LU-8009 QUV & Q-SUN: A Comparison

The Need For Testing 

Light, high temperature, and moisture can cause damage to coatings, plastics, inks, and other organic materials. The resulting damage can be seen in many different types of polymer degradation. These include changes in physical properties such as cracking, peeling, embrittlement, and loss of tensile strength; as well as visual properties such as gloss loss, fading, yellowing, color fade and color change. 

For many manufacturers, it is crucial to formulate products that can withstand weathering and light expo - sure. Accelerated weathering and light stability testers are widely used for research and development, quality control and material certification. These testers provide fast and reproducible results. 

Two Different Approaches 

QUV ® accelerated weathering testers and Q-SUN ® xenon test chambers are both affordable and easyto-use apparatuses for laboratory weathering tests. The QUV tester meets the requirements of ASTM G154, ISO 4892-3, and others; the Q-SUN tester meets ASTM G155, ISO 4892-2, and others. 

This paper will explore the ways in which these two testers differ, including light spectra and method of moisture simulation. The inherent strengths and weaknesses of each tester will be discussed, including purchase price and operating costs. Guidelines will be given for which tester is generally recommended for a particular material or application.

Historical Perspective 

While it is clear that weatherability and light stability are important for many products, the best way to test is sometimes controversial. Various methods have been used over the years. Most researchers now use natural exposure testing, a fluorescent UV apparatus, or a xenon arc apparatus. 

Natural exposure testing has many advantages: it is realistic, inexpensive and easy to perform. However, many manufacturers do not have several years to wait and see if a “new and improved” product formulation is truly an improvement. 

The Q-SUN (xenon arc) and QUV (fluorescent UV) are the most commonly-used accelerated weathering testers. The two testers are based on completely different approaches. The xenon test chamber reproduces the entire spectrum of sunlight, including ultraviolet (UV), visible light, and infrared (IR). A xenon arc lamp with appropriate optical filters essentially simulates sunlight itself from 295 nm - 800 nm (see Figure 1 below).

The QUV Accelerated Weathering Tester, on the other hand, does not attempt to reproduce sunlight, just the damaging effects of sunlight that can occur from 300 nm - 400 nm (Figure 1). It is based on the concept that, for durable materials exposed outdoors, short-wave UV causes the most weathering damage. 

Which is the better way to test? There is no simple answer to this question. Depending on your application, either approach can be quite effective. Your choice of tester should depend on the product or material you are testing, the end-use application, the degradation mode with which you are concerned, and your budgetary restrictions. 

To understand the differences between Q-SUN and QUV testers, it is necessary to first look more closely at why materials degrade.