Effect of Small Molecule Antiplasticiser

In the case of polycarbonates, it has been observed that by adding miscible low molecular weight additives, with specific chemical structures, it is possible to increase the yield stress of the polymer, as well as to reduce the local molecular motions that are responsible for the secondary relaxation processes 

Some antiplasticisers exist for PET [13] and it is interesting to study their effect on the / relaxation in PET, using the same investigation tools as the ones applied to pure PET. 

Other compounds [13] have very similar effects. 

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Such an effect of small molecule antiplasticiser is not specific to BPA-PC. It seems to occur with most polymers undergoing a transition originating from motions in the main chain. In the present paper, the effects of antiplasticisers on the f3 transition of poly(ethylene tere-phthalate) and epoxy networks are analysed in Sects. 4 and 7, respectively. 

Furthermore, the effect of miscible small molecule additives, antiplasticisers, on the secondary transition, is worth analysing in order to reach a deeper understanding of the involved molecular motions. 

It appears that it is mostly the high-temperature part of the fi transition which is suppressed, leading to a downward shift of the peak maximum. As presented in Fig. 71, the strength of the fi relaxation, expressed by the area under the dynamic mechanical loss, peak, Rsec, decreases much more rapidly with increasing the AP concentration that it should according to a dilution effect. It is worth pointing out that a similar behaviour has been reported, a long time ago, on the same system [53] and is encountered in BPA-PC-antiplasticiser mixtures, irrespective of the specific nature of the antiplasticiser small molecule [16,17,53,54]. 

In a way similar to that described for polyethylene fere-phthalate (Sect. 4.2), some antiplasticiser small molecules with a specific chemical structure are able to affect the ft transition and the yield stress of epoxy resins, but they do not have any effect on the y transition. In the case of HMDA networks, an efficient antiplasticiser, EPPHAA, whose chemical structure is shown in Table 8, has been reported [69]. The investigation of such antiplasticised epoxy networks by dynamic mechanical analysis as well as solid-state NMR experiments [70] can lead to a deeper understanding of the molecular processes involved in the ft transition and of their cooperativity. 

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