Specification for one part gun-grade polysulphide-based joint sealants, Part 2: Methods of test
1986 Edition

IS 11433 Part 2 outlines specific substrates for adhesion evaluations including: clean plate glass of approximately 6 mm thickness; stainless steel conforming to IS 6911-1972; untreated aluminium alloy 64430 WP as per IS 736-1974; and Portland cement mortar blocks prepared and cured under defined conditions (mix ratio of 1 part ordinary Portland cement to 3 parts standard sand with a water-cement ratio of 0.35 to 0.40, cured initially for 24 hours at controlled humidity, followed by 28 days water curing, drying at 110°C for 12 hours, and storage at 25±2°C and 65% relative humidity for 28 days). Representative test assemblies include combinations such as glass with aluminium and stainless steel with cement mortar, ensuring standardized and reproducible adhesion test setups.

The cyclic adhesion test per IS 11433 Part 2 involves using a dedicated test apparatus (Fig. 2) with the test chamber maintained at -15 ± 2°C. Initially, assemblies containing spacers are oven-conditioned at 70 ± 2°C for 4 days. After cooling for at least 2 hours under laboratory conditions and spacer removal, specimens are immersed in distilled or de-ionized water at 25 ± 2°C for 24 hours. Subsequently, dried assemblies are placed in the test device and conditioned at -15 ± 2°C for a minimum of 16 hours. Extension is then applied incrementally at 1.0 ± 0.1 mm every 3 minutes until reaching a total of 24 mm, maintaining this extension at -15 ± 2°C for 24 hours. The specimens are then relaxed at 25 ± 2°C for 4 hours without tensile stress, compressed at 5-6 mm/min until a 12 mm compression is achieved, and oven-conditioned again at 70 ± 2°C for 4 days. This immersion, freezing, extension, and conditioning cycle is repeated as specified to evaluate sealant performance under cyclic environmental stresses.

The staining evaluation procedure involves preparing a mortar block with a central cavity, half of whose upper surface and inner hole surfaces are coated with primer if specified. The cavity is filled completely with the polysulphide sealant, and the remaining sealant is evenly spread over the block’s top surface to a thickness between 6 and 10 mm. The specimen is conditioned for 24 hours at 25 ± 2°C and 50 ± 5% relative humidity. Following this, the specimen undergoes repeated immersion cycles, each consisting of immersion for 1 minute in 400 ml distilled water at room temperature, followed by conditioning in the chamber. This cycle is repeated 13 times over 21 days, ensuring at least 24 hours between immersions. Staining is inspected primarily on the smooth, uncoated undersurface around the sealant interface. The presence or absence of staining, as well as whether it occurs on primed or unprimed surfaces, is recorded to assess the sealant’s staining propensity.

According to IS 11433 Part 2, cement mortar blocks are prepared by thoroughly mixing dry ordinary Portland cement (1 part) with standard sand (3 parts) on a non-absorbent, non-metallic surface before adding water to achieve a water-cement ratio between 0.35 and 0.40. The sand used must be washed and dried, with grain size distribution such that 100% passes through an 850 µm sieve and 0-10% passes through a 600 µm sieve. The mortar is cast into rigid molds of 12 mm thickness and 76 mm diameter with a central hole created by a polyethylene mandrel. The casting is done in four layers, each compacted on a vibrating table. The blocks are initially cured within molds for 24 hours at relative humidity ≥ 90%, then demolded and immersed in water (~400 ml per block) at ambient temperature for 28 days. After water curing, blocks are dried at 110°C for at least 12 hours and stored for another 28 days at 25 ± 2°C and 65% relative humidity. If blocks are stored in uncontrolled conditions, they must be reconditioned for 7 days at the specified temperature and humidity before utilization.

IS 11433 Part 2 prescribes that during heat aging, assemblies should be cured at 40 ± 2°C and 95 ± 5% relative humidity for 21 days with specimens securely clamped and spacers repositioned after 7 days to maintain a 6 mm gap on each side. Mass loss tests involve curing the specimens for 21 days under the same conditions, followed by an additional 14 days aging at 70 ± 2°C. Prior to weighing, the specimens are conditioned for 2 hours at 25 ± 2°C and relative humidity not exceeding 55%. Mass loss percentage is calculated by comparing initial and final masses of the sealant. Additionally, sealants are conditioned at 25 ± 2°C and 50 ± 5% relative humidity for 24 hours before tensile testing. For adhesion tests involving sunlamp exposure, the glass surface temperature must not exceed 50°C, and specimens are exposed for 96 hours at a distance of 300 mm from the lamp source. These controlled environmental conditions ensure consistent and reproducible evaluation of sealant durability.