PVC Discoloration ("pinking")

PVC fabrics are used extensively in boats. Glen Raven Fabrics decided to hire Pastic Expert Group to figure out the root cause of the PVC discoloration. We performed extensive analysis of discolored PVC fabrics to identify the chemistry taking place in the fabric that was causing the discoloration (called "pinking"). We discovered that the amine catalyst in the polyurethane foam backing underneath the PVC was migrating into the PVC causing it to degrade and discolor. Glen Raven published the results of our work in Marine Industry magazines in order to get the word out that the root cause of the discoloration problem had been finally figured out (see http://marinefabricatormag.com/2014/05/01/the-science-of-vinyl-discoloration/).  

Failure of Automotive Pulley Caused by Defective Part Design

In an effort to reduce automobile weight and increase fuel economy, automobile manufacturers are replacing metal parts with lighter weight materials. However, critical automotive components and could lead to serious injury if failure occurs, should always be made using metal. For example, some automotive companies have replaced metal pulleys in the engine compartment with synthetic composite materials. If a failure of a pulley occurs in the engine, the engine stops. When the engine suddenly stops while traveling at high speeds, a serious injury or death may occur. A case in point, a car was traveling at a high rate of speed on a California freeway. The glass fiber reinforced composite pulley suddenly broke causing the engine to suddenly stop. Power steering was lost. Because the car's battery was weak, the lights dimmed. The result was a rear end collision that left the passenger dead. Our analysis of the failed pulley revealed significant design and manufacturing defects in the pulley. 

Blow Molded PVC Bottle Failure

 

Before using a bottle to contain a chemical solution, chemical compatibility testing should be performed to ensure that the chemicals are compatible with the bottle material. As an example, we recently were asked to determine why a blow molded PVC bottle ruptured allowing gelled ethanol to spray onto a child. Ethanol is only marginally compatible with PVC. Residual stresses in te material from the blow molding process in combination with a large wall thickness variation in the bottle wall led to the bottle failure. Finited element analysis predicted the location of the failure.