Selective chemical etching of poly(ethylene terephthalate) using primary amines

Abstract

Several primary amines have been examined as selective degradative etchants for the investigation of poly(ethylene terephthalate) (PET) morphology. The objective is to remove less ordered regions, leaving crystals intact. The amines include 40% and 20% aqueous methylamine, 70%–40% aqueous ethylamine and pure and 40% aqueous n‐propylamine. Weight‐loss and x‐ray diffraction data show that certain concentration of aqueous amine solution simultaneously degrade and crystallize PET. This observation indicates the hazard of using some of these amine reagents to characterize PET morphology since the crystalline structure found after etching is likely to be a result of solvent‐induced crystallization during degradation. Data for 40% aqueous methylamine used at room temperature shows that crystallization does not occur during etching, and in light of earlier research indicates the favorable nature of this reagent as a selective degradative medium for PET. Application of this reagent disclosed that in oriented PET fibers chemical stress cracking occurs, causing the degradative reagent to lose its selectivity.

Characterization of aminated poly(ethylene terephthalate) surfaces for biomedical applications

“…One approach to the introduction of nitrogen‐containing groups to the surface of PET is aminolysis, that is, the formation of amide groups by the reaction of a polyester with an amine. This method has already been identified as a simple approach to the surface modification of PET 9–12. Unacceptable degradation to the PET, as a result of the treatment, was observed when primary amines were used.…”

Fatigue crack propagation in amorphous poly(ethylene terephthalate)

“…Fracture surfaces were examined using an optical microscope (reflected light) and an ETEC scanning electron (SEM), for which specimens were prepared by gold/palladium coating. Fracture surfaces and portions of the face of the specimen containing the crack were also etched (for 20 hr) using a 40% solution of methylamine in water to reveal morphological detail; this etchant preferentially attacks amorphous polymer (16). Preliminary measurements of temperatures at the crack tip were made using a Barnes infrared camera, model RM-2B.…”

Aminolysis of polyesters for cracking and structure clarifying: A review

“…It was not possible to explain entirely the solvent induce crystallization in terms of solubility parameters of PET and amines used. It was found that a 40% methylamine solution had nonselective behavior for 6X drawn fiber, because stress cracking might affect the selectivity of aqueous amine 60 …”