Physical aging definition

Physical aging in the epoxy matrix definitely affects the long-term mechanical properties of the composite. As the material was further sub-Tg annealed at 140 °C for 102, 103, 104, and up to 105 minutes, the toughness and other ultimate properties... 

The polymers physical aging represents itself the structure and properties change in time and is the reflection of the indicated materials thermodynamically nonequilibriiun nature [61, 62], As a rule, the physical aging results to polymer materials brittleness enhancement and therefore, the ability of structural characteristics in due course prediction is important for the period of estimation of pol5mier products safe exploitation. For cross-linked polymers the quantitative estimation of structure and properties changes in physical aging process was conducted in Refs. [63, 64] within the frameworks of fracture analysis [65] and cluster model of polymers amorphous state structure [7, 66]. The authors of Ref. [67] use the indicated theoretical models for the description of PC physical aging. Besides, for PC behavior closer definition in the indicated process such theoretical notions were drawn as structure quasiequilibrium state [68] and the thermal cluster model [69], which is one from variants of percolation theory. 

AGE. Although aging involves biochemical processes, it is observed as a physical occurrence. Aging definitely increases the risk of cancer as Fig. C-18 illustrates. 

The most definitive diagnosis of AD is a postmortem examination of the brain for the presence of two characteristic lesions the neuritic plaque (NP) and the neurofibrillary tangle. Both structures were originally described in 1906 by Alois Alzheimer using silver-based histological stains. The discovery of NPs was hailed as a watershed moment in the history of neurological disease as it helped shift society s perception of age-related dementia from social stigma to physical disease [2]. 

Q. You also advised that a definitive statement from a responsible official emanate as follows "Questions have been raised concerning the status of Germany s so-called storm troops. These number about 2,500,000 men between the ages of 18 and 60, physically well trained and disciplined, but not armed, not prepared for war, and organized only for the purpose of preventing for all time the return of the Communist peril."... You made such a statement to your client ... 

The definitions of the degree of mixing presented above aim at a local characterization of the mixture homogeneity in the physical space. There also exist more indirect mixing indices. The segregation index J of Danckwerts (12) is one of the most famous ones. It applies to continuous reactors and relies upon the variance of age J = Var oip/Var a>where a is the age of a molecule,... 

Put very simply, copal is young version of amber. There is no definite age at which copal turns into amber, as the process is continuous firom the moment the resin appears on the tree and begins to solidify. In physical terms, when the resin is sufficiently cross-linked and polymerised it becomes amber (see Chapter 13, Plastics ). In other words, the resin has dried out and hardened. This process takes thousands if not millions of years, and not all copal becomes amber as much of it disintegrates with time. Furthermore, as the process is such a long one it is not possible for us to follow it or to replicate it in a laboratory, so there is still much that is speculation. We know, however, that there are some instances of copal that have begun to look like, and take on, the properties of amber. 

---