Utilization of recycled polymer matrices for production of eco-composites

Abstract: One of the big new areas of development of the advanced composite materials is in combining natural fi bers with thermoplastics for producing lightweight, environmentally friendly, cost-effective composite material. The aim of this work is to show the possibilities of recycling and reuse of thermoplastic polymer matrices with rice hulls (RH) and kenaf fi bres (KF) using the conventional techniques, extrusion and compression moulding. The matrices (polypropylene (PP) and poly(lactic) acid (PLA) ) were recycled one and two times and the fi bers/fi ller were compounded with recycled matrix. The processing and material properties have been studied on the composites with recycled matrix and compared to the composites with virgin matrix. Characterization of all composites includes mechanical, morphological and thermo-gravimetrical analysis. Тhe fl exural properties for PP recycled based composites were held close to the fl exural properties for composite based on neat PP, but for PLA recycled based composite the fl exural properties are decreased for about 50%. The thermal stability of recycled matrices based composites is very similar to the thermal stability of the composites with virgin matrix. SEM analysis has shown that the fi llers/fi bers are covered by the recycled polymer matrix, indicated on the satisfi ed durability of the recycled polymer matrices. The obtained results have shown that both polymer matrices (biodegradable and no degradable) could be recycled with acceptable mechanical properties and they can be successfully used for production of eco-composites. Keywords: eco-composites, polypropylene, poly(lactic acid), rice hulls, kenaf fi bers, extrusion compressio

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

Biocomposites based on poly(lactic acid) and kenaf fibers: effect of microfibrillated cellulose

In this work, the influence of microfibrillated cellulose (MFC) on the basic mechanical properties of PLA/kenaf fiber biocomposites has been studied. The addition of 5–15 % microfibrillated cellulose to a biocomposite premix has resulted in an increased glass transition temperature of the final product, produced by compression molding of previously melt-mixed composite components. The presence of MFC has influenced the interface-sensitive properties of the PLA/kenaf composite: at an optimal loading of 10 %, the interfacial energy release rate was increased by about 20 %. Moreover, flexural strength and modulus of the composites were also improved (from 34.8 MPa to 57.1 MPa and from 4.9 GPa to 5.8 GPa, respectively). Keywords: biocomposites; poly(lactic acid); kenaf fibers; microfibrillated cellulos

Isothermal crystallization of iPP in model glass‐fiber composites

: Isothermal crystallization of iPP in model glass-fiber composites is studied by DSC, and the basic energetic parameters of crystallization are determined. Unsized untreated and thermally treated glass fibers are used in model composites to determine the role of the surface on nucleation and crystallization processes. Thermally treated glass fibers are found to exhibit a predominant nucleating effect as compared to unsized untreated ones, and the crystallization proceeds faster, resulting in lower values for the half-time of crystallization (10–120 s). The energy of formation of a nuclei of critical dimensions at a given Tc is also lower, and it decreases as the content of the fibers in the composite increases. The surface free energy of folding, σe = 140 × 10−3 J/m2, was determined for iPP in the composite containing 50% glass fibers, while for pure iPP, σe = 170 × 10−3J/m2 was found

Mehanička svojstva staklo/PET kompozita iz pletenih predoblika - utjecaj finoće pređe

Ispitivan je utjecaj finoće pređe na mehanička svojstav staklo/PET termoplastičnih kompozita od kulirnih pletenih predoblika. Primijenjeni su teoretski modeli modula i čvrstoće istezanja za ispitivane kompozite. S povećanjem finoće pređe postiže se manja varijacija svojstava kompozita. Teoretski i eksperimentalni rezultati modula i čvrstoće istezanja kompozita pokazuju sličan trend promjene mehaničkih svojstava s promjenom finoće pređe. Razlika između teoretskih i eksperimentalnih rezultata je najmanja kod kompozita s najfinijom pređom

Electron spin resonance on hybrid nanocomposites based on natural rubber

Electron spin resonance (ESR) was used as a new method to analyze the synergy between two nanofillers dif-ferent by nature, form and rigidity dispersed in natural rubber matrix. Natural rubber (NR) nanocomposites loaded with fixed amount of carbon nanotubes (2 parts per hundred of rubber parts ; phr) and various amounts of expanded organically modified montmorillonite (EOMt, 4–20 phr) were investigated. The dependence of the double integral of the resonance spectra on the amount of EOMt present in the natural rubber was established. Its decrease with an in-creaseof the amount of EOMt confirmed the synergy between these two nanofillers. Also DMA temperature sweep measurements were performed and the cluster-cluster aggregation (CCA) model was used to assess the apparent filler networking energy. The obtained results suggest that the presence of the EOMt above a critical amount strengthens the hybrid-filler networking