Abstract:
This research studied the effects of 4 types of additives, UV-absorber, antioxidant, carbon black, and flame retardant, on UV- stability of glass fiber reinforced epoxy (GRE) pipes prepared by filament winding process using a MTHPA (Methyl Tetrahydrophthalic Anhydride) as a catalyst. The amount of additive used was varied from 0 - 10 %w/w. The central composite design (CDD) was employed to experimentally design the formulation of GRE pipes, in order to practically reduce the total number of experiments from 625 pipes (Full factorial design for 4 factors and 5 levels) to 30 pipes without losing the credibility of the results achieved. The photodegradation of the GRE pipes was performed by an outdoor exposure and simulated condition in Q-UV Lamp. The progress of photodegradation was followed by determining the changes in mechanical properties, physical properties and appearance, and thermal properties as a function of exposure time. The results showed that the GRE pipes No.30 had better mechanical properties than the others over period of exposure time. Similar results were observed in both outdoor and accelerated tests. In addition, it was found that UV exposure could actually improve short-term mechanical properties due to postcuring phenomenon. Under the accelerated condition, it was found that upon increasing the Q-UV exposure time, the physical properties in terms of the density, color, and gloss were decreased. Color changes involved initial fading followed by subsequent increased level of yellowing. The decrease in density and gloss values were attributed to the surface degradation induced by UV-irradiation. As evidenced by SEM micrographs, a substantial degree of cratering and cracking was observed, especially after 10 years of Q-UV exposure. The addition of additives led to an increase in thermal stability and % residue weight. No changes were observed in the Tg of the GRE pipes after long exposure time, indicating that damage is confined to the surface region. The collected mechanical properties data were graphically and statistically analyzed by analysis of Variance (ANOVA). Empirical models describing the responses (properties of interest) over the applicable ranges of additives were developed.