SGS Helps Manufacturers Understand Laboratory Accelerated Aging Techniques for Outdoor Furniture
As outdoor furniture becomes more popular, manufacturers need to understand how laboratory accelerated aging processes can help them develop attractive and durable products. SGS expert, Matthew McGarrity, provides an overview of these techniques.
To help manufacturers developed attractive and durable outdoor furniture, they should test their products using laboratory accelerated aging techniques to replicate weathering processes. These procedures use aggravated environmental factors to speed up the normal aging process, thereby helping manufacturers understand the long-term effects of exposure to environmental factors in shorter timeframes and under standardized laboratory conditions.
The effects can broadly be split into two forms:
• Changes in visual properties or aesthetic appeal – fading, yellowing, color change, gloss reduction
• Changes in physical properties – cracking, peeling, embrittlement, loss of tensile strength
It should be noted, visible alterations may also be symptomatic of changes to the physical properties of the product and could therefore become a safety issue.
The Sun is the primary driver in altering the visual appearance of furniture, with heat and moisture acting as catalysts. Obviously, the outdoor natural exposure method is the most straightforward form of exposure, if time permits. The problem with this is the variability of climate at different sites means test data would only truly be applicable to the test site. Using weatherometers to accelerate sunlight degradation in the controlled environment of a laboratory is a far more sensible approach, providing greater consistency in the results.
Heat and light oxidation, (also known as photooxidation)
The two primary laboratory practices used to replicate harmful effects of sunlight are:
• Fluorescent Ultraviolet, using ASTM G154 – Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials
• Xenon Arc, using ASTM G155 – Standard Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials
These simulate sunlight alongside heat and moisture, but the primary difference is the sun's wavelength they replicate:
· Xenon Arc - full spectrum sunlight and is therefore a closer replication of outdoor sun exposure
· UV chamber - sunlight's UV band. Fluorescent UVA and UVB lamps replicate 300 – 400 nm wavelengths – where most physical damage occurs
These approaches allow manufacturers to test different facets of the aging process: Xenon Arc is best for evaluating color change of outdoor pigments and dye over time; QUV to test for embrittlement and physical change, especially in polymers and durable outdoor coatings.
It is also importance to test for resistance to extreme of temperature. To evaluate this, manufacturers can use industry methods but often their application is made redundant by the incorporation of elevated temperature tests in other aging methods.
Methods for testing include:
• ASTM D1211 – Heat and Cold Resistance
• ASTM D2247 – Head and Humidity Resistance
• ASTM C666 – Rapid Freeze and Thaw of Concrete
Another major effect of weathering is corrosion – the gradual degradation of refined materials, usually metals, into a more stable form. It occurs naturally through chemical and/or electrochemical reaction but can be accelerated using laboratory practices:
· ASTM International's ASTM B117 – Standard Practice for Operating Salt Spray (Fog) Apparatus services as the principal corrosion testing guidance document.
· ASTM B117 creates a controlled corrosive environment using a 5% salt solution that is atomized into a "salt fog". Samples are left in this environment for pre-determined amounts of time, or until a failure is identified.
In addition, ASTM D5894 – Standard Practice for Cyclic Salt Fog/UV Exposure of Painted Metal uses both UV and corrosion chambers to more closely simulate outdoor exposure. There is evidence that exposure to one element will affect the way a product reacts to other weathering agents. Materials are therefore exposed to alternating periods of UV and salt fog exposure.
One way to address the limitations that exist is to design a proper weather evaluation. To do this, it is critical to review the following factors:
• Objective: to ascertain how a piece of outdoor furniture will perform in its intended use environment. Because fool proof correlation of laboratory and real-life exposure does not exist, it is advised to corroborate test results with real-life observations in the field. These methods also allow comparison between materials – useful for material selection
• Product Construction:
• Primary Intended Use Environment: replicating the most severe use environments will limit a study's lead time, cost, and sample requirements
• Criteria: quantitative criteria are needed with results that can be used as a basis for evaluation and subsequent decision
The increasing demand for outdoor furniture means manufacturers need to be sure they are producing furniture that conforms to the expectations of consumers. SGS has considerable experience in offering efficient and cost-effective testing solutions for outdoor furniture to help manufacturers bring quality, durable products to their target markets.
To learn more about SGS Furniture (http://www.sgs.com/
For more information, please contact:
Senior Technical Manager - Hardlines
SGS - North America, Inc.
Tel: +1 973 461 1505
SGS is the world's leading inspection, verification, testing and certification company. SGS is recognized as the global benchmark for quality and integrity. With more than 95,000 employees, SGS operates a network of over 2,400 offices and laboratories around the world.