Poly Masking
Poly masking, short for polyethylene, is the most popular masking and is often times referred to as static, corona or cling masking. Historically, this product was the "cheap" alternative to paper, and did not add value to the acrylic sheet beyond the limited protection it offered. Today, premium acrylic sheet is masked with a multi-layer high-performance masking, which enables processors to leave the masking in place throughout the entire process reducing damage and virtually eliminating post cleaning steps. Many fabricators leave the masking in place even through delivery to the end user.

The adhesive mechanism for this product is a static charge, or corona treatment typically measured in dynes. The higher the dyne level the more aggressive the product. Outdated monolithic poly masking (single layer) does not perform in operatons where the acrylic sheet is subjected to heat. Mono films cannot withstand thermoforming or aggressive fabrication such as gang cutting - cutting thick stacks of acrylic sheet on saws, or high speed CNC routing.

Poly masking should have a high tensile strength and elongation properties. Corona treated poly masking is commonly used on extruded acrylic sheet products, but not cell cast acrylic sheet, because it requires a certain degree of heat at the laminating station.

Adhesive-backed poly masking
This type of polyethylene masking is similar to corona treated masking except that the bonding mechanism is achieved with adhesive rather than static or corona. Typically this masking is a low performer and cannot withstand thermoforming or other applications where heat is generated. Most adhesive-backed poly masking is monolithic and has not undergone the transformation that corona treated multi-layer polymasking has in recent years.

This type of masking is generally used on cell cast acrylic sheet where it is too difficult to generate the surface temperature that activates the corona treatment. This product may be used on textured or embossed extruded acrylic sheet as well.

Paper masking replacement (PMR)
PMR is the most recent evolution in acrylic sheet masking and is designed to blend the positive attributes of multi-layer poly and domestic paper, allowing fabricators to enjoy the best characteristics of both masking products. For instance, PMR does not rely upon adhesive or corona treatment as the bonding mechanism, eliminating the opportunity of over-or-under treatment common in corona masking , and aggression from drying adhesive seen with paper masking, meaning longer shelf life for customers. The adhesive mechanism is a sealant layer which clings to the ultra smooth surface of acrylic sheet perfectly.

This engineered product can be thermoformed, laser cut, and gang cut on saws without affecting the release characteristics of the masking. It doesn't leave a residue, has half the initial peel strength of paper masking, and will not become agressive over time. This masking is used on extruded and continuously cast acrylic sheet, which is either smooth or textured.

For more information, contact Mike at Ultra Acrylics, Inc.

Paper masking
The actual weight of the paper, usually measured in pounds per thousand square feet, needs to be considered, as do the actual constructon of the paper and the type and coat weight of the adhesive, to ensure true value and maximum shelf life. Domestic suppliers generally provide high quality paper, which is extensible-the long fibers of the paper are able to expand and contract as the acrylic sheet is subjected to changes in ambient temperatures and humidity. However, most paper masked imported acrylic sheet is masked with a low quality "rice" paper which is not extensible and has lower tear or tensile strength making the product more difficult to remove.

The adhesive type and coat weight play an integral part in the product's ability to withstand tunneling or bubbling. Domestic suppliers use a proprietary blend of natural and synthetic rubber, applied evenly to ensure uniform adhesion. Low adhesive coat weight, a common problem on some emport paper masked acrylic sheet, is a leading contributor to reduced shelf life. As this adhesive dries out, it hardens, becoming more aggressive and diffucult to remove.

Paper masking is genrally the most expensive protective masking used on acrylic sheet, and has a limited shelf life. Paper masking is used on cell cast and extruded acrylic sheet.

For more information, contact Mike at Ultra Acrylics, Inc.

A simple characteristic such as post-forming peel strength can have a profound affect on the productivity of a fabrication department. There are five steps to determining the proper masking for fabricated parts, and among these base price may actually be the least important. However, it is important to first understand the basic terminology of masking in order to apply these five easy steps.

There are currently four types of masking used to protect and add value to premium acrylic sheet. Paper masking, poly masking, adhesive-backed poly masking and paper masking replacement (sometimes referred to as PMR), all have very specific applications. Some of these products have been used for decades, while other products such a PMR - complicated, multilayer, engineered masking - are new to the market but all have very specific jargon and properties which, once understood, can help purchasing managers make informed decisions.

Paper Masking
This product has the most history protecting acrylic sheet and is often the default masking of choice for many distributors and fabricators who want to ensure protection. However, not all paper masking is created equal and there are several characteristics which need to be considered when evaluating the quality of this product.

Acrylic sheet is widely considered one of the best products for intricate fabrication projects which require stunning visual clarity and unlimited design characteristics. This fact is most predominate in P-O-P displays, where fabricators employ countless tools and techniques to achieve eye-catching designs to enhance store level presentation at well-known retailers. Sophisticated equipment such as CNC routers and saws, precision laser cutters and thermoforming equipment are routinely used to shape acrylic sheet, making this product the most versitle see-though thremoplastic on the market.

One of the most important features which must be considered when choosing acrylic sheet is often the most overlooked - masking. Masking is no longer simply packaging but is in fact an important part of the "package." Today's advances in manufacturing now provide fabricators with several choices of masking to consider when purchasing acrylic sheet.

Masking is no longer simply a protective barrier- although this is an obvious characteristic-but is instead a functional aspect of the overall acrylic sheet product. Masking can now be evaluated in features and benefits which go way beyond the traditional identity of older monolithic type masking products. Purchasing managers must now identify these time-saving characteristics to ensure they have created manimum value for the manufacturing department.

For more information, contact Mike at Ultra Acrylics, Inc.

Shrinkage
Because of the orientation imparted during manufacture, acrylic sheet shrinks slightly when heated to thermoforming temperatures.

Original dimensions won't change in fabrication operations not requiring heat or if the acrylic sheet is heated while clamped in a frame. However, unrestrained sheet heated to thermoforming temperature changes dimensionally. Continuously manufactured sheet changes by up to 3 percent maximum shrinkage in the manufacturing direction and 0.5 percent maximum width increase (transverse direction). Manufacturing direction can be determined from the sheet label or print on the masking. The lines of print are perpendicular to the direction of manufacture. Cell cast sheet will shrink up to 1.5 percent in both directions.

Measure the shrinkage in a preliminary test. Then, determine the size of material required to compensate for shrinkage before cutting any blanks.

Predrying
Predrying acrylic sheet is rarely necessary. Keep the sheet wrapped until used. To prevent blistering, dry high-water content sheet in a forced-circulation drying or vacuum oven before heating. Drying time depends on water content and material thickness. Twenty-four hours at 176 degrees F (80 C) dries most sheets.

To reduce length of the forming cycle, pre-dry the sheet in a spare oven and transfer it directly into the forming oven at 176 degrees F (80 C) after the dring period.

For more information, contact Mike at Ultra Acrylics, Inc.