Synthesis and curing kinetics of cardanol‐based curing agents for epoxy resin by in situ depolymerization of paraformaldehyde

Three novel cardanol‐based phenalkamines with good stability have been successfully prepared by Mannich reaction using phenolic compounds with paraformaldehyde and hexamethylenediamine (or its mixture with other amines). The structure of the prepared phenalkamines has been analyzed using liquid chromatography‐mass spectrometry, nuclear magnetic resonance, and Fourier transform infrared spectroscopy. The curing kinetics of the prepared epoxy resin/phenalkamine systems has been investigated using differential scanning calorimetry (DSC), and determined by Kissinger, Flynn–Wall–Ozawa, and Crane methods. Furthermore, the thermal properties of the cured materials have been evaluated using DSC and thermogravimetric analysis, and the mechanical properties of the cured materials have been analyzed systematically. The results demonstrate that the phenalkamine 1 (PAA1) had a lower reactivity and better toughness than phenalkamine 2 (PAA2) and phenalkamine 3 (PAA3). In addition, PAA1 is a solid curing agent, while PAA2 and PAA3 are liquid curing agents, which were more convenient for practical usage. Results indicate that the properties of the prepared phenalkamines strongly depend on the structures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 472–480     

新型腰果酚双子表面活性剂的合成及表面活性

以天然生物质腰果酚、1,3-二溴丙烷及氯磺酸为原料,通过醚化、磺化及中和三步反应合成了一类新型的腰果酚基磺酸盐双子(Gemini)表面活性剂.采用傅立叶转换红外光谱仪和核磁共振谱仪表征了产物的结构;采用滴体积法测定了腰果酚Gemini表面活性剂的表面张力,研究了水溶液的表面性质,并与相应的单基腰果酚基磺酸盐表面活性剂进行了对比.结果表明:腰果酚Gemini表面活性剂水溶液的临界胶束浓度(cmc)为6.20×10-2 mmol.L-1,远小于相应的单基腰果酚表面活性剂水溶液的cmc(8.40mmol.L-1);其临界表面张力γcmc为36.92mN.m-1,与单基腰果酚表面活性剂水溶液的相近(γcmc为38.41mN.m-1).与此同时,腰果酚Gemini表面活性剂水溶液的最小分子截面积Amin为0.27nm2,比相应的单基表面活性剂水溶液的小得多.     

Thermal behavior of cardanol resin reinforced 20 mm long untreated bagasse fiber composites

Recently the attention in composite materials reinforced with natural fibers has significantly increased due to the new environmental legislation as well as consumer pressure that forced manufacturing industries to search substitutes for the conventional materials, e.g., glass fibers. In this way, the objective of the paper was to evaluate the thermal properties of sugarcane bagasse fiber-cardanol resin composites. Fibers were cut down to 20?mm length in diagonally. These fibers were mixed with the cardanol and epoxy resin, and fabricate in a biocomposites with different compositions, such as 0, 5, 10, 15, and 20?wt%. The thermal properties were evaluated by thermal gravimetric analysis and differential thermogravimetry analysis and also chemical formulation studied in Fourier transform infrared spectroscopy. The results showed the improved thermal strength of the composites in comparison to the neat polymer (0?wt%).     

Physicochemical properties of series of cardanol polyoxyethylene ether carboxylates with different ethoxylation unit at the interface

Series of cardanol polyoxyethylene ether carboxylates were synthesized with biomass cardanol as material to study their physicochemical properties at the interface. The surface tensions of the cardanol nonionic-anionic surfactants were measured at 25?°C and the thermodynamic parameters of adsorption were also calculated. The surface activity and thermodynamic properties of the cardanol nonionic-anionic surfactants were correlated to their chemical structures. With increasing of the number of the ethoxylation unit in the hydrophilic group, a decrease in adsorption efficiency and an increase in surface tension at critical micelle concentration and thermodynamic free energy of adsoption were observed and were attributed to a decrease in adsorption of the cardanol nonionic-anionic surfactants at the interface. Series of the cardanol nonionic-anionic surfactants have good wettability and foaming property. The foaming capacity and the foaming stability of the solution of the cardanol nonionic-anionic surfactants increase by decreasing in the ethoxylation unit and by increasing the double bond of the hydrophobic group. The physicochemical properties of the cardanol nonionic-anionic surfactants at the interface are correlated to the chemical structures of the investigated surfactants, and there is the synergy effect between the nonionic hydrophilic group and the anionic hydrophilic group at the interface.