Organic filler like carbon black (CB) and inorganic filler like talc (T) with 0, 0.5, 1.0, 10, 20 and 40 wt% were separately loaded in high density polyethylene (HDPE) by the extrusion moulding method at 160 o C. Then, different sets of filler loaded HDPE composites were prepared using the compression moulding technique, and their structures and mechanical properties were characterized. The pure HDPE sample, as examined by the X-ray diffraction (XRD) technique, showed orthorhombic structure, which did not change either with filler types or with their concentration. The only variations found in the structure are the changes of crystallinity and crystallized size that depend on both types of fillers and their concentrations. Incorporation of CB in HDPE emphasizes the crystallinity and crystallized size more than that of T. The tensile strength of the composite decreases with the increase of both types of fillers, and this decrease is explained on the basis of Nielson model, which basically describes a poor interaction between filler and HDPE matrix. An increase of Young's modulus of 350% is observed with the increasing CB and T contents, representing an increase of the stiffness in the materials. Flexural strength increased with the increase of CB content but decreased with the increase of talc content. Although the microhardness was observed to increase with both types of fillers, the hardness value was 80% higher for CB loaded-composites than that of T at 40 wt% filler content. These findings strongly indicate that the compatibility of HDPE is better with organic filler than with inorganic one.

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Oil palm empty fruit bunch fibers were treated in sodium hydroxide solution, and then composites were produced by 0-50 wt% untreated and treated empty fruit bunch fibers with polypropylene using a twin-screw extruder followed by an injection molding machine. To improve the interfacial adhesion in and flame retardancy of the composites, malic anhydride grafted polypropylene and magnesium hydroxide were also used in the formulation as a coupling agent and a flame retardant, respectively. Composites were characterized by tensile, flexural, impact and burning tests as well as by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analyses. Tensile strength and flexural modulus of treated empty fruit bunch fibers-composite with malic anhydride grafted polypropylene and flame retardant are observed to increase by 23 and 133% more than the corresponding composite without these additives. Addition of malic anhydride grafted polypropylene considerably improves the mechanical strengths and thermal stability of the treated empty fruit bunch fibers-and untreated empty fruit bunch fibers-based composites from their respective uncoupled composites. Inclusion of flame retardant decreases the burning rate of the composites by about 60%. All these findings are attributed to the improved fibers-matrix interfacial adhesion by incorporation of malic anhydride grafted polypropylene and flame retardant, as demonstrated by scanning electron microscopy and Fourier transform infrared spectroscopy. Due to high burning resistance, the resulting composites can be proposed to apply in structural components and electrical appliances.

Biocomposites of poly(lactic acid) (PLA) and micrometre-sized graphite (GP) flake powder with 0-30 wt% GP contents have been prepared using extrusion moulding followed by compression moulding. The pure PLA and PLA-GP composites (PGC) have been examined by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy (RS), X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical and micromechanical testing, differential thermal analysis (DTA) and thermogravimetric analysis (TGA). FTIR spectra confirm the physical bond formation between GP and PLA. RS distinguishes the D-band spectra of pure PLA and PGC. XRD shows a partially crystalline structure in the PLA. SEM and TEM exhibit a clear dispersion of GP particles in PLA matrix at lower loading and aggregates at higher loading. With an increase of filler content, the tensile and flexural strengths decrease, but the Young's and tangent moduli are observed to increase by 58% and 77%, respectively. These increments represent an increase in the stiffness of the materials and are found to be consistent with the theoretical values. A decrease in microhardness with increase in filler content is also observed. Both the DTA and TGA reveal an increased thermal stability of the composites.

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