ASTM-D4976:12a(R2020) pdf free download – Standard Specification for Polyethylene Plastics Molding and Extrusion Materials.
10. Specimen Preparation
10.1 Unless otherwise specified, test specimens shall be compression molded in accordance with Annex A 1, Procedure C of Practice D4703.
10.2 The specimen type and dimensions shall comply with those described in the test method section. Die-cut specimens are recommended: however, machine-cut specimens are acceptable.
11. Conditioning
11. 1 Conditioning—Once specimens are molded, they shall be moved to a standard laboratory atmosphere or a controlled laboratory atmosphere. For natural unfilled polyethylene plastics the controlled laboratory atmosphere shall be 23 ± 2°C. Test specimens, 7 mm or under in thickness, shall be conditioned for a minimum of 40 h immediately prior to testing. For filled and reinforced polyethylene plastics or polyethylene plastic blends, which contain a hydrophilic co-monomer, pigment. or modifier the specimens shall be conditioned in a standard laboratory atmosphere of 23 ± 2°C and 50 ± 10 % relative humidity (see Practice D618, Procedure A). For all materials to be conditioned for electrical testing. conditioning shall comply with the requirements of the standard test methods for electrical testing. In all cases the laboratory shall report both the temperature and humidity conditions during the conditioning period.
II .2 Test Conditions—Natural unfilled polyethylene plastics shall he tested in a controlled laboratory atmosphere of 23 ± 2°C. For filled and reinforced polyethylene plastics and polyethylene plastic blends, which contain a hydrophilic comonomer. pigment, or modifier the specimens shall he conditioned in a standard laboratory atmosphere of 23 ± 2°C and 50 ± 10 % relative humidity. For all materials to be tested for electrical properties. the laboratory shall comply with the requirements of the standard test methods for electrical testing. In all cases the laboratory shall report both the temperature and humidity conditions during testing.
11.3 Dispute—In cases of dispute. conditioning and testing shall be conducted in accordance with Procedure A of Practice D618.
12. Test Methods
12. 1 Determine the properties enumerated in this specilication in accordance with the ASTM methods as they apply, unless otherwise stated in this specification.
12.1.1 Flow Rate—Test Method Dl238, using Condition l90°C/2.l6 kg unless otherwise directed. (see Note 8). Make duplicate determinations on the material in the form of powder, granules. or pellets. No conditioning is required.
Nom 8—Although the flow rate of polyethylene plastics can be measured under any of the conditions listed for it under 6.2 of Test Method D1238, only measurements made at Condition 19OC/2.I6 kg are identified as “melt index.”
This method of test serves to indicate the degree of uniformity of the flow rate of the polymer of a single manufacturer as made by an individual process and is not, by itself, indicative of the degree of uniformity of other properties. Additionally, uniformity of flow rate among various polymers of various manufacturers as made by various processes does not, in the absence of other tests, indicate uniformity or equivalency of other properties and vice versa.
The melt viscosity of polyethylene plastics, in common with that of most high polymers. is non Newtonian, that is, dependent on the rate of shear. The degree of departure from Newtonian behavior depends on the nature and molecular constitution of the individual sample. Addiional characterization of the sample can be obtained if other conditions are used. Especially recommended as an adjunct to Condition 190°C/2.16 kg is Condition 190°C/lO.O kg or Condition l9O°2l.6 kg.