A new transparent microwave absorbing coating was developed by compounding 1-butyl-3-methyl imidazolium tetrafluoroborate (bmim.BF 4 ) ionic liquid (IL) with diglycidyl ether of bisphenol A-type epoxy resin. The systems were crosslinked with the IL alone or combined with conventional hardeners, as anhydride or aromatic amine. The curing behavior was investigated by thermal and spectroscopic analysis performed at high temperatures. Neat bmim.BF 4 was able to cure epoxy resin, giving rise to networks with outstanding thermal stability compared with the systems cured with anhydride or aromatic amine. bmim.BF 4 accelerated the curing process in the presence of aromatic amine but retarded this event when anhydride was used as an external curing agent. The glass-transition temperature evaluated by dynamic mechanical analysis decreased when the amount of IL increased, which can be attributed to side reactions during the curing process, as well as the plasticizing effect of IL. The epoxy networks cured with bmim.BF 4 alone or in combination with anhydride or aromatic amine were transparent and presented considerable microwave absorbing properties in the X-band frequency range (8-12 GHz), being the best performance observed for the systems cured with bmim.BF4/anhydride curing system, with reflection loss value around −16 dB at 11.3 GHz.

No abstract

Rev. Bras. Saúde Prod. Anim., Salvador, v.15, n.4, p.947-956 out./dez., 2014

The dynamic vulcanization technique is a process of crosslinking an elastomer during mixing with a molten state thermoplastic, resulting in a new class of thermoplastic elastomers (TPEs): vulcanized thermoplastics (TPVs). This technique obtains materials with rubber behavior at room temperature, but processed as plastics at high temperatures, especially by extrusion and injection. The advantage of using the process of obtaining thermoplastic elastomers is that traditional elastomers require several steps in their processing. From an environmental point of view, vulcanized thermoplastics are interesting, since these materials keep their properties practically unchanged with direct recycling, without the need for any treatments. The objective of this work was to develop a new system of reactive compatibilization for the PP/NBR mixture, by means of the click chemistry technique by the reaction of the thiol-ene type, using as a compatibilizing agent the addition of EVASH (Poli (ethylene-co-alcoholicvinyl)-co-mercapto-vinyl acetate), resulting from the chemical modification of EVA (poly (acrylonitrile-co-butadiene)) with mercaptan groups by transesterification. The ionic liquid acted as a catalyst, optimizing the transesterification reaction of EVA, to obtain EVASH with a greater presence of -SH to EVA, obtaining more rigid systems due to the click thiol-ene bond.

Natural fibers have been extensively studied as a reinforcement filler in obtaining composites, replacing partially synthetic fibers. The vast majority of these materials originate from agro-industrial waste with a high content of lignin and cellulose making it a very interesting material with low cost and good mechanical properties. The purpose of the study was to obtain a composite based on alkyl ketene dimer resin, for the manufacture of sustainable packaging, made of paper by adding a 10% (w/w) con-tent of green coconut fiber and sugarcane bagasse fiber, and evaluated the impact of the filler on the mechanical behavior of the systems. The studied material was characterized from mechanical tests, such as Ring Crush Test (RCT) and Concora Medium Test (CMT) evaluating the maximum resistance supported by centimeter in the pre-pared composites, by the specimens. Through the RCT tests, with 10% w/w fibers, it was possible to verify that the fiber from sugarcane bagasse reached an increase of about 1% in the reinforcement effect compared to pure paper, and a difference of up to 2% in strength mechanics in relation to coir fiber, and CMT tests shows the reinforcement effect of the presence of sugarcane bagasse fiber, with an increase of about 3% compared to pure paper, and with a mechanical strength higher by 1% compared to coconut fiber. Therefore, the study was funneled with sugar cane fiber, varying the content by 20 and 30 % (w/w), evaluating the impact on the dispersion of this filler in the polymeric matrix and, consequently, the mechanical response of the composite with these compositions. The conclusion of the study was that the system prepared with 20% (w/w) was the one that achieved the greatest optimization of the mechanical properties, evaluated by the tests. This type of material can be applied to obtain cardboard boxes with resistance to high loads, due to the achievement of good mechanical properties.