ASTM D543 Plastics Resistance To Chemical Reagents

Scope:

ASTM D543 describes three practices, including a provision for reporting changes in size, shape, color, strength, and other mechanical characteristics. Using different chemical reagents relevant to a particular chemical resistance requirement is not prohibited when standard reagents are specified to establish results on an equivalent basis.

Test Procedure:

There are three practices included in this ASTM D543 standard:

Procedure I for Practice A’s Immersion Test: Weight Dimension, Appearance, and Color Changes

In this practice, we weigh each conditioned specimen separately to the nearest 0.025mm and take measurements of its thickness at the center, length, and width (or two diameters at right angles to each other). Laminates are prone to swelling under specific conditions, so we measure the thickness at the center and edges, reporting the percentage change separately for each location. Additionally, we consider measuring the color coordinates in CIE1976 Lab* units to analyze color changes.

Practice A – Immersion Test Procedure II – Mechanical Properties Changes:

For this practice, we submerge and handle the mechanical test specimens following the guidelines from Procedure I. We assess the mechanical properties of identical specimens, both submerged and non-submerged, based on the tensile test specifications provided for the tested material. Submerged specimens are tested immediately after removal from the chemical reagent. If the specimens were exposed to reagents at elevated temperatures, we cool them for about an hour in a separate container with the reagent at regular laboratory temperature before testing, unless specified otherwise.

Practice B: Exposure to Mechanical Stress and Reagents (including Environmental Stress Cracking Resistance, or ESCR):

In this practice, we mount test specimens onto strain fixtures with appropriate curvature to achieve the desired strain. Ensuring full contact between specimens and fixtures, we subject the strained specimens to the evaluated reagent, either through immersion or wet patch method for volatile reagents. The exposure times are seven days at room temperature and three days at elevated temperatures unless agreed otherwise. We maintain unexposed control specimens with identical strain conditions. After the exposure period, we determine the appearance and mechanical properties of both exposed and unexposed specimens using standard methods. We also record observations of cracks and crazes. Mechanical tests are conducted within 24 hours after removing specimens from the chemical agent and strain fixtures unless specified otherwise.

Video: Chemical Resistance of Plastics

 Test Specimen:

The specimen’s surface area significantly impacts the weight change caused by immersion in chemical reagents. Both the percentage change in mechanical characteristics and the percentage dimension change are influenced by thickness.

Additionally, findings from specimens cut from extruded sheets or molded pieces may not line up with findings from specimens made from molded specimens of a certain material. As a result, when comparing materials, findings from specimens with the same dimensions and prepared using similar techniques should be used.

Data:

Figure 1:Determination of Strain Level of Environmental Stress Crack Resistance (ESCR) Fixtures (Practice B)

Where,
R = radius of jig RNA

ROF = radius of outer fiber

t = thickness of the specimen

RNA = radius of the neutral axis

Ɵ = arbitrary angle

L_OF= length of outer fiber

L_NA = length of the neutral axis

 LNA=RNA=R+12t                                  RNA=R+12t  

LOF=ROF=R+t                                       ROF=R+t  

 L=LOF–LNA=R+t–R+12t 

= LL= R+t–R+12t R+12t

=R+t -R + 12t R + 12t = 12tR+12t           

= 12Rt+ 1       R= 1-1t2

Conclusion:

Hence, As described in this ASTM D543 standard practices, We can use this practice for the evaluating resistance of plastics to chemical reagents.