Polypropylene/coir fiber composites were prepared according to an experimental statistical design, in which the independent variables, coir fiber, and compatibilizer content, were varied. The compatibilizer used was maleic anhydride grafted polypropylene (PP-g-MA). Compatibilizer free composites were also prepared. Composites were processed in a corotating twin-screw extruder and submitted to mechanical and morphological analyses. The effects of the independent variables on the mechanical properties were assessed through tensile strength, elongation at break, flexural modulus, and impact strength. The morphological properties were assessed by scanning electron microscopy (SEM). The results indicated the need for using compatibilizers in the composites due to the incompatibility of PP and coir fiber. The variable with the strongest effect on the properties was coir content, whose increase caused increase in tensile strength, impact strength and elastic modulus, and decrease in elongation at break. The presence of PP-g-MA was fundamental to achieving the aforementioned results. The effect of increasing compatibilizer content was only observed for the elastic modulus.

The solubility of docosane in heptane has been determined in the range of (277.25-317.65) K. The effect of ultrasonic waves in the solubility was studied. The results can be fitted with high accuracy to the relationship log 10 (x 1 ) ) A + B/T + C log 10 (T). It was found out that the ultrasound did not affect the system solubility and the system behaved as an ideal solution.

The response of a granular material during a stop-and-go shear experiment is investigated using an annular shear cell and silicagel powders of different particle sizes. The experimental results are examined on the basis of the Dieterich-Rice-Ruina model for solid friction. In addition to making this analogy with solid friction, we describe a new instability that is observed when restarting shear, where the powder bed is found to slip and compact for short hold times but only dilates for long hold times. The minimum hold time to restore a non-slip behaviour has been investigated for different size particles and normal loadings. The observed dependencies show analogies between this behaviour and the sliding rearrangements seen above the stick-slip threshold.

The densification dynamics and flow properties of powdery to granular varieties of commercial sugars were obtained. Samples of granular sugar (GS), refined (RS) sugar, a raw type VHP sugar (VS), and icing sugar (IS) were characterized concerning particle morphology, size distribution, loose and tapped bulk densities. Primary particles of IS sugar have a mean size (D50) of 77 μm and they agglomerate into larger size granules with intraparticle voidage. The RS, GS and VS sugars have D50 equal to 286 μm, 537 μm, and 696 μm, respectively. The RS sugar revealed some irregular and rough agglomerates, while the other samples were composed of flat and well‐defined crystals. After full compaction, the initial bulk volume of the IS sugar was reduced by 25%, of the RS sugar by 18%, of the GS and VS sugars by about 10%. The IS sugar was the sample with poorest flowability, based on a Hausner ratio equal to 1.33. Compared to the others, this sugar variety presented a higher bed porosity and a smaller tapped density. In spite of its irregular shaped particles, the RS sugar compacted easily and achieved the same tapped density of samples with well‐defined granular particles. A slower compaction kinetic was observed for the coarser sugar—VS (D50 = 696 μm). Finally, the static and dynamic repose angles increased from the granular (GS and VS) to the powdery sugars (RS and IS), but for the latter ones the values were not significantly different in spite of the mean sizes decreased from 206 μm in the RS sugar to 77 μm in the IS. A more relevant difference was observed in the dynamic repose angle for the powdery sugar and the difference between the dynamic and static repose angles increased as the mean particle size was reduced. According to their repose angles, the flowability would be classified as good (GS and VS) or fair (RS and IS). The densification dynamics of all sugars were fitted with good accuracy to an empirical equation. Practical applications Powder flow is influenced by the presence of fines contained in the bulk powder, by the particles' size distribution and by their morphological characteristics. To meet the different needs of customers, a number of sugar varieties are marketed, including the granulated white sugar, the brown raw sugars and the powdery refined sugars. Every sugar variety behaves differently in operations such as packing, transport, and discharge from silos and hoppers. As sugar manufacturing plants deal with materials in a broad range of sizes and shapes, data of basic flow indicators for different sugar varieties obtained under standardized and comparable conditions may be useful for predicting the performance of a processing plant and monitoring the product quality attributes and for designing equipment as well.

We propose an analytical expression for the shape of a heap of cohesive powder when the cohesion is constant, and when the cohesion increases proportionally with the stresses applied. From the results obtained, we discuss the possibility to extract quantitative information on the flowability of a powder from this shape.