WEATHERING EFFECTS ON PLASTICS

A STUDY IS CONDUCTED TO ATTEMPT TO PREDICT A PLASTIC'S WEATHER-ABILITY. NUMEROUS APPEARANCE, PHYSICAL, AND FUNDAMENTAL PROPERTIES OF PLASTICS ARE BEING EXAMINED IN SIMULATED AND OUTDOOR EXPOSURES. THE CHANGES IN TENSILE AND FLEXURAL PROPERTIES RESULTING FROM EXPOSURE ARE BEING DETERMINED. MEASUREMENTS ARE CONDUCTED ON PLASTICS WHICH INCLUDE POLYETHYLENES, POLYMETHYL METHACRYLATES, POLYVINYL FLUORIDES, POLYETHYLENE TEREPHTHALATES, GLASS-REINFORCED POLYESTERS, AND POLYVINYL CHLORIDES. ALL PLASTICS WERE SUBJECTED TO MODIFIED ASTM TENSILE TESTS. THE FOLLOWING PARAMETERS WERE THEN OBTAINED FROM THE RESULTING STRESS-STRAIN CURVES: YOUNG'S MODULUS OF ELASTICITY, YIELD STRESS, YIELD STRAIN, FAILURE STRESS, AND ULTIMATE ELONGATION AT BREAK. FLEXURAL PARAMETERS MEASURED WERE: YOUNG'S MODULUS, YIELD STRESS, YIELD STRAIN, RUPTURE STRESS, RUPTURE STRAIN, AND STRESS AT 5 PERCENT STRAIN, IF THE MATERIAL DID NOT BREAK AT LESS THAN 5 PERCENT STRAIN. THE ULTIMATE TENSILE ELONGATION AND 5 PERCENT FLEXURAL STRESS SHOWED THE GREATEST CHANGE WITH TIME. ULTIMATE ELONGATION DECAYED RAPIDLY WITHIN ONE YEAR FOR MOST OF THE PLASTICS. FIVE PERCENT STRESS INCREASED SUBSTANTIALLY IN A FEW MONTHS AFTER WHICH THERE WAS LITTLE OR NO CHANGE. AN INCREASE IN 5 PERCENT STRESS WAS USUALLY ACCOMPANIED BY A DECREASE IN ULTIMATE ELONGATION. THESE CHANGES INDICATE A LOSS OF ELASTICITY AND FLEXIBILITY, RESULTING IN INCREASING STIFFNESS AND PROBABLY BRITTLENESS. USING ULTIMATE ELONGATION AND 5 PERCENT STRESS, PERCENT RETENTION OF INITIAL VALUE WAS FOUND TO BE A USEFUL MEASURE FOR CLASSIFYING THE PLASTICS. SMOOTH CURVES FITTED FOR THE PERCENT RETENTION OF INITIAL ULTIMATE ELONGATION SHOW A DEFINITE EXPONENTIAL DECREASE. MATHEMATICAL MODELS USING FUNCTIONS OF TIME AND WEATHER VARIABLES ARE BEING FITTED TO THE ULTIMATE ELONGATION DATA.

• Supplemental Notes:
  • Vol 53, No 8, P 171, 2 PHOT
• Corporate Authors:

  National Bureau of Standards

  Department of Commerce, Office of Technical Publications
  Washington, DC  United States  20234
• Publication Date: 1969-8

Media Info

• Serial:
  • Dimensions NBS

Subject/Index Terms

• TRT Terms: Elasticity (Mechanics); Ethylene resins; Flexibility; Flexural strength; Length; Mathematical models; Modulus of elasticity; Nylon; Physical properties; Plastics; Polyvinyl chloride; Tensile properties; Weathering; Yield strength
• Uncontrolled Terms: Elongation; Polyethylene
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00216892
• Record Type: Publication
• Files: TRIS
• Created Date: Mar 9 1970 12:00AM