Evaluating Gels in Plastics: Methods, Causes & Quality Control

What Are Gels in Plastic Films?

Gels are unwanted defects in plastic films that compromise quality, processability, and appearance. While technically defined as crosslinked polymer networks that resist flow, "gels" also broadly refer to various visual imperfections. These include unmelted polymer lumps, foreign particles or polymer, moisture-induced fisheyes, and fibrous or inorganic contaminants.

Understanding the origin, type, and impact of these gels is essential in maintaining the integrity and performance of e.g PE, PP, PES, PET, PC, PA, HIPS, EVA or other compounds.

Types of Gels Found in Plastic Films

Point Gels: Caused by crosslinked or unmelted resin, foreign material, or die build-up; appear glassy and vary in color.

Arrow-Shaped Gels: Result from melt index variation or interlayer flow issues; have distinct directional patterns.

Gel Flurries: Randomly scattered translucent gels e.g. from LDPE reactor separator residue.

Non-melting gels: Fibrous contaminants like cellulose, paper, cotton or inorganic additives.

Fisheye Gels: Lens-shaped defects caused by moisture or high humidity during processing.

Why is evaluating gels defects important?  
The evaluation of gel defects is performed in a plastic film. This is necessary to make the gel defect detection possible. This approach can be used to study polymers and plastics used for automotive parts, cable industry and a wide range of other applications.

Gels defects in plastic films pose significant risks beyond mere visual imperfections. They can lead to film breakage, particularly at high processing speeds, and compromise sealing integrity and mechanical strength. Gels can impact everyday usage by consumers such as bursting crisp packets or holes in film sealed meals. In laminated structures, gels may impair barrier properties, reducing overall performance. Visually, they can cause optical defects in clear or printed films, diminishing aesthetic appeal. Hard gels can also damage sensitive equipment such as printing plates, increasing maintenance costs. Ultimately, the presence of gels often results in product rejection, material waste, and costly disruptions to production. 

Our scientists have supported global innovators in new polymer and plastic film development and production for over 30 years. Our complete approach to film development from compounding, lab-scale extrusion and physical, chemical testing and also migration studies for safety assessment form a comprehensive suite of expertise. 

How Gels Are Evaluated: Techniques and Tools

Automated Optical Scanning: Continuous, real-time monitoring. Detects, classifies, and alerts operators to gel events. Highly accurate and reduces waste through instant correction.

Gel Count via Lab-Scale Extrusion: Uses light and camera systems to identify and quantify gel defects. Enables online visualization and real-time quality tracking. Ideal for assessing recycled materials and blends.

Filter Choking Tests: Screens materials to detect trapped gels or contamination which can then be collected for further analysis with microscopy and others. Offers insight into material cleanliness and process behavior.

Advanced Analytical Techniques: Microscopy, FTIR, EDX, Raman, NMR, Pyrolysis: Identify chemical composition, source, and morphology of gels. Suitable for both particulate and molecular-level defect analysis. GPC used to assess impact on molecular weight and flow behavior

Why Partner with Intertek? 

Our scientists have supported global innovators in new polymer and plastic film development and production for over 30 years. Our complete approach to film development from compounding, lab-scale extrusion and physical, chemical testing and also migration studies for safety assessment form a comprehensive suite of expertise. 

Working with a specialist testing laboratories offers a range of valuable advantages for manufacturers dealing with gel-related issues in plastic films. We provide access to science-backed insight from advanced diagnostic tools such as FTIR, NMR, and Raman spectroscopy, enabling precise identification of gel composition and origin. Our expertise spans the entire development process - from lab-scale extrusion to in-depth root-cause analysis - ensuring a comprehensive approach to problem-solving. With decades of experience in polymer formulation and defect resolution, we deliver fast, reliable results that help minimize waste and enhance film quality. Additionally, our knowledge of regulatory and performance testing, including migration and safety assessments, ensures compliance and product reliability.

Contact our polymer experts today to find out how we can help solve your polymer gel issues and resolve issues in either development or production.