Polypropylene-based Eco-composites Filled with Agricultural Rice Hulls Waste

In this workthe properties of rice-hull-filled polypropylene (PP) composites were investigated with the purpose of enhancing adhesion between the polymer and the filler through the addition of w = 5 % PP-grafted-MA (CA). Composites containing w = 20 and 30 % rice hulls (RH), as well as composites with a certain amount of PP matrix substituted with a coupling agent, were prepared by extrusion and compression moulding. The composites’ mechanical properties were investigated through tensile and fracture tests at low and high strain rate, using the concept of linear elastic fracture mechanics. Introduction of rice hulls in the PP matrix resulted in a decreased stress at peak, together with increase of composites tensile modulus (EPP = 1013 MPa, EPP/RH (ζ = 0.70:0.30) = 1690 MPa) and modulus in flexure. Introduction of w = 5 % PP-g-MA caused 6 % and 12 % improvement in the composite tensile strength, respectively for the PP composites with w = 20 and 30 % rice hulls. Modulus in flexure for the composite PP/RH/CA (ζ = 0.65:0.30:0.05) reached Ef = 1646 MPa, which was an improvement of 52 % when compared to pure polypropylene. Kc and Gc values were determined for PP and PP-based composites. Thermal stability of PP was slightly improved by adding rice hulls

Nucleation activity of glass fibers towards iPP evaluated by DSC and polarizing light microscopy

Nucleation activity of unsized and differently sized glass fibers during the crystallization of polypropylene from melt was investigated by polarizing light microscopy and DSC. Depending on the type of surface treatment, glass fibers were shown to exhibit different nucleating effects, evaluated by induction time of crystallization, crystallization onset temperature as well as half-time of crystallization in model composites with 50% wt glass fibers. Predominant nucleation activity was found for glass fibers sized with polypropylene compatible dispersion containing polyurethanes. However, according to the results of DSC measurements, unsized glass fibers slightly depressed the nucleation of polypropylene. Using the approach of Dobreva et al., the activity of the fibers towards heterogeneous nucleation during nonisothermal crystallization was evaluated

Isothermal crystallization kinetics of polypropylene latex-based nanocomposites with organo-modified clay

The effect of organo-modified clay (Cloisite 93A) on the crystal structure and isothermal crystallization behavior of isotactic polypropylene (iPP) in iPP/clay nanocomposites prepared by latex technology was investigated by wide angle X-ray diffraction, differential scanning calorimetry and polarized optical microscopy. The X-ray diffraction results indicated that the higher clay loading promotes the formation of the β-phase crystallites, as evidenced by the appearance of a new peak corresponding to the (300) reflection of β-iPP. Analysis of the isothermal crystallization showed that the PP nanocomposite (1% C93A) exhibited higher crystallization rates than the neat PP. The unfilled iPP matrix and nanocomposites clearly shows double melting behavior; the shape of the melting transition progressively changes toward single melting with increasing crystallization temperature. The fold surface free energy (σe) of polymer chains in the nanocomposites was lower than that in the PP latex (PPL). It should be reasonable to treat C93A as a good nucleating agent for the crystallization of PPL, which plays a determinant effect on the reduction in σe during the isothermal crystallization of the nanocomposites. The activation energy, ΔE a, decreased with the incorporation of clay nanoparticles into the matrix, which in turn indicates that the nucleation process is facilitated by the presence of clay

Characterization of latex-based isotactic polypropylene/clay nanocomposites

Polypropylene/clay nanocomposite (PCN) containing 1 wt% organo-modified clay was prepared by latex technology, previously successfully applied for preparation of carbon nanotubes (CNTs)/polymer composites. The level of dispersion of organoclay and the microstructure of the resulting PCNs were characterized by means of X-ray diffraction analysis, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The obtained results have demonstrated that the latex technique represents a promising method for preparation of PP/clay nanocomposites with good dispersion of exfoliated nanoclay particles. The influence of clay nanoparticles on nonisothermal crystallization of PCN was investigated by DSC. The crystallization onset temperature of the matrix rises for about 5 °C when crystallizing from the quiescent melt. Improved thermal stability of PP/nanoclay was observed as evaluated by TGA. The dynamic mechanical analysis reveals an increase in storage modulus of PP matrix in the nanocomposites for 30% over a temperature range, indicating an increase in the stiffness of the material with the addition of organically modified clay

Rice straw as an alternative reinforcement in polypropylene composites

We studied the use of rice straw as reinforcement in maleated polypropylene (PPm). Composites containing 20 and 30% by weight rice straw were successfully prepared by extrusion and compression molding. The samples were characterized by tensile tests, differential scanning calorimetry (DSC), thermogravimetry (TGA), dynamo-mechanical analysis (DMTA) and scanning electron microscopy (SEM). The results of the mechanical properties showed that rice straw can be used as an alternative reinforcement for polypropylene. Higher tensile moduli (E) were obtained for composites containing higher rice straw content. Thermogravimetric curves of the composites exhibit two-stage decomposition process and slightly higher thermal stability. Higher crystallization (Tc) and melting peak temperatures for composites were detected by DSC analysis (Tcpp = 107.8 °C, TcRS/PP(20/80) = 114.5 °C). The renewability of rice straw and the recyclability of thermoplastic polypropylene provide an attractive eco-friendly quality to the resulting composites

Effect of different thermal treatments on the mechanical performance of poly(L-lactic acid) based eco-composites

PLLA-based eco-composites reinforced with kenaf fiber and rice straw and containing red or yellow pigments have been studied. The mechanical behavior of the composites was tested by DMTA at two different annealing temperatures (65°C and 85°C) and times (15 min and 120 min) as well as at two preparation conditions: vacuum drying and long time at room temperature. A decrease of microhardness was observed during the water absorption tests. Moreover, the rice straw-based composites absorbed more water than the kenaf-ones. Generally, the dyed NFs composites presented better water resistance than undyed ones. The pigments improved the adhesion and led to better mechanical performance. The natural fibers favored the cold crystallization process of PLLA and shifted the cold crystallization peak temperature to lower values, as it was confirmed by DSC measurements. The values of tensile storage modulus obtained after different preparation condition were strongly affected by the process of physical ageing. According to, tan d parameter, the samples stored at room temperature for a long time showed the highest amorphous content. The PLLA eco-composite reinforced with kenaf fibers, dyed with the red pigment, and annealed at 85°C for 2 h displays the best mechanical properties.Peer reviewe