Synthesis of a Carrageenan-Iron Complex and Its Effect on Flame Retardancy and Smoke Suppression for Waterborne Epoxy

Lignin-based flame retardants chelated with Fe3+: Facilitating the development of flame retardant, UV resistant and antibacterial properties polyvinyl alcohol composites

To overcome the problems of inflammability, poor UV resistance and susceptible to bacterial growth of polyvinyl alcohol (PVA), a new lignin-based PVA composite (PVA/PLig-Fe) was prepared. Compared to PVA, the limiting oxygen index (LOI) of PVA/PLig-Fe was increased by 64.8 %. The peak heat release rate (PHRR) and total heat release (THR) were reduced from 247.40 kW/m2 and 8.26 MJ/m2 of pure PVA to 151.70 kW/m2 and 6.95 MJ/m2, respectively. In addition, the total smoke production (TSP) of the modified sample was reduced from 3.11 m2 to 1.87 m2 compared with PVA. Notably, the elongation at break and tensile strength of PVA/PLig-Fe increased from 188 % and 35 MPa to 247 % and 53 MPa, and its transmittance of UVA (TUVA) and transmittance of UVB (TUVB) were reduced to 0.54 % and 0.59 %, respectively. Besides, the treated samples demonstrated 99.95 % and 99.90 % antibacterial activity against E. coli and S. aureus, respectively. The present research provides a feasible approach for the development of flame retardant, enhanced mechanical properties, UV resistant, and antibacterial PVA composites as a promising application in packaging.

Intumescent flame retardancy and smoke suppression of Eucommia ulmoides gum/natural rubber blends based on synergistic g-C3N4@Fe3O4 nanocomposites

A flame retardant synergist (g-C3N4@Fe3O4) was designed through an in situ co-precipitation method by using graphitized carbon nitride (g-C3N4) and Fe3O4, and its structure was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). A series of different contents of g-C3N4@Fe3O4 and intumescent flame retardant (IFR) were simultaneously added into eucommia ulmoides gum/natural rubber (EUG/NR) blends to improve the flame retardancy and reduce the smoke release. The flame retardancy, smoke suppression performance, thermal degradation behaviors and thermal stability of EUG/NR blends were evaluated by the limiting oxygen index (LOI), UL-94, cone calorimetry test (CCT) and thermogravimetric analysis (TGA). The results showed that using g-C3N4@Fe3O4 as a flame retardant synergist, the LOI value of the 9 phr g-C3N4@Fe3O4 synergist (EUG/NR 5) blend was 29.5%, which was much higher than the 20.0% of the original composite. Moreover, the 6 phr g-C3N4@Fe3O4 synergist (EUG/NR 4) and EUG/NR 5 passed the UL-94 V-0 rating, while the pristine EUG/NR blends showed no rating. Moreover, the total heat release rate (THR), peak of heat release rate (PHRR) and total smoke production (TSP) of the EUG/NR blends in the CCT test were much lower than those of the pristine EUG/NR blends. In particular, PHRR, THR and TSP of EUG/NR 5 decreased by 37.1%, 16.2% and 18.0%, respectively. This indicated that the introduction of g-C3N4@Fe3O4 decreased the release of combustible gases. TGA results also showed that the addition of g-C3N4@Fe3O4 accelerated the thermal degradation of the EUG/NR blends and changed the thermal degradation mechanism of the EUG/NR blends, indicating the synergistic effect of g-C3N4@Fe3O4. Finally, a possible degradation mechanism of EUG/NR blend composites was proposed.

Surface Modification of Ammonium Polyphosphate for Enhancing Flame-Retardant Properties of Thermoplastic Polyurethane

Currently, the development of efficient and environmentally friendly flame-retardant thermoplastic polyurethane (TPU) composite materials has caused extensive research. Ammonium polyphosphate (APP) is used as a general intumescent flame retardant to improve the flame retardancy of TPU. In this paper, we developed a functionalized APP flame retardant (APP-Cu@PDA). Adding only 5 wt% of APP-Cu@PDA into TPU can significantly improve the flame-retardant's performance of the composite material, reflected by a high LOI value of 28% with a UL-94 test of V-0 rating. Compared with pure TPU, the peak heat release rate, total heat release, peak smoke release rate, and total smoke release were reduced by 82%, 25%, 50%, and 29%, respectively. The improvements on the flame-retardant properties of the TPU/5%APP-Cu@PDA composites were due to the following explanations: Cu²⁺-chelated PDA has a certain catalytic effect on the carbonization process, which can promote the formation of complete carbon layers and hinder the transfer of heat and oxygen. In addition, after adding 5% APP-Cu@PDA, the tensile strength and elongation at the break of TPU composites did not decrease significantly. In summary, we developed a new flame-retardant APP-Cu@PDA, which has better flame-retardant properties than many reported TPU composites, and its preparation process is simple and environmentally friendly. This process can be applied to the industrial production of flame retardants in the future.

The Toxicological Testing and Thermal Decomposition of Drive and Transport Belts Made of Thermoplastic Multilayer Polymer Materials

The article presents the potential impact of flat drive and transport belts on people's safety during a fire. The analysis distinguished belts made of classically used fabric-rubber composite materials reinforced with cord and currently used multilayer polymer composites. Moreover, the products' multilayers during the thermal decomposition and combustion can be a source of emissions for unpredictable and toxic substances with different concentrations and compositions. In the evaluation of the compared belts, a testing methodology was used to determine the toxicometric indicators (W_LC50SM) on the basis of which it was possible to determine the toxicity of thermal decomposition and combustion products in agreement with the standards in force in several countries of the EU and Russia. The analysis was carried out on the basis of the registration of emissions of chemical compounds during the thermal decomposition and combustion of polymer materials at three different temperatures. Moreover, the degradation kinetics of the polymeric belts by using the thermogravimetric (TGA) technique was evaluated. Test results have shown that products of thermal decomposition resulting from the neoprene (NE22), leder leder (LL2), thermoplastic connection (TC), and extra high top cower (XH) belts can be characterized as moderately toxic or toxic. Their toxicity significantly increases with the increasing temperature of thermal decomposition or combustion, especially above 450 °C. The results showed that the belts made of several layers of polyamide can be considered the least toxic in fire conditions. The TGA results showed that NBR/PA/PA/NBR belt made with two layers of polyamide and the acrylonitrile-butadiene rubber has the highest thermal stability in comparison to other belts.

Modified Epoxy Resin Synthesis from Phosphorus-Containing Polyol and Physical Changes Studies in the Synthesized Products

Epoxy resins are commonly used to manufacture the molding compounds, reinforced plastics, coatings, or adhesives required in various industries. However, the demand for new epoxy resins has increased to satisfy diverse industrial requirements such as enhanced mechanical properties, thermal stability, or electrical properties. Therefore, in this study, we synthesized new epoxy resin (PPME) by modifying phosphorous-containing polyol. The prepared resin was analyzed and added to epoxy compositions in various quantities. The compositions were cured at high temperatures to obtain plastics to further test the mechanical and thermal properties of the epoxy resin. The measured tensile and flexural strength of epoxy compositions were similar to the composition without synthesized epoxy resin. However, the heat release rates of the compositions exhibited tendencies of a decrease proportional to the amount of PPME.