Influencia del proceso de reciclado sobre las propiedades de los materiales compuestos obtenidos por inyección de poliestireno reforzado con fibras lignocelulósicas

The objective of this research is to study the influence of several recycling cycles on the mechanical properties of four different materials made by the injection of polystyrene. The four materials studied have different characteristics. The first one is polystyrene (PS), the second one is polystyrene reinforced with hemp fibers (PSf), the third one is polystyrene reinforced with hemp fibers modified with AKD (PSft) and the last one is polystyrene reinforced with fiberglass (PSfv). With all these materials tensile strength, bending, hardness and impact is measured. After the measurement of these physical properties, materials are recycled to obtain new injection samples, and its physical properties are measured again. This process is repeated during 24 cycles. After each recycling cycle material physical properties are related with polystyrene molecular weight, melt flow, FTIR spectra and DSC. From reinforced materials, fibers are recovered and through microscopy and image analysis they are characterized to study the influence that recycling has on its structure.

Impacto tributario de la implementación en el Ecuador de las Normas Internacionales de Información Financiera, (NIIF) y las Normas Internacionales de Contabilidad, (NIC) en las empresas comerciales: caso de una empresa dedicada a la venta de productos homeopáticos y naturales

Las Normas Internacionales de Información Financiera (NIIF) son estándares de contabilización que establecen el tipo de información que se debe presentar conjuntamente con los Estados Financieros y su forma de contabilización. El Ecuador en el año 2006 por resolución de la Superintendencia de Compañías decidió adoptar dicha normativa, por lo que se estableció plazos para que los empresarios del país adopten e implementen las NIIF de carácter obligatorio. El 20 de noviembre del 2008 la Superintendencia de Compañías emite la resolución Nº 08.G.DSC para prorrogar la vigencia de las Normas Internacionales de Información Financiera por la crisis financiera global. Por lo que estableció un cronograma escalonado por grupos de aplicación obligatorio dividiendo en tres grupos: - El primero conformado por las empresas auditoras y compañías inscritas en el Registro de Mercado de Valores: el período de aplicación a partir de enero 2010. - El segundo grupo aplicará a partir del 1 de enero del 2011 son las compañías que tengan activos totales iguales o superiores a $ 4’000.000,00 al 31 de diciembre del 2007, las compañías tenedoras de acciones o Holding, las compañías de economía mixta y entidades del Sector Público; las sucursales de compañías extranjeras u otras empresas extranjeras. - El tercer grupo que aplicarán a partir del año 2012 conformado por las compañías no consideradas en los dos grupos anteriores. En el Ecuador la implementación de las Normas Internacionales de Información Financiera (NIIF) y las Normas Internacionales de Contabilidad (NIC) han tenido una expectativa muy grande tanto por los gerentes de las empresas como por las personas involucradas, ya que existen muchas interrogantes respecto al proceso de implementación de las NIIF y NIC.

Análisis del proceso de implementación de las normas de información financiera - NIIF e identificación de las ventajas y beneficios de su aplicación en importantes organizaciones ecuatorianas del sector industrial

Mediante Resolución No. 08.G.DSC.010 del 20 de noviembre del 2008 (Registro Oficial No. 498 del 31 de diciembre del 2008), la Superintendencia de Compañías resolvió establecer un cronograma escalonado de aplicación obligatoria de las Normas Internacionales de Información Financiera - NIIF por parte de las compañías ecuatorianas y entes sujetos al control y vigilancia de la misma. El cronograma establecido determinó a tres grupos de aplicación; el primer grupo constituido por las compañías reguladas por la Ley de Mercado de Valores y Auditoras Externas cuyo año de implementación fue el 2010; el segundo grupo conformado por las compañías cuyos activos superaban los USD$4 millones al 31 de diciembre del 2007, entidades de economía mixta, sector público y sucursales de compañías extranjeras cuyo año de implementación fue el 2011; y todas las demás compañías cuyo año de implementación fue el 2012. A la fecha de presentación de este trabajo de investigación, la gran mayoría de las compañías ecuatorianas han culminado el proceso de adopción a las NIIF como su normativa contable, es por tal motivo que este trabajo de investigación toma relevancia, al enfocarse en analizar e investigar cuáles han sido los ajustes más importantes y comunes realizados por las compañías ecuatorianas del sector industrial seleccionadas durante este proceso de conversión de normativa contable, así como también cuáles fueron las principales dificultades que debieron afrontar durante el proceso de implementación y los beneficios y ventajas más importantes que están teniendo estas compañías post implementación de las NIIF.

Análisis práctico de la aplicación de las normas internacionales de contabilidad “propiedad, planta y equipo" y “deterioro del valor de los activos” NIC 16 y NIC 36, en el año 2011 y su impacto tributario

La Superintendencia de Compañías, Valores y Seguros, a través de la Resolución No. 06.Q.ICI-004 de 21 de agosto de 2006, adoptó las Normas Internacionales de Información Financiera “NIIF” y dispuso su aplicación obligatoria por parte de las entidades sujetas a su control y vigilancia de la Superintendencia, en este sentido estableció un cronograma de implementación de dichas normas mediante Resolución 08.G.DSC.010 de 20 de noviembre de 2008, en la que se establecieron tres grupos de aplicación a partir del año 2010, 2011 y 2012. Con estas disposiciones, a partir del año 2012 absolutamente todas las compañías sujetas al control por parte de la Superintendencia de Compañías, Valores y Seguros, debieron registrar sus estados financieros bajo las referidas normas contables, las cuales permiten obtener información financiera transparente y uniforme, que sirve para la toma de decisiones a los usuarios de esos estados financieros. Un rubro importante que se presenta en los estados financieros, sin duda son la propiedad, planta y equipo, cuyo tratamiento contable se encuentra en las NIC 16 y NIC 36, esta última en cuanto al reconocimiento del deterioro, mientras que tributariamente, la Ley Orgánica de Régimen Tributario Interno y el Reglamento para la Aplicación de la Ley Orgánica de Régimen Tributario Interno, establecen el cumplimiento de ciertas condiciones para que las depreciaciones de esa propiedad, planta y equipo, sea deducibles a efectos del Impuesto a la Renta. En este sentido tanto la norma contable (Superintendencia de Compañías, Valores y Seguros) como la norma tributaria (Servicio de Rentas Internas), con el pasar del tiempo confluyen hacia tratamientos contables y tributarios que permiten a las compañías una mejor conciliación entre las mismas, como es el caso del Reglamento a la Ley orgánica de Incentivos a la Producción y Prevención de Fraude Fiscal, publicado en el R.O. No. 407 de 31 de diciembre de 2014, que permite el reconocimiento de activos y pasivos por impuestos diferidos en ciertos casos y condiciones, que de acuerdo a la norma contable deben registrarse.

Composition and cure temperature: The influence on properties of final flexible PU cold cure foam parts

Foams are cellular structures, produced by gas bubbles formed during the polyurethane polymerization mixture. Flexible PU foams meet the following two criteria: have a limited resistance to an applied load, being both permeable to air and reversibly deformable. There are two main types of flexible foams, hot and cold cure foams differing in composition and processing temperatures. The hot cure foams are widely applied and represent the main composition of actual foams, while cold cure foams present several processing and property advantages, e.g, faster demoulding time, better humid aging properties and more versatility, as hardness variation with index changes are greater than with hot cure foams. The processing of cold cure foams also is attractive due to the low energy consumption (mould temperature from 30 degrees to 65 degrees C) comparatively to hot cure foams (mould temperature from 30 degrees to 250 degrees C). Another advantage is the high variety of soft materials for low temperature processing moulds. Cold cure foams are diphenylmethane diisocyanate (MDI) based while hot cure foams are toluene diisocyanate (TDI) based. This study is concerned with Viscoelastic flexible foams MDI based for medical applications. Differential Scanning Calorimetry (DSC) was used to characterize the cure kinetics and Dynamical Mechanical Analisys to collect mechanical data. The data obtained from these two experimental procedures were analyzed and associated to establish processing/properties/operation conditions relationships. These maps for the selection of optimized processing/properties/operation conditions are important to achieve better final part properties at lower costs and lead times.

Factors influencing the dissolution of phosphate rock in a range of high P-fixing soils from Cameroon

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo-Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)- sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg 21 soil and incubated at 30 degrees C for 85 days. Dissolution of the PRs was determined at various intervals using the Delta NaOH-P method ( the difference of the amount of P extracted by 0.5 M NaOH between the PR-treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH-(H2O), < 5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH-(H2O) > 5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P At B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.

Synthesis and characterization of fluorescent poly(aromatic amide) dendrimers

The synthesis of a series of poly(aromatic amide) dendrimers up to the second generation is described herein. The AB, building block used throughout the synthesis of the dendrimers was the allyl ester of 3,5-diaminocinnamic acid, which has been synthesized from 3,5-dinitrobenzoic acid in good yield with use of a four-step procedure. Dendron synthesis was achieved via a convergent approach with use of a sequence of deprotection/coupling steps. Two commercially available alcohols, L-menthol and citronellol, were coupled to the AB(2) monomer by using an alkyl diacid spacer and two core units; 1,7-diaminoheptane and tris(2-aminoethyl)amine have been used to produce the final dendrimers. Characterization was carried out by NMR and IR spectroscopies, MALDI-TOF mass spectrometry, GPC, and DSC. The novel monomer and dendritic derivatives exhibited a strong fluorescence emission in the visible region (lambda approximate to 500 nm) of the spectrum and a weak emission in the near-infrared (lambda approximate to 850 nm) upon excitation in the near-UV region. The fluorescence emission characteristics were found to be solvent and dendrimer generation dependent.

Alternative syntheses of linear polyurethanes using masked isocyanate monomers

A range of linear polyurethanes featuring aliphatic, aromatic and ether residues have been prepared by co-polymerisation of novel 'masked' isocyanate A(2)-type monomers and diols. The reactive isocyanate monomers were generated in situ via the triphenylphosphine mediated decomposition of the heterocyclic disulfide, 1,2,4-dithiazolidine-3,5-dione. Two different synthetic approaches were examined and assessed for the construction of the novel A(2)-type monomers, which involved either coupling two 1,2,4-dithiazolidine-3,5-diones together through a spacer group or construction of 1,2,4-dithiazolidine-3,5-diones directly from diamines. The resulting polyurethanes were purified via solvent extraction and analysed using GPC, NMR and IR spectroscopic analyses. Molecular weight data were obtained and compared from both GPC and H-1 NMR (via end-group analysis) spectroscopic analysis. The thermal properties of the polyurethanes were determined using DSC and their solubility in common aprotic organic solvents was also assessed and related to their structural composition. (c) 2006 Elsevier B.V. All rights reserved.

Enthalpy-driven ring-opening polymerization of highly strained macrocyclic biaryl-ether-ketones

Highly strained macrocyclic ether-ketones obtained by nickel-catalyzed cyclization of linear precursor oligomers undergo ring-opening polyinerization via ether exchange in the presence of nucleophilic initiators such as fluoride or phenoxide anions. Strain enthapies of these macrocycles, from DSC analyses of their exothermic ring-opening polymerization are in the range 50-90 kJ mol(-1). Melt-phase polymerization generally affords slightly cross-linked materials, but solution-phase polymerization at high macrocycle concentrations gives fully soluble, high molar mass polymers with inherent viscosities of up to 1.78 dL g(-1). Sequence-analysis of the resulting polymers by C-13 NMR shows that alternating or random monomer sequences may be obtained, depending on whether one or both aromatic rings adjacent to the ether linkages are activated toward nucleophilic attack.

Low molecular weight organogelators from self-assembling synthetic tripeptides with coded amino acids: morphological, structural, thermodynamic and spectroscopic investigations

A series of self-assembling terminally blocked tripeptides (containing coded amino acids) form gels in various aromatic solvents including benzene, toluene, xylenes at low concentrations. However these tripeptides do not form gels in aliphatic hydrocarbons like n-hexane, cyclohexane, n-decane etc. Morphological studies of the dried gel indicate the presence of an entangled fibrous network, which is responsible for gelation. Differential scanning calorimetric (DSC) studies of the gels produced by peptide 1 clearly demonstrates thermoreversible nature of the gel and tripeptide-solvent complex may be produced during gel formation. FT-IR and H-1 NMR studies of the gels demonstrate that an intermolecular hydrogen-bonding network is formed during gelation. Single crystal X-ray diffraction studies for peptides 1, 2 and 3 have been performed to investigate the molecular arrangement that might be responsible for forming the fibrous network of these self-assembling peptide gelators. It has been found that the morph responsible for gelation of peptides 1, 2 and 3 in benzene is somewhat different from that of its xerogel.

Crystallization in poly(L-lactide)-b-poly(epsilon-caprolactone) double crystalline diblock copolymers: a study using X-ray scattering, differential scanning calorimetry, and polarized optical microscopy

The crystallization of well-defined poly(L-lactide)-b-poly(epsilon-caprolactone) diblock copolymers, PLLA-b-PCL, was investigated by time-resolved X-ray techniques, polarized optical microscopy (POM), and differential scanning calorimetry (DSC). Two compositions were studied that contained 44 and 60 wt % poly(L-lactide), PLLA (they are referred to as (L44C5614)-C-11 and (L60C409)-C-12, respectively, with the molecular weight of each block in kg/mol as superscript). The copolymers were found to be initially miscible in the melt according to small-angle X-ray scattering measurements (SAXS). Their thermal behavior was also indicative of samples whose crystallization proceeds from a mixed melt. Sequential isothermal crystallization from the melt at 100 degreesC (for 30 min) and then at 30 degreesC (for 15 min) was measured. At 100 degreesC only the PLLA block is capable of crystallization, and its crystallization kinetics was followed by both WAXS and DSC; comparable results were obtained that indicated an instantaneous nucleation with three-dimensional superstructures (Avrami index of approximately 3). The spherulitic nature of the superstructure was confirmed by POM. When the temperature was decreased to 30 degreesC, the PCL block was able to crystallize within the PLLA negative spherulites (with an Avrami index of 2, as opposed to 3 in homo-PCL), and its crystallization rate was much slower than an equivalent homo-PCL. Time-resolved SAXS experiments in (L60C409)-C-12 revealed an initial melt mixed morphology at 165 degreesC that upon cooling transformed into a transient microphase-separated lamellar structure prior to crystallization at 100 degreesC.

Melt structure and its transformation by sequential crystallization of the two blocks within poly(L-lactide)-block-poly(epsilon-caprolactone) double crystalline diblock copolymers

Sequential crystallization of poly(L-lactide) (PLLA) followed by poly(epsilon-caprolactone) (PCL) in double crystalline PLLA-b-PCL diblock copolymers is studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). Three samples with different compositions are studied. The sample with the shortest PLLA block (32 wt.-% PLLA) crystallizes from a homogeneous melt, the other two (with 44 and 60% PLLA) from microphase separated structures. The microphase structure of the melt is changed as PLLA crystallizes at 122 degrees C (a temperature at which the PCL block is molten) forming spherulites regardless of composition, even with 32% PLLA. SAXS indicates that a lamellar structure with a different periodicity than that obtained in the melt forms (for melt segregated samples). Where PCL is the majority block, PCL crystallization at 42 degrees C following PLLA crystallization leads to rearrangement of the lamellar structure, as observed by SAXS, possibly due to local melting at the interphases between domains. POM results showed that PCL crystallizes within previously formed PLLA spherulites. WAXS data indicate that the PLLA unit cell is modified by crystallization of PCL, at least for the two majority PCL samples. The PCL minority sample did not crystallize at 42 degrees C (well below the PCL homopolymer crystallization temperature), pointing to the influence of pre-crystallization of PLLA on PCL crystallization, although it did crystallize at lower temperature. Crystallization kinetics were examined by DSC and WAXS, with good agreement in general. The crystallization rate of PLLA decreased with increase in PCL content in the copolymers. The crystallization rate of PCL decreased with increasing PLLA content. The Avrami exponents were in general depressed for both components in the block copolymers compared to the parent homopolymers. Polarized optical micrographs during isothermal crystalli zation of (a) homo-PLLA, (b) homo-PCL, (c) and (d) block copolymer after 30 min at 122 degrees C and after 15 min at 42 degrees C.

Water-soluble, unimolecular containers based on amphiphilic multiarm star block copolymers

A new class of water-soluble, amphiphilic star block copolymers with a large number of arms was prepared by sequential atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) and poly( ethylene glycol) methyl ether methacrylate (PEGMA). As the macroinitiator for the ATRP, a 2-bromoisobutyric acid functionalized fourth-generation hyperbranched polyester (Boltorn H40) was used, which allowed the preparation of star polymers that contained on average 20 diblock copolymer arms. The synthetic concept was validated by AFM experiments, which allowed direct visualization of single molecules of the multiarm star block copolymers. DSC and SAXS experiments on bulk samples suggested a microphase-separated structure, in agreement with the core-shell architecture of the polymers. SAXS experiments on aqueous solutions indicated that the star block copolymers can be regarded as unimolecular micelles composed of a PBMA core and a diffuse PPEGMA corona. The ability of the polymers to encapsulate and release hydrophobic guests was evaluated using H-1 NMR spectroscopy. In dilute aqueous solution, these polymers act as unimolecular containers that can be loaded with up to 27 wt % hydrophobic guest molecules.

Polymorphism in [Co(SCN)(4)(ppz-H)(2)] (ppz, piperazine)

A one-pot reaction of [Co(NO3)(2)center dot 6H(2)O and piperazine] with NH4SCN/NaSCN in water-methanol (1:1) solvent leads to two polymorphs of [Co(SCN)(4)(ppz-H)(2)] (ppz, piperazine) (I and II). X-ray crystal structure reveals both have same space group but the differences in the alignment of pendant SCN- leads to two polymorphs. In I, trifurcated N-H...S hydrogen bonding plays a prominent role in crystal packing leading to S...S interactions between SCN fragments but in II, no such trifurcation arises and thereby the crystal packing occurs through hydrogen bonding interactions only leading to a distinctly different network topology. TG/DSC and FT-IR study reveal they are enantiotropically related. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of sequence distribution on the morphology, crystallization, melting, and biodegradation of poly(epsilon-caprolactone-co-epsilon-caprolactam) copolymers

Two types of poly(epsilon-caprolactone (CLo)-co-poly(epsilon-caprolactam (CLa)) copolymers were prepared by catalyzed hydrolytic ring-opening polymerization. Both cyclic comonomers were added simultaneously in the reaction medium for the First type or materials where copolymers have a random distribution of counits, as evidenced by H-1 and C-13 NMR. For the second type of copolymers, the cyclic comonomers were added sequentially, yielding diblock poly(ester-amides). The materials were characterized by differential scanning calorimetry (DSC), wide- and small-angle X-ray scattering (WAXS and SAXS), and transmission and scanning electron microscopies (TEM and SEM). Their biodegradation in compost was also studied. All copolymers were found to be miscible by the absence of structure in the melt. TEM revealed that all samples exhibited a crystalline lamellar morphology. DSC and WAXS showed that in a wide composition range (CLo contents from 6 to 55%) only the CLa units were capable of crystallization in the random copolymers. The block copolymer samples only experience a small reduction of crystallization and melting temperature with composition, and this was attributed to a dilution effect caused by the miscible noncrystalline CLo units. The comparison between block and random copolymers provided a unique opportunity to distinguish the dilution effect of the CLo units on the crystallization and melting of the polyamide phase from the chemical composition effect in the random copolymers case, where the CLa sequences are interrupted statistically by the CLo units, making the crystallization of the polyamide strongly composition dependent. Finally, the enzymatic degradation of the copolymers in composted soil indicate a synergistic behavior where much faster degradation was obtained for random copolymers witha CLo content larger than 30% than for neat PCL.