A flame-retardant polylactic acid composite added with piperazine pyrophosphate and melamine cyanurate was developed. Piperazine pyrophosphate and melamine cyanurate showed synergistic effect in the polylactic acid composites. When the weight ratio of piperazine pyrophosphate to melamine cyanurate was 4:1 and the loading of the piperazine pyrophosphate/melamine cyanurate flame retardant was 15 wt.%, the prepared polylactic acid composites passed V-0 rating in the UL-94 test and achieved the high limit oxygen index value of 34.9%. The cone calorimeter test result confirmed that the addition of piperazine pyrophosphate/melamine cyanurate flame retardant reduced the total heat release value of polylactic acid. The effect of polylactic acid biodegradation on the flame retardancy of polylactic acid composite was further discussed. The biodegraded polylactic acid, which was exposed to the air for 8 months, showed high flame retardancy and even passed V-0 rating in the UL-94 test without the addition of piperazine pyrophosphate/melamine cyanurate flame retardant, which proved that biodegradation could affect the flame retardancy of polylactic acid.
In this study, a magnesium phosphate whisker (DPM-H) was synthesized by the acid-base neutralization reaction between magnesium hydroxide and 10-hydroxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-OH) at 120 C. A new synergistic intumescent flame retardant (IFR) for epoxy resin (EP), which was composed of DPM-H and ammonium polyphosphate (APP) was thoroughly studied. When the IFR loading was 8%, with the DPM-H to APP weight ratio at 1:7, the prepared flame-retardant EP (EPDA-2) passed the vertical burning tests (UL-94) V-0 rating and obtained the limiting oxygen index (LOI) value of 29.3%. Microscale combustion calorimetry (MCC) results showed that the total heat release (THR) of EPDA-2 reduced by 32.1% compared with pure EP. Meanwhile, the addition of DPM-H can partially solve the problem of the decrease of the EP mechanical property caused by the addition of APP. Compared with the flame-retardant EP with the 8% loading of APP, the impact strength of EPDA-2 increased 152.3%.
The degree of the imidization reaction determines the properties of polyimide (PI) obtained by the thermal curing process. In this paper, amine-modified graphene (N-GO) was designed by integrating pyridine structure with graphene and acting as a catalyst to promote the imidization reaction of PI. Fouriertransform infrared spectroscopy (FTIR), scanning electron microscope (SEM) were then used to confirm the morphology and structure of N-GO. The catalytic effect of N-GO in imidization reaction was obtained by FTIR and subsequently characterized by differential scanning calorimetry (DSC) and water contact angle (WCA). Surprising results suggest that the agglomeration of N-GO can also contribute to solid-phase reactions in imidization reactions.Lastly, the results of mechanical property tests, thermogravimetric analysis (TGA), and FTIR demonstrated that the composite films showed excellent tensile strength (176.2 MPa) and thermal stability (513.0 C); at the same content, only 0.5% of N-GO addition reduced the imidization temperature by 20 C, exhibiting remarkable enhancement effects. This research is a valuable solution to the problem in performance caused by low-temperature curing agent residues in films, and it is expected to be used in the microelectronics field.
Ammonium polyphosphate (APP), piperazine pyrophosphate (PAPP), and melamine cyanurate (MCA) were used as raw materials to develop an intumescent flame retardant system (IFRS) for polypropylene (PP). The synergistic flame retardancy among APP, PAPP, and MCA was explored. The effect of the proportion of APP, PAPP, and MCA on the IFRS flame‐retardant performance was studied. For the range of samples tested, the IFRS with the proportion of PAPP, MCA, and APP at 4:1:7.5 showed the best flame retardancy. When the addition of PAPP/MCA/APP IFRS in PP was 20%, the prepared flame‐retardant PP composite (PP‐PMA‐3) passed UL‐94 V‐0 rating. Moreover, the PP‐PMA‐3 total heat release (THR) decreased by 46.4% compared with PP‐0. Meanwhile, PAPP/MCA/APP IFRS showed good smoke suppression performance because the total smoke production (TSP) of PP‐PMA‐3 decreased by 65.0% compared with PP‐0. In addition, the high flame retardancy and the flame‐retardant mechanism of the prepared IFRS was explained.
Organically modified montmorillonite (OMMT) and Ni2O3 were simultaneously introduced into flame‐retardant linear low‐density polyethylene/ethylene‐vinyl acetate/magnesium hydroxide (LEM) composites. Compared with the LEM composite, the thermal stability, and tensile properties of LEM/ remained basically unchanged when 5 wt% of OMMT/Ni2O3 was substituted for MH. The LOI value increased a little from 27.2 to 27.7%. The data from cone calorimeter test showed that the first and second peak heat release rate was reduced by 19% and 67%, respectively. The total heat release and total smoke production showed a significant reduction by 18% and 36% after incorporation of OMMT/Ni2O3, respectively. The mechanism study indicated that the combination of OMMT/Ni2O3 cooperates promote the carbonization of the polymer itself into carbon naotubes, which form a more cohesive char layer with magnesium hydroxide during combustion. This is the core factor responsible for the synergistic effect on reducing the heat release and smoke production in the LEM composite.
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