Thermal Barrier Properties Research Articles

Insight into the complex coupling agents on thermal, mechanical, and barrier properties of lignin‐poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) biocomposites

AbstractBiodegradable polymers, including poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBH), can replace traditional plastics to effectively target microplastic pollution; however, their high cost limits their application. In this study, lignin modified with the complex coupling agents was prepared and incorporated into PHBH to reduce its cost and improve the compatibility of composites. The results showed lignin modified with the complex coupling agents was dispersed well in the PHBH matrix. Compared to other composites, lignin‐PHBH biocomposites modified with maleic anhydride and KH550 had better thermal stability, mechanical and barrier properties due to collaborative modification. Moreover, lignin‐PHBH biocomposites showed the excellent UV resistance and antioxidant activity. The obtained results revealed that using the complex coupling agent was a feasible method to improve the properties of biocomposites.

Material properties and antimicrobial activities of starch/PBAT composite films incorporated with ε-polylysine hydrochloride prepared by extrusion blowing

In this study, starch/PBAT antimicrobial films with different ε-polylysine hydrochloride (ε-PL) contents (0, 1, 2, 3, and 4 wt%) were developed by extrusion blowing. Rheological results indicated that incorporation of ε-PL decreased the complex viscosity and storage modulus of blends. Fourier transform infrared spectra revealed that intermolecular hydrogen bonds were formed between ε-PL and starch. The incorporation of ε-PL enhanced thermal stability, ultraviolet barrier and oxygen barrier properties of the films; however, the composite films had heterogeneous microstructures with decreased surface hydrophobicity, moisture barrier, and mechanical properties. Antimicrobial activity of the films increased with increasing ε-PL contents; at 4 wt% ε-PL level, the growth of all tested microorganisms (Staphylococcus aureus, Bacillus subtilis, and Escherichia coli) was effectively inhibited. The ε-PL containing starch/PBAT blown films are promising as an antimicrobial packaging material for delaying food spoilage.

Novel aldehyde sensitive bio-based colorimetric film for kiwi fruit freshness monitoring

The novel colorimetric film was designed to monitor the aldehyde emission from kiwi fruit based on ethyl cellulose/polyvinyl alcohol (EC/PVA) incorporated with poly (ethylene glycol) bis(3-aminopropyl) terminated (amine-PEG) and methyl red. The different colors of aldehyde-sensitive films were caused by a change in alkalinity, which was caused by nucleophilic addition reaction between aldehydes and amine-terminated polymers. The structure and basic properties (thermal stability, mechanical properties, hydrophobicity and barrier property) of the film were studied, as well as the colorimetric response of the film to aldehyde and its application in detecting of kiwi fruit freshness. Low incorporation of amine-PEG (no more than 2%) can improve the thermal stability and water vapor barrier of the films. When amine-PEG content was 2%, amine-PEG can be well distributed in the EC/PVA matrix by interaction of hydrogen bonding. As the kiwifruit ripened, the color of films changed from yellow to orange, and finally to red. The trends of color change in colorimetric film was similar with the changes of kiwi fruit freshness parameters, including sensory tests, TSS, hardness, weight loss rate, titratable acidity, ascorbic acid content and MDA. Therefore, the films can be used to real-time monitor the freshness of kiwi fruit during shelf life.

Preparation and Characterization of a Thermal Barrier Heat-Resistant Silicone Coating

In this study, a heat resistant coating with thermal barrier property was designed. Two types of silicone resin (based on methoxy methyl polysiloxane and methyl phenyl silicone resin) were used as thermal resistant binders, and the black iron oxide pigment and glass micro hollow sphere (MHS) additive were utilized to formulate the heat resistant/thermal barrier coatings. Coatings were applied to the steel substrates, and general properties of the coatings such as film formation, curing, and adhesion were then studied. The thermal stability of the coatings was evaluated by thermogravimetric analysis up to 450 °C. The thermal conductivity coefficient of the coatings was measured by temperature modulated differential scanning colorimeter (TMDSC). Investigation of the properties of all coatings showed that the silicone coating with the 7% of hollow microsphere had higher thermal stability (Tmaximum weight loss= 538 °C) and better barrier properties (Thermal conductivity= 0.29 W/mK (compared with other coatings.

Effect of natural deep eutectic solvent and chitosan nanoparticles on physicochemical properties of locust bean gum films

Novel bio-based films containing Locust Bean Gum (LBG) and Chitosan (CH) or Chitosan nanoparticles (CH-NPs)/natural deep eutectic solvents (NADES) were investigated. The films with different LBG and CH-NPs w/w ratios in the absence or in the presence of NADES plasticizer were prepared by a semi-continuous knife-coating process. The detailed characterization of the films confirmed their transparency, uniformity, and homogeneity, without cracks or pores. FTIR spectra confirmed physical entanglements and miscibility between film components and suggested the occurrence of interaction between CH and LBG components. The mechanical, optical, rheological, thermal and water barrier properties of the new films were also evaluated. It was found that addition of CH-NPs reduced the apparent viscosity of LBG solution, and that the presence of NADES provided more flexible films with less mechanical and barrier resistance. In contrast, the addition of CH-NPs to the LBG solution provided films with enhancement of tensile strength and Young's modulus and a slight increase in water vapour permeability.

Quantitative thermodynamic investigation of thermal stability and diffusion barrier property of an amorphous cobalt alloy interlayer

We explored suitable amorphous alloys for a diffusion barrier interlayer between conductor and insulator materials for advanced semiconductor devices. A thermodynamic simulation method was employed, for the first time in the field of large-scale integrated circuit interconnections, to enable quantitative evaluation of the thermal stability and diffusion barrier property of the interlayer, which led us to narrow down a vast number of binary alloy candidates to a few cobalt-based alloys. The selected alloys were experimentally examined for adhesion strength with an oxide insulator, resistivity variation with composition, annealing temperature and film thickness, thermal stability of composition distribution and structure, and diffusion barrier property under high electric field at elevated temperature. Combining the simulation and experimental results, we proposed an amorphous Co-15 at. %Zr alloy as the most suitable choice and discussed its possibility and challenges.

Gelatin-based composite films and their application in food packaging: A review

Gelatin is an important biopolymer that is extracted from collagen and is extensively used in the food industry because of its excellent functional properties. However, native gelatin films are moisture-sensitive and readily dissolve, swell, or split when they come in contact with water, which limits its use in food packaging. Various natural and synthetic materials are incorporated in gelatin films to improve their mechanical and thermal stability, elasticity, flexibility, and oxygen and light barrier properties. This review discusses various methods used for gelatin-based film production and modification approaches for improving their functional properties, including mechanical strength, thermal stability, water and light barrier ability, solubility and swelling, and antimicrobial properties. Moreover, gelatin-based films extend the shelf life of stored products due to their antioxidant and anti-microbial properties. The potential applications, challenges, and limitations of gelatin-based films in food packaging are also discussed. However, further research is required to prolong the modification of gelatin-based films using naturally available edible materials that are not commercially utilized. Further, studies about possible health hazards associated with the continuous use of gelatin-based packaging films should also be conducted in the future. • Various natural and synthetic materials are incorporated with gelatin to improve their properties. • Gelatin-based composites extend the shelf-life of food by reducing oxidation and microbial contamination. • The potential applications, challenges, and limitations of gelatin-based composites in food packaging were discussed.

Ductile gas barrier poly(ester–amide)s derived from glycolide

Sustainable poly(ester–amide)s derived from glycolide have been synthesized and their thermal, mechanical, and gas barrier properties have been studied by systematically changing the number of methylene groups.

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.

Thermal properties of surface-modified nano-Al2O3/Kevlar fiber/epoxy composites

The mechanical and thermal properties of Kevlar fiber reinforced polymer composites are favorable. Researchers have extensively studied to improve these composites' mechanical characteristics, but research into improving their thermal properties is still limited. The aim of this study is to further improve the thermal properties of Kevlar fiber reinforced epoxy composite using surface modified Al2O3 nanoparticles. Vacuum-assisted resin infusion method (VARIM) was used to produce nanocomposite laminates. The surface of Al2O3 nanoparticles was modified with a silane coupling agent. Ultrasonication and magnetic mixing were used to incorporate Al2O3 at various wt.% (1, 2, 3, 4 and 5) into epoxy. Thermal stability was determined by performing differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) and measuring thermal conductivity and thermal diffusivity. The results obtained revealed that the surface-modified Al2O3 nanoparticles exhibit good thermal barrier properties and improve thermal stability. In terms of degradation temperature and specific heat capacity, the thermal stability of Kevlar composites is best at 3 wt% Al2O3. SEM images and EDX processing were used to determine the morphological characteristics. The chemical composition was confirmed by EDX analysis, and SEM images revealed that the failure occurred in fiber and matrix-related mechanisms. Fourier transform infrared (FT-IR) spectra were recorded using a FT-IR spectrophotometer. It was seen that three new peaks appear with the addition of surface-modified Al2O3.

A review on the application of bio-nanocomposites for food packaging

Globalization has widened the markets of food producers across the globe. The need for packing the foodstuff to maintain the quality and longer shelf-life is growing day by day. The vital requirements, for a material to be used as a packaging material, are better mechanical strength, biodegradability, good thermal stability and barrier properties. Plastics and other polymers find the major share in materials used for packaging and containers. The usage of plastics and polymers will generate non-recyclable waste and stands as a hindrance in creating a cleaner and greener environment. As a result of extensive research in the process of finding a suitable alternative, a new family of material called bio nanocomposites gives a ray of hope. This review aims to throw light on understanding the various research work done so far in this field and to prepare an organized classification of various biopolymer nanocomposites based on their application for specific needs. This kind of review will be helpful for the potential industries in identifying the right biopolymer nanocomposites for packing and preserving their products.

Bio-based aliphatic/aromatic poly(trimethylene furanoate/sebacate) random copolymers: Correlation between mechanical, gas barrier performances and compostability and copolymer composition

Highly promising fully biobased random copolyesters, poly(trimethylene 2,5-furandicarboxylate-co-trimethylene sebacate) (PTFcoPTSeb), were synthesized by using bio derived 1,3-propanediol, dimethyl ester of 2,5- furandicarboxylic acid, and sebacic acid, through eco-friendly polycondensation in the melt. Copolymers with high molecular weight containing 5, 15, 25 mol % of PTSeb were obtained, and their chemical structure confirmed by 1H NMR and FTIR spectroscopy. The thermal, tensile and gas barrier properties and composability were studied in relation to the copolymer supramolecular structure. As expected, introduction of PTSeb co-units results in lowering of glass transition temperature of copolymers and improves their flexibility. Besides, all copolymers showed outstanding gas barrier properties to O2 and CO2, with copolymer containing 15 mol % of PTSeb showing exceptional gas barrier properties, better than those of PTF and comparable to those of EVOH, currently used in multilayer packaging films. The same copolymer exhibited temperature induced shape memory behaviour. It was found that low amounts (15-25 mol %) of PTSeb in copolymer significantly modifies PTF thermal, mechanical and barrier properties and renders the final material compostable. Copolyesters containing 15 and 25 mol % of PTSeb can compete in some applications with commercially available compostable Ecoflex® polymer, but with markedly improved barrier properties.

The influence of silane on the physico-mechanical properties of vulcanizates using bentonite fillers

Layered phyllosilicate fillers have received attention in the polymer industry due to their unique nanoscale sheet-like structure. Adding a small amount of bentonite nanofiller gives rise to improved mechanical, thermal, and gas barrier properties of rubber mixtures. Depending on the application, natural bentonite is often modified by physical processes or by chemical processes (intercalation, cation exchange process, functionalization, pillaring, etc.). Chemical modification increases the size of the interlayer spaces and provides a hydrophobic environment. Functionalization (e.g., silanization), which encompasses the chemical grafting of thermally stable silane coupling agents onto the clay platelets, make inorganic bentonite and the organic polymer matrix compatible. In the introduced study, commercial bentonite P130 from Lieskovec deposit was modified by silane (3-aminopropyl trietoxysilane) treatment. Different techniques such as infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize modified and raw bentonite sample. Silanized P130s and raw product P130 were added to the natural rubber matrix to examine the influence of chemically functionalized bentonite on curing characteristic (M H, M L, t s2, t 90, ΔM) and mechanical properties (TSb, Eb, hardness) of rubber vulcanizates. Organo-bentonite was mixed into a rubber blend in particular ratio of 5, 10, 15, 20 phr in various combination with silane (3-aminopropyl triethoxysilane), Perkasil and carbon black. The highest maximum torque values were obtained with the sample using 20 phr of silanized P130s. The tensile strength (TSb) values decreased with increasing P130 content, as well as non-silanized and silanized P130. However, when 20 phr P130s was used, value of TSb was higher. The most enhanced properties of rubber blends were found with the addition of 20 phr of silanized bentonite P130s.

Effects of Nonhydroxyl Oxygen Heteroatoms in Diethylene Glycols on the Properties of 2,5-Furandicarboxylic Acid-Based Polyesters.

With regard to polyesters based on biobased 2,5-furandicarboxylic acid (FDCA), our work presents a new strategy, heteroatom substitution, to adjust the thermal and gas barrier properties. The effects of nonhydroxyl oxygen heteroatoms in the diols on the properties of FDCA-based polyesters were first investigated by a combination of an experiment and molecular simulation. The results demonstrated that the introduction of oxygen heteroatoms significantly influenced the thermal and gas barrier properties. As for the two model polymers with a very similar skeleton structure, poly(pentylene 2,5-furandicarboxylate) (PPeF) and poly(diethylene glycol 2,5-furandicarboxylate) (PDEF), their Tg exhibited an obviously increasing order. Moreover, they showed similar thermal stability and thermal oxidative stability. Dynamic mechanical analysis, positron annihilation lifetime spectroscopy, and molecular dynamics simulation indicated that the gas barrier properties followed the sequence of PDEF > PPeF mainly due to the decreased chain mobility and smaller fractional free volume. In-depth analysis of the effects of heteroatom substitution has an important directive significance for the design and preparation of new high glass transition temperature or novel excellent gas barrier materials. Through the manipulation of different heteroatoms in the diols, the polyesters with varied properties can be expected.

Bond coat composition formed by spark plasma sintering for gradient material with thermal barrier properties

High-temperature materials for thermal barrier coatings (TBC) have important prospects for application in the aircraft engine industry. To increase the service life and reliability of superalloy parts, the bond coat (BC) in the structure of the TBC is of great importance. In this study, the architecture of the BC material between the superalloy and the external ceramics is proposed. It is shown that the BC layer can consist of a sublayer of intermetallic NiAl (VKNA) and a mixture of VKNA with 15 or 30 wt.% zirconium dioxide (8YSZ). This architecture allows us to form by spark plasma sintering (SPS) technique. In the work, samples of a gradient BC VKNA/VKNA+(15% or 30%)YSZ/YSZ were obtained using SPS at 1070 oC, a pressure of 30 MPa and an isothermal exposure of 5 min. In all sintered compositions the porosity did not exceed 2%. The structure of the BC material is characterized by scanning electron microscopy, energy-dispersion spectroscopy, and micro-durometry. It is shown that the SPS provides an adhesive connection of the sublayers in the BC layer and with the external ceramics. The microhardness increases li nearly during the transition from the VKNA layer to the YSZ layer through a BC with different YSZ content in the sublayer. The BC samples demonstrated a thermal conductivity gradient from the Inconel 625 substrate to YSZ and the influence of the YSZ content in the sublayers on the decrease in the coefficient of linear thermal expansion in the temperature range of 800–1000 oC was also determined. Damage to the ceramic surface during thermal cycling in air at 1100 oC, i.e. the appearance and development of cracks, is not more than 10% at 45 cycles.This research was carried out under Basic Scientific Research Assignment No. FSNM-2020-0026 of the Ministry of Education and Science of Russia and was funded by the Russian Foundation for Basic Research, Grant No. 19-48-590007.

Rational formulations of sustainable polyurethane/chitin/rosin composites reinforced with ZnO-doped-SiO2 nanoparticles for green packaging applications

Polysaccharide chitin (CH) was modified by antimicrobial natural gum rosin as a biocompatible agent within the thermoplastic polyurethane (TPU) elastomer to form the TPU/CH composite. This blend was then mixed with different ratios of ZnO-doped-SiO2 nanoparticles (ZnO-SiO2-NPs) to chelate chitin and to improve the properties of TPU nanocomposites. The topology and surface roughness of chitin and nanoparticles within the TPU matrix, besides their effect on the crystallinity degree of TPU were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). The TPU nanocomposites are subjected to different measurements such as mechanical, thermal, hydrophobicity, flammability, water vapor, and oxygen barrier properties, as well as antimicrobial activity. The results showed that the major properties were improved when the nanoparticles were added, especially at 5 wt%. Furthermore, the TPU/CH blend reinforced with high contents of NPs (i.e., 5–7 wt%) exhibited efficient antimicrobial activities against Gram-negative, Gram-positive bacteria and, pathogenic fungi.

Enhanced Polyester Degradation through Transesterification with Salicylates.

Polyesters constitute nearly 10% of the global plastic market, but most are essentially non-degradable under ambient conditions or in engineered environments. A range of degradable polyesters have been developed as more sustainable alternatives; however, limitations of practical degradability and scalability have hindered their viability. Here, we utilized transesterification approaches, including in situ polymerization-transesterification, between a salicylate and a polyester to incorporate salicylate units into commercial polyester backbones. The strategy is scalable and practically relevant given that high molar mass polymers can be obtained from melt-processing of commercial polyesters using common compounders or extruders. Polylactide containing sparse salicylate moieties shows enhanced hydrolytic degradability in aqueous buffer, seawater, and alkaline solutions without sacrificing the thermal, mechanical, and O2 barrier properties of the parent material. Additionally, salicylate sequences were incorporated into polycaprolactone and a derivative of poly(ethylene terephthalate), and those modified polymers also exhibited facile degradation behavior in alkaline solution, further expanding the scope of this approach. This work provides insights and direction for the development of high-performance yet more sustainable and degradable alternatives to conventional polyesters.

Thermal and Barrier Characterizations of Cellulose Esters with Variable Side-Chain Lengths and Their Effect on PHBV and PLA Bioplastic Film Properties.

Cellulose esters (CEs) are promising biodegradable substitutes for traditional petroleum-based plastic materials. Research on structure–property relationships of CEs is necessary to evaluate their suitability for industrial applications such as food packaging. Cellulose esters with different side-chain lengths were synthesized and studied. Their thermal and moisture barrier properties were characterized. Cellulose triheptanoate (CTH) was proved to have an optimal moisture barrier (WVTR = 0.31 g·mil/day/in.2) and was used to blend with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactic acid (PLA) bioplastics. CTH addition improved the PLA thermal stability, enhanced the ductility, and increased the moisture barrier by 32%, while it decreased the PHBV thermal stability, weakened the ductility, and reduced the moisture barrier by 90%. We demonstrated that by proper choice of the combination of CE and bioplastic, bioplastic blends with unique and useful synergistic properties can be obtained. These blends can potentially be used for commercial applications, such as biodegradable flexible packaging.

Reactive extrusion of biodegradable PGA/PBAT blends to enhance flexibility and gas barrier properties

AbstractAmong commercial biodegradable polyesters, poly(glycolic acid) (PGA) has been rarely investigated for packaging applications, despite its unique advantages such as 100% compostability, high degree of crystallinity, high thermal stability and high gas barrier properties. The application of PGA has been limited by its mechanical brittleness, moisture sensitivity, and high melting temperature (~240°C), restricting its processing and applications for film packaging. In this study, PGA was modified by blending with poly (butylene adipate‐co‐terephthalate) (PBAT) via melt‐extrusion. A commercial terpolymer of ethylene, acrylic ester and glycidyl methacrylate (EMA‐GMA) was selected for compatibilization. The phase morphology, rheology, thermal, mechanical and gas barrier properties of the blends were investigated. With addition of 20 wt. % EMA‐GMA, the elongation of PGA/PBAT (50/50 wt. %) blends was improved from 10.7% to 145%, the oxygen permeability was reduced from 125 to 103 (cm3 mm)/(m2 24 h atm), and the water vapor barrier performance was improved by ~47%. The enhancement in ductility, oxygen and water vapor barrier properties of the flexible blends were ascribed to the interfacial bonding between PBAT and PGA enabled by EMA‐GMA. The compatibilized PGA/PBAT blends with high thermal stability up to 300°C are preferable for high temperature or hot food packaging.

Central composite design based statistical modeling for optimization of barrier and thermal properties of polystyrene based nanocomposite sheet for packaging application

Synergistic effect of ZnO-nanoparticles as three-dimensional nanospheres and nanoclay as one-dimensional clay platelets, on thermal and barrier properties of polystyrene-based nanocomposite packaging sheet was investigated. A central composite design under response surface methodology was employed for optimizing the thermal and moisture barrier properties of sheet. Polynomial equations were fitted to the obtained experimental data of glass transition temperature (Tg), water vapor permeability (WVP) and water uptake (WU) using multiple regression analysis with a determination coefficient values of 0.94,0.81 and 0.93, respectively. At 1.16 % ZnO and 4.47 % nanoclay concentrations, the corresponding predicted response values for Tg, WVP and WU were 111.88 °C, 7.75 × 10−11 g/m.s.Pa and 0.37 %, respectively, which were confirmed by validation experiments. The presence of nanoclay in the polystyrene/ZnO-nanoparticles matrix and increasing its content, increased UV absorption of the nanocomposite, while having little effect on transparency. The incorporation of nanoparticles reduced the oxygen permeability of polystyrene sheet by up to 60 %.