Green-stabilized PVDC copolymer films using Precocene I

Abstract

Precocene I; 7-methoxy-2, 2- dimethyl chromene extracted from the plant Ageratum conyzoides (Ifiora, 2019), was incorporated into extrudable vinylidene chloride – methyl acrylate copolymer by heating the copolymer under reflux in methanol solvent in a three necked Quick fit flask under dry nitrogen gas until the weighed copolymer dissolved in the solvent. The weighed precocene I was then added drop wise to the resulting copolymer solution with continuous stirring and heating under nitrogen atmosphere to exclude oxygen as well as moisture. The product recovered on cooling the solution and evaporating the solvent methanol was weighed and later subjected to thermogravimetric analysis to determine weight loss data. A comparison of the infra-red (Ir) spectrum of the product of incorporation with that of the copolymer without incorporation did not show any new prominent absorption bands in the product obtained after incorporation but cannot be conclusive evidence in the absence of scale expansion facilities which may have provided further evidence. Plots of thermogravic data against time were linear at each of the three temperatures of 170°C, 180°C, and 190°C both for initiation and for propagation processes, and lend support for the statement that dehydrochlorination of the vinylidene chloride – methyl acrylate copolymer followed first – order kinetics at these three experimental temperatures with the incorporation of precocene I as additive. Rate constants for initiation of degradation under experimental isothermal conditions were obtained as 1.16 x 10^-5 s^-1, 2.50 x 10^-5 s^-1, and 5.58 x 10^-5 s^-1 at the constant temperatures of 170°C, 180°C, and 190°C, respectively, while values for rate constants of propagation were 2.32 x 10^-5 s^-1, 4.41 x 10^-5 s^-1 and 7.60 x 10^-5 s^-1 for the respective constant temperatures. These values show a steady decrease in the rate of degradation under the conditions of the experiment when compared with known literature values without additives as well as with nitrogen bases. Thermodynamic quantities derived from plots of these experimental quantities are as follows: Enthalpy of activation, DH^#, 98 kJ mol^-1, Arrhenius parameter, DE_a, 133 kJ mol^-1, and Entropy of Activation, DS^#, -128 J mol^-1 K^-1, as against corresponding values without any additive, namely 116 kJ mol^-1, 125 kJ mol^-1, and –32 J mol^-1 K^-1. The relative lowering of the energy requirements in the presence of precocene I additive indicates a more stable arrangement with lower degradation spontaneity. A reversal of such spontaneity is clearly supported by the negative value of the Entropy of Activation, DS^#. Precocene I additive was extracted from the plant Ageratum conyzoides using CHCl₃ as extracting solvent. Separation from other co-components was effected using Gas chromatography (GC) and isolation was by trapping in liquid N₂. Identification was by Mass Spectrometry (MS) using the fragmentation pattern: molecular ion mass M⁺, m/z 190 (EIMS), base peak m/z 175 (EIMS), molecular formula C₁₂H₁₄O₂. These as well as IR spectrum subsequently obtained from the isolated compound were compared with those stored on the NIST database which also confirmed identification by supplying ¹H and ¹³C NMR spectral characteristics.