Plasticiser epoxy resin

Aromatic amines formed from the reduction of azo colorants in toy products were analysed by means of HPLC-PDA [703], Drews et al. [704] have applied HPLC/ELSD and UV/VIS detection for quantifying SFE and ASE extracts of butyl stearate finish on various commercial yarns. From the calibrated ELSD response the total extract (finish and polyester trimer) is obtained and from the UV/VIS response the trimer only. Representative SFE-ELSD/UV finish analysis data compare satisfactorily to their corresponding SFE gravimetric weight recovery results. GC, HPLC and SEC are also used for characterisation of low-MW compounds (e.g. curing agents, plasticisers, by-products of curing reactions) in epoxy resin adhesives. 

The cure kinetics of some epoxy resin powder coating composition were reported by Olcese et al.108). These were mixtures of BADGE resins with DICY and an epoxide-amine adduct or an imidazole as accelerator, together with TiOz and plasticisers. Data from DSC scans were analysed using Eq. (2-12) to obtain the apparent activation energy, E. Also Eq. (2-13) and (2-13 a) were used to obtain estimates of E and order... 

Epoxy resins produced by the reaction of bisphenol A and epichloro-hydrin are versatile polymers with several useful properties (subsection 2.2.2.1). However, one significant weakness is their brittle nature. Incorporation of plasticisers is not very useful. Dibutyl phthalate is an exception, showing good compatibility but offering only limited ability to flexibilise the resin. Moreover, plasticisers affect the mechanical properties and chemical resistance of the cured system. With polyurethanes it is possible to complement the flexibility of the epoxy system. Numerous attempts have been made to combine the two types to achieve beneficial modifications (Lee and Nivelle, 1967). These modifications proved successful under high-temperature cure but inferior results were obtained for ambient cures. 

It is possible to accelerate the rate of the polycondensation reaction by incorporation of special catalysts, resulting in urethane-urea-modified epoxy resin. The low-volatility alkyl phenol liberated in this reaction remains in the film as an external plasticiser. Owing to the different rates of the above two reactions, they have been synchronised to produce suitable polymer segments (Figure 10.9). 

Later (1935—45), new materials such as silicone were developed as water repellent and heat resistant paint. The development of epoxy resins offered a structural material for boat and car bodies. Poly(tetrafluoroethylene) (PTFE), polycarbonate, poly(ethylene terephthalate) (PET), polypropylene, polyurethane, ABS and acetals are the latest additions to find their way into plastics technology. Studies have also been carried out with the use of fillers and plasticisers as part of the next generation of materials. 

Epoxy resins used in composite manufacturing are intentionally prepared with an excess of epoxy compared to hardener. This is done to ensure that the hardener is completely reacted during cure and is not allowed to remain in the network and cause plasticisation. A mixture with an epoxy—hardener ratio of 1 1 would not be able to fully cure due to the mobility arguments given in this chapter. The epoxy excess means that there will be a significant number of unreacted and relatively polar functional groups present in the cured 3D network. 

Water molecules plasticise polar polymers such as epoxy and other advanced resins used as matrices for fibre composites so that absorption of moisture can cause the glass transition temperature, Tg, to be reduced significantly. This effect is illustrated in Figure 12.12 [4] and therefore has an impact on the maximum service temperature available to a specific composite system. A rule of thumb for epoxy resins is that Tg is reduced on average... 

A typical cured aerospace epoxy resin is highly cross-linked and may contain a dispersed nonpolar thermoplastic or rubber which reduces the equilibrium moisture content and hmits the reduction in Tg. As shown in Table 12.2, more advanced systems, such as an epoxy—cyanate ester blend, absorb lower concentrations of water at equilibrium. However, the water is not uniformly distributed so that the epoxy phase is stiU plasticised to the same extent. Figure 12.12 shows that the different component epoxies and/or hardeners are plasticised differentially with the development of additional relaxation peaks. We discussed the different degrees of water molecule hydrogen bonding as a function of network polarity in this chapter. 

Many other chemicals have become more expensive because of increases in the price of upstream intermediates. Tin stabilisers are affected by the rising price of tin metal and epoxy derivatives are also affected, with basic epoxy resins going up by about 200 euros/tonne in Eiuope in mid-2004. Some phenohc derivatives have also risen dramatically in price. A snapshot over two or three months diuing mid-2004 shows substantial price increases being announced by leading suppliers for impact modifiers, waxes, silica, phosphorus flame retardants and, as indicated earlier, brominated types. Plasticiser producers were also attempting price increases for DINP and DEHP. 

Hardeners such as amines and anhydrides include many sensitizers. See the sections on epoxy, acrylate and and urethane resins. Triethylamine may irritate and sensitize (Bittersohl and Heberer 1978). Benzoyl peroxide, p-methoxy phenol and hydroquinone are used as accelerators and inhibitors of polymerization (see the chapters on epoxy resin compounds and acrylics in this book). Of the other additives, dioctyl sodium sulfosuccinatey a surfactant, is a potential, rare sensitizer (Fischer 1986), as are dibutyl phthalate and triphenyl phosphate, used as plasticisers (Hjorth 1964). 

Tricresyl phosphate, 2% (plasticiser in resin systems) Triethylenetetramine, 0.5% petrolatum (epoxy resin catalyst)... 

With TG it is also possible to determine glass fibres in polymer systems. Fava [261] recorded TG/DTG curves of PP filled with carbonate and fibreglass. TG is an ideal analytical tool for the control of the glass fibre content in composite materials. Since the glass fibre is thermally inert, there is no problem resolving the weight from the resin (by simple subtraction from 100%). Gibbons [151] has analysed additives such as plasticisers, antioxidants, fillers, and reinforcements for PAll, PE, PP and epoxy resins both qualitatively and quantitatively by DSC and thermomechanical analysis. Fig-... 

The durability of epoxy-aluminium joints that used a homopolymerised epoxy resin was studied by researchers based in Spain [15], and the effects of relative humidity, temperature, and salt concentration analysed. The homopolymerised epoxy resin absorbed little water (1.5 wt%) because of its non-polar network structure. Increasing relative humidity and temperature enhanced water uptake, but the joint strength remained constant because of epoxy plasticisation. A saline environment was damaging to the adhesive joints because of metal corrosion, but was not significantly harmful to the epoxy resin because of the lower diffusion coefficient of salt water. The decrease in glass transition temperature of the epoxy adhesive due to water absorption was dependent upon only the amount of absorbed water and was independent of hydrothermal ageing conditions. The durability of epoxy adhesive joints made underwater has been studied [16]. 

The influence of moisture on the dielectric properties of three experimental resin casting systems and an epoxy based laminate is investigated in this chapter to see if the mechanisms described above, can be recognised. Besides, the resistivity of an epoxy based tank coating and that of plasticised PVC cable insulation material in contact with water is described. 

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