Analysis of Gel Contamination

Intertek undertakes comprehensive testing and analysis of the phenomenon of gels as they can have a major impact on product quality, performance and appearance. 

Gels necessitate exhaustive testing and analysis as they are common to the polyethylene, polyester, films and polypropylene industries. By nature they are difficult ‘sticky’ contaminants and may manifest in various forms: within certain products - such as a personal care product as shampoo - they may appear as a thickening or lump, and also may appear as a ‘fish-eye’ aesthetic deformity, for example in the shampoo bottle itself.

They are very common in the plastics and polymer industries, and may form as a result of overheating: within polyester production this may take the form of crosslinked gels; from catalyst residue (for example an iron particulate), mostly in stagnating and ‘dead’ regions of resins, during extrusion or as a result of other organic or inorganic contamination, as degraded oxidation related occurrences. They may also have their roots in the supply chain.

Gels can exist at the molecular level, causing performance defects and affecting viscosity which may necessitate the use of GPC processes to define their molecular weight.

They can lead to weak points and rupturing, compromise of materials, scrapping of product, considerable QC issues - appearing as surface defects - and, crucially, gel contaminants can be precursors to failure as they contribute to overall stress factors.

The Intertek analytical research and development laboratories have vast experience in gel defect investigation, right through to the location of the source.

The chemical nature of the gel is able to be assessed via microscope based techniques, followed by FTIR, which may be most suitable if the gel is due to foreign contamination, for example cellulosic fibres or, in the case of a crosslinked gel, due to unintended mixing of polymers of different densities, enabling a view of the gel’s IR transmission spectrum. 

As gels can exist as a visible, light scattering particulate; for example, as fish eye contaminants or unmelted polymers knowns as ‘nibs’, they may be identified with methods such as pyrolysis or EDX. 

Other techniques will include Raman spectroscopy which is suitable for analysis of gels, and also NMR spectroscopy once the gel is no longer in the ‘particulate’ state.

Intertek possesses a wealth of knowledge in polymer and chemical formulation testing and will assist you, whether it is a high molecular weight gel, a reaction side-product, poor formulation, cross-contamination of another product or symptom of a larger contamination issue. Our analytical research and development laboratories possess the expertise and insight to quickly identify the defect and resolve your problem using our state of the art equipment and methodology.