The mechanical properties of composites from recycled waste plastic and waste sawdust are of interest in trying to convert these waste streams to useful products. The development of these composites from natural fiber is therefore receiving widespread attention due to the growing environmental awareness. The effects of compositions were investigated including different grades of plastic (virgin and recycled) and amounts of wood flour, coupling agent, and ultraviolet (UV) stabilizer on mechanical and physical properties of polypropylene/rubberwood flour (RWF) composites. Virgin polypropylene gave better mechanical properties than recycled (recycled polypropylene (rPP)), both in composites and as unfilled plastic. RWF content exceeding 25 wt% enhanced the strength of RWF-reinforced rPP composites. The modulus and hardness of composites increased linearly with wood flour loadings. Maleic anhydride-grafted polypropylene (MAPP) as a coupling agent increased the strength, modulus, and hardness of the composites. However, addition of 1 wt% UV stabilizer degraded the mechanical properties. Therefore, 4 wt% MAPP content is recommended to achieve good mechanical properties of rPP/RWF composites, while the amount of UV stabilizer should be as small as possible to avoid its negative influence.
a b s t r a c tA mixture design was used in experiments, to determine the optimal mixture for composites of rubberwood flour (RWF) and reinforced recycled polypropylene (rPP). The mixed materials were extruded into panels. Effects were determined of the mixture components rPP, RWF, maleic anhydride-grafted polypropylene (MAPP), and ultraviolet (UV) stabilizer, on the mechanical properties. The overall composition significantly affected flexural, compressive, and tensile properties. The fractions of recycled polypropylene and rubberwood flour increased all the mechanical material properties; however, increasing one fraction must be balanced by decreasing the other, and the rubberwood flour fraction had a higher effect size. The fraction of MAPP was best kept in mid-range of the fractions tested, while the UV stabilizer fraction overall degraded the mechanical properties. Our results suggest that the fraction of UV stabilizer should be as small as possible to minimize its negative influences. The models fitted were used for optimization of a desirability score, substituting for the multiple objectives modeled. The optimal formulation found was 50.3 wt% rPP, 44.5 wt% RWF, 3.9 wt% MAPP, 0.2 wt% UV stabilizer, and 1.0 wt% lubricant; the composite made with this formulation had good mechanical properties that closely matched the model predictions.
Miscible block copolymer/homopolymer blends are typically prepared from homogeneous
solutions in a nonselective solvent. During solvent removal and subsequent annealing, the molecular
species comprising such blends organize in such fashion as to lower the system free energy and ideally
attain thermodynamic equilibrium. In this work, we investigate nonequilibrium triblock copolymer/homopolymer (ABA/hB) blends generated by diffusing hB molecules from a hB-selective solvent into a
lamellar ABA copolymer. Since the copolymer is already microphase-ordered during homopolymer
incorporation, we refer to such blends as mesoblends. The mass uptake of hB is found to be strongly
dependent on homopolymer molecular weight (M
hB), with the maximum solubility scaling as M
hB
-1. An
induction period that scales as M
hB
1/2 is also observed. Transmission electron microscopy reveals that
the morphology of these mesoblends appears to be perforated lamellar, which, in some cases, transforms
to cylindrical upon annealing. Dynamic mechanical analysis and differential scanning calorimetry confirm
that the A-rich microdomains in the mesoblends are plasticized. The mechanical properties of these
mesoblends can be improved upon annealing, but nonetheless differ from those of composition-matched
conventional blends.
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