Roundtable: Natural materials

Materials World magazine
,
1 Feb 2014

They make plastic bottles out of plants, protect delicate goods with wool and use rubber to make more elastic plastic. So, what is it like working with natural materials? Eoin Redahan asks the professionals.

Meet the panel  
WOOD: Dr Graham Ormondroyd (GO)
Head of Materials Research, Biocomposites Centre at Bangor University, UK

 

 

 

 

BIOPOLYMERS: Andrew Gill (AG)
Technical Manager of Floreon Transforming Packaging Ltd in Hull, UK

 

 

 

RUBBER: Dr Stuart Cook (SC)
Director of Research, Tun Abdul Razak Research Centre in Hertford, UK

 

 

 

GENERAL PACKAGING: Keith Barnes (KB)
Chairman of the Packaging Society in London, UK

 

 

 

BIOPOLYMERS: Angela Morris (AM)
CEO of the Wool Packaging Company Limited in Shropshire, UK

 

 

 

How are you using natural materials? What are the advantages of the materials you use?
GO The nature and beauty of wood mean that it can be used purely for its aesthetics, while the same material can also be used in load-bearing construction applications. The weight-to-strength ratio of timbers makes wood suitable for many applications.

AG Biopolymers are typically made by converting starch to sugar (or starting with sugar directly), which is fermented to produce polymer building blocks (monomers) or their precursors. Established plastics such as PE can be made this way, as can relatively new polymers such as PLA. Bioplastics are generally seen as a greener alternative to oil-based plastics.

SC Natural rubber accounts for more than 40% of global rubber use (10 million tonnes). The inherent strength of natural rubber, arising from the regularity of its structure, makes it the material of choice in a wide range of applications, from tyres to engineering products and gloves.

KB All areas of packaging involve natural materials. One example is paper and board, where the main raw material is wood, but other plant life, such as hemp, sisal and straw, could be used where the land or climate is not good. Some of these organic materials have parts that cannot be used for paper, such as sugar beet waste. In this case, by applying clever chemistry, the starch is extracted and converted into oil, which can be turned into plastics.

AM We use 100% pure sheep’s wool in our insulated packaging for temperature sensitive products. Wool is a natural smart fibre that provides a range of unique innate benefits and superior insulation. Wool has a natural crimp, and the outer part of the fibre is made of scales that trap air, making it effective in reducing heat transfer, as air does not conduct or disperse heat well. With wool’s ability to breathe, it absorbs and releases moisture from the air, being hygroscopic, which in turn generates tiny amounts of heat that stabilise temperature changes and create a natural buffering effect. This insulating factor can work both ways, by retaining heat or keeping heat out.

How expensive are the natural materials you work with compared with their synthetic alternatives? Is this a barrier to progress?
GO Timber and timber products can be relatively cheap, for example particleboard is much cheaper than an equivalent synthetic product. However, when a piece of wood is bought for its beauty, the price of the raw timber is often high. This high price can be compounded by the scarcity of the timber.

AG Biopolymers tend to be more expensive due to economies of scale, as production is scaled up to meet demand. Green, or bioderived PE, currently sells for around 30% more than identical oil-derived PE. The higher price can be an obstacle for newer materials such as PLA, although plant-derived plastics suffer less price fluctuation compared to those produced from oil.

SC As a commodity, the price of natural rubber relative to relevant synthetic rubbers varies over time, depending on the balance between supply and demand. Supply has eased in the past two years, and this has been refl ected in the price. While for some products such as tyres, there is some scope for adjusting the relative amounts of natural and synthetic rubber used (and some accommodation is made on the basis of price), there is a limit to the extent that this can be practised. In recent years, there has been concern that the future supply of natural rubber will not be adequate to meet demand.

AM Wool-insulated packaging is competitive and in some instances actually shows a saving over synthetic alternatives. The initial outlay is sometimes slightly more expensive but when transport, storage, quantity of ice packs required, waste management, product damage and spoiled product costs are included in the calculation, wool packaging can show a substantial saving.

Have you explored the use of natural material composites in your field? What possibilities do they open up?
GO Natural material composites have been extensively used in the timber industry throughout history. Plywood, medium-density fibreboard, chipboard, oriented strand board and laminated veneer lumber are all composites used in construction, furniture and other applications.

AG A lot of work has been done on reinforcing plastics and biopolymers with natural fibres such as flax, to expand their range of applications. Progress has been made but there are still technical and commercial obstacles to be overcome. The variability of plant-based fibres needs to be addressed.

SC Natural rubber composite materials are already widely used. The rubber fillers provide additional hardness and toughness, as well as reducing the cost of the product. Blending natural rubber with other rubbers provides characteristics that are not available from single constituent rubbers. Blends have also been developed with plastic materials to produce a composite that is processed like a plastic, but which retains elastic properties.

AM During our research, we have considered using natural material composites. Initial trials have shown that our wool can be combined with other natural materials to enhance the properties of wool. This opens up endless possibilities, creating enormous commercial potential within the packaging sector.  

For more information, email Angela Morris, Chair of IOM3’s Natural Materials Association, angela@thewoolpackagingcomany.com