The thermo-oxidation resistance and weatherability of' LDPE and HDPE compositions, containing up to 45 wt. $6 calcium carbanate, are investigated. The thermo-oxidation resistance is inrestigated by dynamic D'FA and natural ageing is carried out in an exposure station in a seaside climate. The change in strength and colour after ageing is determined. The behauiours of filled and unfilled polymers are compared. Empirical equations are given, describing the change in the investigated parameters during natural ageing .
A base of experimental data on the ageing of commerial grade plastics is created. In includes assorted physical and chemical properties of plastics and their changes at natural ageing. An automated system for storing and processing of the experimental data is designed. Processing involves mathematical modeling of the changes in properties that aids in empirical prediction. The possibilities of the system are verified with experimental results from a 5‐year ageing period of PE‐LD and PE‐HD. The results show a good agreement between the predicted and real data for selected models.
SynopsisThe long-term behavior of high density polyethylene (HDPE) and poly(viny1 chloride) (PVC) under static mechanical load is investigated. The long-term behavior is determined as a function of stress and temperature. The applicability of the equation proposed by the authors which describes the dependence between the time-dependent failure, stress, and temperature of the two polymers is examined. The equation, derived on theoretical considerations, represents a modification of the Arrhenius equation for the chemical reaction rate. It is found that there is a complete agreement between the experimentally determined long-term behavior of PVC and HDPE and that calculated by the equation over the whole examined range of temperatures and stresses, with the exception of narrow intervals for HDPE where an intensive plastic deformation is developed.
The aim of the present work is to predict the warehouse storage life of polyethylene low-density, polyethylene high-density and polystyrene impact-resistent, using the method of temperature-time superposition. The properties, most representative for thermal ageing, are the relative elongation at break for polyethylene and the impact resistance for polystyrene. The validity of the predicted shelf-life is verified by estimating the change of these properties under real conditions of warehouse storage.
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