The biocomposites of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3,4HB)] and recycled carbon fiber (RCF) were
prepared via a melting extrusion. The crystallization behaviors and
kinetics of the P(3,4HB) matrix in composites were exclusively studied
under both nonisothermal and isothermal conditions. The corresponding
results indicated that the P(3,4HB) either neat or compositing with
RCF had a dual-peak cold crystallization behavior in the nonisothermal
condition, and the isothermal crystallization rate of P(3,4HB) in
composites was jointly determined by the rates of the nucleation and
the crystal growth and integrity. However, it was reduced with the
incorporation of RCF. Wide-angle X-ray scattering investigation demonstrated
that the presence of RCF did not change the crystallization mechanism
and crystalline structure of the P(3,4HB) matrix, but the crystallinity
of the P(3,4HB) either neat or compositing with RCF was enhanced with
an increase of crystallization temperature. Dynamic mechanical analysis
revealed that the storage moduli of P(3,4HB)-based composites were
significantly improved with increasing the RCF loadings, and the dual
internal friction peaks corresponding to the thermal motion of surface
molecule of crystalline zone and the glass transfer of whole macromolecules
were observed on the thermograms of the P(3,4HB) either neat or compositing
with RCF. The mechanical properties including tensile, flexural, and
notched Izod impact strength were significantly improved in the presence
of RCF, and such reinforcing and toughening effects were due to the
good interfacial adhesion between RCF and P(3,4HB) as a result of
bonding effect of silane coupling agent. Scanning electronic microscopy
further confirmed a good dispersion of RCF in P(3,4HB) matrix and
a strong interfacial interaction between fibers and matrix.