Polyester resins rubbery

Among various rubbery polymeric materials, a special polyester resin has been developed as a binder in view of its curing at ambient temperature, low viscosity (as a result of addition of vinyl monomers) without appreciable sedimentation of explosives. In addition, polyester resin has the greatest advantage of having an oxygen moiety in the skeleton which increases oxygen balance of the final sheet,... 

Tasdemir and Yildirim [22] showed that rigid plastics such as epoxies, PS, PVC, polymethyl methacrylate (PMMA), PP, PC, unsaturated polyester resins and PA can be toughened and their impact properties improved by the incorporation in the formulation of 5-20% of a rubbery elastomer such as ABS terpolymer. 

This type of adhesive is generally useful in the temperature range where the material is either leathery or rubbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mostly uncompounded state. 

While thermoplastic polymers soften at Tg, and if semicrystalline, melt at T, cross-linked polymers do not melt and flow (Fig. 5.2c ). Lightly cross-linked polymers soften as the temperature exceeds Tg, but they remain rubbery solids until the polymer decomposes. Highly cross-linked polymers often do not even soften and retain a high modulus until reaching the decomposition temperature. Thermoset resins, like unsaturated polyester, epoxy, and polyurethanes, have varied levels of cross-linking. However, thermoplastic resins can be modified to contain few cross-links lightly cross-linked polyethylene (XLPE) often improves the mechanical properties of rotomolded parts. 

As a class the polyesters find wide application as fibres, as laminating resins for glass-fibre reinforced cars and boats, in moulding compositions, in surface coatings, as adhesives and as plasticizers for PVC. Elastomeric polyesters may also be prepared. Providing that the molecule is flexible (for example by primarily consisting of a carbon-carbon aliphatic backbone with small substituents on the carbon atoms, does not crystallize or has a very low melting point) then the presence of a few ester links, which increase interchain attraction and reduce rubberiness, is not too adverse on the rubbery properties of the polymer. 

The toughening effectiveness of impact modifiers of any kind in unsaturated polyester and vinyl ester resins will depend on the rate of impact or applied strain, atmospheric conditions (temperature, presence of solvents), and the toughness of the base resin. As the applied strain rate increases or the lest temperature decreases the effectiveness of the rubber additive may decrease. This is because the rubbery particles and the matrix resin b me more brittle under these conditions. As a result, when comparing toughness data from different sources, testing... 

---