Processing and mechanical performance of 3D Cf/SiCN composites prepared by polymer impregnation and pyrolysis

The processing of 3D carbon fiber reinforced SiCN ceramic matrix composites prepared by polymer impregnation and pyrolysis (PIP) route was improved, and factors that determined the mechanical performance of the resulting composites were discussed. 3D C_f/SiCN composites with a relative density of ∼81% and uniform microstructure were obtained after 6 PIP cycles. The optimum bending strength, Young's modulus and fracture toughness of the composites were 75.2 MPa, 66.3 GPa and 1.65 MPa m^1/2, respectively. The residual strength retention rate of the as-pyrolyzed composites was 93.3% after thermal shock test at ΔT = 780 °C. It further degraded to 14.6% when the thermal shock temperature difference reached to 1180 °C. The bending strength of the composites was 35.6 MPa after annealing at 1000 °C in static air. The deterioration of the bending strength should be attributed to the strength degradation of carbon fibers and decomposition of interfacial structure.     

Thermal degradation behavior of polypropylene base wood plastic composites hybridized with metal (aluminum,magnesium) hydroxides

The effect of hybridization of wood fibers and metal hydroxides on the thermal stability of polypropylene (PP) based plastic composites is studied through thermo gravimetric analysis (TGA). The wood fiber increases thermal stability of the metal hydroxide hybridized WPC including aluminum hydroxide (AH) and magnesium hydroxide (MH). Hybridization with the AH increases decomposition temperature of the maximum loss rate (T_max) of the PP due to reinforcement of residue, but the onset‐temperature of the PP decomposition is nearly shifted. However, hybridization with the MH increases both the onset‐temperature and the T_max of the PP thermal degradation. Both AH and MH fillers increase the T_max of the PP matrix decomposition with increment of their contents. Besides, the MH case shows higher thermal stability of the PP resin in WPC decomposition than the AH case at the same loading level. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40120.     

Mechanical,thermal, and dielectric properties of SiCf/SiC composites reinforced with electrospun SiC fibers by PIP

Electrospun unidirectional SiC fibers reinforced SiC_f/SiC composites (e-SiC_f/SiC) were prepared with ∼10% volume fraction by polymer infiltration and pyrolysis (PIP) process. Pyrolysis temperature was varied to investigate the changes in microstructures, mechanical, thermal, and dielectric properties of e-SiC_f/SiC composites. The composites prepared at 1100 °C exhibit the highest flexural strength of 286.0 ± 33.9 MPa, then reduced at 1300 °C, mainly due to the degradation of electrospun SiC fibers, increased porosity, and reaction-controlled interfacial bonding. The thermal conductivity of e-SiC_f/SiC prepared at 1300 °C reached 2.663 W/(m∙K). The dielectric properties of e-SiC_f/SiC composites were also investigated and the complex permittivities increase with raising pyrolysis temperature. The e-SiC_f/SiC composites prepared at 1300 °C exhibited EMI shielding effectiveness exceeding 24 dB over the whole X band. The electrospun SiC fibers reinforced SiC_f/SiC composites can serve as a potential material for structural components and EMI shielding applications in the future.     

Thermal and biodegradation properties of poly(lactic acid)/fertilizer/oil palm fibers blends biocomposites

Poly(lactic acid) (PLA) and NPK fertilizer with empty fruit bunch (EFB) fibers were blends to produced bioplastic fertlizer (BpF) composites for slow release fertilizer. Thermal properties of BpF composites were investigated by thermogavimteric analysis (TGA), differential scanning calorimetry (DSC), and morphological and degradation properties were anlayzed by scanning electron microscopy (SEM), soil burial test, respectively. TGA themogram display that neat PLA, PLA/NPK, and BpF composites degradate at different temperatures. DSC curves of PLA and other composites exhibited same glass transition temperature (T_g) value indicating that both major blend components are miscible. The T_g, crystallization temperature (T_c), melting temperature (T_m) values also decreased with increased amount of fertilizer and fibers. The T_m of BpF composites did not change with an increase in fertilizer content because thermal stability of PLA and PLA/NPK composites was not affected. Soil burial and fungal degradation test of PLA, PLA/NPK, and BpF composites were also carried out. Soil burial studies indicated that BpF composites display better biodegradation as compared with neat NPK. Fungal degradation study indicated that fungi exposure times of BpF composites show higher value of degradation as compared with PLA/NPK. We attribute that developed BpF composites will help oil palm plantation industry to use it as slow release fertilizer. POLYM. COMPOS. 36:576–583, 2015. © 2014 Society of Plastics Engineers     

Roles of Calcium,Zinc, Copper and Titanium Compounds on the Degradation of Polymers

In this article, the influences of the metallic filler content upon the thermal degradability of polymer composites such as initial degradation temperature, maximum degradation temperature and char content have been critically reviewed using thermogravimetric analysis. Besides that, the review on the relationship between activation energies of polymer/metal composites, which was obtained from various degrade models, and the content of metallic fillers have also been defined. Other thermal properties such as glass transition temperature (T_g) and melting temperature (T_m) have also been reviewed based on the evaluation of differential scanning calorimetry (DSC) analysis.     

Morphological,mechanical, and thermal characterization of biopolymer composites based on polylactide and nanographite platelets

This work focuses on development and optimization of polylactide (PLA) and nanographite platelets (NGP) based composites to display possible superior mechanical and improved thermal stability. Melt blending and dry mixing methods of fabrication were employed at temperature of 180°C. Different Loading fractions of NGP were incorporated into polymer matrix. Morphological evaluation techniques such as XRD and TEM were applied to determine the degree of dispersion of NGPs into PLA matrix. Mechanical properties were evaluated and correlated to structural morphologies of PLA/NGP composites. Thermal properties of composites were studied to examine possible changes in T_g, T_c, T_m, and percentage crystallinity of these composites. The effect of mixing was also explored through double extrusion of some samples. It was concluded that composites containing 3 wt% NGP showed optimum mechanical performance without any significant changes in the thermal characteristics. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Thermal and dynamic mechanical behavior of bionanocomposites: Fumed silica nanoparticles dispersed in poly(vinyl pyrrolidone), chitosan,and poly(vinyl alcohol)

Various bionanocomposites were prepared by dispersing fumed silica (SiO₂) nanoparticles in biocompatible polymers like poly(vinyl pyrrolidone) (PVP), chitosan (Chi), or poly(vinyl alcohol) (PVA). For the bionanocomposites preparation, a solvent evaporation method was followed. SEM micrographs verified fine dispersion of silica nanoparticles in all used polymer matrices of composites with low silica content. Sufficient interactions between the functional groups of the polymers and the surface hydroxyl groups of SiO₂ were revealed by FTIR measurements. These interactions favored fine dispersion of silica. Mechanical properties such as tensile strength and Young's modulus substantially increased with increasing the silica content in the bionanocomposites. Thermogravimetric analysis (TGA) showed that the polymer matrices were stabilized against thermal decomposition with the addition of fumed silica due to shielding effect, because for all bionanocomposites the temperature, corresponding to the maximum decomposition rate, progressively shifted to higher values with increasing the silica content. Finally, dynamic thermomechanical analysis (DMA) tests showed that for Chi/SiO₂ and PVA/SiO₂ nanocomposites the temperature of β‐relaxation observed in tanδ curves, corresponding to the glass transition temperature T_g, shifted to higher values with increasing the SiO₂ content. This fact indicates that because of the reported interactions, a nanoparticle/matrix interphase was formed in the surroundings of the filler, where the macromolecules showed limited segmental mobility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characterization and thermal degradation kinetics of poly(l‐lactide) nanocomposites with carbon nanotubes

The purpose of this research was to study the thermal degradation kinetics of nanocomposites of poly(l ‐lactide) (PLLA) with carbon nanotubes (CNT) in order to provide further insight into their thermal stability. Nanocomposites were prepared by solvent casting with 1, 3, and 5% by weight of pristine CNT (P‐CNT) or functionalized CNT (F‐CNT), and were characterized using infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic‐mechanical‐thermal analysis. The kinetic parameters of thermal decomposition were determined employing Coats‐Redfern method to calculate the reaction order and E₂ function model to calculate the activation energy (Ea). We found no major changes in PLLA glass transition temperatures due to CNT presence, but melt‐crystallization temperature increased slightly in some composites. In general, composites consisting of 3% or 5% of F‐CNT had superior thermal stability than did pure polymer or P‐CNT composites. This improved thermal stability was revealed by slightly higher degradation and onset temperatures, and Ea obtained from kinetic analysis. In addition, 3% or 5% of F‐CNT in PLLA composites slightly enhanced the storage modulus above the glass transition. Therefore, functionalization promoted, in some extent, better morphology and dispersion of CNT into the matrix, which was responsible for improved thermal stability and thermomechanical performance of composites at higher temperatures relative to pure polymer. POLYM. ENG. SCI., 55:710–718, 2015. © 2014 Society of Plastics Engineers     

Structural,thermal, morphological and dynamic mechanical characteristics of waste‐reinforced polypropylene composites: A novel approach for recycling electronic waste

An in‐depth investigation has been carried toward utilizing polymer‐rich nonmetallic fraction of printed circuit boards (PCBs) as reinforcing fillers in polypropylene (PP) composites. The influence of waste additions (up to 25 wt %) on structural, thermal, morphological, and dynamic mechanical behavior of PP composites was investigated using a range of analytical techniques. The incorporation of PCB waste was found to affect the crystalline morphology resulting in the formation of smaller spherulites. The presence of glass fibers in PCB waste promoted the formation of β‐crystal enhancing the mechanical properties of composites. Thermal analysis showed a maximum increase of ～15 °C in the crystallization onset temperature (T_co) suggesting the nucleating effect of the filler, a feature also supported by structural investigations. Polarized microscopy revealed a reduction in the spherulite size after 5 wt % PCB waste loading owing to the presence of large number of nucleation sites. The incorporation of waste also increased the thermal stability of composites increasing the final degradation temperature by up to 14 °C. Dynamic mechanical properties of PP/PCB waste composites were determined in the temperature range ?20 to 155 °C; a significant increase in the storage modulus further confirmed the reinforcing effect of waste additives. This investigation has shown that the nonmetallic fraction of PCB waste could be used as a cost‐effective reinforcing filler for PP, providing an environmental friendly route to utilize electronic waste in value‐added products. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43389.     

Thermal degradation of polymethacrylic ester containing bisphenol-S

Thermal degradation of polymethacrylic ester containing bisphenol-S, poly(BPS-M), was investigated under nitrogen and air atmosphere at various heating rates. Ozawa's method was used to calculate the kinetic parameters, activation energy, preexponential factor and reaction order. Thermodegradation of the polymer occurs in one or two stages in nitrogen and air, respectively. The temperature at the start of intense degradation (T_start) and the temperature corresponding to a 50% mass loss (T_50%) were found to be 300 and 402°C, respectively, at a heating rate of 10°C min^?1 in nitrogen. Larger sample masses have a larger temperature interval (ΔT) and a greater mass loss (ΔW). The kinetic order of degradation is unity both in nitrogen and air. The direct pyrolysis mass spectrum of the polymer shows one degradation peak. The most important degradation process under inert atmosphere is the loss of carbon dioxide, phenol and sulphur dioxide. A possible mechanism for thermal decomposition of poly(BPS-M) is proposed based on the product analyses.     

Structural properties and mechanical behavior of injection molded composites of polypropylene and sisal fiber

Composites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L_(110)α, L_(040)α, L_(130)α and L_(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth.     

Schiff base‐substituted polyphenol: synthesis,characterisation and non‐isothermal degradation kinetics

BACKGROUND: Polymers of phenols and aromatic amines have emerged as new materials in fields such as superconductors, coatings, laminates, photoresists and high‐temperature environments. The stability, kinetics and associated pollution of the thermal decomposition of oligophenols are of interest for the aforementioned fields. RESULTS: A new Schiff base polymer, derived from N,N′‐bis(2‐hydroxy‐3‐methoxyphenylmethylidene)‐2,6‐pyridinediamine, was prepared by oxidative polycondensation. Characterisations using Fourier transform infrared, UV‐visible, ¹H NMR and ¹³C NMR spectroscopy, thermogravimetric/differential thermal analysis, gel permeation chromatography, cyclic voltammetry and conductivity measurements were performed. The number‐average (M_n) and weight‐average molecular weight (M_w) and dispersity (D = M_w/M_n) of the polymer were found to be 61 000 and 94 200 g mol^?1 and 1.54, respectively. Apparent activation energies of the thermal decomposition of the polymer were determined using the Tang, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Coats–Redfern methods. The most likely decomposition process was a D_n deceleration type in terms of the Coats–Redfern and master plot results. CONCLUSION: The mechanism of the degradation process can be understood through the use of kinetic parameters obtained from various non‐isothermal methods. Copyright © 2009 Society of Chemical Industry     

Properties of bamboo flour/high-density polyethylene composites reinforced with ultrahigh molecular weight polyethylene

In order to improve the properties of bamboo-plastic composites (BPCs), bamboo flour/high-density polyethylene (HDPE) composites were reinforced with ultrahigh molecular weight polyethylene (UHMWPE). The effects of UHMWPE on properties of composites were studied. The crystallinity of composites decreased slightly. Compared with non-UHMWPE added bamboo powder/HDPE composite, the composite with 6 wt % UHMWPE, showed decrease in water absorption to 0.41%, whereas its tensile strength and flexural strength increased to 34.51 and 25.88 MPa, respectively, a corresponding increase of 34.59 and 12.87%. The temperatures corresponding to initial degradation temperature (T_initial) and maximum degradation temperature (T_max) of the composite increased from 282.7 and 467.4 °C to 288.5 and 474.7 °C respectively. Scanning electron microscopic images showed that UHMWPE was well dispersed and fully extended as long fibers in the composite, forming a “three-dimensional physically cross-linked network structure,” which contributed to the improved properties of the composites. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48971.     

Investigation on the environmental-friendly poly(lactic acid) composites based on precipitated barium sulfate: Mechanical,thermal properties,and kinetic study of thermal degradation

A novel environmental-friendly poly(lactic acid) (PLA) composites based on precipitated barium sulfate (BaSO₄) were prepared via melt-compounding. The mechanical properties and thermal stability of PLA/BaSO₄ composites were investigated. To dig the decomposition mechanism, kinetic analysis of thermal degradation was emphasized systematically based on nonisothermal thermograms. Results showed that the mechanical responses were improved remarkably both under the quasi-static condition and subjected to high-speed shock due to the well-bonded interfaces between PLA and BaSO₄. Meanwhile, the added BaSO₄ suppressed the mass conversion rate of PLA phase and improved the thermal stability at high temperature. Due to the inhibition of BaSO₄, the calculated activation energy was enhanced obviously according to model-free isoconversional approaches. Finally, the apparent kinetic mechanism and reaction order for the over-all thermal degradation were determined by the combination of model-fitting approaches and Carrasco method. From this study, we hope to provide a facile method to prepare environmental-friendly PLA composites with excellent mechanical properties and thermal stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47995.     

Preparation and characterization of the copolymer containing N‐pyridyl bi(methacryl)imide unit

The copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide was prepared based on the reaction of polymethacrylic acid with 2‐pyridylamine. The molecular structure was characterized by ¹H‐NMR, FTIR, UV–Vis, and circular dichroism techniques. The physical properties of polymethacrylic acid change significantly after an introduction of 6 mol % N‐2‐pyridyl bi(methacryl)imide unit. In particular, the thermal degradation of the polymer was systematically studied in flowing nitrogen and air from room temperature to 800°C by thermogravimetry at a constant heating rate of 10°C/min. In both atmospheres, a four‐stage degradation process of the copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide was revealed. The initial thermal degradation temperature T_d, and the first, second, and third temperatures at the maximum weight‐loss rate T_dm1, T_dm2, and T_dm3 all decrease with decreasing sample size or changing testing atmosphere from nitrogen to air, but the fourth temperature at the maximum weight‐loss rate T_dm4 increases. The maximum weight‐loss rate, char yield at elevated temperature, four‐stage decomposition process, and three kinetic parameters of the thermal degradation were discussed in detail. It is suggested that the copolymer of methacrylic acid anhydride and N‐2‐pyridyl bi(methacryl)imide exhibits low thermal stability and multistage degradation characteristics. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1673–1678, 2002     

Thermal stability and kinetics analysis of epoxy composites modified with reactive polyol diluent and multiwalled carbon nanotubes

The effect of polyether polyol and amino‐functionalized multiwalled carbon nanotubes (NH₂‐MWCNTs) on the thermal stability of three‐phase (epoxy/polyol/NH₂‐MWCNTs) epoxy composites was investigated. Thermal stability and degradation characteristics of polyol/MWCNTs modified epoxy composites was evaluated using thermogravimetric analysis. The kinetics of thermal degradation was assessed from data scanned at 5, 10, and 20°C/min. Activation energy for degradation of epoxy nanocomposites was calculated using different differential and integral methods, that is, Kissinger's, Flynn–Wall–Ozawa, Coats–Redfern, and Horowitz–Metzger methods. In addition, the integral procedure decomposition temperature was determined to evaluate the inherent thermal stability of the modified composite system. Rate of thermal degradation in MWCNT/Polyol samples was found to be reduced significantly while activation energy of degradation was increased compared to unmodified epoxy composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41558.     

Effect of thermal exposure on the properties of phenolic composites: Dynamic mechanical analysis

Changes in the dynamic response of glass‐reinforced phenolic composites following thermal exposure at 180^oC for periods of time up to 28 days were monitored using dynamic mechanical analysis. Four phenolic resins were investigated: a resol/novolac blend, a phenolic–furan novolac/resol graft copolymer, a novolac, and a resol. Reactive blending and copolymerization of phenolic resins are currently being investigated to determine if these techniques will produce phenolic resins (and composites) that have improved impact properties and retain the excellent high‐temperature properties of resol and novolac phenolic resins. The results indicate that thermal aging at 180^oC for 1 day led to a more complete cure of all four phenolic resins as indicated by an increase in the temperature of the maximum of plots of both loss modulus (E″) and tan δ versus temperature. The storage modulus (E′) of the composites at 40^oC varied little following thermal aging at 180^oC for 1 day but decreased with increasing exposure time for samples aged 2, 7, and 28 days. Thermal aging led to an increase in E′ at higher temperatures and the magnitude of E′ at a given temperature decreased with increasing exposure time. The magnitude of E″ and tan δ decreased with aging time for all resins, although E″ and tan δ were larger for the blend and copolymer composites than for the novolac and resol composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 385–395, 2001     

Effect of SiO2 nanoparticles-decorated SCF on mechanical and tribological properties of cenosphere/SCF/PEEK composites

A silicon oxide (SiO₂) nanoparticles-decorated short carbon fiber (SCF) hybrid (SCF-SiO₂) was designed to improve the weak interfacial bonding between fibers and matrix. Nano-SiO₂ was grafted onto carbon fibers by introducing amino group and epoxy group on the surface of carbon fibers and SiO₂, respectively. The chemical composition of SCF-SiO₂ was analyzed by Fourier transform infrared spectrometer and energy-dispersive spectrometry, the microstructure of SCF-SiO₂ were investigated by scanning electron microscope, and then the hybrid filler was introduced into Poly(ether ether ketone) (PEEK). Due to the strong interfacial interaction between filler and matrix, the mechanical and tribological properties of SCF-SiO₂/PEEK composites were significantly better than SCF/PEEK composites. In order to further improve the tribological properties of the composites, micrometer-sized cenosphere (CS) particles were introduced into the aforementioned system to prepare multicomponent composites. The test results of friction and wear indicate that the CS/SCF-SiO₂/PEEK composites have the optimal tribological properties. Compared with pure PEEK, the friction coefficient of CS/SCF-SiO₂/PEEK composites under 200 N load decreases by 56.4% and the specific wear rate decreases by 87.4%. Meanwhile, the thermal decomposition temperature of CS/SCF-SiO₂/PEEK composites is increased by 40 °C compared to pure PEEK. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48749.     

Polypropylene/natural rubber composites filled with recycled newspaper: Effect of chemical treatment using maleic anhydride‐grafted polypropylene and 3‐aminopropyltriethoxysilane

A study on effect of chemical treatment using maleic anhydride‐grafted polypropylene (MAPP) and 3‐aminopropyltiethoxysilane (3‐APE) was investigated. The performance of the MAPP and 3‐APE were investigated by means of torque development, mechanical properties, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy morphology, and water absorption. The results revealed that the use of MAPP or 3‐APE in the composites has increased the stabilization torque, tensile strength, Young's modulus, water absorption, and thermal stability of the PP/NR composites. The incorporation of MAPP in the composites shows higher stabilization torque, tensile strength, E_B, Young's modulus, and lower water uptake when compared with the use of 3‐APE in the PP/NR composites. TGA and DSC results indicated that primary and secondary peak of DTG curve, initial degradation temperature (T₀), degradation temperature (T_deg), melting temperature (T_m), heat of fusion of composites (ΔH_f(com)), crystallinity of composites (X_PP), and PP (X_PP) increased, while total weight loss and thermal degradation rate decreased for both treated composites. The MAPP‐treated RNP‐filled PP/NR composites were found to be more thermal resistance and more crystalline than 3‐APE‐treated filled PP/NR RNP composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Role of Mn of PEG in the morphology and properties of electrospun PEG/CA composite fibers for thermal energy storage

As an aim toward developing novel class of form‐stable polymer‐matrix phase change materials for thermal energy storage, ultrafine composite fibers based on cellulose acetate and polyethylene glycol (PEG) with five different molecular weight (M_n) grades were prepared by electrospinning. The effects of M_n of PEG on morphology, thermal properties and mechanical properties of the composite fibers were studied by field emission scanning electron microscopy, differential scanning calorimetry, and tensile testing, respectively. It was found that the composite fibers were smooth and cylindrical shape, with the average diameters ranging from about 1000 to 1750 nm which increased with M_n of PEG. Thermal analysis results showed that the composite fibers imparted balanced thermal storage and release properties in different temperature ranges with the variation of M_n of PEG. Thermal cycling test indicated that the prepared composites had excellent thermal stability and reliability even they were subjected to 100 heating‐cooling thermal cycles. © 2009 American Institute of Chemical Engineers AIChE J, 2009