A Study of Loblolly Pine Growth Increments—Part IV. Papermaking Properties

Loblolly pine growth increments were divided into five fractions: two earlywood, a transition, and two latewood growth zones. Each fraction was kraft digested to four different time schedules, Valley beaten, made into handsheets, and tested for tear, tensile strength, and bulk properties. Differences in these physical properties were related to inherent characteristics of individual fibers. Tear factor was highly correlated with the relative position of wood from which the pulps were prepared, with respect to the growth ring. Earlywood pulps produced sheets of low tear values, whereas latewood pulps produced high tear factors. Variation in specific volume, or bulk, of handsheets showed trends similar to those of tear factor. However, intra-incrememt variation in tensile strength of handsheets was the opposite of those in tear and bulk. For all three physical characteristics of hand-sheets, most of the variations could be accounted for by relative position of tracheids within the growth rings of loblolly pine. The extent of digestion and refining of the pulps affected tear and bulk adversely but improved tensile strength of handsheets. However, by far the most important single variable affecting sheet properties was inherent intra-increment tracheid morphology.