Guest Put Up By Jeremy Pasatta, Advanced Polymer Coatings
One of the principle drivers of recent product improvement for thermosets, and epoxies particularly, is sturdiness, and epoxie hardeners are not any exception. Today, there are a number of bio-based hardeners for epoxy resins, and maybe probably the most well-known and broadly used are the phenalkamine household of amine-based epoxy hardeners. Phenalkamine hardeners are based mostly on cashew nut shell liquid, from which cardanol is extracted. Cardanol is then reacted with numerous amines to offer a phenalkamine, which is a kind of Mannich base, with the response scheme and construction as proven in Figure 1.
Figure 1. Phenalkamine response scheme and construction
(Source: https://www.cardolite.com/expertise/phenalkamines/)
Due to their distinctive construction amongst amine hardeners, phenalkamines present the next advantages:
- Very quick curing because of phenolic construction
- Excellent low temperature curing
- Good flexibility and water resistance because of aliphatic facet chain
- Don’t blush
- Long pot life
- Chemical resistance
The improved water resistance of formulations utilizing phenalkamines additionally improves the corrosion resistance of metal substrates in coatings utilizing phenalkamine hardeners. The long-chain alkyl teams that enhance water resistance additionally enhance adhesion on poorly ready and moist substrates, comparable to damp concrete.
The earlier weblog put up mentioned polyamides, that are amine hardeners based mostly on dimer acid and tall oil fatty acid, that are additionally bio-derived uncooked supplies. Hardeners have been developed which can be a mix of phenalkamine and polyamide and that mix many of the optimistic properties of every hardener with a really excessive biobased mass share. These hardeners, often called phenalkamides, are synthesized utilizing a polyamide because the beginning amine within the artificial scheme proven in Figure 1. A visible illustration of the properties of those hardeners is proven in Figure 2.
Figure 2. Properties of Phenalkamides
Source: (https://www.cardolite.com/expertise/phenalkamides/)
In addition to the commercially obtainable phenalkamines and phenalkamides, a number of different research have been carried out on biobased uncooked supplies used as curing brokers for epoxy resins and these research are summarized in Table 1.
Table 1. Summary of Biobased Epoxy Curing Agents
(Source: https://doi.org/10.1002/app.44103 )
Of the biologically derived hardeners listed in Table 1, the constructions based mostly on furanyl constructing blocks have many potential for property refinement. Some of the attainable constructions are proven in determine 3.
Figure 3. Structures of furanyl-based hardeners
(Source: https://doi.org/10.1002/app.44103 )
When DFDA and CH3-DFDA have been cured with a regular bis-A based mostly epoxy resin, TGs of 128°C and 142°C, respectively, have been measured utilizing DMA. This exhibits that there is no such thing as a have to compromise on efficiency with a biobased hardener and that programs with excessive thermal resistance will be realized.
This weblog put up exhibits that an ever-increasing variety of organic hardeners are being developed that present distinctive properties. The improvement and commercialization of those hardeners will proceed to develop because the drive for sustainability will increase in a number of markets utilizing epoxy resins. When used at the side of bio-derived epoxies, a formulator can create a product that makes an actual distinction to shoppers and the atmosphere.
Source: polymerinnovationblog.com