Artificial ageing 678 Subject

Attempts in this laboratory to characterize real or artificial aging with other kinds of analytical observations (color, reflectance, pH, etc.) and to subject these data in turn to Arrhenius plots has been even less successful. In general, the magnitude of the observed change and the inherent analytical errors do not allow Arrhenius plots. Among the test methods used, folding endurance is unusually sensitive compared with other test methods with respect to aging and component composition. 

Application Prooedyres. All fabric samples were cut to 4 x 6 inch (W x F) rectangles. Three r licate cimens were process for each treatment to be subjected to ecch of the artificial aging acperiments described below. Ebr the comparison samples which were not to be artificially ciged, six r licate specimens were treated either with water ch one of the cdJcaline agents. 

Artificial Aging.—The chemist distinguishes between aging and maturation that is, between the mere passage of time and the effects thereby produced. If the latter can be duplicated within a short period, the results, from the chemist s and from an economic point of view are much preferable. Hence much study has been given to the subject of the artificial aging of spirits. Many of the more scientific suggestions are admirably summarized by Snell and Fain in an article which appeared in Ind. Eng. Chem. News Ed. XII, 7, p. 120. They state ... 

In the initial state, the basic solid solution phase subjected to partial decomposition by artificial aging (Fig. 5, arrows 1, 2, and 11), contained 3.8 to 4.6% Cu in the higher-purity alloy and 4.5 to 5% in the normal alloy. The difference was probably caused by a variation in the heat treatment of the alloys. 

Mechanical Behavior Variation of an Isotactic Polypropylene Copolymer Subjected to Artificial Aging... 

The chapter shows the analysis of the mechanical properties variation of an isotactic polypropylene copolymer, when this material is subjected to artificial aging according to the standard UNE 4892. 

In the first phase of the developed process a series of samples was subjected to artificial aging in a climatic chamber. The mechanical properties of the original material used and the aged polypropylene were obtained by tensile tests. 

Once the mechanical propjerties of both materials were obtained, a series of numerical calculations by means of the Finite Elements Method (FEM) were made. The results of the numerical tests allow for obtaining the variation of the mechanical behaviour of the material subjected to artificial aging with resp>ect to the original polypropylene. 

For this, 5 samples were subjected to cyclical periods of UV exposure, followed by periods without radiation. During these cycles, changes in temperature and humidity were carried out according to the standard UNE 4892. This standard is the one governing the artificial aging tests and it was used as a guide in the investigation developed. 

Figure 1 shows the inside of the climatic chamber with the samples subjected to artificial aging. Figure 2 shows the position of the samples in the dimatic chamber, which were pxjsitioned in the irradiation zone of the lamp. This lamp is represented in the figure 2 by an X. 

Once the samples of isotactic polypropylene copolymer were subjected to the artificial aging process, the next phase in the development process was to obtain and comp>are the mechanical proporties of the aged material and the mechanical properties of the original material. 

The mechanical properties used in the definition of polypropylene were the averages of the results obtained in tensile tests carried out on the samples subjected to artificial aging and the initial polypropylene samples. The material of the semi-sphere was defined as a linear steel with a Yoimg modulus E = 210GPa, density y = 7850 kg/ m and Poison ratio u = 0.3. 

Tensile tests carried out on samples of original polypropylene and polypropylene subjected to artificial aging had provided force-displacement curves of the materials, which are shown in figures 6 and 7. 

Fig. 7. Stress-displacements curves of the polypropylene subjected to artificial aging samples...

The third parameter analyzed is the strain energy, figure 10. This parameter represents the energy used in the deformation of the Polypropylene sheet on the impact. The results obtained show that the energy used in the deformation of the polypropylene sheet subjected to artificial aging is higher than in the original material for the three load cases analyzed. 

The research process developed allows for obtaining the mechanical properties variation of isotactic polypropylene copolymer subjected to artificial aging. 

Subsequently, 10 samples (5 of material subjected to artificial aging and 5 samples of original polypropylene) were subjected to tensile tests in order to obtain the mechanical properties of the original pwlypropylene and the material subjected to artificial aging. 

The minimal variations obtained of the mechanical properties of polypropylene subjected to artificial aging with respect to the original material show that the polypropylene is a suitable material for the design of systems to protect motorists and cyclists. These protection systems are continually exposed to environmental effects, and therefore a continuous aging process. 

Fig. 57. Relation between fatigue limit after the cycles of 10 and tensile fracture strength for an as-extruded Alg sNigMuh s alloy. The data for conventional Al-based alloys are also shown for comparison. The symbols O, T4 and T6 represent the samples that were subjected to annealing, natural aging after solid solutioning and artificial aging after solid solutioning, respectively.

Kiat-Amnuay S, Lemon JC, Powers JM.( 2002) Effect of opacifiers on color stability of pigmented maxillofacial silicone A-2186 subjected to artificial aging. J Prosthodont 11 109-16. 

Figure 9. DSC thermograph for Material B9 subjected to 6000 hours of exposure to artificial aging in a UVCON (80/50) apparatus. Determination of the glass transition temperature is shown in the figure. (Reprinted withpermission.) ...

All experimental and surgical procedures were approved by the Animal Care and Ethics Committee of Kanazawa University. The subjects of our investigations were female Japanese macaque monkeys (Macaca fuscata). These were kept in air-conditioned cages sized approximately 1 m on a side. The monkeys were allowed free access to water and were daily fed with artificial animal food, and fruits or vegetables. In total, tissues from 29 monkeys were included in the present study one monkey was neonatal (14 days old, sacrificed on postnatal day 14 P14), while the rest of the monkeys were sexually mature (age of 5-13 years). 

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