Datasheet

58
Weathering
Ultraviolet light (which is a component of sunlight) attacks, over a period of time,
most plastic materials and reduces their properties by breaking the molecular
chain. The material breakdown is accompanied by reductions in tensile strength
and elongation, increased brittleness, color changes and loss of surface gloss.
Carbon black, which is used in PAN DUIT
®
nylon and polypropylene cable ties,
is one of the most effective stabilizers known today. A uniform dispersion of car-
bon black provides good ultraviolet light resistance without adversely affecting
physical properties. The addition of carbon black, or any other ultraviolet light sta-
bilizer, prolongs the useful life of plastic products used outdoors, but it does not totally eliminate the
destructive effects of the light. Some plastics, such as TEFZEL

or HALAR
▲
, are intrinsically very resis-
tant to ultraviolet light and do not require stabilizing additives.
Weathering Test Methods
In order to monitor the effects of ultraviolet light and the effectiveness of ultraviolet stabilizers, Panduit, in
conformance with industry standards, adopted two methods of weatherability testing: Outdoor Aging and
Accelerated Weather Aging.
Outdoor Aging
The Outdoor Aging method is probably the best and most realistic method of the two. It is conducted in
accordance with ASTM D1435-85 Recommended Practice for Outdoor Weathering of Plastics, and
allows the material to be affected by not only ultraviolet light, but by all other outdoor elements as well.
Although this may more closely approximate an actual application, two drawbacks do exist. The period
of time required to produce property decay and material failure may be quite long and varying adverse
chemical environments cannot be tested.
Accelerated Weather Aging
Accelerated weathering tests have been used in order to increase the rate of degradation due to a com-
bination of ultraviolet light, temperature and moisture. The methods used are in accordance with the fol-
lowing standards:
• ASTM D1499-84, Operating Light and Water Exposure Apparatus (Carbon-Arc type) for exposure to plastics
• ASTM G53-84, Operating Light and Water Exposure (Fluorescent U.V. Condensation type) for exposure of
non-metallic materials
The condition specified in ASTM D1499-84 utilizes a carbon arc to simulate natural sunshine and a water
spray. The test chamber is operated 20 hrs/day with a two hour cycle of 108 minutes of simulated
sunshine and 12 minutes of sunshine and water spray. The temperature of a black body inside the
chamber is approximately 63°C (145°F) during the “Sunshine Only” portion of the cycle. Humidity is not
controlled inside the chamber.
The test chamber per ASTM D53-84 uses fluorescent sun lamps to generate ultraviolet light only. A
heated water pan produces condensation during a portion of the cycle.The daily cycle is composed of 20
hours of light followed by 4 hours of condensation. Black body temperatures during the light cycle are
50°C (122°F) and 40°C (104°F) during the condensation cycle.
Panduit has also designed a special chamber which is used to simulate the effect of acid rain and
ultraviolet light on cable tie materials. The effect of other common chemicals, such as road salt, are also
evaluated in this chamber.
These methods are effective in quickly determining the ultraviolet light resistance of the various cable tie
materials, but it must be emphasized that there are no exact correlations between accelerated aging and
actual outdoor exposure.
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HALAR is the Registered Trademark for Ausimont Inc. fluoropolymer

TEFZEL is the Registered Trademark of E. I. DuPont Co., fluoropolymer
Weathering