An all-aromatic thermosetting copolyester has been prepared using hydroquinone, hydroxybenzoic acid, isophthalic acid, trimesic acid, and/or 1,3,5-triacetoxybenzene as key building blocks. The preparation and characterization of these materials are described. Cured resins based on these structures exhibit thermal stabilities in nitrogen to 450 °C, glass transition temperatures up to 240 °C, and moisture pickups of only 0.3 wt %. An important feature of these cross-linked aromatic copolyesters is their ability to undergo further processing in the solid state through interchain transesterification reactions.

The adhesive properties of a new family of crosslinkable aromatic copolyester resins are described in this paper. A unique method for forming an adhesive bond in the solid state through high temperature interchain transesterification reactions (ITR) between cured thin films of these copolyester thermosets is indicated. Bonds formed via this procedure yield average lap shear strengths of roughly 13 MPa to titanium adherends and invariably exhibit failure at the polymer‐metal interface and not within the polymer. Various procedures to increase the strength of the bond at the interface between the polymer and the metal were tested such as the effect of surface pretreatments, primers, fillers, and the role of bondline thickness on the lap shear strength of the joints. Of these, the use of surface pretreatments and thinner bondlines has the greatest effect, raising the observed average lap shear strength of the joints to 16.5 and 20.7 Mpa, respectively. Some of the adhesive properties pertaining to the use of this new thermoset as a matrix in a graphite fiber composite are also presented.

ABSTRACT:The experimental and modeling studies are presented on the melt polycondensation of poly(ethylene terephthalate) by a gas sweeping process. In this process, low molecular weight prepolymer is polymerized to a higher molecular weight polymer in a molten state at ambient pressure as ethylene glycol is removed by nitrogen gas bubbles injected directly to the polymer melt through a metal tube. In the temperature range of 260 -280°C, the rate of polymerization by the gas sweeping process is quite comparable to that of conventional high vacuum process. The effects of nitrogen gas flow rate and reaction temperature on polymerization rate and polymer molecular weight were investigated. Polymer molecular weight increases with an increase in gas flow rate up to certain limits. A dynamic mass transfer-reaction model has been developed, and the agreement between experimental data and model simulations was quite satisfactory. The effect of ethylene glycol bubble nucleation on the polymerization has also been investigated. It was observed that the presence of nucleated ethylene glycol bubbles induced by the bulk motion of polymer melt has negligible impact on the polymerization rate and polymer molecular weight.

A series of multiblock poly(ether-ester-amide)s (PEEA) based on polyamide-6 (PA6) and poly(ethy1ene glycol) (PEG) is synthesized in a two-step process. The first step represents the hydrolytic polymerization of E-caprolactam (CL) in the presence of adipic acid (AA) to carboxylterminated PA6 oligomers of different chain lengths and the second is their polycondensation with PEG of molecular weights 420 (PEG 400) and 1 150 (PEG 1ooO) in the presence of catalyst and thermostabilizer. The formation of the new ester bond between PA6 and PEG is proved by infrared spectroscopy. The content of the hard (PA6) and the soft (PEG) segments in the copolymer is determined by 'H NMR and elemental analysis. The shift in glass transition temperature Tg above that of pure PEG and the depression of the melting temperature T, assigned to PA6 are characteristic for phase-separated block copolymers. The degree of crystallinity of the PA6 component does not seem to be affected by the actual weight composition but depends on the different segment lengths. For the copolymers containing PEG1000 it is close to that of the respective homopolymer PA6. The tensile parameters of the copolymers studied are similar to those of available PEEA products.

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