Study of thermodegradation and thermostabilization of poly(lactide acid) using subsequent extrusion cycles

The thermomechanical degradation and thermostabilization of poly(lactic acid) (PLA) have been studied using subsequent extrusion cycles under different temperature profiles. Primary and secondary antioxidants were used to avoid degradation process during extrusion. Melt flow index (MFI), size exclusion chromatography (SEC), and infrared spectroscopy (FTIR) analysis were used to evaluate the degradation and stabilization of PLA. The MFI and SEC analysis show that the main thermodegradation mechanism of PLA is governed by scission reactions. FTIR analysis confirmed the SEC results and showed that the synergetic effect between primary and secondary antioxidant is a suitable way to thermostabilize the PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40023.     

CFD predictions for hazardous area classification

This study aimed to describe a Computational Fluid Dynamics(CFD) procedure using the ANSYS CFX software 16.1 and Design of Experiments for the determination of volume and extension of explosive atmospheres due to fugitive emissions of flammable gases.The multidimensional statistical sampling technique Latin Hypercube was used, which defined 100 simulations of random methane gas leak conditions.The CFD model proved to be robust in predicting the extension and volume of the explosive atmosphere for orifice diameters from 0.1 to2.5 mm, pressure from 0.1 MPa to 12 MPa and temperatures from 0 ℃ to 400 ℃.It was found that the calculation domain must be parameterized 8 m in length for each millimeter of the diameter of the source of release to ensure the predictions.In order not to lose precision for very small diameters, the mesh was parameterized with 50 elements along the orifice diameter.It was proved that gravity does not influence the extension and volume of the explosive atmosphere at sonic emissions.The deviation from the ideal gas behavior in the reservoir,achieved by applying the Soave–Redlich–Kwong equation of state, also has not significantly influenced the extension and volume of the explosive atmosphere.The results showed that the size of the explosive atmosphere varies directly with the diameter of the source emission and reservoir pressure, and inversely with the temperature of the reservoir.The diameter of the source is the parameter that has the major effect on the extension of the explosive atmosphere, followed by the pressure and lastly the temperature of the reservoir.     

Acerola and cashew apple as sources of antioxidants and dietary fibre

Several tropical fruits have been described as natural sources of dietary fibre (DF) and phenolic compounds, associated with different health effects. The aim of this work was to ascertain the DF, phenolic compounds content (including non‐extractable polyphenols, mostly associated with DF) and antioxidant capacity in acerola fruits and cashew apples from selected clones. ‘BRS 236’ acerola fruits presented a high antioxidant capacity because of the combination of both extractable polyphenols and l ‐ascorbic acid (providing together a Folin value of 170 kg^?1 g d.m.). ‘CCP 76’ cashew apples contained 28 g kg^?1 d.m. of extractable polyphenols and 13 g kg^?1 d.m. of ascorbic acid as well as a high amount of non‐extractable condensed tannins (52 g kg^?1 d.m.). DF content was of 260 g kg^?1 d.m. in acerola fruit and of 209 g kg^?1 d.m. in cashew apple. Acerola fruits and cashew apple should therefore be considered as new natural sources of DF and phenolic compounds.     

Comparison of the damage in sapphire due to implantation of boron, nitrogen, and iron

The damage microstructure and optical properties of sapphire implanted with boron, nitrogen and iron were examined by RBS-C, TEM, and optical absorption. Implantations were conducted at RT and 1000 °C at 150 keV and fluences of 3 × 10¹⁶-1 × 10¹⁷ ions/cm². Optical absorption measurements indicate that the boron-implanted samples contained the highest number of F-type centers and the nitrogen-implanted samples the fewest. The microstructure of the boron-implanted samples shows only ‘black-spot’ defect clusters, as did the iron-implanted samples at the lower fluences. At higher fluences, the iron implanted samples revealed the presence of nanometer-sized precipitates of single crystal bcc iron that contributed to additional optical scattering. Bubbles formed in samples implanted with low fluences of nitrogen. A second damage region is apparent in the RBS-C patterns for higher fluences of nitrogen.     

Effects of spontaneous and inoculated fermentation on the volatile profile of lychee (Litchi chinensis Sonn) fermented beverages

The aim of this study was to evaluate the contribution of yeast to the volatile profile of beverages obtained by the fermentation of lychee must through inoculated (Saccharomyces cerevisiae strains UFLA CA116 , UFLA CA1183 and UFLA CA1174 ) and spontaneous fermentation. Higher alcohols and esters were the primary volatiles detected by SPME/GC–MS. A Principal Component Analysis indicated similarities between UFLA CA116 and UFLA CA1183 and between UFLA CA1174 and spontaneous fermentation. Changing the yeast strain used in the fermentation process has the potential to modulate the volatile profile of fermented beverages. The beverage produced by the inoculation of yeast CA1183 showed the most complex aroma profile compared to the other beverages.     

Influence of synthesis conditions on carbonate entrapment in perovskite SrSnO3

Strontium stannate (SrSnO₃), a perovskite material, was synthesized by the polymeric precursor method, with different routes to eliminate organic matter. The utilization of pure oxygen for the elimination of organic matter changed the Raman spectra, especially in the low frequency region. Some peaks, which were previously assigned to the perovskite phase, were not noticed when the carbonate amount was lower. On the other hand, the profile of the IR spectra and XRD patterns did not change. These results suggest that carbonate may be present inside the perovskite lattice.     

Sustainable design procedure: The role of composite materials to combine mechanical and environmental features for agricultural machines

The improvement of environmental performance of products is the main focus for many companies. Although, methodologies are fundamental in the design process in order to introduce environmental inputs in the development, it has not been a comfortable practice for companies. In this context, this study is concerned with the development of procedural guidelines for how ecodesign concepts may be introduced to the selection of material. The results point out the importance of the introduction of environmental parameters, since the beginning of the project. In regards to composite material, it is possible to note that vegetable fibers are good choice replacements for fiberglass.     

Enhancement of the photoelectrochemical response of poly(terthiophenes) by CdS(ZnS) core-shell nanoparticles

We have investigated the photoelectrochemical properties of hybrid films of polythiophenes poly(4,4″dimethoxy-3′-methyl-2,2′:5′,2″ terthiophene) (PDM), poly(4,4″dipentoxy-3′-methyl-2,2′:5′,2″ terthiophene) (PDP), and cadmium sulfide/zinc sulfide (CdS(ZnS)) core-shell nanoparticles. Although CdS(ZnS) nanoparticles present enhanced exciton trapping, light harvesting by hybrid films was enhanced when compared to those of pure PDM and PDP films. This enhancement is explained in terms of electron and hole transfer mechanisms at different excitation wavelengths. The more efficient light harvesting of PDM/CdS(ZnS) when compared to that of PDP/CdS(ZnS) was attributed to its broader absorption spectrum and more efficient electron hopping.     

Surface modification of polystyrene and poly(ethylene terephtalate) by grafting poly(N-isopropylacrylamide)

In this work, poly(N-isopropylacrylamide) (PNIPAAm) was incorporated into previously oxidized PS and PET surfaces by grafting using two photo-initiation pathways. The incorporation of PNIPAAm was observed by drop water contact angle measurements, dyeing with Methylene Blue and AFM images analysis of the virgin and modified polymers. It was verified that the grafting process depends on the chemical surface environment. The grafted surfaces are hydrophilic below 32 °C and hydrophobic above this temperature. The transition is due to the incorporated PNIPAAm. This characteristic gives to the grafted materials potential to be applied as biomaterials.     

Optical and structural behaviour of Mn implanted sapphire

Sapphire single crystals were implanted at room temperature with 180 keV manganese ions to fluences up to 1.8 × 10¹⁷ cm⁻². The samples were annealed at 1000 °C in oxidizing or reducing atmosphere. Surface damage was observed after implantation of low fluences, the amorphous phase being observed after implantation of 5 × 10¹⁶ cm⁻², as seen by Rutherford backscattering spectroscopy under channelling conditions. Thermal treatments in air annealed most of the implantation related defects and promoted the redistribution of the manganese ions, in a mixed oxide phase. X-ray diffraction studies revealed the presence of MnAl₂O₄. On the contrary, similar heat treatments in vacuum led to enhanced out diffusion of Mn while the matrix remained highly damaged. The analysis of laser induced luminescence performed after implantation showed the presence of an intense red emission.