A study of the curing of sealants used in building construction

Abstract

Important material properties such as strength, elasticity, movement capability and weather resistance are developed as a sealant cures. Indeed, the magnitude of key material properties such as modulus is directly related to the level of cure. Hence it is important to appreciate the level of cure of a sealed joint when it is being tested. A review of the curing of sealants is given with some generalized cure mechanisms proposed for polysulfide, polyurethane and silicone sealants. There is generally very little published work on assessing the cure of sealants. The deficiencies in traditional methods for measuring the level of cure in polymer systems (for example, hardness and rheometry tests) when applied to sealants are outlined. Two alternative methods were used to determine the state of cure of six sealant materials: the measurement of modulus and glass transition temperature ( T g ) with cure time. The effect of different curing regimes on cure development was monitored for up to 16 weeks' cure time. The results show that both modulus and T g are useful parameters for assessing the cure level of sealants, with T g measurement being particularly elegant. Six weeks' curing appeared to be the minimum cure time necessary to provide a sufficiently high degree of cure for material testing to be performed, regardless of curing regime of sealant type used.