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Study on synthesis of high molecular weight poly(p-phenylene terephthalamide) by combining calcium hydride

wallpapers News 2021-11-23
Study on synthesis of high molecular weight poly(p-phenylene terephthalamide) by combining calcium hydride
The study uses calcium hydride instead of pyridine as the acid absorbent to synthesize high molecular weight polyparaphenylene terephthalate (PPTA) and compares it with the polymer product using pyridine as the acid absorbent to evaluate the application prospects of this research. Calcium hydride replaces pyridine to investigate the influence of calcium hydride on the polymerization process of TPC and PPD and the molecular weight and structure of the polymer product. The results of the study show that the addition of calcium hydride can polymerize high molecular weight PPTA. Elemental analysis, X-ray diffraction, and infrared spectroscopy The analysis results show that PPTA synthesized using calcium hydride and pyridine as acid absorbents are the same in element content and structure. The thermogravimetric analysis results show that the thermal decomposition temperature of PPTA obtained using two acid absorbents is about 550 ℃. These research results preliminarily prove that it is feasible to use calcium hydride instead of pyridine for industrial polymerization of high molecular weight PPTA.
Fully aromatic polyamide (aramid) is considered to be a high-performance organic material due to its excellent thermal stability and mechanical strength, and it is used in aerospace and aviation. The energy of aramid fiber is that they have a similar molecular structure, the main chain is composed of aromatic rings and amide groups alternately connected. Among them are two important types of fully aromatic polyamides: polyparaphenylene terephthalate (PPTA) and polyisophthalamide Metaphenylene diamide (PMIA) has been industrialized. In this paper, a new species in the aromatic polyamide family-polyparaphenylene isophthalamide (PPIA), has not been realized. Industrialization, there are not many reports on PPIA at home and abroad. This paper discusses the synthesis of PPIA in-depth and gives a detailed report on its synthesis method, synthesis process, and performance. The key research content of this paper includes the following two parts: The first part (Chapter 2 of this paper), using p-phenylenediamine and isophthalic chloride as monomers, using low-temperature solution polycondensation method to synthesize polyp-phenylene isophthalamide. Each reaction is explored. The influence of conditions (solvent system, acid absorbent type, reaction time, monomer molar ratio, reaction temperature) on the inherent logarithmic viscosity of polyparaphenylene isophthalamide, and through infrared spectroscopy and thermogravimetric analysis The chemical structure and thermal properties of the polymer were characterized and analyzed.
The thermal stability of high-molecular-weight PPTA resin in concentrated sulfuric acid is related to temperature, solution concentration, and stirring speed during dissolution. As the temperature rises, its thermal stability decreases; when the solution concentration is lower than 16% (W/W), The lower the concentration, the worse the thermal stability, when the solution concentration reaches more than 16%, the concentration has no obvious effect on its thermal stability; the stirring speed increases during dissolution and its thermal stability becomes worse; PPTA resins of different molecular weights The thermal stability in sulfuric acid is basically the same.

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