January 2012

PSI News: Alligators, Skittles and Beer

In this issue:

=> Feature Story: Why the Alligator Lost Its Air: A Failure Analysis
=> Feature Story: Geographical Authentication of Beer
=> Employee Profile: Alan Sentman
=> Upcoming Events: Plastics Today Webinar
=> Polymer Solutions Newsblog: Top Five Stories This Month
=> Company News and Notes

Why the Alligator Lost Its Air: A Failure Analysis

by James D. Rancourt, Ph.D.
Founder and CEO, Polymer Solutions Incorporated

Failure Analysis

Sheets of Plastic, Welded Together

Vinyl, olefin, and other plastic and elastomer materials are produced in sheets and as roll goods. From there, die-cutting, slitting, and trimming operations are used to created specific sizes and shapes from the sheets. No matter what width sheet is produced, there are times where joining several sheets is required in order to make a product.

Membrane roofing for industrial facilities, geotextiles for landfills, and production of three-dimensional inflatable structures all require the joining of sheets.

Many methods are used successfully to bond multiple sheets of plastic and elastomer materials. Solvent welding, adhesives, thermal bonding, ultrasonic welding, and physical stitching are some examples. In cases where high throughput and fluid-impermeable bonding are required, ultrasonic welding is a common fabrication method.

Experience and robust experimentation, often using statistical methods such as Design of Experimentation (DOE) methods, are used to optimize the ultrasonic frequency, horn, anvil, pressure, duration, and the rate at which these parameters reach their peak value. Typically, after these parameters are optimized, many seams are successfully welded, producing useful articles of commerce. Occasionally, however, things go wrong.

Failure Analysis

When a product does not behave as expected, it is claimed to be "a failure," and often a failure analysis ensues. The purpose of the failure analysis is to determine the root cause of the failure, identify corrective actions and preventive actions, implement process improvements, and verify effectiveness.

The failure analysis and determination of root cause can follow many paths; some may be based on experience whereas other paths may be highly analytical, scientific, and objective. The scientific methodologies that are required to "rule-in" or "rule-out" potential contributors to product failure are often straightforward to identify and implement. A major difficulty often encountered, however, is a complete and accurate description of the failure scenario itself.

Analyzing the Alligator

This failure analysis example pertains to an inflatable alligator that lost its air. While it may be argued that the actual product was a crocodile, not an alligator, the anatomical features were determined to be those associated with Alligator mississippiensis rather than Crocodylus acutus.

The initial failure analysis step involved a determination of"mode of failure." Did the alligator lose air because of the permeability of the plastic material, because of a pinhole or other spot defect, or because of an issue with a seam? Visual inspection, with digital photo-documentation, revealed that a welded seam had "let go."

The failure analysis now focused on attributes of the seam itself, in the failure zone. Possible reasons for the failure can include improper bonding, surface contamination, and weak polymer film. It is also possible that the inflatable alligator was properly manufactured but had been misused or abused. A portion of the failure description was, "One minute the alligator was fully inflated, and actually had been for quite a long time, and the next thing we knew. . . it lost its air."

Studying the Seams

Improper bonding and surface contamination were assessed using optical microscopy and scanning electron microscopy. It was evident from the images that the seam had originally been properly welded. A non-failed region of a seam was tested using a tensile tester. The data set indicated that the seam strength greatly exceeded the forces exerted by the inflation pressure. Also, comparison of the intentionally "failed" seam verified that the failed seam had been properly bonded. The compositional attributes of the plastic sheet material were determined using infrared spectroscopy, thermogravimetric analysis, and gas chromatography-mass spectrometry. No differences were noted when comparing a non-failed region with the failed region. Additionally, gel permeation chromatography was used to compare the molecular weight of the polymer in the two regions. Again, no differences were noted.

Scientific methodologies were used to evaluate potential root cause contributors to the air-loss failure. Manufacturing defects and process issues were ruled out, and were reported. The investigation continued with an eye toward misuse or abuse. A worker was located who had actually recorded critical aspects to the product failure. A 300-pound sandbag had been dropped from a height of 12 feet directly onto the alligator's torso, and rapid air loss resulted.

It was determined that the failure of the alligator was related to abuse, not a manufacturing defect, and not a material defect.

Let Us Wrestle Your Gators!

Intentionally whimsical, this description is actually very close to the reality of many failure investigations pertaining to consumer products, some of which become litigated matters. Highly detailed science-based analytical methodologies can be used to "rule-in" and "rule-out" potential contributors to failure. On some occasions, specific material or process issues are revealed, and those deficiencies are corrected. In other cases, the failure is highly unique and is the direct consequence of misuse or abuse. If your "alligator loses air," give us a call.

Images courtesy of Polymer Solutions Incorporated.

Feature Story:

Geographical Authentication of Beer

by Rachel Petkewich, News Editor
Polymer Solutions Newsblog

For folks who do not have the kind of refined palate that can help them distinguish where beers were made, researchers at the University of Seville in Spain have devised and published an analytical method to help.

For beer producers, it comes down to protecting and marketing a product. "Authenticity and geographical identification studies are 'very important' for the food industry 'given that they allow the differentiating characteristics of a product to be established. This can have an impact of their marketing,'" the researchers said in a statement. For example, the European Commission of Agriculture and Rural Development, which keeps track of products with ties to geographic origin, has registered 20 brands of German, Czech, and British beer in its Database of Origin and Registration.

These Seville researchers have experience in the field of food authentication: A quick scan of their publications shows that they have also authenticated the origins of tea leaves and tequila, and confirmed the diet that was used for fattening a pig.

Identifying beers, explained chemist and team leader José Marcos Jurado in a statement, depends on elucidating unique chemical patterns related to raw materials used for brewing, such as metals and anions in water, and polyphenol content related to the type of hops.

Here's the gist of how they conducted their study. First, they collected absorbance spectra of various components of beer. Then came the statistics. Using the Kruskal–Wallis test and backward stepwise linear discriminant analysis, they selected the characteristics that clearly distinguish one beer from another, such as levels of aluminum, iron, phosphate, or strontium.

Next, they created a mathematical model based on levels of iron, potassium, phosphorous, phosphates, and polyphenols. Jurado noted in a statement that the differences that help distinguish the beers may be quite subtle. Finally, the support vector machines went to work. They applied a set of algorithms for recognizing relevant data patterns.

The Seville team reported in the journal, Food Control, that they used their model to identified German, Spanish, and Portuguese beers with 99.3% accuracy. They note that the models will necessarily become more complex as more beers are added to the list. In time, models may be subgrouped.

"Differentiating should be dealt with by taking large geographical areas into account and then considering possible groupings in smaller areas," Jurado explained in a statement.

Sources:

"Where does my beer come from?," Spanish Foundation for Science and Technology press release, 12/1/11.

"Recognition of the geographical origin of beer based on support vector machines applied to chemical descriptors," Food Control, online Aug 2, 2011; in print January 2012.

Image courtesy of Maya83 used under its Creative Commons license.

Employee Profile: Alan Sentman, Ph.D.

PSI's Applied Chemistry and Spectroscopy Laboratory Manager

Interview by Rachel Petkewich, News Editor
Polymer Solutions Newsblog

Dog food bags. Starch. Ammunition. Alan Sentman joined PSI six years ago, and still enjoys the fact that he never knows what he will get to analyze next.

He started out as a project manager at PSI. As the Applied Chemistry and Spectroscopy Laboratory Manager, he now runs his own lab. He supervises three technicians as well as oversees standard methods, adapts methods to meet client needs, develops new methods, validates data, and maintains quality control in the lab. As an Expert, he is available to testify about results pertinent to court cases. He is also PSI's acting safety manager and known at PSI for attaching Jeopardy!-style questions to his daily schedules for fun.

Ask Alan what kind of analysis he is really good at, and he'll say, dilute viscosity testing. For example, he recently was asked to examine a starch solution. Over the course of a week, he and a technician worked on several small experiments to develop the appropriate parameters for the final test. He also likes solving problems with nuclear magnetic resonance spectroscopy (NMR) and is just itching to do more work with PSI's inductively-coupled plasma optical emission spectrometer (ICP-OES).

Alan grew up in Southern California. He completed a BS in chemistry at the University of California, Riverside, and earned a Ph.D. in materials chemistry from the University of California, Berkeley. He completed a postdoc at IBM's Almaden Research Center before starting at PSI.

Clearly, Alan's scientific curiosity and analytical nature continue beyond the lab. For example, at one time, Alan ate a lot of Skittles candy. He happened to notice that sometime the colored candy shell of Skittles candy didn't match the flavor inside, and wondered how often it really happened. So he sat down with a giant bag of Skittles, a pill cutter to reveal their inner color, and an Excel spreadsheet to record the data. With a sample size of about 326, he found that about 5% had interiors that didn't match the exterior.

Alan's wife, two Italian greyhounds, and one Chihuahua have observed him conducting other science-themed projects at home, including building a Jacob's ladder, constructing a compressed air rocket launcher, and fashioning a pulsejet out of a Mason jar. Alan also partakes in other hobbies, including origami, Asian cooking, and, most recently, blacksmithing.

Photo courtesy of Polymer Solutions Incorporated.

Upcoming Events:

Plastics Today Webinar

Topic: Assessing Biodegradable and Biodurable Polymers for Implantable Medical Devices

Presenters: Dr. Alan Sentman and Dr. Beth Caba

When: Thursday, January 19, 2012, 2:00 pm Eastern Time

Cost: Free of charge!

Where: Register using the following link:
http://bit.ly/Aq1MNS

Highlights from the Polymer Solutions Newsblog

The PSI Newsblog covers breaking news in the fields of plastics analysis, plastics testing, and plastics failure. Here are a few of the month's top articles:

Company News and Notes

New Equipment:

PSI has installed a new distillation system that enables the recovery of HFIP waste. This new addition will drastically reduce PSI's hazardous chemical waste disposal. Moving forward, PSI will grow their distillation capabilities to enable the recovery of solvents like chloroform, toluene, and DMA to further reduce their environmental impact.

Employee Accomplishments:

Josh Rancourt has successfully completed two FEMA Emergency Management courses:

=> Introduction to Incident Command System

=> Incident Command System for Single Resources and Initial Action Incidents

Josh's training enables him to serve our community during emergency situations, and also provides an invaluable resource to PSI in being prepared to respond to emergency situations on site. Moving forward, Josh will continue to complete training in Incident Command and Emergency Management.

Thank you for reading Polymer Solutions News! Please feel free to forward this newsletter to others who might be interested and subscribe below.

Subscribe to our Newsletter for industry updates:

Polymer Solutions News is a monthly publication of Polymer Solutions Incorporated, an independent laboratory and a strategic global resource for chemical analysis, physical testing, research and development services, and litigation services. Please contact us with any corrections, comments, reprint requests, suggestions for stories, requests for quotes, or other feedback. Thank You!