SEF Americas Heat Transfer Blog: Evaluating Heat Transfer Films

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How do you determine if one brand of heat transfer film is better than another? Today, most flex films are polyurethane. But not all polyurethane films are the same. In fact, the difference from one brand to another is staggering. Here’s what to look for in comparative shopping:

FLEXIBILITY. All polyurethane stretches more than vinyl. This characteristic is critical, because fabrics stretch. And the popular performance fabrics, such as DriFit and UnderArmour, stretch significantly more than traditional textiles. In making your selection, test the various brands side by side to see which is more stretchable after the applique is applied to the garment.

SOFTNESS OF HAND. The old heat transfer vinyls were stiff as a board, and just as uncomfortable. Some polyurethane films are nearly as stiff. Comparing products simply involves touching the applied graphics to decide which film has a softer hand.

CUTTING, WEEDING & HANDLING. Many flex films have a tacky pressure sensitive carrier or backing sheet. The tacky carrier makes cutting and weeding easier. In testing products, you should rate the films based on cutting and weeding characteristics. After weeding the films, stack one finished graphic on top of another. Ideally, stacked graphics pull apart easily with no damage.

In evaluating cutting and weeding characteristics, put the candidate products to an extreme test. A design with fine detail will help you rate the performance of the different films.

LAYERING. Some brands of heat transfer films have limitations when heat pressing one color on another. On this matter, you need to ask the suppliers whether you can layer any color on top of another and if there are any problems in layering particular colors.

ADHESION TO FABRIC. Testing the adhesion of the film to fabric is one of the most important criteria. After transferring the films, stretch the fabric to the extreme and pick at the edges to determine at what point will the product fail. In evaluating the adhesion of products to various fabrics, keep in mind that special fabrics require special adhesive solutions. For example, some of the new performance fabrics and coated surfaces require heat transfer films with adhesives designed for those specific applications. Your supplier can help you select the right product for the application.

DURABILITY. Polyurethane appliques are durable. They will withstand washing after washing. Unlike vinyl transfers, polyurethane won’t crack. With proper care, polyurethane heat transfers should last the life the garment. The test that I have used in evaluating products is to apply the various candidate films on the same fabric, and after washing the garment multiple times, rate the performance.

NOTE: Buyer beware! PVC heat transfer films are often considerably less expensive than polyurethane films. These films are thicker, less flexible and less durable than polyurethane. After multiple washings, PVC heat transfer graphics tend to become brittle and crack.

ECOLOGICAL REQUIREMENTS. Ask your suppliers whether their heat transfer films have been tested for harmful substances as well as what test standards were used in the evaluation. If you are a shop owner in the United States, you should also find out if the films satisfy CPSIA requirement for lead in children’s articles.

ABOUT SEF: For more than 35 years, SEF has provided the screen printing and garment industries with high quality flex films and flock films. Manufacturing at SEF is totally integrated. The factory formulates, casts and adhesive coats its own polyurethane (PU) films. SEF even manufactures its own flock fibers. With a corporate commitment to a greener environment, all of its film and adhesive formulations are water based. This ensures that no solvents pollute the atmosphere. Its only emission is water vapor. Today, SEF is recognized as a leading producer of heat transfer films for used in the fabrication of heat press appliqués for textile decoration. Its ultra-thin polyurethane films and super soft flock films are easy to plotter cut and digitally print.

FOR TECHNICAL SUPPORT: SEF Americas provides a toll-free technical support service at 844-720-9601. NOTE: If your call is not answered by a tech support person during normal business hours, 8am to 5pm EST (Eastern Standard Time), please leave a message and we will do our best to return your call within an hour. Should you need to contact us after business hours, an alternate tech support number is 480-987-8028. You can also get answers to your technical questions by emailing: techsupport@SEFamericas.com.

About this blog: SEF Americas Heat Transfer Blog is dedicated to providing technical information about flex and flock films for heat pressing appliques to textiles. SEF, a leader in flock materials and polyurethane films, serves the garment, sign and screen print industries. SEF brands include Tatoo, Classicprint, Clearflex, Fiberplus, Metalflex and Reflexcut.

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