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Definitions

FAQ

FOR THOSE WHO WANT TO KNOW MORE ABOUT DEGRADABLE & BIO-COMPOSTABLE “PLASTIC”

 

As supplied by TTD International Pty Ltd – Australia manufactured by Willow Ridge (USA) for exclusive distribution by “TODI”P&T Todorov Co. in Poland

The term “Plastic”
The term "plastic", as used throughout the text (this presentation) is to be understood to mean a synthetic or semi-synthetic thermoplastic polymer excluding rubber. Thermoplastic polymers are capable of flowing under heat and pressure and they can be melded. Plastics are composed of condensation or addition polymers and may contain other substances to improve performance or economics. As a raw material, plastics are often in the form of pellets of thermoplastic polymer that are heated and extruded for the manufacture of packaging, films, articles and the like.

“TODI” Environmental Degradable & Bio-Compostable Plastics
“TODI” P&T Todorow Co. evolved from the environmental concerns related to current massive use of plastics based exclusively on petroleum sources [1]. This led to the believe, shared by the company founders, that bio-based and biodegradable plastics should be adopted as the basis for an environmentally sensible and preferable sustainable alternative to the petroleum-based, regular plastics – polymer materials, which originally have been designed to resist degradation. The challenge was to design polymers that have the necessary functionality during use, but disintegrate after use and the breakdown products not be toxic or persist in the environment, and should be completely assimilated and metabolized (as food) by soil microorganisms – preferably in a defined time frame.

There are three commonly-used terms describing degradable plastics and/or bioplastics:
degradable,
biodegradable, and
compostable.


The above terms are often misinterpreted and products are incorrectly named and labeled as far as the understanding of the way they degrade after being disposed off with the waste.

Degradable plastics This is the most general term. It includes both, plastics that degrade by physical or biological factors (sunlight or heat, or microbial action). Most so-called oxo-degradable or photo-degradable or photo-oxo-degradable plastics (i.e.: degradation accelerated by photo [UV-sensitizing] additives and/or oxidative catalysts at elevated temperatures), can cause environmental problems, mainly due to small fragments in the process of uncontrolled degradation, may pollute compost, landfill or marine environment. Undegraded hydrophobic fragments with high surface areas can migrate into the water table and soil where they can attract and hold hydrophobic highly toxic elements like PCB and DDT up to one million times background levels – effectively functioning as a toxic chemicals transport system in the environment.

Biodegradable Plastics Biodegradable Plastics are plastics that are completely assimilated (utilized) by the microorganisms present in the disposal system, as food for their energy (enter into microbial food chain) in more than 180 days. This complete microbial assimilation/utilization is measured by the complete conversion of the carbon of the test plastic to CO2 during the microbial process taking place inside the cell.

Compostable Plastics In addition to being biodegradable by microorganisms, to call a plastic “compostable”, a time factor for complete degradation is imposed and regulated by appropriate internationally-accepted standards such as ASTM 6400 (Specification for Compostable Plastics), ASTM D6868 (Biodegradable Papercoatings1) or EN 13432 (Compostable Packaging). These materials will biodegrade in an industrial composting environment in less than 180 days. Industrial compost environment means a defined temperature of about 60°C; a defined humidity and microorganisms must be present. Compostable plastics as per this definition do not leave fragments, which persist longer than approx. 12 weeks in the residue; they do not contain heavy metals or toxins and will support plant life.

Terms as presented above and used throughout this document has been adopted by the “TODI” P&T Todorov Co. after the latest internationally-promoted and adopted terminology summarized in Bioplastic Magazine (Vol.1; 02/2006; p. 34-5) referenced to work on principles and concepts of Bio-based and Biodegradable Polymer Materials by internationally-acclaimed scientists in the field: - Professor Ramani Narayan, Department of Chemical Engineering and Material Science, Michigan State University, USA, - Professor Joseph Greene, Department of Mechanical Engineering Mechatronic, Engineering and Manufacturing Technology, California State University, Chico, California, USA, and - Joeran Reske, BioPlastics and Compostable Packaging, ISD INTERSEROH Dienstleistungs GmbH, Cologne, Germany.

BIO-COMPOSTIBILITY “TODI” bio-compostable plastics – Generation G-1 (Photo-Oxo-degradable), G-2 (bio-degradable) and G-3 (compostable), all degrade under commercial composting conditions within the time limit imposed by commercial composting standards. Composting “TODI” biodegradable plastic waste along with other „organic“ compostable materials like paper, food, agricultural wastes, can generate much-needed carbon-rich compost (humic material) particularly on poor and nutrient-depleted soils as commonly exist in majority of temperate and arid sub- and tropical region of Australia. Compost amended soil has beneficial effects by increasing organic carbon, increasing water and nutrient retention, reducing chemical inputs, and suppressing plant disease – thus maintaining the sustainability of the agriculture system.

Photo-Oxo-Degrading Additive (G-1): What is it? How doe’s it work? Depending on the product and its degradation characteristics, an amount of 1% to 5% (by weight) of “TODI” G-1 additive (photo-oxidative degrading additive) is blended with regular thermoplastic polymers (plastics).

The photo-oxidative degrading additive is particularly suitable for blending with polyolefin-based thermoplastic polymers, such as polyethylene, polypropylene or polystyrene, and blends thereof and copolymers thereof.

The photoactive degradant is selected from the group consisting of: an unsaturated fatty acid composition containing a metal ion, such as Co, Fe, Mg, Zn, Ce; metallic oxides, such as FeO, Fe2O3, ZnO, TiO; and inorganic salts, such as FeCl3 , CuCl2, CoCl2.

The oxidation catalysing additive is selected from the group consisting of: a copolymer of ethylene and carbon monoxide; and a vinyl ketone copolymer. The carbonyl group (CO) content may be from about 1% up to about 8% in the polymer. The degradation time of the copolymer of ethylene and carbon monoxide or the vinyl ketone copolymer can be controlled (increased or decreased) by controlling the carbonyl group content of the copolymer.

G-1 additive and regular plastics are then used to form polymer blend composition which after processing provides a wide range of degradable plastic products and articles.

The photo-oxidative degrading additive triggers degradation of the thermoplastic polymer structure to form particles of degraded plastic which are then able to be subjected to decomposition by microbial activity in a composting process.

G-1 degradable “TODI” plastic products obtained from the use of G-1 Photo-oxo-degradable additive will begin to degrade after a predetermined time period – approximately 6-9 months to 2-3 years.

Plasticized Starch-based Resins – G-2 and G-3 “TODI” G-2 (70-75% plastic replaced by plasticized starch) and G-3 (100% non-plastic) resins are used to make biodegradable and completely biologically-degradable products. Most common current use is in production of film for shopping and garbage bags or in injection moulding of biodegradable utensils and kitchenware. As an example - biodegradable film consists of poly caprolactone EAA, ternary composite plasticizing agent system of glycerol, EVA soluble agent and polyester polyol cold-resistant agent, and reinforcing agent. All these components co-participate in physico-chemical modification of the resultant blend, which after co-blending process is used to make granules for use in biodegradable film production. In an alternative custom-prepared G-3 production run, constituents may comprise oxidized and dextrinized starch-polyepsilon-caprolactone-D, HNN' double bond fatty amide, glycerine, polyesterpolyalcohol cold resisting agent and composite plasticiser, cross linking agent, and modifier.



IN-DEPTH DESCRIPTION OF “TODI” DEGRADABLE & BIODEGRADABLE PRODUCTS: “TODI” BIO-COMPOSTABLE ADDITIVES AND RESINS.

Degradation – Bio-degradation Dynamics: The “TODI” photo-oxidative (Photo-Oxo) G-1 degrading and biodegrading additive is used in the formulation of polymer blend compositions for further manufacturing of specific degradable plastic products including, but not limited to: film, overwrap, shopping bags, waste and bin liner bags, composting bags, mulch film, silage wrap, landfill covers, packaging, oxygen or water barriers, bait bags, nappy backing sheet, cling wrap, personal care products, bottles, containers, planter boxes, food service cups, cutlery, trays, and straws, loose fill foam, and the like. The polymer blend compositions may be particularly useful for manufacturing degradable plastic products that may end up as compostable waste (e.g. garbage bags) or for products which come into contact with the soil and are intended to disintegrate after a desired time (e.g. agricultural films)..

The photo-oxidative degrading additive allows for the formulation of degradable plastic products having a pre-determined time for triggering the degradation process. Specifically, inclusion of the additive composition in to polymer blend compositions for the manufacture of degradable plastic products allows for predetermined time and environmental condition dependent physico-chemical degradation of the plastic. The physico-chemical degradation is then followed by biological degradation of the degraded plastic during composting under aerobic conditions into CO2 and H2O as end products, or under anaerobic conditions into CH4 and H2O as end products.

Each of the processes in this two step process of physico-chemical degradation and biological degradation can be carried out separately or simultaneously. Typically, the physico-chemical degradation will be triggered first and the biological degradation process will follow.

The photoactive degradant and the oxidation catalysing additive initiate and maintain the physico-chemical degradation. Specifically, the thermoplastic polymer degrades in the presence of a required dosage of UV radiation (sunlight) and heat (in the presence of oxygen) to a brittle degraded plastic material which is broken down into fragments (often by the mechanical actions in a municipal solid waste composting process). The molecular weight of the plastic fragments decreases quickly and continuously such that the low molecular weight plastic fragments can ultimately be biodegraded in the presence of microorganisms.

Under the action of ultraviolet radiation (typically provided by sunlight) or heat or under composting conditions, free radicals such as hydroxyl radicals are formed due to the presence of the photoactive additive and the auto-oxidation catalysing additive, and these can react with the polymers, forming other free radicals. These free polymer radicals are extremely reactive and can, inter alia, react further with oxygen or with other polymer chains. The polymer chains are thus split and small chains are formed. During this process, the photoactive degradant acts both as an initiator and as a reaction promoter, whereas the oxidation catalysing additive acts as a reaction promoter and especially as a chain splitter. This process repeats itself as long as the polymer is exposed to the ultraviolet radiation or heat. In this phase, the plastic materials become brittle and fragile and disintegrate into small particles of a few mm2 up to few cm2.

In the second stage, particles of the degraded plastic that are formed as a result of the physico-chemical degradation process are decomposed in the presence of bacteria, fungi and/or enzymes (i.e. microorganisms), such as occur under composting conditions or in contact with the soil. Due to the disintegration into small particles, the area of the polymer subject to attack by the microorganisms is enlarged several times. Depending on the prevailing conditions, the degradation processes of the first stage can still continue, leading to even shorter oxygen-containing polymer chains which, due to the close contact with the microorganisms, are in turn partially degraded further. In this way, complete biodegradation at the end of the second stage can be achieved. In general, this takes place, for example, under composting conditions that are typically used in municipal waste depots.

Plastic products made from the polymer blend composition which are placed in soil or sea water will biodegrade at variable rates. The biodegradation rate depends on conditions such as moisture level (soil), air (oxygen) concentration, temperature, presence of microorganisms, etc. The presence of ultraviolet radiation in the sunlight, light intensity and temperature will also influence – speed-up the degradation rate.

References: [1] Ramani Narayan, Michigan State University, Biobased & Biodegradable Polymer Materials: Rationale, Drivers, and Technology Exemplars, Presented at the National American Chemical Society, Division of Polymer Chemistry meeting, San Diego (2005); ACS Symposium Ser (An American Chemical Society Publication) 939 June 2006 [2] Joseph Greene, California State University, Biodegradation of Compostable Plastics in Green Yard-Waste Compost Environment, Presented at the International Degradable Plastics Symposium, BioEnvironmental Polymer Society (BEPS), June 17, 2006, Chicago, USA [3] Joeran Reske, Beauty of bioplastics, Waste Management World, 02/03/05, www.earthscan.co.uk [4] From Algalita Marine Research Foundation – www.algalita.org/pelagic_plastic.html [5] Y. Mato, T. Isobe, H. Takada, H. Kahnehiro, C. Ohtake, and T. Kaminuma, Environ. Sci. Technol. 2001, 35, 318-324 [6] Ramani Narayan, Biobased and Biodegradable Polymer Materials: Principles, Concepts, and Technology Exemplars; World Polymer Congress, Macro 2006, Brazil.


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