AS NZS 4766:2020 pdf free.Rotationally moulded buried, partially buried and non-buried storage tanks for water and chemicals.
2.7.3 All other tank types
When tested in accordance with ASTM D2565, the polymer compound for tanks, fusion-bonded fittings and welding rods shall contain UV stabilizers such that the natural (non-pigmented) compound will retain 50 % tensile elongation after 8 000 h of exposure in a Xenon-Arc weatherometer.
2.7.4 Alternative test methods
UV testing in accordance with ISO 4892-2 may be conducted as an alternative to ASTM D2565. When testing in accordance with Iso 4892-2, evidence shall be provided to demonstrate that the amount of exposure hours in accordance with ISO 4892-2 is equivalent (or higher) in total energy output to that specified in Clause 2.7.2 or Clause 2.7.3.
2.8 Dispersion of additives and pigments
2.8.1 General
Compounded powders for rotational moulding that exhibit a uniform colour distribution after the masterbatch has been compounded into the polymer will also exhibit uniform distribution of all other additives including UV light stabilizers that have been compounded into the masterbatch simultaneously with the pigments. The addition of UV light stabilizer additives only via masterbatch into a non-UV stabilized base resin shall not be permitted.
A sample for visual inspection of between 0.5 mm to 1 mm in thickness and a minimum of 40 mm diameter shall be rotational or compression moulded or melted down from production powder to provide a sample sufficiently large to allow inspection under a light source. Colour shall be even through the specimen, without any evidence of agglomeration, blotching or other visual evidence of uneven dispersion.
2.8.2 Non-UV stabilized base resins
Anti-oxidants, ultraviolet light stabilizers and pigments, including carbon black, shall be evenly dispersed in the compound for non-U V stabilized base resins. The compounded resin shall be tested for uniformity of dispersion of additive via visual inspection of a specimen manufactured in accordance with Clause 2.8.1.
Anti-oxidants, pigments and ultraviolet stabilizers shall be pre-compounded with a small percentage of a suitable polymer resin into a masterbatch, before this masterbatch is compounded with the (nonUV stabilized) base resin at the prescribed ratio/percentages to ensure the final compound conforms with Section 5 of this Standard. Pigment content, other than carbon black, shall not exceed 2 % of the total mass.AS NZS 4766 pdf download.