Atoms or molecules in a crystal are organized in a periodic and regular way. Crystallinity is referred to the extent of structural order in solid products, such as powders and pellets. Compared to crystalline polymers, amorphous polymers lack a degree of crystallization and behave quite differently.
A combination of amorphous and crystalline regions can be created in a large number of polymeric materials, including plastic bottles. In these instances, process methods can be altered by controlling the degree of crystallinity. This approach has a major effect on a polymer’s density, hardness, diffusion, and transparency. It is often stipulated as a volume percentage of the crystalline material.
Organizations that manufacture plastic bottles have to ensure the strength, consistency, and overall quality of products. This can be done by validating the degree of crystallinity in blown bottle walls. Calorimetric or X-ray diffraction methods can be used to determine crystallinity in a lab. However, these techniques are not accurate all of the time, and are relatively slow. This means that the results will not be readily available for inclusion in a Certificate of Analysis for end-user purposes.
However these issues can be overcome using the FT-NIR technique, which helps to measure the crystallinity of plastic bottles in a quick and non-destructive way. Individual bottles can be examined within a fraction of seconds, and even operators without any analytical expertise can easily carry out the test.
While the FT-NIR method shares a similar reproducibility to that of standard lab techniques, it is far better in terms of robustness and repeatability. Here, an ABB MB3600-CH40 FT-NIR instrument is used to determine the degree of crystallinity of polyethylene bottles (Figure 2). The device is also utilized to measure moisture content and thickness of bottle walls.
Figure 1. MB3600-CH80 PET packaging analyzer
Quantitative measurement of the percentage of crystallinity in 88 polyethylene bottles (packaging samples).
The following parameters were used during the test:
- Sampling method: Intact bottles positioned on sampling port.
- Instrument: MB3600
- Detector: InAs TE-cooled
- Chemometrics model: Partial Least Squares (Software Horizon MB Quantify)
- Resolution: 8 cm-1
- Number of scans: 16 (12s /sample)
- Analysis temperature: Room temperature
Figure 1 shows the calibration performance, and Table 1 shows crystallinity in range, R2, and SECV.
Figure 2. Calibration performance
Table 1. Degree of crystallinity
Key User Benefits of ABB FT-NIR
- Multi-component analysis on one sample
- Quick results, within 1 minute
- Substitutes relatively slow wet chemical techniques
- Allows measurement of physical and chemical characteristics
- Low cost per analysis
- Eliminates the need for consumables, reagents, or solvents
Suggested Instrumentation - MB3600-CH80 PET Packaging Analyzer
A robust industrial FT-NIR instrument, the MB3600-CH80 PET packaging analyzer allows rapid analysis of PET containers such as bottles, jars, and preforms. It is suitable for QA/QC labs, research and development centers, and the manufacturing lines of companies that measure the key properties of PET containers on a daily basis.
With the aid of the MB3600-CH80 instrument a number of PET quality features, like intrinsic viscosity, crystallinity, wall thickness, and moisture content, can be accurately measured.
Investigations can also be carried out within a fraction of seconds, making the instrument a suitable alternative to relatively slower laboratory techniques.
There is no need to prepare specific samples or instruments, and measurements are made in a fully non-destructive manner. The operator has to simply place the PET sample to be examined in the analyzer sampling compartment and follow the instructions that are displayed on the screen.
When using the MB3600-CH80 PET packaging analyzer for product analysis, factors like analytical expertise, chemical reagent, or waste disposal are no longer needed.
With an unparalleled FT-NIR calibration expertise, ABB provides turnkey solutions to determine the crystallinity in PET containers. Made out of over 150 PET bottles, the calibrations are pre-loaded on the system and configured in the easy-to-use interface. As soon as the FT-NIR has been installed, users can start their investigations on PET containers. A statistical indicator is measured automatically for each assay to evaluate the quality of the sample recognized by the instrument. In case PET formulations are different or unique from the calibration database, automatic warnings will be displayed. This notifies users that the FT-NIR calibration needs to be tuned to include certain samples of this formulation and to further improve the model’s robustness. Atypical samples or those surpassing the range of crystallinity specified by the pre-loaded model will be rejected automatically.
Apart from crystallinity, the following properties of PET can also be determined with the MB3600-CH80 PET packaging analyzer:
- Intrinsic viscosity
- Wall thickness
- Moisture content
- Acid value
- Hydroxyl value
The above properties are based on customized calibration models that can be developed by end-users, or can be delivered by ABB. Particular sampling accessories can also be introduced as options. These include universal heatable vial holder for analysis of melted plastics or liquids in disposable scintillation vials, and powder sampler for the analysis of pellets, powders, opaque packaging, and other types of solids. These accessories are placed in the MB3600-CH80’s sampling compartment, and through a USB port are joined to the analyzer to facilitate automatic recognition. The accessories can be exchanged easily.
Minimal Cost of Ownership
The MB3600-CH80 PET packaging analyzer comes with a minimal cost of ownership, and features a vertical design that has a small footprint. The modular components of the MB3600-CH80 analyzer, designed by ABB engineers, extend the product life based on the principles given below:
- No adjustments
- No maintenance
- No wear of the scan mechanism
- No consumables
Equipped with electronic stabilization, the pre-aligned source module is designed to function for 10 years without any need for replacements. The metrology module based on solid state laser has a lifespan of 20 years. Non-hygroscopic optics used in the MB3600-CH80 PET packaging analyzer ensure that instrument purging is no longer needed for optical protection. The cost of lab analysis is also considerably reduced, while lab throughput and product consistency are largely enhanced.
The Support and Reliability of a Leading Global Supplier
A leading supplier of lab and process analytical systems, ABB has over four decades of expertise in developing FT-NIR and FT-IR spectrometers for space, military, and industrial applications. For process optimization, the company provides a complete range of application support and custom calibration modeling services for industrial applications. In addition, ABB offers a full customer training program and after-sales support and engineering services across the globe.
This information has been sourced, reviewed and adapted from materials provided by ABB Measurement & Analytics - Analytical Measurement Products.
For more information on this source, please visit ABB Measurement & Analytics - Analytical Measurement Products.