Thermal Stability Of Composites Research Articles

Strengthened high-temperature resistance in B4C/SiC/2024Al composite via SiC nanowires pinning grain boundary

Aiming at developing new B4C/Al neutron absorbing materials with both high thermal neutron absorption performance and high-temperature strength for neutron shielding applications, B4C/SiC/2024Al composites were fabricated by powder metallurgy process. TEM results revealed that SiC nanowires were distributed at Al grain boundaries and bonded tightly with Al matrix. Grain boundary sliding and grain rotation were efficiently restricted and prevented dislocation annihilation at GBs. The thermal stability of composite was improved by adding SiC nanowires and achieved a high-temperature strength of 163.4 ± 1.8 MPa at 573 K, which was increased by 92.2 % compared to the composite without addition of SiC nanowires. By analyzing the strengthening mechanism, dislocation strengthening was the dominant factor in the improvement of high-temperature strength. As for neutron absorption application, B4C/SiC/2024Al composite exhibited not only good high-temperature strength but also remarkable neutron absorption performance and matched thermal conductivity and coefficient of thermal expansion.

Fabrication of cellulose-based antimicrobial films integrated with in situ synthesized silver nanoparticles using Psidium guajava leaf extract

Cellulose-based antibacterial nanocomposite films were prepared by adding silver nanoparticles (AgNPs) synthesized in situ using a guava leaf extract. The nanocomposite films were synthesized using the solution casting method and characterized by analytical methods. The FTIR analysis indicated the presence of the carbonyl groups of guava leaf extract and hydroxyl groups of cellulose in the in situ synthesized AgNPs. The XRD analysis confirmed the AgNPs in the nanocomposites. SEM analysis revealed the presence of spherical AgNPs in the size range of 60-90 nm. The addition of AgNPs increased the tensile strength and thermal stability of composites. In addition, the cellulose-based nanocomposite film wasn’t showed very significant antibacterial activity against various foodborne pathogenic bacteria. Therefore, the prepared cellulose/AgNPs nanocomposite film is eco-friendly and exhibits excellent tensile strength and thermal stability along with a wide range of antimicrobial activity, so it is considered to be suitable for biomedical and food packaging applications.

Investigation of Thermal Decomposition and Thermal Oxidative Degradation of a Composite of Cellulose Nanofibers and Deproteinized Natural Rubber Grafted Methyl Methacrylate

Natural rubber (NR) is a polymer that has many applications in daily life. However, the traditional rubber industry relies heavily on petroleum-based materials, causing environmental pollution problems. Therefore, to reduce environmental challenges, products created from NR are combined with non-toxic chemicals and natural fillers such as cellulose nanofibers (CNF). This study presents the effect of CNF on the thermal properties of novel composites made from CNF and deproteinized natural rubber grafted methyl methacrylate (DPNR-g-MMA) under air and nitrogen atmosphere. Graft copolymerization of MMA onto DPNR to produce DPNR-g-PMMA was performed in the latex phase. The CNF/DPNR-g-PMMA composite was created by dispersing CNF in DPNR-g-PMMA at ratios of 0.5%, 1%, and 1.5% using ultrasonic waves. DPNR-g-PMMA was employed as the composite's matrix and CNF served as its reinforcing phase. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR) were used to confirm the success of the graft copolymerization. The thermal properties of materials were studied by Thermalgravimetric analysis (TGA) and Differential scanning calorimetry (DSC), in which the thermal stability of composites was examined via TGA under air and nitrogen atmosphere. The obtained data illustrate that, in comparison to DPNR and DPNR-g-PMMA, the decomposition temperature of all CNF/DPNR-g-PMMA composites, especially at CNF ratio of 1%. After blending CNF to DPNR-g-PMMA, the decomposition temperatures of CNF/DPNR-g-PMMA 1% increased by nearly 2 °C in nitrogen atmosphere and by 5.27 °C in air atmosphere. These results prove that the CNF is a key role in the thermal stability of DPNR-g-PMMA.

Material properties of spray‐dried cellulose nanocrystal reinforced homopolymer polypropylene composites

AbstractSpray‐dried cellulose nanocrystal (SDCNC) particles have attracted intense interest as reinforcements in polymer composites because of their unique physical and mechanical properties. This work aims to develop homopolymer polypropylene (HPP) composites with different loading levels of SDCNC particles (5, 10, 15, and 30 wt%) to understand their impact on composite mechanical, morphological, and thermal properties. The SDCNC‐reinforced HPP composites were manufactured using a C.W. Brabender bowl internal mixer with a masterbatch concept and an injection molding process. The mechanical, morphological, and thermal properties of the composites were investigated. Compared to pure HPP, the tensile, and flexural modulus of elasticity (MOE) of composites with 30 wt% SDCNC significantly increased by up to 67% and 49%. The impact strength of the composites with the absence of a compatibilizer significantly increased by up to 19%, which was attributed to the mechanical interlocking network established between SDCNC particles and HPP. Additionally, increasing SDCNC loading in the composites led to higher crystallization peak temperatures and increased the degree of crystallinity (especially at 30 wt% SDCNC content), indicating that the SDCNC particles can act as heterogeneous nucleating agents during the crystallization process. The thermal stability of the composite was slightly improved upon SDCNC introduction.Highlights With the incorporation of spray‐dried cellulose nanocrystal (SDCNC), the tensile modulus of elasticity (MOE), flexural MOE, and impact strength of filled homopolymer polypropylene (HPP) composites were significantly improved by up to 67%, 49%, and 19%, respectively. Mechanical interlocking network established between SDCNC and HPP contributed to the enhanced the impact strength. SDCNC particles can act as heterogeneous nucleating agents to promote the crystallization process of HPP. SDCNC particles slightly enhanced the thermal stability of HPP composite.

Thermal oxidation and compressive failure behavior of ZrSi2–B4C modified phenolic resin-based composite

Phenolic resin-based ablative materials have gained significant attention in the aerospace sector in recent years. In this study, TGA-DSC, FT-IR, XRD and XPS were employed to the thermal stability and phase transformation of the ZrSi2–B4C modified quartz fiber/boron containing phenolic resin (QF/BPR) composite. The compressive failure behavior of the composite at 600–1200 °C was studied through SEM and high-speed camera techniques. The results indicated that the compression strength of the composite decreased to a minimum at 600 °C and increased at 800–1200 °C. The composite exhibited different failure modes at different temperature: shear fracture at room temperature (RT), debonding of the fiber bundles at 600 °C, fiber buckling and fiber shear fracture at 800 °C, fiber buckling and delamination at 1000–1200 °C. The improvement in thermal stability of composite was primarily attributed to the formation of ZrO2, SiO2 and B2O3, which covered the fiber and effectively transmitted the load, leading to an enhanced strength of the interface between the fiber and resin.

Development of epoxy composites with graphene nanoplatelets and micro-sized carbon foam: Morphology and thermal, mechanical and tribological properties

The effect of graphene nanoplatelets (GNPs) and carbon foam (CF) micrograins on the morphology and thermomechanical and tribological properties of epoxy composites was determined. The binary composites containing separately CF grains or GNPs and multiphase composites with CF particles and GNPs together obtained by two procedures were studied. In the first method GNPs were dispersed initially in epoxy resin and then CF particles were introduced. In the second procedure, conversely, CF particles were distributed in polymer before GNPs addition. CF simultaneously applied with GNPs strongly improves storage modulus, hardness and thermal stability of composites and reduces the friction coefficient and the wear rate compared to epoxy matrix. The composite fabricated by the first method exhibited better tribological properties, especially considering the higher wear load.

Double percolation behavior through the preferential distribution of conductive black in polymer blends to boost electrical properties and EMI shielding effectiveness

The preferential distribution of the filler in the polymer blends leads to a lower percolation threshold in comparison to a single polymer matrix with random filler distribution. Poly(ethylene methyl acrylate) (EMA) and carboxylated acrylonitrile butadiene rubber (XNBR) composites of EMA-XNBR (EX) with a variable amount of conductive carbon black (Vulcan XC 72; VXC) has been prepared by conventional melt blending. These composites have superior electromagnetic interference (EMI) shielding effectiveness to attenuate the hazardous effects and save society from proliferating electromagnetic radiation. The suitable distribution of carbon black lowers the electrical percolation threshold of 12.5 phr by the formation of interconnected architecture following the two-step percolation phenomenon and results in an improved EMI SE of 33.5 dB. The morphological analysis demonstrates that the formation of a polymer-filler network of VXC in an EX technologically compatible blend increases the mechanical and thermal stability of composites by retaining their flexibility, which facilitates the application of EXV composites in techno-commercial fields.

Thermochemical behaviour, solidification, thermal stability and oxidation of Al-Mg2Si composites: An experimental and thermodynamic study

Effects of Mg and Si (Mg2Si) concentration on the thermochemical behaviour, solidification, thermal stability and oxidation of Al-Mg2Si composites have been investigated. Thermochemical behaviour, solidification characteristics and solid-liquid phase transformation of the composites have been simulated using FactSage™ 7.3 software and differential scanning calorimetry (DSC) heating and cooling curve analysis. The thermal stability of the composites has been investigated through thermogravimetric analysis (TGA) analysis. The oxides formation in Al-Mg2Si composites has been explored by FESEM-EDX analysis. In the hypoeutectic Al-Mg2Si composites, the α-Al nucleation temperature decreases with the increase in Mg2Si concentration, but in the hypereutectic composites, it increases with the increase in Mg2Si concentration in the composites. The reaction starting temperature between Mg and Si in molten composite increases with the increase in Mg2Si concentration. The Mg2Si solid-liquid transition initiation temperature decreases with the increase in Mg2Si concentration in the Al-Mg2Si composites. The Mg2Si acts as a barrier for the oxidation of Al up to the melting temperature of the composites which results in an improvement in the thermal stability of Al. Al2O3, MgO, SiO2, MgAl2O4 and AlFeMgOSi are the common oxides of Al-Mg2Si composites. With the increase in Mg2Si concentration, the Al2O3 and MgO oxides formation decreases and SiO2 and MgAl2O4 oxides formation increases in the Al-Mg2Si composites.

Noncovalent self‐assembled supramolecular aggregate decorated nickel‐aluminum layered double hydroxides nanosheets for reinforcing the flame retardancy of PLA

AbstractIn this work, an environmentally friendly and energy‐saving strategy to decorate Ni‐Al layered double hydroxides nanosheets (LDHs@PN) has been utilized to boost their flame retardancy and dispersion in the polymer. This proposed strategy was implemented through noncovalent self‐assembly supramolecular aggregate of phytic acid (PA) and 1,4‐bis(3‐aminoethyl) piperazine (AEP) onto NiAl‐LDHs surface in water without any organic solvent. The target product LDHs@PN was investigated by different characterization techniques. It was found that LDHs@PN was successfully fabricated possessing hydrophobic surfaces. In contrast, the surface of LDHs@PN became rough and exhibited a fluffy structure. Meanwhile, Ni, Al, P and N were homogeneously distributed on the surface of LDHs@PN. Significantly, after introducing LDHs@PN into biobased polylactic acid (PLA) via melting‐blending, the thermal stability of composites was improved compared to that of pure PLA and LDHs@PN promotes the formation of composite residual carbon. In addition, the PLA/LDHs@PN composite with 20 wt% loadings reached V‐0 rating in the UL‐94 test and achieved 30.1% limiting oxygen index value, indicating LDHs@PN significantly increased the flame retardant performance of the PLA. The flame retardant mechanism of LDHs@PN in the PLA matrix was analyzed. This facile, low‐cost and eco‐friendly decorating strategy is promising for industrial production.

A novel degradable sealing material for the preparation of dissolvable packer rubber barrel

To develop dissolvable packer rubber barrel is a key technology for realization of green oil drill engineering. During this experiment, a novel degradable rubber sealing material from MPUR/HNBR composite was prepared by physical mixing and chemical cross-linking with different parts of HNBR. The effect of blending ratio on the vulcanization characteristics, mechanical properties, compatibility, thermal stability, and dissolution characteristics of the composites were investigated. The results showed that when the MPUR/HNBR blend ratio changed from 80/20 to 60/40, the cross-linking degree of composites decreased gradually and the mechanical properties decreased. MPUR and HNBR have compatibility properties in a certain blending range, and the addition of HNBR led to an improvement in the thermal stability of composites. When immersed in a water medium at 100 °C, the tensile strength of pure MPUR decreased sharply in 12 h from 30 MPa to 3 MPa, its short service life time didn’t meet the need of engineering. After composed by HNBR, the tensile strength retention increased from 27.0% to 52.1% immersion for 24 hours. In addition, the composite can maintain high tensile strength between 48 and 168 h, its superior long service life time fully meet the sealing requirements. The possible degradable mechanism in water medium was offered.

Novel grasshopper protein/soy protein isolate/pullulan ternary blend with hesperidin derivative for antimicrobial edible film

As a green agricultural resource and a new alternative protein, edible insects have the potential to become an excellent source of biopolymer. In this study, a new ternary blend composites were formed based on the mixture of edible grasshopper protein and soybean protein isolates by adding pullulan (PUL). The combined effect of incorporation of antimicrobial agent methyl hesperidin (2.5 %, 5 %, 7.5 % and 10 %) was investigated. The addition of PUL can greatly improve the tensile strength of protein blend composites but has no positive impact on elongation at break. 5 % methyl hesperidin can further increase tensile strength to 7.36 MPa with no deterioration on elongation at break. The SEM and XRD results showed good compatibility between PUL and protein blend. The WVP and WCA results showed that the hydrophobicity of composites increased slightly. Moreover, thermal analysis presented that the thermal stabilities of composites were impaired. The increasing of methyl hesperidin content enhanced antibacterial activity against E. coli and S. aureus of ternary blend film, proving its application value as active packaging.

Fabrication and mechanical/thermal properties of composites from cotton linter and urea formaldehyde resin

The aim of this study is to prepare composite from commercial valueless cotton linter cellulose (CLC) of textile mills and garment industries, and urea formaldehyde (UF) resin. The alkali-treated cellulose (ATC), bleached cellulose (BLC) and microcrystalline cellulose (MCC) have been prepared from CLC. A novel fabrication method of CLC, ATC, BLC and MCC reinforced with urea formaldehyde resin has been developed. These composites are subsequently subjected to evaluation of their mechanical (tensile, flexural, hardness) and thermal (TGA, DTA, DTG) properties. The MCC-UF composites show the highest tensile strength (TS), flexural strength (FS) and Vickers micro hardness number (VHN) having the corresponding values 48.09 MPa, 34.05 MPa and 521.33 VHN respectively. The lowest mechanical values are found for CLC-UF composites (TS 32.96 MPa, FS 21.28 MPa and VHN 201.00). It is also revealed that the mechanical properties of the composites increase with the increase in fibre loading up to 5% and beyond this loading, these values are decreased. The morphological changes in flexural fractured surface are clearly observed by scanning electron microscopy measurement. The thermal stability of the composites is influenced by the filler content. The thermal stability of MCC-UF composite is found slightly higher than those of other composites.

Cardanol and bisphenol-F based benzoxazines with zirconium phosphate reinforced composites coating for protecting the mild steel surface from corrosion

The present work is to develop and characterize the benzoxazines from cardanol and bisphenol-F with imdazole core based amine in order to utilize them in the form of (50/50 wt%) blended composites coating for corrosion resistance application. The benzoxazine blends were reinforced with varying weight percentages of (0.5, 1, 1.5, 2.0 and 2.5 wt%) of 3-glycidoxypropyltrimethoxysilane (GPTMS) functionalized zirconium phosphate (ZrP) to obtain respective composites blended coatings. The thermal stability of composites was studied by thermogravimetric analysis (TGA). In order to ascertain their hydrophobic behavior the water contact angle studies were carried out and the values obtained for 0.5, 1, 1.5, 2.0 and 2.5 wt% GPTMS functionalized ZrP reinforced (50/50 wt% of C-ima/BF-ima) benzoxazines blended composites are 114,116,117,119,120 and 123° respectively. The UV shielding behavior of ZrP reinforced polybenzoxazine blended composites material was also studied by UV-Vis spectroscopic technique and the results obtained infer that these materials possess good UV shielding behavior. ZrP reinforced benzoxazine blended composites were coated on the mild steel specimens and their corrosion resisting behavior was studied. Results of Nyquist plot and Tafel plot, ascertain that among the coated specimens, the specimen coated with 2.5 wt% ZrP reinforced poly(C-ima/BF-ima) blended composites exhibits highest corrosion resisting efficiency.

Preparation and characterization of a graphene hybridizing polyurethane damping composite

Abstract A graphene hybridizing polyurethane/polyethyl methacrylate (GR-PU/PEMA) damping composite was synthesized using the sequential interpenetration method. The effects of the graphene content and the microphase separation structure on the damping properties, thermal stability, and mechanical properties have been studied in detail. The dynamic mechanical analysis indicated that graphene could improve the damping peak value of PU/PEMA, and the microphase separation structure could be beneficial for broadening the damping temperature range. The damping peak (tan σ max) of PU/PEMA hybridizing with 0.5 wt% graphene reached 0.82, and the temperature range of the loss factor (tan σ ≥ 0.3) was expanded to 88.3°C. Analysis of scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering reveals that graphene is uniformly dispersed in the polymer matrix, and the composite with interpenetrating polymer network (IPN) shows more microphase separation structures. Fourier transform infrared analysis indicated that there is strong interaction between graphene and IPN matrix. Furthermore, the addition of graphene improved the mechanical properties and thermal stability of composites.

Artificial silicide barrier coatings in titanium matrix composites

Abstract A continuous S2 silicide ([Ti,Zr] x Si y ) segregation layer was found in the fibre matrix interface of SCS6-SiC/Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si (IMI834) composites (composition in wt.%). The S2 layer separates completely the titanium matrix from the reaction layer. It was shown that the S2 layer stabilises the interface during thermal treatment. The thermal stability of composites was tested in which artificial coatings were introduced into the interface. For the artificial coatings a composition and structure of the S2 silicides were aspired. The interface of the composites was investigated with analytical transmission electron microscope in the as-processed condition and annealed at 700 °C for 3 000 h and at 800 °C for 1000 h. The coatings of the same composition and structure can be introduced into the interface of SiC-SCS6/IMI834 composites as those of the S2 silicide obtained by self-segregation. The composites with the artificial coatings have a similar interface stability at 700 °C as those obtained by self-segregation.

SYNTHESIS AND CHARACTERIZATION OF SOME MODIFIED NATURAL NANOCOMPOSITE POLYMERS AND STUDY THEIR THERMAL AND MECHANICAL PROPERTIES

Dextrin, tannic acid and different proportions of silver nanoparticles (AgNPs) are used to prepare novel materials. The functional and morphological characterization of the prepared nanocomposites was carried out by using Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM). The mechanical strength (Impact,compressing, hardness, and swelling behavior) of composite were evaluated. The thermal stability of composites was evaluated. The addition of AgNPs to the polymer blend matrix improves the physicochemical of the matrix. Due to the cross-linking motion of AgNPs, it is found that the swelling degree slightly decrease. The composite containing AgNPs becomes effective in increasing thermal stability.

Thermal degradation behavior and structures of thermoplastic cassava starch/sisal fiber composites

AbstractThe thermoplastic cassava starch (TPS)/sisal fiber (SF) composites were prepared by melt blending. The effects of SF content and its surface treated by sodium hydroxide (NaOH) and silane coupling agent (KH550) on the thermal degradation behavior and structures of TPS were investigated by thermogravimetric‐mass spectrometry (TG‐MS), Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and nuclear magnetic resonance (NMR). The thermal decomposition temperatures of TPS/SF composites increase with the SF content. The thermal decomposition products of TPS/SF composites are mainly methane, H2O, acetylene, formaldehyde, methanol and CO2. The thermal stability of composites containing SF treated by NaOH is better than that of KH550. TPS/SF composites show A + V types crystal, and the sample containing SF treated by NaOH has the highest V type crystal. The experimental results reveal that the content and the surface of SF play an important role in the thermal stability and structures changes of TPS/SF composites.

Enhanced dielectric and thermal properties of thermoplastic polyurethane/multi-walled carbon nanotube composites

Thermoplastic polyurethane (TPU) composites embedded with multi-walled carbon nanotube (MWCNT) of different loadings as a filler were synthesized by melt mixing method. These composites were characterized by Fourier Transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) technique. A considerable peak shift in FTIR was not seen, proving the absence of a chemical interaction between the matrix and the filler. The crystallinity of the composite almost doubled with that of neat as evidenced by XRD analysis. The morphological characterization of composites was done by scanning electron microscope (SEM) which proved the fine dispersion of MWCNT on TPU at lower loadings up to 3 w% while agglomeration started on further increase in the filler loadings. Dielectric studies of the composites showed a significant increase in dielectric properties which is due to the increased mobility of polymer chains. The ac conductivity of the composites also showed a gradual increase with an increase in filler loadings. Thermogravimetric analysis (TGA) revealed a considerable increase in the thermal stability of composites up to 3% MWCNT in comparison with neat.

Mechanical and thermal characterization of tungsten particulate reinforced epoxy polymer composites

Polymer matrix composites find a wide range of industrial applications due to its unique properties like lightweight, improved strength and the properties could also be tailored to suit specific applications. In this present work, a new class of polymer matrix composites with epoxy resin as matrix and tungsten metal particles as fillers were developed. The influence of the addition of tungsten fillers on mechanical and thermal properties of the composites has been investigated. The composites are fabricated by hand lay-up method and the specimens containing tungsten particle content by 1%, 3%, 5%, 7% and 9% by weight were developed. The developed specimens were subjected to mechanical and thermal investigations. Mechanical behavior was analyzed by conducting a flexural test and hardness as per ASTM standards. Thermal behavior was analyzed by conducting Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) of the developed composites. The results show that the addition of 7 wt. % filler has a higher value of flexural strength and hardness. Further addition of particulate fillers deteriorates the flexural strength and hardness due to agglomeration of filler content in the epoxy. Analysis by TGA and DSC shows that the thermal stability of composites is improved by increasing the addition of tungsten content in the epox.

The effect of graphene oxide on thermomechanical and permeability properties of poly(dimethyl siloxane) composites

The effect of graphene oxide (GO) on the properties of composites withhydroxyl-terminated poly(dimethyl siloxane) (PDMS) matrices, prepared by solution mixing, using tetrahydrofuran (THF) as a solvent, were examined. Viscosity measurements during the vulcanization reaction, usinga Brookfield viscosimeter, revealed that GO increases the viscosity of the system, in comparison with the unreinforced PDMS, proportionally to its concentration. The calculation of D and G bands ratio (ID/IG) at 1350 and 1580 cm−1 respectively, using RAMAN spectroscopy, showed more defects in graphene nanoplatelets incorporated in the PDMS nanocomposites. By Differential Scanning Calorimetry (DSC), a slight decrease in glass transition and melting temperatures of PDMS was observed. The thermal stability of composites was significantly improved, especially at higher GO concentrations (0.5 and 1 phr), as it was detected by thermogravimetric analysis (TGA). Also, the tensile strength of composites was enhanced, up to 113%, for samples reinforced with 1 phr GO. The elongation at break was increased, whereas no effect on the modulus of elasticity was observed. A decrease in oxygen permeability of 38% and 15% was measured in membranes made ofcomposites containing 0.5 phr and 1 phr GO respectively. The increase in swellingafter immersion of composites in toluene was explained by the fact that this phenomenon is not only related with the crosslinking density of the elastomer but alsowith the increased absorption properties of GO particles, due to the sonication treatment in THF during the preparation process of the composite, which might contribute to this effect.