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PVC BANNERs - Controlling
Plasticiser Migration Summer has arrived, and as
the days get warmer, the technical phone calls increase with questions
concerning the performance of UV inks and vinyl on PVC banner and static cling
substrates. It is not uncommon to hear that the
inks "have changed" and the same ink that used to be glossy and dry
now appears matt and tacky or wet. The problem is not that the ink or vinyl has
changed, it's that the warmer weather conditions are causing changes to the
substrates. Most
plastic materials contain plasticisers to make them flexible.
While these plasticisers make the material softer and more flexible, they
also can cause screen, digital printers and vinyl applicators many difficulties. Plasticisers
migrate to the surface of the material and change the surface to which the ink
or vinyl must adhere to.
When the material is exposed to higher temperatures, the migration process
occurs more quickly. Since static cling and PVC banner materials contain high
levels of plasticisers, storing them in a hot warehouse, transporting in a hot
truck, or curing through a hot unit will quickly cause plasticisers to migrate
to the substrate surface, potentially causing ink adhesion and/or blocking
problems. Some PVC banner manufacturers now
offer top-coated vinyl banner materials which prevent any plasticiser from
contaminating the surface of the material. This top-coating eliminates the
plasticiser migration problems. Printers and Vinyl Applicators
should weigh the higher material costs against the potential production down
time in making their substrate decision. As a rule of thumb, PVC banners should only be used
for short-term outdoor applications such as once off promotions. With longer
term signage use Flexface (used on light boxes) which has a top coating to
prevent plasticiser migration.
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