Plasticization mechanism and structure of polymers

Triphenylmethane (TPM) dyes were used as fluorescence probes for the characterization of thin polymeric layers. Glass transition temperature, mobility and free volume can be determined by this method. A correlation was found between the dye fluorescence and the free volume of the polymer. Above the glass transition temperature of the polymer the activation energies for the rotation of the dye phenyl groups were found at ca. 25 -35 kJ/mol, at temperatures below the glass point these energies are in the range of 5-12 kJ/mol. Nearly all probes describe the free volume equally well. A relation was found between the dye mobility and gas diffusion constants (ammonia and oxygen).

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“…(7) and (8) Fig. 7 give a very good correlation with the literature values ( T f ) 13) of these mixtures (see Fig. 8).…”

Section: *)supporting

confidence: 85%

Determination of the molecular mobility and the free volume of thin polymeric films with fluorescence probes

et al. 1991

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“…Although these theories are widely accepted and used in plasticizer selection for polymers, Shtarkman and Razinskaya (1983) have emphasized the limitation of current theories on the mechanism of plasticization. Indeed, according to these authors, it is not possible to establish a plasticization mechanism because of the huge versatility of the investigated polymer and plasticizer systems; hence, instead of trusting on the above theories, it would be much more useful to consider the direct correlation between compatibility-efficiency-property of each investigated polymerplasticizer blend.…”

Section: Use Of Plasticizersmentioning

confidence: 99%

In vivo and Post-synthesis Strategies to Enhance the Properties of PHB-Based Materials: A Review

Turco

Santagata

Corrado

et al. 2021

Front. Bioeng. Biotechnol.

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The transition toward “green” alternatives to petroleum-based plastics is driven by the need for “drop-in” replacement materials able to combine characteristics of existing plastics with biodegradability and renewability features. Promising alternatives are the polyhydroxyalkanoates (PHAs), microbial biodegradable polyesters produced by a wide range of microorganisms as carbon, energy, and redox storage material, displaying properties very close to fossil-fuel-derived polyolefins. Among PHAs, polyhydroxybutyrate (PHB) is by far the most well-studied polymer. PHB is a thermoplastic polyester, with very narrow processability window, due to very low resistance to thermal degradation. Since the melting temperature of PHB is around 170–180°C, the processing temperature should be at least 180–190°C. The thermal degradation of PHB at these temperatures proceeds very quickly, causing a rapid decrease in its molecular weight. Moreover, due to its high crystallinity, PHB is stiff and brittle resulting in very poor mechanical properties with low extension at break, which limits its range of application. A further limit to the effective exploitation of these polymers is related to their production costs, which is mostly affected by the costs of the starting feedstocks. Since the first identification of PHB, researchers have faced these issues, and several strategies to improve the processability and reduce brittleness of this polymer have been developed. These approaches range from the in vivo synthesis of PHA copolymers, to the enhancement of post-synthesis PHB-based material performances, thus the addition of additives and plasticizers, acting on the crystallization process as well as on polymer glass transition temperature. In addition, reactive polymer blending with other bio-based polymers represents a versatile approach to modulate polymer properties while preserving its biodegradability. This review examines the state of the art of PHA processing, shedding light on the green and cost-effective tailored strategies aimed at modulating and optimizing polymer performances. Pioneering examples in this field will be examined, and prospects and challenges for their exploitation will be presented. Furthermore, since the establishment of a PHA-based industry passes through the designing of cost-competitive production processes, this review will inspect reported examples assessing this economic aspect, examining the most recent progresses toward process sustainability.

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“…[8] The widely accepted mechanism for polymer plasticisation is believed to be the disruption of polymer-polymer interactions and the replacement with plasticiser-polymer interactions that increase the free volume within the polymer structure and so allows freer movement of the chains and hence an increase in flexibility. [9][10][11][12] le Roux reported that much of the structure and properties of Fischer-Tropsch waxes could be learnt from the closely related polyethylene polymer. [13] This may suggest that even though carnauba wax is a mixture of various molecules such as esters, hydrocarbons and fatty acids, the plasticisation mechanism for polymers could be transferable.…”

Section: Introductionmentioning

confidence: 99%

Plasticisation of carnauba wax with generally recognised as safe (GRAS) additives

Zhang

Adams

Zhang

et al. 2016

Polymer

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Plasticization mechanism and structure of polymers

Cited by 21 publications

References 14 publications

Determination of the molecular mobility and the free volume of thin polymeric films with fluorescence probes

Determination of the molecular mobility and the free volume of thin polymeric films with fluorescence probes

In vivo and Post-synthesis Strategies to Enhance the Properties of PHB-Based Materials: A Review

Plasticisation of carnauba wax with generally recognised as safe (GRAS) additives

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