ANALYSIS OF PLASTICS BY ATR SPECTROSCOPY

A BRIEF DISCUSSION IS PRESENTED OF THE PRINCIPLES OF THE ATTENUATED TOTAL REFLECTANCE (ATR) METHOD. THE ATR METHOD OF INFRARED SPECTROSCOPY HAS PROVIDED THE INDUSTRIAL SPECTROSCOPIST WITH A METHOD OF ANALYSIS FOR DIFFICULT OR IMPOSSIBLE TO HANDLE SAMPLES. IN THE ATR ACCESSORY UNIT, THE SAMPLE IS PLACED IN CONTACT WITH A PRISM WHICH IS IN TURN PLACED IN THE SAMPLE BEAM AREA OF THE SPECTROPHOTOMETER. THE MIRRORS AND PRISM IN THE OPTICAL PATH OF THE ATR UNIT ARE MOUNTED ON ROTATABLE STAGES ENABLING THE ANGLE OF INCIDENT RADIATION TO BE VARIED FROM 40 TO 65 DEG. IN ORDER TO OBTAIN THE MOST USEFUL SPECTRUM OF THE SAMPLE. WHEN A BEAM OF RADIATION ENTERS THE PRISM AND IS TOTALLY REFLECTED FROM ONE FACE, THERE IS AN EXCHANGE OF ENERGY BETWEEN THE PRISM AND THE SAMPLE SINCE THE SAMPLE IS IN INTIMATE CONTACT WITH ONE FACE OF THE PRISM. SOME OF THE ENERGY INCIDENT ON THE TOTALLY REFLECTING INNER SURFACE OF THE PRISM ESCAPES AND PENETRATES A FEW MICRONS INTO THE SURFACE OF THE SAMPLE. THE ENERGY EXCHANGE IS APPROXIMATELY INVERSELY PROPORTIONAL TO THE INDEX OF REFRACTION OF THE SAMPLE. THE PRISM MATERIAL MUST HAVE A HIGHER INDEX OF REFRACTION THAN THE SAMPLE. A KRS-5 PRISM HAS BEEN USED IN THE WORK REPORTED. IT IS THALLIUM BROMIDE-IODIDE AND HAS AN INDEX OF REFRACTION OF 2.380, WHICH IS HIGHER THAN MOST ORGANIC MATERIALS. FROM APPLICATIONS REVIEWED, IT IS CONCLUDED THAT ATR IS PARTICULARLY VALUABLE FOR SURFACE STUDIES, SUCH AS THOSE ON THE EPOXY CIRCUIT BOARDS AND CELLULOSE ACETATE BUTYRATE DESCRIBED. THE ATR TECHNIQUE MAY BE USED TO DETECT ORGANIC CONTAMINATION ON A SUBSTRATE IF THE ABSORPTION BANDS FROM THE MATERIAL OF INTEREST ARE OF SUFFICIENT INTENSITY TO PRESENT A USABLE SPECTRAL CURVE, AND THE ABSORPTION BANDS FROM THE MATERIAL ARE DIFFERENTIATED FROM ANY ARISING FROM THE SUBSTRATE. THE METHOD HAS BEEN USED TO DETERMINE THE TYPES OF PLASTICIZERS IN THERMOPLASTICS SUCH AS CELLULOSE ACETATE BUTYRATE. EXPERIMENTAL EVIDENCE INDICATES THAT ATR SHOULD PROVE FEASIBLE IN DETERMINING THE DEGREE OF CURE OF EPOXY SYSTEMS BY SURFACE STUDIES OF THE SOLID, CURED MATERIAL.

• Supplemental Notes:
  • Vol 45, No 7, PP 123-126, 7 FIG
• Authors:
  • Kraft, E A
• Publication Date: 1968-3

Media Info

• Serial:
  • Modern Plastics
  • Publisher: McGraw-Hill, Incorporated

Subject/Index Terms

• TRT Terms: Concrete curing; Contaminants; Epoxides; Infrared spectroscopy; Organic deposits; Plasticizers; Reflectivity; Refractivity; Substrates (Waterways); Texture
• Uncontrolled Terms: Attenuation; Contamination; Reflectance; Substrates
• Old TRIS Terms: Attenuated total reflectance; Epoxy
• Subject Areas: Geotechnology; Highways; Materials; Research;

Filing Info

• Accession Number: 00216715
• Record Type: Publication
• Files: TRIS
• Created Date: Mar 10 1994 12:00AM