Wisdom For Polyethylene vol.2

2. List of Polyethylene Analysis Methods

2024-01-25

To select appropriate packaging materials, it is essential to have a detailed understanding of material properties.
In particular, when replicating products using the same raw materials as existing polyethylene bags, accurate resin analysis is required.

Here, we will explain commonly used methods for material analysis of polyethylene bags.
The following analytical methods are generally employed to identify the materials of polyethylene bags.

(1) Infrared Spectroscopy (IR)

Since infrared spectra always show the same pattern when they are the same substances, we compare the analyzed spectra with the known spectra to identify the materials.

Figure 2: IR Spectrum of High-Pressure Low-Density Polyethylene

Figure 3: IR Spectrum of Medium-Low Pressure High-Density Polyethylene

(2) Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry is a method of recording the energy required to keep the temperature difference between the sample and the reference material at zero over time or temperature under identical conditions while heating.

(3) Polarization Microscope

In the case of multilayer film, observation is made at magnifications of 150× to 300× using a polarization microscope to analyze the interlayer composition. This is a common analytical procedure, but it is not possible to identify resin manufacturers or resin grades. Additives may also be analyzed by pyrolysis gas chromatography (PGC) if their presence needs to be confirmed.

3. Two Main Steps of Making Poly Bags