Copolymerisation polyester resin

Structures present in cured polyester resin. Cross-linking via an addition copolymerisation reaction. The value of n 2-3 on average in general purpose resins... 

IPNs are found in many applications though this is not always recognised. For example conventional crosslinked polyester resins, where the polyester is unsaturated and crosslinks are formed by copolymerisation with styrene, is a material which falls within the definition of an interpenetrating polymer network. Experimental polymers for use as surface coatings have also been prepared from IPNs, such as epoxy-urethane-acrylic networks, and have been found to have promising properties. 

The time-dependent evolution of the polymerisation and copolymerisation reactions of styrene/unsaturated polyester resin was characterised using optical levitation with Raman spectroscopy (135). The n-butyllithium-initiated anionic polymerisation of styrene in ethylbenzene was measured using Raman spectroscopy (214). 

For the free radical copolymerisation of unsaturated polyester resins containing an inhibitor, the following simplified mechanism could be used. 

For the cure study of radical reactions, such as the unsaturated polyester resin-styrene copolymerisation, a different and more elaborated approach incorporating a molecular weight dependent diffusion coefficient, shouldbe employed to take the Trommsdorff, or gel, effect into account. 

An unsaturated polyester resin has two primary components, a polyester containing polymerisable double bonds and a copolymerisable solvent monomer, of which the most commonly used is styrene. Unsaturated polyesters are made by esterification of glycols with mixtures of maleic anhydride and saturated diacids (Structure 9.1). The term alkyd is used to describe low-molecular-weight polyesters, where molecular weight is broadly... 

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

Because of its low price, compatibility, low viscosity and ease of use styrene is the preferred reactive diluent in general purpose resins. Methyl methacrylate is sometimes used, but as it does not copolymerise alone with most unsaturated polyesters, usually in conjunction with styrene in resins for translucent sheeting. Vinyl toluene and diallyl phthalate are also occasionally employed. The use of many other monomers is described in the literature. 

The earliest synthetic resin to be used in commerce seems to have been a polyester then termed ester gum, which was made by esterifying rosin (essentially an unsaturated monocarboxylic terpenoid acid, abietic acid) with glycerol. When cooked with tung oil (a glycerol ester of 9,11,13-octadecatrienoic acid), this provided varnishes that dried overnight. In this case, the polymer is formed by an addition copolymerisation process, but the product is nevertheless also a polyester. 

Medium oil length mahua oil-based pentalkyds (polyesters) were prepared with varying degrees of excess hydroxyl, which was converted into liquid crystalhne form by copolymerising with p-hydroxybenzoic acid in the presence of dicyclohexyl carbodiimide (DCC) (Fig. 4.3). An improvement was observed in the resistance to scratching and the drying time of the hquid crystalhne resins. These have low viscosity and good film properties. 

As stated in Chapter 1, modification of existing commercial polymers by physical and chemical means is one of most widely used industrial techniques for improving the properties of base polymers without the need to develop new polymers. Like other resins, polyesters may also be modified by functionalisation, copolymerisation, blending, interpenetrating network formation, and so on. The properties of oil-modified polyesters may be improved by appropriate modification with a variety of reactive chemicals and other polymeric materials. 

Before vitrification, a heat capacity change as a result of chemical reaction, ACp,react, is noticcd. For the anhydride-cured epoxy and the polyester-styrene resin a minor, but reproducible, and almost linear decrease of Cp with conversion is observed. The former system is supposed to be an anionic chain-growth living polymerisation (without termination), the latter is a chain-growth copolymerisation with termination. 

The -R groups in the APES and AAMS contain amines, which would make them reactive with epoxide adhesives or liquid resins. As GPMS contains epoxide groups, it would react with amine groups in adhesives or resins. The carbon-carbon double bonds in MPMS of VMS would copolymerise with styrene and unsaturated polyester in liquid resins, by a free radical mechanism. 

The practical consequences of an auto-acceleration effect on exotherm and conversion are illustrated by the exotherm curves in Figure 9.1. The urethane methacrylate/methyl methacrylate resin that shows auto-acceleration at all oligomer/monomer ratios is compared with an unsaturated polyester/styrene resin, which only shows an autoacceleration (or gel effect ) at high alkyd/styrene ratios. The urethane methacrylate oligomer copolymerised with styrene shows virtually the same exotherm behaviour as the unsaturated polyester for equivalent styrene/oligomer unsaturation ratios. 

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