Recycling mechanical

Although PVC is second only to polyethene in terms of polymer production volumes, recycling is not widespread this is attributable to the long-term nature of its major applications in the construction industry, e.g. pipes and window frames. A potentially valuable source of PVC in municipal waste is the water bottle (especially in areas of high bottled water consumption like France). PVC has found widespread use in this application since it does not taint the water. 

Most PVC is recycled via a co-extrusion process in which it becomes the inner layer of sewerage pipes and window Irames, the outer layer being virgin PVC to comply with building regulations. To meet the requirements for the extrusion process it is important to remove all trace amounts of solid contaminants, hence prior to extrusion the melt is usually filtered. Further stabilizers and HCl scavengers are usually also added to prevent polymer degradation. 

Production of polyester fibers using cleaned bottled flakes as raw material consumes approximately 80 % less energy, and emits 70 % less COj and 40 % less water than the production from petroleum. PET bottles are cut into small pieces, and then cleaned in a hot water process to remove dirt, then sorted and extruded to polyester fibers. Mechanically recycled PET is widely used on consumer products such as carpets, T-shirts, underwear, fleece and others. During its recycling by extrusion, PET can undergo structural changes. Chain scission or crosslink could occur after several 

If material is continuously recirculated within the same product line, small fractions in the material will undergo several reprocessing steps. If recyclate content is small, typically a couple of per cent, this proportion will rapidly decrease. For smaller products, where runners may have the same volume as the product itself, however, significant multiple-processing degradation might occur and may result in premature degradation of a product. 

Within the field of engineering thermoplastics, in-plant recycling has only recently been adopted due to stringent performance specifications. There are no general guidelines on maximum regrind content. Feasible levels depend on the application requirements and on material characteristics. 

Extrusion with melt filtration can then be used as the ultimate way of purifying the material. Since each extrusion step exposes the material to thermomechanical cycles likely to further degrade the material, the number of extrusion steps should be kept to a minimum. For the final extrusion compounding, additives can be used to maintain or improve selected material properties, depending upon the composition and degree of degradation of the material. 

A significant fraction of plastics and products cannot be identified and recovered in a cost-effective way as individual polymers. This includes  

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Mechanical pulping Mechanical recycling Mechanism Mechanisms Mechanisms nucleation... 

Mechanical properties. See also Dynamic mechanical analysis (DMA) of polyamides, 138 of polyester LCPs, 52 of polyurethanes, 242-244 of semicrystalline aromatic-aliphatic polyesters, 45 Mechanical recycling, 208 Medical applications, for polyurethanes, 207... 

In Denmark, the discussion on PVC waste is probably one of the most tense in the EU. Denmark was one of the first countries to have a covenant aiming to avoid the landfilling of PVC from building waste applications. Whereas for waste flows like pipes and window frames mechanical recycling is a good option, the situation is a bit more difficult for PVC isolation from cables. The NKT process was initially developed... 

MSWIs (several flue gas cleaning options) Mechanical recycling ... 

Furthermore, Solvay have developed a process called Vinyloop , that is an intermediate between chemical and mechanical recycling and will also be discussed here. 

As indicated, this process is defined as mechanical recycling, since the PVC polymer is not broken down into its monomers. Yet, a main difference with classical mechanical recycling is that in the latter the full PVC formulation is kept intact. Here the components that make up the full formulation are separated. This results in the important advantage that the Vinyloop process can deal with rather complicated formulations. According to Solvay the regenerated PVC is comparable in quality to the primary product. 

The input of the process is a separately collected PVC fraction. The quality has to be about similar as for PVC bound for mechanical recycling. The pilot scale tests... 

Netherlands (high ground water level, soft soil), a price of some 50 per tonne is enough to realise a controlled landfill (including aftercare systems). The gate fee of mechanical recycling processes depends very much on the type of plastic and type of mechanical recycling and cannot be specified here. 

Finally, other relevant treatment options for plastics waste include landfill and mechanical recycling. Since these options (unlike Vinyloop and cement kiln incineration) are not even similar to feedstock recycling we discuss them here only very briefly. Mechanical recycling of plastics (be it PVC or other plastics), needs dedicated collection of the plastic waste in question. This is only possible for selected plastic flows (high volumes, recognisable products, products consisting mainly of one plastic). Landfill can accept plastic waste in any waste context (pure plastic type, MPW, mixed materials). I will only address the costs of these alternative technologies. 

Mechanical recycling Mono waste flow Some 200+, much lower for cables Operational Recovered PE or PP N/A N/A Highly product specific... 

Mechanical recycling uses MPW as a replacement for primary plastic resin. 

Separate collection of plastics, sorting, cleaning and mechanical recycling. 

This article presents details of the gloomy picture of the environmental impacts associated with PVC waste which has been painted by four PVC waste management studies carried out for the European Commission. The studies cover mechanical recycling, feedstock recycling, behaviour in landfill, and the influence of PVC on incinerator flue gas cleaning residues. 

Post-consumer plastic waste recycling is discussed with special reference to feedstock recycling, the advantages it has over mechanical recycling, and the techniques involved. Chemolysis and thermolysis are explained, and... 

Mechanical recycling, feedstock recycling and thermal energy recovery are all valid methods of recycling plastics. This is the conclusion reached by an ecobalance study coordinated by the TUV Rheinland. According to this study, a mixture of all three recycling methods provides... 

Recycling of glass fibre-reinforced plastics is reviewed, with special emphasis on remelting of thermoplastic composites, mechanical recycling of thermoset composites, depolymerisation and dissolution of thermosets and thermoplastics, closed loop recycling of glass, and the use of glass as a mechanical compatibiliser. 32 refs. 

This paper explores the use of plastics in cars to make them more environmentally friendly. It lists major environmental issues. It then discusses in detail the positive role of plastics during the lifetime of a car (more plastics means less fuel consumption), the fact that automotive plastic parts are user-friendly and safe, the current and future uses of plastics in cars, recovery options for plastics in end-of-life vehicles, mechanical recycling (which is the best recovery option for many large automotive parts), energy recovery (the solution for small plastic parts), and feedstock (or chemical) recycling. Lastly, the way forward is considered. 

Davos, 14th-18th March 1994, paper 69. 8(13) PLASTICS IN AGRICULTURAL APPLICATIONS MECHANICAL RECYCLING VS ENERGY RECOVERY Fernandez A P ANAIP... 

This paper analyses the difficulties of the two traditional plastics waste recovery routes, energy recovery and mechanical recycling, and goes on to introduce a third... 

This article provides brief information from a study carried out in the Netherlands, which revealed that combustion with energy recovery is the most economical way of processing waste plastics, whilst mechanical recycling is the most environmentally attractive option. 

A new study carried out by Dow Europe and published by APME indicates that both mechanical recycling and energy recovery have a vital role in ensuring the most environmentally efficient disposal for plastic bottles. The survey carried out by Dow uses the example of an HD PE bottle. Main conclusions of the report are indicated. 

With reference to the latest UK government s attempts to tackle the problem of the disposal and/or recycling of packaging waste, comments are reported from Cameron McLatchie, chief executive of British Polythene Industries. He calls for a landfill levy and increased use of incineration with energy recovery. According to recent studies, the capacity for mechanical recycling is presently insufficient. Statistics relating to waste production are included and the case for incineration in the UK is propounded. 

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