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Volume 8 / Issue 3

We are pleased to share with you another case study from our archives.

A retail store was experiencing a problem with breakage of small capacity, rectangularly shaped nail polish bottles.  The bottles were breaking while being displayed on a store shelf when the ambient temperatures were somewhat higher than usual.  Analysis of the fracture patterns indicated the bottles failed from an internal pressure load. 

In order to properly diagnose the cause of the breakage problem it was necessary to determine how the unexpected internal pressure load had been created and whether the tensile stresses that were associated with this load were too high or whether the glass strength was too low.  What were our findings?

The fracture origins were consistently located in the mid-point of the upper sidewall of the bottles as shown in the picture above.  Based on the physical dimensions of the mirrors that were present on the fracture surfaces, the average breaking stress was 5780 psi (405 kgf/cm2).  Since glass strength is defined as the magnitude of the tensile stress at failure, this stress value represents the glass surface strength at the fracture origin site.  Consulting a standard strength table, it was concluded that the glass strength was acceptable for a long-time load duration.  Therefore, it was necessary to focus on the factors that led to the creation of an elevated level of tensile stress. 

Upon heating of a capped container, if the headspace volume is inadequate, expansion of the liquid will totally consume this volume and the liquid will exert a hydraulic force on the inside surface of the container.  As the pressure increases, the flat panels of the container bend outward creating a high tensile stress on the outside glass surface in the sidewall region of the containers.  This would account for the presence of elevated tensile stresses and for fracture origins to be consistently located in the mid-point of the upper sidewall region. 

Two factors have the potential to create a hydraulic internal pressure load.  The first is insufficient overflow capacity of the containers and the second is excessive volume of the filled liquid product.  The overflow capacity of representative unbroken containers ranged from 20.2 ml to 20.9 ml which met the blueprint specification of 20 ml ± 1.5 ml.  The measured liquid volume ranged from 17.8 ml to 18.3 ml which exceeded the targeted volume of 16.0 ml to 17.5 ml. 

Thus, the cause of the hydraulic pressure was an excessive liquid volume when the containers were filled.  The total overflow volume of the cosmetic container must be designed to account for the product volume, the headspace volume, any mixing balls that might be present as well as the volume of the polish applicator.  Failure to account for all of these “product” volumes will potentially result in hydraulic pressure situations as it did in this case study.   

In-person Pharmaceutical training returns to Butler Campus in August

We are pleased to announce we will be conducting our “Testing and Fracture Diagnosis of Pharmaceutical Glassware” in-person 3-day training seminar August 17-19 on our Butler, PA campus. This course helps participants develop an understanding of the characteristics of glass as a packaging material and will introduce techniques for the evaluation of flaw severity as well as how to distinguish between functional and cosmetic defects.

Learn more or register HERE.

Announcing our latest live webinar “Coatings for Containers: Purpose and Performance”. 

This new, live webinar in our “Spotlight On” series, consists of 2 sessions of instruction and will provide an in-depth exploration of the  purpose of surface treatments that are applied to glass containers.  It will demonstrate the protection provided and indicate how the coatings ensure satisfactory container performance.
Topics covered include the general aspects related to the application and function of the hot end and cold end coatings. An introduction to the instruments and test methods used to evaluate the quality of surface treatments will also be presented. Participants will also become familiar with the practical aspects of interpreting coating measurements through the use of case studies.
The two live 1+ hour sessions will be conducted by AGR Research Scientist Doug Holscher who holds a BS in Chemistry from Shippensburg University.

For those unable to view the live broadcast, the webinar will be recorded and attendees can replay the presentation at their convenience. 

The first of the two live sessions will be conducted on Tuesday September 21 and the second on Thursday September 23 at 9:00 EDT/13:00 GMT/15:00 CEST.  The cost is $375 per person. Group discounts are available.

Registration will be available soon. CONTACT US If you have any questions. 
Our on-demand, E-seminars allow you to learn at your convenience. For a limited time, we are pleased to provide bundles created from our full catalogue of virtual training courses.

Choose from a specific pair of topics or register for everything in our catalog. We have created bundles that will fulfill any training need. The three levels of bundles will only be available for purchase during the months of July and August. Buy during the promotion and you will enjoy special discount pricing. The best part is you don’t have to watch in those months, you can view the training on your schedule later!

Signing up for any of our Bundles automatically qualifies you to join any of our live, interactive Q&A Sessions (via MS Teams). And as a special short-term summer offer you also gain access to our "Do's and Don'ts of weighting" webinar for free (a $95 value) with any of the combination packages.

Learn more or register HERE:

AGR Training Seminars Update 

We are pleased to announce our upcoming  Q3 in-person training Schedule: 

"Testing and Fracture Diagnosis of Pharmaceutical Glassware" in Butler, PA, Aug. 17-19

"Fracture 1: Testing and Breakage Diagnosis" in Lake Ammersee/Munich, Germany Sep. 13-15 and in Butler, PA Sep. 28-Oct. 1

"Batch and Furnace Operations" in Butler, PA Sep. 21-24

We also have our upcoming live webinar "Coatings for Containers: Purpose and Performance" coming in September. More information will be availalbe soon. Plus our "Stone Analysis Essentials" webinar has been converted to an on-demand, 7-module E-seminar that you can view at your convenience.  Learn more or register HERE. 

Private customized on-location training is available as well.

To learn more about all of our seminars, visit our Seminar Catalogue and if you have questions or would like to discuss Private Training Contact Us 
American Glass Research
603 Evans City Road, Butler, PA 16001
Tel: +1 (724) 482-2163
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American Glass Research · 603 Evans City Road · Butler, PA 16001 · USA

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