Effect of hybrid hollow microspheres on thermal insulation performance and mechanical properties of silicone rubber composites

Hollow microspheres (HM) of ceramic, silica, and glass‐filled silicone rubber (SR) composites were prepared, and the effects of hybrid HM on thermal and mechanical properties of composites were investigated. The results indicate that hybrid HM can effectively improve the thermal insulation property of HM/SR composites. Especially, for sample 15S, the thermal conductivity and thermal degradation temperature reached 0.1273 W/m K and 521 °C (45 °C higher than that of neat SR), respectively. Besides, thermal insulation performance was improved, showing as a temperature of 103.2 °C after 15 min heating, which is 37.8 °C lower than that of SR. The tensile strength of composites was enhanced from 1.92 MPa at 11.56 vol % hollow silica microspheres (HSM) loading to 3.08 MPa at 21.88 vol % HSM loading. Moreover, the compressive strength was improved from 3.33 to 5.68 MPa by introducing more hollow ceramic microspheres into the matrix, in this case, from 7.79 to 15.33 vol %. Furthermore, the failure mechanism was analyzed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46025.     

High‐performance polymeric materials with greatly improved mechanical and thermal properties from cyanate ester/benzoxazine resin reinforced by silane‐treated basalt fibers

This present article investigates the effect of silane‐treated basalt fibers (TBFs) on the morphological, mechanical and thermal properties of cyanate ester/benzoxazine (CE/BOZ) resin composites. The characterization was made using a scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), flexural test, impact strength (IS) test, microhardness test, dynamic scanning calorimetry, and thermogravimetric analysis. The mechanical test results inferred the distinctive improvements in the values of the flexural strength and modulus, IS, and microhardness of the CE/BOZ composites. The thermal stabilities in terms of the T_g, T_5%, T_10%, and T_HRI were appreciably improved and were higher than those of the pure CE/BOZ resin. Data from the SEM and FTIR tests ascertained the good dispersion and adhesion between the TBFs and the resin matrix, which might be behind the significant enhancement in the ultimate performances of the composites, with respect to the distinguished properties of BFs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46283.     

Flexible and transparent polymer/cellulose nanocrystal nanocomposites with high thermal conductivity for thermal management application

Polymeric materials play important roles in semiconductor technology and modern electronic devices. However, the weak thermal management capability of polymer seriously restricts the service life, reliability, and efficiency of devices. Consequently, inorganic or metallic thermally conductive fillers are added into polymers to make up the low thermal conductivity, but the optical transparency and flexibility always decrease or even disappear. Herein, we report transparent polymer nanocomposites comprising poly(vinyl alcohol) (PVA) and cellulose nanocrystal (CNC) with highly lateral thermal conductivity [about 5.7 W/(m·K)]. Such a high thermal conductivity is attributed to the aligned structure of CNC in PVA matrix and hydrogen-bond interaction between CNC and PVA. All the organic nanocomposites also present excellent electrical insulating performance and tensile properties. The transparent and flexible nanocomposites are promising in the thermal management applications of displays, next-generation wearable devices, sensors, and LEDs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48864.     

Promotion of the mechanical properties and thermal conductivity of epoxy by low Si3N4 whisker content and its mechanisms

Si₃N₄ whisker (Si₃N_4w) is selected as epoxy filler. The influence of filler content on the bulk density, porosity, bending strength, Young's modulus, critical stress intensity factor, work of failure, morphologies of fracture surface, and thermal conductivity of Si₃N_4w/epoxy is investigated. The bending strength is 82.63 MPa at a Si₃N_4w content of 5 vol% and increases to 25.29% more than that of neat epoxy. Compared with that of neat epoxy, the work of failure and thermal conductivity increase by 455% and 34.78% to 18 248.92 J·m⁻² and 0.31 W·m⁻¹·K⁻¹, respectively, at a Si₃N_4w content of 7 vol%. However, Si₃N_4w/epoxy becomes sensitive to precrack due to a weak C N bond and residual tensile stress at the interface, thereby resulting in the decline of critical stress intensity factor. The coexistence of various energy dissipation mechanisms, namely, steps, craters or depressions, stress whitening, plastic flow, pull out of Si₃N_4w, and rough fracture surface, is observed in Si₃N_4w/epoxy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48721.     

The impact of polymer matrix blends on thermal and mechanical properties of boron nitride composites

To improve mechanical and thermal properties of a hexagonal boron nitride platelet filled polymer composites, maleic anhydride was studied as a coupling agent and compatibilizer. Injection molded blends of acrylonitrile butadiene styrene (ABS), high-density polyethylene (HDPE), and maleic anhydride with boron nitride filler were tested for thermal conductivity and impact strength to determine whether adding maleic anhydride improved interfacial interactions between matrix and filler and between the polymers. Adding both HDPE and maleic anhydride to ABS as the matrix of the composite resulted in a 40% improvement in impact strength without a decrease in thermal conductivity when compared to an ABS matrix. The best combination of thermal conductivity and impact strength was using pure HDPE as the matrix material. The effective medium theory model is used to help explain how strong filler alignment helps achieve high thermal conductivity, greater than 5 W/m K for 60 wt % boron nitride. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48661.     

Improving thermal conductivity and shear strength of carbon nanotubes/epoxy composites via thiol‐ene click reaction

This study investigates the effect of the thiol‐ene click reaction on thermal conductivity and shear strength of the epoxy composites reinforced by various silane‐functionalized hybrids of sulfhydryl‐grafted multi‐walled carbon nanotubes (SH‐MWCNTs) and vinyl‐grafted MWCNTs (CC‐MWCNTs). The results of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM) show that the sulfhydryl groups and vinyl groups are successfully grafted onto the surface of MWCNTs, after treatment of MWCNT with triethoxyvinylsilane and 3‐mercaptopropyltrimethoxysilane, respectively. Scanning electron microscopy (SEM), HotDisk thermal constant analyzer (HotDisk), optical microscope, and differential scanning calorimetry (DSC) are used to characterize the resultant composites. It is demonstrated that the hybrid of 75 wt % SH‐MWCNTs and 25 wt % CC‐MWCNTs has better dispersion and stability in epoxy matrix, and shows a stronger synergistic effect in improving the thermal conductivity of epoxy composite via the thiol‐ene click reaction with 2,2′‐azobis(2‐methylpropionitrile) as thermal initiator. Furthermore, the tensile shear strength results of MWCNT/epoxy composites and the optical microscopy photographs of shear failure section indicate that the composite with the hybrid MWCNTs has higher shear strength than that with raw MWCNTs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44579.     

Effect of polyphenylene sulfide containing amino unit on thermal and mechanical properties of polyphenylene sulfide/glass fiber composites

Three kinds of high‐molecular‐weight compatibilizers [copoly(1,4‐phenylene sulfide)‐poly(2,5‐phenylene sulfide amine)] (PPS‐NH₂) containing different proportions of amino units in the side chain) were synthesized by the reaction of dihalogenated monomer and sodium sulfide via nucleophilic substitution polymerization under high pressure. The intrinsic viscosity of the obtained copolymers was 0.354–0.489 dL/g and they were found to have good thermal performance with melting point (T_m) of 271.3–281.0 °C and initial degradation temperature (T_d) of 490.0–495.7 °C. There was an excellent physical compatibility between PPS‐NH₂ and the pure industrial PPS. The results of dynamic mechanical analysis and macro‐ and micromechanical test showed that the selective compatibilizer PPS‐NH₂ (1.0) (1.0% mol aminated ratio) can improve the mechanical and interfacial properties of polyphenylene sulfide/glass fiber (PPS/GF) composite. The macro‐optimal tensile strength, Young's modulus, bending strength, and notched impact strength of 5%PPS‐NH₂ (1.0)/PPS/GF composite raised up to 141 MPa, 1.98 GPa, 203 MPa, and 6.15 kJ/m², which increased 12.8%, 9.4%, 4.1%, and 13.8%, respectively, comparing with the pure PPS/GF composite (125 MPa, 1.81 GPa, 195 MPa, and 5.40 kJ/m², respectively). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45804.     

The effects of modified zinc oxide nanoparticles on the mechanical/thermal properties of epoxy resin

Characterized by its strength, durability, and thermal properties, epoxy resin has been widely used as an adhesive, paint, and coating in many applications in the aerospace, civil and automotive industries. Despite this, the thermoset polymer resin has been known for its brittleness and low fracture resistance. This study focuses on the reinforcement of an epoxy resin system (diglycidyl ether of bisphenol A) with zinc oxide (ZnO) nanoparticles in their pristine form and a further modified form. The modification took place in two ways: coating with polydopamine (PDA) and covalently functionalizing them with (3-aminopropyl)triethoxysilane (APTES) and (3-glycidoxypropyl)trimethoxysilane (GPTMS). Therefore, four different types of nanoparticles were used: pristine ZnO, ZnO/PDA, ZnO/GPTMS, and ZnO/APTES aiming to improve the interfacial bonding between the polymeric matrix and the reinforcement. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy characterization and imaging techniques were used to prove that the ZnO nanoparticles were successfully modified prior to manufacturing the epoxy composites. While tensile testing showed that using pristine ZnO increases the composite's strength by 32.14%, the fracture toughness of the resin was improved by 9.40% when reinforced with ZnO functionalized with APTES. TGA showed that the addition of functionalized nanoparticles increases the material's degradation temperature by at most 7.31 ± 4.9°C using ZnO/APTES. Differential scanning calorimetry and dynamic mechanical analysis testing proved that the addition of any type of nanoparticles increases the resin's glass transition temperature by as much as 7.83°C (ZnO/APTES).     

γ Irradiation effects on optical,thermal, and mechanical properties of polysulfone/MWCNT nanocomposites in argon atmosphere

Polymer‐based composites find use in many nuclear and space application for their ease of fabrication, tailor made properties and light weight. Certain polymers like PTFE, unfilled polyesters and polyamides are prone to degradation in presence of high energy radiation while polymers like epoxies, polyimides, and poly‐ether ether ketone have good stability to ionizing radiation. Incorporation of fillers like carbon nanotubes (CNTs) is likely to improve the radiation resistance of the polymers. In this work, polysulfone (PSU)‐based nanocomposites were fabricated using multiwalled carbon nanotube (MWCNT) by solution mixing process. The morphology of the PSU/ MWCNT nanocomposites films were studied using Field Emission Scanning Electron Microscopy (FESEM). The prepared films were subjected to γ radiation in an argon environment (to avoid the effect of air/oxygen). Different techniques were used to understand the radiation‐induced changes. Gel Permeation Chromatography (GPC) traces of neat PSU before and after exposure to radiation shows a decrease in molecular weight. Infrared spectroscopy shows changes in chemical structure. Differential Scanning Calorimetry (DSC) thermograms reveal dose‐related changes. For neat PSU, a decrease in T_g was observed with increase in dose. For PSU/ MWCNT nanocomposites, the increase in MWCNT content and dose (up to 1.5 MGy) increased the T_g. Thermo Gravimetric Analysis (TGA) showed a marginal decrease in thermal stability for pristine PSU as well as PSU/MWCNT nanocomposites with irradiation. Tensile strength increased with increasing MWCNT content but decreased with dose. Elongation at break decreased with MWCNT content as well as radiation dose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42017.     

Preparation of polyester resin/graphene oxide nanocomposite with improved mechanical strength

Graphene oxide (GO) has attracted huge scientific interest due to its unique physical and chemical properties as well as its wide‐scale applicability including facile synthesis and high yield. Here, we report preparation of nanocomposites based on GO and unsaturated polyester resin (PE). The synthesized samples were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and tensile strength measurements. A good dispersion of the GO sheets within the resin matrix was observed from the morphological analysis. A significant enhancement in mechanical properties of the PE/GO composites is obtained at low graphene loading. Around 76% improvement of tensile strength and 41% increase of Young's modulus of the composites are achieved at 3 wt % loading of GO. Thermal analysis of the composite showed a noticeable improvement in thermal stability in comparison to neat PE. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Electrically insulating ZnOs/ZnOw/silicone rubber nanocomposites with enhanced thermal conductivity and mechanical properties

In this work, hybrids of surface modified zinc oxide spherical (ZnOs) nanoparticles and tetrapod‐shaped whiskers (ZnOw) were incorporated into the silicon rubber (SR) to prepare the ZnOs/ZnOw/SR nanocomposites. The incorporation of the ZnOs/ZnOw facilitated the formation of three‐dimensional thermally conducting network. It was found that the thermal conductivity of the ZnOs/ZnOw/SR reached up to 1.309 W m^?1 K^?1 when the ZnOs/ZnOw content was 20 vol % (V_m‐ZnOs:V_ZnOw = 7:3), which was nearly 6.5 times that of the pristine SR. The dielectric and resistivity measurements showed that the incorporation of the ZnOs/ZnOw hybrids did not cause much change in the electrical properties. In addition, the results show that the tensile strength of ZnOs/ZnOw/SR nanocomposites is higher than that of pristine SR. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46454.     

Multilayered ultrahigh molecular weight polyethylene/natural graphite/boron nitride composites with enhanced thermal conductivity and electrical insulation by hot compression

A scalable strategy to fabricate thermally conductive but electrically insulating polymer composites was urgently required in various applications including heat exchangers and electronic packages. In this work, multilayered ultrahigh molecular weight polyethylene (UHMWPE)/natural graphite (NG)/boron nitride (BN) composites were prepared by hot compressing the UHMWPE/NG layers and UHMWPE/BN layers alternately. Taking advantage of the internal properties of NG and BN fillers, the UHMWPE/NG layers played a decisive role in enhancing thermal conductivity (TC), while the UHMWPE/BN layers effectively blocked the electrically conductive pathways without affecting the thermal conductive pathways. The in-plane TC, electrical insulation, and heat spreading ability of multilayered UHMWPE/NG/BN composites increased with the increasing layer numbers. At the total fillers loading of 40 wt%, the in-plane TC of multilayered UHMWPE/NG/BN composites with nine layers was markedly improved to 6.319 Wm⁻¹ K⁻¹, outperforming UHMWPE/BN (4.735 Wm⁻¹ K⁻¹) and pure UHMWPE (0.305 Wm⁻¹ K⁻¹) by 33.45% and 1971.80%, respectively. Meanwhile, the UHMWPE/NG/BN composites still maintained an excellent electrically insulating property (volume resistance~5.40×10¹⁴ Ω cm ; breakdown voltage~1.52 kV/mm). Moreover, the multilayered UHMWPE/NG/BN composites also exhibited surpassing heat dissipation capability and mechanical properties. Our results provided an effective method to fabricate highly thermal conductive and electrical insulating composites.     

Tailoring the structure of Kevlar nanofiber and its effects on the mechanical property and thermal stability of carboxylated acrylonitrile butadiene rubber

Water-dispersible hydrolyzed Kevlar nanofibers (hANFs) prepared by acid-assisted hydrothermal treatments of Kevlar nanofibers (ANFs) were first incorporated into carboxylated acrylonitrile butadiene rubber (XNBR) by a latex co-coagulation method. The obtained hANFs maintained the one-dimensional nanofibrous morphology and crystal structure as ANFs. There were amounts of polar groups appearing at the end of hANFs molecular chains after hydrothermal process, which led to the strong hydrogen bonding interaction between the filler and XNBR matrix. The results indicated that hANFs had significant reinforcement effects on the mechanical properties, crosslink density, and thermal stability of XNBR matrix. In comparison with those of neat XNBR, the tensile strength, tear strength, crosslink density, and maximum heat decomposition temperature (T_max) of XNBR/hANFs nanocomposites filled with 7 phr hANFs increased by 236%, 161%, 35%, and 19.64 °C, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47698.     

Facile preparation for gelatin/hydroxyethyl cellulose-SiO2 composite aerogel with good mechanical strength,heat insulation,and water resistance

The advanced thermal insulation materials with low cost and high mechanical properties play an important role in transport packaging and thermal protection fields. An inorganic/organic composite aerogel was prepared through hydrogen bonds and chemical crosslinking among silica aerogel particles, gelatin (GA), and hydroxyethyl cellulose (HEC). The as-prepared GA/HEC-SiO₂ composite aerogels were characterized by compression tests, scanning electron microscopy, Fourier transform infrared, thermogravimetric analyzer, and contact angle tests to investigate the chemical composition and physical structure. The GA/HEC-SiO₂ composite aerogels exhibited a strong mechanical strength (0.53–4.01 MPa), a high compression modulus (1.33–11.52 MPa), a lower volume density (0.035–0.081 g/cm³), thermal conductivity as low as 0.035 W/[m K]), a porosity of more than 93%, and hydrophobic angle as high as 150.01° after hydrophobic modification. These results indicate that biopolymer composite aerogels embedded with SiO₂ aerogel particles display a bright future in thermal insulation.     

外掺料对磷石膏基胶凝材料力学及导热性能的影响

将磷石膏应用于建筑业,可以解决磷化工副产物堆积的问题。采用单因素实验,通过改变水灰质量比、粉煤灰掺量、生石灰掺量等条件来研究各因素对磷石膏基胶凝材料力学性能及保温性能的影响,借助X射线衍射（XRD）、X射线荧光光谱（XRF）、扫描电镜（SEM）等手段来分析磷石膏基胶凝材料的物化性质和形貌结构。结果表明,磷石膏基胶凝材料的导热系数和抗压强度都与水灰质量比呈负相关,在水灰质量比为0.250时胶凝材料的抗压强度最大、水灰质量比为0.550时胶凝材料的导热系数最小;粉煤灰在磷石膏基胶凝体系中除了提供胶凝性能外,还会被生石灰激发出活性,增强胶凝体系的综合性能,粉煤灰掺量为50%（质量分数）时胶凝体系的综合性能最佳;生石灰在磷石膏基胶凝体系中对杂质的吸附效果明显,生石灰掺量超过7%（质量分数）以后对胶凝体系的保温性能和力学性能的增强效果明显。     

Transfer function and working principle of a pressure/temperature sensor based on carbon black/silicone rubber composites

Pressure/temperature sensitive silicon rubber (SR) filled with carbon black (CB) was prepared by a liquid mixing method. The transfer function of a pressure/temperature sensor based on CB/SR was derived by general effective media theory. The results show that the transfer functions coincided well with the experimental data, and the negative pressure coefficient of the resistance/positive temperature coefficient of resistance are shown. The working principles of these two kinds of sensors are different. The working principle of the pressure sensor based on CB/SR was related to the volume fraction of CB. With increasing volume fraction of CB, the working principle of this kind of pressure sensor varied from a piezo‐resistive effect to a strain effect. In addition, the working principle of the temperature sensor based on CB/SR was that the resistivity changed with temperature; this was not related to the volume fraction of CB. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42979.     

Study on the mechanical and thermal properties of polylactic acid/hydroxyapatite@polydopamine composite nanofibers for tissue engineering

Electrospun nanofibers have attracted tremendous attention because of their similar structure with extracellular matrix. In this work, the polydopamine (PDA) coating layer was first applied to modify hydroxyapatite (HA) nanoparticles and obtain functional HA@PDA nanoparticles. Subsequently, the polylactic acid (PLA)/HA@PDA composite nanofibers were prepared via electrospinning. The hydrophilicity and water absorption of PLA/HA@PDA composite nanofibers were larger than those of PLA and PLA/HA composite nanofibers. The thermal stability, static and dynamic mechanical properties of PLA/HA@PDA composite nanofibers significantly increased because the PDA coating layer on the surface of the HA nanoparticles acted like a glue-like transition layer, which led to an increase in interfacial adhesion between HA@PDA nanoparticles and the PLA matrix. The attachment and viability of mouse embryonic osteoblast cells (MC3T3-E1) cultured on the PLA/HA@PDA composite nanofibers were significantly increased compared with those cultured on the PLA and PLA/HA composite nanofibers. These results suggested that the PLA/HA@PDA composite nanofibers have superior mechanical and biological properties, which makes it potentially useful for tissue engineering scaffolds.     

Preparation,thermal and mechanical properties of poly (ether-imide) composite reinforced with carbon nanotube buckypaper

Vacuum filtration technique was employed in order to prepare multiwalled carbon nanotube buckypapers (MWCNT-BP) through a well-dispersed suspension of MWCNT/H₂O with the aid of Triton X-100 surfactant. The obtained BP (buckypaper) was then infiltrated with a solution of poly (ether-imide) (PEI) under vacuum conditions. The visual inspection demonstrated the importance of the centrifugation procedure before the vacuum filtration of the suspension, revealing a smooth surface of the as-prepared buckypaper. Thermogravimetric experiments (TGA) and scanning electron microscopy analyses have demonstrated the role of isopropyl alcohol in the removal of Triton X-100 from the nanotube network. SEM observations of the cross-section view of the samples revealed a porous network of the fabricated BP, and an impregnated structure of the PEI/BP composite, suggesting a good interfacial bonding between MWCNT and PEI. Moreover, significant improvements were achieved in mechanical and thermal properties of PEI matrix by the incorporation of BP, as the increase of both the storage modulus (42%) and the T _g (11 °C) for the PEI/BP composite. TGA have shown a significant increase in the onset decomposition temperature of the polymer by the incorporation of the BP. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48330.     

Highly filled multilayer thermoplastic/graphene conducting composite structures with high strength and thermal stability for electromagnetic interference shielding applications

Polyvinyl chloride (PVC)/graphene and poly(methyl methacrylate) (PMMA)/graphene nanocomposites were made by solution casting technique with graphene weight fractions of 1, 5, 10, 15, and 20%. Multilayer structures of the composites were made by hot compression technique to study their electromagnetic interference shielding effectiveness (EMI SE). Tensile strength, hardness, and storage modulus of the nanocomposites were studied in relation with graphene weight fraction. There has been a substantial increase in the electrical conductivity and EMI SE of the composites with 15–20% filler loading. Differential thermal analysis of the composites shows improved thermal stability with an increase in graphene loading. PMMA/graphene composites have better thermal stability, whereas PVC/graphene composites have superior mechanical properties. About 2 mm thick multilayer structures of PMMA/graphene and PVC/graphene composites show a maximum EMI SE of 21 dB and 31 dB, respectively, in the X band at 20 wt % graphene loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47792.