Linsheng Tang

The synergistic fire retardancy of modified melamine resin with pentaerythritol (MF‐PER, a novel green and effective triazine charring agent), and ammonium polyphosphate (APP) in polypropylene was investigated by UL‐94 test, LOI measurement, and cone calorimetry test. It is found that the synergism of MF‐PER is obviously better than pentaerythritol (PER). MF‐PER/APP imparts a fire retardancy mainly by the following mode: in burning process, MF‐PER, and APP are first pyrolyzed respectively into polyols and polyphosphoric acid, which is esterified to form phosphoric ester, and the inert gases make the molten residues foaming; When the temperature increases, and polyphosphoric acid is dehydrated to polymetaphosphoric acid, which dehydrates phosphoric ester to form an intumescent char layer, inducing a fire retardant effect by barrier effect. The graphitization degree of the cone calorimetry test residues of the FR‐PP with MF‐PER is higher than that with PER, which leads to a better synergism. Highlights: Melamine formaldehyde resins modified with pentaerythritol (MF‐PER) as a novel triazine charring agent was designed and synthesized. MF‐PER is synthesized by solid phase method and using hexahydroxymethyl melamine (HMM) instead of cyanuric chloride as raw material, so the emission of three wastes in its synthesis process is very little, only a small amount of formaldehyde and water are produced. MF‐PER has excellent synergistic fire retardancy with APP in polypropylene. The highly efficient and environmentally benign charring agent show great potential for developing more efficient and eco‐friendly IFR.

1-Butene, as one of the widely used chemical raw materials, can be produced by the double bond isomerization of 2-butene. However, the current yield of the isomerization reaction is only up to 20% or so. It is therefore an urgent issue to develop novel catalysts with higher performances. In this work, a high-activity ZrO₂@C catalyst that is derived from UiO-66(Zr) is fabricated. The catalyst is prepared by calcining the precursor UiO-66(Zr) at high temperature in nitrogen, and characterized by XRD, TG, BET, SEM/TEM, XPS and NH₃-TPD. The results demonstrate that the calcination temperature has significant influences on the catalyst structure and performance. Regarding the catalyst ZrO₂@C-500, the selectivity and yield of 1-butene are 94.0% and 35.1%, respectively. The high performance is due to multiple aspects, including the inherited octahedral morphology from parent UiO-66(Zr), suitable medium-strong acidic active sites and high surface area. The present work will lead to a better understanding of the ZrO₂@C catalyst and guide the rational design of high-activity catalysts for the double bond isomerization of 2-butene to 1-butene.

In order to improve the flame retardant efficiency and smoke‐suppression of piperazine pyrophosphate/melamine cyanurate (PPAP/MCA) in PP, the synergism of ZnO and PPAP/MCA was investigated by limiting oxygen index (LOI) determination, UL‐94 test, and cone calorimetry test (CCT). It is found that ZnO performs an exceptional synergism in flame retardant effect and inhibition on the flame propagation. Besides, ZnO can significantly inhibit the production of the smoke and CO. The TGA of the PP composites, the component and structure analysis of the heated composites and CCT residues reveal that ZnO performs the synergism primarily by the following modes: ZnO promotes obviously the charring of the composite, and improves the thermal stability as well as the strength of the intumescent layer, which brings about an improved flame retardant property and inhibiting ability on the flame propagation.

Summary: The fire‐retardant synergy of bis(1‐methoxy‐2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate (NORSM) and melamine hydrobromide (MHB)/aluminum diethylphosphinate (ADEP) in polypropylene (PP) has been studied using UL‐94 tests, limiting oxygen index (LOI) determination, and cone calorimetry tests (CCTs). The results indicate that NORSM exhibits exceptional fire‐retardant synergy with ADEP/MHB in PP. For a PP composite with 1.0 wt% of MHB and 1.5 wt% of ADEP, the LOI increased from 19.0% to 26.0%, fire retardation effectivity increased from 0.48 to 2.93, synergy effectivity was as high as 1.99, UL‐94 level was enhanced from none to V‐2, fire performance index increased from 56.4 to 84.8, and various heat release values decreased significantly when the PP composite just discussed combining 0.30 wt% of NORSM. NORSM plays a role in synergy with ADEP/MHB primarily through the following modes: radicals such as CH₃O· and aminyl formed by the decomposition of NORSM; PO₂·, PO·, and HPO· formed from ADEP; HBr formed from MHB; and quench active radicals such as HO· for combustion and breaking down the radical source, which terminates the chain oxidation reaction for combustion, leading to more exceptional fire retardation in the gaseous phase.

Summary: Synergistic flame retardancy of bis(1‐methoxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl)sebacate (NORSM) and aluminium hypophosphite (ALHP)/melamine hydrobromide (MHB) in polypropylene (PP) was studied by limiting oxygen index (LOI) determination, UL‐94 test and cone calorimetry test. The results reveal that NORSM, together with ALHP/MHB, has an exceptional synergistic flame retardant effect in PP. For the FR‐PP containing 1.0 wt% of ALHP and 1.5 wt% of MHB, combining NORSM in 0.30 wt% concentration can make its LOI increases from 19.0% to 26.3%, the flame retardant effectivity increases from 0.48 to 3.04, the synergistic effectivity is as high as 2.03, the UL‐94 rating is improved from none to V‐2, the fire performance index increases from 58.7 to 91.3, various heat release parameter values are reduced obviously. It is confirmed that NORSM plays the role of synergism with ALHP/MHB mainly through the following mechanisms: the active radicals such as methyl radicals, methoxy radicals, nitro radicals, and aminyl radicals produced by the pyrolysis of NORSM, together with PH₃ and HBr, quench active free radical such as ·OH, so the chain reaction of combustion is interrupted and results in a more efficient flame retardant effect in gaseous phase.

Fire‐retardant synergy of tris(1‐methoxy‐2,2,6,6‐tetramethyl‐4‐piperidinyl) phosphite (NORPM) and aluminum hypophosphite (ALHP)/melamine hydrobromide (MHB) in polypropylene (PP) was researched by limiting oxygen index (LOI) measurement, vertical burning test, and cone calorimetric test (CCT). The results reveal that NORPM, together with ALHP/MHB, has an exceptional fire‐retardant synergy in PP. For the FR‐PP containing 1.0 wt% of ALHP and 1.5 wt% of MHB, combining NORPM in 0.20 wt% concentration can make its LOI value increases from 19.0% to 26.1%, the fire‐retardant efficiency (EFF) increases from 0.48 to 3.07, synergistic efficiency (SE) is as high as 2.18, the vertical combustion rating can be improved from none to UL 94 V‐2, fire performance index (FPI) increases from 58.7 to 84.9, and various heat release parameter values are reduced markedly. NORPM induces the synergy with ALHP/MHB primarily by the mechanisms as follows: active free radicals formed through the decomposition of NORPM, such as CH ₃ , CH ₃ O, nitro radicals and amino radicals, together with PH ₃ and HBr, trap active radicals (HO·) for combustion. Consequently, the reaction chain of combustion is terminated, which makes gaseous phase fire retardancy more efficient.

Summary: Synergistic flame retardancy of tris(1‐methoxy‐2,2,6,6‐tetramethyl‐piperidin‐4‐yl) phosphite (NORPM) and tris(2,4,6‐tribromophenoxy)‐1,3,5‐triazine (TTBPC)/Sb₂O₃ in high‐impact polystyrene (HIPS) was studied by limiting oxygen index (LOI) determination, UL‐94 test, and cone calorimetry test (CCT). NORPM has an exceptional synergistic effect in HIPS. When the dosage of TTBPC, Sb₂O₃, and NORPM was 12.8, 3.2, and 0.5 wt% respectively, flame retardant effectivity and synergistic effectivity were 0.424 and 1.15 respectively. Compared with the Flame retardant (FR)‐HIPS containing 16.0 wt% of TTBPC/Sb₂O₃, the LOI of FR‐HIPS increases from 23.8% to 25.4%, the flame‐retardant rating of FR‐HIPS can be improved from UL 94 V‐2 to V‐0, and the peak heat release rate and total heat release are significantly reduced by combining NORPM in 0.5 wt% concentration. NORPM induces the synergistic effect mainly through the following mechanisms: the active radicals produced by the pyrolysis of NORPM promote the release of bromine radicals from TTBPC and the formation of HBr, which improves the flame retardancy of TTBPC; the above active radicals, together with HBr, quench active free radicals, such as the hydroxyl radical (·OH) and decompose the free radical source, which interrupts the chain reaction during combustion and results in a more efficient flame retardant effect in gaseous phase.

Bis(1‐methoxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl)sebacate (NORSM) was found to perform an exceptional synergistic effect with tris(2,4,6‐tribromophenoxy)‐1,3,5‐triazine (TTBPC)/Sb₂O₃ in HIPS. The LOI of fire retardant HIPS (FR‐HIPS) with 16 wt% of TTBPC/Sb₂O₃ increased from 23.8% to 25.2%, the flame retardant rating of FR‐HIPS was improved from UL 94 V‐2 to UL 94 V‐0, and various heat release parameters such as peak heat release rate, total heat release, and mean effective heat of combustion were greatly lowered by combining NORSM of 0.50 wt%. The Py‐GC/MS results revealed that NORSM induced the role of synergistic effect; the main mechanisms were as follows: the active radicals such as methoxy radicals and aminyl radicals produced by the pyrolysis of NORSM promote the release of bromine radicals from TTBPC and the formation of HBr and CO₂, which improves the flame retardancy of TTBPC/Sb₂O₃; the above active radicals, together with HBr, quench active free radicals, such as the hydroxyl radical (OH), and decompose the free radical source, which interrupts the chain reaction during combustion and results in a more efficient flame retardant effect in gaseous phase.