An improved paperboard has been bulk enhanced by retaining a substantial portion
of bulk-enhanced additives including expandable microspheres in a suitable distribution
within the paperboard. The cellulosic paperboard web has an overall fiber weight
(w) of at least 40 lbs. per 3000 square feet and, at a fiber density of 3, 4.5,
6.5, 7, 8.3, and 9 pounds per 3000 square foot ream at a fiberboard thickness of
0.001 inches, has a GM Taber stiffness of at least about 0.00246 w2.63 grams-centimeter/fiber
mat density1.63, and a GM tensile stiffness of at least about 615+13.18
w pounds per inch. The high retention of the bulk enhancing additives is believed
to result from the incorporation of suitable retention aids. The resulting paperboard
has better GM Taber stiffness values and GM tensile stiffness than prior art paperboards.
The paperboard also has increased strain to failure and is able to be formed into
suitable paperboard containers without loss of integrity. The resulting containers
have increased hold times when they contain hot or cold food or drink.
