Hugo Alberto Destéfanis

Barrier Properties and Structural Study of Nanocomposite of HDPE/Montmorillonite Modified with Polyvinylalcohol

In this work was studied the permeation of CO2 in films of high-density polyethylene (HDPE) and organoclay modified with polyvinylalcohol () obtained from melt blending. Permeation study showed that the incorporation of the modified organoclay generates a significant effect on the barrier properties of HDPE. When a load of 2 wt% of was incorporated in the polymer matrix, the flow of CO2 decreased 43.7% compared to pure polyethylene. The results of TEM showed that clay layers were dispersed in the polymeric matrix, obtaining an exfoliated-structure nanocomposite. The thermal stability of nanocomposite was significantly enhanced with respect to the pristine HDPE. DSC results showed that the crystallinity was maintained as the pure polymeric matrix. Consequently, the decrease of permeability was attributable only to the effect of tortuosity generated by the dispersion of . Notably the mechanical properties remain equal to those of pure polyethylene, but with an increase in barrier properties to CO2. This procedure allows obtaining nanocomposites of HDPE with a good barrier property to CO2 which would make it competitive in the use of packaging.

Preparation op metal borides in an aprotic system

Abstract A novel technique to prepare Nickel Borides using Diborane-THF complex generated “in-situ” as reducing agent, is presented. The Nickel Bondes series were prepared using two ways, the HETEROGENEOUS and HOMOGENEOUS route. Solid NiCls of different mesh size was added to the reducing complex to prepare nickel boride by HETEROGENEOUS route. While Ni(AcO) 2 ·4H 2 O dissolved in methanol was used to obtain nickel boride by the HOMOGENEOUS one. The advantage of this technique is that by using an aprotic medium, borides of metals which form stable oxoanions are obtained.

Effect of the Organoclay Preparation on the Extent of the Intercalation/Exfoliation and the Barrier Properties in Polyamide-6/Montmorillonite Nanocomposites

This paper shows the importance of the clay surface chemistry in the preparation of nanocomposite materials. An Argentinean montmorillonite was used for preparing two modified clays. The filosilicate was intercalated with a quaternary ammonium salt derived from ε- caprolactam to obtain an organofilic material. The other modification was introduced by mixing the clay with hexadecyl trimethyl ammonium chloride. Thus, the polyamide 6 ability in dispersing clays was applied to prepare composites with the intercalated clays. The polyamide 6/clay dry composites with 3 wt % of filler were prepared by melt processing in a mixer chamber. Composites of polyamide 6/organoclay were characterized by X-ray diffraction, transmission and scanning electron microscopy and thermogravimetry. The barrier properties were determined by cyclohexane pervaporation. The results show that the dispersion and degree of delamination depend on a proper chemical treatment and the clay content influences the polyamide 6 nanocomposites solvent pervaporation resistance.

α-Amylase Aspergillus oryzae Immobilized on Modified Expanded Perlite

Abstract The α-amylase from Aspergillus oryzae was immobilized covalently onto expanded perlite (EP) and modified EP by treatment with TiO2 (EP-TiO2), dye HE3B (EP-HE3B) polyethylene terephthalate (PET)-hydrazide (EP-PET) and magnetite (EP-magnetite). The modified EP was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The supports were functionalized with aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA). The optimum pH for free and immobilized α-amylase was 5.5. Temperature of maximum activity for free enzyme and immobilized enzyme on EP-HE3B was 50°C. The immobilized enzyme in EP-APTES this value was 55°C. The immobilized α-amylase in EP-APTES and EP-HE3B-APTES exhibited better thermostability than free enzyme. The immobilized derivatives showed moderate operational stability by retaining 50% of initial activity after seven successive reuses.