Verifying materials compliance

This Issue This is a part of the Material durability feature

By - , Build 182

To help combat the problem of non-compliant and substituted building materials, BRANZ is advancing its work using special technology that chemically identifies the composition of materials to weed out any fakes.

FTIR spectrometer
FTIR spectrometer
Build 182 66 Feature Material Durability Verifying Material Compliance 2
Figure 1: Materials verification by FTIR spectroscopy is achieved by generating a unique chemical fingerprint for a particular building product.
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Figure 2: FTIR spectrum showing a mixture of polyethylene (red) and polypropylene (blue) materials. Identification is based on the locations of the peaks at specific frequencies on the horizontal axis (wavenumber). The heights of the peaks on the vertical axis (absorbance) indicate the relative amounts of radiation absorbed at each frequency.
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Figure 3: The FTIR spectrometer can be used in the laboratory or detached and used in portable mode.

THE NEW ZEALAND construction industry needs help to tackle the serious problem of non-compliant materials and product substitution.

A specified product can be relied on to perform to an expected standard over a stated timeframe. While cheaper alternatives may look identical to specified products, substituted materials may behave very differently in terms of durability, weathertightness, fire safety or other critical parameters. Warnings about non-compliant products have been sounded for some time now (see, for example, Beware non-compliant products in Build 137 in 2013) but detection can be difficult before damage or failure starts to become apparent.

Solution to non-compliant materials problem

One potential solution suggested by industry groups has been to investigate the potential for a building product register to be developed. This register would be similar to the existing National Product Catalogue that functions as a single repository for data across multiple product types.

Another approach, currently being progressed by the Ministry of Business, Innovation and Employment is to mandate a minimum set of information for building products. The legislative process for this work is already under way.

BRANZ extending research using FTIR

BRANZ is supporting efforts in establishing materials compliance through extension of previous research described in Are materials the real deal? in Build 162. This explored how Fourier transform infrared (FTIR) spectroscopy could assist product verification by confirming the chemical composition of materials.

The aim of the new research is to use the same FTIR methodology to scope the feasibility and practicality of supplying a materials verification component to the information already held for any given building product.

The materials verification component is based on generating a unique chemical fingerprint for that product, adding another layer of product authentication (Figure 1). Materials could be tested to check that they match the chemical fingerprint of the expected product.

Build 182 66 Feature Material Durability Verifying Material Compliance 2
Figure 1: Materials verification by FTIR spectroscopy is achieved by generating a unique chemical fingerprint for a particular building product.

FTIR gives a chemical fingerprint

FTIR spectroscopy uses a beam of infrared radiation to make the molecules in a material move and vibrate. The vibrations are measured across a range of frequencies (wavenumbers) and are highly characteristic of the material. The output from an FTIR analysis is called a spectrum (Figure 2).

A spectrum can be thought of as a chemical fingerprint for identification purposes. This fingerprint can be used to verify that the product being used is the product that was originally specified as compliant. In this way, compliant materials can be chemically distinguished from visually identical substitutes.

Figure 2: FTIR spectrum showing a mixture of polyethylene (red) and polypropylene (blue) materials. Identification is based on the locations of the peaks at specific frequencies on the horizontal axis (wavenumber). The heights of the peaks on the vertical axis (absorbance) indicate the relative amounts of radiation absorbed at each frequency.

Excellent way to authenticate materials

While most of our FTIR analysis is done in the laboratory, the instrument is portable and can easily be transported, enabling sampling to be carried out on site (Figure 3). A recent software upgrade has also boosted the analytical capability of our FTIR, simplifying the identification of different components within products and allowing more advanced quantitative analysis of materials than we have been able to do previously.

Our previous work has already provided preliminary data to assess the technical feasibility of using an FTIR-based approach for augmenting existing product information. It is an excellent choice for materials authentication because it is:

  • rapid – data is obtained in a matter of minutes
  • reliable – the equipment is robust, and the system performance remains stable over extended timeframes
  • proven technology – FTIR spectroscopy has a long history of use in multiple scientific fields
  • portable – as previously mentioned, on-site use is possible
  • non-destructive – sample preparation is not required, and materials are not destroyed during analysis
  • broadly applicable – a very wide range of materials can be analysed, with the only major exception being metals.
Figure 3: The FTIR spectrometer can be used in the laboratory or detached and used in portable mode.

Testing technical feasibility

A major technical unknown that will be addressed in this work is the sensitivity of the method. We need to be confident that similar products can be adequately distinguished. We must also be sure that the method is capable of handling the expected range of compositional differences for a particular product to be able to discriminate between compliant and substituted materials. The effect of material ageing also needs to be investigated.

Even with technical feasibility established, it is essential that the FTIR-based approach will work within the context of a product register or minimum product information legislation. Important considerations include:

  • confidentiality of product information
  • access to product data
  • conformation of data to any specific standards or format
  • how data is shared in practice
  • how data is maintained and updated
  • how on-site data is compared with reference FTIR data in the register.

Initial work on passive fire protection products

Initial work on technical feasibility is focusing on products used for passive fire protection. Product substitution is a major concern for fire separation reliability and external fire spread performance in buildings. Both are key areas of investigation for the new Building fire-safe densified housing programme of research at BRANZ that is now under way.

Improving confidence in the passive fire products installed in real buildings and reducing uncertainties around potential substitutions is an example of how the compliant materials verification research could be used in a practical context.

For more

If you have any comments, contact the project leader, Catherine Nicholson, at [email protected] This work is supported by the Building Research Levy.

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Articles are correct at the time of publication but may have since become outdated.

FTIR spectrometer
FTIR spectrometer
Build 182 66 Feature Material Durability Verifying Material Compliance 2
Figure 1: Materials verification by FTIR spectroscopy is achieved by generating a unique chemical fingerprint for a particular building product.
Figure 2: FTIR spectrum showing a mixture of polyethylene (red) and polypropylene (blue) materials. Identification is based on the locations of the peaks at specific frequencies on the horizontal axis (wavenumber). The heights of the peaks on the vertical axis (absorbance) indicate the relative amounts of radiation absorbed at each frequency.
Figure 3: The FTIR spectrometer can be used in the laboratory or detached and used in portable mode.

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