Polyester stabilisation

As is often the case with patents, little information is provided on any proposed mechanism for the stabilising action of these additives, althongh it is very likely that many of them will act in some way to control or snppress reactions at chain ends. A more focused discussion of this aspect of polyester stabilisation, along with examples of additives specifically targeted towards this aspect of polyester chemistry, is given in Section 6.3. 

Besides resin and reactive diluent, additives are commonly incorporated into polyester resins. These include not only curing agents and fillers (see Section 25.2.3) but also ultraviolet stabilisers. The latter are particularly important for outdoor applications such as roof lighting, benzotriazoles being particularly effective. 

Formulations for one-shot polyether systems are similar to those used for flexible foams and contain polyether, isocyanate, catalyst, surfactant and water. Trichloroethyl phosphate is also often used as a flame retardant. As with polyesters, diphenylmethane di-isocyanate is usually preferred to TDI because of its lower volatility. Tertiary amines and organo-tin catalysts are used as with the flexible foams but not necessarily in combination. Silicone oil surfactants are again found to be good foam stabilisers. Volatile liquids such as trichlorofluoro-methane have been widely used as supplementary blowing agents and give products of low density and of very low thermal conductivity. 

Typical additive packages for engineering thermoplastics have been described by Titzschkau [9], such as processing aids for PA, PP, or PET/PBT, three-component additive packages for polyamides and polyesters (nucleating agent, lubricant and process heat stabiliser) and coated copper stabilisers for polyamides. Additive packages or combinations of up to five or more additives are quite common. A typical white window PVC profile formulation comprises an acrylic impact modifier, TiC>2, CaCC>3, calcium stearate, a... 

As reported by Nelissen [58], unreacted carbodi-imides (Stabaxol I, P and P100), used as hydrolysis stabilisers in e.g. polyesters, are readily detected by IR analysis on the basis of the —N=C=N—absorption at 2140 cm 1, but without further discrimination within... 

Figure 12.3 Examples of the weathering performance of (a) a stabilised HDPE nonwoven and (b) a polyamide/polyester nonwoven deliberately unstabilised against ultraviolet radiation. Both were exposed to artificial weathering using three different types of apparatus and to natural weathering in two locations. All results are plotted against radiant exposure (total ultraviolet light energy...

Zimmerman, H Degradation and stabilisation of polyester in Developments in Polymer Degradation —5, Grassie, N. (Ed.), Applied Science Publishers, London, 1984, Ch. 3 79-119. 

There is interest in trace metal levels in both natural and synthetic fibres and fabrics but perhaps most interest is in synthetic fibres as these may contain residues of catalysts, treatments or stabilising agents. Reviews have been published of trace-metal analysis of rayon, polyamide, polyester and polypropylene fibres [178] and of cotton fabrics, especially for flame... 

The thermal and UV stabilising action of linear, low molec.wt. unsaturated polyesters and epoxy resins in PVC was investigated using short-term tensile and long-term tensile creep testing and calculations of isochronous creep... 

Four different polyester plasticisers for PVC, having moderate acid numbers (11.5 to 20.5 mg KOH/g resin), were synthesised. These polyesters were modified by converting the terminal COOH group to Ba(II) and Cd(II) carboxylate salts in order to introduce the capability of heat stabilisation for PVC. The modified polyesters were applied as dual function polyesters, i.e. as plasticisers and stabilisers at the same time. The thermal stabilisation efficiency of the plasticised PVC films formed was tested photometrically and the data obtained were compared with that afforded by Irgastab BZ 556. The efficiencies of these modified polyesters as heat stabilisers for PVC were found to be comparable with those of Irgastab BZ 556. 38 refs. CIBA-GEIGY CO. 

Acrylics, unsaturated polyesters and other monomer-based adhesives containing ethy-lenic unsaturation, cure by formation of free peroxide radicals formed with transition metal ion donators such as cobalt, iron, copper and nickel. In engineering applications the presence of transition metals on surfaces sees them act as initiators by forming the free peroxide radicals from the added peroxide compound(s). The base monomers usually contain inhibitors such as phenols or other materials classed as peroxide stabilisers to... 

Peracetic acid can also be used for bleaching polyester/cotton blended fabrics with a solution containing 4 g/1 peracetic acid, 1 g/1 tetrasodium pyrophosphate (stabiliser) and 1 g/1 wetting agent with a liquor ratio of 5 1. Peracetic acid has a pH of about 1.5 and the bleaching bath solution is adjusted to pH 5.5 with the help of dilute alkali. The material is entered cold and run for 10 min. Then the temperature is raised to 65-70 C in 15 min and bleaching is continued at this temperature till the concentration of peracetic acid drops to 0.09 g/1. The fabric is then washed thoroughly... 

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