To make glass stronger, you have to break it

To most people, the reason that glass cracks is simple: Impact. A rock strikes the windshield of a car or a smartphone drops to the ground.

To researchers at SCHOTT, the reasons behind glass cracks are much more complex.

By studying cracks, SCHOTT researchers can uncover improvements in glass materials used in electronics, medicine, and even energy storage. This has led to strengthened glass, the creation of bendable glass, and more.

This research is perhaps most important in the pharmaceutical industry, where cracks can be costly and dangerous. Here’s what we’re learning about how glass cracks and how that knowledge will usher in the next generation of innovations.

Where cracks start

The strength of glass is not constant. A piece of glass may survive one fall, but shatter on the next, even though the same, or less, force was applied.

All intrinsic glass cracks start out as slight imperfections invisible to the naked eye. These imperceptible defects are usually caused by production or handling. As mechanical stresses increase – through drops, increases in pressure, or bending – these slight imperfections become larger until sudden fractures occur. Extrinsic glass cracks commonly originate from impacts by hard materials – metals, ceramics, or other glass containers.

Inside SCHOTT laboratories, scientists use a variety of analytical tools. Researchers might peer deep into the nano- and micro structures of glass. Or they may use simpler tests, like dropping a steel ball on glass.

These tests yield insights that SCHOTT uses to forecast product lifetimes, identify new applications, or support better processes and products.

Improving pharmaceutical packaging

Broken vial after burst pressure test

Broken vial after burst pressure test

While actual intrinsic glass breakage in the pharmaceutical industry is pretty rare, the stakes are high. Breakage can cost significant amounts of money in terms of lost product. But because glass breakage can also impact patient safety, it’s a clear cause for concern among pharmaceutical companies and regulatory agencies. Glass breakage occurring in the field requires companies to perform analyses that identify the root cause and to develop plans to prevent such instances in the future.

Many pharmaceutical companies, rather than perform glass strength tests, use cosmetic quality as an indicator of glass strength. The reasoning is that if intrinsic cracks start out as slight imperfections, visual inspection can decrease the likelihood of breakage in the field. In the past the volume of glass tubing produced for use as syringes, vials, and cartridges has traditionally been too large for anything but statistical sampling for quality control, however new advances in inspection technology now allow for 100 percent inspection of the glass tubing.

Visual inspection, however, does not always ensure undamaged glass.

Stress distribution in vial that not was completely relieved after hot-forming

Stress distribution in vial that not was completely relieved after hot-forming

SCHOTT continues to employ tests on the strength of glass on behalf of clients. In some cases, SCHOTT performs forensic analysis to determine if fractures and stress occurred during shipping, processing, or during filling.

Pharmaceutical companies have also tapped SCHOTT experts to determine whether slight scuff marks on pharmaceutical vials have weakened the glass, and whether high tech drugs are interacting with leachables from the container closure system.

Battling breakage

Research into glass cracks starts at the nano-structure, but it can involve processes as ordinary as how a box or pallet was handled during shipment. By reviewing everything from the smallest air bubbles to the box that a syringe is shipped in, huge strides have been made in improving the surface quality of glass and the way it is handled. Put another way: Stronger glass makes for safer patients.

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Hi there. I’m Dan Haines, Scientific Advisor at SCHOTT Pharma Services. I joined SCHOTT 13 years ago as a Research Scientist, helping to develop SCHOTT Nexterion microarray products, and pharmaceutical coating development. In my current role, I serve as the North American Free Trade Agreement (NAFTA) coordinator for pharmaceutical packaging analytical services. I earned my bachelor’s degree from The University of Scranton and hold a doctorate in inorganic chemistry from The University of Chicago. I’m an avid skier, game player, and love spending time with my wife and three children.

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