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QUALITY ASSURANCE

RECIPE CONTROL

Just as today's modern bread recipes are much more than simply flour and water, the formulation for a specific polyurethane film is typically a fixed recipe containing a variety of ingredients. TPU film is rarely extruded solely from just the raw polyurethane resin. The vast majority of applications require a blend, or recipe, comprised of three basic categories of ingredients:

1. Virgin TPU Resin
Just as there are many types of flour to use as the primary ingredient in a bread recipe, the same principle is true when extruding polyurethane film. A broad array of TPU resins are available, straight out of the box, from a number of chemical companies. The basic types of polyurethane resin include:

• aromatic polyester
• aromatic polyether
• aromatic polycaprolactone
• aliphatic polyester
• aliphatic polyether
• aliphatic polycaprolactone

These fundamental classes of polyurethane are further subdivided based on variations in physical characteristics, such as hardness, elasticity, tensile properties, tear strength, melt point, lamination temperature range and abrasion resistance, to name just a few. Such property modifications are generally made at the molecular level in conjunction with the resin supplier.

In addition to TPU resins, Argotec also has expertise in extruding copolyesters, copolyamides, ether-amides, specialty TPEs and TPOs, as well as cellular sheet from aromatic polyester and polyether polyurethane. Whether the base resin is polyurethane or one of these other specialty materials, the same exacting recipe control is necessary to ensure customers the highest quality product, both chemically anddimensionally.

2. Chemical Additive Packages
The second category of ingredients included in the typical TPU film recipe are supplementary chemical additives designed to impart specific characteristics to the final film product. These carefully engineered additive packages give the film properties beyond those possible via polymeric modifications to the raw resin, including:

• color
• flame resistance
• ultraviolet (UV) resistance
• antibacterial (odor) control
• antibacterial (infection) control
• antifungal control
• antistatic control
• surface slip lubrication
• antiblock properties

3. Regrind
The use of regrind, or recycled polyurethane film, is environmentally responsible and can also be cost effective, depending on the source, ratio and cleanness of the materials used. Argotec recycles only its own film components, such as edge trim and startup materials. The use of regrind in a given film recipe is carefully controlled and limited to the same resin type, color, and chemistry.

Argotec does not buy regrind on the open market unless specifically instructed to by the customer. This allows absolute control of the "chain of custody" of recycled materials and their chemistry, as well as the ability to dictate the cleanness of the ingredients used in the final film recipe.

Use of regrind is only feasible if it is compatible with the recipe's virgin materials and can be processed to give uniform film properties. Argotec treats regrind as if it is a first-quality raw material having specifications for both quality and percentage of concentration that must be met before it is allowed in a final recipe.

While it is not Argotec policy to reduce cost by use of regrind, the practice, when requested by the customer and properly controlled, can provide certain economies. However, pitfalls of uncontrolled use of regrind can result in several problems with the finished film, including:

• Excessive gel: gel is unmelted raw material that manifests as a cosmetic blemish that will usually not affect performance. Gels can also result from using materials in the recipe that have slightly different chemistry or melt properties. In severe cases, they can appear as larger, solid pieces of material that can cause a tear or void in the film during secondary processing or end use.
• Wide variations in physical properties: use of excessive amounts of regrind, or mismatched materials, can result in variations in mechanical, tensile or elongation properties from one part of the sheet to another. This can affect downstream processability in the customer's fabrication or lamination operations.
• Extrusion processing problems: in addition to physical defects and variations in physical properties in the finished film, improperly matched and proportioned regrind has the potential of creating film extrusion processing problems which can increase manufacturing costs.

Recipe control can be effective only if the mixture of virgin resin, chemical additive packages and any use of regrind is properly formulated and strictly maintained throughout the extrusion process. Argotec uses up-front engineering to eliminate mid-run recipe changes needed to fix problems or increase yield. We believe that proper advance design of the film recipe to match exactly the customer's end-use requirements is the very best way to ensure the highest chemical quality of the finished polyurethane film and sheet.