Microfibril angle scanning of increment cores by x-ray diffractometry

The mechanical properties of paper are strongly influenced by the strength and stiffness of the fibres from which it is formed. Fibre strength and stiffness are largely controlled by microfibril angle (MFA). X-ray diffraction patterns have been obtained at sub-millimetre resolution along radial strips from both Pinus radiata and Eucalyptus nitens samples. Variation in MFA, as estimated from the patterns after correction for fibre tilt, has now been added to a range of fibre properties which include coarseness, wall thickness and diameter. A new apparatus includes an X-ray area detector which reduces the measurement time for a single MFA estimate from 60 minutes to 30 seconds. An important criterion for the design of the instrumentation was that measurement must be done using the same samples currently prepared for automated densitometry and image analysis. Therefore no additional sample preparation is necessary. Although the MFA measurement rate-spatial resolution combination cannot match that for the other properties owing to the relative weakness of diffracted radiation, automation and the judicious choice of within-sample measurement positions makes feasible the routine assessment of MFA in increment cores.