Detailed explanation of waterproof and breathable fabric lamination technology and waterproof and breathable fabric expansion technology
1. The concept of fabric and film interface
FromThree-layer composite fabric‘s perspective, Waterproof and breathable laminated fabric is composed of one or more layers of fabric and polymer film bonded together through an adhesive to form a variety ofFunctional composite fabric. No matter how good the performance of the fabric and film is, if it cannot be bonded well to form a whole, or the peeling resistance of the laminated fabric after bonding is poor, it is obvious that this fabric has no practical value. The structural properties of the interface are closely related to the bonding effect. The stress on the fabric or film will be transmitted to each other through the interface between them, forming an overall macroscopic mechanical behavior.
The interface is not a single joint surface, but not necessarily Thickness and different action areas and interface layers. Three-layer composite fabric The interface layer of the laminated fabric is composed of the fabric surface area, fabric and film The interaction zone and the film surface zone constitute the multilayer transition zone. For the part where adhesive exists, the original interaction zone is expanded into a multi-layer bonding zone.
In macroscopic terms, the concept of surface, interface or contact surface They are all very clear and crossing the line is easy to identify. But when discussing the interaction between contact surfaces, it is a micro-level concept, and the division of the surface or interface is not so clear. The surface area refers to a thin layer with asymmetric structure and obviously different properties from the main body. These are difficult to distinguish from the microscopic level. Even in a certain layer area, the structure is not a homogeneous phase, and there are also heterogeneous heterostructure micro-areas.
2. Interface force and bonding strength
The force at the bonding interface is directly related to the bonding strength ,Kunshan Yingjie Textile Import and Export Co., Ltd. believes that there are three types of forces on the interface: 1. The class is static force, such as the force generated by “anchoring” effect and friction. The so-called “anchoring” effect is due to the flow of uncured resin into the pits or gaps of the adhesive parts and solidification there. Its effect is equivalent to The anchorage of the ship causes the resin to adhere to the surface of the bonded body. The contribution of this kind of static force to the interface bonding strength theoretically reaches 1.4~7.0MPa. The second type is the interfacial intermolecular force, that is, when the adhesive and the adherend are close to each other, it is 0.3~0.5nm. The force generated by dispersion, dipole and hydrogen bonding can theoretically contribute up to 7.0×102MPa to the interface bonding strength. The third category is chemical bonding force, that is, when the adhesive molecules and the adherend molecules are close to each other within 0.1~0.3 nm, a chemical reaction occurs to form a chemical bond. The contribution of this chemical bond to the interface bonding strength can theoretically reach 7.0×10 3~7.0×104MPa. These three types of forces may exist simultaneously for a bonding system, but the magnitude of their effects varies depending on the situation. Generally speaking, the intermolecular force contributes a large proportion to the interface bonding strength, but the ability to resist medium and water corrosion mainly depends on the chemical bond force. Therefore, in order to make the interface bonding strength both high and resistant to medium corrosion, In addition to sufficient intermolecular forces, the interface must introduce necessary chemical bonding forces. From the above analysis, it can be seen that if the interface is ideally bonded, the interface bonding strength is very considerable. In fact, the bonding strength retains a very small part of the theoretical value. This is due to poor intermolecular contact during the bonding process, which results in microporous defects on the bonding interface, reduces the bonding interface area, causes stress concentration, and promotes early failure. In addition, the residual thermal stress and shrinkage stress at the interface also contribute to strength loss.
3. Introduction of waterproof, moisture-permeable and expanded fabrics
The outer layer of ordinary fiber is coated with swollen polymer. After being woven into fabric, it is moisture-permeable when dry and waterproof when exposed to water.
Swelling polymers usually use hydrogels, hydrogels It has the characteristics of water-absorbing swelling and de-swelling when dehydrated, and it is grafted and polymerized on fabrics. In a dry state, the grafted gel layer shrinks, and the large number of gaps on the fabric can ensure the permeation of sweat emitted by the human body, meeting the requirements of wearing comfort; when immersed in water, the grafted gel layer swells rapidly, The pores are closed, thus providing good waterproof or immersion resistance. Through the action of this driving mechanism, the two properties of “waterproof” and “moisture permeability” can be satisfied accordingly under different environmental conditions.
Someone chose the method of electron beam pre-irradiation to Acrylic monomers were graft-polymerized onto polyester fabrics, and the fabric properties were studied. The test results show that when the fabric is grafted with acrylic acid, the fabric properties will have the ability to block water within 3S. The greater the grafting rate of the fabric, the faster the fabric will respond to water, and it will change over time. As it is extended, the water blocking capacity continues to increase until it reaches a certain value.
In recent years, with the emphasis on With the in-depth understanding of the properties of PTFE and the improvement of film-making technology, on the basis of the second functional fabric, PTFE has been developed. Functional fabricLaminated fabric. For example: Waterproof and breathable elastic fabric, Waterproof, moisture-permeable and flame-retardant composite fabric, Waterproof, breathable and moisturizing fabric, Radiation protection clothing fabricWait.
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