Synthesis And Characterization Of Poly(P-Phenylene Isophthalamide)

Fully aromatic polyamides(aromatic polyamides)are considered as high-performance organic materials due to their excellent thermo-mechanical resistance,and have gained important applications in aerospace.Aromatic polyamide fibers have a similar molecular structure because they have a similar molecular structure,and their main chains are composed of alternating aromatic rings and amide groups.Among them,two important types of wholly aromatic polyamides,poly(p-phenylene terephthalamide)(PPTA)and poly(meta-phenylene isophthalamide)(PMIA)have been industrialized.In this dissertation,a new variety of aromatic polyamides,poly(p-phenylene isophthalamide)(PPIA),has been studied.This polymer has not been industrialized.Reports of PPIA at home and abroad are rare.This thesis deeply discusses the synthesis of PPIA,and gives a detailed report on its synthesis method,synthesis process and its performance.The main research content of this paper includes the following two parts.In the first part(Chapter 2 of this thesis),poly(p-phenylene isophthalamide)was synthesized by the low temperature solution polycondensation method using p-phenylenediamine and isophthaloyl dichloride as monomers.The effect of reaction conditions(including solvent system,acid type,reaction time,monomer molar ratio,and reaction temperature)on the inherent viscosity of poly(p-phenylene terephthalamide)was investigated,and passed through infraredspectroscopy,Thermogravimetric analysis characterized and analyzed the chemical structure and thermal properties of the polymer.Experiments show that the polymerization temperature,monomer molar ratio and solvent system have a significant effect on the inherent viscosity of the polymer.The type of acid-binding agent has a greater influence on the inherent viscosity of PPIA,and the polymerization time should be prolonged.When calcium hydride is selected and the amount is 1/8 to 1/4 of the mass of p-phenylenediamine,the reaction temperature is-3°C and the monomer molar ratio is p-phenylenediamine(PPD):isophthaloyl chloride(IPC)=1:1.0071,the molar concentration of p-phenylenediamine was 0.45 mol/L,and the inorganic salt calcium chloride concentration(wt)was 5%.When the polymerization time was greater than 6h,the obtained polymer had a value of 0.99.The infrared spectrum shows that the polymer satisfies the basic structure of poly(p-phenylene isophthalamide).The results of thermogravimetric analysis show that when the temperature reaches around 580°C,the polymer's hot residual weight is 52%,indicating that the polymer PPIA has good thermal stability.In the second part(Chapter 3 of this paper),in order to further increase the inherent viscosity of PPIA,firstly,trimethylchlorosilane and p-phenylenediamine were used to synthesize N,N'-(bis)trimethylsilane and benzene.Then N,N'-(bis)trimethylsilane p-phenylenediamine and isophthaloyl chloride as monomers,using an ionic liquid instead of inorganic salts or organic solvents,using low-temperature solution polycondensation synthesis of poly(p-phenylene isophthalamide)Formyl p-phenylenediamine.The effects of the initial temperature of the polymerization,the polymerization time,and the solvent system on the inherent viscosity of PPIA were studied.The solubility test wasperformed on the synthesized PPIA.The chemical structure and thermal properties of the polymer were characterized and analyzed by infrared spectroscopy and thermogravimetric analysis.The chemical stability of PPIA was tested in a dilute acid and dilute alkaline environment.The synthetic experimental results show that the use of N,N'-(bis)trimethylsilane p-phenylenediamine instead of p-phenylenediamine can increase the polymerization rate,and the polymerization time can be shortened by half;when the monomer molarity is 0.35mol/L,the polymerization initiation temperature is 10°C,the solvent system is NMP-Ca Cl2,the inherent viscosity of the prepared PPIA has a maximum value of 1.35;take N,N'-(bis)trimethylsilane p-phenylenediamine The poly(p-phenylene isophthalamide)synthesized by p-phenylenediamine is higher in inherent viscosity than that of poly(p-phenylene isophthalamide).At the same time,the method uses trimethylchlorosilane and p-phenylenediamine in the benzene solvent while adding an acid absorbent to remove the generated hydrogen chloride,followed by simple distillation and drying to obtain N,N'-(bis)trimethylsilane-to-benzene Diamines,this method is simple,practical and does not require complicated equipment.The infrared spectrum shows that the polymer satisfies the basic structure of poly(p-phenylene isophthalamide).Thermogravimetric analysis shows that when the temperature reaches 586°C,the residual weight rate is 52%.Therefore,the polymer has good thermal stability,and thus the poly(p-phenylene isophthalamide)is expected to become a high temperature resistant fiber.The chemical stability test showed that PPIA was resistant to certain acidity and alkalinity.The solubility test showed that the polymer was insoluble in pure polar solvents and had good solubility in solvent-inorganic salt solutions.