Factors Affecting the Air Permeability and Moisture Permeability of PVC Composite Fabrics (Part 1) - Guangyuan Ruifeng New Materials

Category: PVC composite fabric

Release Time: 2020-08-11

Summary: The air permeability and moisture permeability of composite fabrics can be expressed by moisture resistance. When there is a difference in water vapor concentration (or water vapor partial pressure) on both sides of the fabric, the resistance of water passing through the fabric is called the moisture resistance of the fabric.

The breathability and moisture permeability of composite fabrics can be expressed using moisture resistance. When there is a difference in water vapor concentration (or water vapor partial pressure) on both sides of the fabric, the resistance of water passing through the fabric is called fabric moisture resistance. (Crosslinking agent used in PVC composite fabric, crosslinking agent manufacturer, PVC bonding promoter)

1. Temperature and humidity conditions of the fiber

Under the same fabric structure (including the volume ratio occupied by the fiber in the fabric), the type of fiber has almost no effect on the resistance of the fabric. Hollis's comparative experiment on hydrophilically treated polyester fabrics and untreated polyester fabrics also shows that under low humidity conditions, the transmission of water vapor is not significantly related to the type of fiber in the fabric. Only under high temperature conditions does the moisture permeability of hydrophilically treated polyester fabrics significantly outperform that of untreated polyester fabrics.

In fact, under low humidity conditions, because the fiber itself absorbs less moisture, and the diffusion coefficient of air is much larger than that of the fiber, water vapor diffuses through the pores between the fabrics to the side with lower water vapor pressure, indicating that the transmission of water vapor in the fabric is not much related to the type of fiber. At this time, the thickness and porosity of the fabric or the fabric structure are the main factors determining the moisture permeability of the fabric.

On the other hand, the moisture absorption of the fiber board is also related to the temperature. In the process of moisture absorption, the fiber releases a certain amount of heat after moisture absorption, which increases the temperature of the fiber aggregate, increases the water vapor partial pressure inside the fiber, reduces the gradient of water concentration inside and outside the fiber, and slows down the moisture absorption speed and diffusion moisture permeability speed. (Crosslinking agent used in PVC composite fabric, crosslinking agent manufacturer, PVC bonding promoter)

The diffusion coefficient of the fiber increases exponentially with the increase of temperature, and this increase is more obvious during moisture absorption. Therefore, the increase in temperature and humidity will enhance the moisture transmission capacity of the fibers in the fabric. From the perspective of the speed of moisture absorption or desorption, it generally appears faster at the beginning, and gradually slows down with the increase of moisture absorption or desorption, and finally reaches moisture absorption equilibrium. However, the time required to reach equilibrium is related to the moisture absorption capacity of the fiber itself and the tightness of the fiber aggregate; in addition, the thermal conductivity of the fiber will increase after moisture absorption, and the moisture permeability caused by the fiber's own moisture absorption is very complex, and there is no perfect theory to quantitatively describe it yet.

2. Fabric thickness and coverage factor

The thickness of the fabric is approximately related to its moisture resistance. Generally, the thicker the fabric, the greater the moisture resistance. This is because the thicker the fabric, the longer the path the water vapor takes through the pores between the fabrics. In addition, the change in fabric porosity has a significant impact on fabric moisture resistance. (Crosslinking agent used in PVC composite fabric, crosslinking agent manufacturer, PVC bonding promoter)

Keywords: Factors Affecting the Air Permeability and Moisture Permeability of PVC Composite Fabrics (Part 1) - Guangyuan Ruifeng New Materials

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