Chemical Technology May 2016

CORROSION & COATINGS

WACKER’s Burghausen site, with its nearly 10 000 employees, is the largest chemical plant in Bavaria, Germany.

interact with the adhesive during storage. Long-term tests are also undertaken to ensure that the release coating still meets quality requirements after prolonged storage. To determine whether the curing reaction is complete, the coated substrate is placed in solvent, which dissolves out any uncured silicone. The amount of such uncured silicone is then measured analytically. As a result, the amount of platinum required can be determined precisely. Optimising the formulation can therefore reduce platinum consumption by as much as one third. New challenges Technical service engineers measure the coating’s release force electronically with the aid of a peelforce measuring device. Different tests show how the coating behaves at a peel angle of 90 º or 180 º, for example. The test results are illustrated graphically. Lautenschlager believes that, while the test results to date point the way ahead, they are by no means definitive. Release coatings thus require further research, so that shampoo, melons, and other products, will be optimally labelled in the future, too. ■

liners. The properties of silicone release coatings include the following: • Good coverage of the substrate’s surface • Minimal silicone consumption • No matrix breaks at high die-cutting speeds • Smooth, pin-hole free surfaces • Release values that do not change during storage • Ease of processing under widely various production temperatures and speeds • Application and adhesion to different kinds of substrates. At the pilot coater, a 1 to 1,3 µm layer is applied to the backing material and then dried in an airflotation dryer at 100 - 180 °C – depending on the material properties – for 1,2 to 18 seconds. Here, the WACKER experts simulate the customer’s industrial processing conditions exactly. The subsequent use of the release liner is also of great importance. In industrial labelling, a machine applies up to five labels per second to packaging – such as a shampoo bottle. The skill of the laminate manufacturer now lies in finding a compromise in the release force between the label and the release liner so that both matrix peeling and labelling run smoothly. Doublesided adhesive tape poses another challenge for laminate manufacturers. The release liner must feature two different release forces for the two sides, so that the adhesive tape peels off of the underside of the release liner first. This allows the doublesided adhesive tape to cleanly peel off for further processing. Testing with Xrays On a lab bench at the coating centre, a colour test provides information on the level of cover of a coating immediately after it has been applied. Xrays measure the thickness of the applied silicone release layer. After it has cured, the release coating still contains reactive groups that can • Custom controlled-release • Reproducible release force

WACKER expands Engineering Silicones laboratory in Dubai

The Dubai Technical Centre is a highly spe- cialised, applications-focused lab, supporting customers from the Middle East and Africa. The Engineering Silicones Lab is equipped to carry out necessary developments for Silicone Elastomers. The main applications are insula- tor coatings, mould-making, and baking trays.

The lab has ‘state-of-the-art’ mixing equipment for developing low viscosity Silicone Elastomers formulations. It also houses a Spray Chamber (see photo) which is a unique facility to support local customers in the electri- cal industry within the Middle East and Africa region.

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Chemical Technology • May 2016