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27.08.2018 | Original Paper | Ausgabe 5/2019

Polymer Bulletin 5/2019

Antimicrobial itaconimido aromatic hydrazide derivatives for inhibition of the thermal degradation of rigid PVC

Zeitschrift:
Polymer Bulletin > Ausgabe 5/2019
Autor:
Nadia A. Mohamed

Abstract

A series of novel itaconimido aromatic hydrazide derivatives has been synthesized by a low-temperature solution condensation reaction of N-[4-(chlorocarbonyl)phenyl]itaconimide with an equimolar amount of benzhydrazide, salicylhydrazide, p-aminobenzhydrazide or p-aminosalicylhydrazide. The structure of the synthesized derivatives was elucidated on the basis of elemental analyses, FTIR, 1H-NMR, and mass spectroscopy. All the hydrazide derivatives were screened for antibacterial activity against Bacillis subtilis and Streptococcus pneumoniae as Gram-positive bacteria and against Escherichia coli as Gram-negative bacteria and for antifungal activity against Aspergillus fumigatus, Geotricum candidum and Syncephalastrum racemosum fungi by agar well diffusion method. They showed good antimicrobial activity as judged by their high inhibition zone diameter and low minimum inhibition concentration. They are more potent against Gram-positive bacteria than against Gram-negative bacteria. Some of the hydrazide derivatives displayed comparable or even better antibacterial and antifungal activities than the reference bactericides or fungicides. The hydrazide derivatives are characterized by high thermal stability and could be cyclodehydrated into the corresponding 1,3,4-oxadiazole derivatives in the temperature region of 240–285 °C by losing water from the hydrazide groups as illustrated by thermogravimetric analyses (TG) and differential scanning calorimetry (DSC) in nitrogen. This is not a true degradation, but rather a thermochemical transformation reaction of the hydrazide derivatives into their corresponding 1,3,4-oxadiazole derivatives. The hydrazide derivatives were investigated as thermal stabilizers for rigid PVC using thermogravimetric analysis technique, in nitrogen. They exhibited a higher stabilizing efficiency relative to dibasic lead carbonate (DBLC), cadmium–barium–zinc (Cd–Ba–Zn) stearate complex and di-n-octyltin bis (isooctylmercaptoacetate) (n-octyltin mercaptide, n-OTM) industrially thermal stabilizers as shown by their higher initial decomposition temperature and higher residual weight percent at particular temperatures. Their stabilizing efficiency is also illustrated by lower rates both of discoloration as well as degree of chain scission of the polymer during degradation. The stabilizing efficiency increased with the introduction of electron-donating substituent groups into these derivatives.

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