What is FTIR Testing? A Complete Guide to Principles, Methods & Applications

What is FTIR Testing?

FTIR is a widely used analytical technique for identifying organic and polymeric—and sometimes inorganic—materials by measuring their infrared absorption spectra. When a sample is exposed to infrared light, its molecular bonds absorb specific wavelengths corresponding to characteristic vibrations. The resulting spectrum acts as a unique “fingerprint” for the material’s molecular composition and structure.

FTIR testing enables the qualitative and quantitative determination of functional groups and chemical bonds in a sample, providing critical information for the identification, purity verification, and degradation analysis of materials. This technique is non-destructive and can be applied to solids, liquids, and gases.

Why is FTIR Testing Important?

FTIR is one of the most powerful and widely used techniques for material characterization and quality control. It helps manufacturers, researchers, and regulatory agencies ensure that materials meet performance, safety, and compliance standards.

FTIR testing helps to:

• Identify unknown materials, contaminants, or defects in products.
• Verify the composition and authenticity of raw materials and finished goods.
• Detect chemical changes caused by degradation, weathering, or aging.
• Ensure regulatory compliance with international quality and safety standards.
• Support product development and failure analysis by revealing molecular-level information.

FTIR plays a key role in industries such as polymers, pharmaceuticals, coatings, electronics, and environmental testing, where understanding chemical composition directly impacts performance, safety, and reliability.

Which Materials Can Be Tested Using FTIR?

FTIR testing is suitable for a wide range of materials, including:

• Polymers and plastics: PE, PP, PVC, PET, PS, ABS, PMMA, PTFE
• Elastomers and rubbers: EPDM, NBR, SBR, silicone rubber
• Coatings and adhesives: Paints, resins, sealants, varnishes
• Fibers and textiles: Nylon, polyester, rayon, cellulose
• Organic compounds: Oils, waxes, fuels, surfactants, and additives
• Inorganic compounds (limited): Some oxides, carbonates, and silicates

Samples can be analyzed in various physical forms, such as films, powders, pellets, liquids, or solid parts, depending on the testing objective and preparation technique.

What Information Do FTIR Test Results Provide?

FTIR spectra provide detailed information about the molecular structure and chemical composition of materials. Key data include:

By comparing a sample’s spectrum to reference databases, FTIR can determine material type, purity, and detect contamination or chemical modification.

What Industries Use FTIR Testing?

FTIR is a versatile technique used in numerous industries for research, development, quality assurance, and regulatory compliance, including:

• Polymers & Plastics: Identification of base resins, additives, and degradation products
• Automotive & Aerospace: Coating verification, rubber composition, and failure analysis
• Electronics: Polymer encapsulant and conformal coating analysis
• Environmental Testing: Detection of microplastics, oils, and organic pollutants

What Equipment Is Used for FTIR Testing?

FTIR testing requires specialized spectroscopic instruments equipped with:

• FTIR Spectrometer: The core unit containing the interferometer and infrared source
• Beam Splitter and Detector: To measure the intensity of transmitted or reflected light
• ATR (Attenuated Total Reflectance) Accessory: Enables direct analysis of solid or liquid samples with minimal preparation
• Transmission / Reflectance Cells: For thin films or transparent materials
• Gas Cells or Liquid Holders: For volatile or fluid samples
• Spectral Libraries: For automated material identification through reference matching

How Is FTIR Testing Performed?

Step-by-Step Overview:

• Sample Preparation:
  Samples are cleaned and prepared according to their physical form. Solids may be analyzed directly via ATR, pressed into KBr pellets, or cast as thin films. Liquids and gases are placed in sealed cells.
• Data Collection:
  Infrared radiation is directed at the sample. The FTIR spectrometer records the amount of light absorbed at each wavelength, generating an interferogram.
• Fourier Transform Processing:
  The instrument mathematically converts the interferogram into an infrared absorption spectrum.
• Spectral Interpretation:
  The resulting spectrum is analyzed for characteristic peaks. These are compared against known reference spectra to identify chemical bonds and materials.
• Quantitative Analysis (Optional):
  For specific applications, the intensity of absorption bands can be correlated with concentration to determine material composition.

What Are the Standard Test Conditions?

Stable environmental conditions and proper calibration are essential for reproducible, high-accuracy spectra.

Key Properties Measured

FTIR measures the vibrational frequencies of molecular bonds, revealing the presence of specific chemical groups and compounds.
The main properties evaluated include:

• Molecular structure and composition
• Chemical bonding and functional group identification
• Degree of oxidation, degradation, or contamination
• Verification of polymer type and filler content

This makes FTIR invaluable for identifying unknown substances, confirming product formulation, and investigating material failures.

Related Testing Methods

• Raman Spectroscopy: A Complementary technique for molecular structure analysis
• Thermogravimetric Analysis (TGA): Evaluates thermal stability and compositional changes
• Differential Scanning Calorimetry (DSC): Measures thermal transitions and crystallinity
• X-Ray Diffraction (XRD): Determines crystalline structure
• Energy Dispersive X-ray Spectroscopy (EDS): For elemental composition analysis in conjunction with SEM

Conclusion

FTIR is a cornerstone analytical technique in material identification, chemical characterization, and quality assurance. It provides a rapid, accurate, and non-destructive means of determining material composition and structure by analyzing the absorption of infrared radiation by various molecular bonds.

From identifying unknown materials to verifying formulations and detecting contaminants, FTIR enables industries to achieve product reliability, regulatory compliance, and scientific innovation.

Why Choose Infinita Lab for FTIR?

At the core of this breadth is our network of over 2,000 accredited labs in the USA, offering access to more than 10,000 test types. From advanced metrology (SEM, TEM, RBS, XPS) to mechanical, dielectric, environmental, and standardized ASTM/ISO testing, we give clients unmatched flexibility, specialization, and scale. You’re not limited by geography, facility, or methodology—Infinita connects you to the proper testing, every time.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090  to learn more about our services and how we can support you. Request a Quote

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