Yu-Nan Chen

Polyvinyl chloride (PVC) is the most widely used general flame-retardant plastic worldwide; however, the large number of plasticizers added during processing significantly reduces its flame-retardant property. To prepare a new type of PVC material with highly efficient flame retardancy and smoke suppression, antimony trioxide (Sb₂O₃), talc powder, hydromagnesite, and zinc borate were added in different proportions to PVC to explore the flame-retardant properties, thermal weight, smoke density (Ds), and mechanical properties of the composite materials. Results showed that the limiting oxygen index value of each group was higher than 27% after adding talc powder, magnesite, and zinc borate to replace part of the Sb₂O₃. This value was within the refractory-grade level and indicated a good flame retardancy performance. The replacement effect was in line with the experimental expectation. The lowest Ds peak value was 656.4 when the flame retardants were added with 10 wt% Sb₂O₃, 50 wt% hydromagnesite, 20 wt% talc, and 20 wt% Zn₃BO₆. Compared with pure Sb₂O₃ as a flame retardant, the Ds peak value decreased by 46.7%. The thermogravimetric decomposition temperature of the composites in each group was generally higher than that of the group with pure Sb₂O₃ as a flame retardant, increasing by 45.3 °C. The thermal stability of the composites was improved, and the elongation at the break and tensile strength were 234.9% and 25.8 MPa, respectively, indicating good mechanical properties. The results showed that using compound flame retardants to replace most of the Sb₂O₃ is an effective technique for obtaining good flame retardancy and mechanical properties of PVC. This study, not only reduced the manufacturing cost of flame-retardant PVC, but also effectively reduced its smoke density and the time to reach the highest smoke density, which provided a research reference for the application and promotion of flame-retardant PVC.

In this study, hydromagnesite, a rare natural hydrated alkaline magnesium carbonate, was used to synthesize magnesium hydroxide (MH) as a flame retardant for ethylene-vinyl acetate (EVA) to enhance its fire resistance and smoke suppression. Various concentrations of sodium hydroxide (NaOH) were used to alter the morphology and the flame-retardant efficiency of synthesized MH. EVA/MH composites were prepared through melt blending, and the influence of NaOH on the flame retardancy and mechanical properties was investigated by means of the limiting oxygen index (LOI), cone calorimeter test (CCT) and tensile test. The flame retardancy results demonstrated that composites exhibited remarkably improved flame retardant properties after introducing MH, reflected by an increase in the LOI value from 20% for neat EVA to roughly 38%. Additionally, the peak of heat release rate (pHRR), the total heat release (THR) and the peak of the smoke production rate for EVA3 were decreased by 37.6%, 20.7% and 44.4% compared with neat EVA, respectively. In the meantime, increasing char residues were also observed. The incorporation of different MH concentrations had a limited effect on the mechanical properties of the EVA/MH composites.