| 1. YUPO sheet surface is primarily polypropylene with some exposed calcium carbonate resulting in low surface energy (30 - 33 dynes/cm as measured by the contact angle method. This surface is treated with a mixture of proprietary chemicals to raise surface energy and improve printability.
2. Damage or inadvertent alteration of the surface treatment can interfere with ink transfer and adhesion. Flame or corona priming, static discharge, fumes from drying ink, and excessive moisture levels from the dampening system or aqueous coatings all will affect printing performance. Extended storage (two or more years) may result in deterioration of the dyne levels, and therefore surface printing properties.
3. If surface conditions are compromised during the press run, application of a primer coating or varnish often will level out surface energy and restore uniform printability. Coatings can be applied in line or in an additional press pass.
4. YUPO generally has a lower friction coefficient than uncoated paper. Based on the testing procedure used, the coefficient measures between .45 and .55, and the coefficient of sliding (kinetic) friction measures between .35 and .40. Printed sheets will usually have higher coefficients of friction and be more resistant to sliding. |
|
