Rheometry: Examples From Industry -Steve Brenno- RTP Company 9 March 2012. Lecture Outline. • General/Material Background Torque Rheometer (Process Development) Capillary Rheometer (Effect of Additive) Dynamic Rheometer (Material Design). RTP?.
9 March 2012
ThermoPlastic Elastomer (TPE)?
“…Having the property of softening or fusing when heated and of hardening again when cooled…”
“…Any of various elastic substances resembling rubber…”
Int. Institute of Synthetic Rubber Producers (IISRP) definition:
“Polymers, polymer blends or compounds which, above their melt temperatures, exhibit thermoplastic character that enables them to be shaped into fabricated articles and which, within their design temperature range, possess elastomeric behavior without cross-linking during fabrication. This process is reversible and the product can be reprocessed and remoulded.”
TPEs are composed of hard and soft domains. They are dualphase materials at the nano- or micro-scale in their solid state.
- Hard phase contributes “plastic” properties such as:
- Soft phase contributes “elastomeric” properties such as:
compression & tension set
But Why Are TPEs “Rubbery”?
At usage temperature, the TPE’s elastomeric/softphase is above its glass transition temperature region (Tg).
By raising the temperature of the TPE above the glass transition or melting temperature (Tm) of the plastic/hardphase.
+ ShearSo How Can TPEs Be Melt Processible?
…and applying shear forces typical of thermoplastic processes.
*** For comparison, thermoset rubbers (TSRs) are singlephase materials with non-reversible chemical (covalent) bond cross-links***
Tri-block copolymers develop a “nanocomposite-like” material
Multi-block copolymers with polymer crystallinity creating the hard phase and physical x-link.
…Processdependent, two-phase morphology on the micro-scale
Mean shear stress = C2 * Torque
(Example: Journal of Rheology43, 415 (1999))