Is epoxy a cross-linked polymer?
Crosslinking occurs when a thermosetting polymer such as an epoxy, cures via a chemical reaction either through the addition of heat, UV light exposure, or at room temperature itself. The origin of this crosslinking process occurs when linear polymer chains link to form a three dimensional network (See Figure 1)1.
What are cross linking agents in polymers?
Cross-linking agents are added to novolacs to create bridges among the novolac polymers, i.e., the process of curing. Among them, the most common is hexamethylenetetramine (in short known as HEXA), which decomposes and reacts with a considerable rate from 150 °C and formally provides six methylenes per molecule.
Which interaction allows for the cross linking of the polymer?
chemical bonding
Polymers can be cross-linked by chemical bonding or physical interaction. Synthetic methods for chemically cross-linked polymers are classified into cross-linking during polymerization and post- cross-linking of polymer chains.
How do you cross link a polymer?
Crosslinking can be accomplished chemically or by irradiation. Chemical crosslinking with rubber material is called Vulcanization. It is accomplished by a heat induced reaction between the polymers and a crosslinking agent.
Does epoxy conduct electricity?
Epoxy alone is non-conductive, but if combined with silver filled epoxy it can become conductive. The most common is silver, but gold, nickel, copper and carbon can also be used. Another benefit is the epoxy can also be thermally conductive, meaning it can also cool the component.
What does cross-linking agents do?
Crosslinking Agents. Crosslinking is the formation of chemical links between molecular chains to form a three-dimensional network of connected. molecules. The vulcanization of rubber using elemental sulfur is an example of crosslinking, converting raw rubber from a weak plastic to a highly resilient elastomer.
What is cross linking degree?
The degree of crosslinking, or DC, relates to the number of groups that interconnect two materials. The DC is generally expressed in mole percent.
How are crosslinkers and curing agents help polymers?
Crosslinkers / Curing Agents / Hardeners Crosslinking is a process of associating polymers through a chemical bond. In most of the cases it is irreversible and can be either intra or inter-molecular. Crosslinking boosts the thermal stability and mechanical properties of the polymer.
What kind of chemical is used to cross link epoxy?
Curing chemistries using phenol (ic) hardeners is for instance employed in powder coating applications whereas anhydride cure is often used in epoxy composite applications. At room temperature however by far the largest groups of chemicals used are amine-functional curing agents capable of cross linking epoxy resins at room temperature.
How does an epoxy cross link at room temperature?
At room temperature however by far the largest groups of chemicals used are amine-functional curing agents capable of cross linking epoxy resins at room temperature. An epoxy group reacts with ONE amine-hydrogen, i.e. one hydrogen attached directly to a Nitrogen atom (hence also amine-hydrogen equivalent weight).
Which is an example of a chemical cross linking agent?
Chemical cross-linking agents covalently couple neighboring collagen fibrils using targeted reactive moieties in the collagen fibrillar system and the cross-linking molecules themselves.138 Such agents include glutaraldehyde, epoxy compounds, and isocyanates.