PFFC - December 2007 - (Page 31)

MATERIALS TESTING Products that fail due to light exposure u An attractively colored blue mouthwash was found to gradually turn a sickly shade of green after only a few hours of exposure to certain types of in-store lighting. Fortunately, this was observed early as different lots of material reached the store shelves to be placed next to older inventory that showed early signs of this color decay. u Many of the non-cola drinks contain artificial color components. The producers of these products have learned to do lightfastness studies before market introductions. Cola is subject to photodegradation as well. u A manufacturer of a fabric deodorizer discovered that when the bottle of product was allowed to remain in vehicles with exposure to light, the product changed from deodorizer to a very malodorous aerosol. u Certain types of fluorescent store lighting cause deterioration of whole milk products in transparent or translucent glass or HDPE bottles. u In addition to product photodegradation, print fading on the package is a common problem in cases where non-stable inks are used. High chroma organic pigments and dyes are much more susceptible to light than some of the older systems. Most stable of all is the oldest: carbon black. Increasing use of inkjet printing will mean that greater care will need to be taken so that the graphics do not change color faster than the anticipated shelf life of the product. Finding Solutions Two Principal Methods So what is to be done? The first step is to determine whether there could be a problem of poor resistance to light energy for some specific product. The second step is to determine how to protect against a negative outcome. It is obvious the best approach would be to test the actual product/package/label in the environment anticipated for its use for the maximum time of expected exposure. This has some obvious drawbacks, both in terms of the time it will take and, more importantly, in anticipating all of the different potential exposures possible. As mentioned previously, the best test in every case is to duplicate the end-use exposure and place the package in that environment for as long as exposure is expected to last. The next best approach, however, is to use existing instrumentation to attempt a close parallel to anticipated conditions and then expose the package accordingly. The two principal methods currently available are instruments based on xenon arc light sources or, alternatively, instruments based on UVproducing fluorescent lamps. Methods are available to use the light from xenon arc lamps to duplicate, with appropriate Test samples inside a xenon arc light flatbed instrument chamber. Therefore, we usually resort to an FMEA (Failure Mode and Effects Analysis) to determine a best estimate of possible failure modes and the cost balance of their occurrence. From this we can determine the worst exposure that must be overcome. Note this does not mean that we plan against every exigency. We need to deal only with those that will have a significant cost or image impact. With this analysis in hand, we have access to laboratory testing options. filters, either indoor or outdoor light. They can duplicate, with reasonable accuracy, outdoor sunlight or, alternatively, sunlight as viewed through window glass or other screening elements. Photo courtesy of Milliken Chemical Div., Milliken & Co. Figure 1. Image on left shows the intended product appearance, while the image on the right shows the product faded by UV light. The filtered xenon arc lamp provides a full spectrum exposure, including the visible and infrared wavelengths. It is known that many products as well as the colorants used in packaging and inks are sensitive to visible light as well as UV, so testing with a fullspectrum xenon arc light source provides the greatest range of exposure conditions to both outdoor and glass-filtered sunlight as well as indoor artificial light. However, if the UV wavelengths are of particular concern, preliminary screening tests with fluorescent devices using UVA lamps may be an economical first step. The second method uses controlled irradiation fluorescent lamps to provide measured quantities of a narrow spectrum of UV light. Because the UV wavelengths are those that do most of the damage to most products, using this method often is sufficient. We strongly recommend that users of fluorescent UV devices employ the appropriate bulbs that mimic the short wavelength UV that occurs in the intended end-use application. Figure 2 and Figure 3 are examples of these two instrument types. The xenon instrument (Figure 2) has air-cooled lamps, an exposure surface of approximately 400 sq in., and irradiance, temperature, and humidity control. Fluorescent instruments, like the one shown in Figure 3, also are widely used and provide temperature/humidity control as well as controlled irradiation within fixed, though truncated, parameters and exposure area of approximately 1,000 sq in. Figures 2 (left) and 3. DECEMBER 2007 | 31 WWW.PFFC-ONLINE.COM http://WWW.PFFC-ONLINE.COM

Table of Contents Feed for the Digital Edition of PFFC - December 2007

PFFC - December 2007 Table of Contents First Glance From the Editor Web Lines Process Management News Clips Narrow Web & Label Reporter Narrow Web & Label What’s New Products Carton & Box Reporter 2008 Calendar of Events Materials Testing Pilot/Lab/Technical Facilities What’s New Products Services Directory Classified Marketplace Advertisers Index Experience Speaks

PFFC - December 2007

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