Use of nano materials in plastic articles

             
BPF position statement on the use of nano materials is plastic articles

Over recent years an increasing interest and awareness in the use of nano technologies has developed across a range of applications.  The number of patents in the area of nano technology has increased significantly over recent years, and it is estimated that Research and Development in this field, in Europe alone, is in excess of 1 billion Euros.  The growing interest in the field of nano technology has led to much discussion amongst NGO groups, regulators and the media.

Recent developments include the ability to grow exceedingly small particles of a material and to give intimate mixtures of such substances with host materials. It is not the materials that are new but the form in which they have been made or “engineered.” For example, the subject of nano technology started in the early 1990s when new types of structures started to be made consisting of carbon spheres of increasing diameters layered on top of each other. A wide variety of new carbon nanostructures, such as endohedral fullerenes, cup-stacked nanotubes, nanohorns, nanotori, nanobuds and graphemes, are now emerging as new forms of carbon whose chemical and physical properties are currently being unravelled. The term nano-technology is generally understood as referring to these types of materials and similarly engineered substances (such as clays and minerals) rather than other materials that have been used safely for many years but may contain small amounts of discrete particles of exceedingly small size.

It is accepted that nano technologies have the potential to bring benefits across a wide range of applications, yet there has also been concern expressed about potential hazardous associated with the use of such materials.

With widespread discussions regarding the use of nano materials, many actors within the plastics industry supply chain are questioning whether or not nano materials are used in plastic articles.

Although the use of the term ‘nano’ is relatively new, particles in the nano scale, both naturally occurring and synthetic, have been in use for many years. Nanoparticles are all around us in nature, for example nanoparticles of minerals in water and nano particles in the air which are the products of combustion (i.e from motor vehicles). 

The ISO definition of a nano-particle (ISO –TS 27687) is of a particle between 1 and 100 nm.  It is also important to note that particles may exist in a range of formats.  There is the primary particle size (which may exist as a needle, plates or as spherical particles).  These may be nano in one dimension, yet not in another.  Materials may also form aggregates or agglomerates.  Each of these factors can lead to variations in the determination of particle size.

In typical colorant masterbatch products (both liquid and solid masterbatch technologies), dyestuffs, pigments and additives are distributed throughout a carrier material.  Dyestuffs are soluble in the polymer and dissolve.  Pigments are insoluble and will be present in the polymer in their particulate form.  There is a huge range of commercially available pigments for such uses.  These pigments are not marketed as nanomaterials, nor are they necessarily specifically engineered or manufactured to be in the <100nm range.  Many manufacturers of such materials do not measure the particle size in the nano range but will provide information on the particle size distribution, and for example the proportion of materials below a particular particle size (100µm for example).  It is however well documented that many common pigments may include particles in the nano range. Some examples are:

Material	Particle size (nm)
Carbon Black	10-80
Titanium Dioxide	20-1000
Zinc Oxide	20-1000
Silica	<100
Iron oxide	50-1000
Chrome oxide pigments	300-400
Ultramarine pigments	300-800

These materials will also span a range of particle sizes, representing a normal distribution curve, whereby some of the primary particles will be of lower dimensions than the example given above.

There have been requests for suppliers of such materials to provide statements confirming that no nano scale materials are used by those in the plastics industry supply chain.  Based on the above information such statements are not possible since some materials contain at least a  fraction of particles between 1 and 100 nm as a result of the manufacturing technology used to produce them. These are not newly engineered materials. They have been used safely for many years and several have been authorised for use in food packaging following a review of dossiers by the relevant competent authorities.  It is also important to note that it is the air-borne nanoparticles that are of most concern to human health due to the inhalation risk that they present. In polymer applications, these pigments/additives are encapsulated in the polymer matrix. They tend to have low solubility in food simulants and do not migrate or leach from the polymer.  The term is new but “nano” pigments have been used in polymer applications (as well as coatings and cosmetics) for a number of years. They are not commonly declared as nano materials so many actors in the supply chain may not be aware of their use.

The European Commission’s Scientific Committee on Emerging and Newly Identified Health Risks has recently adopted its opinion on “Risks Assessment of Products of nanotechnologies”.  The final paragraph of the executive summary states:

“The health and environmental hazards were demonstrated for a variety of manufactured nanomaterials. The identified hazards indicate potential toxic effects of nanomaterials for man and environment. However, it should be noted that not all nanomaterials induce toxic effects. Arguably, some manufactured nanomaterials have been in use for a long time (carbon black, TiO2) and show low toxicity. The hypothesis that smaller means more reactive and thus more toxic cannot be substantiated by the published data. In this respect nanomaterials are similar to normal substances in that some may be toxic and some may not. As there is not yet a generally applicable paradigm for nanomaterial hazard identification, a case by case approach for the risk assessment of nanomaterials is recommended.’’

This opinion supports the approach that each application of such materials should be evaluated to ensure suitability for the intended end use, but there is no reason to think that simply because of the new concept of ‘nano materials’ that substances that have been in use in plastics applications for decades are new novel materials. Plastics materials, whether incorporating materials in the particle size range 1 to 100 nm or not, will comply with all regulations pertinent to the application in which they are being used. For example, when used in food packaging applications all polymer additives will be listed on Annex III of EU Directive 2002/72/EC or national lists of approved substances.

In summary, the BPF continually strives to ensure that there should be adequate flow of information thoughout the supply chain to ensure safe use of all substances in their intended applications (whether nanoscale or not). Proposed amendments to the REACH regulation to encompass nano materials may help further in this respect.  However provision of blanket statements confirming that no nano materials are present in any polymer applications are not possible without consideration of individual substances or further clarification from the relevant authorities in this area.

References: 

• Nanoscience and nanotechnologies: opportunities and uncertainties, The Royal Society & The Royal Academy of Engineering , July 2004
• Inorganic coloured pigments today, Hartmut Undriss
• ISO_TS 27687, ISO, Geneva
• Science Insights, Royal Society of Chemistry, April 2008

 

 

 22/05/09