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Product category: Materials processing and testing
News Release from: Tantec | Subject: Corona treatment
Edited by the Engineeringtalk Editorial Team on 07 August 2006

Corona treatment gets plastic pipes
prepared

Plastic piping has low surface energy, which makes it difficult for inks, coatings and foams to adhere to the surface - a problem that can be solved by corona treatment.

Plastic piping is used in a wide variety of applications and across a range of different industries Its three main types, PE, PEX or PP, share one basic characteristic - low surface energy, which makes it difficult for inks, coatings and foams to adhere to the surface

Corona treatment by Tantec solves this problem by increased surface energy and improving adhesion.

PE, PEX and PP display a wide range of properties that make plastic piping systems the ideal choice for anything from pressured water mains and gravity sewer systems to indoor heating systems and a continuously growing number of new markets and uses.

Plastic pipes are used in: water pipes, gas pipes, sewer pipes, cable protection or conduit, heating and cooling pipes, and industrial systems.

Plastic pipes have numerous advantages over regular steel pipes, such as being lightweight, strong, flexible, cost-effective and durable.

Their resistance to many ordinary chemicals such as acids, bases, salts, and oxidants make them suitable for a wide range of special applications.

They are easy to install and require minimum maintenance, and offer long-term resistance to a variety of service conditions such as abrasion, temperature, ground movement, bending, weathering, internal pressure etc Improved product durability has lead to a decline in wettability - a surface's ability to adhere to liquids such as inks and other coatings.

This decline in adhesive power has lead to the development of new and innovative methods to improve wettability.

Tantec's corona treatment systems provide substantial flexibility in the treatment of a wide variety of materials used in the pipe industry, and is a key method in solving adhesion problems.

Tantec's specialised corona treatment systems treat pipes across their complete length with superior one-pass coverage and consistency.

Corona treatment chemically roughens the surface, allowing it to 'grab onto' the ink, foam or coating being applied to the plastic pipe.

The resulting chemical bond that occurs with the pipe's surface is stronger than a simple mechanical bond.

Pipes have to fulfil a long list of requirements before they are put into the ground.

One requirement, for example, is that each pipe segment has to be labelled with information such as country of origin, manufacturer, material, date, dangerous hazards etc.

This information has to be applied in such a way that it remains clearly visible even after many years in the ground.

While this information is usually printed onto the pipes, materials such as PE, PEX and PP have low surface energy, resulting in poor adhesion.

Combine this with rough conditions such as abrasion, temperature fluctuations, ground movement, bending, weathering and internal pressure the information does not stick to the surface for long.

Before information can be printed on a plastic pipe, its surface must be treated to ensure proper adhesion between the ink and the pipe's surface.

Corona surface treatment is a unique and cost-effective method, which creates optimum adhesion by increasing the surface energy of the substrate to just above that of the material to be applied.

The SpotTec is an inline pretreatment system designed specifically by Tantec to be easily integrated into new or existing pipe production lines.

The frequency by which SpotTec treats pipes depends on the size, thickness and extrusion speed of the pipe.

While thin pipes are extruded at high speeds (300-600m/min), larger, thicker pipes are extruded at very low speeds (0.5-2m/min).

SpotTec's generator frequency and electrode types vary according to the surface to be treated: high speed extrusion requires a higher frequency generator, while at lower speeds the generator runs at low frequencies.

A high frequency system includes: high-frequency generator, high-voltage transformer, air-cooled electrodes, ozone filter and customised stand-alone or bench-top treatment station.

Treating the inside of pipes is also often necessary to improve adhesion.

District heating pipes require surface treatment to ensure that the hard foam insulation used adheres to the pipe's interior.

District heating pipes are insulated using a hard polyurethane foam (PUR) made of polyol and isocyanate, which is discharged into the space between the inner steel pipe and the PE outer shell, completely filling the space.

Treating the inside of the pipe is crucial to improve adhesion and prevent air pockets from forming, which in turn causes condensation and deterioration of the foam over time.

PipeTec corona treatment helps solve this problem by improving the bonding properties of the inside of the PE outer shell to the PUR.

PipeTec is usually installed between the extruder and the saw that cuts the pipes into 6m sections and its extrusion varies in speed for large pipes (1000-1200cm diameter) 0.5-10m/min.

Corona treatment is very effective and lasts for several months, which means final processing does not need to occur immediately.

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