structures——test methods
DMA
FTIR
Micro phase Separation
DSC
AFM
What can AFM do ?
AFM
INSTRUMENT: Atomic Force Microscope PRINCIPLE: a cantilever with a sharp tip is
200nm. Same height
200nm. Same force
Valley Soft segment
Peak Hard segment
500nm. 3D picture of PU
The AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface. The cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever according to Hooke's law.[2] Depending on the situation, forces that are measured in AFM include mechanical contact force, van der Waals forces, capillary forces, chemical bonding, electrostatic forces, magnetic forces (see magnetic force microscope, MFM), Casimir forces, solvation forces
• • • • • • • • • • • • • • •
Segmented polyurethanes (PUs) have a great application potential due to their wide range of mechanical properties. Depending on the specific end use, PUs can be designed to possess either elastic or rigid mechanical characteristics, depending on the macromolecular structure. Thus, considerable effort has been made to understand structure– property relationships of segmented PUs. In order to tailor mechanical properties, the macromolecules of segmented PUs are built up of two types of blocks. One block type, the so-called hard segment, is glassy (or crystalline) as it is below itsTg (orTm) at the use temperature. The other soft block is flexible and rubbery, as it is above its correspondingTgat the use temperature. The hard segments due to their thermodynamic incompatibility with the soft segments usually associate to form small domains that serve as physical cross-links and reinforcement sites; hence they limit flow of the other phase,
THE APPLICATION OF AFM ON THE
MICROPHASE SEPARATION OF POLYURETHANE
Pengfei Li 25th Apr,2014
CONTENT
Introduction of PU Principle of AFM
Application of AFM
AFM
Contact mode
• The tip drag across the surface
Tapping mode
• keeping the probe tip close enough to the sample • preventing the tip from sticking to the surface • Increase amplitude
used to scan the specimen surface,and When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever according to Hook’law.So,forces that are measured and chang into the height of the sample surface.
POLYURETHANE
What is polyurethane?
O O C N N C O
+
HO
OH
HN
C
O
MDI
HDI
PEG
HO(CH2CH2O)nH
PPG IPDI
PTHF
பைடு நூலகம்
POLYURETHANE
Different Structures(Thermodynamic incompatible) — —Phase separation
Noncontact mode
• cantilever does not contact the sample surface
What Can We Get From The AFM?
TEM
AFM
TPU
TPU with 0.05wt%ZnO
Which one has lager degree of phase separation?