Fire retardant coatings are moving towards environmentally friendly products, and the development of green flame retardants is gradually attracting the attention of researchers. In this work, spent coffee grounds (SCG) were modified with m-xylylenediamine phosphate ammonium (MAP) to create a bio-based flame retardant (SCG-g-MAP) for waterborne epoxy resin (WEP). The structure and composition of SCG-g-MAP were analyzed by a range of characterization tests, and the effects of SCG-g-MAP on the thermal stability, flame retardancy and fire resistance of WEP composite coatings were discussed. It revealed that WEP composite coating with 10% SCG-g-MAP and partial conventional intumescent fire retardant fillers, resulted in a LOI value of 29.5% and self-extinguishing capability. Moreover, the coating exhibited significantly improved fire resistance and thermal insulation properties due to its better thermal stability and excellent barrier function of forming carbon layer. This work presents a new attempt and inspiration for the application of biomass waste such as SCG for green flame retardant fillers.
Simultaneously improving the thermal conductivity and flame resistance of epoxy composite is still a challenge. Herein, a novel epoxy composite with high thermal conductivity and greatly enhanced flame retardancy was developed through constructing integrated three-dimensional (3D) network based on boron nitride (BN), talc, ammonium polyphosphate (APP). The thermal conductivity of the composite with filler network reached 3.04 Wm −1 K −1 , which was 15.2 and 3.1 times of those of pure epoxy and sample with random filler distribution. The LOI value of the composite with filler network reached 37.8%, which was 1.9 and 1.4 times of those of pure epoxy and sample with random filler distribution, respectively. In addition, the effects of various combinations of filler on the flame resistance of the epoxy composite were also evaluated. The prepared composite with filler network exhibited excellent shape stability and mechanical strength even after ablation at 1000°C. The network structure constructed by BN had a positive effect on heat transfer, while APP led to the formation of phosphoric acid at high temperature, adhering to talc and other residues together. A ceramic-like residue was formed on the firing surface, which enhanced the barrier effect of char layer and flame resistance of the composite.
Phase separation between SGFs and phosphates promotes formation of cristobalite at high temperature, which leads to improvements in ceramifiable properties.
Abstract A cost-efficient and practical strategy was developed for preparing high thermal conductive epoxy packaging composites. The effective conductive network was constructed by the bridging effect between boron nitride (BN) and spherical silica (SiO 2 ). Compared to the epoxy (EP) composites with randomly dispersed BN and SiO 2 , the EP/SiO 2 @BN showed a great enhancement in thermal conduction. The thermal conductivity of EP/SiO 2 @BN reached to 0.86 W m −1 K −1 with 60 wt% content of hybrid filler, which was 91% higher than that of EP/SiO 2 samples and was around 12% higher than that of epoxy composites with unmodified BN and SiO 2 . In addition, the EP/SiO 2 @BN exhibited lower thermal interface resistance in comparison with EP/SiO 2 &BN composites according to the effective medium theory (EMT). The encapsulation of BN on the surface of SiO 2 greatly enhanced the thermal transfer efficiency of the epoxy matrix and showed great potential in the epoxy packaging practical application.
Preparing composites from gricultural waste with biodegradable polymers is one of the strategies used to ensure the long-term sustainability of such materials. However, due to the differences in their chemical properties, biomass fillers often exhibit poor interfacial adhesion with polymer matrices. Inspired by mussel foot silk, this work focused on the surface modification of coffee grounds (CGs) using a combination of tannic acid (TA) and alkali treatment. CGs were used as a biomass filler to prepare polybutylene adipate terephthalate (PBAT)/CG composites. The modification of CGs was demonstrated by Fourier transform infrared spectroscopy (FTIR), the water contact angle, and scanning electron microscopy (SEM). The effect of CGs on the rheological, tensile, and thermal properties of the PBAT/CG composites was investigated. The results showed that the addition of CGs increased the complex viscosity, and the surface modification enhanced the matrix-filler adhesion. Compared with unmodified CG composites, the tensile strength and the elongation at break of the composite with TA-modified alkali-treated CGs increased by 47.0% and 53.6%, respectively. Although the addition of CGs slightly decreased the thermal stability of PBAT composites, this did not affect the melting processing of PBAT, which often occurs under 200 °C. This approach could provide a novel method for effectively using biomass waste, such as coffee grounds, as fillers for the preparation of polymer composites.
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