Thermal Resistance Properties Research Articles

A new study of dynamic mechanical analysis and the microstructure of polyurethane foams filled.

Polyurethane foams have good shock-absorbing properties. This article discusses the study of the physical, dynamic analysis, and microstructure of filled polyurethane foams (PUR). We used mineral fillings nanoparticles of titanium dioxide (TiO2) and calcium carbonate (C1) to support and strengthen the foam cell structure to develop shock absorption and thermal resistance properties. Dynamic mechanical analysis (DMA) and compression tests compared the mechanic characterization results with different modelling approaches. For studies of physicochemical properties, we used differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). We deduced the flame retardancy mechanism. It appears that a detailed description of the characteristics of viscosity and yield stress must take into consideration the filler's size in comparison to the cell wall's size. The effect of size distribution on the foam's microstructure was given by scanning electron microscopy (SEM). Half-open spherical cells were shown to be reduced in size with filling. The filler diffusion in polyurethane foams was used to model the composite foam. We observed that crystalline filler particles were uniformly distributed in the matrix, indicating that the total size is related to the density and is a crucial metric for the level of reinforcement.

UV-curable self-matting waterborne polyurethane acrylate coating via self-wrinkled surface during curing in open-air.

This study developed and evaluated a series of ultraviolet (UV) curable self-matting waterborne polyurethane acrylate (UV-WPUA) coatings based on the self-wrinkled surface during UV-curing in the open-air. This method is simple, efficient, eco-friendly, and it does not require complicated or expensive equipment. The FT-IR spectrum indicates that the peaks of C[double bond, length as m-dash]C in UV-WPUA have disappeared after UV irradiation. The gloss value of the UV-WPUA cured film can be affected by the wrinkles on the surface of the film and adjusted it by controlling the content of the photoinitiator in the liquid coating, since the content influences the dimensions of the wrinkles. As the height of the wrinkle increased, the gloss value of the UV-WPUA cured film decreased, and when the incident angles are 20° and 60°, the gloss values are less than 3 GU and 5 GU, respectively. Moreover, the cured film has a maximum water contact angle of 109°, which is affected by wrinkles and positively correlated with the surface roughness of the film. Furthermore, the cured film has excellent properties of thermal stability, tensile strength, pencil hardness, cross-cut adhesion and resistance to abrasion properties, making it well suited for the furniture, leather, and textile applications.

Comparative study on the properties of starch-based bioplastics incorporated with palm oil and epoxidized palm oil

This study aimed to modify the starch-based bioplastics with acceptable mechanical and water resistance properties using palm oil (PO) and epoxidized palm oil (EPO). The structural, thermal, mechanical and water resistance properties of the resulted bio-composites were evaluated. EPO had better compatibility within the starch matrix than PO. The bioplastics with PO and EPO exhibited different melting behaviors. Low concentrations of oils (<3 wt%) improved the tensile strength and elongation at break of the bioplastics remarkably, while higher concentrations of oils caused the decrease of tensile properties due to phase separation. Comparatively, EPO was more efficient at enhancing tensile properties than PO due to the presence of epoxy groups. Both oils reduced the water uptake and solubility of the bio-composites slightly. In conclusion, the addition of EPO was a more attractive way to enhance the properties of starch-based bioplastics.

Engineering of the structural and morphological characteristics of MWCNTs employing a nano-dimensional binary oxide coating with enhanced thermal oxidation resistance properties for the tailoring of their reinforcement potential

The present investigation mainly addresses the rational design of a MgAl-binary-oxide-coated MWCNT nano-hybrid architecture and the study of its reinforcement potential.

On Machining behaviour of various cutting Inserts: A review on hardened steel

Cutting tool plays an important criterion for the overall performance of machining to achieve better tool-life, superior surface finish along with immense productivity. The evolution of cutting temperature along with increased cutting parameters accelerates the plastic deformation of insert tip, cutting edge breakage and thus affects the surface quality. Built-up-edge (BUE) formation also enhances rapid tool wear, fluctuations of cutting forces, and vibration. Therefore in modern manufacturing to enhance productivity considering good surface quality, there is striving for innovation and research in the area of novel cutting tool materials. Hard machining emerges as a newer process alternative to traditional grinding performance where popular cutting tool materials used as CBN (Cubic Boron Nitride), ceramics, and coated carbides etc. The benefits of hard machining serve as reduction of the manufacturing cycle, cost, and environmental friendly. Thermal softening and reduction of shear stress due to the rise of cutting temperature enable hard machining easier under dry environment compared to flood cooling. However, tool wear and surface roughness deteriorates and thus reduces tool life due to frequent failure of cutting edge. Thus in the current review, the performance of cutting tool materials during machining hardened steels is focused. Moreover, a proper selection of cooling and lubrication strategy can prolong the tool life and surface finish. Different hard thin layer coatings on carbide tools enhance the machining performance due to thermal barrier, abrasion, and diffusion resistance properties. Due to techno-economical feasibility, coated carbide cutting tools are extensively used during hard machining in recent years which has been developed by CVD/PVD method.

Synthesis characterization and application of hexafunctional epoxy resin and comparison against commercial epoxy resin

Current study compares the various analytical results of hexafunctional epoxy resins based on bisphenol-A with conventional epoxy resins. Reaction of bisphenol-A, formaldehyde, and epichlorohydrin produces hexafunctional epoxy resin. The curing properties of commercial epoxy resin and hexafunctional epoxy resin were determined using a variety of hardeners, including diethylenetriamine, triethylenetetramine, phenalkamine, polyamido amines, and polyamides. The epoxy equivalent weight (EEW), hydrolyzable chlorine content, volatile content, Brookfield viscosity, weight average molecular weight, elemental analysis (C, H, N, O analysis), and Fourier transform infrared spectroscopy were used to characterize the hexafunctional resin (FT-IR). Jute and glass reinforced composites were also prepared by using hexafunctional epoxy resins and commercial epoxy resins. Mechanical properties (tensile strength, flexural strength, Izod impact strength, and Rockwell hardness), thermal properties, and chemical resistance were determined for each composite. Hexafunctional epoxy resin-based composites exhibited superior mechanical characteristics, thermal resistance, and chemical resistance properties than commercial epoxy resin-based composites.

Development of thermal insulation coating for automotive application

The required polymers cannot be directly employed for our applications because of lacuna in the multifunctional aspects. These multifunctional aspects are obtained by blending two or more materials or reinforcement in small proportions in a holding matrix, the infusion of some materials as random reinforcement into the holding matrix brings a lot of difference in the properties of the materials. Among the reinforcement micro v/s nanolevel, nano-level makes a great difference in the observed properties, Compared to the micro-level nanoparticles have surface-dominated properties that make them ideal for the reinforcement of the composites. Nature has chosen the best path for the efficiency of all its systems. Even life science makes the best possible usage of nanotechnology. Nanoparticles made up of silicon & calcium are excellent thermal insulators. These combined with the exceptional insulating properties of the polymer matrix will provide us with a great thermal insulation material for automotive purposes. The resulting combination of the polymer matrix and the nanoparticle is transparent and has an affinity towards metals. This makes it suitable for automotive applications. Among the combination of silicon and calcium with silicone sealant in enhancing the thermal resistance of the developed composites, the best combination resulted with the addition of silicon dioxide with the silicone sealant rather than calcium. This could be due to the amplification of the inherent property of thermal resistance of the silicone element by the addition of the silicon dioxide at the nano level. The thermal resistance of the calcium-modified sealant was 159 °C whereas the silicon dioxide modified sealant showed enhanced thermal resistance of 153 °C as compared to the pristine specimen. Based upon the results calcium silicate gains in addressing the observed properties.

Study on Single Jersey Knitted Fabrics Made from Cotton/ Polyester Core Spun Yarns. Part I: Thermal Comfort Properties

This study focused on the effect of core- sheath ratio, twist and loop length on the thermal comfort properties of single jersey knitted fabrics produced from 100% cotton, 80:20 and 60:40 cotton/polyester core spun yarns. Thermal properties like air permeability, water vapor permeability, thermal conductivity and thermal resistance properties were analyzed with low, medium and high twist and also with loose medium and tight structured fabrics. Box behnken, three level - three variable factorial design software has been used to study the interactive effect of core- sheath ratio, twist and loop length on the thermal comfort properties of single jersey knitted fabrics and response surface equations were derived and design variables were optimized. ANOVA test model reveals the statistical significance of variables on thermal properties with high F-value and low p-values. From this study it is observed that the decrease in cotton ratio decreases the fabric thickness, becomes lighter and more porous with higher thermal conductivity, air permeability, water vapour transmission rate and less thermal resistance. Increase in twist and tight loop structure makes thicker and less porous fabric with higher thermal resistance and lesser air permeability, water vapour transmission rate and thermal conductivity.

Influence of corium temperature, concrete composition and water injection time on concrete ablation during MCCI: New insights

Molten corium, a mixture of molten nuclear fuel, cladding, thermo-hydraulic and structural elements, can originate in a nuclear plant accident after a reactor core meltdown. This un-cooled corium could penetrate through the reactor pressure vessel and cause concrete ablation via basement melt-through, a process known as Molten Corium Concrete Interaction (MCCI). The MCCI analysis because of its complex nature is still uncertain and needs thorough investigation of various parameters. In this study the use of CORQUENCH simulator is presented to model the molten corium, composition of concrete and heat transfer along with related chemical reactions. Using this modeling technique, the chemical reaction capabilities of CORQUENCH is successfully utilized enabling the modeling of interaction between molten corium and concrete. The developed model is validated against experimental data at PWR and BWR conditions. The results showed that the temperature of corium, composition of concrete and water injection time have a pronounced effect on mitigating ablation and reactor integrity in case of a nuclear accident. In addition, the composition of concrete was found to be the main controlling factor to mitigate ablation. An alternative to concrete is to utilize igneous rock (pyrolite) and this approach could lead to comparatively very low rates of ablation due to its high thermal resistant properties. Furthermore, the injection of water (as a cooling agent) into the reactor cavity should also be optimized to enhance corium quenching to avoid ablation via basement melt-through. The concrete ablation mechanisms during MCCI are very case-dependent on the concrete solidus, liquidus and ablation temperatures, respectively.

Enhanced thermal resistance and ablation properties of ethylene-propylene-diene monomer rubber with boron-containing phenolic resins

With the development of aerospace industry, higher requirements have been put forward for the thermal properties of internal insulation materials for heat protection of solid rocket engine chamber. In this study, boron-containing phenolic resin (BPR) was chosen as the thermal-resistant filler of ethylene-propylene-diene monomer (EPDM). By adjusting the amount of BPR, a series of BPR/EPDM were prepared and their thermal, mechanical, and ablation properties were studied. The results showed that the addition of BPR significantly improved the char yield of EPDM. The char yield of BPR/EPDM was 21.6%, which increased by 17.9% (800 °C) relative to EPDM. By studying the structural evolution of BPR/EPDM during pyrolysis, boron oxide (B2O3) was formed, which avoided the formation of volatile carbon oxides and reduced the carbon loss. The molten B2O3 penetrated into the pores of carbonization products, which can protect the unstable edges of graphitic carbon and improve the ablation performance of BPR/EPDM. The linear ablation rate of BPR/EPDM was 0.045 mm/s (the lowest reported in current references). Additionally, the addition of BPR improved the graphitization degree of carbonization product. This research is expected to provide a resin matrix with excellent comprehensive performance and large-scale production for combustion chamber of the solid engine.

Molecular dynamics study on the thermal, mechanical and tribological properties of PBI/PI composites

Temperature resistance of polymer determined their service life as frictional materials. In order to improve the glass transition temperature (Tg), mechanical strength and wear resistance of polyimide (PI), the polybenzimidazole (PBI) with high temperature resistance was introduced for blends. However, research on the blending mechanism of PBI/PI composites were still not fully understood at the atomic level owing to the difficulty in situ experiments. Therefore, molecular dynamics simulation was employed to predict their thermal, mechanical and tribological performance of PBI/PI composites. Results indicated that the glass transition temperature, Young’s modulus and shear modulus of PI increased with an increase of PBI contents, while the friction coefficient of PBI/PI composites sliding against copper decreased. 50%PBI/PI composite had the highest Tg of 575 K increased by 11.2%, Young’s modulus of 8.64 GPa increased over three times and the smallest friction coefficient decreased from 0.16 to 0.11. The thermal expansion ratio of 50%PBI/PI composite also decreased compared to pure PI. The inherent mechanism was explored by analyzing the intermolecular forces. The fractional free volume (FFV) and mean square displacement (MSD) decreased after filling PBI because of strong adsorption effect between PI and PBI molecular, which restricted the movement of PI. Therefore, the thermal resistance and mechanical properties were improved after filling PBI.

Effect of ZnO on the structural, physio-mechanical properties and thermal shock resistance of Li2O–Al2O3–SiO2 glass-ceramics

The composition of lithium aluminosilicate (LAS) with different zinc oxide-magnesium oxide (ZnO–MgO) contents that ranged from 0 to 1.45 wt percent (wt%) was investigated to determine the thermal shock resistance properties of the glass-ceramics. The LAS glasses were melted in an alumina crucible at 1550 °C for 5 h, and the green compact samples were then heat-treated at 1100 °C for 3.5 h. The presence of zinc oxide (ZnO) in the compositions did not change the major crystal phase of β-spodumene. However, the addition of ZnO shifted the pronounced peak to a lower angle and increased the percentage of crystallinity from 55% to 59%. Additionally, the function of ZnO in LAS glass-ceramics as the network modifier was confirmed through Fourier Transform Infrared Spectroscopy (FTIR) analysis. The physio-mechanical properties were improved when 1.45 wt% ZnO was added to the LAS glass-ceramics. The results showed increased density (2.42 g/cm3), low porosity (0.85%), high flexural strength (125.23 MPa), and low coefficient of thermal expansion (25–800 °C) (CTE(25–800 °C)) value of 1.73 × 10−6 °C−1. Meanwhile, the thermal shock resistance properties evaluation of the LAS glass-ceramics at different ZnO contents were conducted at different thermal shock temperatures of 200 °C, 500 °C, and 800 °C. The critical temperature of the LAS specimens with 1.45 wt% ZnO demonstrated the ability to withstand a thermal shock at 800 °C while preserving 87% of their initial strength of 108.40 MPa, exemplifying the best LAS glass-ceramics properties for rapid high-temperature change applications.

Synergistic Effect of Screen-Printed Single-Walled Carbon Nanotubes and Phosphorylated Cellulose Nanofibrils on Thermophysiological Comfort, Thermal/UV Resistance, Mechanical and Electroconductive Properties of Flame-Retardant Fabric.

Single-walled carbon nanotubes (SWCNTs) and phosphorylated nanocellulose fibrils (PCNFs) were used as functional screen-print coatings on flame-retardant (FR) fabric, to improve its thermal resistance and thermophysiological comfort (wetting, water vapour and heat transmission) properties, while inducing it with electrical conductivity and UV protection. The effect of PCNF printing, followed by applying a hydrophobic polyacrylate (AP), on the same (back/B, turned outwards) or other (front/F, turned towards skin) side of the fabric, with and without the addition of 0.1–0.4 wt% SWCNTs, was studied by determining the amount of applied coating and its distribution (microscopic imaging), and measuring the fabric’s colour, air permeability, thickness, mechanical, flame and abrasion resistance properties. Due to the synergistic effect of PCNF and SWCNTs, both-sided printed fabric (front-side printed with PCNF and back-side with SWCNTs within AP) resulted in an increased heat transfer (25%) and an improved thermal resistance (shift of degradation temperature by up to 18 °C towards a higher value) and UV protection (UPF of 109) without changing the colour of the fabric. Such treatment also affected the moisture management properties with an increased water-vapour transfer (17%), reduced water uptake (39%) and asymmetric wettability due to the hydrophilic front (Contact Angle 46°) and hydrophobic back (129°) side. The increased tensile (16%) and tear (39%) strengths were also assessed in the warp direction, without worsening the abrasion resistance of the front-side. A pressure-sensing electrical conductivity (up to 4.9∙10−4 S/cm with an increase to 12.0∙10−4 S/cm at 2 bars) of the SWCNT-printed side ranks the fabric among the antistatic, electrostatic discharge (ESD) or electromagnetic interference (EMI) shielding protectives.

Study on the Thermal and Impact Resistance Properties of Micro PA66/PU Synergistically Reinforced Multi-Layered Biaxial Weft Knitted Fabric Composites

Abstract In this paper, the influence of micro PA66/PU in multi-layered biaxial weft knitted (MBWK) fabric reinforced composites on thermal and impact resistance was studied. The main objective was to investigate the role of micro PA66/PU in terms of improving material performance. The results showed that the addition of micro PA66/PU improved the thermal stability of the MBWK composite. It is observed that the onset degradation temperatures increased by 1.6°C in thermo-gravimetric analysis (TGA) test and the Tg increased by 2.8°C in the dynamic mechanical analysis (DMA) test. Besides, the impact energy absorption of composites increased by 5.3% after the addition of micro PA66/PU. The addition of micro PA66/PU effectively reduced the impact damage area from the failure morphology after impact. In simple words, the addition of micro PA66/PU effectively improves the comprehensive properties of composites.

Preparation of iron oxide nanopowders by the radiation-chemical method

Various magnetic nanopowders of iron oxide were obtained using the radiation-chemical method when irradiated with a nanosecond electron beam. The main physical and chemical characteristics of the prepared nanopowders were studied, such as structure, porosity, thermal resistance and magnetic properties. It was found that, by selecting precursors and the composition of the solution, it is possible to control not only the textural properties and yield of the obtained nanopowders (by changing the dose and dose rate intensity of the electron beam), but also to obtain crystalline or amorphous nanopowders, on which their magnetic properties depend.

Fabrication of polyimide foams with superior mechanical and flame resistance properties utilizing the graft copolymerization between red phosphorus and graphene oxide

In this work, red phosphorus (RP) grafted graphene oxide (GO) was generated inside polyimide foam (PIFs) matrices using a novel method. Definite chemical interaction between RP and GO was confirmed. The RP grafted GO (GO-RP) as a beneficial additive greatly improved the mechanical, thermal and flame resistance properties of the PIFs. Scanning electron microscopy (SEM) revealed the cell size of PIFs/GO-RP minished and homogenized when compared to the pristine PIF. The mean cell diameter decreased to 0.29 mm from 0.38 mm and the open cell content was reduced by 4%. The specific strength increased greatly after adding GO-RP, from 2.14 × 103 N·m/kg to 2.48 × 103 N·m/kg. Besides, the pyrolysis temperature of PIFs/GO-RP shifted to a higher value and the carbon residue increased at 800 °C, indicating excellent thermal properties. The flame resistance property of foams significantly enhanced while the peak heat release rate (PHRR) was reduced by 66% compared to that of the pristine foams. The craft of PIFs/GO-RP presented here has greatly provided an potential value in the design of materials.

Design of tough adhesive from commodity thermoplastics through dynamic crosslinking.

Tough adhesives provide resistance against high debonding forces, and these adhesives are difficult to design because of the simultaneous requirement of strength and ductility. Here, we report a design of tough reversible/recyclable adhesive materials enabled by incorporating dynamic covalent bonds of boronic ester into commodity triblock thermoplastic elastomers that reversibly bind with various fillers and substrates. The spectroscopic measurements and density functional theory calculations unveil versatile dynamic covalent binding of boronic ester with various hydroxy-terminated surfaces such as silica nanoparticles, aluminum, steel, and glass. The designed multiphase material exhibits exceptionally high adhesion strength and work of debonding with a rebonding capability, as well as outstanding mechanical, thermal, and chemical resistance properties. Bonding and debonding at the interfaces dictate hybrid material properties, and this revelation of tailored dynamic interactions with multiple interfaces will open up a new design of adhesives and hybrid materials.

Thermal Resistance of Insulated Precast Concrete Sandwich Panels

Many nations are already working toward full implementation of energy efficiency in buildings known as Green Building. In line with this perspective, this paper aims to develop a thermally efficient precast concrete sandwich panels (PCSP) for structural applications. Therefore, an experimental investigation was carried out to determine the thermal resistance of the proposed PCSP using Hotbox method and the results were validated using finite element method (FEM) in COMSOL Multiphysics Software. The PCSP were designed with staggered shear connectors to avoid thermal bridges between the successive layers. The staggered connectors are spaced at 200 mm, 300 mm and 400 mm on each concrete layer, while the control panel is designed with 200 mm direct shear connection. In the experimental test, four (4) panels of 500 mm × 500 mm and 150 mm thick were subjected to Hotbox Test to determine the thermal resistance. The result shows that thermal resistance of the PCSP with staggered shear connection increases with increase in spacing. The PCSP with 400 mm staggered shear connectors indicates the best thermal efficiency with a thermal resistance (R value) of 2.48 m2K/W. The thermal performance was verified by FEA which shows less than 5% error coupled with a precise prediction of surface temperature gradient. This indicates that, with conventional materials, thermal path approach can be used to develop a precast concrete building with better thermal resistant properties. Hopefully, stakeholders in the green building industry would find this proposed PCSP as an alternative energy efficient load bearing panel towards sustainable and greener buildings.

Crosslinking polydopamine/cellulose nanofibril composite aerogels by metal coordination bonds for significantly improved thermal stability, flame resistance, and thermal insulation properties

Crosslinking polydopamine/cellulose nanofibril composite aerogels by metal coordination bonds for significantly improved thermal stability, flame resistance, and thermal insulation properties

Characterization of Thermal Bio-Insulation Materials Based on Oil Palm Wood: The Effect of Hybridization and Particle Size.

Oil palm wood is the primary biomass waste produced from plantations, comprising up to 70% of the volume of trunks. It has been used in non-structural materials, such as plywood, lumber, and particleboard. However, one aspect has not been disclosed, namely, its use in thermal insulation materials. In this study, we investigated the thermal conductivity and the mechanical and physical properties of bio-insulation materials based on oil palm wood. The effects of hybridization and particle size on the properties of the panels were also evaluated. Oil palm wood and ramie were applied as reinforcements, and tapioca starch was applied as a bio-binder. Panels were prepared using a hot press at a temperature of 150 °C and constant pressure of 9.8 MPa. Thermal conductivity, bending strength, water absorption, dimensional stability, and thermogravimetric tests were performed to evaluate the properties of the panels. The results show that hybridization and particle size significantly affected the properties of the panels. The density and thermal conductivity of the panels were in the ranges of 0.66–0.79 g/cm3 and 0.067–0.154 W/mK, respectively. The least thermal conductivity, i.e., 0.067 W/mK, was obtained for the hybrid panels with coarse particles at density 0.66 g/cm3. The lowest water absorption (54.75%) and thickness swelling (18.18%) were found in the hybrid panels with fine particles. The observed mechanical properties were a bending strength of 11.49–18.15 MPa and a modulus of elasticity of 1864–3093 MPa. Thermogravimetric analysis showed that hybrid panels had better thermal stability than pure panels. Overall, the hybrid panels manufactured with a coarse particle size exhibited better thermal resistance and mechanical properties than did other panels. Our results show that oil palm wood wastes are a promising candidate for thermal insulation materials.