In situations where heat sealing is used to bind materials together, there are two main methods of heat sealing that apply to both home sealing and the more industrial manufacturing used by companies like Vinyl Technology: impulse and constant heat. Impulse sealing machines only heat up for the exact amount of time it takes to make the bond and then rapidly cool. This method uses less power than other methods and is best used for thinner fabrics that also tend to have a lower melting point. Impulse heat sealing is the kind you probably use at home. Constant, or direct heat sealing is just what it sounds like. It typically uses two opposing elements, like metal bars, that are constantly supplied with power. This means that they’re also constantly hot, in order to maintain the higher average temperature required to make the required bonds. This method is the preferred heat seal for thick fabrics like mylar, because of the high heat it uses. For PVC fabric welding using RF, radiofrequency energy is applied through electrodes custom-built to the required shape. This custom-created mold makes RF sealing the most versatile of the polymer film sealing methods because so many shapes can be created. RF sealing uses a precise combination of time, pressure, and RF waves to form a stronger, more uniform weld than is possible using other methods. PVC has the advantage of being lightweight and durable. PVC is considered to be an excellent material for radio-frequency welding because of its strong dipolar moment and other chemical properties.