Transparent low-flammability epoxy resins using a benzoguanamine-based DOPO derivative

We successfully prepared a highly effective flame-retardant additive called hsalbenzoguanamine phosphaphenanthrene (HDPD) through salicylaldehyde and nitrogen-rich benzoguanamine. The introduction of HDPD into epoxy resin (EP) sharply enhanced the flame retardancy of EP/HDPD thermosets. The introduction of 6 wt% HDPD into EP succeeded in reaching the V-0 rating. Limited oxygen index results revealed the high flame-retarding performance of HDPD. Cone calorimeter test data revealed that heat and smoke released from EP/6 wt% HDPD thermoset were significantly restrained. In addition, EP/6 wt% HDPD thermoset demonstrated excellent transmittance and mechanical strength. The transmittance of EP/6 wt% HDPD was assessed from 520 to 800 nm. The results showed that transmittance of EP/6 wt% HDPD were nearly 90% of the control group.

Polylactic acid flame-retarded by nano-compound of form II ammonium polyphosphate with montmorillonite

It is reported a convenient method to obtain flame-retardant polylactic acid composite by adding low amount of crystal form II ammonium polyphosphate (APP-II) or nano-compound of crystal form II ammonium polyphosphate with calcium-based montmorillonite. The structures and thermal properties of the crystal form II ammonium polyphosphate and crystal form II ammonium polyphosphate with calcium-based montmorillonite were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Crystallography and morphologies of the polylactic acid and its composites with the crystal form II ammonium polyphosphate and crystal form II ammonium polyphosphate with calcium-based montmorillonite were measured through differential scanning calorimeter and scanning electron microscopy. In flame retardancy of the polylactic acid composites, the 5 wt% crystal form II ammonium polyphosphate could make the polylactic acid achieve the UL-94 vertical burning V-0 rating and limited oxygen index 27.3%. When using crystal form II ammonium polyphosphate with calcium-based montmorillonite in flame-retarding polylactic acid, only 3 wt% nano-compound can result in the same V-0 rating level and the limited oxygen index of 28.0%. Meanwhile, polylactic acid with crystal form II ammonium polyphosphate or crystal form II ammonium polyphosphate with calcium-based montmorillonite still keeps the good mechanical properties. The developed systems are environmentally friendly and highly effective flame retarding, which show a promising future in practical large-scale polylactic acid application.

Synthesis of a Flame Retardant for Epoxy Resins: Thermal Stability, Flame Retardancy, and Flame-Retardant Modes

A polyphosphonate (PDPA) flame retardant that contains phenyl phosphonic dichloride and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide groups, has been synthesized. The flame retardant was introduced into epoxy resins (EP) and cured by 4,4’-diamino diphenylmethane. The vertical burning, limited-oxygen index and cone calorimeter tests reveal that the PDPA can enhance the flame-retardant properties of the EP significantly. With only a 4 wt% PDPA loading, the EP composites achieved a limited-oxygen index value of 33.4% and a V-0 rating in the vertical burning test, and the peak heat release rate and total heat release were decreased by 40.9% and 24.6%, respectively. The thermal properties and gas pyrolysis products of the EP composites were evaluated by thermogravimetric analysis and thermogravimetric analysis-Fourier transform infrared spectroscopy, and the morphology and structure of residual char were characterized by scanning electron microscopy, Flourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. To explain the combined effects of the condensed and gas phases, modes of the flame-retardant action are proposed.

Flame retardancy and thermal properties of rigid polyurethane foam conjugated with a phosphorus–nitrogen halogen-free intumescent flame retardant

In this work, a halogen-free intumescent combining phosphorus and nitrogen, flame-retardant 2-((2-hydroxyphenyl)(phenylamino)methyl5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide (HAPO) was successfully synthesized. It had been synthesized by reaction of 5,5-dimethyl-1,3, 2-dioxphosphinane 2-oxide with Schiff base. Its chemical structure was characterized in detail by Fourier transform infrared spectroscopy, 1H NMR, and 31P NMR spectrum. The flame-retardant polyurethanes were prepared with different loadings of HAPO. The thermal properties, flame retardancy and combustion behavior of the pure polyurethane foam thermosets were investigated by a series of measurements involving thermogravimetric analysis, limited oxygen index measurement, UL-94 vertical burning test, and cone calorimeter test. The results of the aforementioned tests indicated that HAPO can significantly improve the flame retardancy as well as smoke inhibition performance of polyurethane foam. Compared with the PU-Neat, the limited oxygen index of flame-retardant polyurethanes (15%) thermoset was increased from 19.5% to 23.8% and its UL-94 reached V-0 rating. In addition, the cone test results showed that the heat release rate, total heat release, rate of smoke release, and total smoke production of flame-retardant polyurethanes (10%) were decreased obvious sly. The apparent morphology of carbon residue was characterized by scanning electron microscopy, and results revealed that the modified polyurethane foam can form dense carbon layer after combustion. Thermogravimetric analysis results also indicated that the char amount of flame-retardant polyurethanes was obviously increased compared with PU-Neat. Based on the above analysis, we can draw the conclusions which in the condensed phase, phosphorus-based acids from the degradation of HAPO, this could promote the formation of continuous and dense phosphorus-rich carbon layer. In the gas phase, the flame-retardant mechanism was ascribed to the quenching effect of phosphorus-based radicals and diluting effect by non-flammable gases.

Influence of reactive POSS and DDP on thermal stability and flame retardance of UPR nanocomposites

Unsaturated polyester resins (UPR) were prepared by the melt condensation method based on adipic acid, o-phthalic anhydride, maleic anhydride and ethylene glycol in the presence of PSS-(2,3-propanediol)propoxy-heptaisobutyl substituted (PSS-POSS) or/and 9 wt% [(6-oxide-6H-dibenz(c,e)(1,2)oxaphosphorin-6-yl)methyl]butanedioic (DDP). We synthesized UPR containing DDP (DDP-UPR) and UPR containing both DDP and PSS-POSS (DDP-PSS-POSS-UPR series). The chemical structures of the modified polyesters were characterized and confirmed by Fourier transform infrared (FTIR) and 31P nuclear magnetic resonance (31P NMR). The thermal stability and flammability behaviors of UPR were evaluated by thermogravimetric analysis (TGA) and limited oxygen index (LOI) and the vertical burning test. The morphology of residual char of UPR was shown by scanning electron microscopy (SEM). The results indicate that the incorporation of PSS-POSS has little influence on the thermal stability of DDP-UPR, but enhances the flame retardance of DDP-UPR, and when the PSS-POSS content reaches 10 wt%, the DDP-PSS-POSS-UPR has better flame retardance.

Preparation of microcellular poly(lactic acid) composites foams with improved flame retardancy

In this study, flame-retardant poly(lactic acid) foams with satisfactory cell structures were prepared by microcellular foaming technology using phosphorus-containing flame retardant and graphene as the charring agent. The introduction of 5–30 wt% flame retardant increased the limited oxygen index value of poly(lactic acid) from 19.0 to 26.5–37.8% and simultaneously increased the foam expansion of poly(lactic acid) foams from 4.4 to 5.8–17.5. In addition, all the prepared poly(lactic acid)/flame-retardant composites passed the UL-94 V-0 rating. The addition of 0.5 wt% graphene increased the limited oxygen index value of poly(lactic acid)/flame-retardant composite with flame-retardant content of 15 wt% from 27.9 to 29.2%, and more graphene additions improved the antidripping behavior of poly(lactic acid) composites. The possible mechanisms of the effects of the resultant cellular structure on the flame-retardant properties of poly(lactic acid) composites were also discussed.

Flame-Retardant Properties of Polyester Fabrics Reinforced Phenolic Resin Modified with Silazanes Composites

Phenolic resin modified with methylvinylcyclosilazanes (MVSZ) were prepared and their flame-retardant properties were investigated, and results exhibited that the Limited Oxygen Index (LOI) values increased with the content increasing of MVSZ, and the LOI reach to 40.8, when the content of MVSZ was 26.0%. The flame-retardant and mechanical properties of polyester fabrics reinforced phenolic resin modified with silazanes (PFMS) composites were measured, the results indicated that the LOI and flexural strength were enhanced compared with those of phenolic resins composites.

Processing of Fireproof and High Temperature Durable Particleboard from Rice Husk

The aim of this study is the recovery of rice husk waste by researching usability in industry as an alternative to wood. In this study urea formaldehyde resin was used mainly as binding agent for wood-panel used in industry. For the preparation of composite material, ground powder rice husks were mixed with urea formaldehyde resin used in different proportions (65/50, 75/50, 80/50, 85/50, 95/50 by mass of filler/binder). Each particleboard produced in 393.15 K and 9.8 MPa pressure was tested by means of three point bending strength, shore hardness and limited oxygen index (LOI) tests. Particleboard made with 75/50 paddy husk/urea formaldehyde composition material formed of 11.40 MPa specimens showed the highest strength. Limited oxygen index value increased by increasing the filler material usage. The highest LOI value was recorded as 40%. Besides, fire point of particleboards which have the best three point bending strength has been analyzed at environmental atmosphere and 493.15 K has been measured as fire point. The results of the tests showed that this material maybe used instead of wooden plate. The usage of agricultural wastes like these in processing of particleboard will give economically benefits and slow down waste products.

Flame Retardant Properties of Two Different Synthetic Process of Ammonium Polyphosphates

Ammonium polyphosphate (APP) produced by non-P2O5 process and traditional P2O5 process were used in the intumescent flame retardant (IFR) polypropylene (PP) composite (IFR-PP). The composite was tested by limited oxygen index (LOI) and UL-94. TGA and SEM were used to study the decomposition processes. Results showed that when the ratio of APP-II/ pentaerythritol/melamine is 3/1/1, the LOI value is 33.1, and all composite could reach UL-94 V0 rating. The results showed that APP by non-P2O5 process had similar IFR properties as APP of traditional P2O5 process