ATR-FTIR Spectrometer for Polymer Analysis

What is the ATR-FTIR Spectrometer for Polymer Analysis?

An ATR-FTIR spectrometer measures solid and opaque polymer samples by total internal reflection in a crystal pressed against the surface. It is the practical choice for pellets, moulded parts, films and rubbers that cannot be dissolved or pressed into transparent films.

Overview

In attenuated total reflection the infrared beam travels through a crystal of high refractive index and reflects at the crystal-sample interface, where a small evanescent wave extends a few micrometres into the sample and is absorbed at characteristic frequencies. Common crystals are diamond for scratch resistance and wide pH tolerance, zinc selenide for a broad spectral range and germanium for very shallow sampling depth. Single-reflection designs need only a small contact area, while multi-reflection plates increase sensitivity for thin coatings. The measurement is quick, requires no consumables and is largely non-destructive, which makes it suitable for checking a finished part in a quality dispute. Contact uniformity, crystal cleanliness and pressure applied by the clamp determine the quality of the result.

How does it work?

Molecules absorb infrared radiation at frequencies that match their vibrational modes, so a spectrum of absorbance against wavenumber acts as a fingerprint of the polymer backbone and of the additives present. Fourier-transform instruments use an interferometer and a mathematical transform to record the full spectrum quickly and at high signal-to-noise ratio. Attenuated total reflection brings the beam into a high-refractive-index crystal in contact with the sample, so surface layers of a few micrometres can be measured without preparation. Raman spectroscopy complements this by measuring inelastically scattered light from a laser, which is sensitive to non-polar bonds, and near-infrared spectroscopy records overtone and combination bands that are weak but penetrating, making it suitable for rapid screening through packaging or with fibre probes.

What are the key features?

• Diamond single-reflection ATR crystal
• Sampling depth of a few micrometres
• No KBr pressing, grinding or solvent
• Interchangeable ZnSe and Ge crystals
• Clamp for reproducible contact pressure
• Rapid cleaning between samples

What are the technical specifications?

A typical atr-ftir spectrometer for polymer analysis configuration offers spectral range of 4000–400 cm⁻¹ with ZnSe, resolution of 1–4 cm⁻¹, ATR crystal of Diamond, single reflection, sampling depth of About 2 µm at 1000 cm⁻¹ (diamond), contact area of About 1 mm diameter and pressurisation of Screw clamp with torque limit. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The ATR-FTIR Spectrometer for Polymer Analysis is used in pellet and granulate identification without preparation, rubber and elastomer surface analysis, coating and film on-substrate measurement and screening complaints about contamination. Across the wider Polymer Spectroscopy class, laboratories also deploy it for incoming identification of resin and rubber grades, contaminant and gel particle analysis and additive, filler and plasticiser detection.

Which standards and certifications apply?

Relevant standards and methods include ASTM E1252, ASTM E168, ASTM D5576, ASTM D3677, ISO 4650, ASTM E1840 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Keep the spectrometer purged or desiccated because water vapour and carbon dioxide bands appear in the mid-infrared and can mask weak peaks. Run a background scan at the same resolution and purge conditions as the sample, and verify wavenumber calibration with a polystyrene film at defined intervals. For ATR work, clean the crystal immediately after each measurement and check for scratches, because damaged surfaces distort bands. Raman systems should be calibrated against a standard such as silicon or cyclohexane, and laser power must be limited for dark or heat-sensitive polymers to avoid burning the sample.

How do I select the right ATR-FTIR Spectrometer for Polymer Analysis?

Select an ATR configuration whenever the sample is a solid part, a pellet, a rubber strip or a coated substrate, and whenever you want to avoid consumables and solvent disposal. Choose a diamond crystal for general use and for abrasive or chemically aggressive samples, and a germanium crystal when the analysis must be restricted to the outermost surface layer.

How does it compare with other Polymer Spectroscopy variants?

Infrared is the default for polymer identification because spectral libraries are extensive and the method is well standardised. Add an attenuated total reflection accessory when samples are solid, opaque or dirty, since it removes pressing, grinding and solvent steps. Choose an infrared microscope when the target is a contaminant, a gel particle or a multilayer film that must be measured at a defined point or mapped across a surface. Raman is preferred for aqueous samples, for polymers that are strong infrared absorbers such as filled or black materials, and for portable field identification through transparent packaging. Near-infrared is selected for high-throughput screening and quantitative additive or moisture measurement using chemometric models.