Blends of polyamide 6 and epichlorohydrin elastomers. II. Thermal, dynamic mechanical, and mechanical properties

The mechanical blending of polyamide 6 and epichlorohydrin elastomers, polyepichlorohydrin, PEPI, and poly(epichlorohydrin-co-ethylene oxide), EGO, is accompanied by grafting copolymerization. In this work the influence of the graft copolymer on the thermal and mechanical properties of the blends is investigated. The blends are immiscible and the crystallinity degree normalized to the polyamide 6 contents in the blends is higher than expected. The X-ray diffraction results show that the grafting copolymer is also crystalline; hence, the presence of crystalline phase of copolymer can be responsible for the apparent enhancement of crystallinity. The DMA analysis reveals the presence of a shoulder in the peak corresponding to the PA 6 glass transition, as observed by loss modulus curves, which was assigned to relaxations of the grafting copolymer. Tensile tests show that the blends are more fragile than the PA 6, despite the graft copolymer. These results were attributed to the mechanical fragile interface constituted by a network type structure of the graft copolymer. (C) 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1835-1841, 1999.72141835184

Blends of polyamide 6 and epichlorohydrin elastomers. I. Graft copolymerization in the melt blending

With the purpose of improving the mechanical properties of the polyamides, the possibility of combining polyamides with elastomers has been used. The low compatibility of the resulting blends leads to deficient mechanical properties, and therefore, it is necessary to add the compatibilizer to the mixture or to produce the compatibilizer during the melting mixture. Usually, at least one of the components must contain a reactive functional groups. In the present work, blends of polyamide 6 (PA 6) and epichlorohydrin elastomers, polyepichlorohydrin (PEPI), and the equimolar copolymer poly(epichlorohydrin-co-ethylene oxide), EGO, with different compositions were prepared by mechanical mixture using a Banbury-type mixer. The blends were characterized by rheological measurements, the Molau test, elemental analysis, Infrared Spectroscopy by Diffuse Reflectance, Transmission Electron Microscopy, and X-ray Diffractometry. The blends of PA 6 with PEPI and ECO are heterogeneous, showing a morphology of elastomer particles dispersed in the polyamide matrix. The results of rheological measurements and the Molau test indicate a graft copolymerization in the interface between the polyamide and the elastomer, PA 6-g-elastomer, whose concentration decreases with the elastomer content. It was found that the grafting of PEPI and PA 6 changed the diffraction pattern of PA 6. (C) 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1827-1833, 1999.72141827183

Central nervous system involvement in experimental infection with Leishmania (Leishmania) amazonensis

We describe the pathologic alterations of the central nervous system (CNS) observed in experimental tegumentary leishmaniasis in BALB/c and Swiss mice. The mice were subcutaneously infected with 10(4) amastigotes of Leishmania (Leishmania) amazonensis. Animals were killed and brains were removed for histologic and immunocytochemical studies. Histologic examination showed that 66.6% of infected mice had a discrete hyperemia and inflammatory infiltrate in the meninges, composed of mononuclear cells and neutrophils with no detectable parasites. However, parasitized macrophages were detected in the cerebral parenchyma, as well as mast cells, lymphocytes, and polymorphonuclear cells. Necrosis in the cerebral parenchyma was also observed. Confocal fluorescence microscopy showed that CD8(+) T lymphocytes are the major component of the inflammatory infiltrate in the CNS. In addition to these cells, CD4(+), CD11b, and dendritic cells are present, in small numbers, in the inflammatory processes of the CNS. Thus, L. amazonensis is able to cross the blood-brain barrier and cause significant pathologic changes in the CNS.Univ Estadual Maranhao, Dept Patol, Maranhao, BrazilFiocruz MS, Inst Oswaldo Cruz, Lab Imunomodulacao, Dept Protozool, BR-21045900 Rio De Janeiro, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Morfol, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Microbiol Immunol & Parasitol, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Morfol, Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Microbiol Immunol & Parasitol, Sao Paulo, BrazilWeb of Scienc