a force sensor and 3D printing technology may have great applied potential in sensor fabrication.

Catalytic Condensation of Carbonyl Compounds during the Synthesis of Cyclohexanone in the Production of Caprolactam

Kinetic features of the condensation processes of carbonyl and unsaturated impurities in cyclohexanone have been studied using model mixtures in a heterophase system in the presence and absence of phase-transfer catalysts. It has been shown that linear aldehydes are condensed with cyclohexanone in the heterophase system in the presence and absence of phase-transfer catalysts under mild conditions (30–50°C). Noncarbonyl unsaturated compounds (e.g., 2-cyclohexene-1-ol) can be removed only at temperatures above 100°C in the presence of acidic catalysts (e.g., high-temperature sulfonated cation-exchange resins). Unsaturated cyclic ketones are characterized by both alkylation reactions over acid catalysts and aldol condensation reactions in the presence of an alkali, thereby suggesting the possibility of their elimination at different cyclohexanone purification steps. The theoretical models built can be used to develop an effective cyclohexanone purification technology that will substantially enhance the manufacturability of high-purity caprolactam and polyamide.

Specific heat, thermal conductivity, and magnetic susceptibility of cyanate ester resins – An alternative to commonly used epoxy resins

In low temperature experiments, resins have many applications as glues or thermal and electrical insulators. Cyanate ester resins (CEs) are a high-temperature compatible thermoset resin whose glass-transition temperature Tg is ≈300 °C. Recently, we found that CEs also withstand low temperatures without microcracking by measuring 4He permeability. Here, we measured specific heat C, thermal conductivity κ, and magnetic susceptibility χ of different kinds of CEs in the wide temperature range from room temperature to 0.5 K for C and 2 K for other two. The thermal properties, C and κ, of different kinds of CEs are surprisingly coincident with each other. We discuss chemical structures and crystallinity of CEs and their blends based on the measured thermal properties. Compared to Stycast 1266, a commonly-used epoxy resin in low temperature experiments, C of CEs is larger by a factor of 3 (≤30 K), κ is lower by a factor of 4 (≤10 K), indicating the small thermal diffusivity. The χ values are as small as Stycast 1266, indicative of their high purity. Our results show that cyanate esters are a new option for cryogenic resins with thermal insulative properties in/for low temperature experiments.

The effect of phthalide cardo structure on the shape memory performance of high-temperature resistant epoxy resins

The novel high-temperature resistant shape memory (SM) materials which were prepared based on diglycidylether of bisphenol A (DGEBA) epoxy resin with a chain-extended aromatic diamine containing phthalide cardo structure (BAPP) as curing agent. The influence of deformation temperature and loading rate on the deformability, and the dependence of shape recovery ratio (Rr) and shape fixity ratio (Rf) on the fixed deformation temperature, imposed deformation load, shape fixity cooling rate and number of cycles were investigated by dynamic mechanical analyzer (DMA) in comparison with these of the common aromatic amine-cured epoxy systems. The deformability, Rr and Rf could be improved markedly by changing the SM programming conditions. The results demonstrate the incorporation of phthalide groups plays an important role on the improvement of SM performance of epoxy networks.

High Tg and Thermo-Oxidatively Stable Thermosetting Polyimides Derived from a Carborane-Containing Diamine.

To provide high-temperature polyimide matrix resins, novel carborane-containing thermosetting polyimides are presented. First, the low-viscosity carborane-containing imide oligomers are synthesized using newly designed 1-(3-amino-4-tolyl)-2-(4-aminophenyl)-o-carborane and aromatic dianhydride as monomers, 4-phenylethynyl phthalic anhydride as the end-capping reagent. Followed by thermal curing, the resulting polyimides show high Tg (≥500°C) and above 92.1% char yield at 800°C both in nitrogen and air atmosphere due to the incorporation of the bulky carborane cages. Aging studies, performed at 400 and 500°C for 5 h in air on a carborane-containing polyimide and a carborane-free polyimide, show that the polyimide with carborane groups possesses excellent thermo-oxidative stability. Moreover, the novel polyimides exhibit constant and relatively low coefficient of thermal expansion values over a wide range of temperature, indicative of a remarkable dimensional stability. Thus, this study clearly demonstrates the viability of the incorporation of carborane cages to access polyimide thermosets with ultrahigh Tg and thermo-oxidative stability.

Oligosilylarylnitrile: The Thermoresistant Thermosetting Resin with High Comprehensive Properties.

One of the highest thermoresistant thermosetting resins ever studied so far, oligosilylarylnitrile resin, was investigated first in this study. Oligosilylarylnitrile was synthesized by lithium-reduced Wurtz-Fittig condensation reaction, and the prepared viscous resin exhibited moderate rheological behaviors while heated purely or together with 20% polysilazane as a cross-linking agent. The thermal curing temperatures were found by differential scanning calorimetry at 268 °C (pure) and 158 °C (with the polysilazane cross-linking agent), which is comparably close to that of polysilylarylacetylene resin (normally at 220-250 °C) but much lower than those of polyimide and phthalonitrile resins (normally >300 °C), indicating the admirable material processability of oligosilylnitrile. The cured oligosilylarylnitrile resins have extremely high thermal resistance, indicated by the results of thermogravimetric analysis (the mass residue at 800 °C is >90% under N2) and dynamic mechanical analysis (the glass-transition temperature is >420 °C). The mechanical property of the oligosilylarylnitrile-matrixed silica-cloth reinforced laminate is comparably close to those of polyimide and phthalonitrile but much higher than that of polysilylarylacetylene, indicating the enviable thermal and mechanical properties of oligosilylnitrile. Thus, among the high-temperature resins ever studied so far, the oligosilylarylnitrile resin was found to have the almost best comprehensive characteristics of processability and properties.

Low thermal and high electrical conductivity in hollow glass microspheres covered with carbon nanofiber–polymer composites

To take advantage of both the low density and thermal conductivity of hollow glass microspheres, and the high mechanical and electrical conductivity of carbon-based nanofillers, micro- and nanosized fillers can be combined into a single composite material. Here we prepared composite materials from hollow glass microspheres (HGMs) and from the same microspheres surrounded by carbon nanofibers (CNFs). By adding 10% wt. of HGM-CNFs to a high-temperature resin we can obtain a low density (0.8 g/cm3), low thermally (0.17 W/mK) and high electrically conductive (7±3×10−4S/m) composite. This novel method demonstrates the possibility to achieve an unusual combination of properties such as low thermal and high electrical conductivity which, along with their light weight and thermal stability, makes these materials promising for aerospace applications or thermoelectric devices.

Low-Molecular-Weight, High-Mechanical-Strength, and Solution-Processable Telechelic Poly(ether imide) End-Capped with Ureidopyrimidinone

Solution-processable poly(ether imide)s (PEIs) with ureidopyrimidinone (UPy) end groups were prepared by incorporating monoisocyanato-6-methylisocytosine into amine-terminated PEI oligomers. After functionalization with UPy end groups, PEI with a molecular weight as low as 8 kDa (8k-PEI-UPy) can be solution-cast to form films. Tensile tests revealed that 8k-PEI-UPy had an outstanding Young’s modulus higher than those of state-of-the-art high-molecular-weight commercial PEIs. The tensile strength, maximum elongation, and Young’s modulus of 8k-PEI-UPy were 87.2 ± 10.8 MPa, 3.10 ± 0.39%, and (3.20 ± 0.14) × 103 MPa, respectively. The discovery herein significantly advances the chemistry of high-temperature PEI resins. UPy-based supramolecular chemistry is an effective and general strategy to achieve outstanding mechanical properties for PEI oligomers.

Effect of Diluent on Performances of High-Temperature Resistance Epoxy Resin

Effect of Diluent on Performances of High-Temperature Resistance Epoxy Resin

ПОГРЕШНОСТЬ ФОРМООБРАЗОВАНИЯ ТЕЛ ВРАЩЕНИЯ ПРИ ИСПОЛЬЗОВАНИИ ТЕХНОЛОГИЙ БЫСТРОГО ПРОТОТИПИРОВАНИЯ

The purpose of the work was the study of error appearance in cylindrical surfaces at prototyping. To achieve the purposed specified there were developed sketches of parts of “cylinder” type. On the basis of the sketches there were created 3D computer models in the CAD medium. Cylinder growth took place at an angle of 90° to a basic surface of a working platform with a pitch of a platform z=50 mkm at the thickness of a layer hc=0.005 mkm. Among basic requirements made for cylinders under investigations consist in circularity and cylindrical shape and also surface layer quality according to an arithmetic mean of Ra. Parts were typed according to the technology of quick prototyping (Rapid Prototyping - RP) – Direct Light Projection – DLP of hightemperature resin.
 To obtain data calculated there was used a simulator of A.I. Grabchenko which underwent some changes and was used for the technology of DLP rapid prototyping. For more accurate and deep investigations a coordinate measuring Metris LKV machine for the elevation of a surface layer quality was used.
 It is evident from the results presented that at empirical investigations of a cylindrical surface grown according to the technology of DLP rapid prototyping and at the computation of shaping error the results convergence makes 96.6.3%.

Modified coin cells to evaluate the electrochemical properties of solid-state fluoride-ion batteries at 150 °C

In the scope of developing new chemistries for electrochemical energy systems, rechargeable solid-state fluoride-ion batteries are attractive devices owing to their high theoretical energy density. State of the art of fluoride ion conductors require the use of high temperature electrochemical cells to overcome the low ionic conductivity of the electrolyte at room temperature. In this work, we modify a coin cell to evaluate the electrochemical properties of fluoride-ion batteries at elevated temperature, over long periods of time and outside a glovebox. The coin cell is covered by a high-temperature epoxy resin that enables efficient sealing and therefore protection against air atmosphere at 150°C. The suitability of the setup is confirmed by electrochemical investigation performed on a symmetrical cell assembled with composite electrodes made of Bi and BiF3. Notably, a reversible capacity of around 190mAh/g after 3 cycles is reached with the modified coin cell setup.

ИССЛЕДОВАНИЕ ЗАКОНОМЕРНОСТЕЙ ФОРМИРОВАНИЯ ТОЧНОСТНЫХ ПАРАМЕТРОВ ДЕТАЛЕЙ ПРИ ПРОТОТИПИРОВАНИИ

The purpose of the work was the study of regularities in the cylindrical surface formation at prototyping. To achieve the task there were developed sketches of two parts of “cylinder” type. According to the sketches in the CAD medium there were formed two 3D computer parts. The next step to achieve the task was the conversion of the designed and created para-metric 3D part in STL format. The printing was carried out in two product lines: the cylinders of the first prod-uct line were printed at the maximum rate of the formation (Vform=12.7mm/h) and at the maximum layer thickness (Slayer=100 mkm), and cylinders of the second product line – at Vprint=5 mm/h; Slayer=50 mkm. The parts were printed according to the method of rapid protopyping (RP) – photopolymer light curing (Direct Light Projection –DLP) on Envision Ultra 3SP plant. Material – high-temperature photopolymer resin HTM 140. Heatresistance of this material makes 140°C.
 As a result of the research there was revealed a vivid saddle-shaped form in printed cylinders. The reason of a hidden defect lies in a high rate of printing and also in a layer thickness. It should be excluded that the reason of an error can be electronic mistakes during a 3D conversion of an object from CAD medium into STL format.

Technology Developments Toward ELM Coil Manufacturing Appropriate for Tokamak

The Institute for Plasma Research (IPR) has been developing technologies appropriate toward realizing fusion-relevant edge-localized mode (ELM) magnets in Tokamaks, such as suitable for Joint European Torus (JET) and Steady State Superconducting Tokamak (SST-1). The development of characteristic winding topologies, developing an appropriate “special-purpose winding facility,” developing a high-temperature resin insulation system, developing vacuum pressure impregnation of high-temperature resin systems in a manufactured winding pack, developing profiled-case manufacturing technologies, and developing technologies at consolidating and encasing the impregnated winding packs are some of the essential aspects of realizing an ELM control coil. In these contexts, under an IN-EU joint initiative, the Magnet Technology Development Division at IPR has developed 1:1 prototypes of JET ELM control coils. These technologies would also be extended to the SST-1 ELM coils. This paper would elaborate on some of the salient technologies developed in support of JET ELM prototype coil realization.