Healing mechanism of cotton bandages loaded with PNIPAM/GO-Ag hydrogel on deep second-degree burn wounds in a rat model.

Dressings play a crucial role in the management of burn wounds. In this study, cotton bandages were modified with poly (N-isopropylacrylamide)/graphite oxide/nano silver (PNIPAM/GO-Ag) hydrogel to obtain a novel dressing (PNIPAM/GO-Ag/COT). The healing effect of the PNIPAM/GO-Ag/COT dressing on deep second-degree burn wounds in rats and the changes of related inflammatory factors were explored and analyzed systematically. The deep second-degree burn model was established by the steam scald method in Sprague-Dawley (SD) rats. The granulation tissue, collagen deposition, the expression of tumor necrosis factor-α (TNF-α), and basic fibroblast growth factor (bFGF) in the wound were evaluated by means of HE staining, Masson staining, ELISA, and immunohistochemistry methods. The results showed that, compared with the blank group (rats without the dressing treatment), the PNIPAM/GO-Ag/COT dressing reduced the expression of TNF-α by approximately 18 % and promoted the bFGF expression in wound tissue. Compared to the control group (rats with the gauze treatment), the wound healing rate in the PNIPAM/GO-Ag/COT dressing group was 58 % on the 14th day, with an increase of 30 %. These results demonstrated that the PNIPAM/GO-Ag/COT dressing primarily promoted burn wound healing by reducing inflammatory reactions, promoting collagen deposition, and enhancing the expression of bFGF.

Cooperative Effect of Ni-Decorated Monolayer WS2, NiO, and AC on Improving the Flame Retardancy and Mechanical Property of Polypropylene Blends.

Improving the residual char of polypropylene (PP) is difficult due to the preferential complete combustion. Here, we designed a combination catalyst that not only provides physical barrier effects, but also dramatically promotes catalytic charring activity. We successfully synthesized WS2 monolayer sheets decorated with isolated Ni atoms that bond covalently to sulfur vacancies on the basal planes via thiourea. Subsequently, PP blends composed of 8 wt.% Ni-decorated WS2, NiO, and activated carbon (AC) were obtained (ENi-SWS2-AC-PP). Combining the physical barrier effects of WS2 monolayer sheets with the excellent catalytic carbonization ability of the ENi-SWS2-AC combination catalyst, the PP blends showed a remarkable improvement in flame retardancy, with the yield of residual char reaching as high as 41.6 wt.%. According to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, it was revealed that the microstructure of residual char contained a large number of carbon nanotubes. The production of a large amount of residual char not only reduced the release of pyrolytic products, but also formed a thermal shield preventing oxygen and heat transport. Compared to pure PP, the peak heat release rate (pHRR) and total heat release rate (THR) of ENi-SWS2-AC-PP were reduced by 46.32% and 26.03%, respectively. Furthermore, benefiting from the highly dispersed WS2, the tensile strength and Young's modulus of ENi-SWS2-AC-PP showed similar values to pure PP, without sacrificing the toughness.

Synergistic Effect of Activated Carbon, NiO and Al2O3 on Improving the Thermal Stability and Flame Retardancy of Polypropylene Composites.

It is difficult to enhance the char yields of polypropylene (PP) due to the preferential complete combustion. Successful formation of abundant char layer structure of PP upon flammability was obtained due to the synergistic effect of NiO, Al2O3 and activated carbon (AC). From characterization of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it was revealed that the microstructure of residual char contained large amount of carbon nanotubes. Compared to the modification of AC, NiO and Al2O3 alone, the combination of AC, NiO and Al2O3 dramatically promotes the charring ability of PP. In the case of AC and NiO, NiO plays a role of dehydrogenation, resulting in the degradation product, while AC mainly acts as carbonization promoter. The addition of Al2O3 results in higher dispersion and smaller particle size of NiO, leading to greater exposure of active sites of NiO and higher dehydrogenation and carbonization activity. Compared to the neat PP, the decomposition temperature of the PP modified by combined AC, NiO and Al2O3 was increased by 90 ℃. The yield of residual char of AC-5Ni-Al-PP reached as high as 44.6%. From the cone calorimeter test, the heat release rate per unit area (HRR) and total heat release per unit area (THR) of PP composite follows the order AC-5Ni-Al-PP < AC-10Ni-Al-PP < AC-Ni-PP < AC-15Ni-Al-PP < AC-1Ni-Al-PP. Compared to the neat PP, the peak of HRR declined by 73.8%, 72.7%, 71.3%, 67.6% and 62.5%, respectively.

Construction of Carbon Microspheres-Based Silane Melamine Phosphate Hybrids for Flame Retardant Poly(ethylene Terephthalate).

To improve the flame retardancy and inhibit the smoke of poly(ethylene terephthalate) (PET), carbon microspheres (CMSs)-based melamine phosphate (MP) hybrids (MP-CMSs) were constructed in situ with the introduction of CMSs into the hydrothermal reaction system of MP. The integrated MP-CMSs were modified by 3-Aminopropyltriethoxysilane (APTS) to obtain the silane MP-CMSs (SiMP-CMSs) to strengthen the interface binding between the MP-CMSs and PET matrix. The results showed that the SiMP layer was loaded on the CMSs surface. The addition of only 3% SiMP-CMSs increased the limiting oxygen index (LOI) value of the PET from 21% ± 0.1% to 27.7% ± 0.3%, reaching a V-0 burning rate. The SiMP-CMSs not only reduced heat damage, but also inhibited the smoke release during PET combustion, whereupon the peak heat release rate (pk-HRR) reduced from 513.2 to 221.7 kW/m², and the smoke parameters (SP) decreased from 229830.2 to 81892.3 kW/kg. The fire performance index (FPI) rose from 0.07 m²s/kW to 0.17 m²s/kW, demonstrating the lower fire risk. The proportion of the flame-retardant mode in the physical barrier, flame inhibition, and char effects were recorded as 44.53%, 19.04%, and 9.04%, respectively.