Polyester networks

Network Polyesters Synthesized with Polyatomic Acid and Polyatomic Alcohol.222... 

NETWORK POLYESTERS SYNTHESIZED WITH POLYATOMIC ACID AND POLYATOMIC ALCOHOL... 

Yang and coworkers did the most efforts on the development of network polyester based on citric acid. " They investigated the reaction of citric acid with a series of aliphatic diols (from 3-16 carbon chains) and polyether diols such as polyethylene oxide (PEG), in which 1,8-octanediol (POC) and 1,10 decanediol (PDC) have been studied the most. 

These polymers contain ester groups in the main chain of the polymer itself. The polymers are of various types like linear saturated, linear unsaturated, network polyesters, polyallylesters and Polycarbonates. 

The use of triols or tricarboxylic acids leads to cross-linked or network polyesters. For example, an alkyd resin is formed by the reaction of glycerol with phthalic anhydride [19]. 

More usually, phthalic anhydride is reacted with a polyfunctional material such as glycerol to form a network polyester (a glyptal). This class of polymer, modified with monofunctional additives and known as alkyd resins, is very important in the paint and plastics industry. Consequently most of the theoretical studies have been concerned with the formation of infinite networks ( microgel ) and the distinction between this and the so-called gel-point [75]. 

Poly(ethylene terephthalate) is a linear polyester obtained from the reaction of difunctional monomers. Branched or network polyesters are obtained if at least one of the reagents is tri- or multifunctional. This can be achieved either by the use of polyols such as glycerol in the case of saturated polyesters (glyptal) or by the use of unsaturated dicarboxyhc acids such as maleic anhydride in the ease of unsaturated polyester. In the preparation of glyptal, glycerol and phthalic anhydride reaet to form a viseous liquid initially, which on further reaction hardens as a result of network formation (Equation 2.31). 

Network polyester resins may be categorized into saturated and unsaturated polyesters. Unlike linear saturated polyesters such as PET, which are made from difunctional monomers, saturated polyesters (glyptal) are formed by the reaction of polyols such as glycerol with dibasic acids such as phthalic anhydride. 

Unsaturated network polyesters may be produced by using an unsaturated dibasic acid or glycol or both. Typically the unsaturated dibasic acid, such as maleic anhydride or fumaric acid, is copolymerized with a saturated acid such as phthalic acid and a glycol (e.g., propylene glycol or diethylene glycol). 

Describe network polyesters. Explain how they are prepared by two different techniques. 

A large number of polyesters is commercially available. These polymers are conveniently classified into the following types - linear unsaturated polyesters linear saturated polyesters of low molecular weight linear saturated polyesters of high molecular weight network polyesters poly(allyl ester)s and polycarbonates. Each of these groups is considered separately in this chapter. 

Intermolecular-intramolecular copolymerization MA-diallyl ether, 314, 325, 348 MA-dienes, 348, 358 MA-divinyl silanes, 327, 385 Interpenetrating polymer networks, polyester-polyurethane blends, 490 Iodine, 198... 

Mirci L, Boran S, Luca P, Boiangiu V (2003) New citric esters with aromatic content and a complex structure considered for use as tribological fluids. J Synth Lubr 20 39-52 Tsutsumi N, Oya M, Sakai W (2004) Biodegradable network polyesters from gluconolac-tone and citric acid. Macromolecules 37 5971-5976... 

---