Design And Combustion Mechanism Study Of New Flame Fetardant Bio-based And Semi-Aromatic Polyamide Composite

It's an important strategy oriented towards the national energy strategy to use new energy material displace fossil fuels.By summarizing the documents and researching the theory of high temperature resistant polyamides,the thesis designed and developed petroleum base polyamide,such as alternative PA6T,PA9T.Low-melting-point,easily decomposed during processing and poor flame retardancy greatly limit its application in the sophisticated field.Therefore,the development of flame-retardant bio-based high temperature resistant polyamide with good processability has become an important target.Structural design,manufacturing technology and flame-retardant modification of novel bio-based polyamides could help to develop polyamides with high-temperature stability,excellent apparent hardness and anti-tracking performance.The research contents of this work are as follows:(1)The structure of bio-based polyamides was adjusted to improve its processing stability are improved.Based on PA10T homopolymer,a series of high temperature resistant polyamides with the same content of biological group and different melting point were synthesized,where a part of terephthalic acid is replaced with isophthalic acid monomer.The branched structure was introduced into the straight chain of 10T molecule by isophthalic acid,which reduced the crystallinity and melting point of the new high temperature resistant polyamide.Then,the molecular structure of the sample was confirmed by13C-NMR,1H-NMR and IR.And the properties of the product were characterized by DSC and TGA.Finally,the high temperature resistant polyarylamine(PA10T/10I)with the content of biological group more than 50%and the melting point more than 280? was obtained by screening all samples.(2)In order to realize industrialization of bio-based high temperature resistant nylon resin,suspension prepolymerization and vacuum drum solid phase tackifier were used to prepare bio based high temperature resistant nylon resin.The screw belt agitator is used to solve the mixing problem of the reaction system and obtain uniform and stable prepolymer;the multi reactor and segmented low-temperature polymerization technology are used to solve the problems of discoloration and yellowing caused by high-temperature melting of high-temperature resistant nylon,so as to obtain high brightness and high whiteness resin that can meet the needs of LED support;the modified paddle dryer material receiving device is used to make the material cooled,crushed and transported rapidly,thus solving the problem of material caking after prepolymerization discharge;the waste water recycling equipment is established to realize the recycling of reaction waste water,reduce the waste water discharge and prevent the pollution of the environment;the vacuum pipe heat tracing and insulation system is adopted to prevent the excessive diamine monomer from solidifying on the inner wall of the vacuum pipe and blocking the vacuum pipe,Furthermore,the diamine is cooled,solidified and recycled in the cyclone separator,which improves the production efficiency and reduces the production cost.(3)Aiming to improve the flame retardancy and mechanical performance,high temperature resistant polyamide was modified with halogen-free(Alpi)and halogen-free(BrPS/ZB=3:1)flame retardancy.The effect of different additives on the flame retardant polyamide was studied.The performance of the modified material was evaluated by TGA,oxygen index combustor and cone calorimeter.Then The V-0 grade composite material in accordance with UL-94 combustion test was obtained.Finally,the suitable formula was selected and compared with the same type of commercial products.The data show that the high temperature resistant polyamide products have the advantages of low water absorption,good dimensional stability,good fluidity,no blistering after reflow soldering,good color stability and good recyclability.(4)To explore the fire behavior in combustion and the fire-retardant mechanism of bio-based high temperature resistant nylon resin,the graphitization degree of char residue was analyzed by Raman spectrum and X-ray diffraction(XRD);the composition of char residue was analyzed by X-ray photoelectron spectroscopy(XPS);the microstructure of char residue was analyzed by SEM.The coalescence mechanism of flame-retardant modified bio based flame-retardant and high temperature resistant nylon composite with brominated flame retardant system and hypophosphonate flame retardant system during combustion was explored.Steady state tubular furnace platform(SSTF)and Thermogravimetric analysis-infrared spectrometry(TG-IR)were apllied to analyze the change of gas products during combustion and to reveal the corresponding flame-retardant mechanism.The synergistic effect flame-resistance mechanism of free radical chain mechanism in gas phase and char-forming in condensed phase was also illustrated.(5)In order to further improve the properties of flame retardancy of bio-based high temperature resistant polyamide resin,BP-CO-POSS nanohybrids was synthesized through the reaction of-COOH functional group with-NH3Cl functional group on eight branch chains of POSS-NH2.PA/Alpi/BP-CO-POSS composite was prepared by replacing part of Alpi with BP-CO-POSS.Then the pyrolysis and combustion behavior of the composite system were studied,which revealed that the new two-dimensional material,black phosphorus,exhibited good synergistic effect with POSS and Alpi in flame-retardant and anti dripping performance.