Unsaturated polyesters fillers

Alkyds are formulated from polyester resins, cross-linking monomers, and fillers of mineral or glass. The unsaturated polyester resins used for thermosetting alkyds are the reaction products of polyfunctional organic alcohols (glycols) and dibasic organic acids. 

Unsaturated Polyesters. There are two approaches used to provide flame retardancy to unsaturated polyesters. These materials can be made flame resistant by incorporating halogen when made, or by adding some organic halogen compound when cured. In either case a synergist is needed. The second approach involves the addition of a hydrated filler. At least an equal amount of filler is used. 

The relative effectiveness of nucleating agents in a polymer can be determined by measuring recrystallization exotherms of samples molded at different temperatures (105). The effect of catalyst concentration and filler content has been determined on unsaturated polyesters by using dynamic thermal techniques (124). Effects of formulation change on the heat of mbber vulcanization can be determined by dsc pressurized cells may be needed to reduce volatilization during the cure process (125). 

This is also known as Bulk Moulding Compound (BMC). It is blended through a mix of unsaturated polyester resin, crosslinking monomer, catalyst, mineral fillers and short-length fibrous reinforcement materials such as chopped glass fibre, usually in lengths of 6-25 mm. They are all mixed in different proportions to obtain the required electromechanical properties. The mix is processed and cured for a specific time, under a prescribed pressure and temperature, to obtain the DMC. 

Methacrylates possess many advantages, and alternatives to them are rarely seen in the marketplace. An early example using styrene in a structural adhesive has been reported [26]. The combination of styrene with unsaturated polyester is commonly used as a filler and bonding putty. 

For a complete panel replacement, the refinisher starts with a panel preprimed in the appropriate stoving primer. For spot repairs or larger repairs without replacement of metal, there will be areas which have to be rubbed through to clean metal. Any indentations then have to be filled with a stopper or spray filler, probably based on unsaturated polyester resins and styrene, with cure initiated by mixing in an organic peroxide. After sanding, remaining bare metal areas are sprayed with a two-pack etch primer. 

A pyrolysis technique was investigated as a method for the chemical recycling of glass fibre-reinforced unsaturated polyester SMC composites. The proeess yielded liquid products and gases and also a solid residue formed in the pyrolysis of glass fibres and fillers. The solid residue was used as a reinforeement/filler in unsaturated polyester BMC composites, and the influenee on mechanical properties was studied in comparison with BMC prepared entirely from virgin materials. 

In addition, fillers can be used for both cost reduction and property modification. Table 21.3 presents some examples of typical fillers and their effects on the unsaturated polyester resin formulation properties. 

Sheet molding compounds (SMCs) and bulk molding compounds (BMCs) are the dominant materials used in automotive applications. These composites of unsaturated polyester resin, fillers and fiberglass have advantages of high stiffness, heat resistance and low coefficient of expansion. Coupled with low creep resistance, which is a distinct advantage over thermoplastic competition, and low-profile additives, which can yield Class A surfaces, these materials are well suited for applications from exterior body panels to under the hood components. 

Unsaturated polyesters are relatively brittle and about 70% are used with fillers, of which glass fiber is easily the most popular. Glass fiber-reinforced polyester for small boat hulls consumes one quarter of unsaturated polyesters. Automobiles, furniture, and construction also make use of this thermoset resin. 

Unsaturated polyesters are auto body fillers. They are commonly used in place of solder for many applications. 

Whereas McGee [188] did not verify any effect of particulate fillers (i.e., glass, calcium carbonate, and aluminum) on the reaction kinetics, Lem and Han [185], working with calcium carbonate and clay in an unsaturated polyester resin, concluded that the reaction rate increases by increasing the filler content. 

The mechanism of reduction of NG absorption in halopolyesters (chloropolyesters and bromopolyesters) and filled unsaturated polyesters and halopolyesters (after addition of fillers) has already been proposed by us [322] and accordingly, techniques for reduction of NG migration have been suggested [323-325]. 

The acid-base properties of polymers, fillers and silane additives, as described by Fowkes [14] can be used to predict the effect of silanes on the dispersion of fillers in polymer, and viscosity of the mix. In general, opposites attract (give good dispersion) while like materials repel (poor dispersion) [15]. The effect of cationic silane (Z-6032) on the dispersion of silica (acidic filler) in this particular unsaturated polyester resin (acidic polymer) is shown in Table 6. Addition of Z-6032 in increments to a silica-filled polyester resin lowered the viscosity of the mixture to a minimum at about 0.4% silane based on the filler. 

Wan Hanafi, W.Z.A. and Hornsby, P.R., Smoke suppression and fire retardancy in unsaturated polyester compositions containing hydrated fillers, Plast. Rubber Composites Process. Appl., 19, 175-184, 1993. 

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