Furan-Based Polyesters

Whereas 2,5-dihydroxymethylfuran (DHMF) has been proposed frequently as a diol component for polyester synthesis, the high reactivity of the hydroxymethyl groups under acidic conditions primarily leads to resin formation, which is commercially exploited for the production of thermoset furan resins [55]. Although HMFA is more chemically stable than DHMF, it is also prone to resinification at high temperatures. In contrast, FDCA and derivatives have proven to be chemically stable under conditions relevant to polyester synthesis, making them the most versatile and industrially viable furan monomers for step growth polymers. 

Furan derivatives, mainly based on furfural or furfuryl alcohol, have been applied in thermosetting resins for almost a century. In contrast, academic and industrial research into furan based polyesters and polyamides took off in the 1950s. Farly papers (up until the 1970s) are usually rather qualitative, generally just describing the polymer synthesis, combined with rudimentary property analysis. Since the 1980s, more quantitative scientific papers have been 

In this chapter attention is focused mainly on 2,5-FDCA. However, also DHMF and HMFA based polyesters will be discussed briefly in order to gain a better overview of the full potential of furan based polyesters. 

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Moore reacted the acid chloride of FDCA with DHMF, yielding only low molecular weight polyesters [57], Recently, Gomes et al. described a fully furan based polyester via the acid chloride of FDCA by interfacial polymerization, with an Mn of 3800 g.mol , and a Tg of 83 °C (no Tn, is mentioned) [17], The onset of decomposition was determined to be around 205 °C. Based on these results we can conclude that DHMF is too unstable to be used as monomer in step-growth polymers. 

Grosshardt et al. prepared a series of furan based polyesters, by reacting FDCA dimethyl ester with 1,3-propanediol, 1,6-hexanediol, 1,12-dodecanediol and 1,18-octadecanediol, using calcium acetate and antimony(III) oxide as catalysts [47]. Molecular weights and thermal properties were determined for all polyesters and are summarized in Table 9.6. 

Two recent additions to the topic of furan-based polyesters include macromolecular structures synthesized from... 

A number of cement materials are used with brick. Standard are phenolic and furan resins, polyesters, sulfur, silicate, and epoxy-based materials. Carbon-filled polyesters and furanes are good against nonoxidizing acids, salts, and solvents. Silica-filled resins should not be used against hydrofluoric or fluosihcic acids. Sulfur-based cements are limited to 93°C (200°F), while resins can be used to about 180°C (350°F). The sodium silicate-based cements are good against acids to 400°C (750°F). 

Laminates have been prepared for the manufacture of chemical plant. They have better heat and chemical resistance than the polyester- epoxide- phenolic- or aminoplastic-based laminates but because of the low viscosity of the resins were not easy to handle. Because they were also somewhat brittle, furan-based laminates have been limited in their applications. 

Furan-2,5-Dicarboxylic Acid (FDCA) Based Polyesters... 

As with furan polyesters, following a number of isolated and rather qualitative studies, a real scientific interest in furan-based polyamides began in the 1980s with a thorough study carried out in Moore s laboratory [43] which called upon the use of 2,5-furan dicarboxylic monomers in conjunction with aliphatic diamines. These new nylons were however not inspected in terms of molecular weight, crystallinity or physical properties. 

Furan-2,5-dicarboxylic add also has tremendous industrial potential, because it could replace oil-derived diadds such as adipic or terephthalic acid as monomers for polyesters and polyamides [98, 99]. This diadd can be synthesized by Pt-catalyzed oxidation with 02 of 5-hydroxymethylfurfural the latter is obtained by acid-catalyzed dehydration of D-frudose or frudosans (inulin) the latter, however, are too expensive as starting materials, and yields from glucose-based waste raw materials are no higher than 40%. Therefore, the potential attractive option of furan-2,5-dicarboxylic acid will develop only after an effident generation of 5-hydroxymethylfurfural from forestry waste materials has been developed. The same compound is also the starting material for the synthesis of other interesting chemicals obtained by oxidative processes, such as 5-hydroxymethylfuroic add, 5-formylfuran-2-carboxylic add and the 1,6-dialdehyde. 

Different foundry casting techniques are used. Included are plastic-based binders mixed with sand. Various types of molds and cores are produced that include no-bake or cold-box, hot-box, shell, and oven-cured. Usual binders are phenolic, furan, and thermoset polyester. There is the foundry shell casting, also called dry-mix casting. It is a type of process used in the foundry industry, in which a mixture of sand and plastic (phenolic, thermoset polyester, etc.) is placed on to a preheated metal pattern (producing half a mold) causing the plastic to flow and build a thin shell over the pattern. Liquid plastic pre-coated sand is also used. After a short cure time at high temperature, the mold is stripped from its pattern and combined with a similar half produced by the same technique. Finished mold is then ready to receive the molten metal. Blowing a liquid plastic/sand mix in a core-box also produces shell molds. 

Polymer concretes based on phenol-formaldehyde, acetone-formaldehyde resins and monomers, and methyl methacrylate are much less common. Phenolic resins are similar to furan in many physical and mechanical properties. However, they are unstable in alkalis like polyester resins [7],... 

There are basically three types of mortars in use in CRM. They are thermoset resin based mortars (such as furan, phenolic, epoxy, polyester), silicate mortars, and sulfur mortars. 

Orthophthalic, isophthalic, bisphenol, and chlorinated or brominated polyesters exhibit poor resistance to such solvents as acetone, carbon disulfide, toluene, trichloroethylene, trichloroethane, and methyl ethyl ketone. The vinyl esters show improved solvent resistance. Heat-cured epoxies exhibit better solvent resistance. However, the furan resins offer the best all-around solvent resistance. They excel in this area. Furan resins are capable of handling solvents in combination with acids and bases. 

Another class of interesting isohexide polyesters contains furan-2,5-dicarboxylic acid (2,5-FDA or FDCA, Figure 9.5) as the aromatic diacid component. Since FDCA can be obtained from carbohydrates via various routes, this opens up possibilities for fully bio-based semiaromatic polyesters. 

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