ASTM D7473 Weight Attrition of Plastic Materials in the Marine Environment by Open System Aquarium Incubations.

Introduction

The ASTM D7473 test method determines the weight loss as a function of the time of non-floating plastic materials (including formulation additives). When cultivated in the open, fluctuating conditions are typical of aquatic habitats near the coast and at the bottom of the seas. The aquarium incubation test method enriches representative Indigenous microorganisms in seawater and marine sediment for biodegradation.

Scope

Lubricants that degrade by more than 20% in 28 days are considered inherently biodegradable. Most mineral oil-based lubricants up to ISO VG 320 meet this criterion. However, petroleum-based lubricants are not readily biodegradable because they only naturally degrade by 15-35% in 28 days. The weight loss as a function of time is determined using the ASTM D7473 test method when non-floating plastic materials are incubated under changing, open marine aquarium conditions, which are representative of aquatic environments near the coasts.

Procedure

Preparation Procedure: The process starts by preparing the film, where the mean thickness of the pre-dried film is measured. Then, the film is cut into 0.5 x 0.5-inch pieces and weighed. All of these weights are recorded. The preparation procedure for aquarium inoculation involves the collection of surface sediment from NSW and transporting it to the incubation area of the aquarium. The sediment is kept in dark conditions before use, with enough collected to half-fill the required sections of the incubation containers, thus ensuring there are enough sections for all sample films.

During aquarium incubation, natural seawater is permanently maintained in an aquarium tray. Film samples are placed within plastic boxes with sediment and without sediment, so their position is noted. The covers for the box are nylon screen meshes, bound with rubber bands at each corner; they should be submerged after slowly displacing sediment and filling with seawater in the aquarium tray. The aquarium is kept in darkness by using opaque plastic film or fabric. Data calibration requires monitoring the incoming seawater’s temperature, and samples are checked for degradation over 180 days. Samples are removed in triplicate at specific intervals, rinsed to remove sediments, slime, and salts, and dried to a constant weight at 35–40°C before the final weight is recorded.

Sample Size

The following are the technical specifications of ASTM D7473:

Result

ASTM D7373 Predicting Biodegradability of Lubricants Using a Bio-kinetic Model. A biodegradable substance is broken down into smaller molecules by microbes. This test is intended to predict the amount of lubricating oil that will biodegrade in a specified period, typically 28 days.

Conclusion

ASTM D7473 is the standardized method that uses open-system aquarium incubations to determine the degree of weight loss or attrition plastic materials undergo when exposed to marine environments. This method allows testing of the rate at which plastics degrade under simulated oceanic environments and, hence, helps better understand the impacts on the environment and pollution derived from waste plastics. This aspect is made possible by measuring weight attrition over time in ASTM D7473-12, enabling researchers and manufacturers to compare the resilience of different plastic formulations and, thus, foster the development of more sustainable and environmentally friendly materials for marine applications.

FAQs