The different capillary flow regimes of entangled polydimethylsiloxane polymers: macroscopic slip at the wall, hysteresis and cork flow

International audienc

Rheological and Thermal Properties of PP-based WPC

Wood Plastic Composite (WPC) has attracted great interest in outdoor building products for the reduced cost and the possibility of using recycled materials. Nevertheless the material shows two problems: the large viscosity due to the presence of high concentrations of filler and the degradation of cellulose during processing The aim of this work was to investigate the rheological and thermal properties of WPC. The material used for the experiments was a commercial PP-based WPC compound, with different concentrations of natural fibers (30, 50, 70% wt.). The thermal properties were studied to check for degradation of natural fibers during the subsequent rheological tests. Analyzing the storage and loss moduli and the complex viscosity curves obtained using a parallel plate rheometer it was possible to observe some features related to the viscoelastic nature of the composite

In – line vs. off – line rheological characterization of wood polymer composites

In a previous study [1], a commercial PP - based Wood Polymer Composite (WPC) filled with various percentage of white fir fibers (30% – 70% wt.) has been investigated with a parallel plate rheometer in oscillation mode at 170 °C. This temperature has been imposed by the requirement of performing the rheological test within the linear viscoelasticity region (LVR), but the data that are measured are not directly useful for processing, as the required temperature lies between 180 – 195 °C. In order to obtain the WPC viscosity at such temperatures, a model that uses the WPC viscosity measured at 170 °C at different fibers quantity and of neat polypropylene viscosity measured at various temperatures has been proposed. These measurements allowed to obtain shift factors useful to estimate the WPC viscosity at any temperature and percentage of fibers. The aim of this work has been to validate such a model using an in – line rheometer directly connected to a single screw extruder. With this apparatus, 30% and 70% wt. WPC flow curves at 195°C have been measured in a setting that is similar to processing conditions. The results show that the viscosity curve for the 30% wt. WPC validates the model with a reasonably good agreement, while the agreement for the 70% wt. is less evident. Several reasons are proposed to explain this deviation, in particular the presence of an yield stres

Rheological and mechanical characterization of polypropylene-based wood plastic composites

International audienc

Melt extrusion of polystyrene reinforced with cellulose nanocrystals modified using poly (styrene)-co-(2-ethylhexyl acrylate) latex particles

Non-covalent modification of cellulose nanocrystals (CNC) was performed using a water based method with laboratory prepared statistical copolymer, viz. poly [(styrene)-co-(2-ethylhexyl acrylate)], by ionic interactions. The thermal, functional and morphological properties of modified CNC were characterized by thermogravimetric analysis (TGA), Fourier vansform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Their hydrophobic nature was investigated by contact angle measurements. These nanoparticles were used to prepare polystyrene (PS) nanocomposites by twin-screw extrusion. The thermomechanical performance of the ensuing composites was examined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The morphology of the materials was also studied using scanning electron microscopy (SEM)