Rapid discrimination of plastic packaging materials using MIR spectroscopy coupled with independent components analysis (ICA)

Plastic packaging wastes increased considerably in recent decades, raising a major and serious public concern on political, economical and environmental levels. Dealing with this kind of problems is generally done by landfilling and energy recovery. However, these two methods are becoming more and more expensive, hazardous to the public health and the environment. Therefore, recycling is gaining worldwide consideration as a solution to decrease the growing volume of plastic packaging wastes and simultaneously reduce the consumption of oil required to produce virgin resin. Nevertheless, a major shortage is encountered in recycling which is related to the sorting of plastic wastes. In this paper, a feasibility study was performed in order to test the potential of an innovative approach combining mid infrared (MIR) spectroscopy with independent components analysis (ICA), as a simple and fast approach which could achieve high separation rates. This approach (MIR-ICA) gave 100% discrimination rates in the separation of all studied plastics: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS) and polylactide (PLA). In addition, some more specific discriminations were obtained separating plastic materials belonging to the same polymer family e.g. high density polyethylene (HDPE) from low density polyethylene (LDPE). High discrimination rates were obtained despite the heterogeneity among samples especially differences in colors, thicknesses and surface textures. The reproducibility of the proposed approach was also tested using two spectrometers with considerable differences in their sensitivities. Discrimination rates were not affected proving that the developed approach could be extrapolated to different spectrometers. MIR combined with ICA is a promising tool for plastic waste separation that can help improve performance in this field; however further technological improvements and developments are required before it can be applied at an industrial level given that all tests presented here were performed under laboratory conditions.     

Renewable Cellulose Derived Carbon Nanospheres as Nucleating Agents for Polylactide and Polypropylene

Nucleation of polylactide and polypropylene using novel renewable resource biobased carbon nanospheres (CNS) is investigated using differential scanning calorimetry and polarized optical microscopy. Isothermal studies near the optimal crystallization temperature demonstrate at least a five-fold increase in crystallization rate in PP but only a 1.4 times faster crystallization in PLA. Non-isothermal studies reveal an asymptotic relationship of the maximum crystallization temperature with increasing CNS weight loading in PP and no relationship in PLA. Microscopy indicates some aggregation in the solution blended samples and that average spherulite size is reduced 10-fold due to faster nucleation in the composites as compared to the neat polymer. The fractional crystallinity achieved during non-isothermal crystallization increases by about 7% with addition of a small amount of CNS and decreases with weight loading higher than 1%. The crystallization rates obtained in polypropylene are competitive with widely used mineral talc nucleating agents.     

Maleated Polylactide as an Interfacial Compatibilizer in Biocomposites

The aim of the research described in this paper was to prepare and characterize a maleated polylactide (MAPLA) and to study whether use of this additive might enhance the properties of polylactide (PLA) biocomposites. PLA and MAPLA prepared in the laboratory were characterized using various analytical techniques and the effect of using MAPLA as an additive was investigated by three methods: (a) compounding with a commercially available l-PLA and wood fiber in a Brabender mixer, (b) compounding with commercially available l-PLA and nanoclay in a Haake mini-extruder, and (c) solution treatment of jute fiber mats that were then used to prepare jute-PLA composites by a compression molding process. Scanning electron microscopy (SEM) photomicrographs of the wood-PLA compound prepared in the Brabender mixer suggested some improvement in adhesion might have occurred in the presence of MAPLA. Rheological and X-ray diffraction measurements on nanoclay-PLA compounded in the mini-extruder gave mixed results but did not indicate beneficial effects from addition of MAPLA to the process. Tensile testing of jute-PLA composites showed a reduction in composite tensile strength resulting from addition of MAPLA to the fibers. Possible reasons for these results and options for further research are discussed.