INFLUENCE OF PLASTICIZERS ON THE PROPERTIES OF THIOKOL MASTIC

The influence of plasticizers - chloroparaffin and dibutyl phthalate - on the properties of thiokol mastic of SG-1M grade was investigated. Plasticizers were introduced into the sealing composition in amounts of 7, 9, 11, 13, 15 % wt. %. It was revealed that the type and amount of plasticizer influences the density value of sealing pastes. Thus, with the increase in the amount of the introduced plasticizer there is a noticeable decrease in the density of sealing pastes.The study of the influence of plasticizers on the viability of sealants showed that this index increases with the amount of chloroparaffin / dibutyl phthalate content. Increase in viability of sealing mastic with chlorparaffin increased by 60%, and for the composition with dibutyl phthalate almost twice. The viability of sealant with plasticizer dibutyl phthalate increases on average by 19 % in comparison with a similar sealant with chlorparaffin. According to the results of the study of strength parameters of sealants the tendency of decrease of conditional breaking strength with simultaneous increase of relative elongation was revealed, which indicates the increase of plastic properties of sealing mastics. Relative elongation increased in comparison with the initial sample for the composition with chloroparaffin by 87 %, and for the mastic with dibutyl phthalate by 2.5 times. At the same time, it was found that when the content of dibutyl phthalate in the amount of 15 wt. %, the relative elongation reached 100 %. This value is about 30 % more in comparison with relative elongation of sealant with chlorparaffin, that speaks about higher elastic properties of sealant with dibutyl phthalate. It is revealed that the addition of plasticizers significantly increases the hydrolytic resistance of sealing mastics based on thiokol. It is noted that the decrease in the degree of swelling is observed maximally at the introduction of 15 wt% of plasticizer and reaches 70% compared to the original sample. The minimum degree of swelling in water reaches for the composition with chloroparaffin 0,6 % wt. %, and for sealants with dibutyl phthalate 0,5 % wt. %. These indicators are within the normalized range (not more than 2 % wt. %) and indicate good resistance to moisture.