Synthesis, Properties And Cure Kinetics Of Tung Oil Based Polyamide Derivatives

A series of polyamide derivatives used for printing inks and epoxy curing agent were prepared from methyl eleostearate, acrylic acid and polyamines. The relationship of structures and properties of polyamide resins used for printing inks was discussed, the mechanical and thermal properties of polyamide for curing epoxy resins were tested and the cure kinetics of these polyamide with epoxy resin were studied.First, a novel methyl of C21 diacid (TMAA) was synthesized from methyl eleostearate and acrylic acid. The optimal reaction conditions indicated by orthogonal experiment were as follows: with 1% p-benzenediol by weight of acrylic acid used as polymerization inhibitor, the reaction temperature was maintained at 180℃for 3h at a feed ratio of 1:0.247 (the ratio of Methyl eleostearate to acrylic acid). GC-MS exhibited that there were six isomers in the product and the purity was 98.6%. The structure of the addition product was also characterized by EA, FT-IR spectroscopy, ¹H-NMR, ¹³C-NMR and GC-MS.Then three new reactive polyamides as epoxy curing agent were manufactured from diethylen etriamine, triethylenete tramine and tetraethylene pentamine with TMAA. Compared to the cured product of polyamide prepared from C₃₆ dimer acid, the cured product of polyamides made from TMAA had higher tensile strength, elasticity modulus, bending strength, bengding modulus, compression strength and compression modulus, but lower tensile strain and lap shear strength. T_g values of the curing product made up of three curing agents sample 1, sample 2, sample 3 and epoxy resin EP-618 were 108℃, 109℃and 116℃, respectively, which are much higher than that of the cured product made from polyamide 650. The activation emergy of three samples in curing reactions were calculated by n order model were 62.179kJ/mol, 56.551 kJ/mol and 59.761kJ/mol, respectively. The activation energy data was unable to reflect the activity of different curing agents. The n order model can be used to predict curing process at low heat rates generally. As the heat rate increased, the n order model was of more and more distinction with experimental data. Besides, the n order model unreasonably simulated iso-thermal curing process of sample 1 and EP-618.For a better result of kinetic data, Málek method and autocatalytic mechanism were introduced to calculate the kinetic equation of curing reaction. The values of the activation energy calculated by the isoconversional method were 52.436kJ/mol, 55.385kJ/mol and 54.387 kJ/mol., which reasonably embodied the activity of various curing agent samples. The result exhibited that nonisothermal and isothermal DSC curves of three samples obtained using the experimental data show a good agreement with that theoretically calculated.Besides, a series of polyamide resins as printing ink binder were synthesized by condensation polymerization from various monomers. Mechanical properties testing and DSC indicated that polyamide derives from isophorone diamine (IPDA) had higher shore hardness and lap shear strength, but a lower melting point and glass transition temperature (Tg). As the ratio of IPDA/EDA in diamines increased, the gel point of prepared polyamide solutions decreased from 14℃to -35℃and the softening point of prepared polyamide decreased from 112℃to 88℃, then increased to 103℃. It was proved that IPDA improved the anti-gelling behavior of the polyamide but weakened its thermal properties. TMAA had similar effect on the performance of prepared polyamide. All the polyamides had approximative solubility parameters, and they were soluble in n-propyl, tetrahydrofuran and n-butyl acetate, but their solubility in ethonal were not improved hereby.