In 1907, Belgian chemist, Dr Leo Hendrik Baekeland first invented plastic materials, with his discovery of the first thermosetting phenolic resin compound. This was used to manufacture the first plastic products under the brand name of ‘Bakelite’. The best known examples of Bakelite, in UK, were the original telephone handsets and motor car distributor caps – distinctive for being hard, smooth and glossy in the only available dark brown colour.
The history of plastic developments has since been long and multi-facetted, from the manufacture of cheap children’s toys, to the heat resistant nose cone on the NASA Space Shuttle. In fact, there are now more varieties of the different types of plastic materials – than there are species of timber, with which we are generally more familiar.
For example, Timber varieties have their own unique characteristics and benefits, which justify their individual usefulness. For example, softwoods are generally cheaper and more sustainable but do not last as long as hardwoods, externally, in our maritime climate but they perform well indoors. Similarly, the Meranti and Luan species of hardwood are far less durable than the oily Teaks and resilient Iroko varieties. However, Douglas Fir is a slow grown softwood with a solid reputation for external durability, whilst Balsawood is a species of hardwood that would hardly stand the test of time and strength in any climate! So it is important to understand the differences and to know which variety is ideal for any particular application.
Plastics are similar, requiring a good understanding of their different capabilities in order to select the right type for any given application. All plastics share some common features, with the main one being that they are impervious to water. This is a useful start, especially for external applications – and establishes the first and compelling advantage over timber. Two common forms used in the construction industry are ‘thermo-plastics’ and ‘thermo-sets’.
Thermo-plastics, like PVC, are cured by heat, which enables them to be softened and re-formed like candle wax, by the subsequent re-application of heat, causing them to melt if sufficient heat is applied. They are dimensionally volatile under changing temperatures, having a high coefficient of expansion. Thermosetting resins, however, are chemically cured, thus their performance characteristics are locked in, or ‘set’, during manufacture, so no amount of heat can reverse the process, or subsequently mould or melt them. Thus, they provide a far more reliable and durable compound for external applications where significant temperature changes are experienced and dimensional stability is required.
As well as different resin systems having their own unique attributes – significant development has been undertaken to develop high performance hybrids by adding other components to create new ‘super-strength’ compounds, called plastic ‘composites’, or ‘composite materials’. Such composites, take the strong and reliable ‘thermosetting’ resin system and add glass or carbon fibres into the mix, to act as a reinforcing binding agent to spread any stress loading and give considerable additional strength to the end product. The resultant composites considerably exceed the strength to weight ratio of steel and aluminium – and still, of course, remain impervious to water.
These astonishingly strong and durable composite materials are called FRPs (Fibre Reinforced Polymers) better known as ‘GRP’, ‘Fibreglass’, ‘carbon-fibre’ and ‘graphite’ – and are invariably found in the best sports equipment (skis, golf clubs, tennis racquets, fishing rods, etc). The motor and aeronautical industries have also embraced this technology which provides great strength with lightness of weight, hence their use for the bodies and disc brakes of all Formula 1 racing and many sports cars, as well as for an impressive 94% of the wings and fuselage of the new Boeing 787, scheduled for introduction this year (2010).
Building products, which have successfully used this technology in UK, have been, most notably, the GRP residential ‘composite’ door, introduced in 1987 and which now dominates social housing – and a variety of moulded roof canopy structures. These products use, either, high pressure flat pressing for door skins, or, hand lay-up moulded assembly for the manufacture of more complex shapes. This was the extent of the manufacturing options until more recently, although a continuous manufacturing process has long been sought after, to produce unlimited lengths of shaped profiles that can be cut to any dimension and thus minimise wastage. This ‘pultrusion’ process was developed in North America, in the 1980′s and enabled the availability of GRP fibreglass for a whole new variety of building applications – including window frames.
Windows: For the past 30 years there has been a struggle to establish the optimum window material between, timber, PVC and aluminium. PVC currently dominates the housing market, whilst aluminium dominates commercial, ‘non-housing’ applications. Timber encroaches onto the housing market, too but the inevitable regular and costly maintenance makes it impractical for long term, whole life cost sensitive applications, despite improvements in preservative treatments (which tend to have poor sustainability credentials) and water based finishes.
However, the rapidly increasing awareness of climate change and sustainability has made specifiers re-assess these incumbent materials and have often found them wanting against this new environmental analysis. PVC, for example is condemned by Greenpeace and GHA (The Good Homes Alliance), for its high levels of human toxicity and CO2 emissions, released during manufacture, in use and upon disposal; whilst aluminium is criticised for its high embodied energy during manufacture and its very low thermal insulation. Also, the most commonly used Mahogany timbers can only grow in the Tropical rainforests, which, due to excessive deforestation, is reducing the Earth’s capability to heal itself from the effects of rising CO2 levels, since they absorb CO2 and generate oxygen in return, through photosynthesis. The Rainforests are not called ‘the Lungs of the World’ for nothing!
So it is – that at the very time these product shortcomings have been identified – a solution appears to have arrived!
GRP Fibreglass suffers from none of the above limitations which afflict other materials and is, therefore, ideally suitable for window applications, whether for commercial projects or for housing. The material is made 50% from sand, the most abundant substance on the planet, which has an inherently low thermal conductance and therefore generates lower U values than other materials can achieve. Thus U values of 0.9 W/M2K across the whole window is possible. Furthermore, the extreme strength, durability and immunity from the climate provides a maintenance-free life expectancy of 50 – 75 years, which dwarfs all alternative window materials – and creates a spectacularly good ‘best value’ comparison against all-comers, including the cheapest, softwood – and after only 16 years in that case.
Pultruded GRP is 65% glass, which reduces thermal conductance and expansion, close to that of glass itself, thus reducing friction and wear between sealed units and frames. In addition, up to 33% of the glass comes from a recycled source, scoring additional points on any BREEAM or Code for Sustainable Homes assessment. The frames can also be recycled upon disposal by grinding down for use as filler in concrete to improve the binding agent of the mix.
It is the sheer strength of pultruded GRP that astounds most new comers, having twice the strength to weight ratio of steel and five times that of reinforced concrete. Fact! Aluminium of course is much softer than either steel or GRP – and PVC is weaker still, despite its essential internal metal reinforcement, which ironically creates a cold bridge to further lower its attainable U values.
In practice, GRP scores well over all other window materials, too, being the only material which provides zero maintenance and yet which can be either repaired or repainted if damaged, at any stage of its life, without triggering the need for any future maintenance. By comparison, aluminium and PVC cannot be repaired or recoated commercially and so their appearance will gradually diminish until it becomes unacceptable, when the only way to correct it is for it to be changed completely. For this reason the service lives of aluminium and PVC windows are predicted by independents to be less than half that of GRP. Timber, of course, requires regular and expensive maintenance throughout its life, which is enormously unsustainable and makes it the most expensive whole life cost option of them all, typically twice the cost of GRP over 30 years.
New innovative materials are always greeted with caution in the Building Industry and GRP is no exception! However, the benefits to those who have had the confidence to investigate it and use it first-hand, are immense and have been proven many times over. So, thank you to Dr Baekerland, who would be delighted at how his early discovery has been developed and, today, able to come to the aid of those seeking to reduce carbon emissions and thus help to slow the rate of climate change.
Post time: 06-07-2017