Monthly Archives: February 2014

Adhesion, Polymer, Composite, and Geckskin

Last night I attended the GGPF monthly polymer forum, in which professor Alfred J. Crosby gave a talk titled, “Draping Materials: Enabling Advanced Adhesives and Multifunctional Technologies”. He described his research areas and spoke extensively on the studies that led to
GeckskinTM. It is truly fascinating. My understanding on adhesion has always come from
surface science and chemistry. His talk adds mechanical and biological dimensions to my knowledge base. The equation he presented to describe adhesion force is directly proportional to contact area and inversely proportional to compliance. I have heard of compliance in mechanics classes and I have seen it presented in DMA thermographs. However, I have never paid much attention to it. It is certainly something new that I should keep an eye on.

Another surprise to me is he is using composite with carbon fibers and glass fibers and Kevlar fibers as the stiffness backbone.  It is certainly a very different application than the composite structures traditionally used in structural applications such as airplanes and bicycles.

It is great to see science works. And professor Crosby is certainly smart to collaborate with other departments and professors with different expertise. Consilience certainly works well here. Professor Crosby disclosed at the end of the talk that a company was formed last year to commercialize GeckskinTM. I can think of lots of applications for it and I wonder if 3M will be acquiring the company any time in the future!

Best practices in presenting Tg data

Due to the nature of glass transition, which may occur over a range of temperature 5 – 10 deg-C and which is a second-order transition, it can be difficult and confusing to identify.  In addition, because thermal analysis by nature is dynamic (i.e., temperature increase or decrease), it is necessary to accompany Tg data with experimental details, preferably the thermograph with sample preparation information and test parameters.  Without knowing the testing details, it is impossible to compare Tg.  Ideally, it is best to compare Tg when the samples are tested side-by-side with the same method.  This means the same sample preparation, same test procedures, and the same equipment.

Tg data should always be presented with the way it is measured and how it is identified.  If a standard method such as ASTM is followed, the method should be specified along with its required report information.  If it is not a standard method, sample preparation, test parameters and how the transition measurement is selected should be available, at the very least.  For example, DSC, heating rate 10C/min, mid point temperature.

For comparison between samples, the temperature value should be rounded and not contain any decimal points.