Volume 5, Issue 6        November/December 2003


Independent's Day         an iga viewpoint___________
The PVB Dispute 
by Tim Smale

"The qustion remains, is what Solutia states in its report a cause for concern?"

In my last article, I wrote about a recent study that was performed on polyvinal butyral (PVB), (see September/October 2003 AGRR, page 14). That article and the Independent Glass Association’s (IGA’s) recent investigation into damaged windshields has been misunderstood largely and caused confusion with some people in our industry. 

The primary issue we investigated is the tendency for PVB to absorb moisture when a windshield is damaged and any possible subsequent safety risks. The IGA’s focus is not whether or not windshield repair is safe. I admit that the headline in my last article “Is Windshield Repair Safe?” was misleading and may have led to the assumption that the IGA was against windshield repair. 

I regret any confusion this headline may have caused and want readers to know that we are staying focused on the PVB issue and not attacking windshield repair. 

I have met with various members of the windshield repair industry, including the National Windshield Repair Association (NWRA) board of directors, to emphasize this point and ask cooperation to help investigate this matter further.

A Recap

To recap, the IGA commissioned Solutia Inc. to conduct a study of PVB’s absorption of moisture when it is exposed to air and the subsequent potential for the broken windshield to dislodge glass particles (called spalling) upon impact. 

Solutia’s test of seven repaired windshields concluded that spalling does occur if PVB has been exposed to moisture in the air. From the beginning, I have cautioned that Solutia’s test is not conclusive because it was performed by what some would feel is a biased party and the sample size was small. The results simply indicated that further study is necessary. 

Further Questions

The question remains: is what Solutia states in its report a cause for concern? And, if its findings are true, what does this mean for our industry, and does it affect windshield repair? Let me state clearly that our original intent merely was to seek industry comment and conclusion on the matter, not to take a position on whether or not it is true or false. We simply do not have enough information to come up with any conclusion other than the fact that more investigation is warranted. 

The testing and conclusions performed by Solutia were consistent with a similar study commissioned by the National Glass Association (NGA) in 1993. I have learned since writing my last article that in 1993 the NGA formed a committee to investigate these matters and there are various interpretations as to whether or not the issue was resolved at that time. Those who feel that the issue was resolved are criticizing the IGA for investigating what they feel is a dead issue. 

Some repair manufacturers believe the issue has been resolved based on private testing of their own products. Understandably, they do not want to share the results with us for fear of it getting into the hands of their competitors. Most of these companies are IGA members, and these reputable companies stand behind their studies. 

Other people believe it’s a resolved issue based on a subsequent study by the Insurance Institute for Highway Safety (IIHS). The study concluded that damaged, unrepaired windshields that were soaked in water for one week spalled upon impact in approximately equal amounts as damaged, unrepaired windshields that were not soaked in water. From this they concluded, “The risk of interior windshield glass spalling from non-collision impacts does not increase when damaged windshields receive even extreme exposure to moisture.” 

I learned in a recent visit with OEM windshield manufacturing engineers that PVB absorbs moisture rapidly (called moisture absorption) when exposed to air, but the moisture spreads slowly to other areas beyond the damaged section (called moisture diffusivity). The rate of moisture diffusivity in a broken windshield is only about .00004 inches per minute at 25 degrees, or about a .4 inch in a week. 

It is also dependent on two factors; the amount of PVB surface area exposed, and the temperature. Larger cracks and higher temperatures speeds diffusivity. 

Taking all of this into consideration, the IIHS study results seem to be expected; since moisture migration in PVB is very slow, one would not expect windshields that were water-soaked for one week to spall more.

To me, the IIHS study conclusion only emphasizes that broken windshields spall upon impact and confirms that I need more information in order to make any conclusions. 

Search for Answers

Since the studies I have reviewed are not conclusive and could be perceived as biased since they were sponsored by manufacturers of windshields, PVB, repair products or an insurance institute, I believe we need more information. 

We need strong evidence for one side or the other to determine if PVB’s absorption of moisture in broken windshields is a safety concern or not. I suggest that our industry bands together and commissions an independent lab to perform a battery of conclusive tests that are supported by all, thereby eliminating the potential for bias. 

The PVB moisture issue had lead to related discussions about when and where to repair windshields, and I believe that the glass industry would benefit from having clear guidelines to follow when repairing windshields. Therefore, I advocate the development of an ANSI standard for windshield repair. 
Just as the development of the ANSI/AGRSS windshield replacement standard by industry leaders resulted in the documentation of industry best practices based on sound testing, so, too, can an ANSI repair standard help us all determine when and where to repair windshields. 

I have invited industry leaders from both the repair and replacement side to join me in supporting the development of an ANSI repair standard, and so far, the feedback has been positive.

The IGA board of directors has not discussed doing any additional investigation at this time, though I will continue to stay abreast of any industry developments regarding this issue. My primary focus to help independents everywhere remains on steering and underpayment issues.

Tim Smale is the chief executive officer of the Independent Glass Association, based in Idyllwild, Calif.

© Copyright 2003 Key Communications Inc. All rights reserved. No reproduction of any type without expressed written permission.