Monitoring the degradation of physical properties and fire hazards of high-impact polystyrene composite with different ageing time in natural environments

Multifunctional nacre-like materials

Nacre, the iridescent inner layer of seashells, displays an exceptional combination of strength and toughness due to its 'brick-wall' architecture. Significant research has been devoted to replicating nacre's architecture and its associated deformation and failure mechanisms. Using the resulting materials in applications necessitates adding functionalities such as self-healing, force sensing, bioactivity, heat conductivity and resistance, transparency, and electromagnetic interference shielding. Herein, progress in the fabrication, mechanics, and multi-functionality of nacre-like materials, particularly over the past three years is systematically and critically reviewed. The fabrication techniques reviewed include 3D printing, freeze-casting, mixing/coating-assembling, and laser engraving. The mechanical properties of the resulting materials are discussed in comparison with their constituents and previously developed nacre mimics. Subsequently, the progress in incorporating multifunctionalities and the resulting physical, chemical, and biological properties are evaluated. We finally provide suggestions based on 3D/4D printing, advanced modelling techniques, and machine elements to make reprogrammable nacre-like components with complex shapes and small building blocks, tackling some of the main challenges in the science and translation of these materials.

Enhancing the flame retardancy and UV resistance of polyamide 6 by introducing ternary supramolecular aggregates

An integrated multi-functional additive was fabricated by successively grafting melamine (MEL) and phytic acid (PhA) on multiwalled carbon-nanotubes (MWNCTs), and was then applied in PA6 to improve the flame retardancy and light aging resistance of the composite. The limit oxygen index of PA6 composite containing 7 wt% PhA-MEL-MWCNTs was increased to 26.4 from 21.0. The smoke and CO release were significantly reduced by 48% and 88% respectively, and the severe melt dripping of PA6 in burning was eliminated. It is proved that PhA-MEL-MWCNTs can absorb ultraviolet (UV) radiation, and hence significantly reduces the mechanical property loss of the PA6 composite after UV aging. The tensile strength of the aged PA6/7 wt%PhA-MEL-MWCNTs composite sample only decreased by 18.1%, which was significantly lower than the loss rate of the control aged PA6 sample (62.5%). This protocol provides a new opportunity for fabricating long-life flame retardant polyamide composites.

Photo-catalytic and biotic degradation of polystyrene packaging film: Effect of zinc oxide photocatalyst nanoparticles and nanoclay

Synergistic effect of zinc oxide nanoparticles (ZnO-NPs) as photocatalyst and organonanoclay (ONC) as biodegradable promoter on the degradation of polystyrene (PS) film was investigated. The films were exposed to ultraviolet irradiation under ambient air at room temperature for photo-catalytic degradation and then submitted to biodegradation test in soil using respirometric procedure. Fourier-transform infrared and ultraviolet-visible spectroscopy, thermogravimetric analysis, colorimeter technique, contact angle measurement, and the carbon dioxide evolution results showed higher photo- and biodegradation efficiency of PS-ONC-ZnO nanocomposite compared to the neat PS, PS-ONC and PS-ZnO nanocomposites. Thermal stability, optical band gap, and water contact angle of photo-degraded PS-ONC-ZnO nanocomposite decreased by 11.37, 18.33 and 63.99%, respectively, while that of PS film was only 6.20, 6.44 and 5.84%, respectively. The photo-degraded PS-ONC-ZnO and PS-ZnO film indicated a biodegradation percentage value of 3.3 and 2.1%, respectively, over 16 weeks of incubation in soil. The possible degradation mechanism of nanocomposites was briefly discussed.

Design of fire alarm system of intelligent camera based on fuzzy recognition algorithm

Aiming at the problems of low fire detection accuracy and high false alarm rate of the current intelligent camera fire accident alarm system, a fire accident alarm system based on fuzzy recognition algorithm is designed. By analyzing the structural principle of the fire detection and alarm system, selecting the CO gas, temperature and smoke sensor selection, designing the corresponding fire signal detection circuit, and designing the single-chip system circuit, including the single-chip clock circuit, reset circuit, power supply circuit and A/D conversion circuit design, on the basis of in-depth study of the Bluetooth communication protocol structure, the hardware design of the serial interface circuit of the single-chip microcomputer, PC and Bluetooth module has been completed. The fuzzy recognition algorithm is used to set the input and output, establish the control rule table and reasoning relationship, generate the input and output rule table, preprocess the sensor signal, and finally output the fire alarm model through the fuzzy inference system, so as to realize the fire accident alarm of the intelligent camera. The experimental results show that the fire detection accuracy of the proposed method is high, and can effectively reduce the false alarm rate and false alarm rate of the system.

Synergistic Effects of Graphene and Ammonium Polyphosphate Modified with Vinyltrimethoxysilane on the Properties of High-Impact Polystyrene Composites

Ammonium polyphosphate (APP) was modified with a silane coupling agent (vinyltrimethoxysilane, Si-171), and then the synergistic flame retarding effect of graphene and surface-modified APP (APP@Si-171) on high-impact polystyrene (HIPS) was investigated. Surface modification and thermal stability characterization of APP were analyzed by Fourier transform infrared spectroscopy (FTIR), energy dispersive spectrometer (EDS), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results showed that surface-modified APP (APP@Si-171) exhibited significantly better dispersion and less agglomeration tendencies compared with pure APP. A series of target HIPS composites containing different mass fractions of the two flame retardants were prepared by melt blending. TGA and cone calorimeter tests (CCT) were conducted to quantitatively investigate the thermal and flammability properties of the composites, respectively. Results from TGA and CCT demonstrated that the addition of the flame retardants delayed the onset and peak temperatures in differential thermogravimetry (DTG) curves and weakened the peak heat release rate (PHRR) and total heat release (THR). Moreover, the synergistic effect index (SE) was employed to quantify the synergistic behavior between the two fillers, and the results showed that APP@Si-171 and graphene had a synergistic effect on improving the thermal stability and flame retardancy of HIPS.

Multi-sensor information fusion detection system for fire robot through back propagation neural network

Objective

To reduce the danger for firefighters and ensure the safety of firefighters as much as possible, based on the back propagation neural network (BPNN) the fire sensor multi-sensor information fusion detection system is investigated.

Method

According to previous studies, the information sources and information processing methods for the design of this study are first explained. Then, the basic structure and flowchart of the research object in this study are designed. Based on the structure diagram and flowchart, the BPNN is selected to fuse the feature layers in this study, and the fuzzy control is selected to fuse the decision layers in this study. The multi-sensor information fusion detection system collects information for the sensors first, processes the collected information, and sends it to the processor of the robot. The processor analyzes and processes the received signal, and transmits the obtained information to the control terminal through the wireless communication system.

Results

Through the tests in this study, it is found that when the number of hidden layer nodes of the BPNN is 7, the optimal training result is obtained. On this basis, the test of BPNN in this study is performed. The test results show that after 127 iterations, the error of the BPNN reaches the lowest target value, indicating that the BPNN achieves an excellent level of accuracy. The trained BPNN has a running time of 0.0276 s and a mean square error of 0.0013. The smaller the mean square error value is, the higher the accuracy of the BPNN is, which shows that the BPNN meets the high precision requirements of this study.

Conclusion

The research on the multi-sensor information fusion detection system of fire robots in this study can provide theoretical support for the research on forest fire detection in China. Since the proposed BPNN-based robot is applied to the inspection and processing of forest remaining fire, the results are applicable to the forests of various countries, with a wide range of applications.

Nacre-Inspired Tunable Electromagnetic Interference Shielding Sandwich Films with Superior Mechanical and Fire-Resistant Protective Performance

With the rapidly increasing development of portable device hardware and flexible electronics, ultrathin electromagnetic interference (EMI) shielding films with a combination of high flexibility and excellent mechanical properties are noticeably required. In addition to minimizing the electromagnetic wave pollution problem, the fire hazards caused by accidental electrical leakage or aging are also a cause of extensive concern. Inspired by nacre and sandwich structure, herein, we fabricated for the first time an electrical insulating sandwich-structured film based on Ca ion cross-linked sodium alginate (SA)-montmorillonite (MMT) and Ti₃C₂T_x MXene through a step-by-step vacuum-assisted filtration process. This novel design strategy not only maintains the inner EMI shielding network but also can act as an excellent fire-resistant barrier to protect the electronic device in case of accidental fire. Compared with the pure Ti₃C₂T_x layer, such kind of sandwich film can effectively maintain the EMI shielding performance (50.01 dB), dramatically enhance the mechanical properties (84.4 MPa), and exhibit excellent fire-resistant performance. Especially, compared with the film composed of mixture, the EMI shielding effectiveness value is only 55% that of sandwich films. Besides, it functions well under long-term heat aging test at 80 °C. Therefore, this unique design provides a novel EMI material strategy to facilitate its future applications in flexible electronics.

Estimation of Mechanical Performance, Thermal Stability and Flame Retardancy of High-Impact Polystyrene/Surface-Modified APP/Carboxylic-Functionalized MWCNTs Nanocomposites

An ammonium polyphosphate (APP) surface-modified by silane coupling agent was used as flame retardant in high-impact polystyrene (HIPS). A series of HIPS nanocomposites containing different mass fractions of APP (k-APP) surface-modified by silane coupling agent (3-aminopropyl triethoxysilane, KH 550) and carboxylic-functionalized MWCNTs (COOH–MWCNTs) were prepared by the melt blending method. A composite only containing APP was also prepared as a reference material. Scanning electron microscopy (SEM) was employed to investigate the dispersion of the fillers into the HIPS matrix, and it was found the hydrophobic groups on the k-APP surface would greatly enhance the dispersion and prevent agglomerations compared with APP. Furthermore, the COOH–MWCNTs also showed good dispersibility into the matrix. Mechanical tests of the nanocomposites revealed that k-APP exhibits a more beneficial effect on both tensile and flexural properties compared with APP. Thermogravimetric analysis (TGA) and cone calorimeter tests (CCT) were conducted to probe the thermal and flammability properties of the nanocomposites, respectively. The synergistic effects of k-APP and COOH–MWCNTs on mechanical, thermal and flammability properties were examined as well.