Excellent Thermo-mechanical Properties Research Articles

A novel ultra-light bio-based fiberboard from mexican feather grass for thermal and acoustic insulation in green building construction applications

The use of natural fibers as raw materials for insulation fiberboard production is emerging as a strategy to replace wood fibers. This study developed an ultralightweight natural fiber insulation core fiberboard (CFB) with high mechanical strength, hygroscopic resistance, and excellent acoustic and thermal insulation properties. This study examined the production of CFB, which utilizes Mexican feather grass fibers with an epoxy resin binder across a range of densities of 0.18–0.36 g∙cm−3. Furthermore, the impact of incorporating a reinforcing skin layer of woven glass fibers on the core fiberboard's physical, mechanical, acoustic, and thermal properties was evaluated. All the fiberboard samples exhibited excellent thermal conductivity values (0.048–0.057 W/mK), which increased with increasing panel density (0.18–0.36 g∙cm−3). In addition, all of them displayed superior mechanical properties following the ASTM C208 standard. In terms of climatic resistance of the fiberboards, the results displayed excellent water resistance, exhibiting minimal humidity content (<5 %), thickness swelling (<6.5 %), and a hydrophobic surface, as indicated by the high-water contact angle (>121.96 at 30 s). Sound reduction exhibited a frequency-dependent tendency, with denser and sandwich fiberboards showing greater sound reduction of up to 27.9–36.56 dB at 3150 Hz for CFB-0.36 and SFB-0.52, respectively. Following ASTM C208, both core fiberboards and those coated with woven glass fiber skins (sandwich fiberboards, SFB) met the thermomechanical property requirements for regular and structural wall sheathing applications, respectively. These findings highlight the potential of Mexican feather grass as a bio-based alternative to wood, enabling the production of eco-friendly ultralightweight fiberboards with excellent thermomechanical properties suitable for building construction, such as regular and structural wall sheathing applications and ceiling decorations.

Solvent-free Acrylate/BCB drop-on-demand (DOD) inkjet dielectric ink for 3D printing

Currently, drop-on-demand (DOD) inkjet-printed dielectric inks used to produce next-generation high-frequency electronic devices fail to meet the requirements of circuit board substrates in terms of thermal, mechanical, and dielectric properties. To address this gap, we synthesized a low-viscosity acrylate monomer featuring an intrinsically low dielectric structure (hexafluorobisphenol A) and multiple cross-linking sites, and a benzocyclobutene monomer with low curing shrinkage and excellent thermomechanical properties. By mixing these monomers with other reactive diluents and verifying them through theoretical calculations and printing, we have developed a range of dielectric inks suitable for inkjet 3D printing. To enhance the overall performance of the cured inks, a sequential UV/thermal curing strategy was employed to form interpenetrating networks (IPNs). The optimal ink formulations met the requirements of circuit board substrates, demonstrating excellent heat resistance (Td5% = 334 °C, Tg = 181 °C), mechanical properties (tensile strength = 85 MPa, elongation at break = 13.5 %), and dielectric properties (Dk = 2.526 and Df = 0.113 at 15 GHz). These formulations meet the performance requirements for circuit board substrates and lead the industry in mechanical and dielectric properties. Furthermore, the feasibility of inkjet printing heterogeneous integrated electronic devices was verified, showing excellent print resolution and continuity of the conductive network. This work provides new insights into the future development of dielectric materials for inkjet 3D printing.

Prediction of tool wear and surface finish using ANFIS modelling during turning of Carbon Fiber Reinforced Plastic (CFRP) composites

Carbon fiber-reinforced plastics (CFRP) are widely used in various industries due to their high strength to weight ratio, corrosion resistance, durability, and excellent thermo-mechanical properties. The machining of CFRP composites has always been a challenge for the manufacturers. In this study, CNC turning operation with coated carbide tool is used to machine a specific CFRP and the relationship between the cutting parameters (Speed, Feed, Depth of Cut) and response parameters (Vibration, Surface Finish, Cutting Force and Tool Wear) are investigated. An adaptive-network-based fuzzy inference system (ANFIS) model with two multi-input–single-output (MISO) system has been developed to predict the tool wear and surface finish. Speed, feed, depth of cut, vibration and cutting force have been used as input parameters and tool wear and surface finish have been used as output parameters. Three sets of cutting parameter have been used to gather the data points for continuous turning of CFRP composite. The model merged fuzzy inference modeling with artificial neural network learning abilities, and a set of rules is constructed directly from experimental data. This model is capable of predicting the cutting tool wear and surface finish during turning of CFRP composite. The predicted tool wear and surface finish data are compared to the experimental results. The predicted data agreed well with the actual experimental data with 98.96 % accuracy for tool wear and 99.61 % accuracy for surface finish.

The Development of Poly(lactic acid) (PLA)-Based Blends and Modification Strategies: Methods of Improving Key Properties towards Technical Applications-Review.

The widespread use of poly(lactic acid) (PLA) from packaging to engineering applications seems to follow the current global trend. The development of high-performance PLA-based blends has led to the commercial introduction of various PLA-based resins with excellent thermomechanical properties. The reason for this is the progress in the field of major PLA limitations such as low thermal resistance and poor impact strength. The main purpose of using biobased polymers in polymer blends is to increase the share of renewable raw materials in the final product rather than its possible biodegradation. However, in the case of engineering applications, the focus is on achieving the required properties rather than maximizing the percentage of biopolymer. The presented review article discusses the current strategies to optimize the balance of the key features such as stiffness, toughness, and heat resistance of PLA-based blends. Improving of these properties requires molecular structural changes, which together with morphology, crystallinity, and the influence of the processing conditions are the main subjects of this article. The latest research in this field clearly indicates the high potential of using PLA-based materials in highly demanding applications. In the case of impact strength modification, it is possible to obtain values close to 800 J/m, which is a value comparable to polycarbonate. Significant improvement can also be confirmed for thermal resistance results, where heat deflection temperatures for selected types of PLA blends can reach even 130 °C after modification. The modification strategies discussed in this article confirm that a properly conducted process of selecting the blend components and the conditions of the processing technique allows for revealing the potential of PLA as an engineering plastic.

A Spironolactone-Based Prototype of an Innovative Biomedical Patch for Wound Dressing Applications.

The electrospinning process is an effective technique for creating micro- and nanofibers from synthetic and natural polymers, with significant potential for biomedical applications and drug delivery systems due to their high drug-loading capacity, large surface area, and tunable release times. Poly(L-lactic acid) (PLLA) stands out for its excellent thermo-mechanical properties, biodegradability, and bioabsorbability. Electrospun PLLA nanofibrous structures have been extensively investigated as wound dressings, sutures, drug delivery carriers, and tissue engineering scaffolds. This study aims to create and characterize electrospun PLLA membranes loaded with spironolactone (SP), mimicking active compounds of Ganoderma lucidum (GL), to develop a biodegradable patch for topical wound-healing applications. GL, a medicinal mushroom, enhances dermal wound healing with its bioactive compounds, such as polysaccharides and ganoderic acids. Focusing on GL extracts-obtained through green extraction methods-and innovative drug delivery, we created new fibers for wound-healing potential applications. To integrate complex mixtures of bioactive compounds into the fibers, we developed a prototype using a single pure substance representing the extract mixture. This painstaking work presents the results of the fabricating, wetting, moisture properties, material resilience, and full characterization of the product, providing a robust rationale for the fabrication of fibers imbued with more complex extracts.

Rapid and inexpensive synthesis of liter-scale SiC aerogels

Ceramic aerogels are promising materials for thermal insulation and protection under harsh environments. Yet current synthesis methods fail to provide an energy-, time-, and cost-effective route for high-throughput production and large-scale applications, especially for non-oxide ceramic aerogels. Here we reported a way to synthesize SiC aerogels within seconds and over liter scale, with a demonstrated throughput of ~16 L min−1 in a typical lab experiment. The key lies in renovated combustion synthesis and a fast expansion from powder reactants to aerogel products over 1000% in volume. The synthesis process is self-sustainable and requires minimal energy input. The product is very cheap, with an estimated price of ~$0.7 L−1 (~$7 kg−1). The obtained SiC aerogels have excellent thermo-mechanical properties, including low thermal conductivity, high elasticity, and damage tolerance. Our invention not only offers a practical pathway for large-scale applications of ceramic aerogels, but also calls for rethinking of combustion synthesis in one-step conversion from raw chemicals to bulk products ready for practical applications.

Bio-based polyurethane vitrimer with imine bonds: Excellent thermo-mechanical properties and heat recovery

Preparation of vitrimer with excellent performance from biomass feedstock can effectively reduce the waste of fossil fuels and the pollution problem to the environment. In this paper, vanillin (VAN) and 4-amino-3-methylphenol, which are biobased raw materials, were used to prepare the imine-bonded diol AMV-OH in a one-step process, which was incorporated into the main chain of vitrimer polymer, and a series of imine-bonded vitrimer materials AMV-V was obtained by using pentaerythritol tetra-3-mercaptopropionate (PETMP) as a cross-linking agent. The mechanical property analysis, solvent resistance analysis, DSC thermal analysis, DMA analysis and self-repair characterization showed that AMV-V exhibited good thermo-mechanical properties (the highest initial degradation temperature was 246 °C with a Tg value of 17 °C). The results showed that specific mechanical properties could be obtained by adjusting the contents of PETMP and AMV-OH, among which the best tensile properties were obtained at 10 mmol of AMV-OH, with a tensile strength of 8.03 MPa and an elongation at break of 316.79 %. Meanwhile, the AMV-V samples were able to achieve self-healing properties under milder conditions (100 °C, 10 MPa repair for 1 h) and had a high self-healing efficiency (H=94.80 %, R=83.72 %).

Aromatic nitrile resins with improved processability and thermal properties prepared by collaborative design of structure and blending strategy

The contradiction between processability and thermal properties has been limiting the development of high-performance thermoset resins, especially aromatic nitrile resins (AN). A new AN resin blend of 2-(3-(3,4-dicyanophenoxy)phenyl)-1H-imidazole-4,5dicarbonitrile (PNDCI) and 4-(4-aminophenoxy) phthalonitrile (APN) named PAB based on Brønsted acid-base blending strategy and introduction of asymmetric structure was designed and prepared in this paper. A series of characterizations showed that the PAB has not only excellent processability with a diminished melting point (118°C), wider processing window (90°C), and high curing reactivity, but that the cured PAB resins (C-PAB) also possessed high glass transition temperature (477°C), excellent long-term thermo-oxidative stability, thermomechanical properties and dimensional stability. The present design strategy of blending resins provides PAB as a good reference material for achieving a good balance between processability and high-temperature resistance.

Adaptable Polyurethane Networks Containing Tertiary Amines as Intrinsic Bond Exchange Catalyst

AbstractVitrimers exhibit unique properties, such as thermal recyclability akin to thermoplastics, while structurally mirroring thermosets in terms of strength, durability, and chemical resistance. However, a significant limitation of these materials is their dependence on an external catalyst. Consequently, this research aims to develop vitrimer materials that incorporate an intrinsic catalyst, thus maintaining excellent thermomechanical properties and recyclability. Polyaddition polymerization is employed to synthesize the desired polymer, incorporating a self‐synthesized tertiary amine unit, (bis(2‐hydroxyethyl)‐3,3′‐((2‐(dimethylamino)ethyl)azanediyl)dipropanoate) (N‐diol), as an internal catalyst for transcarbamoylation and potential transesterification reactions. The resulting polymer, with a gel content of 97% and a glass transition temperature of 29 °C, is fabricated into test samples for comprehensive thermal and mechanical evaluations. The material demonstrates an initial Young's modulus of 555 MPa, retaining 81% of this value after two recycling processes. Additionally, using stress relaxation analysis (SRA), a topology freezing temperature of 82 °C, indicative of the characteristic Arrhenius‐like relaxation behavior, is identified with a bond exchange activation energy of 163 kJ mol−1.

Supramolecular cross-linking affords superelastic and fatigue-resistant cellulose-based nanocomposites with excellent thermomechanical properties and waterproofing performance

Nanocellulose is one of the most abundant renewable resources on earth and is used in many applications due to its excellent physical and chemical properties, and it is an important biopolymer raw material to support human well-being. However, current cellulose-based aerogel nanocomposites are plagued by irreconcilable contradictions between thermomechanical and waterproofing characteristics due to their hygroscopicity. Herein, sustainable insulating cellulose aerogel nanocomposites are prepared from tempo-oxidized bamboo cellulose nanofibrils (CNFs) and polyvinyl alcohol (PVA) with a continuous orientation-free pore architecture formed by CNFs/PVA pre-hydrogel aggregates, which combine to become the basic structural unit for producing superelastic properties. The resulting lightweight CNFs/PVA aerogels (CNPA) with a hierarchical orientation-free pore architecture and density about 5–20 kg m3 achieve an optimal thermomechanical and insulation trade-off, demonstrating temperature-invariant compressibility (–100–500 ℃) and a low thermal conductivity of 38.2 mW m–1 K–1 at 300 ℃. Particularly, the flyweight CNPA retained its structural integrity after more than 106 cycles at ɛ=20 %, 105 cycles at ɛ=50 %, and 104 cycles at ɛ=80 %. Furthermore, CNPA also exhibits robust liquid-repellency with a WCA exceeding 160.3°. This lightweight cellulose-based nanocomposites, although constructed using an intrinsically hygroscopicity nanocellulose-constituent, is simultaneously superelastic, fatigue-resistant, thermomechanical, and waterproofing performance.

Study on the curing characteristics and properties of phthalonitrile resin cured with organic guanidine

Bisphenol A-based phthalonitrile resin was synthesized by nucleophilic substitution reaction from bisphenol A and 4-nitrophthalonitrile, and then the obtained resin was cured with sulfaguanidine as a novel curing agent. The curing characteristics, kinetics, thermal stability and dynamic mechanical property were studied by standard thermal analysis techniques including DSC, TGA, and DMA. The peak temperature of exothermic peak ( Tp) and apparent activation energy ( Ea) of sulfaguanidine cured phthalonitrile resin were 263.20°C and 76.6 kJ·mol−1 respectively, much lower than those of traditional aromatic diamine cured resin. Moreover, the resin cured by sulfaguanidine showed excellent thermomechanical properties and thermal stability. The glass transition temperature ( Tg) was 284.8°C, the initial thermal decomposition temperature ( Td,5%) was 439.6°C, and the char yield at 800°C was 62.1% in nitrogen atmosphere. To sum up, organic guanidine cured phthalonitrile resin exhibits excellent curing characteristics (low Tp and Ea) and high thermal properties, which provides a promising approach to preparing phthalonitrile resin with high comprehensive performance.

Closed-loop recyclability of a biomass-derived epoxy-amine thermoset by methanolysis.

Epoxy resin thermosets (ERTs) are an important class of polymeric materials. However, owing to their highly cross-linked nature, they suffer from poor recyclability, which contributes to an unacceptable level of environmental pollution. There is a clear need for the design of inherently recyclable ERTs that are based on renewable resources. We present the synthesis and closed-loop recycling of a fully lignocellulose-derivable epoxy resin (DGF/MBCA), prepared from dimethyl ester of 2,5-furandicarboxylic acid (DMFD), 4,4'-methylenebis(cyclohexylamine) (MBCA), and glycidol, which displays excellent thermomechanical properties (a glass transition temperature of 170°C, and a storage modulus at 25°C of 1.2 gigapascals). Notably, the material undergoes methanolysis in the absence of any catalyst, regenerating 90% of the original DMFD. The diamine MBCA and glycidol can subsequently be reformed by acetolysis. Application and recycling of DGF/MBCA in glass and plant fiber composites are demonstrated.

Rotating Flow and Heat Transfer Characteristics of a Novel Cooling Channel for Gas Turbine Blade Trailing Edge With Diamond-Type TPMS Structures

Abstract This work designs a Diamond-type triply periodic minimal surface (TPMS) structure that exhibits excellent thermomechanical properties in a gas turbine blade trailing edge to enhance thermal performance and improve heat transfer uniformity. Since the velocity and temperature distributions are altered in the rotating trailing edge channel, the flow and heat transfer characteristics of the baseline pin fin and Diamond TPMS models are numerically investigated at the Reynolds number of 10,000 and the rotation numbers of 0.0–0.28. Compared to the baseline model, the Diamond TPMS network significantly decreases recirculation flow at the inner wall, improving heat transfer, especially at the tip and outlet regions. Although the Diamond TPMS model incurs substantial pressure losses from 191% to 234%, it yields significantly higher overall heat transfer than the pin fins by 179%. Consequently, the thermal performance increased by 93.4%. The flow fluctuations due to the rotating effects are minor in the Diamond TPMS architecture, considerably reducing the differences in heat transfer between the leading and trailing walls. The differences in the wetted-area averaged Nusselt number of the baseline and Diamond TPMS models within the studied rotation numbers are 8.5–14.4% and about 8.5%, respectively. Moreover, the Diamond TPMS structure reduces the differences in heat transfer between the root and tip regions at the outlet by up to 80% compared to the pin fins. This improvement helps protect the trailing edge from thermal failure, thereby potentially prolonging the gas turbine blade's lifetime.

Mixed-Material Feedstocks for Cold Spray Additive Manufacturing of Metal–Polymer Composites

High-performance polymers such as poly(ether ether ketone) (PEEK) are appealing as composite components for a wide variety of industrial and medical applications due to their excellent thermomechanical properties. However, conventional PEEK metallization methods can often lead to poor quality control, low deposition rate, and high cost. Cold spray is a promising potential alternative to produce polymer–metal composites rapidly and inexpensively due to its relatively mild operating conditions and high throughput. In this study, we investigated the deposition characteristics of metal–polymer composite feedstock, composed of PEEK powder and copper flake in varying ratios, onto a PEEK substrate. Copper-PEEK powder blends were prepared by both hand-mixing and cryogenic milling (cryomilling), which predominantly creates composite particles with micron-scale copper domains coating PEEK particle surfaces. This process non-monotonically affects the relative dominance and length scales of the multiple contributing deposition mechanisms present in mixed-material cold spray. In low-pressure cold spray, deposits showed significant changes in deposition efficiency and composition as a result of milling, with improvements in these characteristics most dramatic at lower Cu fractions. Deposits of a cryomilled blend of nominally 30 vol.% copper in PEEK exhibited minimal porosity under scanning electron microscopy, complete retention of powder composition, and the highest deposition efficiency among all samples tested. Notably, neither neat PEEK nor neat Cu meaningfully deposited at the same mild conditions as this 30 vol.% Cu blend, indicating a synergistic departure from linear mixing rules driven by the relative balance of local deposition interactions (e.g., hard–soft, soft–soft, etc.). Intentional powder and process design toward optimizing this balance may facilitate cold spray metallization applications.

Effect of Repeat Unit’s Composition Ratio on the Properties of a Random Copolymer: A Molecular Dynamics Simulation Study

For thermosetting resins the degree of cross-linking plays a crucial role in the dielectric properties of the resin. In our previous works we confirmed this by simulating the relationship between the dielectric properties of poly(2-(4-benzocyclobutenyl)-divinylbenzene (DVB-S-BCB)) and the degree of cross-linking. In our research described here, we constructed a novel random copolymer with all-hydrocarbon structure based on poly(DVB-S-BCB) by introducing styrene (St) as the second polymerization monomer, thus controlling the number of cross-linking sites in the polymer. The effect of changes in St monomer content (number of cross-linking points) in the polymer chains, i.e. DVB-S-BCB and St, on the dielectric properties of the cured resins was investigated by molecular dynamics simulations. The simulation results showed that increasing the St monomer content in the copolymer, decreasing the cross-linking points, led to an increase in the dielectric constant of the cured resin, in addition to which the copolymer exhibited excellent thermo-mechanical properties. We also tested resin samples prepared by the experimental method and compared them with the simulated data, confirming the reliability of the results within acceptable error limits.

Synthesis of pyrogallol triglycidyl ether: A bio-based epoxy resin monomer with low viscosity, high activity, and good thermomechanical properties

With increasing development of chip and circuit integration, the requirements regarding the viscosity, activity, and thermomechanical properties of underfill are becoming increasingly stringent. However, common low-viscosity resins are often obtained with poor thermal and thermomechanical properties. In this study, natural renewable pyrogallol was used as a raw material and preparedto prepare a high-performance polyphenol epoxy resin monomer named E3PG (pyrogallol triglycidyl ether) through employing a combination of epichlorohydrin and olefin epoxidation methods for the first time. At 25°C, the viscosity of E3PG was only 210 cps, indicating excellent processability. Compared with traditional epoxy resin (E51), E3PG has a lower activation energy, and more importantly, exhibits excellent thermomechanical properties after curing; its glass transition temperature (Tg) reaches 164°C, and its storage modulus (E′) reaches 3500 MPa at 25°C. In this study, an epoxy resin monomer with excellent properties was successfully prepared using renewable polyphenols as raw materials, providing a unique and novel approach for the synthesis of epoxy resin monomers.

Efficient Regulation of the Cross-Linking Structure in Polyurethane: Achieving Outstanding Processing and Mechanical Properties for a Wind Turbine Blade.

Although epoxy resin has been extensively used in the field of wind turbine blades, polyurethane has attracted much attention in recent years, due to its potential value of better fatigue resistance, lower processing viscosity and higher strength than epoxy resin blades. Herein, we construct a dense cross-linking structure in polyurethane (PU) based on different amounts of hydroxypropyl methacrylate (HPMA) with low processing viscosity and excellent mechanical properties. By increasing the content of HPMA, the thermal stability of PU is enhanced, but the micro-morphology does not change significantly. When the content of HPMA is 50 g (in 200 g copolymer), the PU sample PH-50 exhibits a viscosity of 70 MPa·s and a gelation time of 120 min at 25 °C, which is sufficient to complete processes like pouring and filling. By post-curing the PH-50 at 80 °C for 2 h, the heat distortion temperature can reach 72 °C, indicating the increase of temperature resistance. The PU copolymers also have excellent mechanical and dynamic thermo-mechanical properties due to the cross-linking structure between PU chains and poly-HPMA chains. Additionally, the PU copolymer has excellent compatibility with various glass fiber fabrics (GFF), showing a good match in the vacuum infusion experiment and great properties in the mechanical test. By compounding PH-50 with GFF, the composite with high strength is easily prepared for a wind turbine blade in various positions. The tensile strengths of the composites are all over 1000 MPa in the 0° direction. Such composites are promising for the future development of wind turbine blades that meet the stringent requirements for outstanding processing and mechanical properties.

Cellulose nanofibrils as a bio-based binder for wood fiber composite insulation panels with enhanced thermo-mechanical properties for structural wall sheathing applications

A low-density wood fiber insulation panel (WIP) composite was developed with 100 % petrochemical-free, bio-based binder with high mechanical strength, water resistance and thermal insulation properties. This study investigated the manufacturing process of composite WIPs made with mechanical pulp fibers with cellulose nanofibrils (CNFs), lignin-containing CNFs (LCNFs), hybridized CNFs-LCNFs, and CNFs-starch as a binder on different scales and evaluated the effects of binder type and content on the panels’ physical, mechanical, and thermal properties. All panels had excellent thermal resistivity values, which increased with the decrease in density. The WIPs made with LCNFs as binder had lower mechanical properties, but it was possible to replace 20 % CNFs with LCNFs to obtain the same performance as neat CNFs as the binder. Untreated panels had poor water resistance but the water absorption properties were significantly improved with the addition wax. The WIPs made with 5 % and 7.5 % binder content and 2 % wax addition could fulfill the criteria of regular and structural wall sheathing applications, respectively. Overall, the results confirm the potential of CNFs and LCNFs to be used as 100 % bio-based adhesives to produce eco-friendly composite WIPs with excellent thermo-mechanical properties to be used for regular and structural wall sheathing applications.

Effect of organoclay on the physical properties of colorless and transparent copoly(amide imide) nanocomposites.

Copoly(amic acid) was prepared using the diamine monomer N,N'-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]bis(4-aminobenzamide) (TFAB) and the anhydride monomers 4,4'-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA) and 4,4'-biphthalic anhydride (BPA). Thereafter, a colorless and transparent copoly(amide imide) (Co-CPAI) film was synthesized through various heat treatments. Co-CPAI hybrid films with a TFAB : 6FDA : BPA molar ratio of 1 : 0.5 : 0.5 were subsequently fabricated using organically modified hectorite (STN) with various contents ranging from 0 to 7 wt% via the solution intercalation method. Finally, the thermomechanical properties, clay dispersion, and optical transmittance of the hybrid films were investigated. The results of wide-angle X-ray diffractometry and transmission electron microscopy demonstrated good dispersion at low clay loadings; however, clay agglomeration was observed above a certain critical STN content. At the critical STN content of 3 wt%, the clay was evenly distributed in the matrix with a nanoscale thickness of approximately 10 nm. Hybrid films containing 3 wt% STN showed excellent thermomechanical properties. Beyond this critical clay content, the physical properties of the films decreased because of the agglomeration of excess clay. Regardless of the clay content, however, the optical properties of the hybrid films remained constant, and their yellow indices, which ranged from 2 to 4, indicated excellent colorless transparency.

Rotational stress-induced shish-kebab governs the balance of enhanced thermal conductivity and mechanical performance of high-density polyethylene (HDPE) / boron nitride (BN) composites via axial hot compression

Polymer-based composites with high BN sheets loadings have potential to improve thermal conductivity without compromising mechanical performance. In this work, a balanced enhancement in both thermal conductivity and tensile strength were achieved using rotational shear followed by axial hot compression. For neat HDPE matrix, the highly oriented shish-kebab structures induced by shear field improved tensile strength from 20.4 MPa to 80.9 MPa, compared with unsheared specimens. The in-plane thermal conductivity of sheared HDPE/BN composite was 25.0% higher than the unsheared one. Axial hot compression resulted in denser crystal and oriented fillers, leading to a 63% increase in tensile strength while simultaneously increasing thermal conductivity in both in-plane and out-plane directions. This work has utilized rotation shear and axial hot compression to manufacture HDPE/BN composites with effective two-way thermal conductivity and higher tensile strength. The excellent thermo-mechanical properties mean a longer service time and less replaced frequency of material under extreme operating conditions. The two-step methods provide a key information for the preparation of composites with balanced mechanical properties and thermal conductivity.