Polyesters, unsaturated development

Unsaturated Polyesters. The chemistry of unsaturated polyesters was developed in the 1930s, and manufacture of glass-fiber-reinforced polyesters began in the early... 

Nylon, polyester (unsaturated) and, currently, aromatic Nylons (aramides) like Kevlar. High-performance (and expensive) reinforcing fillers include carbon (mainly graphite) fibers, alumina, silicon, carbide, nitrite, boron, beryllium and other metals. Producing extremely high strength and stiffness, these specific fibers have been developed for space, aviation and military use. 

A new class of materials called smart tagged composites has been developed for stmctural health monitoring appHcations. These composites consist of PZT-5A particles embedded into the matrix resin (unsaturated polyester) of the composite (16). 

Other polyamides produced experimentally include polymers with active lateral groups (hydroxy, keto groups etc.), polymers with heteroatoms (sulphur and oxygen) in the polyamide-forming intermediates, polymers with tertiary amino groups in the main chain and polymers with unsaturation in the main chain. There does not, however, appear to have been any serious attempt to develop unsaturated polyamide analogues to the polyester laminating resins. 

As small molecule fragments resulting from the initiator may plasticize the polymer and lower performance, approaches have been developed to avoid this. A dihydroxyamine can be used to form a polyester [52]. This accelerator gave a modest increase in the strength of unsaturated polyester resins. A polymerizable tertiary amine has been prepared by the reaction of A-methylaniline with glycidyl methacrylate [53] (Scheme 8). 

Processes have been developed separating pure metaxylene from other Cj aromatics.Metaxylene is a raw material for the manufacture of isophthalic acid. The major outlets for the acid are in the synthesis of unsaturated polyester and alkyd resins, and for the production of isophthalic esters (plasticizers). 

Methods for achieving low styrene emissions in the unsaturated polyester resin industry are discussed. The necessity for new formulations to maintain the same mechanical properties as the previous ones is considered. The environmental requirements and working conditions that make essential the development of new formulations and processes that reduce volatile emissions are examined. The need for factories to adopt alternative technologies in order to comply with the latest environmental restrictions is discussed. 12 refs. 

Polymers Catalytic reactions involving C=C bonds are widely used for the conversion of unsaturated fatty compounds to prepare useful monomers for polymer synthesis. Catalytic C-C coupling reactions of unsaturated fatty compounds have been reviewed by Biermann and Metzger [51]. Metathesis reactions involving unsaturated fatty compounds to prepare co-unsaturated fatty acid esters have been applied by Warwel et al. [52], Ethenolysis of methyl oleate catalyzed by ruthenium carbenes developed by Grubb yields 1-decene and methyl 9-decenoate (Scheme 3.6), which can be very useful to prepare monomers for polyolefins, polyesters, polyethers and polyamide such as Nylon 11. 

Development of the third class, i.e. unsaturated polyester resins, remained rather slow until the late 1930s, but after commercial production of maleic anhydride by catalytic oxidation of benzene began in 1933, maleic anhydride and fumaric acid rapidly became the most important sources of unsaturated groups in polyesters. The mechanism of drying of these resins on their own and with the addition of drying oils (i.e. unsaturated compounds such as linseed oil) was... 

Low-profile additives are generally materials such as poly (vinyl acetate), polystyrene, polyethylene or polycarbonate. During the unsaturated polyester cure cycle, the low-profile additives separate into a second phase, which expand to counteract the shrinkage of the curing unsaturated polyester resin. Material development and the science of low-profile additives have helped create substantial markets for unsaturated polyesters. Their use in automotive markets, where Class A show room quality surfaces is a requirement, is an example of this. 

There are perhaps hundreds of miscellaneous unsaturated polyester resin construction applications. These would include window frames, doors, cabinet enclosures, electrical boxes, etc. In addition, recent developments bode well for unsaturated polyesters in construction markets. Concrete rebar, bridge construction and general infrastructure repair are examples of growing construction applications. 

The growth of unsaturated polyesters will continue to be fueled by their versatility and their ability to provide cost-effective solutions to end-use requirements. Unsaturated polyester composites will continue to provide solutions to engineering demands for corrosion resistance, strength-to-weight and cost performance. Marine, transportation and construction opportunities currently identified and being developed will provide growth beyond the existing applications presented. Some examples are as follows ... 

In the early 1990s, at Newtown Square in Pennsylvania, Lyondell Chemical Company developed an interesting alternative to produce unsaturated polyesters. Based on this development, it became possible to produce a series of very flexible UPRs without sacrificing either mechanical or thermal properties. These products also showed good corrosion resistance when compared to conventional UPR resins. 

At the outset of the composites industry, the matrices were unsaturated polyesters. Then other thermosets were developed but some years ago the manufacture of thermoplastic composites began and their development is now faster than that of thermoset-based composites. 

The purpose of this review is to report on the recent developments in the macromolecular engineering of aliphatic polyesters. First, the possibilities offered by the living (co)polymerization of (di)lactones will be reviewed. The second part is devoted to the synthesis of block and graft copolymers, combining the living coordination ROP of (di)lactones with other living/controlled polymerization mechanisms of other cyclic and unsaturated comonomers. Finally, several examples of novel types of materials prepared by this macromolecular engineering will be presented. 

Results are presented of experiments undertaken by Gaiker in the manufacture of sandwich panels containing foam cores based on PETP recycled by a solid state polyaddition process developed by M G Ricerche. Panels were produced with glass fibre-reinforced unsaturated polyester and epoxy resin skins, and allthermoplastic panels with PE, PP, PS and glass fibre-reinforced PETP skins were also produced. EVA hot melt adhesives and thermoset adhesives were evaluated in bonding glass fibre-reinforced PETP skins to the foam cores. Data are presented for the mechanical properties of the structures studied. 

Table 10.3 summarizes the uses of propylene oxide. Propylene glycol is made by hydrolysis of propylene oxide. The student should develop the mechanism for this reaction, which is similar to the ethylene oxide to ethylene glycol conversion (Chapter 9, Section 8). Propylene glycol is a monomer in the manufacture of unsaturated polyester resins, which are used for boat and automobile bodies, bowling balls, and playground equipment. 

Both thermoset and thermoplastic resin systems are employed in the construction of composites (Table 8.3). The most common thermoset resins are polyimides, unsaturated polyesters, epoxys, PFs, and amino-formaldehydes. A wide variety of thermoplastic resins have been developed. 

Similar arguments explaining the phase separation were employed by Chou et al. [44]. The dynamics of phase separation was observed using an optical microscope during the course of polyurethane-unsaturated polyester IPN formation at different temperature. Chou et al. suggested that an interconnected phase formed through the spinodal decomposition mechanism developed quickly and was followed by the coalescence of the periodic phase to form a droplet/matrix type of morphology. The secondary phase separation occurred within both the droplet and the matrix phases. Chou et al. did not explain, however, why secondary phase separation occurred. 

This is perhaps attributed to variation in molecular weight (mol.wt.) of PEG-200 as, most of the time, mol.wt. of 200 is achieved by blending PEGs of different molecular weights. In view of this, an unsaturated polyester based on triethylene glycol (TEG), IPA and MAn was developed and this meets the requirements [302]. The properties of three typical batches of TEG-based polyester are given in Table 4.15. 

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