RAPTOR^® LOW/HIGH TEMP PERFORMANCE

RAPTOR^® polymers have an optimum operating temperature range (at which they can be driven) from at least -50C (-58F) to at least 65C (150F), while polymers used for staples such as the Kowa brand have an optimum operating temperature range from about -10C (15F) to about 65C(150F). RAPTOR^® can be successfully driven at very low or quite high temperatures. The technical reasons for these differences are described below.

Polymers undergo a dramatic change in properties at a temperature that is unique to each polymer. This temperature is called the glass transition temperature (Tg). The glass transition takes place over a temperature range. When the polymer is cooled below this temperature, it becomes hard and brittle. Above the Tg, it can be tough or rubbery. Depending on the application, polymers may be used above their glass transition temperature, or below their glass transition temperature. If a polymer is below its Tg, it is brittle. This does not mean poor performance for an application unless it actually fails. The Tg does not put a lower limit on the service temperature for end-use polymers, it simply indicates the temperature at which brittle fracture becomes the dominant failure mechanism.

Polymers that have a Tg greater than ambient temperature are in the glassy/brittle state at ambient temperature. Examples of these are plastics such as PS, PMMA and PET. These plastics tend to be brittle and, if they are stressed beyond their design, they will fail in a brittle manner. They are successfully used for thousands of applications even though they are brittle. The RAPTOR^® composite has a Tg about 120°C and its Tg does not change much with humidity. RAPTOR^® composite is designed to be driven into a substrate when it is BELOW its Tg, whether it is driven at 105°C or at -40°C. Driving into a substrate is the most demanding requirement for impact driven fasteners. Since RAPTOR^® is already below its Tg, temperatures colder than -40°C will not change the drivability of the RAPTOR^® fastener measurably.

Nylon is a polymer that is used for non-RAPTOR^® plastic staples and it has a Tg about -20°C for typical humidity in the U.S. For applications using nylon, the material is ABOVE its Tg. When using nylon at lower temperatures, the material becomes brittle and no longer functions as intended. It will fail when trying to drive it as an impact driven fastener at low temperatures. This type of material exhibits a dramatic change in performance as the temperature gets colder.

Finally, the properties of the RAPTOR^® composite may not be the only considerations for successful driving RAPTOR^® at low temperatures. Tool performance and frozen wood could affect drivability of RAPTOR^® at low temperatures, so tests were done in a cold room at -40°C (-40F) with frozen pine, poplar, MDF and oak with tools and fasteners and wood conditioned to this temperature. Analysis of the results showed there was NO difference in drivability performance at -40°C (-40F) compared to drivability performance at 23°C (74F).

RAPTOR^® HOLDING STRENGTH WITH CHANGES IN TEMPERATURE

Once RAPTOR^® is driven, the forces on the staple due to temperature changes should be small. The coefficient of thermal expansion for the RAPTOR^® composite material and for wood is not dramatically different (see table below, medium density wood is listed), so any forces from dissimilar expansion will be small. We have had no issues with the installed RAPTOR® fastener failing due to changes in temperature.

If RAPTOR^® is driven into wood and then the temperature is raised above the Tg, RAPTOR^® will continue to hold because the reinforcing fibers and the crystalline structure remain intact. RAPTOR^® can be continuously used at 150°C and can be used for short duration at 260°C (after being driven at lower temperatures).