AS 4758.2:2022 – Lifejackets Part 2: Materials and components-Requirements and test methods
AS 4758.2:2022 – Lifejackets Part 2: Materials and components-Requirements and test methods.
(d) Following removal from the oven, specimens shalt be laid on a flat surface for (17.0 ± 0.1) hat (23 t 2) °C and (50 ± 5) % relative humidity.
(e) They shall then be exposed In a similar container to an even temperature of (-30 ± 1) °C for a period of (7.0 ± 0.1) h, then removed and laid on the flat surface for (17.0 ± 0.1) h at rooni temperature as before.
(f) The cycle of exposure to alternating high and low temperatures shall be repeated until the samples have been exposed to each temperature for 10 periods. The measurements shall then be repeated, and the percentage volume change calculated.
(g) Examine the sample for cracking, dissolution and change of mechanical properties.
8.2.4 Compressibility of inherently buoyant material The test shall be as follows:
(a) Examine three specimens of each sample of foam of dimensions (100 ± 2) mm by (100±2) mm and of a thickness of at least 20 mm. If the material consists of granules. then fill three cloth sacks with the granules to the same filling density as the lifejacket or buoyancy aid. Fit them into a metal frame of dimensions 100 mm x 100 mm and a height equivalent to the thickness of the inherently buoyant material. Prior to the test, they shall have been stored at (23 ± 2) C and a relative humidity of(50 ±5) % for at least 24 Ii, In which conditions they shall be tested.
(b) Each specimen shall be placed in fresh water under a flat metal plate at least 20 % larger than the specimen size and then compressed at a speed of 200 mm/mm until a load of 50 kPa has been reached. This lower position shall be set for further compressions. The specimen shall then be completely decompressed, and the cycle of compression repeated a further four times, using the lower set point as the limit of compression.
(c) The specimen shall then be kept under the metal plate such that it is only just weighted by the plate to remain under water. The load required to achieve this shall be recorded as the original buoyancy.
NOTE It may bc ncccssary to usc a dilfcrcnt load ccli from that rcquircd by (b).
(d) The specimen shall then be dried for 7 days In air at a temperature of (23 ± 2) °C and a relative humidity of (50 ± 5) %. The compression cycle at (b) shall then be repeated without water, and for a total of 500 times. If deformation occurs, then the upper set point may need to he reset In order to keep the decompression time equal during the whole period.
(e The specimen shall then be returned to the atmosphere at (d) for at least 3 days. and the buoyancy measurement at (b) and (c) repeated, giving the value B. The loss of buoyancy (as A — B) shall then be expressed as a percentage of the original buoyancy (A).
8.2.5 Tensile strength
Foam buoyancy material that forms a structural part of a lifejacket (not retained by a cover fabric) shall be tensile tested in accordance with ISO 1926.
Prior to the tensile strength test, the dumbbell-shaped specimens shall be conditioned under standard conditions.
Dumbbell-shaped specimens shall be cut from the samples using Die A as specified in the standard test methods for rubber properties in tension specified in ISO 1926. Specimens from five of the samples shall be cut parallel to each other, and specimens from the other five samples shall be cut parallel to each other and in the direction perpendicular to that in which the specimens from the first live samples were cut. The top and bottom surfaces of the specimens shall be parallel, and the cut surfaces are to be perpendicular to the top surface and free from sharp or ragged edges. If skin is not a condition of acceptance, any surface skin or irregularities that affect the test results shall be removed by light.