Effect of Hard Segment Content and Molecular Weight of Liquid Polysulfide on the Microphase Separation Structure–Property of One‐Component Polysulfide Adhesives

Abstract

The degree of microphase separation plays a vital role in one‐component polysulfide adhesives determining their mechanical properties and thermal stability. However, the degree of microphase separation was mainly determined by the hard segment content and molecular weight of liquid polysulfide. In this work, we successfully prepared a series of one‐component polysulfide adhesives with 30 wt%–50 wt% hard segment content by using 4,4‐diphenylmethane diisocyanate (MDI), different molecular weights (1000, 2500, and 4000 g/mol) of liquid polysulfides (JLY‐121/1225/124) and 1,4‐butanedithiol (BSO), and systematically investigated the relationship between microphase separation and material's properties. The results revealed that higher hard segment content and larger molecular weight of liquid polysulfide contributed to forming a higher degree of microphase separation, respectively. Among them, the optimal mechanical properties and thermal stability were obtained at 40 wt% hard segment content when JLY‐1225 (2500 g/mol) was used. After immersion in the oil and water for 21 days, the tensile strength of C40‐1225 could still reach 16.99 ± 0.80 and 14.87 ± 0.30 MPa, with a tensile strength retention rate of 75.75% (oil) and 66.30% (water), confirming that one‐component polysulfide adhesives had good solvent resistance.