Page 644 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Polymer Technology 607

The 3M company has been instrumental in the discovery and improvement of many tapes. The
fi rst pressure-sensitive adhesive tape was discovered in 1925. During the depression an increasing
number of items were taped together rather than discarded. Double-sided tape was used to hold
together layers of metal skins to aircraft frames. But what we now know as Scotch tape was discov-
ered by a young 3M engineer Richard Drew in 1930. Then 3M was a small sand paper manufactur-
ing company. Two toned automobiles were becoming popular. Painters would mask one section
while painting the second color. Parts of the first color were often ripped off when the masking

material, typically simply newsprint, was removed. Drew noticed this and worked for the next
2 years developing pressure-sensitive glue that he applied to the edges of one side of some crepe
paper. While it could be easily removed by the painters, it also kept falling off. The story goes that
one of the painters told a 3M representative to tell his “Scotch” bosses (an indication that 3M was
cheap) to put adhesive all over the tape and not just on the edges. They did and the name stuck as
did the tape. Today, 3M has hundreds of tapes sold under the “Scotch Tape” name.
Drew was then asked to develop a waterproof tape that could seal insulation panels for refriger-
ated railroad cars. He and fellow workers developed the clear cellophane-backed tape that is famil-
iar today but today with a variety of different formulations.
Post-It Notes is another of the host of 3M tapes. It was discovered by Art Fry using an adhesive
developed by a fellow coworker Spenser Silver with the help of Jesse Kopes in 1968. The adhesive
was simply an acrylic adhesive similar to that used for many of the more permanent tape adhesives,
but diluted with nonadhesive material. Silver promoted his “low-tack” reusable pressure-sensitive
adhesive for 5 years within the 3M origination but with little success. Fry attended one of the sales
pitches by Silver and used the formula to anchor his bookmark in his hymnbook. 3M commer-
cialized the product in 1977 but customers would not try this new product. After giving away free
samples to the residents of Boise, Idaho they found that people liked it so a new promotion was tried
and the rest is history. By 2003, 3M came out with “super” Post-It Notes that were simply the old
formula with less nonactive filler giving the Post-In Notes better adhesion.

Self-adhesive tapes generally consist of four thin layers as pictured in Figure 18.17. The fl exible
backing is often about 50–100 μm thick and can be composed of a variety of materials, including
polyethylene, PP, paper, cloth, foil, vinyl, or foam.
Backings are coated on both sides. The release coating is often a poly(vinyl carbamate) (18.5) and
it prevents the tape from adhering with itself. The other side of the backing is coated with a primer
that attaches the backing and adhesive material. The major component of the adhesive is poly-
meric. For instance, styrene block copolymers are often employed as the adhesive for packaging and
double-sided tapes while offi ce tapes often employ water-based acrylics similar to those employed
in some paints. Silicon adhesives are often used for medical tapes.

Release Coat
Backing
Primer Coat
Adhesive

FIGURE 18.17 Components of a typical pressure-sensitive tape.

R
R

O NH 2 (18.5)

O

9/14/2010 3:43:44 PM
K10478.indb 607
K10478.indb 607 9/14/2010 3:43:44 PM