D Standard Practice for Outdoor Weathering of Plastics outdoor weathering~ ADD TO CART. 5, $ Standard + Redline PDF Bundle. D - 99 Standard Practice for Outdoor Weathering of Plastics, exposure, natural weathering, outdoor weathering, plast, Format, Pages, Price. PDF. astm d 塑料的室外风化_专业资料。美标. Scope This practice is intended to cover procedures for the exposure of plastic materials to weather. Exposures in several locations Annual Book of ASTM Standards, Vol
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Test Sites 8. Climatological variations within these areas may include those represented by desert, seashore salt air , industrial locations, tropical, and subtropical regions, plus areas exhibiting a wide range in solar radiant energy.
The area beneath and in the vicinity of the weathering racks should be typical of the ground cover in that climatological area. In desert areas in which sand is the prevailing ground cover, coarse gravel is recommended to prevent abrasion and signi? The ground cover should be low-cut grass in most temperate, tropical, and subtropical areas. NOTE 6—Sand as a ground cover may be desirable where the abrasive effects of exposure to wind-blown sand is a part of the desired exposure.
Exposure Stages 9. The exposure stages must be regarded as providing only a general indication of the degree of exposure, and the results should always be considered in terms of characteristics of the exposure site as well. NOTE 8—The results for exposure stages of less than one year will depend on the season of the year in which the exposure was made. For instance, summer exposures are generally more severe than winter exposures.
Seasonal effects are averaged in exposures of several years. An inherent limitation in solar-radiation measurements is that they do not re?
This is the recommended method for determining exposure stages when polymer degradation is being evaluated. Table 1 shows typical UV radiant exposures for 12 months in subtropical and desert climates. NOTE 9—The average UV radiant exposures shown for subtropical and desert climates are based on several years of measurement in these test environments. The actual yearly values may vary widely from Table 1. Report Procedure Specimen marking shall be in accordance with Practice G and shall be such that there is no interference with either the exposure or the subsequent testing.
Preferably, mark both specimen and specimen holder on the side not exposed to weather, as advanced weathering can obscure even deeply scribed marks.
It is convenient to group specimens to be removed from exposure at the same time in one holder. This procedure will vary with materials, but it must be uniform in a series of tests on one material to provide comparative results. Calculate retention of characteristic property according to Practice D when it is reported.
Precision and Bias The degradation processes were studied using blown films having various additives with thicknesses of approximately 20—80 mm. The formulations are explained in Table I. The test was carried out during the summer for 90 days from 3 June to 2 September The weathered films were collected on four occasions, namely at 52, 75, 93, and h. The conditions in the chamber are tabulated in Table IV.
Characterizations Tensile Properties Tensile tests were performed at room temperature to determine the mechanical properties of weath- ered LDPE films on dumbbell-shape tensile bars tensile samples were prepared by an injection molding machine using a Hounsfield tensile test machine.
Displacement was measured from the crosshead position. The stress-strain curves and the mechanical properties, e. For the tensile testing, the sample was held between two clamps. The upper clamp was connected to a crosshead that moves upwards at a preprogrammed rate to apply tension to the sample. The resistive force between the apparatus and the tensioned sample was measured using a load cell. During the tensile test, the crosshead movement and resulting force were logged.
FT-IR analysis was performed only on unexposed, h accel- erated weathering, and 90 days natural weathering samples. Figure 1 shows the tensile stress-strain curve for samples with various additives. The data were taken as the averages of four runs. The presence of antioxidants or UV stabilizers reduces the tensile strength, as shown in Figure 2. Moreover, films containing Anox, Alkanox, and Good-rite antioxidants show higher tensile strength than films having other UV stabilizers or antioxidants.
The tensile strengths of AN However, ANT Figure 3 shows the elastic modulus of LDPE films before weathering. However, two of the stabilized films show significantly higher elastic moduli, sGR It is well known that tensile strength is a good measure to evaluate the stability of films under natural and accelerated weathering conditions. The weathering effect on the mechanical properties of different samples is evident, with a decrease of tensile strength with increase of the weathering period.
It was found that the tensile strength decreases exponentially with weathering time, as shown more clearly in Figure 4. It can be seen how much faster the accelerated test is than the natural test shown in Figure 4, as carried out by Bualek et al. This result suggests that the accel- erated test method is about nine times faster than the natural one in Riyadh June—August, Films with 0.
For the film containing 0. Thus, the usage lives of AN It can also be concluded that the life of LDPE increases with increase in thickness. Good-rite antioxidants were used at different concentrations. This suggests that there is negligible effect of the addition of 2. It can also be concluded the addition of 0.
Thus, the threshold of GR antioxidant that provides the highest stability seems to be approxi- mately 0. The neat LDPE has a smooth surface before exposure; however, it develops many cracks and grooves after weath- ering, as investigated by others as well. The damage extent is readily appar- ent in the neat sample, as compared to samples containing antioxidants. As shown in Figure 5 a after 90 days of weathering, neat LDPE developed a rip around 12 mm in length; the weathered samples containing antioxidants show fewer cracks.
Figure 6 depicts the FT-IR spectra of samples as a function of irradiation time. The same cases can be found in Figure 6 b — d. Therefore, these results indicate that M. Conse- quently, carbonyl index analysis may be an effective tool in analyzing these results. However, GR Salem et al. In short, AN The CI table also shows that GR This suggests that the higher concen- tration provides more effectiveness to the antioxidants in preventing degradation.
However, the disadvantage of higher concentration of antioxidants is the reduction in strength, as discussed previously. From the above results, it can be concluded that there exists no correlation between mechanical properties and carbonyl index.
Such behavior appears to be in good agreement with Salem et al. Outdoor weathering tests of these films during the summer June to September in Riyadh were also conducted. The effects of weathering on tensile proper- ties of different samples were obvious by the exponential reduction in tensile strength with increase in the weathering period.
From the tensile strength data, the increase in LDPE film life can be under- stood. Good-rite at 0. As discussed, the aging criterion of tensile strength has many more effects than elongation at break and elastic modulus.
After exposure, the weathered films containing anti- oxidants exhibit fewer cracks than neat LDPE film. Natural weathering tests create more effects than accelerated tests.
Calculation of the carbonyl index CI shows that 0. CI data also show that higher concentration of the stabilizers increases the effectiveness of antioxidants. However, the disadvantage is in the reduction in strength produced by higher concentration of antioxidants.
From the mechanical and physico-chemical analysis, there is no correlation between mechanical properties and carbonyl index. The study showed that the addition of 0.
Alhamdan, A. Mechanical deterioration of polyethylene greenhouses covering under arid conditions. Ulrich, H. Introduction to Industrial Polymers. Mass per Unit Area.
West Conshohocken, thickness were more affected. Test Method for Index Puncture Resistance were more significant after 30 months. The behavior was characteristic of a ductile for Testing and Materials.
ASTM D Measuring Nominal Thickness of Geotextiles Tear resistance showed some variations for both and Geomembranes. Assessment in tear resistance were verified but these values were not on a PVC geomembrane in a landfill after ten years. Factors in the durability of polymeric samples showed relevant variations but some decrease membrane liners.
In: international conference on occurred at the last period. Interestingly the biggest thickness geomembranes, , Denver, USA. Proceedings… Designing with geosynthetics, 4rd ed. Englewood Cliffs: Prentice Hall Publ. A comprehensive literature variations for the smallest thickness. Florida: a little decrease in the last period. University of Florida, july 12,