Preparation of boron nitride nanosheets via polyethyleneimine assisted sand milling: towards thermal conductivity and insulation applications

Hexagonal boron nitride (h-BN) is often used as a filler in polymer composites due to its good thermal conductivity and insulation properties. However, the compatibility between h-BN and the matrix limits its application areas. To overcome this issue, a combination of mechanical liquid phase exfoliation and chemical interfacial modification was adopted in this work. Polyethyleneimine (PEI) was used as the exfoliation reagent to prepare PEI-functionalized h-BN nanosheets, denoted as PEI@BNNS. Thermoplastic polyurethane (TPU) composites with different contents of h-BN and PEI@BNNS which were recorded as h-BN/TPU and PEI@BNNS/TPU were successfully prepared through a hot-pressing process, respectively. The results show that PEI@BNNS/TPU composites have better in-plane thermal conductivity while maintaining insulation, and with the content of 5 wt% PEI@BNNS, the in-plane thermal conductivity of the PEI@BNNS/TPU composite is up to 0.61 W m⁻¹ K⁻¹, which is three times that of pure TPU (0.22 W m⁻¹ K⁻¹).

The PEI-grafted boron nitride nanosheets were successfully prepared via sand-milling process, which were doped into thermoplastic polyurethane matrix for better in-plane thermal conductivity while maintaining insulation properties.     

Enhanced thermal conductivity of epoxy composites filled with tetrapod-shaped ZnO

Epoxy composites with ZnO powders characterized by different structures as inclusion are prepared and their thermal properties are studied. The experimental results demonstrate that the epoxy resins filled by tetrapod-shaped ZnO (T-ZnO) whiskers have the superior thermal transport property in comparison to ZnO micron particles (ZnO MPs). The thermal conductivity of ZnO/epoxy and T-ZnO/epoxy composites in different mass fraction (10, 20, 30, 40, 50 wt%) are respectively investigated and the suitable models are compared to explain the enhancement effect of thermal conductivity. The thermal conductivity of T-ZnO/epoxy composites with 50 wt% filler reaches 4.38 W m⁻¹ K⁻¹, approximately 1816% enhancement as compared to neat epoxy. In contrast, the same mass fraction of ZnO MPs are incorporated into epoxy matrix showed less improvement on thermal conduction properties. This is because T-ZnO whiskers act as a thermal conductance bridge in the epoxy matrix. In addition, the other thermal properties of T-ZnO/epoxy composites are also improved. Furthermore, the T-ZnO/epoxy composite also presents a much reduced coefficient of thermal expansion (∼28.1 ppm K⁻¹) and increased glass transition temperature (215.7 °C). This strategy meets the requirement for the rapid development of advanced electronic packaging.

Epoxy composites with ZnO powders characterized by different structures as inclusion are prepared and their thermal properties are studied.     

Practical PBT/PC/GNP composites with anisotropic thermal conductivity

Most of the highly thermally conductive polymer-based composites currently face problems that must be solved before they can be directly used in industrial production. Herein, a practical polybutylene terephthalate (PBT)/polycarbonate (PC)/graphite nanoplatelet (GNP) thermally conductive composite with relative low filler content was prepared by a conventional melt-blending technique. GNPs selectively distributed and oriented in the PBT phase afford the composite a low percolation threshold and anisotropic thermal conductivity. Investigation of the influence of filler content on the final comprehensive performance showed that a prepared PBT/PC/GNP composite with 20 vol% GNPs exhibited superior performance in thermal conductivity, heat resistance, and mechanical properties. The in-plane and through-plane thermal conductivities of the composite were 5.82 W m⁻¹ K⁻¹ and 1.06 W m⁻¹ K⁻¹, respectively, which were increased by 2430% and 361% as compared to that of a neat PBT/PC blend. The Vicat softening temperature increased by 17.7 °C and reached 213.7 °C, while the mechanical properties also maintained a good application level.

The selective distribution of thermally conductive fillers in a co-continuous polymer blends provides an industrialized preparation method that takes into account both the properties and functions of thermally conductive composites.     

High thermal conductivity driven by the unusual phonon relaxation time platform in 2D monolayer boron arsenide

The cubic boron arsenide (BAs) crystal has received extensive research attention because of its ultra-high thermal conductivity comparable to that of diamond. In this work, we performed a comprehensive study on the diffusive thermal properties of its two-dimensional (2D) counterpart, the monolayer honeycomb BAs (h-BAs), through solving the phonon Boltzmann transport equation combined with first-principles calculation. We found that unlike the pronounced contribution from out-of-plane acoustic phonons (ZA) in graphene, the high thermal conductivity (181 W m⁻¹ K⁻¹ at 300 K) of h-BAs is mainly contributed by in-plane phonon modes, instead of the ZA mode. This result is explained by the unique frequency-independent ‘platform’ region in the relaxation time of in-plane phonons. Moreover, we conducted a comparative study of thermal conductivity between 2D h-BAs and h-GaN, because both of them have a similar mass density. The thermal conductivity of h-BAs is one order of magnitude higher than that of h-GaN (16 W m⁻¹ K⁻¹), which is governed by the different phonon scattering process attributed to the opposite wavevector dependence in out-of-plane optical phonons. Our findings provide new insight into the physics of heat conduction in 2D materials, and demonstrate h-BAs to be a new thermally conductive 2D semiconductor.

The cubic boron arsenide (BAs) crystal has received extensive research attention because of its ultra-high thermal conductivity comparable to that of diamond.     

Research on the thermal conductivity and dielectric properties of AlN and BN co-filled addition-cure liquid silicone rubber composites

The present work aims at studying the thermal and dielectric properties of addition-cure liquid silicone rubber (ALSR) matrix composites using boron nitride (BN) and aluminum nitride (AlN) as a hybrid thermal conductive filler. Composite samples with different filler contents were fabricated, and the density, thermal conductivity, thermal stability, dielectric properties, and volume resistivity of the samples were measured. According to the experimental results, the density, thermal conductivity, dielectric constant and dielectric loss tangent values all increased with the increasing addition of filler. When the weight fraction of hBN filler was 50 wt%, the thermal conductivity of composites was 0.554 W (m⁻¹ K⁻¹), which is 3.4 times higher than that of pure ALSR. The corresponding relative permittivity and dielectric loss were 3.98 and 0.0085 at 1 MHz, respectively. Furthermore, TGA results revealed that the AlN/BN hybrid filler could also improve the thermal stability of ALSR. The volume resistivity of ALSR composites was higher than that of pure ALSR. The addition of fillers improved the thermal properties of ALSR and had little effect on its insulation properties. This characteristic makes ALSR composites attractive in the field of insulating materials.

The present work aims at studying the thermal and dielectric properties of addition-cure liquid silicone rubber (ALSR) matrix composites using boron nitride (BN) and aluminum nitride (AlN) as a hybrid thermal conductive filler.     

An effective utilization of MXene and its effect on electromagnetic interference shielding: flexible,free-standing and thermally conductive composite from MXene–PAT–poly(p-aminophenol)–polyaniline co-polymer

MXene and conductive polymers are attractive candidates for electromagnetic interference shielding (EMI) applications. The MXene–PAT-conductive polymer (CP) composites were fabricated by a cost-effective spray coating technique and characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. A new approach has been developed for the synthesis of exfoliated MXene. The MXene–PAT–poly(p-aminophenol)–polyaniline co-polymer composite exhibited good electric conductivity (EC) of 7.813 S cm⁻¹. The composites revealed an excellent thermal properties, which were 0.687 W (m K)⁻¹ thermal conductivity, 2.247 J (g K)⁻¹ heat capacity, 0.282 mm² s⁻¹ thermal diffusivity and 1.330 W s^1/2 m⁻² K⁻¹ thermal effusivity. The composites showed 99.99% shielding efficiency and the MXene–PAT–PANI–PpAP composite (MXPATPA) had EMI shielding effectiveness of 45.18 dB at 8.2 GHz. The reduced form of MXene (r-Ti₃C₂T_x) increased the shielding effectiveness (SE) by 7.26% and the absorption (SE_A) was greatly enhanced by the ant farm like structure. The composites possess excellent thermal and EMI SE characteristics, thus can be applied in areas, such as mobile phones, military utensils, heat-emitting electronic devices, automobiles and radars.

MXene and conductive polymers are attractive candidates for electromagnetic interference shielding (EMI) applications.     

Surface modification and thermal performance of a graphene oxide/novolac epoxy composite

Functionalized graphene oxide (GO) was successfully modified by grafting 1,3,5-triglycidylisocyanurate (TGIC) onto the surface of GO. The modified GO was then added to a novolac epoxy composite at various volume fractions to improve the interfacial compatibility between the filler and matrix. Samples of the modified GO/novolac epoxy composite were fabricated through the hot-pressing method. Microstructural analysis revealed that the modified GO dispersed well in the matrix and formed thermal conductive pathways across the matrix. The thermal degradation temperature of 50% weight loss of the modified GO/novolac epoxy composite was 166 °C higher than that of the novolac epoxy. The data for loss factor tan δ demonstrated that when the composite contained 36.8 wt% of modified GO, the glass transition temperature of the modified GO/novolac epoxy composite was 222 °C, which is 90 °C higher than that of the novolac epoxy. The thermal conductivity of the modified GO/novolac epoxy composite improved from 0.044 W m⁻¹ K⁻¹ to 1.091 W m⁻¹ K⁻¹. Results indicated that the incorporation of surface-modified GO into the novolac epoxy positively affects the thermal conductivity and various properties of the modified GO/novolac epoxy composite.

Functionalized graphene oxide (GO) was successfully modified by grafting 1,3,5-triglycidylisocyanurate (TGIC) onto the surface of GO.     

Manufacturing silica aerogel and cryogel through ambient pressure and freeze drying

Achieving a mesoporous structure in superinsulation materials is pivotal for guaranteeing a harmonious relationship between low thermal conductivity, high porosity, and low density. Herein, we report silica-based cryogel and aerogel materials by implementing freeze-drying and ambient-pressure-drying processes respectively. The obtained freeze-dried cryogels yield thermal conductivity of 23 mW m⁻¹ K⁻¹, with specific surface area of 369.4 m² g⁻¹, and porosity of 96.7%, whereas ambient-pressure-dried aerogels exhibit thermal conductivity of 23.6 mW m⁻¹ K⁻¹, specific surface area of 473.8 m² g⁻¹, and porosity of 97.4%. In addition, the fiber-reinforced nanocomposites obtained via freeze-drying feature a low thermal conductivity (28.0 mW m⁻¹ K⁻¹) and high mechanical properties (∼620 kPa maximum compressive stress and Young''s modulus of 715 kPa), coupled with advanced flame-retardant capabilities, while the composite materials from the ambient pressure drying process have thermal conductivity of 28.8 mW m⁻¹ K⁻¹, ∼200 kPa maximum compressive stress and Young''s modulus of 612 kPa respectively. The aforementioned results highlight the capabilities of both drying processes for the development of thermal insulation materials for energy-efficient applications.

Ambient pressure and freeze drying techniques enable silica aerogel and cryogel insulation composites.     

Anisotropic thermal conductive properties of cigarette filter-templated graphene/epoxy composites

Herein, a cigarette filter-templated graphene/epoxy composite was prepared with enhanced thermal conductive properties. The through-plane thermal conductivity of the epoxy composite was up to 1.2 W mK⁻¹, which was 4 times that of it in the in-plane (0.298 W mK⁻¹) after only 5 filtration cycles. The thermal conductive anisotropy and improvement in the through-plane thermal conductivity of the epoxy composite were attributed to the particular structure of cigarette filter-templated graphene in the epoxy matrix. The unique structure formed effective conductive pathways in the composite to improve the thermal transportation properties. The excellent thermal transportation properties allow the epoxy composite to be used as an efficient heat dissipation material for thermal management applications.

We report a facile method to prepare cigarette filter-templated graphene/epoxy composites with excellent thermal transport performance.     

Fabricating high thermal conductivity rGO/polyimide nanocomposite films via a freeze-drying approach

The preparation of polymeric composite materials with low filler content as well as high thermal conductivity has been an important subject for the field of polymer material research. During our recent investigation on polyimide (PI), it was found that poly(amic acid) (PAA) solution (in dimethylacetamide, DMAc) could crystallize at low temperature. When adding reduced graphene oxide (rGO) as the thermal conductive fillers in the PAA solution, it was also found that the crystallization process of PAA would impel the rGO to rearrange in order and form an aligned thermal conductive network. To retain the rGO network structure, the freeze-drying technique was used to remove the solvent. Subsequently, through a thermal imidization process the final rGO/PI films containing a 3D rGO network could be obtained. The PI composite films retain good flexibility, excellent thermal stability, and exhibit excellent thermal conductivity. When the content of rGO added is 8 wt%, the thermal conductivity of the rGO/PI film can reach a high value of 2.78 W m⁻¹ K⁻¹, which is about 15.4 times that of neat PI and 5.5 times that of the rGO/PI composite film prepared by the conventional two-step routine with the same content of rGO.

PI composite films with excellent thermal conductivity (as high as 2.78 W m⁻¹ K⁻¹) have been fabricated by a freeze drying approach.     

Thermoelectric performance enhancement of eco-friendly Cu2Se through incorporating CB4

We have prepared Cu₂Se + x wt% CB₄ composites with x = 0, 0.1, 0.3, 0.5, and 0.7 by a hydrothermal method and hot-pressing technique. The structural and compositional analysis indicates that pure phase Cu₂Se powders were synthesized and the densified layered bulk samples were obtained. Electrical properties testing showed that the sample with x = 0.5 has the high power factor of 0.886 mW m⁻¹ K⁻² due to its high Seebeck coefficient. Meanwhile, the thermal conductivity was suppressed to 0.6 W m⁻¹ K⁻¹ at 773 K. As a result, the final optimized ZT value of 1.46 at 773 K was achieved. These results suggest that CB₄ could be an alternative inclusion to improve effectively the thermoelectric performance of Cu₂Se.

Thermoelectric performance enhancement in a liquid-like material Cu₂Se by introducing CB₄ nanopowders based on the hydrothermal method and hot-pressing technique.     

Flexible PANI/SWCNT thermoelectric films with ultrahigh electrical conductivity

The effects of polyaniline (PANI) with different polymerization times on the film-forming and thermoelectric properties as well as on the performance of SWCNTs/PANI composites were systematically investigated in this study. It was found that the film-forming and flexibility of PANI films improved with the increase in polymerization time. We showed that a super high conductivity of ∼4000 S cm⁻¹ can be achieved for the SWCNTs/PANI composite film, which is the highest value for the SWCNTs/PANI system at present. Both the electrical conductivity and power factor increase by an order of magnitude than that of pure PANI films and far exceed the theoretical value of the mixture model. These results suggest that the sufficiently continuous and ordered regions on the interlayer between the filler and matrix are key to improve the electrical conductivity of composites. Finally, the maximum PF reaches 100 μW m⁻¹ K⁻² at 410 K for the 0.6CNT/PANI5h. Furthermore, it is found that the composite films have excellent environmental and structural stability. Our results can deepen the understanding of organic–inorganic thermoelectric composite systems and facilitate the practical application of flexible and wearable thermoelectric materials.

Flexible PANI/SWCNT thermoelectric films with ultrahigh electrical conductivity of ~4000 S cm⁻¹. The maximum PF reaches 100 μW m⁻¹ K⁻² at 410 K for the 0.6CNT/PANI.     

Effect of networked hybridized nanoparticle reinforcement on the thermal conductivity and mechanical properties of natural rubber composites

Thermal conductivity of natural rubber (NR) was enhanced by incorporating novel conductive hybrid nanofillers, namely polyaniline grafted carbon black (PANI/CB) nanoparticles and carbon black nanoparticles linked with carbon microfiber (CF/CB) composites. The PANI/CB hybrid fillers were synthesized using an in situ method, where aniline monomers were initially adsorbed onto carbon black spherical domains and, afterwards, it was polymerized in the presence of an oxidizer. Final rubber composites were prepared through melt mixing, where PANI/CB and CF/CB filler loading was kept at 40 parts per hundred of rubber (phr). The thermal conductivity values of the rubber composites with CF/CB (20 : 20) and PANI/CB (20 : 20) yield were 0.45 W m⁻¹ K⁻¹ and 0.31 W m⁻¹ K⁻¹, respectively and the thermal conductivity improved significantly compared to the control (0.25 W m⁻¹ K⁻¹) sample. The higher thermal conductivity values of CF/CB and PANI/CB incorporated composites suggest that the generated networked structure of CF and PANI nanofibers with CB nanoparticles has immensely contributed to enhancing the heat dissipation compared to that of the neat CB rubber composite. Scanning electron micrographs (SEM) confirmed the attachment of the synthesized PANI onto the spherical CB nanoparticles and interconnected morphology of CF/CB and PANI/CB hybrid fillers. The synthesized PANI/CB hybrid filler was further characterized using Fourier-transform infrared (FTIR) spectroscopy to evaluate the chemical properties. Furthermore, thermogravimetric analysis revealed the higher thermal stability of CF/CB (20 : 20) and PANI/CB (20 : 20) composites compared to the control. Moreover, the addition of CF/CB (20 : 20) and PANI/CB (20 : 20) improved the mechanical properties such as ultimate tensile strength, modulus at break, resilience and abrasion resistance significantly and well above the minimum required standard mechanical parameters in the tyre industry. These reinforced composites show great potential to be used as heat dissipating rubber composites in the tyre industry.

Thermal conductivity of natural rubber was enhanced by incorporating novel conductive hybrid nanofillers, namely polyaniline grafted carbon black nanoparticles and carbon black nanoparticles linked with carbon microfiber composites.     

The combination of Al2O3 and BN for enhancing the thermal conductivity of PA12 composites prepared by selective laser sintering

A powder-based 3D printing technology, selective laser sintering (SLS), is a novel strategy of manufacturing complex components with specially tailored properties, including mechanical properties, as well as thermal and electrical conductivity. In this study, the effect of incorporating Al₂O₃ particles and BN plates on the thermal conductivity of PA12 composites was investigated. PA12 composite powders, which can be well applied to SLS, were prepared via a two-step approach to mixing. Morphology characteristics demonstrated that the fillers dispersed uniformly in the PA12 matrix, as expected. With 35 wt% Al₂O₃ and 15 wt% BN hybrid fillers, the tensile strength had the potential to reach 25.7 MPa, while the thermal conductivity could reach 1.05 W m⁻¹ K⁻¹, 275% higher than that of pure PA12. In addition, the study investigated the effects of filler content on the thermal stability and mechanical properties whilst analysing the melting and crystallisation behaviours of SLS components. The results demonstrate that these composites have favourable thermal stability and exhibit no severe deterioration in mechanical properties. The PA12 composites prepared in this work therefore illustrated vast potential in thermal management materials.

The introduction of hybrid fillers in SLS technology is an effective method for the manufacture of thermally conductive polymer composites with high thermal conductivity, complex structures and good mechanical properties.     

Facile construction of the aerogel/geopolymer composite with ultra-low thermal conductivity and high mechanical performance

In this work, we have successfully prepared a lightweight, highly hydrophobic and superb thermal insulating aerogel/geopolymer composite by a sol–gel immersion method. After silica aerogel was impregnated, the composite exhibited nano-porous structures. Moreover, scanning electron microscopy observations revealed that the aerogel particles were tightly anchored on the geopolymer surface. With several excellent properties (bulk density: 306.5 g cm⁻³, thermal conductivity: 0.0480 W m⁻¹ K⁻¹ and maximum compressive strength: 0.79 MPa) the as-prepared composite shows great potential to be applied in the thermal insulation field.

In this work, we have successfully prepared a lightweight, highly hydrophobic and superb thermal insulating aerogel/geopolymer composite by a sol–gel immersion method.     

Largely enhanced thermal conductivity and thermal stability of ultra high molecular weight polyethylene composites via BN/CNT synergy

In recent years, thermally conductive polymer-based composites have garnered significant attention due to their light weight and easy formation process. In this work, the thermal conductivity of ultra high molecular weight polyethylene (UPE) composites was improved through construction of a hybrid filler network of boron nitride sheets (BNs) and carbon nanotubes (CNTs) in the matrix via hot compression. The morphology, UPE aggregate structure, thermal conductivity, heat dissipation capacity and thermal stability of the UPE composites were investigated. The thermal conduction mechanism of the UPE composites was explored through simulations with Agari''s semi-empirical formula. The results showed that the thermal conductivity of the UPE composite with 40 wt% BNs and 7 wt% CNTs was 2.38 W m⁻¹ K⁻¹, which was 495% higher than that of pure UPE, showing a synergistic effect between BNs and CNTs. The simulations with Agari''s semi-empirical simulation suggested that increasing the CNT content contributed to synergistically assist BNs to form a better continuous and effective hybrid filler thermal network, thereby reducing phonon scattering and thermal resistance between BNs. In addition, UPE composites doped with BNs and CNTs presented better heat dissipation capacity and higher thermal stability as compared to that of pure UPE.

The carbon nanotubes (CNTs) synergistically assist boron nitride microsheets (BNs) to form a more continuous and effective thermal conduction path.     

Synergistic effect of reduced graphene oxide/carbon nanotube hybrid papers on cross-plane thermal and mechanical properties

Graphene paper has attracted great attention as a heat dissipation material due to its excellent thermal conductivity and mechanical properties. However, the thermal conductivity of graphene paper in the normal direction is relatively poor. In this work, the cross-plane thermal conductivities (K_⊥) and mechanical properties of the reduced graphene oxide/carbon nanotube papers with different CNT loadings were studied systematically. It was found that the K_⊥ decreased from 0.0393 W m⁻¹ K⁻¹ for 0 wt% paper to 0.0250 W m⁻¹ K⁻¹ for 3 wt% paper, and then increased to 0.1199 W m⁻¹ K⁻¹ for 20 wt% paper. The papers demonstrated a maximum elastic modulus of 6.1 GPa with 10 wt% CNT loading. The CNTs acted as scaffolds to restrain the graphene sheets from corrugating and to reinforce the mechanical properties of the hybrid papers. The more CNTs that filled the gaps between graphene sheets, the greater the number of channels of the transmission of phonons and the looser the structure in the cross-plane direction. Further mechanism analysis revealed the synergistic effects of CNT loadings and graphene sheets on enhancing the thermal and mechanical performance of the papers.

The top-view SEM images for (a) rGO, (b) rGO/CNT-3%, (c) rGO/CNTs-20% and the corresponding schematic diagram of photon transmission with different spacer CNTs loadings (a-i, b-ii, c-iii).     

Simple in situ synthesis of SiC nanofibers on graphite felt as a scaffold for improving performance of paraffin-based composite phase change materials

A paraffin phase change material absorbed in a composite material of silicon carbide nanofibers and graphite fibers was prepared by vacuum impregnation to solve problems of current organic phase change materials, such as the low thermal response rate, low thermal conductivity, and high vulnerability to leakage. A composite material containing a phase change material as the scaffold combined with silicon carbide nanofibers is prepared by a simple vapor–solid reaction using industrially produced porous graphite felt as the raw material. The thermal conductivity of the composite phase change material is increased to 1.29 W m⁻¹ K⁻¹ by thermal strengthening of the supporting scaffold. Compared with the thermal conductivity of pure paraffin of 0.25 W m⁻¹ K⁻¹, not only is the thermal response rate improved, but the composite phase change material also exhibits chemical stability, shape stability, and stable thermal properties. The phase change enthalpies of the melting and freezing processes are 180.5 and 176.4 J g⁻¹, respectively. In addition, the use of low-cost graphite felt and the simple synthetic process of the composite phase change material facilitates large-scale production. Moreover, the composite is extremely flexible in terms of its shape design and has good energy storage properties in terms of photo-thermal conversion. These features promise to accelerate the effective application of the prepared composite phase change material in solar and buildings energy storage with great potential for application practices.

The composite phase change material has excellent thermal properties, good photo-thermal conversion efficiency and flexible design in size, which produces a type of material for applications in solar and buildings energy storage.     

Development of Prosopis juliflora carbon-reinforced PET bottle waste-based epoxy-blended bio-phenolic benzoxazine composites for advanced applications

An attempt has been made in the present work to develop hybrid blended composites using epoxy resin (PETEP) derived from waste polyethylene terephthalate (PET) bottles and bio-phenolic (cardanol)-based benzoxazine (CBz) reinforced with functionalized bio-carbon (f-PJC) obtained from Prosopis juliflora (PJ) for high performance applications. The molecular structure, thermal properties, thermo-mechanical behaviour, morphology, surface properties, and corrosion resistance of the composites were studied by different analytical methods, and the obtained results are reported. Dynamic mechanical properties such as the storage modulus (2.591 GPa), loss modulus (1.299 GPa) and cross-linking density (5.1 × 10⁷ J mol⁻¹ K⁻¹) were improved in the case of the 5 wt% f-PJC/PETEP–CBz composite compared to those of the PETEP–CBz blended matrix and the f-PJC/PETEP–CBz composites with other weight percentages. Among the studied bio-carbon-reinforced hybrid composites with different weight percentages, the 5 wt% f-PJC/PETEP–CBz composite shows a higher value of char yield (38.37%), with an enhanced glass transition temperature of 285 °C and an improved water contact angle of 111.3°. Results obtained from corrosion studies infer that these hybrid composites exhibit improved corrosion resistance behaviour and effectively protect the surface of mild steel specimens from corrosion. It is concluded that the present work can be considered as an effective method for utilizing waste products and sustainable bio-materials for the development of high performance value-added hybrid composites for thermal and corrosion protection applications.

Schematic representation of development of functionalised Prosopis juliflora carbon (f-PJC) reinforced PET-epoxy resin (PETEP) blended bio-phenolic (cardanol) based benzoxazine (CBz) hybrid composites for high performance applications.     

Preparation of poly glycidyl methacrylate (PGMA) chain-grafted boron nitride/epoxy composites and their thermal conductivity properties

Surface modification of hexagonal boron nitride (h-BN) has the problem of reducing the interfacial thermal resistance, which has hindered its application in thermal conductive composites. Herein, poly glycidyl methacrylate (PGMA) chains were grafted onto the h-BN surface by simple radical polymerization; the thermal conductivity of epoxy (EP) composites was improved by adding the as-grafted h-BN–PGMA to EP resin. When the filling volume of h-BN–PGMA was 4, 10 or 16 vol%, the thermal conductivity of EP composite increased by 160%, 298% or 599%, respectively. Moreover, the h-BN surface modification was beneficial to enhance the compatibility between the filler and the EP matrix. Compared to EP/h-BN, the EP/h-BN–PGMA had higher thermal conductivity (1.197 W m⁻¹ K⁻¹) under the same filling amount (16 vol%). Moreover, excellent dielectric properties and thermal stability indicated that EP/h-BN–PGMA composites were excellent thermal interface materials (TIMs) and could be applied in the field of thermal management. The preparation process is environmentally friendly, easy to operate, and suitable for large-scale practical applications.

A schematic illustration of the preparation process of PGMA chain grafted h-BN.