Physical ageing of organic coatings

Perera, Dan Y.

doi:10.1016/s0300-9440(03)00037-7

Cited by 105 publications

(41 citation statements)

References 104 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This process has different terms such as physical aging, structural relaxation and annealing, and has been well studied in polymers (Hutchinson, 1995;Giovambattista et al, 2005). Perera (2003) describes physical aging as a general phenomenon involving the spontaneous relaxation process of a material that occurs in its glassy state due to its non-equilibrium state after processing. Effects of physical aging include reductions in free volume (V), enthalpy (H), and entropy (S).…”

Section: Introductionmentioning

confidence: 99%

Physical aging of processed fragmented biopolymers

Gonzalez

Khalef

Wright

et al. 2010

Journal of Food Engineering

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Physical aging of processed fragmented biopolymers

Gonzalez

Khalef

Wright

et al. 2010

Journal of Food Engineering

View full text Add to dashboard Cite

“…Decreasing gas and water vapor permeability [4][5][6] with physical aging was observed in crosslinked polymer films. Studies on physical aging reported in the literature [3][4][5][6][7][8][9][10][11] are mainly concerned with changes in the thermal and mechanical properties with continuous exposure to simple isothermal conditions. If temperature varies, polymers age physically more when the temperature is decreasing than when it is increasing.…”

Section: Introductionmentioning

confidence: 99%

Concurrent physical aging and degradation of crosslinked coating systems in accelerated weathering

2008

View full text Add to dashboard Cite

Coating degradation is a combination of both chemical and physical processes; however, physical processes have not received much attention. Physical aging has a non-negligible effect on coatings' mechanical properties and permeability etc. through the densification that continues as a polymer approaches its thermodynamic equilibrium below the glass transition temperature, T g . Observations in recent work showed that physical aging affects coatings' mechanical property response during accelerated weathering and is, itself, affected by the associated chemical degradation. Two crosslinked coating systems were studied in order to compare different chemical compositions, their T g , and their thermal response in accelerated weathering. During thermal cycling, physical aging measured by enthalpy recovery exhibited different trends in the two coatings. A ''rejuvenation'' mechanism was observed in the coating with a T g between the top and bottom limits of the exposure cycle; continued aging was observed for the coating with a high T g . Stress relaxation tests detected aging and ''memory'' behavior over periods comparable with accelerated weathering cycles. Both thermal and mechanical responses changed in complicated and different ways as the coatings degraded. Different degrees of coating thickness reduction were observed in both isothermal relaxation and degradation. When various coatings are evaluated, simply judging their performance under the same weathering environment is not reliable since polymer relaxation behavior depends on the relationship between the exposure temperatures and the T g of each polymer.

show abstract

“…22 Sucrose is generally seen as a fast relaxing molecule (lower c ) compared to starch or other macromolecular materials, which appear much more stable. The influence of the small molecule content on relaxation enthalpy was considered by Blond,23 who reported that, when dextran was added to sucrose, the relaxation enthalpy of the mix was less ''pronounced'' than that of pure sucrose.…”

Section: Introductionmentioning

confidence: 99%

Influence of sucrose and water content on molecular mobilityin starch‐based glasses as assessed through structureand secondary relaxation

Poirier-Brulez¹,

Roudaut²,

Champion³

et al. 2005

Biopolymers

View full text Add to dashboard Cite

Molecular mobility is known to be a key parameter in controlling the physical properties of materials and thus their quality and performance. Beyond glass transition related changes, attention should be called to the impact of local motions remaining in the glassy state. Gelatinized waxy maize starch at different sucrose contents (0-20% solids) was equilibrated between 0 and 14% water and sorption isotherms determined at 25 degrees C. The effect of water and sucrose content on the molecular mobility of glassy starch was investigated by differential scanning calorimetry through enthalpy relaxation studies and dynamical mechanical thermal analysis. The existence of sucrose-starch interactions was suggested by the sorption isotherms not following the expected additivity of the single component sorption curves. Contrary to the glass transition or associated alpha relaxation, water and sucrose affected differently the secondary relaxations. Indeed, the beta relaxation observed around -15 degrees C was shifted to lower temperature upon increasing hydration, and to higher temperature when sucrose content increased, suggesting a hindering of these local motions. Enthalpy relaxation of the ternary mixtures was studied following aging up to 668 h at Tg -15 degrees C. Ternary mixtures exhibited an enthalpy relaxation upon aging lower than starch alone as a sign of lower polymer mobility in the presence of small molecules, contrary to the free volume theory. Relaxation kinetics were characterized with the Cowie-Ferguson model and compared to literature data. The extent of the enthalpy relaxation appeared to be controlled by the distance between the aging temperature and the beta relaxation temperature.

show abstract

Physical ageing of organic coatings

Cited by 105 publications

References 104 publications

Physical aging of processed fragmented biopolymers

Physical aging of processed fragmented biopolymers

Concurrent physical aging and degradation of crosslinked coating systems in accelerated weathering

Influence of sucrose and water content on molecular mobilityin starch‐based glasses as assessed through structureand secondary relaxation

Contact Info

Product

Resources

About