Why is semichemical pulp often used for corrugating medium in cardboard boxes?

Semichemical pulp is primarily used for corrugating medium—the fluted interior layer of corrugated boxboard—because it provides the essential properties of stiffness and adequate strength required for heavy-duty containers.1

In the papermaking process, semichemical pulp is produced by treating wood chips with chemical solutions under milder conditions than those used for full chemical pulping, followed by mechanical refining. This process results in a high fiber yield that offers a balance of chemical and strength characteristics intermediate between groundwood and full chemical pulps. While straw pulp was historically used for this purpose, it has largely been replaced by semichemical hardwood pulp due to these superior structural qualities.12