STUDY OF THE PLASTICIZING EFFECT OF DICARBOXYLIC ACIDS AND OXYETHYLATED ALCOHOLS

This paper presents the results of a theoretical evaluation of the plasticizing effect of the synthesized ester compounds based on the calculations of the Hansen solubility parameters (HSP), which is based on the concept that the total energy of liquid evaporation consists of three main components: dispersion forces between atoms (δd), dipole interactions between molecules (δp) and hydrogen bond interaction forces (δh), which are caused by electron exchange. The calculated data showed a slight discrepancy between the δd, δp and δh values of the studied ester plasticizers and the corresponding parameters of polyvinyl chloride (PVC), which indicates a high compatibility of these compounds with this polymer. Thus, the degree of molecular similarity determines the intensity of intermolecular interaction, since substances with close HSP values are characterized by high affinity. The accuracy of the performed calculations of the Hansen solubility parameters correlates with the experimental values of the critical dissolution temperature. It has been proven that the developed esters of dicarboxylic acids containing an aromatic ring dissolve polyvinyl chloride better than similar compounds of the aliphatic series. For comparison, the critical dissolution temperature of diphenoxyethyl adipate is 134 °C, and that of the corresponding butoxyethanol ester is 147 °C. Dynamic mechanical analysis (DMA) of the obtained products showed that all phenoxyethanol esters undergo transformation into a highly elastic state at temperatures above the glass transition temperature. It has been established that the physicomechanical properties of PVC compositions significantly depend on the molecular structure of the compounds under study. According to the obtained DMA data, esters of oxyethylated butanol are comparable in elastic modulus to industrial plasticizers DOP and DOA. Additionally, the effect of plasticizer content on the composition hardness according to Shore A was studied. It was found that the structure of ester molecules has a pronounced effect on this indicator. Thus, to achieve the reference hardness corresponding to the use of DOP (70 conventional units), the required amount of dibutoxy esters is 5.1% (DBES), 8.5% (DBEAz) and 18.6% (DBEG) less, whereas in the case of phenoxy esters, on the contrary, it is necessary to increase their share in the formulation from 9% to 22%. Consequently, dibutoxy esters of dicarboxylic acids demonstrate higher efficiency as plasticizers compared to aromatic analogues, although the latter have greater dissolving capacity.