Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

© 2015 Society of Plastics Engineers. Compression of dehydrated P(MMA-co-NVP) hydrogel at the glass transition temperature (161°C) results in discs which exhibit orthotropic expansion when hydrated in water. It has been found that the expansion is nonuniform, with an outer annulus expanding more rapidly than the inner core. This behavior has been investigated by comparing the crosspolarized light microscopy, swelling response, and hardness tests for discs pressed with a lower friction (PTFE) interface and those pressed with a higher friction interface (aluminum). Only in the latter case was a clear boundary observed. The outer 4 mm of a 13 mm disc showed increased radial chain alignment as compared to the inner core, as well as a lower average hardness value (81.7HK compared to 97.7HK). These results were not observed in samples pressed with a PTFE interface. This behavior has subsequently been modeled using axisymmetric loading and assuming Von Mises Criteria, showing that the change in behavior can be explained by the presence of a stick-slip boundary formed during hot pressing.

Original publication

DOI

10.1002/pen.24067

Type

Journal article

Journal

Polymer Engineering and Science

Publication Date

01/01/2015

Volume

55

Pages

1290 - 1295