Global Aging and Lifetime Prediction of Polymeric Materials for Solar Thermal Systems – Part 2: Polyamide 66 Glass Fiber Reinforced Absorbers for Integrated Storage Collectors
Abstract
The paper deals with the lifetime estimation of black-pigmented, glass-fiber reinforced polyamide (PA-GF) absorber grades for absorber/storage tanks of pressurized, non-pumped hot water systems at different sites (Athens, Fortaleza, Pretoria). The annual absorber time/temperature distributions were simulated. Global aging data were gathered by exposure of specimens in hot water at elevated temperatures (115 and 135°C) and analytical and mechanical characterization after aging. Lifetime assessment for the absorber/storage-tank material was done by combining the time/temperature loading profiles, extrapolated endurance times from aging tests and assuming cumulative damages. Depending on the chosen aging indicator, glass fiber content and climate zone, the lifetimes varied between 35 and 47 years with lowest values for the hot-and-humid climate zone. The grade with 30 m% glass-fibers exhibited a slightly better long-term performance than the grade with 35 m%.
Keywords
Polypropylene, solar thermal collector, absorber, lifetime