Tape Tensile Strength + Elongation
ASTM D3759 is used to characterize the breaking strength, elongation, and "F" value of PSA tapes. Tapes are commonly pulled in the tensile mode during application and final usage. The tensile properties are primarily a function of the backing material of the tape. There are a host of different types of backing materials including fiber, foam, metal foil, plastic and vinyl,
Most specialty tapes are made by smaller companies in the converting business. These converters will buy the adhesive from a large manufacturer and apply a transfer tape or backing material for the specific end-use application. Since the backing material greatly affects tensile strength and elongation, converters should test their final products for these characteristics.
Almost all tapes are tested at the same width. The vise grip inserts should be 2x2 inches. Pressure-sensitive tapes that break at relatively low forces can be tested with rubber or flat metal grip faces. If the tape is slightly stronger, a serrated metal grip face may be used.
In some cases, especially with reinforced tapes, a wrap grip must be used in order to properly hold the sample. Wrap grips are also commonly known as ribbon, webbing, or capstan grips. The center cylinder of the wrap fixture must be 100mm in diameter and about 40mm wide.
The wrap grips outlined above are only appropriate when vise grips fail. Pneumatic vise grips may be used as they help with both test preparation speed and repeatability.
All tensile pulls under ASTM D3759 should align along the axis of the stress. A universal joint may be used in order to align everything properly. The wrap grips must also be designed in such a way that the axis is offset, allowing a technician to line up the two grips.
The Ultimate Tensile Strength (UTS) is the peak load that the tape withstands during the pull test. Users may also report UTS as the F value. Elongation can also be taken as a % value.