Studies on Rubber-to-Nylon Tire Cord Bonding

ABSTRACT: Nylon tire cord (1680/2) was dipped in different adhesives based on resorcinol formaldehyde resin and latex (RFL) and was bonded to natural rubber-based compounds. The resin-rubber ratio in the RFL adhesive was optimized. The variation of pull-through load was studied by varying the drying and curing temperature of the dipped nylon tire cord. RFL adhesive based on vinylpyridine latex was found to have better rubber-to-nylon tire cord bonding, compared with the one based on natural rubber latex. Addition of a formaldehyde donor into the RFL adhesive/rubber compound improves adhesion.

Studies on adhesives for bonding rubber to rubber and rubber to textiles

The primary objective of this investigation has been to develop more efficient and low cost adhesives for bonding various elastomer combinations particularly NR to NR, NR/PB to NR/PB, CR to CR,NR to CR and NR to NBR.A significant achievement of the investigation was the development of solventless and environment friendly solid adhesives for NR to NR and NR/PB to NR/PB particularly for precured retreading. Conventionally used adhesives in this area are mostly NR based adhesive strips in the presence of a dough. The study has shown that an ultra accelerator could be added to the dough just before applying it on the tire which can significantly bring down the retreading time resulting in prolonged tire service and lower energy consumption. Further latex reclaim has been used for the preparation of the solid strip which can reduce the cost considerably.Another significant finding was that by making proper selection of the RF resin, the efficiency and shelflife of the RFL adhesive used for nylon and rayon tire cord dipping can be improved. In the conventionally used RFL adhesive, the resin once prepared has to be added to the latex within 30 minutes and the RFL has to be used after 4 hours maturation time maximum shelf life of the RFL dip solution being 72 hours. In this study a formaldehyde deficient resin was used and hence more flexibility was available for mixing with latex and maturing. It also has a much longer shelf life. In the method suggested in this study, formaldehyde donors were added only in the rubber compound to make up the formaldehyde deficiency in the RFL. The results of this investigation show that the pull through load by employing this method and the conventional method are comparable. This study has also shown that the amount of RF resin with RFL adhesive can be partially replaced by other modifying agents for cost reduction.Cashew nut shell liquid (CNSL) resin can be employed for improving the bonding of dipped nylon and rayon cord with NR.Since CNSL resin cannot be added in the dip solution since it is not soluble in water, it was added in the rubber compound. The amount of wood rosin in the rubber compound can be reduced by using CNSL resin.Another interesting result of the investigation was the use of CR based adhesive modified with chlorinated natural rubber for CR to CR bonding. Addition of chlorinated natural rubber was found to improve sea water resistance of CR based adhesive. In the bonding of a polar rubber like nitrile rubber or polychloroprene rubber to a non polar rubber like natural rubber, an adhesive based on polychloroprene rubber was found to be effective.

Novel adhesive systems based on neoprene-phenolic blends

The aim of the investigation is to develop new high performance adhesive systems based on neoprene-phenolic blends. Initially the effect of addition of all possible ingredients like fillers, adhesion promoters, curing agents and their optimum compositions to neoprene solution is investigated. The phenolic resin used is a copolymer of phenol-cardanolformaldehyde prepared in the laboratory. The optimum ratio between phenol and cardanol that gives the maximum bond strength in metal-metal, rubber-rubber and rubber-metal specimens has been identified. Further the ratio between total phenols and formaldehyde is also optimised. The above adhesive system is further modified by the addition of epoxidized phenolic novolacs. For this purpose, phenolic novolac resins are prepared in different stoichiometric ratios and are subsequently epoxidized. The effectiveness of the adhesive for bonding different metal and rubber substrates is another part of the study. To study the ageing behaviour, different bonded specimens are exposed to high temperature, hot water and salt water and adhesive properties have been evaluated. The synthesized resins have been characterized by FTIR , HNMR spectroscopy. The molecular weights of the resins have been obtained by GPC. Thermogravimetric analysis and differential scanning calorimetry are used to study the thermal properties. The fractured surface analysis is studied by scanning electron microscopy. The study has brought to light the influence of phenol/ formaldehyde stoichiometric ratio, addition of cardanol (a renewable resource), adhesion promoters and suitability of the adhesive for different substrates and the age resistance of adhesive joints among other things.

Novel applications of cashew nut shell liquid in the polymer field

This research project aims at developing new applications for CNSL in the polymer field. Cashew nut shell liquid (CNSL) is a cheap agro-byproduct and renewable resource which consists mainly of substituted phenols. By using CNSL in place of phenol, phenol derived from petrochemicals can be conserved and a cheap agro-byproduct utilized.In this study CNSL based resin is prepared by condensing a mixture of phenol and CNSL with hexamethylenetetramine and the effect of P: F ratio and CNSL: P ratio on the properties of synthesized resin is studied. The adhesive properties of CNSL based resin in combination with neoprene rubber are investigated. The effect of varying the stoichiometric ratios between total phenol and formaldehyde and CNSL and phenol of the resin, resin content, choice and extent of fillers and adhesion promoters in the adhesive formulation are studied. The effect of resin on the ageing properties of various elastomers is also studied by following changes in tensile strength, elongation at break, modulus, tear strength, swelling index and acetone soluble matter. Crude CNSL and resins with different P: F ratios and CNSL: P ratios are incorporated into elastomers. Lastly, utility of CNSL based resin as binder for making particleboard is investigated.The results show that CNSL based resin is an effective ingredient in adhesives for bonding aluminium to aluminium. The resin used for adhesive fonnulation gives the best performance at 45 to 55 phr resin and a total phenol: formaldehyde of l:2.9. The resin when added at a rate of l5 phr improves ageing characteristics of elastomers with respect to mechanical properties. The reaction mixture of CNSL and hexa and the resin resulting from the condensation of CN SL, phenol and hexa can be used as effective binders for moulding particleboard.

Short Nylon-6 Fibre/Rubber-Toughened Polystyrene Composites

The thesis describes studies on development of short Nylon-6 fibre composites based on rubber-toughened polystyrene (PS). Toughening was done using natural rubber (NR), styrene-butadiene rubber (SBR) and whole tyre reclaim (WTR). The composites were prepared by melt mixing in an internal mixer at 170 oC. It was found that the optimum blend ratio was 85/15 for PS/NR, 90/10 for PS/SBR and 90/22 for PS/WTR blends. The effect of dynamic vulcanisation on 85/15 PS/NR and 90/10 PS/SBR blends using dicumyl peroxide (DCP) at various concentrations were also studied. The dynamic crosslinking improved the tensile properties, flexural properties, impact strength and dynamic mechanical properties of both the blends. The effect of unmodified and resorcinol formaldehyde latex (RFL)-coated short Nylon-6 fibres on the mechanical properties, morphology and dynamic mechanical properties of 85/15 PS/NR, 90/10 PS/SBR and 90/22 PS/WTR blends were studied. Fibre loading was varied from 0 to 3 wt.%. For 85/15 PS/NR blend, there was a significant enhancement in tensile properties, flexural properties and impact strength with 1 wt.% of both unmodified and RFL-coated fibres. Dynamic mechanical analysis revealed that the storage modulus at room temperature was maximum at 1 wt.% fiber loading for both composites. The surface functionality of the fiber was improved by giving alkali treatment. Maleic anhydride-grafted-polystyrene (MA-g-PS) was prepared and used as a compatibiliser. The effect of MA-g-PS on the composites was investigated with respect to mechanical properties, morphology and dynamic mechanical properties. The compatibiliser loading was varied from 0 to 2 wt.%. The properties were enhanced significantly in the case of treated and untreated fibre composites at a compatibiliser loading of 0.75 wt.%. SEM analysis confirmed better bonding between the fibre and the matrix. Dynamic mechanical studies showed that the storage modulus at room temperature improved for treated fibre composites in the presence of compatibiliser. In the case of 90/10 PS/SBR composites, the addition of short Nylon-6 fibres at 1 wt.% loading improved the tensile modulus, flexural properties and impact strength while the tensile strength was marginally reduced. The surface treated fibers along with compatibiliser at 0.5 wt.% improved the tensile properties, flexural properties and impact strength. DMA reveale that the storage modulus at room temperature was better for composites containing untreated fibre and the compatibiliser. In the case of 90/22 PS/WTR blends, 1 wt.% unmodified fibre and 0.5 wt.% RFL-coated fibres improved tensile modulus, flexural properties and impact strength. Tensile strength was improved marginally. The surface treatment of Nylon fibre and the addition of compatibiliser at 0.5 wt.% enhanced the tensile properties, flexural properties and impact strength. The dynamic mechanical analysis showed that the storage modulus at room temperature was better for untreated fibre composites in conjunction with the compatibiliser. The thermal stability of PS/NR was studied by TGA. Thermal stability of the blends improved with dynamic vulcanisation and with the incorporation of RFL-coated Nylon fibres. The untreated and partially hydrolyzed fibre composites in conjunction with the compatibiliser enhanced the thermal stability. Kinetic studies showed that the degradation of the blends and the composites followed first order kinetics.

Studies on meroplankton

Plankton community, drawn from a vary wide variety of animal phyla, formed the basic food supply of marine life and indicators of water mass. The term meroplankton generally referred to that portion of the zooplankton which is transient in nature, remaining rest of their lives in the nektonic or benthic environment. This group was selected for intensive studies, considering the role of meroplankton in the economy of the sea and the scarcity of literature on them from the Indian Ocean. The preser .udy besides providing information regarding the fixation and preservation !e _ iniques and biochemical aspects of tropical meroplankton, also consolidates information regarding their zoogeography in the Indian Ocean region, with a view to amplifying the limited information available from this area. The distribution studies are based on the collections made during the International Indian Ocean Expedition (1960-65), whereas the material for preservation and biochemical studies was collected from the coastal waters during 1968-1978. Salient features:- 2% of formaldehyde buffered with 2% borax, added to the plankton in the ratio of 9:1 was found the best fixative. On fixation the plankton underwent shrinkage due to loss of 15 to 87% water. Addition of antioxidants prevented colour fading. Narcotization by different specific reagents prior to fixation reduced distortions due to violent reaction and improved morphological conditions. One percent formaldehyde solution in sea water buffered with borax or neutralised with calcium carbonate perfectly preserved majority of meroplankton. Equally good was one percent propylene phenoxetol buffered with borax. Biochemical compostion of vaioous taxa showed variations according to their age class, size groups metamorphosing stage, feeding mechanism, type of organism fed and time of collection. General distribution studies of 4 meroplankton taxa - Anthozoan larvae, cirripedia larvae, sipunculoid larvae and gastropod larvae stowed abundance in the coastal areas especially during the SW monsoon period. Based on the larval distribution different zoo-geographical areas in the Indian Ocean are differentiated.

Epoxidized Phenolic Novolac: A Novel Modifier for Unsaturated Polyester Resin

Unsaturated polyester resins (UPRs) are used widely in the fiber-reinforced plastics (FRPs) industry. These resins have the disadvantages of brittleness and poor resistance to crack propagation. In this study, hybrid polymer networks (HPNs) based on UPR and epoxidized phenolic novolacs (EPNs) were prepared by reactive blending. A HPN is composed of a backbone polymer containing two types of reactive groups that can take part in crosslinking reactions via different mechanisms. EPNs were prepared by glycidylation of novolacs using epichlorohydrin. The novolacs had varying phenol: formaldehyde ratios. Blends of unsaturated polyester with EPN were then prepared. The physical properties of the cured blends were compared with those of the control resin. EPN shows good miscibility and compatibility with the resin and improves the toughness and impact resistance substantially. Considerable enhancement of tensile strength is also noticed at about 5% by weight of epoxidized novolac resin. TGA, DMA, and DSC were used to study the thermal properties of the toughened resin and the fracture behavior was studied using SEM. The blends are also found to have better thermal stability. Blending with EPN can be a useful and cost-effective technique for modification of UPR

Molecular computations for reactions and phase transitions: applications to protein stabilization, hydrates and catalysis

In this work we have made significant contributions in three different areas of interest: therapeutic protein stabilization, thermodynamics of natural gas clathrate-hydrates, and zeolite catalysis. In all three fields, using our various computational techniques, we have been able to elucidate phenomena that are difficult or impossible to explain experimentally. More specifically, in mixed solvent systems for proteins we developed a statistical-mechanical method to model the thermodynamic effects of additives in molecular-level detail. It was the first method demonstrated to have truly predictive (no adjustable parameters) capability for real protein systems. We also describe a novel mechanism that slows protein association reactions, called the “gap effect.” We developed a comprehensive picture of methioine oxidation by hydrogen peroxide that allows for accurate prediction of protein oxidation and provides a rationale for developing strategies to control oxidation. The method of solvent accessible area (SAA) was shown not to correlate well with oxidation rates. A new property, averaged two-shell water coordination number (2SWCN) was identified and shown to correlate well with oxidation rates. Reference parameters for the van der Waals Platteeuw model of clathrate-hydrates were found for structure I and structure II. These reference parameters are independent of the potential form (unlike the commonly used parameters) and have been validated by calculating phase behavior and structural transitions for mixed hydrate systems. These calculations are validated with experimental data for both structures and for systems that undergo transitions from one structure to another. This is the first method of calculating hydrate thermodynamics to demonstrate predictive capability for phase equilibria, structural changes, and occupancy in pure and mixed hydrate systems. We have computed a new mechanism for the methanol coupling reaction to form ethanol and water in the zeolite chabazite. The mechanism at 400°C proceeds via stable intermediates of water, methane, and protonated formaldehyde.

Functional studies of the deubiquitinating enzymes USP19, USP4 and UCH-L1

El marcaje de proteínas con ubiquitina, conocido como ubiquitinación, cumple diferentes funciones que incluyen la regulación de varios procesos celulares, tales como: la degradación de proteínas por medio del proteosoma, la reparación del ADN, la señalización mediada por receptores de membrana, y la endocitosis, entre otras (1). Las moléculas de ubiquitina pueden ser removidas de sus sustratos gracias a la acción de un gran grupo de proteasas, llamadas enzimas deubiquitinizantes (DUBs) (2). Las DUBs son esenciales para la manutención de la homeostasis de la ubiquitina y para la regulación del estado de ubiquitinación de diferentes sustratos. El gran número y la diversidad de DUBs descritas refleja tanto su especificidad como su utilización para regular un amplio espectro de sustratos y vías celulares. Aunque muchas DUBs han sido estudiadas a profundidad, actualmente se desconocen los sustratos y las funciones biológicas de la mayoría de ellas. En este trabajo se investigaron las funciones de las DUBs: USP19, USP4 y UCH-L1. Utilizando varias técnicas de biología molecular y celular se encontró que: i) USP19 es regulada por las ubiquitin ligasas SIAH1 y SIAH2 ii) USP19 es importante para regular HIF-1α, un factor de transcripción clave en la respuesta celular a hipoxia, iii) USP4 interactúa con el proteosoma, iv) La quimera mCherry-UCH-L1 reproduce parcialmente los fenotipos que nuestro grupo ha descrito previamente al usar otros constructos de la misma enzima, y v) UCH-L1 promueve la internalización de la bacteria Yersinia pseudotuberculosis.

Estudio de cultivos celulares primarios derivados de Lucilia sericata (Diptera: Calliphoridae)

The main purpose of this study was to obtain primary cell cultures derived from Lucilia sericata (Diptera: Calliphoridae). Necrophagous this fly is used for determination of post-mortem interval and larval therapy. Since explants embryonated eggs were performed in various culture media (Grace Schneider, MM/VP12, DMEM, Grace/L-15 and L-15), supplemented with 20% fetal serum. Sterilization of the biological material was carried out by immersing it in formaldehyde and sodium hypochlorite solutions. The cell growth was initiated in the L-15, MM/VP12, and Schneider Grace/L-15 in an average time of 10 days after completion of planting by the proliferation of groups of colonies scattered on the surface of the boxes crops and also from the endings of larval fragments. The evolution of cell growth to the formation of monolayer semi-confluent was relatively fast, reaching at 3 weeks post-explant. Cellular morphology in cultured cells was heterogeneous, especially epithelioid forms, similar to nerve, giant and irregular. Comparison of the growth characteristics of these cell cultures with those obtained from other species of flies was more favorable in the evolution of those obtained from L. sericata, on the grounds that the cells are better adapted to the physical-chemical conditions of several culture media. This is the first report of a cell culture-fly family Calliphoridae.

Caracterización de la exposición ocupacional a formaldehído en trabajadores del sector salud y educación en Colombia 2004-2013.

El Formaldehído es una sustancia química de amplio uso a nivel mundial con efectos documentados en personas expuestas entre los cuales se destacan irritación de la piel, mucosas, tracto respiratorio y ojos. Según la Agencia Internacional para la Investigación del Cáncer (IARC) el formaldehido se encuentra clasificado en el grupo 1 como agente cancerígeno con suficiente evidencia de producir neoplasias en humanos. Los sectores industriales en Colombia que utilizan de forma frecuente el formaldehído incluyen los fabricantes de maderas, los servicios funerarios, y los sectores de salud y educación. El presente estudio de corte transversal pretende, con base en mediciones históricas (2004-2013) construir un perfil de exposición a formaldehído en trabajadores vinculados al sector de salud y educación en Colombia, divididos y analizados según actividades de trabajo similares (Patólogos, Histotecnólogos, Auxiliares de laboratorio, Docentes y Estudiantes), con el fin de establecer una línea base de diagnóstico para la orientación acciones dirigidas al control del riesgo. Con base en los hallazgos y soportados en estimadores estadísticos aplicables a los grupos de exposición, en general existe un tendencia de no conformidad al comparar los resultados aplicables con valores de referencia de larga duración definidos para el agente por autoridades internacionales. De forma complementaria se encontraron brechas significativas respecto a la implementación de controles administrativos y técnicos que sugieren circunstancias de exposición no controladas en los colectivos de interés.

Exposición laboral de agentes químicos carcinógenos presentes en las empresas afiliadas a una ARL en Colombia 2011-2014

Objetivo: Caracterizar los sectores económicos con mayor susceptibilidad de exposición a agentes químicos carcinógenos, categorizados en el grupo 1 por la Agencia Internacional para la Investigación del Cáncer IARC (formaldehído, polvo de madera, benceno y sílice cristalina) afiliadas a una Administradora de riesgos Laborales (ARL) en Colombia entre el periodo 2011 a 2014. Método: Estudio de tipo descriptivo retrospectivo con datos históricos obtenidos desde 2011 hasta 2014. De acuerdo con el número de mediciones que se realizó en cada área y cargo de las empresas objeto de estudio, se utilizó la medición basal para determinar el estado inicial y evaluar de manera concurrente la exposición de estos cuatro agentes químicos. Resultados: En total se obtuvieron 201 mediciones de higiene industrial para cuatro agentes químicos carcinógenos. Los resultados mostraron que índice de riesgo de la exposición a agentes químicos carcinógenos en diferentes empresas, se encuentra en algunos casos en niveles altos o críticos dado que superar los valores máximos permisibles definidos por la Conferencia Americana de Higienistas Industriales de Gobierno (ACGIH). Conclusión: Los trabajadores de diferentes empresas en Colombia están expuestas a diferentes tipos de concentraciones por agentes químicos cancerígenos. Las concentraciones ambientales obtenidas en el ambiente laboral en algunos casos excedieron las concentraciones máximas permitidas, por lo que se recomienda que las empresas e instituciones del país fortalezcan las medidas de prevención, vigilancia y control para minimizar los riegos a que pueden estar expuestos sus trabajadores.

Linear response functions for a vibrational configuration interaction state

Linear response functions are implemented for a vibrational configuration interaction state allowing accurate analytical calculations of pure vibrational contributions to dynamical polarizabilities. Sample calculations are presented for the pure vibrational contributions to the polarizabilities of water and formaldehyde. We discuss the convergence of the results with respect to various details of the vibrational wave function description as well as the potential and property surfaces. We also analyze the frequency dependence of the linear response function and the effect of accounting phenomenologically for the finite lifetime of the excited vibrational states. Finally, we compare the analytical response approach to a sum-over-states approach

Chlorine tolerant, multilayer reverse-somosis membranes with high permeate flux and high salt rejection

A new class of high molecular weight polyethersulfone ionomers is described in which the ionic content can be varied, at will, over a very wide and fully-controllable range. A novel type of coating process enables these materials to be deposited from alcohol-type solvents as cohesive but very thin (50 – 250 nm) films on porous support-membranes, giving high-flux membranes (3.3 – 5.0 L m-2 h-1 bar-1) with very good, though not outstanding salt rejection (typically 92 - 96%). A secondary layer, of formaldehyde-cross-linked polyvinyl alcohol, can be deposited from aqueous solution on the surface of the ionomer membrane, and this layer increases salt rejection to greater than 99% without serious loss of water permeability. The final multi-layer membrane shows excellent chlorine tolerance in reverse-osmosis operation.

A model for stretch-bend interactions in molecular force fields

Interaction force constants between bond-stretching and angle-bending co-ordinates in polyatomic molecules have been attributed, by some authors, to changes of hybridization due to orbital-following of the bending co-ordinate, and consequent changes of bond length due to the change of hybridization. A method is described for using this model quantitatively to reduce the number of independent force constants in the potential function of a polyatomic molecule, by relating stretch-bend interaction constants to the corresponding diagonal stretching constants. It is proposed to call this model the Hybrid Orbital Force Field. The model is applied to the tetrahedral four co-ordinated carbon atom (as in methane) and to the trigonal planar three coordinated carbon atom (as in formaldehyde).