Dynamic mechanical and thermal behavior of epoxy resins based on soybean oil

ABSTRACT: Mechanical and thermal properties of materials prepared by curing epoxidized soybean oil with various cyclic acid anhydrides in the presence of tertiary amines were investigated by dynamic mechanical thermal analysis and thermogravimetry. All samples presented thermoset material characteristics that were dependent upon the type of anhydride, the anhydride/epoxy molar ratio, and epoxy group content. The thermosets obtained from anhydrides with rigid structures as such phthalic, maleic, and hexahydrophthalic showed higher glass transition temperatures (Tg) and cross-linking densities. As expected, the Tg decreased as the anhydride/epoxy ratio decreased. The influence of the degree of epoxidation of soybean oil on the mechanical properties and Tg was also investigated. It was found that the higher the epoxy group amount, the higher the Tg and hardness. Cured resins exhibited thermal stability up to 300°C, except for those prepared with dodecenylsuccinic anhydride, which began to decompose at lower temperature. They presented excellent chemical resistance when immersed in 1% wt/vol NaOH and 3% wt/vol H 2 SO 4 solutions but poor chemical resistance in the presence of organic solvents. Paper no. J10209 in JAOCS 79, 797-802 (August 2002). KEY WORDS: Chemical resistance, dynamical mechanical properties, epoxidized soybean oil, epoxy resins, thermogravimetric analysis, thermosetting polymers. Vegetable oils represent an interesting renewable source for the production of useful chemicals and new materials (1). Soybean oil is readily available in bulk and is mainly composed of TG molecules derived from unsaturated acids, such as oleic acid (22%), linoleic acid (55%), and linolenic acid (7%). Although unsaturated acids possess double bonds, which are the reactive sites for coatings and paints, they need to be functionalized by the introduction of epoxy, hydroxyl, or carboxyl groups in order to be used for preparation of polymeric materials. Soybean oil can be epoxidized by different methods (2-4) yielding conversions and selectivities higher than 90%. Industrially, it is used mainly as a polyvinyl chloride additive to improve stability and flexibility. New applications have been made possible by the use of photochemically initiated cationic curing (5) and by the preparation of thermosetting materials such as epoxy resins. Epoxy resins are widely used as adhesives and as matrices in composite materials because of their good physical and chemical properties. Toughness and other properties of epoxy resins can be significantly improved by the modification of classical epoxy resins, such as those based on diglycidylether of bisphenol A (DGEBA). Epoxidized vegetable oils prepared from the most unsaturated oils, e.g., soybean oil or linseed oil, can be used for such purpose. In this work we report dynamic mechanical properties of different materials prepared by curing fully and partially epoxidized soybean oil (ESO) with various cyclic acid anhydrides in the presence of tertiary amines. Thermal and chemical resistance were also investigated. MATERIALS AND METHODS Phthalic anhydride (PA), hexahydrophthalic anhydride (CH), maleic anhydride (MAL), and N,N′-dimethylaniline (ARO) were purchased from Aldrich Chemical Co. (Milwaukee, WI) and purified just before use by standard methods. Succinic anhydride (SUC) was purchased from Sigma Co. (St. Louis, MO) and recrystallized from chloroform. Triethylamine (TEA) was purchased from Merck (Darmstadt, Germany) and distilled before use. Dodecenylsuccinic anhydride (DDS) (Sigma Co.) and 1,4-diazabicyclo[2.2.2]octane (DABCO) (Aldrich Chemical Co.) were used without further purification. Fully ESO was supplied by CBM Indústria, Comércio e Distribuição Ltda. (Cachoeirinha, RS, Brazil) and contained 4.1 mmol epoxide/g determined by the oxirane oxygen standard method (AOCS Cd 9-57) (6). On average, ESO has a M.W. of about 929 g/mol and contains about 3.8 epoxy groups per TG. Partially ESO were prepared using the methyltrioxorhenium-CH 2 Cl 2 /H 2 O 2 system (4). The degree of epoxidation was calculated by integrating the signals in the 2.9-3.1 ppm region of the 1 H NMR spectra, corresponding to the cis epoxy hydrogens. Dynamic mechanical properties were measured on Polymer Laboratory-Dynamic Mechanical Thermal Analysis equipment operating in single cantilever mode. The measurements were performed from −60 to 100°C at a heating rate of 2°C/min and frequency of 1 Hz. The glass transition temperature (Tg) was determined as the temperature at the maximum of the tan δ vs. temperature curve. A TA Instruments model 2050 thermogravimeter was used to measure the weight loss of the polymeric materials in an N 2 atmosphere. The samples were heated from 30 to 800°C at a heating rate of 10°C/min

InCl3/NaClO: A reagent for allylic chlorination of terminal olefins

Indium trichloride promotes the chlorination of terminal olefins in the presence of sodium hypochlorite with good results. Carvone was chosen as a model compound to examine some of the general features of this reaction, such as stoichiometry, temperature, reaction time and product conversion. Treatment of beta-pinene with sodium hypochlorite in the presence of indium trichloride resulted in a facile rearrangement to selectively yield perillyl chloride, which is an important precursor for C-7 oxygenated limonenes

Simulation of the Equilibrium Constant Effect on the Kinetics and Average Properties of Polystyrene Obtained by ATRP

Este artigo utiliza simulações para estudar o processo de polimerização radicalar via transferência de átomo por meio da análise do comportamento das espécies químicas (polímeros “vivos”, “dormentes” e “mortos”). Para isso, um modelo matemático foi desenvolvido usando o método dos momentos, e os dados experimentais da polimerização de estireno, obtidos da literatura, foram utilizados para validá-lo. A partir disto, foram obtidos perfis de concentração destas espécies, que foram posteriormente usados para obter as propriedades médias dos polímeros (Mn e IPD). As propriedades foram avaliadas em diferentes valores da costante deequilíbrio (Keq) e verificou-se que os valores na ordem de 10-7 e 10-9 proporcionam o melhor controle na estrutura dos polímeros. Esta pesquisa é, por isto, um ponto de partida para a escolha ideal do sistema catalítico, ligantes e iniciadores. Além disso, a técnica de modelagem apresentou-se como uma ferramenta de fácil implementação e bastante eficiente na análise do processo ATRP.This article uses simulations to study the atom transfer radical polymerization by analyzing the behavior of the chemical species (“living”, “dormant” and “dead” polymers). For this, a mathematical model has been developed using the method of moments, and experimental data from styrene polymerization, obtained from literature, were used to validate the model. From this point, the concentration profiles of all species were obtained, and later on, they were used to obtain the average properties of polymers (Mn and PDI). The properties were evaluated at different values of equilibrium constant (Keq) and it was found that values around 10-7 and 10-9 provide a better control in the structure of polymers. Therefore, this study is a starting point for selecting the optimal catalytic system, binders and initiators. In addition, the modeling technique presented as a useful tool, being very effective on the analysis of ATRP processes

Styrene ATRP using the new initiator 2,2,2‐tribromoethanol: Experimental and simulation approach

Atom transfer radical polymerization (ATRP) is a powerful technique for the controlled synthesis of polymers, and one of the most important ATRP characteristics is the possibility to produce functionalized polymers. 2,2,2‐Tribromoethanol appears as a promising initiator for the ATRP process, because it allows the production of polymers with end hydroxyl groups, making it easy for copolymerization with biomonomers. This article explores, in experimental and computational level, the styrene ATRP using 2,2,2‐tribromoethanol to understand how this new initiator behaves, and presents a powerful tool to predict the polymer properties for different operating conditions. Simulations and experimental results showed that polymers with high molecular weight and low PDI can be simultaneously obtained using 2,2,2‐tribromoethanol as initiator. For all operational conditions, the reaction was fast and polydispersity values kept lower than 1.4, confirming the “living”/controlled characteristic. The polymers produced contain hydroxyl as functional group and in some operating conditions, PDI values of 1.1 was obtained, even at high monomer conversion551022702276sem informaçãosem informaçã

Symmetrical and Asymmetrical Cyanine Dyes. Synthesis, Spectral Properties, and BSA Association Study

New cyanines were prepared by an efficient and practical route with satisfactory overall yield from low-cost starting materials. The photophysical behavior of the cyanines was investigated using UV–vis and steady-state fluorescence in solution, as well as their association with bovine serum albumin (BSA) in phosphate buffer solution (PBS). No cyanine aggregation was observed in organic solvents or in phosphate buffer solution. The alkyl chain length in the quaternized nitrogen was shown to be fundamental for BSA detection in PBS in these dyes

Structure of Micelles Formed by Highly Asymmetric Polystyrene-b-Polydimethylsiloxane and Polystyrene-b-poly[5-(N,N-diethylamino)isoprene] Diblock Copolymers

The internal structure of polystyrene(PS)-shell micelles having core-forming blocks consisting of polydimethylsiloxane (PDMS) or poly[5-(N,N-diethylamino)isoprene] (PAI) was determined in detail by accessing the multilevel structural organization using static and dynamic light scattering and small-angle X-ray scattering techniques. Well-defined PS-b-PDMS and PS-b-PAI diblock copolymers with molar masses in the range of 12.0k-18.2k g/mol were dispersed in cyclohexane, dimethylacetamide, or dimethylformamide. Colloidal nanoparticles exhibiting either swollen core with a large surface area per corona chain that enables the PS chains to assume a random coil conformation with Gaussian statistics, or compact core and slightly stretched PS chains in the corona were obtained. Therefore, the results of this study provide an interesting alternative allowing for precise control of the core and corona properties of PS-b-PDMS and PS-b-PAI micelles in selective solvents. Admittedly, such differences in terms of micellar properties can dictate the potential of block copolymer micelles for generating thin films from preformed nano-objects, as well as the capability to function as nanoreactors in organic medium.Fil: Giacomelli, Fernando C.. Universidade Federal do ABC; BrasilFil: Riegel, Izabel C.. Universidade Federal do Paraná; BrasilFil: Stepanek, Petr. Institute of Macromolecular Chemistry; República ChecaFil: Petzhold, Cesar L.. Universidade Federal do Rio Grande do Sul; BrasilFil: Ninago, Mario Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidade Federal do Rio Grande do Sul; BrasilFil: Satti, Angel Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidade Federal do Rio Grande do Sul; BrasilFil: Ciolino, Andrés Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidade Federal do Rio Grande do Sul; BrasilFil: Villar, Marcelo Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidade Federal do Rio Grande do Sul; BrasilFil: Schmidt, Vanessa. Universidade Federal de Santa Maria; BrasilFil: Giacomelli, Cristiano. Universidade Federal de Santa Maria; Brasi