Study of blends of nylon 6 with EVOH and carboxyl-modified EVOH and a preliminary approach to films for packaging applications

Abstract

Blends of nylon 6 ( Ny6 ) with ethylene-co-vinyl alcohol (EVOH) and EVOH modified with the introduction of carboxyl groups ( EVOH -COOH ) have been studied by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and dynamic-mechanical thermal analysis. The thermal and thermomechanical analyses of the blends show that the melting, crystallization, and relaxational behavior are affected by the blend composition and the presence of carboxyl groups on the EVOH chains. Nevertheless, microscopic and thermal investigations demonstrate the biphasic nature of the two-blend systems. Selective solvent extraction of the EVOH or EVOH -COOH phase in their blends and Fourier transform infrared analysis of the residual products indicates the occurrence of ionic linkages between the amino groups of the polyamide and the carboxyl groups of the modified EVOH, whereas specific interactions are evidenced for Ny6 / EVOH blends. Tests performed on extruded Ny6 / EVOH films show that the addition of EVOH effectively reduces the gas permeability of Nylon, whereas the addition of small amounts of EVOH -COOH helps to control and stabilize melt rheology.

Reactive compatibilizer precursors for LDPE/PA6 blends, 1

“…The amidation reactions between the amine end groups of PA and the free carboxyl groups of the CPs, which is considered by most authors31,32,35–43 as the route for the alleged production of CP‐ g ‐PA copolymers, involves the evolution of byproduct water (Equation (1)). The latter is known to hydrolyze the amide groups of PA (Equation (2)), unless it can escape from the reaction mixture.…”

“…Compatibilization of polymer blends by reactions taking place during compounding is becoming increasingly important9,10 and a range of chemistries has been used to realize it 11–13. Thus, the preparation of several high molar mass CPs consisting of polyolefin chains with reactive functional groups, such as anhydride, epoxy, isocyanate, oxazoline, glycidylmethacrylate, etc., and their use for the reactive compatibilization of polyolefin/polyamide blends have been described 1–3,5,6,14–46. All these CPs have been shown to lower the interfacial tension, improve the minor phase dispersion, enhance the adhesion of the phases, hinder the droplet coalescence and to enhance the mechanical properties of the blends.…”

“…In contrast, other CPs have not been studied as extensively and information concerning their interactions with polyamides is still scarce. For example, ethylene/acrylic (or methacrylic) acid copolymers (EAA, EMAA), eventually neutralized in part with sodium or zinc, as well as other polymers containing pendant carboxyl groups, have been blended with polyamides or added to polyamide/polyolefin blends and have been shown to improve their properties 6,30–46. However, the very nature of the interactions of the free carboxyl groups with the PA functionalities, either chemical reactions or hydrogen bond formation, is still to be clarified.…”

Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends

“…Tan δ for nylon showed the β relaxation peak at about −60 °C for Ny6 and −66 °C for Ny6*; this β peak is related to the segmental motion of amide groups not bonded to other amide groups 17. The α peak was attributed to the movement of large chain segments set free by the disappearance of hydrogen bonding with increasing temperature18 and is commonly ascribed to a glass transition 17.…”

Degradation of high barrier ethylene–vinyl alcohol copolymer under mild thermal‐oxidative conditions studied by thermal analysis and infrared spectroscopy

“…To avoid the deterioration of physical and barrier properties by the uptake of water, these materials are usually sandwiched in multilayer structures by coextrusion where an inner and outer layer of a hydrophobic material, eg polyethylene, wrap up the EVOH barrier layer. Blends of EVOH with other materials have been intensively studied3, 4, 5 over the last few years, with the aims of boosting the barrier properties of low barrier performance materials, or improving the processability, and/or decrease the water sensitivity of EVOH.…”