PP versus PE

The physical properties of synthetics are essentially those of the polymers from which they are made. The king of the polymers is polyethylene, or PE. It is produced in the highest volume globally and its production (or consumption!) is considered a measure of industrial growth.

The second most common polymer in the world is polypropylene, or PP. According to a report from GBI Research, the global PP market is predicted to reach 62.4 million metric tons by 2020. In terms of end-use consumption, construction currently accounts for 5 percent of the PP market.

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Thickness versus GSM

Synthetic underlayment products are frequently characterized in terms of weight or, more precisely, areal weight, so it's worthwhile to examine what exactly is meant by the “weight per unit area”.

The units for areal weight are typically given as grams per square meter (GSM). Areal weight is easy-to-measure and meaningful. It describes the amount of polymer in the underlayment, allowing synthetic underlayment products to be compared to each other and also to other types of underlayments.

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Weaving Plastic Scrims

There is more to scrim than meets the eye.

The scrim is woven from polypropylene threads or filaments. Scrims are used in everyday life to bag oranges, grapefruits and onions in the food processing industry. One can see them at local grocery stores or in the refrigerator.

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Slippery When Wet

The roofing industry initially was reluctant to adopt the new synthetics. By way of comparison, the industry literally had decades of experience with modified bitumen. As a result, residential roofing contractors were eager to adopt the premium self-adhering underlayment and these were readily accepted by the industry as a premium underlayment.

For residential roofing, it has been argued that the underlayment need only shed water because of the steep slopes of the roof. And furthermore, the primary roof (whether shingle, tile, metal or other material) protects the underlying material from ultraviolet radiation.

Such arguments led to the idea of using an extremely thin layer of plastic as an underlayment. But experience with the synthetics was lacking. Synthetic underlayment gained notoriety as being unsafe because the sheets would become slippery when wet. Especially the early versions were deemed unsafe and hence many contractors preferred to use familiar materials.

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Know Your Scrim and Sheets

Considering that the last fifty years could be arguably called the “age of plastics,” it is not surprising that polymers have found a niche in residential roofing.

Between the quality level of the traditional asphalt-saturated organic felt and that of premium modified bitumen underlayment, there is room for a mid-grade quality in the form of synthetic underlayment. The “synthetic underlayment” product category is capturing market share from conventional felt as well as the premium self-adhering underlayments. These thin sheets of plastic can be used beneath shingle, tile or metal, where their light weight feature results in major labor savings for roofing contractors.

Read more: Know Your Scrim and Sheets
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Quick Reference Product Guide

Custom Printing

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Every roof is a billboard with our custom printing program! Get our LeakBarrier EasyLay UDL Synthetic Roofing Underlayments custom printed with your company logo, phone number, website – whatever you want to promote your business! Custom printing is available for: EasyLay UDL 15, EasyLay UDL Basic & EasyLay UDL 50.

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