Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
The term 'specific' gravity refers to a material's density compared to that of a reference material. In the case of this
test method, it usually refers to a material's density compared to that of water.
Possible reasons why customer may request Specific Gravity Testing include:
- Comparison of Materials Pre- and Post-Exposure or Treatment
- Measuring Porosity of a Polymer Material
Below you will find a brief description of the ASTM Test Method related to the topics covered above:
Significance and Use
The specific gravity or density of a solid is a property that is conveniently measured to identify a material, to follow physical changes in a sample, to indicate degree of uniformity among different sampling units or specimens, or to indicate the average density of a large item.
Changes in density of a single material are due to localized differences in crystallinity, loss of plasticizer, absorption of solvent, or to other causes. It is possible that portions of a sample differ in density because of their differences in crystallinity, thermal history, porosity, and composition (types or proportions of resin, plasticizer, pigment, or filler).
Density is useful for calculating strength-weight and cost-weight ratios.
1.1 These test methods describe the determination of the specific gravity (relative density) and density of solid plastics in forms such as sheets, rods, tubes, or molded items.
1.2 Two test methods are described:
1.2.1 Test Method A—For testing solid plastics in water, and
1.2.2 Test Method B—For testing solid plastics in liquids other than water.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 1—This standard is not equivalent to ISO 1183–1 Method A. This test method provides more guidelines on sample weight and dimension. ISO 1183-1 allows testing at an additional temperature of 27 ± 2°C.
2. Referenced Documents
- D4968 Guide for Annual Review of Test Methods and Specifications for Plastics
- D618 Practice for Conditioning Plastics for Testing
- D6436 Guide for Reporting Properties for Plastics and Thermoplastic Elastomers
- D891 Test Methods for Specific Gravity, Apparent, of Liquid Industrial Chemicals
- E1 Specification for ASTM Liquid-in-Glass Thermometers
- E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
density; relative density; specific gravity; Density--plastics; Displacement--plastics; Specific gravity--plastics; ICS Number Code 83.080.01 (Plastics in general)
( Download ASTM D792 From www.ASTM.org )