Crack in ABS refrigerator liner 2

[jeb]

We've had a recent problem with the ABS liner of a
refrigerator cracking in various areas when the cabinet
is chilled. The cabinet has urethane insulation (R22 blowing agent) and is cleaned with 3M citrus cleaner in production. The liner material is GE GPX3800. We are getting a chemical wash and spectrostopy tests from GE on a "destructed" sample to determine possible causes in the materials. We have built the cabinet for several years with no apparent previous problems. Are there any other tests available to analyze the stresses present in the plastic, and possible causes of failure? (We are looking at chemical compatibility, sheet composition, and "cold" thermoforming.)

 

[BLN]

Can I assume you've been using the same ABS for several years? How about R-22 and the Citrus cleaner? Has anything "new" been introduced at the time of the cracks?

You should (or maybe GE) should use an optical microscope to look at the cracks that have occurred. You can analyze the extent of the crack and may be able to pick up microcracks or other anomalies not picked up in a visual inspection.

 

[jeb]

We have been using the same ABS and cleaners since the start of production. The Assemblers have to our knowledge used the same cleaners, but the workforce is not constant and different workers may have used different combinations of cleaners. We are continuing to look at the cleaners, and feel that is a possible cause; particularly in light of the fact that I learned that GPX 3800 has relatively poor chemical resistance. We had sent a sample of the cracked liner to GE and they performed analysis and chemical wash. Results were inconclusive. Not sure how good their lab is - you would expect it would be very good, but I havn't been impressed. Thanks.

 

[BLN]

According to the literature, ABS is attacked by some solvents such as ketones and esters. I know some plasticizers are leached out of plastics in general, making them suseptible to cracking. Make a list of all the possible solvents/cleaners that could have been used (whether correctly or incorrectly) and something may jump out. I know from experience some workers will use a cleaner strictly because it was close at hand.

 

[JGPOLYBENDS]

Sir,
Shall I intervene in your problem, if I could be of any help?
Luckily I have experiences in vacuum forming ABS as well as insitu pouring of PUF inside regrigerator liner.
I feel the cause may be due to two reasons :
1.Rightly, the solvent wash - For food grade why a mild luke warm water with soap solution, be the right material for wash, as any solvent is considered not enviro- friendly?
2. PUF insulation : Basically the ratio of the polyol : iso should be well tuned, so as no unreactive component lies into the system, which in due course due to greeen house effect ( heat built up ), creates exotherm, which may result in the liner cracking up. OR The reactivity (gel & rise time especially ) of the Polyurethane system may be longer than the materials used before. Pls check if these systems' reactivity report is consistent as that of the material u were using for ages. Any change in formulation of PU may also cause exotherm, resulting in liner cracking.( Did u change material source/ vendor?), that's all I can foresee. Best of luck. Happy processing.
Chandrashekhar
chandra_jgp @satyam.net.in