ENME307 Polymer Analysis

Sample exclusion chromatography

dissolved polymers passed through polystyrene beads in a column, large passes through faster and small slower. Plot # molecules to time and calibrate to molecular weight

Solvent viscosity

viscosity of pure solvent with no polymer present

Solution viscosity

viscosity of polymer solution

Relative viscosity

dimensionless ratio comparing solution to solvent

Specific viscosity

fraction increases in viscosity caused by dissolving polymer

Reduced viscosity

extrapolated to zero concentration – hydrodynamic volume of single polymer molecule

Thermal analysis

analysis of change in a property of a sample which is related to an imposed temperature alteration

Molecular weight average order

M_w > M_v > M_n

Differential thermal analysis (DTA) temp sampled compared to reference in same thermos, deviations indicate phase transformation. Not accurate for enthalpy.

Differential scanning calorimetry (DSC)

sample and reference in aluminium pan in different furnaces with a heat coil/thermal coupler. Measures energy/power required for a zero temp difference

Blow mold DSC

smaller broader peaks

Twice melted DSC

2nd time, lower broader peaks due to memory effects from entanglements

Thermoset DSC

heat evolution while curing to check if full cure. Repeat the run, of no further crosslinking, no unreacted monomers so no exotherm

2 exotherms DSC

2 different reactions, 2 different Tg with distinct polymer make up regions

Time optimising DSC

look for exotherms while raising heat until exotherm no longer forms

Thermal mechanical analysis (TMA)

non oscillating static load applied to sample. 0 load test, thermal expansion, control test, differential deformation, softening test, deflection test

Non uniform expansion TMA

not fully cured, stress within material

Amount of crosslinking TMA

residual stress to coil back to original shape measured via diameter change

Polymer shrinkage

as Tg increases more crosslinking, more shrinkage

Creep recovery

constant load, measures strain, small static stress applied and remove, measure transient creep strain.

Residual strain

strain in creep recovery lags less each time

Thermogravimetric analysis (TGA)

polymer in gas atmosphere, heat and look for material stability. Burns off polymer and measure mass to determine crystallinity

Dynamic Mechanical Analysis (DMA)

measures phase lag between stress and strain. Elastic – in phase, Viscous – out of phase. Find Tg

Overlapping Tg

not chemically compatible

Thermoset (DMA)

curing behaviour, stiffness die to crosslinking (gel point)

Freq change (DMA)

more elastic and less viscous as frequency increases