Recycling and Recyclates

At the end of their useful life, waste polymers enter waste streams as either post-consumer waste or industrial scrap. Households and the distribution industry sector are sources of the former while the latter arises from processing, filling, assembling, installing, and polymerisation. Much of the industrial waste is recycled within the process and the rest is usually sent for reprocessing by a third party. Consequently, little of this material is discarded as waste. The majority of postconsumer plastic waste, however, reaches the environment and hence the emphasis in polymer waste management is on this type of waste stream. 

LDPE is widely used in applications requiring clarity and ease of processing. Its most common use is as film (73%) for sacks, shrink wrap, stretch wrap, and refuse bags. LDPE is the predominant material for telecommunications cables and forms a water vapour resistant seal in the lamination of co-extruded multilayer films. When recycled, LDPE can be used to make most of the products made from virgin LDPE (except for packaging). 

It is known that polyolefinic polymers can be readily thermally decomposed to gaseous and liquid hydrocarbons. The pyrolysis of these kinds of polymers in an inert atmosphere or under vacuum at elevated temperatures gives heavy hydrocarbons as major reaction products. Mainly light paraffins and olefins are obtained during polymer thermolysis at higher temperatures (above 700 °C). In 

Thermochemical processes used to recycle the feedstock from plastic waste are usually those used in the petrochemical industry. These include visbreaking (viscosity reduction or breaking), steam cracking. 

Using the peak property method in order to estimate the pyrolysis kinetics of HDPE, Kim and coworkers found that random scission degradation, which is expected to be a major decomposition mechanism of HDPE, does not follow first-order kinetics rigorously [13]. 

---

Chicago, II., 26th-29th Sept.1995, p.279-86. 43C6 RECYCLING AND RECYCLED CONTENT FOR POLYURETHANE FOAM Hicks D A Hemel C B Kirk A C Stapleton R J Thompson A R... 

Table 1. Material balance in the non-recycling and recycling lemon peel oil recovery systems...

To utilise biodegradable, recyclable and recycled packaging materials. 

Basically, there are two ways of recycling, namely, material recycling and recycling via a chemical reaction, the latter using mostly thermal processes. Of course, these two methods can be further subdivided. There are monographs on the basic aspects of recycling of plastics (116,117). 

Fig. 5 Synaptic vesicle recycling in the synapse. For synaptic vesicle recycling, several endocytic mechanisms appear to co-exist in synaptic nerve terminals. In the case of fast kiss-and-ran exo-cytosis/endocytosis, the fused vesicle does not collapse into the membrane but is retrieved directly by a fast process. The molecular machinery underlying this pathway is unknown. Vesicles that have fully collapsed into the membrane are recycled by clathrin-mediated endocytosis. Clathrin, along with other proteins, is involved in membrane invagination (see figure and text) and leads finally to the formation of a constricted pit. The GTPase dynamin (black ring) mediates membrane scission of the constricted pit. After removal of the clathrin coat, two pathways are possible (direct recycling and recycling via the early endosome). In all cases, before fusion the recycled vesicles have to be loaded with neurotransmitters (NT).

Example A recent industrial eco-design example is the Philips Econova ECO Smart LED TV, with a power consumption of just 56 watts in standard mode, which is 60 % less than conventional LCD TVs. In addition, it consists of recycled and recyclable materials and comprises a solar-powered remote control and a zero power switch. 

Directories of Plastics Recyclers and Recycled Plastic Product Manufacturers... 

FIGURE 8.7 Amounts recycled and recycling rates fa- plastics in U.S. municipal solid waste. ... 

Wisconsin, Oregon, and California have laws related to recyclability and recycled content of rigid plastic containers. In Wisconsin, plastic containers except those for food, beverages, drugs, and cosmetics, are required to contain 10 percent recycled content. The exemptions do not apply if the U.S. FDA has approved the use of recycled content. However, the law allows remanufactured material (regrind and so forth) to be counted as recycled, and it has had little effect. 

Plastics pigmented with aluminum can be recycled and recycled PO may be optically improved by addition of aluminum pigments. Among recent developments Obron Atlantic offers Mastersave an easily dispersed pelletized 80% aluminum pigment concentrate, which usually does not require predispersion. They are available as pastes (a slurry with mineral spirits). The major use of metallic flake pigments is in protective and decorative coatings. 

---