The experts at Extrusion Consulting have the experience and expertise needed to resolve issues related to the polymeric materials. We often start with polymer recommendations to ensure that your material choice will perform adequately for the intended application. When issues arise we are ready to respond with data driven decision-making empowered by analytical testing. We have relationships with several large North American testing laboratories and a team of polymer scientists through our association with BHC Associates to address any issue. Regardless if your issue is inadequate stabilization, polymer variability including variable pigment or filler levels, polymer contamination, the impact to product quality can destroy the profitability of your business. Our founder, Dr. Bryan Hauger, spent a few years working for a plastics testing company. We can work with your staff to focus testing on those areas likely to produce the results you need. We have access to FTIR testing, DSC, TGA, rheology, and hundreds of ASTM standard test methods for plastics and rubber materials.
A few examples are discussed below.
FT-IR Investigation for Polymeric and Other Contaminants
Investigation of polymeric materials by Fourier-transform Infrared (FT-IR) spectroscopy can lead to the identification of peaks in specific regions of the spectrum that can be attributed to other polymers. This is discussed in ASTM E1252 “Standard Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis”. It is typical in such analysis to mathematically remove the peaks contributed by the known film components from the measured spectrum resulting in a “difference” spectrum. In some cases, the remaining peaks for the polymeric contamination can be identified by software provided with the FTIR instrument usually referred to as “spectral matching”. Other types of contaminants aside from polymeric materials can sometimes also be identified.
DSC Investigation for Thermoplastic Contamination
Investigation of contamination by Differential Scanning Calorimetry (DSC) can lead to the identification of multiple endotherms that can be attributed to melting (or other thermal transitions) of other polymers. ASTM D3418 is titled “Standard Test Method For Transition Temperatures Of Polymers By Differential Scanning Calorimetry”. Since the melting endotherm for the major film components can be established through testing known materials supplied by the clinet, any other melting endotherms can be used to identify a thermoplastic contaminant. Typically, the DSC in run in a cyclic manner in a heat-cool-heat analysis in which the temperature of the sample is increased from room temperature to a much higher temperature to identify an endotherm associated with melting of HDPE along with any other material present. The sample is then cooled to nearly room temperature which often results in a crystallization exotherm. Finally, the heating process is repeated to give a second look at the melting behavior of the sample.
SEM/EDS Investigation for Contamination
A scanning electron microscope (SEM) is a type of electron microscope that produces images by scanning the surface of a sample with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface structure as well as the elemental composition of the sample. The signal intensity, depends, among other things, on specimen topography with resolution that commonly exceeds the best light microscopes.
When traditional SEM is used on some plastic materials, it is possible under high vacuum to create a charge at the surface of the sample which interferes with imaging. Some non-conductive polymeric materials tend to accumulate charge under high vacuum when scanned by the electron beam creating issues for SEM imaging. For conventional imaging in the SEM, specimens must be electrically conductive, at least at the surface, and electrically grounded to prevent the accumulation of electrostatic charge. Non-conducting materials are usually coated with an ultrathin coating of electrically conducting material, deposited on the sample often by low-vacuum sputter coating. A common conductive material coating is gold/palladium alloy. However, this surface coating completely obscures the actual surface of the sample and eliminates the possibility of using energy dispersive X-ray spectroscopy (EDS) detectors.
Alternatively, nonconducting specimens may be imaged without coating using an environmental SEM (ESEM) which allows a relatively high pressure region around the sample to neutralize charge along with adjustment of other variables such as the incoming beam current and accelerating voltages. ESEM thereby allows for measurement of the energy of photons emitted directly from the specimen surface and provides for elemental identification and analysis. In ESEM using EDS detectors it is common to color code these extra signals and superimpose them in a color image, so that differences in the distribution of the various elements of the specimen can be imaged. Since the elemental composition of the smarting materials can be separately documented, the presence of other elements in the film defect can be highly useful in identification of contaminants present in this location.
Oxidative-Induction Time (OIT) for Material Stabilization
A test method that is commonly employed to probe the extent of antioxidant stabilization of plastic materials is ASTM D3895 titled “Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry”. Speaking generally, thin films are placed into a differential scanning calorimeter (DSC) and heated to above the melting point at a constant rate of heating. Heating is initially conducted in a flowing nitrogen atmosphere. At a specified temperature, the flowing gas changes to oxygen while the temperature of the sample is held constant. When a steep rise in heat evolved from the sample is observed, the reaction between the polyolefin and the oxygen has reached a critical point. The time elapsed following the flow of oxygen starting to the time at which excess heat is measured is called the induction time and is reported as the experimental result. While OIT is not a direct measure of chemical degradation, it is an indication of the level (or degree) of antioxidant stabilization and is therefore widely used as a method of monitoring the extent of oxidative degradation of polyolefin materials. Caution should be used when interpreting the data since there are not well-established sampling procedures nor is there a simple relationship between measured OIT values and service lifetime. However, instances in which antioxidant stabilization has been severely reduced (for example OIT values less than 10 minutes) can be associated with a tendency of the component materials to degrade under the conditions of processing.
A few examples are discussed below.
FT-IR Investigation for Polymeric and Other Contaminants
Investigation of polymeric materials by Fourier-transform Infrared (FT-IR) spectroscopy can lead to the identification of peaks in specific regions of the spectrum that can be attributed to other polymers. This is discussed in ASTM E1252 “Standard Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis”. It is typical in such analysis to mathematically remove the peaks contributed by the known film components from the measured spectrum resulting in a “difference” spectrum. In some cases, the remaining peaks for the polymeric contamination can be identified by software provided with the FTIR instrument usually referred to as “spectral matching”. Other types of contaminants aside from polymeric materials can sometimes also be identified.
DSC Investigation for Thermoplastic Contamination
Investigation of contamination by Differential Scanning Calorimetry (DSC) can lead to the identification of multiple endotherms that can be attributed to melting (or other thermal transitions) of other polymers. ASTM D3418 is titled “Standard Test Method For Transition Temperatures Of Polymers By Differential Scanning Calorimetry”. Since the melting endotherm for the major film components can be established through testing known materials supplied by the clinet, any other melting endotherms can be used to identify a thermoplastic contaminant. Typically, the DSC in run in a cyclic manner in a heat-cool-heat analysis in which the temperature of the sample is increased from room temperature to a much higher temperature to identify an endotherm associated with melting of HDPE along with any other material present. The sample is then cooled to nearly room temperature which often results in a crystallization exotherm. Finally, the heating process is repeated to give a second look at the melting behavior of the sample.
SEM/EDS Investigation for Contamination
A scanning electron microscope (SEM) is a type of electron microscope that produces images by scanning the surface of a sample with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface structure as well as the elemental composition of the sample. The signal intensity, depends, among other things, on specimen topography with resolution that commonly exceeds the best light microscopes.
When traditional SEM is used on some plastic materials, it is possible under high vacuum to create a charge at the surface of the sample which interferes with imaging. Some non-conductive polymeric materials tend to accumulate charge under high vacuum when scanned by the electron beam creating issues for SEM imaging. For conventional imaging in the SEM, specimens must be electrically conductive, at least at the surface, and electrically grounded to prevent the accumulation of electrostatic charge. Non-conducting materials are usually coated with an ultrathin coating of electrically conducting material, deposited on the sample often by low-vacuum sputter coating. A common conductive material coating is gold/palladium alloy. However, this surface coating completely obscures the actual surface of the sample and eliminates the possibility of using energy dispersive X-ray spectroscopy (EDS) detectors.
Alternatively, nonconducting specimens may be imaged without coating using an environmental SEM (ESEM) which allows a relatively high pressure region around the sample to neutralize charge along with adjustment of other variables such as the incoming beam current and accelerating voltages. ESEM thereby allows for measurement of the energy of photons emitted directly from the specimen surface and provides for elemental identification and analysis. In ESEM using EDS detectors it is common to color code these extra signals and superimpose them in a color image, so that differences in the distribution of the various elements of the specimen can be imaged. Since the elemental composition of the smarting materials can be separately documented, the presence of other elements in the film defect can be highly useful in identification of contaminants present in this location.
Oxidative-Induction Time (OIT) for Material Stabilization
A test method that is commonly employed to probe the extent of antioxidant stabilization of plastic materials is ASTM D3895 titled “Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry”. Speaking generally, thin films are placed into a differential scanning calorimeter (DSC) and heated to above the melting point at a constant rate of heating. Heating is initially conducted in a flowing nitrogen atmosphere. At a specified temperature, the flowing gas changes to oxygen while the temperature of the sample is held constant. When a steep rise in heat evolved from the sample is observed, the reaction between the polyolefin and the oxygen has reached a critical point. The time elapsed following the flow of oxygen starting to the time at which excess heat is measured is called the induction time and is reported as the experimental result. While OIT is not a direct measure of chemical degradation, it is an indication of the level (or degree) of antioxidant stabilization and is therefore widely used as a method of monitoring the extent of oxidative degradation of polyolefin materials. Caution should be used when interpreting the data since there are not well-established sampling procedures nor is there a simple relationship between measured OIT values and service lifetime. However, instances in which antioxidant stabilization has been severely reduced (for example OIT values less than 10 minutes) can be associated with a tendency of the component materials to degrade under the conditions of processing.
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