This glossary of polymer testing terms is intended to clarify some of the language you may come across while determining what services your organization needs.
Please contact us with your questions regarding how these and other processes, techniques and technologies apply to you.
ATOMIC FORCE MICROSCOPY
Atomic Force Microscopy (AFM) can provide information about surface morphology – much like the Scanning Electron Microscope (SEM), but at a much higher resolution. The AFM can distinguish phases in blends as well as the distribution of fillers and other additives by showing differences in the densities of the materials.
Often referred to as “reverse engineering”, deformulation is a systematic approach to determining the identity and quantity of the various components comprising a polymer compound or final product. The practices employ multiple disciplines that hone in on specific ingredients to facilitate developing a comparable or superior product.
DIFFERENTIAL SCANNING CALORIMETRY
Differential scanning calorimetry (DSC) determines a wide variety of thermal events involving heat change – either providing a way of categorizing a transition temperature or providing quantitative data on the degree of change. Examples of information DSC obtains include glass transitions, phase changes, crystalline transitions, blend compatibility, heats of vaporization and melting, purity determination, reaction kinetics, reaction onset temperatures, specific heat capacity and oxidative reactions.
ENERGY DISPERSIVE X-RAY ANALYSIS
Energy dispersive X-ray analysis (EDX) provides the elemental composition of solids or powdered samples. Semi quantitative results can be obtained without the need for standards. In bulk EDX elements with atomic numbers greater than 10 can be detected. When used in conjunction with a SEM, elements with atomic numbers greater than 5 can be analyzed.
FAILURE ANALYSIS AND PREVENTION
Failure is a term used to describe any material or product that does not perform the way it was expected to perform. Failure analysis is the investigation of the cause(s) of failure and the recommendation of remedial steps to avoid future failures. Failures can be due to problems with the material, processing, design, or the environment. It can involve the use of many analytical methods as well as the measurement of physical properties.
Safety from the hazards of fires in buildings, homes and transportation vehicles is an important public goal. The fire science laboratory can evaluate a variety of flammability characteristics of materials including flame spread, smoke generation and heat released.
FOURIER TRANSFORM INFRARED (FTIR) SPECTROSCOPY
Fourier transform infrared (FT-IR) spectroscopy is a versatile and sensitive technique for the identification of chemical compounds in samples. In pure compounds and in simple mixtures, a complete identification of all components is often possible from the functional group “fingerprints.” It is an excellent technique for:
- Polymer identification
- Confirming composition of raw materials
- Verifying compound composition
- Identifying reaction products
- Surface analysis
- Contamination identification (for particles as small as 20 µm)
- Quantitative determination of polymer compound compositions
Scientists employ gas chromatography (GC) to separate and quantify volatile components in complex mixtures. It is especially important in residual monomer determinations. It is often combined with mass spectroscopy to allow for the individual components to be identified (aka GC-MS).
HIGH PERFORMANCE SIZE-EXCLUSION CHROMATOGRAPHY (HP-SEC)
High performance size-exclusion chromatography (HP-SEC or SEC), also known as gel permeation chromatography (GPC), is used to fractionate a polymer sample according to the size of the molecules in solution. As such, it is the standard method for molecular weight determination.
Liquid Chromatography (LC) is a separation technique for the quantitative analysis of organic and ionic substances. It is ideally suited for those substances which are nonvolatile or thermally labile, making them unsuitable for gas chromatography.
Moisture can be determined separately from other volatiles using a Karl Fischer coulometric method. In addition, several loss on drying methods also can be used to estimate moisture content.
NUCLEAR MAGNETIC RESONANCE SPECTROMETRY
Nuclear magnetic resonance (NMR) spectrometry identifies structure in organic compounds and organic components in mixtures. The technique is well suited for analysis of high-boiling liquids and polymers that are soluble in organic solvents or in water. NMR uses include:
- Determining purity of raw materials
- Identifying residues
- Measuring solution equilibrium
- Determining copolymer composition
- Determining structure of organic compounds
- Measure branching in polymers
- Analyzing mixtures
- Measuring kinetics of reactions
- Identifying additives
- Performing quantitative analysis of mixtures (by Proton NMR)
The optical microscope is a tool for studying details of structure down to approximately 2 µm. Optical microscopes can be equipped with numerous accessories to enable the study of physical characteristics and chemical phenomena.
PARTICLE SIZE CHARACTERIZATION
Particle size and its distribution is a measure of the diameters of the dry powders, latexes, suspensions and dispersions of powders, polymers and compounding ingredients. Particle size issues affect smoothness of coatings, clarity, flow properties, mixing and dispersing characteristics, dust control, filtration, and many other properties.
SCANNING ELECTRON MICROSCOPY
By using the scanning electron microscope (SEM), detailed images of a sample surface with considerable depth of focus can be obtained on solid specimens. Information can be obtained concerning size, shape, and texture on many materials. It is often used in conjunction with EDX.
TGA provides a continuous record of sample weight change during dynamic or isothermal heating. Various atmospheres can be used to investigate sample reactions. TGA also can be coupled with infrared spectroscopy (TGA/FTIR) or gas chromatography and mass spectrometry (TGA-GC/MS) to identify the evolved gases. Applications for TGA include:
- Weight loss/gain
- Drying rate
- Reactivity with atmospheres
- Oxidative degradation
- Reaction kinetics
- Volatilization analysis
- Compound composition
- Stabilizer effectiveness
In TMA, the deformation of a sample under stress (compression, tension, flexure) is measured with temperature. Dilatometry measures sample dimensions under negligible load and can be performed on the TMA instrument as well. Fibers and films can be analyzed as well. Determinations by TMA include: coefficient of linear expansion, glass transition, and shrinkage kinetics.
Thermal conductivity is a measurement to describe how heat transfers through a material and is an important material property. The “flash method” determines thermal conductivity by measuring the thermal diffusivity and specific heat capacity of a sample.
Virtually all common colorants absorb light strongly in the visible region of the spectrum, and many UV stabilizers and anti-oxidants have absorbance in the UV region. These absorbance characteristics make UV-visible spectroscopy a powerful tool for the identification and quantitation of these types of components.
Weathering determines the effect of light, heat, and moisture on a material sample or finished part. The weathering laboratory contains both QUV and Xenon-Arc weatherometers. Either the QUV or Xenon-Arc weatherometer protocols can be designed to simulate numerous conditions.
Typical Polymers Evaluated:
- PVC (polyvinyl chloride)
- Polyethylene (HDPE, LDPE, LLDPE)
- PC (polycarbonate)
- PET (polyethylene terephthalate)
- PBT (polybutylene terephthalate)
- PHBV (polyhydroxyvalerate – co – butyrate)
- PP (polypropylene)
- ABS (acrylonitrile –butadiene-styrene)
- PVA (polyvinyl acetate or polyvinyl alcohol)
- PEEK (polyetheretherketone)
- PPS (polyphenylene sulfide)
- PMMA (polymethyl methacrylate)
- PS (Polystyrene)
- PTFE (polytetrafluoroethylene)
- TPE (thermoplastic elastomer)
- TPR (thermoplastic rubber)
- TPV (thermoplastic vulcanizates)