Plasticizers are used to make PVC flexible so it can be used as a geomembrane. Plasticizers can migrate from PVC geomembranes over time because of contact with air, liquid, and/or an absorbent solid material. Plasticizer migration can reduce the flexibility of PVC geomembranes, resulting in brittle behavior. This paper discusses the three mechanisms of plasticizer migration and the factors influencing these mechanisms, such as plasticizer molecular weight and linearity of the plasticizer. Field case histories are used to show how these mechanisms influence plasticizer retention in PVC geomembranes. Finally, it is recommended that a minimum average plasticizer molecular weight of 400 be used to ensure long-term plasticizer retention and adequate field performance of PVC geomembranes. The weighted-average method for calculating the average molecular weight is recommended when two or more plasticizers are used in the PVC geomembrane formulation.
Plasticizers are used to make PVC flexible so it can be used as a geomembrane for containment purposes. Plasticizers can migrate from PVC geomembranes over time because of contact with air, liquid, and an absorbent solid material. Plasticizer migration can reduce the flexibility of PVC geomembranes. This paper discusses the three mechanisms of plasticizer migration and the factors influencing these mechanisms, such as plasticizer molecular weight and linearity of plasticizers. The paper recommends that a minimum average plasticizer molecular weight of 400 be used to ensure long-term plasticizer retention in the field. The weighted-average method for calculating the average molecular weight is recommended when two or more plasticizers are incorporated into the PVC geomembrane.
In 1971, twenty circular aquaculture ponds were constructed for the W. K. Kellogg Biological Research Station in Hickory Corners, Michigan. The 30.5‐m‐diameter research ponds were lined using a 0.51‐mm‐thick fish‐grade PVC geomembrane. Over the years the ponds became congested with dense, persistent stands of cattails, trees, and other vegetation, which required the ponds to be cleared and relined in September 2000 in order to allow the initiation of new experiments. The lack of holes in the exhumed geomembrane suggests that it resisted biological attack from microorganisms and also root penetration. Laboratory testing shows that the tensile behavior of the nearly 30‐year‐old PVC geomembrane is within current specifications for new 0.51‐mm‐thick PVC geomembranes. Test results also indicate that performing laboratory tests at in‐situ moisture conditions provides a better estimate of the field properties of PVC geomembranes than desiccating the material prior to testing, as is required by ASTM Standard Test Methods. J. Vinyl Addit. Technol. 10:168–173, 2004. © 2004 Society of Plastics Engineers.
The authors studied the effect of heat and ultraviolet (UV) exposure as well as natural weathering on the glass transition temperature of PVC roof membranes. The glass transition temperature of the unexposed specimens and those exposed to heat, artificial (UV) and natural weathering obtained from the E' and E" curves, as per ASTM Practice for Dynamic Mechanical Analysis and Thermogravimetry of Roofing and Waterproofing Membrane Material (D 6382) and ASTM Test Method for Plastics: Dynamic Mechanical Properties: In Flexure (Dual Cantilever Beam) (D 5418), range from -48°C to -33°C and from -39°C to -28°C, respectively. The ΔTg values obtained from the E' curve varied between -6°C and 4°C and those from the E" curve varied between -4°C and 9°C. The results indicate that some naturally exposed membranes have similar ΔTgs to some of the artificially aged samples.
The moisture absorption rate (MAR) and moisture desorption rate (MDR) are important for industrial coatings that request optimum tactile feel. One method is to include protein into the surface of the coating. It is important to understand the relationship between protein concentration and MAR-MDR. This research investigats the correlation between the protein content and MAR-MDR by using three types of protein: soy protein, fungal protein and industrial recycled protein (IRP). Except for the MAR result of fungal protein coating, all the other results showed there is none direct linear correlation between protein content and MAR-MDR in the testing ranges.
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