Flame retardant polymeric nanocomposites through the combination of nanomaterials and conventional flame retardants

An anisotropic thermally conductive film with tailorable microstructures and macroproperties is fabricated using a layer-by-layer (LbL) assembly of graphene oxide (GO) and nanofibrillated cellulose (NFC) on a flexible NFC substrate driven by hydrogen bonding interactions, followed by chemical reduction process. The resulting NFC/reduced graphene oxide (RGO) hybrid film reveals an orderly hierarchical structure in which the RGO nanosheets exhibit a high degree of orientation along the in-plane direction. The assembly cycles dramatically increase the in-plane thermal conductivity (λX) of the hybrid film to 12.6 W·m–1·K–1, while the cross-plane thermal conductivity (λZ) shows a lower value of 0.042 W·m–1·K–1 in the hybrid film with 40 assembly cycles. The thermal conductivity anisotropy reaches up to λX/λZ = 279, which is substantially larger than that of similar polymeric nanocomposites, indicating that the LbL assembly on a flexible NFC substrate is an efficient technique for the preparation of polymeric n...

Highly Anisotropic Thermal Conductivity of Layer-by-Layer Assembled Nanofibrillated Cellulose/Graphene Nanosheets Hybrid Films for Thermal Management

With the fast-developing miniaturization and integration of microelectronics packaging materials, ultrahigh-voltage electrical devices, light-emitting diodes (LEDs), and in areas which require good heat dissipation and low thermal expansion, the investigations on the polymeric composites with highly thermal conductivities and excellent thermal stabilities are urgently required, which would be beneficial to transferring the heat to the outside of the products, finally to effectively avoid substantial overheating and prolong their working life. Our article reviews recent progress in the classification, measurement methods, model and equations, mechanisms, commonly used thermally conductive fillers, and the correlative fabrication methods for the thermally conductive polymeric composites, aiming to understand and grasp how to enhance the λ value effectively. And future perspectives, focusing scientific problems and technical difficulties of the present thermally conductive polymeric composites are also described and evaluated.

A review on thermally conductive polymeric composites: classification, measurement, model and equations, mechanism and fabrication methods

Rational distribution and orientation of boron nitride nanosheets (BNNSs) are very significant for a polymer/BNNS composite to obtain a high thermal conductivity at low filler content. In this paper, a high-performance thermal interface material based on exfoliated BNNSs and polystyrene (PS) microspheres was fabricated by latex blending and subsequent compression molding. In this case, BNNSs and PS microspheres first self-assembled to form the complex microspheres via strong electrostatic interactions between them. The as-prepared complex microspheres were further hot-pressed around the glass transition temperature, which brought the selective distribution of BNNSs at the interface of the deformed PS microspheres. As a consequence, a polymer composite with homogeneous dispersion and high in-plane orientation of BNNSs in PS matrix was obtained. Benefitted from this unique structure, the resultant composite exhibits a significant thermal conductivity enhancement of 8.0 W m–1 K–1 at a low filler content of 1...

Preparation of Highly Thermally Conductive Polymer Composite at Low Filler Content via a Self-Assembly Process between Polystyrene Microspheres and Boron Nitride Nanosheets

Graphene shows a great potential for high-performance thermally conductive composite applications because of its extremely high thermal conductivity. However, the graphene-based polymer composites reported so far only have a limited thermal conductivity, with the highest thermal conductivity enhancement (TCE) per 1 vol% graphene less than 900%. Here, a continuous network of graphene foam (GF), filled with aligned graphene nanosheets (GNs), is shown to be an ideal filler structure for thermally conductive composite materials. Compared to previous reports, a clear thermal percolation is observed at a low graphene loading fraction. The GNs/GF/natural rubber composite shows the highest TCE of 8100% (6.2 vol% graphene loading) ever reported at room temperature, which gives a record-high TCE per 1 vol% graphene of 1300%. Further analyses reveal a significant synergistic effect between the aligned GNs and 3D interconnected GF, which plays a key role in the formation of a thermal percolation network to remarkably improve the thermal conductivity of the composites. Additionally, the use of this composite for efficient heat dissipation of light-emitting diode (LED) lamps is demonstrated. These findings provide valuable guidance to design high-performance graphene-based thermally conductive materials, and open up the possibility for the use of graphene in high-power electronic devices.

Synergistic Effect of Aligned Graphene Nanosheets in Graphene Foam for High-Performance Thermally Conductive Composites.

The influence of polymer modifier chain length on the thermal conductivity of polyamide 6/graphene (GA) nanocomposites, including through-plane ( λ z ) and in-plane ( λ x ) directions were investigated. Here, three chain lengths of double amino-terminated polyethylene glycol (NH 2 –PEG–NH 2 ) were used to covalently functionalize graphene with graphene content of 5.0 wt%. Results showed that λ z was enhanced with the chain length of NH 2 –PEG–NH 2 increased, but λ x reached a maximum value at a certain chain length of NH 2 –PEG–NH 2 . The maximum λ z and λ x of GA are 0.406 W m −1  K −1 and 9.710 W m −1  K −1 , respectively. This study serves as a foundation for further research on the thermal conductive property of graphene nanocomposites using different chain lengths of polymer modifier to improve the λ z and λ x of the thermal conductive materials.

Effect of polymer modifier chain length on thermal conductive property of polyamide 6/graphene nanocomposites

Polylactide (PLA)/layered double hydroxide (LDH) films with good flame retardant property and transparency were synthesized by solution exfoliation and film casting method. The organic-inorganic interfacial interaction between PLA and NiAl-LDH was carefully modified by 2-carboxylethyl-phenyl-phosphinic acid (CEPPA) to well solve the dispersion problem of NiAl-LDH nanolayers and get enhanced flame retardancy of PLA composites. The results showed the NiAl-LDH/CEPPA (LC) nanolayers had exfoliated structures and were homogenously dispersed in PLA matrixes. All the PLA/LDH films had good transparency even LC content was up to 10 wt%. The PLA/LDH films absorbed the ultraviolet light, which alleviates the embrittlement of PLA films in the using procedure. The flame retardant effect characterized by microscale combustion calorimeter was observed when LC contents increased. The total heat release value of the sample with 10 wt% LC decreased to 9.7 kJ/g from 12.0 kJ/g of virgin PLA.

Phosphorus-containing flame retardant modified layered double hydroxides and their applications on polylactide film with good transparency.

Effect of polymer modifier chain length on thermal conductive property of polyamide 6/graphene nanocomposites Part A Applied science and manufacturing

The covalent functionalization of graphene oxide (GO) with bis(3-aminopropyl)-terminated poly(ethylene glycol) (NH2–PEG–NH2) and subsequent grafting with maleic anhydride grafted polypropylene (MAPP) oligomer matrix using reactive compatibilization were carefully analyzed and verified through detailed investigations. Improvements in the compatibility between the modified GO and the matrix, thermal stability, flame properties, and crystallization properties were achieved through the addition of a small amount of GO-grafted MAPP (PP-g-GO). Results of thermogravimetric and microscale combustion calorimetry analyses revealed an increase in Tmax by 51 °C and reductions in the total heat release and peak heat release rate by 44.4% and 38.9%, respectively, upon the addition of 2.0 wt % PP-g-GO relative to pure MAPP. The approach used in this work is an efficient strategy for improving the thermal behavior of polypropylene oligomer with a view toward extending its use in advanced technological applications.

Effect of Covalent-Functionalized Graphene Oxide with Polymer and Reactive Compatibilization on Thermal Properties of Maleic Anhydride Grafted Polypropylene

The invention relates to a polymer-grafted graphene oxide master batch and a preparation method thereof. The polymer-grafted graphene oxide master batch is characterized by comprising the following raw materials in percentage by weight: the graphene oxide is 1.5-2.5 percent of the polymer in accordance with 100 percent of the polymer content (based on 100 percent of the measurement standard), the content of hydrophilic modification agents is 1-2 times of the graphene oxide, and the mass of the activating agent is 1/10-1/5 of the hydrophilic modification agents. The polymer-grafted graphene oxide master batch and the preparation method of the polymer-grafted graphene oxide master batch have the characteristics that maleic anhydride grafted graphene oxide (MAPP-g-GO) is added into a composite material MAPP-g-GO/MAPP obtained in a basal body (MAPP); relative to the polymer without the modified graphene oxide, the composite material MAPP-g-GO/MAPP is high in flame retardant property, heat stability, crystallinity and the like; moreover, the heat conduction performance is also correspondingly improved.

Jingwen Yang

Papers

Effect of polymer modifier chain length on thermal conductive property of polyamide 6/graphene nanocomposites

Phosphorus-containing flame retardant modified layered double hydroxides and their applications on polylactide film with good transparency.

Effect of polymer modifier chain length on thermal conductive property of polyamide 6/graphene nanocomposites Part A Applied science and manufacturing

Effect of Covalent-Functionalized Graphene Oxide with Polymer and Reactive Compatibilization on Thermal Properties of Maleic Anhydride Grafted Polypropylene

Polymer-grafted graphene oxide master batch and preparation method thereof