The Effect of the Use of Full Body Harnesses on Their Protective Properties
A full body harness is a component of personal systems protecting against falls from a height. To ensure users’ safety, the harness must retain its protective properties during its whole service period. All the elements of a harness (webbings, threads, metal buckles, etc.) are exposed to destructive factors. Harnesses stored and used for a few years were tested. The paper discusses the most frequent types of damage and their effect on the essential resistance parameters. The effect of atmospheric conditions, sunlight, mechanical damage and dust on the parameters of webbings was tested. Conclusions on the main causes of the loss of the protective properties of harnesses are drawn; periodic checks of the physical conditions and guidelines for estimating acceptable service time are recommended.
Comparison of the UV-degradation chemistry of polypropylene, polyethylene, polyamide 6 and polybutylene terephthalate
The photodegradation mechanism of polymers highly depends on the type and concentration of chromophores present. This influence is studied by making a comparison between the UV-degradation of PE, PP, PA6 and PBT and the thermooxidative degradation of PP at a comparable temperature. The degradation processess are followed by determining the oxygen uptake, CO, CO2 and peroxide formation. During UV-degradation of PP, PE, PA6 and PBT the oxygen uptake is linear in time without an induction period. The oxidation rate of PP is higher than that of PBT, which is slightly higher than the oxidation rate of PA6, while that of PE is the lowest. The determined amount of peroxides depends on the ageing time. For the UV-degradation this does not lead to the expected increase of the oxidation rate, as is the case with thermooxidation of PP. Only a limited proportion of the peroxides formed during the UV-degradation decomposes into radicals. The oxidation rate is mainly determined by other radical forming reactions. In the case of PE and PP this is probably initiation by polymer-oxygen Charge Transfer Complexes (CTCs) and for PA6 and PBT direct photolysis of the amide or the ester linkage, respectively. Thickness degradation profiles show that the UV-degradation processes of PP and PBT are heterogeneous. For PP this is due to oxygen diffusion limitation, while in the case of PBT it is the result of absorption of the UV-light.
Experimental study of thermal modeling for stratospheric platform airships
R&D work on the Japanese stratospheric platform airship is discussed from the viewpoint of the thermal modeling. The work includes two experiments on the thermal characteristics of the 25m-long airship and the 35m-long PV-equipped airship model. The validity of the current thermal model was confirmed by comparing the calculated results with the measured data. The other important work is the Ground-to-Stratosphere (GTS) flight test. A 47mlong airship-shaped balloon was flown to the stratosphere. The flight simulation program into which the thermal model was integrated, was developed and applied successfully to predict the ascent behavior and the flight trajectory.