Physical Aging of Polymer Blends

Cowie, J. M. G.; Arrighi, Valeria

doi:10.1007/978-94-007-6064-6_15

Cited by 12 publications

(14 citation statements)

References 100 publications

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“…Physical ageing refers to long-term changes in the local packaging of the chains polymers chains in the amorphous regions of rapidly cooled samples. 19 Over time the material shrinks as the polymer chains rearrange, and while the process is temperature dependant it continues slowly even at room temperature. The increase in stiffness and reduction in elongation observed in the samples stored at 40°C, 50°C, 60°C, 80°C and 100°C did not occur in the samples aged at room temperature, with no statistically significant changes being observed in the samples stored at room temperature over the 6-month study period.…”

Section: Resultsmentioning

confidence: 99%

Ageing of laser sintered glass-filled Polyamide 12 (PA12) parts at elevated temperature and humidity

Dooher

Archer

Walls³

et al. 2021

Polymers and Polymer Composites

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Additive manufacturing is traditionally used to manufacture either prototypes or very small-scale demonstrators. In recent years though, it is being increasingly used to make low volume parts for the aeronautical and defence industry. One concern with laser sintered parts is that their relatively porous nature, means that they may be more susceptible to ageing than injection moulded parts. Parts were aged for 6 months in at different temperatures (18°C, 40°C, 50°C, 60°C, 80°C and 100°C) and in a humidity chamber at 60°C and 80% relative humidity. Each month samples were removed for characterisation. The testing included tensile testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and gas pycnometry. During ageing the samples displayed visible discolouration and embrittlement over the 6-month test period. This embrittlement was not observed in those samples aged at room temperature or an elevated humidity. The observed yellowing in the samples aged above ambient temperature is likely a result of the build-up unsaturated degradation products. No significant differences as a result of ageing were observed via DSC, TGA, SEM or gas pycnometry.

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Section: Resultsmentioning

confidence: 99%

Ageing of laser sintered glass-filled Polyamide 12 (PA12) parts at elevated temperature and humidity

Dooher

Archer

Walls³

et al. 2021

Polymers and Polymer Composites

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“…The small movements of molecules within the glassy matrix can be a source of ‘physical ageing’ of the structure, which has been implicated in the deterioration of foods, plastics and pharmaceutical compounds (e.g. Cicerone et al, 2003; Roudaut et al, 2004; Kucera et al, 2013; Cowie and Arrighi, 2014). Over time, molecules that were entrapped by neighbouring molecules budge (or relax) and begin to fill in the pores.…”

Section: The Role Of Glassy Matrices In Survival and Deterioration Ofmentioning

confidence: 99%

Dry architecture: towards the understanding of the variation of longevity in desiccation-tolerant germplasm

Ballesteros

Pritchard

Walters³

2020

Seed Sci. Res.

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Desiccation-tolerant (DT) plant germplasm (i.e. seeds, pollen and spores) survive drying to low moisture contents, when cytoplasm solidifies, forming a glass, and chemical reactions are slowed. DT germplasm may survive for long periods in this state, though inter-specific and intra-specific variation occurs and is not currently explained. Such variability has consequences for agriculture, forestry and biodiversity conservation. Longevity was previously considered in the context of morphological features, cellular constituents or habitat characteristics. We suggest, however, that a biophysical perspective, which considers the molecular organization – or structure – within dried cytoplasm, can provide a more integrated understanding of the fundamental mechanisms that control ageing rates, hence the variation of longevity among species and cell types. Based on biochemical composition and physical–chemical properties of dried materials, we explore three types of the interplay between structural conformations of dried cytoplasm and ageing: (1) cells that lack chlorophyll and contain few storage lipids may exhibit long shelf life, with ageing probably occurring through slow autoxidative processes within the glassy matrix as it relaxes; (2) cells with active chlorophyll may die quickly, possibly because they are prone to oxidative stress promoted by the photosynthetic pigments in the absence of metabolic water and (3) cells that lack chloroplasts but contain high storage lipids may die quickly during storage at −20°C, possibly because lipids crystallize and destabilize the glassy matrix. Understanding the complex variation in structural conformation in space and time may help to design strategies that increase longevity in germplasm with generally poor shelf life.

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“…The longer the aging time, the closer the polymer will approach its equilibrium state. [ 61 ] It is important to mention that the storage modulus results show that the increase in mobility is not associated with the disappearance of the stress relief phenomenon.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…In this series, the enthalpy relaxation increases rapidly from 0.0123 to 1.2589 J/g within 5 h of aging, this is due to the fact that when a polymer is aged at temperatures close to the T g , the aging process is further accelerated. [61] Conversely, samples of the series M and N (Figure 8B,C) exhibit lower relaxation enthalpy values than the series L. This may be due to the fact that the PS phase at these aging temperatures (100 and 105 C) is already very close to the thermodynamic equilibrium state. [61,62] On the other hand, slight exothermic minima that increase with t a (up to a maximum of 0.13 J/g) appear in series M and N just before the PC's T g .…”

Section: Dsc Analysismentioning

confidence: 90%

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Physical aging of PC:PS blends: Dynamic mechanical analysis and nuclear magnetic resonance studies

Charif¹,

Doulache²,

Gourari³

et al. 2022

Polymer Engineering & Sci

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The effect of physical aging of the partially miscible blend of polycarbonate: polystyrene (PC:PS) at temperatures near the glass transition temperature (T g ) of the PS was studied as a function of time. For this purpose, blends of PC and PS with different ratios were elaborated and characterized using SEM, FTIR, DSC, and DMA techniques. The results indicated the presence of weak interaction upon blending with a maximum of interaction for the 50:50 blend. The effect of physical aging on the latter was then investigated via DMA, DSC, and NMR analyses. The DMA results showed that both phases were sensitive to aging. The effect was found to be strongly dependent on both the temperature and time. The aging of PC:PS blend was also found to trap stress during the process which induced an instability in the viscoelastic behavior. The latter was found to be associated with a phase-separation morphology of the blend and influenced by its composition. The NMR analysis also showed a pronounced distortion of the conformation combined with increasing molecular motion. These effects were found to be important for aging below the PS's T g .

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Physical Aging of Polymer Blends

Cited by 12 publications

References 100 publications

Ageing of laser sintered glass-filled Polyamide 12 (PA12) parts at elevated temperature and humidity

Ageing of laser sintered glass-filled Polyamide 12 (PA12) parts at elevated temperature and humidity

Dry architecture: towards the understanding of the variation of longevity in desiccation-tolerant germplasm

Physical aging of PC:PS blends: Dynamic mechanical analysis and nuclear magnetic resonance studies

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