Dynamic Relative Humidity Creep Decay Basics in Corrugated Board
Dynamic relative humidity accelerates corrugated compression creep via mechano-sorptive softening, requiring environmental safety factor multipliers up to 2.5.
TAPPI T843
Standard Specification
Standard testing protocols for packaging medium quantify edgewise compressive strength on laboratory-fluted specimens held in rigid lateral clamps. Designated as TAPPI T843, this procedure determines fluted edge crush resistance across fluted paper strips. The method isolates intrinsic medium stiffness without attached linerboards.
Structural thresholds stop applying when paperboard basis weight exceeds commercial containerboard ranges.
Specimen Mechanics
Testing fixtures utilize slotted rigid metal plates to support fluted medium specimens during uniaxial vertical compression. Compliance with TAPPI T843 requires compressing a lab-fluted strip of corrugating medium between parallel platens moving at a constant displacement rate. The metal supports prevent premature macrobuckling of the flutes, compelling the paper cell wall structure to withstand compressive load up to ultimate yield.
Results register peak force per unit length in kilonewtons per metre. High moisture levels in conditioning rooms reduce recorded values by softening inter-fibre bonds.
Converting Assessment
Containerboard mills and boxmakers utilize these compressive metrics to verify corrugating medium quality prior to corrugator processing. Values derived from TAPPI T843 correlate with finished corrugated board edge crush performance and final box compression capacity. Recycled fluting and semichemical pulp mediums must maintain strict crush ratings to prevent flute leaning within high-speed single facers.
Specimen preparation errors, including temperature variations on laboratory corrugating fingers or worn flute profiles, generate artificial fluctuations in crush values. Corrugator managers adjust steam showers and web brake tension to accommodate incoming medium stiffness variations, preventing flute cracking under mechanical take-up stresses.