Rapid plasma treatment – Interior of DPC 403 plasma system from Delta Engineering, a four-reactor unit typically used for containers from as small as 10ml up to 2 litres

Delta Engineering’s plasma treatment systems offer efficiency, cost advantages

WRAPETFILL, the integrated consultancy/machinery/material supply business, has noticed some new opportunities for the plasma treatment systems from Delta Engineering of Belgium, which it represents. Delta’s plasma systems offer improved efficiency with reduced costs compared to technology used in South Africa to date.

Delta Engineering is primarily a downstream automation company for container producers, offering standard automation equipment such as conveyors, leak testers, palletisers, baggers, lost head trimmers and check-weighers. It has, more recently, begun to supply plasma coating machines, in which area it partners with Isytech of France, a global plasma coating specialist.

Isytech has recorded some noteworthy achievements in plasma treatment, including amorphous carbon plasma coating for PET bottles, where it developed the Actis system for Sidel in 1998 to produce gas barriers for PET bottles. Applications were however limited to high-output projects. Then in 2005 it developed and patented amorphous fluorinated carbon barrier coating technology for HDPE agrochemical packaging. In 2007, the first plasma coater was installed in an extrusion blow moulding factory in France, which machine is still in production today.

After several years of joint development, Delta launched a range of fully automated plasma coaters during an open house event at its plant in Romania in 2019. Customers from across the globe attended, including several from South Africa.

What is plasma treatment?

Plasma enhanced chemical vapour deposition (PECVD) uses electrical discharge in low vacuum pressure conditions to decompose a gas and create a thin coating layer on the inside wall of the product in the reactor. It is an environmentally friendly way to create fully recyclable coated products where different physical and/or chemical properties are achieved as desired, depending on the material and the plasma gas used.

Different properties can be obtained, including modification of the surface tension for better sliding, adhesion or wettability; an improvement of the barrier in different applications, to prevent migration or permeation. Multilayer technology is used in some containers to achieve the latter features, namely good barrier properties, but these containers cannot be recycled because of the different layers, which can’t be separated.

The Delta Engineering plasma coaters have the ability to apply an amorphous carbon coating to PET bottles and also an amorphous fluorinated carbon coating to HDPE bottles.

This process is often used on PET bottles and increases the oxygen barrier to about 30 times. Water vapour and CO2 barrier are improved as well.

Environmentally friendly gasses

The Delta machines use only environmentally friendly gasses, including Argon, which is an inert noble# gas. The toxicity of acetylene is negligible and widely used in the welding industry. It also uses the new environmentally friendly HCF gasses, with a low GWP (global warming potential) value and well-known in the world of refrigeration.

Furthermore, the gasses are largely consumed during the process, reducing the exhaust quantity to a minimum. The remainder could be captured with an active carbon filter, should local legislation require this.

Other advantages

Plasma coaters primarily replace fluorination of HDPE containers. According to Henk de Klerk of Wrapetfill, batch fluorination is dangerous and expensive with significant costs associated with the transporting to and storing of empty containers at fluorination sites.

“Plasma coaters allow converters to coat their HDPE bottles or drums in-line with extrusion blow moulders or off-line, thereby eliminating transport and warehousing costs as well as the high cost of fluorination. Plasma coating costs a fraction of fluorination and the gasses required for plasma coating are widely used and available in South Africa,” he added.

Delta Engineering has already integrated its range of plasma coating machines into several industrial applications to achieve different outcomes, including treating bottles (inside) without adding gasses in order to obtain different physical properties/surface structures such as crosslinking, sterilisation, surface treatment for medical applications, bonding and plasma carbon deposition.

Leadership in plasma technology

Delta’s focus on the plasma technology over the past few years has already achieved significant results. It has shown that its systems can allow a plasma coated mono-layer container to perform as well or better than a multi-layer or fluorinated equivalent.

Applications are primarily in food, non-food and agrochemical containers, or wherever there is a need for a solvent barrier. The difference in cost reduction is high, added De Klerk.

NOTE: The Noble or inert Gases are the Group 8A elements of the periodic table that include helium, neon, argon, krypton, xenon and radon. The name comes from the fact that these elements are virtually unreactive towards other elements or compounds.