Clean inside and out

Even brand new flexible bags can contain contaminants that damage sensitive products, including particulates and leachates. Sectors such as the space industry, pharmaceuticals, medical devices and electronics require purpose-made ultra clean packaging. Zeal Clean Supplies has developed a way of producing bags with a particulate count in single figures. Low density polyethylene is produced on site and the final packaging is manufactured inside a Class 1,000 cleanroom.

Zeal puts no additives in its ultra clean polyethylene to avoid potential leaching or contamination

It is not always recognised that brand new flexible bags can contain contaminants that damage sensitive products. That is why at Zeal Clean Supplies the bags are made to meet the needs of the most demanding of customers – including those going to explore Mars.

Success of the likes of NASA's twin robots, the Exploration Rovers, which have been roaming around Mars, depends on many sophisticated technologies and very careful assembly of the component parts. Such projects cost millions of dollars and involve many man-hours. Once in space, there is little chance of retrieving the robot if something goes wrong, so failure is to be avoided at all cost.

It is not surprising that NASA has some of the most demanding requirements when it comes to cleanliness of components: one speck of dust could jeopardise a whole mission. As a result, NASA works to exacting standards, such as those of the US military (MIL-STD-1246C) for product cleanliness levels and contamination control. Such standards apply not only to the components that make up the robot and the assembly environments, but also to the packaging that transports the components for use in NASA projects.

To package such components in ordinary plastic bags could spell disaster. Most packaging will come with particulates that can interfere with the performance of highly sensitive components. Other problems could be caused by the ingress of moisture or ambient gases that could affect electronic components.

The success of such components will be assured only if they are supplied in purpose-made ultra clean packaging.

It is not only NASA that relies on such ultra clean packaging; sectors such as pharmaceuticals, medical devices and electronics also require specialised bags.

Zeal Clean Supplies began life in the 1990s producing specialised flexible film bags for the pharmaceuticals market – a sector demanding very high cleanliness levels and contamination control. To ensure the company could offer the best products within the competitive packaging market, Zeal set about inventing a way of producing bags with a particularly high level of cleanliness. This meant instead of particulate counts in the thousands, the company developed a process that produces bags with a particulate count in single figures – a proposition that only a handful of suppliers around the world can offer.

Zeal set about inventing a way of producing bags with a particularly high level of cleanliness

Building on its initial success, the company decided to move into a larger facility in south west London. The larger premises gave the company a multi-storey layout that enabled the low density polyethylene to be produced on site and the final packaging to be produced inside a Class 1,000 cleanroom.

Conventional packaging equipment would emit too much contamination for a Class 1,000 cleanroom, so Zeal had to develop both processes and equipment that would work well in the cleanroom. The traditional blown film extrusion process was redesigned and is carried out under special conditions to ensure the material produced is ultra clean.

Avoiding contaminants

There are two factors with packaging that can affect contaminant sensitive products:

  • particulates in the bag, which for a normal bag can be in the 8000 per cm2 range.
  • the chemical make-up of the raw material used to make the flexible film.

Polyethylene uses many additives to aid its manufacture and to make the bags slippery and easy to open. These additives can leach out and contaminate certain products.

To verify the cleanliness of the bags the company had them tested at independent laboratories, including the Fraunhofer Institute in Germany.

The Institute tested for cleanliness using liquid particle testing, and showed that the bags can typically achieve particle counts of below 20 in the >0.30µm range and below 10 in the 0.50–1.00µm range. The Institute also tested for outgassing of the material and for leaching using ion chromatography. In addition, the company carries out its own routine tests.

Today, in addition to ultra clean polyethylene, the company produces ultra clear high barrier packaging and a selection of high barrier foil packaging for transferring products ranging from pharmaceuticals to food, electronics and semicon to aerospace, and hospital fluids to medical devices.

The company has also branched out into antistatic bags. These are important in some food and pharmaceutical production environments, such as where bulk powders are handled and the slightest electrostatic spark from the plastic bag could set off an explosion.

Antistatic bags have traditionally used additives that can migrate from the base material to the surface where they will react with ambient moisture to create a dissipative chain. This could, however, contaminate or corrode sensitive materials that come into contact with it. Zeal has adopted a new generation of additives that create an embedded, non-degradable dissipative chain, thus obviating contamination or corrosion.

Other customers, such as the semicon industries and the producers of the photovoltaic cells installed in high performance solar panels used in outer space, have their own special requirements concerning dust, volatiles, gases and static. In this respect, Zeal is able to meet the needs of International Disk Drive Equipment and Materials Association (IDEMA) standards for packaging.

The company also maintains a batch control process that enables it to trace batches of goods down to 100 piece lots. For each lot, it maintains details of raw materials batch, machinery used, operations involved, time, shift and date of production.

Instead of particulate counts in the thousands, the company produces bags with a particulate count in single figures

Other industries have many special requirements that are less demanding than those of NASA or IDEMA but nevertheless require a controlled environment. For example, Zeal makes bags for veterinary products made in a foil pouch, as well as the specialised cement used for hip joint replacements, which needs to be packaged in a controlled environment using packaging materials with a non-leaching ink.

The company has now had 15 years of expertise in offering various industries ultra clean bags, but despite this progress Zeal managing director Harry More-Gordon says there is still a need to educate the customer as to why they should use such packaging.

“There is a misconception that if you have a class 1,000 cleanroom the products handled in that cleanroom are also to class 1,000, but this is not the case,” he says. “For example, some companies make bags in a cleanroom but they use a polyethylene that has been made miles away from the site. In reality, the products handled in the cleanroom are only as clean as the material that you start with.”