Isothermal DSC on PHB

Hi, I'm doing a PhD in the properties of PHB, and having great difficulty in getting anything like reproducible isothermal traces from the DSC. Have tried using a cooler unit, but the degradation of the PHB and condensation resulted in in shorting out the block.

If anyone has any ideas they would be much appreciated, with only 9 months left getting a bit concerned about lack of results!!

Thanks,

Linda

Reply to
LindaH
Loading thread data ...

Now why would you be interested in a DSC on your Pointy Haired Boss?! (Sorry about this comment. In the states there is a very popular comic strip called "Dilbert", about a tech worker who is tormented by his PHB, an icon for all the incompetent managers in the world.

formatting link

But seriously, I'm not clear on what you are trying to do and what the exact problem is. The best I can tell is that you are heating the samples up (too hot if you are getting degradation) and then cooling them down to your desired temperture in order to...determine the crystallization rate at a fixed temperature? Is this correct?

Assuming that this is correct: From all of your problems, it almost seems as if you have an old unit that is in dire need of service or total replacement. I say this because the temperature measurement seems shot (it over heating the sample to the point of degradation) and you aren't running dry air in the oven (as seen by the condensation).

Can you check that the temperatures are accurate? (Heat a range of high purity samples with a well defined melting points). Can you run dry air or another dry gas in the oven (dry nitrogen could prevent degradation in the event of overheating) or maybe put the entire unit in a box with a drying agent?

If my assumptions are incorrect, please clarify them and I'll be glad to take another shot at your problems.

John Aspen Research, -

formatting link
"Turning Questions into Answers"

Opinions expressed herein are my own and may not represent those of my employer.

Reply to
john.spevacek

IIRC PHB is very susceptible to thermal oxidative degradation. Can you run dry nitrogen through your DSC?

You might want to check Bob Williams' PhD at University of Birmingham in the UK (he was in the same polymer research group as me).

formatting link
Sorry about the long link. One of these days I'll work out how to use tinyurl or something similar.

Regards

Colin

Reply to
Colin Reed

formatting link

formatting link
That's a bit shorter!

Reply to
Colin Reed

formatting link
>

Just realised that these links don't actually work. Easier just to post the details. Contact University of Birmingham library services for availability.

formatting link
Author Williams, Robert John

Title A study of the thermal, oxidative and hydolytic degradation of a bacterial polyester / by Robert John Williams

Publisher Birmingham : University of Birmingham, 1994

Year 1994

Control Number q5958558

Notes Thesis (Ph.D.)-University of Birmingham, School of Chemistry, 1995.

Location Shelfmark Loan Type Availability Copies Loans Main Library Thesis Store DISS.S2.B95 Reference Available 1 0

Reply to
Colin Reed

Have you considered stabilizing the PHB ? Are you speaking of a butyrate resin?

J.W

Reply to
magicjoe

Have you considered stabilizing the PHB ? Are you speaking of a butyrate resin?

J.W

Reply to
magicjoe

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.