Polymer characterization

Some of the most common methods for determining these parameters are colligative property measurements, static light scattering techniques, viscometry, and size exclusion chromatography.

Gel permeation chromatography is often used in combination with multi-angle light scattering (MALS), Low-angle laser light scattering (LALLS) and/or viscometry for an absolute determination (i.e., independent of the chromatographic separation details) of the molecular weight distribution as well as the branching ratio and degree of long chain branching of a polymer, provided a suitable solvent can be found.

A more efficient analysis of copolymer molecular mass and composition is possible using GPC combined with a triple-detection system comprising multi-angle light scattering, UV absorption and differential refractometry, if the copolymer is composed of two base polymers that provide different responses to UV and/or refractive index.

[4] Many of the analytical techniques used to determine the molecular structure of unknown organic compounds are also used in polymer characterization.

Polymer morphology on a mesoscale (nanometers to micrometers) is particularly important for the mechanical properties of many materials.

X-ray diffraction is generally not as powerful for this class of materials as they are either amorphous or poorly crystallized.

A true workhorse for polymer characterization is thermal analysis, particularly Differential scanning calorimetry.

Thermogravimetric analysis can also give an indication of polymer thermal stability and the effects of additives such as flame retardants.

The characterization of mechanical properties in polymers typically refers to a measure of the strength, elasticity, viscoelasticity, and anisotropy of a polymeric material.

Typically, polymeric materials are characterized as elastomers, plastics, or rigid polymers depending on their mechanical properties.

These defects are typically made up of a second, low modulus polymer that is dispersed throughout the primary phase.

The crazes can increase the strength and decrease the brittleness of a polymer by allowing the small cracks to absorb higher stress and strain without leading to fracture.

Dynamic mechanical analysis is a characterization technique used to measure storage modulus and glass transition temperature, confirm crosslinking, determine switching temperatures in shape-memory polymers, monitor cures in thermosets, and determine molecular weight.

The applied stress and the strain on the sample exhibit a phase difference, ẟ, which is measured over time.