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ACCURATELY PREDICTING HIGH SPEED UNWIND

Debbie Chrzanowski
Manager Product Development & Improvement
Intertape Polymer Group, Marysville, MI

We are all familiar with customer complaints of tape with low adhesion. Upon closer examination, the customer assumption of low adhesion is sometimes a function of low roll unwind force. It is commonly known that most consumers assume that tape, which dispenses easily, or with low force, will not adhere properly. Those of us in the tape industry acknowledge the misunderstanding and, when given the chance, educate the consumer on the separate mechanics of tape adhesion and roll unwind force, or ease of dispensing.

Most pressure-sensitive tapes are "self-wound", that is, wound on themselves, without the benefit of a release liner. Therefore, the adhesive is in intimate contact with the tape's backing. When the tape is unwound, the adhesive must remain on the side to which it was applied. Thus, unwind force should be low, so as not to disturb the adhesive/backing interface. However, if the unwind is too low, the tape may have an unacceptably low adhesion to its own backing which will result in flagging when overlapped or applied to itself.

It would be ideal to supply the consumer with the same product dispensing performance (unwind condition) at all times. However, if a relationship between common in-process measurables and unwind force could be developed, the opportunity for better consistency and control would then exist.

Accurately predicting high speed unwind (HSUW) with in-process testing during the manufacturing process has always been a challenge. Only when the product has been converted into finished rolls do we know the actual unwind characteristics.

A new test method has been designed that, when used in conjunction with predetermined converting controls, will provide the opportunity to produce PSA tape products with consistent roll-toroll HSUW values.

There were 2 significant factors identified in this work, HSAB (High Speed Adhesion to Backing) and Roll Hardness, which had high correlation to HSUW. HSUW along with these two factors will be described in detail.