In order to achieve the reliable production of top-quality goods, it is vital to source raw materials which are safe and of a high quality. Nevertheless, whether as a cost-cutting method or as a result of being unable to support changes in materials that have been dictated by codes of practice, suppliers may alter their materials, often without the manufacturer being made aware. In Japan, this is referred to as a ‘silent change’.
Not only does the use of non-standard raw materials risk the integrity of a product’s quality, but it has also been linked to accidents, and it is thus becoming a societal issue. In order to avoid such issues, manufacturers can carry out checks on delivery to determine whether the raw materials received meet their expected standards.
This article will cover the examination of samples which could have been subject to a ‘silent change’ (referred to in the remainder of this article as a ‘silent change’ product), and will offer case studies which support the existence of such changes through the use of energy dispersive X-ray fluorescence spectrometry (EDX) (Figure 1) and FTIR infrared spectrophotometry (Figure 2).
Figure 1. EDX-7000 Energy Dispersive X-Ray Fluorescence Spectrometer.
Figure 2. IRAffinity-1S with MIRacle 10 Single-Reflection ATR Accessory.
Case of Replacement with a Cheaper Metal Material
Stainless steels are formed through the addition of a variety of materials, including chrome and nickel, to iron to create special kinds of steel that are resistant to rust. The stainless steel entitled SUS316 has the composition 18Cr-12Ni-2.5Mo. It is formed through the addition of molybdenum to SUS304 stainless steel, which increases its resilience against corrosion from sea water and other materials.
In this study, EDX was employed to analyze the stainless steel in both a genuine product and a ‘silent change’ product. The conditions of the analysis are displayed in Table 1, and Figure 3 shows the EDX profiles.
Table 1. EDX Analytical Conditions
||: Rh target
||: 50 kV (Na-U) /Auto
||: 10 mmφ
||: 30 sec.
In Figure 3, it can be seen that the ‘silent change’ product is lacking in the molybdenum peak seen in the genuine SUS316, and instead, presents a profile matching SUS304, demonstrating that the steel material in the ‘silent change’ product has been replaced with a lower-cost variety.
Figure 3. Results of EDX Analysis of SUS316 Genuine Product and "Silent Change" Product (SUS304).
While visual examination alone would never have revealed a change in the steel material, the measurements supplied by EDX proved that a ‘silent change’ had taken place.
Case of Replacement of a Plastic Material
FTIR was employed to study a genuine polypropylene (PP) product alongside a ‘silent change’ product. The conditions of the analysis are displayed in Table 2, while Figure 4 shows the spectra obtained. In Figure 4, a peak can be seen in the ‘silent change’ product which stems from CH2 rocking vibrations in the zone of 718 cm-1 (indicated with a star).
Figure 4. Results of FTIR Analysis of Genuine PP Product and "Silent Change" Product (PP+PE).
It was confirmed through spectral search that the ‘silent change’ product contained polyethylene (PE) mixed together with PP. These findings suggest that the raw materials may have had recycled plastics added in.
Case of Toxic Element and Different Material Mixed into a Plastic Material
In order to study a genuine polyvinyl chloride (PVC) product against a ‘silent change’ product, both EXD and FTIR were used. Table 1 displays the conditions for analysis relating to EDX, with corresponding profiles shown in Figure 5. For FTIR, conditions of the analysis can be seen in Table 2, and corresponding spectra data can be seen in Figure 6.
Table 2. FTIR Analytical Conditions
MIRacle 10 (Diamond/ZnSe)
||: 4.0 cm-1
Figure 5. Results of EDX Analysis of Genuine Plastic Product and "Silent Change" Plastic Product.
Figure 6. Results of FTIR Analysis of Genuine Plastic Product and "Silent Change" Plastic Product.
In the ‘silent change’ product, lead was detected that was not present in the genuine product. This is indicated in Figure 5, with the lead marked with a star. The plastic in question is subject to regulations under the Restriction on Hazardous Substances Directive (RoHS) and therefore must not demonstrate any indication of containing lead. As such, these findings indicate that the ‘silent change’ product fails to comply with RoHS regulations.
In Figure 6, as indicated with a star, it can be seen that, in addition to peaks stemming from PVC, there were also peaks stemming from acrylic shown in the area of 2,900 cm-1 and 1,700 cm-1. These findings indicate the existence of a differing material mixed together with the expected material in the ‘silent change’ product.
Stronger protection against the issue of ‘silent change’ counterfeiting can be achieved through the use of EDX and FTIR to check organic and inorganic materials.
This information has been sourced, reviewed and adapted from materials provided by Shimadzu Scientific Instruments.
For more information on this source, please visit Shimadzu Scientific Instruments.