| Acrylonitrile-butadiene-styrene (ABS) is a widely used thermoplastic material owing to its good mechanical properties, chemical resistance and processing advantages. One of the main drawbacks of ABS is its inherent flammability, and therefore in many application cases, it is necessary to construct a flame retarded composition for ABS resin. Intumescent flame retardant (IFR) is widely used due to its high efficiency and environmental friendly. But the major raw materials for the synthesis of IFR are harmful POCl3 and PCl3, and the reaction demanded absolutely dry conditions. In addition, all of the raw materials for producing IFR are from fossil resources, which are non-renewable. If biomass resources can partly replace fossil resources to produce IFR, it will provide a new way for sustainable development of IFR.A novel phosphorus-containing flame retardant, Poly(DPA-PDCP), was synthesized by interfacial polycondensation from DPA (diphenolic acid), a compound produced from biomass resources. The effects of reaction time, tetrabutyl ammonium chloride (TBAC) dosage and NaOH dosage on yields were studied. Results showed that the optimal reaction conditions are as follows: nTBAC/nDPA=4%, nNAOH/nDPA=3, temperature 25℃, reaction time 1h. The yield of the product was about 75%. Poly(DPA-PDCP) was characterized by FTIR, 1H NMR and TGA. The results showed that Pbly(DPA-PDCP) had excellent thermal stability and charring ability.ABS/APP/Poly(DPA-PDCP) composites were prepared by melt blending. Thermal stability and flammability were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and cone calorimetric test. TGA showed that the addition of Poly(DPA-PDCP) and APP together enhanced the thermal stability of ABS, decreased the degradation rate and improved greatly the weight of residues. At the sametime, the flame retardance of ABS is improved significantly, which is reflected by the reduction of peak heat release rate (PHRR), total heat release (THR) and average mass loss rate (AMLR) by the cone calorimetric tests and the increase of LOI value. When the mass ratio of Poly(DPA-PDCP) and APP was 1:4, the system showed the best synergistic flame-ratardant effect. The mechanism of Poly(DPA-PDCP)/APP is the solid-phase flame-retardant mechanism, with Poly(DPA-PDCP) act as carbon resource and APP act as acid resource and gas resource. The intact intumescent char was formed after combustion and it can protect the ABS resin effectively.Synergistic effects between Poly(DPA-PDCP)/APP (mass ratio 1:4) and expandable graphite (EG) during combustion for improving the flame retardancy of ABS resin were also studied. Thermal stability and flammability were investigated with different ratio between Poly(DPA-PDCP)/APP and EG. The results showed that when the mass ratio of Poly(DPA-PDCP)/APP (1:4) and EG was 1:1, the treated ABS had the best flame-ratardant properity. An LOI value of 32.6% and UL-94 V-0 rating can be achieved. Meanwhile, morphology of the residues obtained from burning flame retarded ABS in LOI test was studied through the SEM observations and rich compact char layers could explain the excellent flame retardance. EG formed graphite sheets after combustion, which constituted a skeleton of char layer. At the same time, the storage modulus (E') and glass transition (Tg) of the flame retarded ABS was increased greatly by addition of EG. The results showed that the use of EG together with Poly(DPA-PDCP)/APP can improve the flame retardancy and mechnical property of ABS resin. |
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