Raluca Nicoleta Darie

On the compatibility of the IPP/PA6/EPDM blends with and without functionalized IPP I. Thermo-oxidative behaviour

Abstract Binary isotactic polypropylene (IPP)/polyamide 6 (PA6) and ternary IPP/PA6/ethylene–propylene diene terpolymer (EPDM) blends in various ratios were obtained in a Haake Rheocord mixer. Processing behaviour was changed in the presence of IPP functionalized with bismaleimide (BMI), maleic anhydride (MA) and acrylic acid (AA) as reactive compatibilizing agents. The thermal and thermo-oxidative behaviour of blends was studied by differential scanning calorimetry and thermogravimetry. The functionalized IPPs modify the crystallinity degree and the decomposition behaviour of both IPP and PA6 as a result of chemical reactions of functional groups with those of the PA6. The changes depend on the IPP/PA6 or IPP/PA6/EPDM ratio, the chemical nature and amount of the functionalized IPP. On the basis of the processing and thermal data one can conclude that the compatibilizing agent effect increases in the following order: IPP-AA

Influence of Accelerated Weathering on the Properties of Polypropylene/Polylactic Acid/Eucalyptus Wood Composites

In the view of producing environmentally friendly materials without compromising properties, new composites containing polypropylene as a matrix and eucalyptus wood, with or without 15% of polylactic acid, were melt processed. In order to improve compatibility between components, a chemical modification of wood with toluene-2,4-diisocyanate (TDI) was realized and evidenced by changes in FT-IR and XPS spectra. The morphological, mechanical, and thermal characterizations of the obtained composites were evaluated before and after accelerating weathering. The results showed that the material comprising 15% TDI-modified wood, PP, and 15% PLA exhibited the best properties.

Investigation of Poly(vinyl alcohol)/Pluronic F127 Physical Gels

The application of Pluronic F127 as injectable gel-forming solution is limited by poor mechanical properties. The purpose of this study was to develop low viscosity formulations at ambient temperature that undergo a transition to gel under physiological conditions. Mixtures of Pluronic F127 and poly(vinyl alcohol) with different compositions were prepared in aqueous solutions and their in-situ gelation was investigated by dynamic light scattering and rheology. The results obtained for different formulations showed synergistic effects of polymer mixtures in aqueous media and their properties can be tuned by varying polymer concentration, system composition or changing temperature.

Polypropylene-based composites reinforced by toluene diisocyanate modified wood

Composites made of polypropylene, a mixture of polypropylene and poly(lactic acid) and spruce wood fibres both non-modified and modified with toluene 2,4-diisocyanate – were prepared by melt blending. The chemical modifications of wood fibres with toluene 2,4-diisocyanate were evidenced by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Wood fibre reinforced polypropylene/poly(lactic acid) composites prepared with addition of maleic anhydride polypropylene as coupling agent were further investigated for structural and morphology properties before and under controlled accelerated weathering conditions by attenuated total reflectance Fourier transform infrared spectroscopy, mechanical testing and scanning electron microscopy analysis. Some specific indexes (carbonyl and vinyl) were also calculated.

Erosion as a possible mechanism for the decrease of size of plastic pieces floating in oceans

A sea water wave tank fitted in an artificial UV light weathering chamber was built to study the behaviour of polypropylene (PP) injected pieces in close ocean-like conditions. In air, the same pieces sees a degradation in the bulk with a decrease of mechanical properties, a little change of crystal properties and nearly no change of surface chemistry. Weathering in the sea water wave tank shows only a surface changes, with no effect on crystals or mechanical properties with loss of small pieces of matter in the sub-micron range and a change of surface chemistry. This suggests an erosion dispersion mechanism. Such mechanism could explain why no particle smaller than about one millimeter is found when collecting plastic debris at sea: there are much smaller, eroded from plastic surfaces by a mechano-chemical process similar to the erosion mechanism found in the dispersion of agglomerate under flow.

Wastes from Wood Extraction Used in Composite Materials: Behavior after Accelerated Weathering

New materials were obtained by incorporating in polypropylene (PP) matrix 60% wood wastes resulting after extraction with supercritical carbon dioxide, water, and ethanol. Structural, mechanical, thermal, and rheological characterizations, as well as moisture uptake of the composites, were evaluated before and after accelerated weathering. It was found that the extraction method influenced the composite properties due to the hydrophilic-hydrophobic balance. The addition of extracted fibers results in an increase in hardness and tensile properties and a decrease of impact strength as compared to PP.

Innovative Biocomposite Derived from Waste Materials with Applications in Electrical Domain

The article highlights the possibility of producing biocomposite material from plastic (e.g. polypropylene) and natural organic materials used as fillers (eggplant flour) which have applications in electrical domain. The right amount of material used as filler is evaluated using mechanical tests and dielectric spectroscopy in order to obtain an optimal structure biodegradable, making it suitable as a viable technical solution to partially replace electrical enclosures or different insulators.

Development of New Materials for Construction Sector Obtained from Renewable Resources

Article tries to highlight the advantages of using in construction area of composites materials obtained from recycled polyethylene and wood dust in the presence of compatibilizing agents. The composite materials have been evaluated in terms of dielectric properties and mechanical characteristics to take into account for the optimum materials structure. The advantage of composite materials made of plastic is that those can be designed in accordance with the formulas of composite plastic and technology to achieve high performance properties in a wide variety of commercial and residential construction applications.

Morphology and Dielectric Properties of some LDPE/PA Blends in Presence of Compatibilizers

The article emphasizes the improvement of compatibility in a polymer blend composed of two normally incompatible constituents as LDPE and PA6. The effect of amount and type of compatibilizing agents is evaluated using electronic microscopy and dielectric spectroscopy, to obtain the optimum materials structure.