Understanding the Morphological Changes in the Polypropylene/Polyamide 6 Fifty/Fifty Blends by Interfacial Modifiers Based on Grafted Atactic Polypropylenes: Microscopic, Mechanical, and Thermal Characterization

Abstract

The main aim of the present work is to correlate the morphological changes observed in the modified PP/PA6 fifty/fifty blends molded at confined flow conditions with both their mechanical and thermal properties and the kind and the amount of the interfacial modifiers used. Both transmitted light optical microscopy in the positive phase contrast mode, PC TOM, and field emission scanning electronic microscopy, FE SEM, were the used techniques for, respectively, general morphology overview and fractures surface analysis. The interfacial modifiers, a succinic anhydride, aPP-SA, and a succinyl-fluorescein, aPP-SF/SA, grafted atactic polypropylenes obtained and well characterized in authors’ laboratories came from the chemical modification of an atactic polypropylene industrial by-product. The amounts of any of both the interfacial modifiers came coded by the Box-Wilson experiment design methodology applied to the overall PP/PA6 binary system, watching that the interfacial agent was not a third component on a ternary blend but a true interfacial modifier in a binary one. All the studies were carried out over suitable specimens according to each test procedure with no further material manipulations to preserve at any moment the morphology of the blends as they emerge from the compression molding step at confined flow conditions.

Industrial waste origin succinic anhydride‐grafted atactic polypropylene as compatibilizer of full range polypropylene/polyamide 6 blends as revealed by dynamic mechanical analysis at the polypropylene glass transition

“…From an applied perspective, the polyamide/polyolefin blend system has been a prime subject for many years due to the potential industrial applications mainly related to the enhancement of impact properties and loss of water moistening [1][2][3][4][5][6][7][8][9]. Thus, the authors have chosen the isotactic polypropylene (iPP)/polyamide 6 (PA6) system to study the influence of the proposed interfacial agent in the dynamic mechanical parameters by many reasons based on their own experience [10][11][12][13]. Therefore, previously, to undertake a study covering the whole compositional range in the iPP/PA6 system, a series of concerns are assumed such as the previous knowledge about the thermal and mechanical properties enhancement, the stability of the emerging morphologies, and the evidence of reactive compatibilization occurring between phases [10][11][12][13].…”

“…Thus, the authors have chosen the isotactic polypropylene (iPP)/polyamide 6 (PA6) system to study the influence of the proposed interfacial agent in the dynamic mechanical parameters by many reasons based on their own experience [10][11][12][13]. Therefore, previously, to undertake a study covering the whole compositional range in the iPP/PA6 system, a series of concerns are assumed such as the previous knowledge about the thermal and mechanical properties enhancement, the stability of the emerging morphologies, and the evidence of reactive compatibilization occurring between phases [10][11][12][13]. Hence, it is well known that a very efficient method to compatibilize and so to enhance the interactions between the components in incompatible phases of heterogeneous materials based on polymers is by the presence the so-called interfacial agents (or compatibilizers) containing grafted groups onto a polymer backbone.…”

“…As mentioned before, in the case of two immiscible phases such as the iPP and PA6, improving the interactions through the interphase would imply the action of an interfacial modifier resembling one of the phases, especially the more mobile [14][15][16]. Additionally, this fact would allow the interfacial agent to be easily allocated in the polypropylene phase with the functionalities excluded from the crystalline domains in order to enhance the interaction with the PA6 phase through some kind of relation, preferably by the existence of real chemical bonds [10,14,16]. Otherwise, the better the interactions provided by the interfacial agent, the better the properties of the blends can be reached [10].…”

“…Additionally, this fact would allow the interfacial agent to be easily allocated in the polypropylene phase with the functionalities excluded from the crystalline domains in order to enhance the interaction with the PA6 phase through some kind of relation, preferably by the existence of real chemical bonds [10,14,16]. Otherwise, the better the interactions provided by the interfacial agent, the better the properties of the blends can be reached [10]. Additionally, the mainly amorphous nature of the interfacial agent (aPP-SA/SA) [17][18][19] results in an advantage to allocate it into the amorphous phase of iPP due to the fact that it is the latter what must allocate the PA6 phase [17].…”

“…In resume, one subject of this article is to investigate the effect of the interfacial modifications caused by an interfacial agent synthesized in our laboratories from polymerization wastes through a chemical modification batch solution process [18,19] in a system with a mobile interphase [14] in contrast to a classical composite system with one rigid phase (as it is the fillers) [20][21][22][23][24][25]. Conversely to other studies in literature considering only the more rigid phase (the PA6 phase) as the dispersed one [3,[9][10][11], one novelty of this work lies in considering the whole composition range (0-100 in iPP) in the iPP/PA6 system [10,[12][13][14]. It is well worth to mention that the interfacial agent used here is an atactic polypropylene with different types of succinic anhydride grafts.…”