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Left: individual linear polymer chains Right: Polymer chains which have been cross linked to give a rigid 3D thermoset polymer. In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (). [1]
Conventional PU foams are cross-linked materials or thermosets. PU foams can either be mechanically recycled (where PU foams are grinded and used as fillers), or chemically recycled (where PU foams are downcycled into polyols or other monomeric components via chemical degradation). [16] [17] However, most PU foams end up on landfills.
The research group led by Ludwik Leibler demonstrated the operating principle of vitrimers at the example of epoxy thermosets. Epoxy thermosets can be represented as vitrimers, when transesterification reactions can be introduced and controlled. In the studied system, carboxylic acids or carboxylic acid anhydrides must be used as hardeners. [13]
They were first used after World War II, and continuing research has led to an increased range of thermoset resins, polymers or plastics, [2] as well as engineering grade thermoplastics. [3] They were all developed for use in the manufacture of polymer composites with enhanced and longer-term service capabilities.
Covalent functionalization can be used to directly attach the polymer to the carbon nanotube, or to add an initiator molecule which can then be used for further reactions. The synthesis of carbon nanotube reinforced PMCs is dependent on the choice of matrix and functionalization of the carbon nanotubes. [13]
Thermosets includes phenolic resins, polyesters and epoxy resins, all of which are used widely in composite materials when reinforced with stiff fibers such as fiberglass and aramids. Since crosslinking stabilises the thermoset polymer matrix of these materials, they have physical properties more similar to traditional engineering materials ...
The quality of thermosets (crosslinked polymers) is determined by a numerous factors such as the purity of the used monomer, polymerization time and temperature, stoichiometry of comonomers (when used) or type and quantity of catalyst or initiator. Another rarely minded factor is the volume shrinking (and density increase) during polymerization ...
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.