Fabric waterproofing is a special requirement for outdoor products’ performance; there are two kinds of waterproofing: water-repellent and waterproof.
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Water Repellent
Usually, the business requirements of water repellent are omitted. The exact name is “water repellent. “, the common way is the hydrophobic compounds of the additives are added to the shaping machine into the cloth at the liquid tank, the fabric is introduced into the liquid tank by soaking and rolling, drying is completed, the formation of hydrophobic compounds on the surface of the fiber deposits.
Hydrophobic compounds can change the surface tension of the fiber so that its activity is limited, reducing the adsorption of water molecules by the fiber (fiber surface tension is less than the cohesion of water molecules), the water in the fabric to form rollable water droplets (like a lotus leaf as “open” dew), also known as “water repellent.” “Water repellent (water repellent), abbreviated as W/R.
As illustrated in the figure below, the pores of the fabric allow air and water vapor to pass through, but the water stays for too long or under certain pressure, it will still penetrate or even absorb water. When wearing a garment with water repellency on a rainy day, water droplets can roll off or be shaken off, but whether the inner layer of the canopy and the canopy inside will get wet depends on the rain quantity and the time it stays in the rain.
The umbrella surface’s waterproof effect will also be affected by washing and long-term use and gradually attenuate until failure. Therefore, the essence of waterproofing is to reduce the adsorption of water on the fabric. It is not really completely waterproof, but we are accustomed to simply referring to it as “waterproof.”
Waterproof
Waterproof is the real sense of waterproof. English is waterproof (waterproof, water blocking), meaning to resist and block water penetration, which is really waterproof. True waterproof fabric in waterproof durability can crush the waterproof fabric. Its physical and chemical properties are more stable, usually not due to washing and long-time use and failure.
A true waterproof treatment aims to form an impermeable barrier on one side of the fabric, which requires a high water pressure rating, e.g., 3000mm water column or more. Anti-penetration is generally done on the bottom side of the fabric with an adhesive backing or film to block water infiltration. Common methods are coating (coating) and lamination (lamination), which are two kinds. The coating is the fabric coating glue or film coated on the fabric side, forming a waterproof film to achieve the function of anti-infiltration.
Common methods are direct coating (dry, wet, hot melt) and transfer coating.
The laminating method is to make the fabric composite layer of waterproof film material (commonly known as “waterproof membrane”) become whole, regardless of whether the fabric is waterproof, and the waterproof membrane always plays a role in waterproof penetration of the fabric fit; laminating another way is the hot-melt calendering so that the fabric bonded to a layer of polymer waterproof film to become one, to achieve the purpose of waterproof penetration of water. Purpose.
True waterproof (impermeable) performance, measured and judged by the water pressure resistance value, water pressure resistance value expressed in a “millimeters high water column.”
With a fixed area of waterproof fabric to block the test container from the contact surface of the water penetration to the other side (surface), continue to raise the water pressure when the surface of the third droplet of water seepage corresponding to the value of water pressure that is the fabric’s water pressure resistance value. Usually, fabrics with a water pressure of more than 1000mm high water column can achieve the basic waterproof ability.
The author Justin works for a well known umbrella manufacturer, if you have umbrella needs or questions, please contact: Justinzhang@hfumbrella.com
