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Nylon is a thermoplastic used in numerous industries. Thermoplastics melt when heated, allowing them to be reshaped. When they cool down, they re-harden in the new shape.
Pipe-cleaning brush bristles made using nylon are soft and flexible while still being resistant to damage by fungi, abrasion and many chemicals. They are suitable to clean and process wood, plastic and metal.
In chemistry, nylon is known as a man-made aliphatic polyamide. You may see this abbreviated to ‘PA.’ PA, polyamide and nylon are all the same material.
Polypropylene is also a thermoplastic. It has similar properties to nylon but is cheaper and easier to produce.
It is resistant to many chemicals and lasts a long time if it is looked after correctly.
Exposure to heat or ultraviolet light causes it to degrade so it is not suitable to clean hot surfaces.
Polypropylene and nylon can be mixed with a gritty material to make flexible bristles which are abrasive along the whole of their length, allowing efficient cleaning right into all recesses in the part to be cleaned.
Aluminium oxide or silicon carbide can be used as the abrasive material because both are very hard, abrasive, crystalline materials.
The plastic makes up the main structure of the bristle while the abrasive material (known as ‘grit’) is set into it. This means the grit size can be varied. The larger the size of the grit, the rougher the surface of the bristle.
Grit size is indicated by a number in the product description. Most UK products use the Federation of European Producers of Abrasives (FEPA) standard which is sometimes indicated by a ‘K’ before the number. The lower the number, the larger the size of the grit.
Abrasive filaments can be round or flat. Flat filaments have a larger surface area so are more abrasive, last a long time and are useful for removing lots of material from the surface of your pipe.
Round filaments are the most common and are more flexible than flat filaments.
Stainless steel is an alloy (a material made from two or more chemical elements) containing mainly iron. Different amounts of chromium, silicon, nickel, carbon, nitrogen and manganese are added to the iron to change how it can be used.
Adding chromium increases the steel’s resistance to rusting while adding more nitrogen allows the steel to be made into wire bristles without breaking. There are 57 standard alloys of stainless steel. They will all have a chromium content of 12%-20%.
Stainless steel bristles are tough, abrasive and resistant to high temperatures so can be used on hot objects or in a power tool.
They can also be used safely when wet and are resistant to some acids and bleach.
If you want to clean a stainless steel pipe or fitting, it is essential a non-ferrous metal (a metal that doesn’t contain iron) or a stainless steel brush is used. Plastic and brass bristles would be suitable. Ferrous metal bristles can leave behind tiny pieces of bristle on the surface of the pipe, which can lead to corrosion.
Carbon steel is an alloy of mainly iron and carbon.
Increasing the amount of carbon makes the steel harder and stronger but less easy to form into bristles.
Tempering, a process of heating and slowly cooling, softens high carbon steel allowing it to be formed into wire for bristles.
Carbon steel is cheaper to produce than other metals but still makes quality, long-lasting, stiff bristles for general cleaning, deburring and preparation of the surface of most metals.
Brass is an alloy of copper and zinc.
Adding a small amount of aluminium makes brass easier to make into bristles and less likely to corrode.
Brass bristles are softer than stainless steel and are designed to be used on non-ferrous metals.
Brass bristles can be used with water and mild bleach.
Titanium is a lightweight, strong metal which doesn’t corrode in salt water, chlorine or strong acid.
It is harder to find on the market than the other metals but, for the same reason as stainless steel (see above), it is essential that titanium objects are cleaned with pipe-cleaning brushes that have titanium bristles to prevent galvanic corrosion. Galvanic corrosion occurs when two metals of opposite electrical charges touch each other.
Although cheaper-to-make synthetic fibres have mostly replaced natural fibre bristles, they are still available.
Bristles can be made from plants such as palms or agave (a plant unique to Mexico). They are suitable for working on wood surfaces.
Tampico forms very fine, soft to medium-stiff bristles that polish surfaces, absorb and release water very easily and can withstand temperature extremes and acids.
Tampico fibre does not collect dust and lasts for a long time without becoming brittle.
It is quite expensive and is often replaced with the cheaper polypropylene which can be made a similar stiffness but does not have the same water absorbing properties (see above).
Animal fibres, such as horsehair, can also be used to make pipe-cleaning brushes.
Horse hair, taken from the tail or mane, creates a soft bristle for gentle dry polishing or dust removal. It is anti-static so it doesn’t collect dust. It will become damaged in acid or alkaline conditions.
These days nylon is more commonly used but horsehair is the more gentle bristle.