PAN is a polymer with the formula (C₃H₃N)_n that has unique properties.

Homopolymeric Polyacrylonitrile (PAN)

Almost all PAN produced for commercial applications are copolymers obtained from mixing acrylonitrile with other monomers, mainly vinyl esters (vinyl acetate, methyl acrylate and methyl methacrylate) in textile applications. In carbon fiber applications, mainly acrylamide, vinylpyrrolidone and itaconic acid are used. In anti-flame modacrylic fibers, vinyl chloride and vinylidene chloride are used. Styrene is used in SAN thermoplastic resin and in ABS.



Among the characteristics to be highlighted in the PAN:

• It is the most resistant polymer among all to degradation by sunlight, mainly by ultraviolet rays.
• Has the ability to form oriented fibers.
• It is quite inert and resistant to most organic solvents and acids, being only attacked by highly polar liquids and concentrated solutions of bases.
• Its fibers are resistant to breakage, produce high volume, are soft, comfortable, and thermal insulating, having properties similar to natural wool.
• In the form of fibers, when heated, it does not melt and maintains its morphological structure, a property that is used for the production of carbon fiber, insulating fibers, anti-flame fibers and blankets for the filtration of hot gases.

Chemical formula
IUPAC Name	Polyacrylonitrile
CAS Number	25014-41-9
Structure
Centesimal composition	C 67,91%, H 5,7%, N 26,4%
Appearance	White Solid
Density	1,184 g/cm³
Fusion point	Above 300ºC
Boiling point	Degrades
Glass transition temperature	Approx. 95ºC
Solubility in water	Insoluble
Main Solvents	Dimethylformamide, Dimethylacetamide, EthyleneCarbonate, PropyleneCarbonate, SodiumThiocyanate, ZincChloride, NitricAcid

Thermal Properties of PAN

PAN does not melt under normal conditions and degrades before melting. Only by DSC calorimetry can the peak of its melting be observed, above 300ºC, if the heating rate is 30 ºC per minute or more. Heated above 180ºC it turns into a rigid structure with energy release, a phenomenon known as cyclization. The higher the temperature, the faster the release of energy is, which can cause the polymer to burn.
If the heating is slow and the heat released is removed, the PAN fibers can maintain the fibrillar structure and when heated above 1000ºC, they are transformed into carbon fibers with a content greater than 90% of this element. This property makes PAN the best polymer to be used in the production of carbon fiber.

PAN cyclization reaction

Its color is white, but depending on the temperature, it may acquire a yellowish color that tends to black, due to the cyclization and formation of conjugated bonds in the polymer chain.

Heating of PAN-co-PS fibers in isothermal conditions at 190ºC in air

During heating, the PAN structure undergoes several changes, since its oxidation, if heated in the air, and also undergoing mass loss due to the release of different types of gases. Some authors describe the thermal decomposition of PAN with the following stages:

Stage	Gases Released	Temperature Range (ºC)
I	Small release of H2O	Until 250ºC
II	Release of H2O, NH3, and little HCN and CO2	300ºC to 450ºC
III	There is an increase in the release of CO2 and HCN, along with H2O and NH3 and hydrocarbons	450ºC to 600ºC
IV	H2 starts to be released due to cracking of hydrocarbons along with HCN and CO. Decreased release of NH3, H2O and CO2 that are converted to C, H2, N2, HCN and CO	600ºC to 900ºC

PAN thermal degradation model proposed in the article
“Processing and Application of Ceramics” 4 [2] (2010) 59–62

PAN Infrared Spectrum

Infrared Spectrum - PAN Homopolymer

Spectral Comparison of several polyacrylonitrile polymers

Pan Homopolymer
PAN-co-Methyl Polymethacrylate (PAN / MMA)
PAN-co-Methyl Polyacrylate (PAN / MA)
PAN-Polyvinyl Acetate (PAN / VA)