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Metal or concrete columns are most often used as load-bearing structures in greenhouses. In the Republic of Croatia, these columns will be replaced by PVC-U pipes. However, as it is known that the properties of polymer materials decrease after they are exposed to atmospheric conditions, it is necessary to test whether they can withstand these conditions. The aim of these studies is to compare the tensile properties of pipes of different formulations of polyvinyl chloride before and after aging. Three different types of PVC-U were chosen for the tests, depending on their molecular weight and degree of polymerization. Two types of K58, which belong to the group of PVC that have lower mechanical properties, but are the easiest to process, and K64 which belongs to the most popular PVC because it has a good balance between mechanical properties and processability. Aging was carried out in a weather aging chamber at an irradiation of 550W/m2, a temperature of 65C, and a humidity of 65% for 1000h whereas dry time and wet time exposure alternated in duration of 102 min and 18 min. The strain decreased by 50% with modified white medium density PVC (K58) / filler D50>1.5 micron and with unmodified transparent crystal PVC (K58) tensile strain was reduced by 90%. Modified white low density PVC (K64) / filler D50<1 micron showed an increase in strain by 40% after aging. The strength of both white modified PVCs increased slightly, while the strength of unmodified crystal PVC decreased by 15%.
aging; greenhouses construction; pipes; PVC-U; tensile properties; weathering chamber
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