Micro-injection moulded composites of softwood fibres from two different pulping processes in thermoplastic polypropylene matrix have been studied. Surface modification of hydrogen peroxide bleached thermo mechanical pulp fibres (BTMP) from spruce (Picea abies L.) and chemical sulphate pulp fibres (BKraft) from pine (Pinus sylvestris L.) was achieved by co-precipitation of layered double hydroxide (LDH) particles that were further functionalized with sodium dodecyl sulphate (SDS) surfactant in conditions similar to wet end in paper production. Micro-injection moulded test specimens were subjected to uniaxial tension tests, water absorption, micromechanical deformation and microscopic studies. Optical micrographs show that functional pulp was homogeneously dispersed into polypropylene matrix where as the untreated fibres agglomerated during moulding. When composites were prepared with BTMP fibres the electrostatically bound SDS on fibre surface increased elongation at break by 70%. LDH particles intensified dissipation of shear energy to BKraft fibres degrading the average fibre length by 50% during moulding. Functionalization with SDS surfactant, however, increased average fibre length up to 125% in comparison to LDH modification.

Carl Lange, Farid Touaiti, Pedro Fardim, Hybrid clay functionalized biofibres for composite applications, Composites Part B: Engineering, Volume 47, 2013, Pages 260-266, ISSN 1359-8368, https://doi.org/10.1016/j.compositesb.2012.10.032.
(http://www.sciencedirect.com/science/article/pii/S1359836812007317)