Abstract
The glass transition temperature (Tg) is a crucial parameter for understanding the mechanical behavior of polyamide 6. It depends mainly on two aspects: hydration level and processing, i.e. the thermal history and the flow conditions. In this work, the effect of the thermal history on Tg was investigated by means of fast scanning calorimetry (flash-DSC). Two different solidification procedures were studied; isothermal crystallization and continuous cooling were performed at different temperatures and rates respectively. The procedures have led to two contradictory trends of glass transition evolutions when related to their crystallinity fraction. The concept of rigid amorphous phase is used. This is considered as a part of the amorphous phase with a lower mobility, present at the inter-phase between crystals and bulk amorphous (mobile amorphous fraction). The analysis leads to the conclusion that the thermal history affects the ratio between rigid and mobile amorphous phases and it is this ratio that determines the glass transition temperature of dry polyamide 6.
Highlights
Polyamide 6 (PA6) is an engineering polymer, commonly known as “Nylon 6”, which is used in the field of load-bearing applications where mechanical performance and lifetime are keywords
The analysis leads to the conclusion that the thermal history affects the ratio between rigid and mobile amorphous phases and it is this ratio that determines the glass transition temperature of dry polyamide 6
The aim of this work is to investigate the structure formation in PA6 for a wide range of cooling procedures and conditions mainly by means of fast scanning calorimetry, in order to determine the relation of the glass transition temperature with the structure, i.e. the amount of crystalline phase, mobile amorphous fraction (MAF) and rigid amorphous fraction (RAF)
Summary
Polyamide 6 (PA6) is an engineering polymer, commonly known as “Nylon 6”, which is used in the field of load-bearing applications where mechanical performance and lifetime are keywords Applications such as under-the-hood components and sport items are often exposed to demanding conditions like high load, challenging temperature regimes and elevated relative humidities. Its monomer has two polar groups; the amide and carbonyl groups These polarities can form hydrogen bonds between chains, leading to high strength [1]. If exposed to a humid environment, PA6 absorbs water till reaching a saturation level which is dependent on temperature and relative humidity [3] If this occurs, part of the hydrogen bonds are broken and new H bonds are formed with the water molecules [4]. It is clear that the glass transition temperature is an important parameter for PA6 properties
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