Absorption and diffusion of humidity in fiberglass-reinforced polyamide

Abstract

A statistical study of railway fastening insulating plates from various points of the Spanish territory reveals that high responsibility structural components injected with a hygroscopic material such as polyamide (PA) reinforced with short fiberglass can absorb varying amounts of water, depending on the working environment. This hygroscopic nature of PA6 means that the mechanical behavior of the matrix, and thus of the component as a whole, is heavily dependent on the content of water retained. This article studies the absorption and diffusion of water in the core of PA6. To verify the effects of humidity on the mechanical properties of reinforced PA6, the material was conditioned, that is, it was assigned a precise humidity content. The results obtained show that the interphase between the fiber and the matrix is a preferential way for the water advance in the composite. The diffusion of water in the PA core was carried out according to Fick's Second Law and the diffusion coefficient responds to an Arrhenius exponential law. The material behavior was experimentally validated and so it can be applied to quantify the humidity content of a component in a specific environment of temperature and exposure. POLYM. COMPOS., 26:580 -586, 2005.

In situ damage mechanisms investigation of PA66/GF30 composite: Effect of relative humidity

“…Both resolutions provided qualitatively relevant physical information. The lCT experiments were performed on samples with the size of 2 Â 2 Â 3.2 mm 3 . The tensile loaded lCT samples were extracted from the specimens that have been tensile loaded up to failure.…”

“…Eventually, this can increase the chains mobility of the polyamide (plasticization effect). Meanwhile, swelling effect can also occur since a certain amount of water is absorbed by the polyamide [1][2][3][4]. The plasticization highly impacts the polyamide properties as it reduces its glass transition temperature [5].…”

Structure–property relationships in glass‐reinforced polyamide, Part 3: Effects of hydrolysis ageing on the dimensional stability and performance of short glass–fiber‐reinforced polyamide 66

“…However, it has been known for sometime within the industry that the chemical nature of the glass fibre sizing can have a strong influence on the retention of some mechanical properties of composites exposed to such hydrothermal conditioning. It is also well known that polyamide materials absorb relatively high levels of moisture when exposed to hydrothermal conditioning in water and that this can cause significant dimensional changes (7)(8)(9)(10)(11)(12)(13). Despite this, and the fact that such hydrothermal testing has become commonplace for under-the-hood applications, there has been little systematic investigation of dimensional change of glass-fibre reinforced polyamide composites during such conditioning in coolant fluid.…”

The influence of environmental conditions on the dimensional stability of components injected with PA6 and PA66

“…Thomanson et al subjected samples to fixed laboratory conditions [2,14], which do not reproduce those experienced by the real component during its working life. Carrascal et al [5] studied thickness variations of samples in different environmental conditions, but did not examine dimensional variations along the other axis of the samples, which become relevant for analysing the behaviour and functionality of nylon components.…”

“…[2] and Carrascal et al [5], although this feature is also influenced by the manufacturing process and its conditions [12].…”