Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production ...

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Plastics recycling: challenges and opportunities

https://scholarlypublications.universiteitleiden.nl/access/item%3A2978611/view

Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities.

Responsive polymers in controlled drug delivery

The plastic in microplastics: A review.

Polymer biodegradation: mechanisms and estimation techniques.

A horizontal test method for biodegradation in soil of bio-based and conventional plastics and lubricants

The degenerated shell element is one of the most efficient elements for analysing shell structures. However, it is known to result in rather stiff models when used in thin element applications. The phenomena associated with this behaviour are known as locking phenomena.

This paper analyses the machine locking mechanism developed in thin to very thin Lagrangian and serendipity elements. The machine related locking phenomenon is distinguished from the shear and membrane locking phenomena. A remedy for the pure machine locking problem is developed for the two elements. The proposed remedy is based on the technique of the modified transverse shear modulus. It is also extended to control shear locking. The proposed technique is shown to completely eliminate machine locking. Also, it is shown to effectively alleviate stiffening effects due to the presence of spurious shear strain.

Machine locking of degenerated thin shell elements

The main standard test methods for biodegradation of plastics in soil (ISO 17556, ASTM D5988, NF U52-001 and UNI 11462) determine the rate of biodegradation under normalized conditions. The standard testing procedures are designed to determine the inherent biodegradability of plastics in soil under optimal controlled conditions that may not be necessarily representative of any specific environmental conditions but they ensure repeatability. The normalized conditions defined by the standard test methods differ in several aspects. A comparative analysis is presented. Besides the biodegradation test methods, pass levels and a time frame also need to be defined in order to determine whether bio-based products will biodegrade sufficiently under soil conditions. There is currently no European or international specification that defines criteria for biodegradation of bio-based products in soil. Criteria for biodegradation of materials used in agriculture and horticulture are only defined in standard specifications NF U52-001 and UNI 11462, together with criteria for environmental safety. However, the evaluation of the biodegradation in soil is not obligatory in the French specification. The main requirements for mulching films are: (1) biodegradation at least 90% within 24 months; (2) material shall not contain heavy metal, no ecotoxicological effects. The same requirements have been adopted by the USDA-AMS National Organic Program (NOP) for mulching films allowed for organic crop production. The constraints, gaps, and limitations of existing relevant testing methods and the new developments are identified and analyzed in this chapter. Functional barriers with respect to standards and labeling for soil biodegradable plastics are analyzed.

Standards for Soil Biodegradable Plastics

On the basics of the shear locking problem of C0 isoparametric plate elements

The field performance of experimental biodegradable drip irrigation thin wall and regular pipes was investigated through three sets of full-scale experiments and in the laboratory. These experimental biodegradable drip irrigation systems were produced through the processing of biodegradable under real soil conditions polymers, Mater-Bi and Bioflex. The mechanical behaviour of the biodegradable thin wall pipes during the irrigation period was more unstable when compared to the corresponding behaviour of the rigid pipes. The tensile strength of the Mater-Bi and Bioflex thin wall pipes remained almost constant during the total exposure time, except from the folding areas. During the first 7–23 days of exposure in the field, the thin wall pipes had already lost more than the 50% of their initial elongation at break value due to degradation. However, their hydraulic performance began to decline only after a period of 100–120 days with the simultaneous formation of the first cracks. Likewise, the majority of the series of biodegradable rigid pipes exhibited a remarkable reduction in their elongation at break values in the transverse direction within the first 2 weeks. Despite the significant drop of the elongation at break, all biodegradable rigid pipes generally retained their tensile strength as well as a satisfactory hydraulic performance during almost the whole duration of their exposure. A few premature leakages in some points adjoining the drippers were observed after 8–10 weeks of exposure.

Demetres Briassoulis

Papers

A horizontal test method for biodegradation in soil of bio-based and conventional plastics and lubricants

Machine locking of degenerated thin shell elements

Standards for Soil Biodegradable Plastics

On the basics of the shear locking problem of C0 isoparametric plate elements

Degradation Behaviour and Field Performance of Experimental Biodegradable Drip Irrigation Systems