Green Material Initiatives

As we have noted above one of the areas where companies are keen to promote “greener” cables is in terms of the materials that are used in their production.


Promoting a cable as using more environmentally friendly materials also has the benefit that this also potentially reduces the competition from low tech low cost manufacturers. So called “green” materials may be harder to process, of proprietary formulation, harder to source, and may also need the back up of a large engineering department, so low tech, low cost manufacturers find it harder to produce these cables.

Slide 4 shows three silos covering major cable components including conductors, jacketing and insulation--a primary area of interest for green initiatives, and an “other” category.

Conductors

There is only limited scope to suggest that there are more environmentally friendly conductors than copper or aluminium, but there are some companies out there that are attempting to promote copper clad aluminium (CCA) as a “green” alternative to copper on the basis that its lower weight can potentially have less impact on the environment. However, since it is much harder to recycle compared to pure copper, any potential gain would be more than offset by this lack of recyclability and we do not view CCA as a realistic alternative to copper from an environmental view point. It could be argued that aluminium is a more environmentally friendly material than copper due to its lower weight, but producing aluminium is a very energy intensive process and we do not see any real major developments in terms of alternative conductors to be promoted as fundamentally more environmentally friendly.
 

Fibre

One of the potential areas addressing environmental issues and cost savings with optical fibre is the use of LED-based curing systems used on draw towers to cure the acrylate coating used to protect the core and cladding. The system comprises a UV Lamp and LED curing system that uses high power LEDs with a narrow band of emission that allows for higher yields and reportedly lowers utility costs by as much as 30%-70% for wire & cable applications. The air-cooled design eliminates the need for external cooling or ozone extraction thereby eliminating containment and waste-related costs.

Some manufacturers are making 200?m fibres versus the traditional 250?m +/-5?m. Inking or colouring fibre for identification adds another 3-5?m. In a recent technical paper, thin skin micromodules containing twelve 242?m fibres have a diameter of 1.15mm. Using 200?m fibres, the diameter is reduced to 1.0mm. The smaller diameter fibre permits greater density and also produces significant weight savings.

We have seen claims that fibre optic cables are more environmentally friendly than copper ones as the main raw material to make fibre, silicon, is abundant. However, we do not believe that customers choosing between copper and fibre are going to make this decision on environmental grounds.

Insulation and Jacketing Material

The main focus of companies’ promotion of “greener” cables is based on the use of polymers which are said to offer an advantage over traditional materials. Generally this means promoting alternatives to halogenenated materials, materials using phthalates or ones with heavy metals in. There are also companies offering “greener” alternatives of traditional materials such as PVC, which have reduced acid gas and smoke emission. There are also now alternatives available to replace lead sheaths.

In terms of halogens the main historical uses have been in PVC, FEP or brominated flame retardants, and the alternatives are usually some form of low smoke zero halogen compound (LSOH or LSZH) often based on EVA, or the use of alternative flame retardants such as aluminium trihydrate (ATH). LSOH cables were originally developed for their performance in a fire, but they are now also being marketed as more environmentally friendly in that when they are burnt the emissions are less toxic to the environment. Thus whilst originally LSOH cables were purely seen as an alternative to PVC cables for use in areas such as public buildings where fire was a real hazard to human health, the promotion of them as more environmentally friendly opens up a much larger potential market. It also means that in North America, where fire safety has taken a different path to Europe, this has opened up an alternative way of promoting these types of cable.

The use of Phthalates as plasticisers has been under attack for many years since one of the original compounds, DOP, was classified as a carcinogen. Many companies now use the fact that their products don’t contain phthalates as a way of promoting their green credentials, and there are numerous alternatives available.

Another development has been the introduction of plasticisers made from renewable sources to make a cable “greener”. One example in North America is the collaboration between a chemical and a compounding company. The chemical company provided a bio-plasticizer that was further enhanced and modified to develop a product with a low volatile organic content (VOC) that didn’t smell. PVC typically releases 24%-25% acid gases when burned, whereas an HFFR compound emits less than 0.5% acid gas. The acid gas performance of the greener compound falls in between PVC and HFFR.
This approach is also being explored with the basic polymer itself with for example ethanol based bio-polyethylene being offered at least as a partial replacement to traditional oil based polyethylene. There would seem to be further potential for the cable industry to develop more use of polymers derived from renewable resources.

Gel Compounds

An important component used in optical cables is gel-filling compound that is injected into the tube containing optical fibres as the tube is extruded. Filling gel serves two purposes: 1) It prevents water from contacting the fibres, which would compromise the fibre’s integrity, and 2) it protects the fibre as the cable is bent or flexed during handling and installation, or during temperature cycling once the cable is installed.

Roughly eighty percent of the filling gel material used in cables is petroleum-based, but to meet performance requirements a specialized thixotropic rubber compound is added that accounts for the remainder of the finished product. Thixotropic refers to the gel’s ability to transition from a gel to a liquid-state when there is some shear effect or movement on or at the boundary layer. Once movement or shear effect stops, the rubber additive causes the liquid to revert back to a gel. Gel in a liquid state allows the fibre to move and prevent micro-bending losses that would impair the fibre’s optical performance.

Gels for more specialized cable designs such as optical groundwire (OPGW) that are installed in place of standard earth wires on high voltage power lines contain a more expensive hydrogen-absorbing material that can withstand hydrogen released from the stainless steel or aluminium tubes containing the fibres.
Gel manufacturers are looking at developing a plant-based product using vegetable oils, but there are a number of technical challenges to overcome: 1) Mineral-based oils are non-polar and allow the thixotropic rubber compounds to easily dissolve in the oil-based mixture. Plant-based oils are polar and do not allow the rubber compounds to easily dissolve. 2) Petroleum-based oils are non-nutritive. In other words, they do not act as a food source for algae or other potentially harmful agents. 3) Plant-based oils have a higher acid value that is problematic when they come into contact with tubes, fibres or matrix material, and 4) a green product using plant-based oils is more expensive as there is insufficient scale to compete against cheaper petroleum-based products.

The polarity of the plant-based oil remains a significant hurdle and will need to be resolved before a greener filling compound can be commercialized. It’s possible that gels with plant-based oil may gain some market acceptance in advanced economies, but likely would not be as readily accepted in emerging markets due to higher cost.

Some end-users prefer totally dry cables that rely on super-absorbent polymers used in yarn or tape products as an alternative to using filling gel. Another trend is the growing acceptance of cables with reduced diameters that exploit the availability of a new family of bend-optimized fibres that eliminates the negative effects of micro bends.

During the production process and also during a cable’s subsequent life, the polymers used in insulation and sheathing often give off gasses. For example when a power cable is insulated with XLPE the production process generates gasses that must be allowed to escape from the insulation. When a cable is installed there will also be potentially some emissions of gas during the lifetime of the cable and some manufacturers are offering alternative cables which are classed as more environmentally friendly because they use materials which have lower emissions in production and during the cables installed life.