Plastic feed form

Results obtained for two mixed plastics are summarized in Table 4. A balance exists between process temperature, plastics feed rate, and product yields (67). For example, lower temperatures increase wax formation due to incomplete depolymerization. Slower feed rates and increased residence times reduce wax formation and increase the yield of Hquids. The data summarized in Table 4 illustrate that the addition of PET to a HDPE PP PS mixture changes the performance of the Conrad process. Compared to the reference HDPE PP PS mixture, increased amounts of soHds ate formed. These are 95% terephthahc acid and 5% mono- and bis-hydroxyethyl esters. At higher temperatures, apparentiy enough water remains to promote decarboxylation. 

The plastic feed may contain chlorine in the form of PVC or PVDC. Preferably, a substantial portion of any chlorine in the feed is removed by the addition of a chlorine scavenger compound to the feed, for example, sodium carbonate or slaked lime (calcium hydroxide) to the feed. It reacts in the pyrolysis zone with the hydrogen chloride to form sodium chloride or calcium chloride which becomes part of the residue at the bottom of the pyrolysis vessel. Preferably, the chlorine content should be removed to less that about 5 ppm. 

Snrue In a mold, the sprue is the main feed channel that connects the mold filling orifice to the runners leading to each cavity gate. The term is also used for for the piece of plastic material formed in the channel. 

Runner n. In an injection or transfer mold, the feed channel, often branched to serve multiple cavities, and usually of semicircular or trapezoidal cross-section, that coimects the sprue with the cavity gates. The term is also used for the plastic piece formed in this channel. 

The screw tip valve mentioned earlier opens when rotation starts, permitting the melt to flow in front of it and force the screw back. In the next step, shown in Fig. 19.35E, the injection assembly moves away from the sprue bushing via the hydraulic cylinder (4). The screw still is charging the front end of the cylinder while moving back in its barrel. While the screw is turning, plastic feed, generally in the form of pellets, drops from the feed hopper... 

Phase inversion does not occur in process A, the viscosity ratio is high, and the resulting dispersion of rabber in the product is poor. In process B, phase inversion takes place after the plastic material melts completely. First, the rubber forms a continuous phase. After the introduction of the 80% plastic feed to the molten rubber, the initial dispersion of the plastic material is governed by piA d RUBBER- The viscosity ratio is between 0.1 and 1, which favors the dispersion of the plastic material into the continuous rubber phase. After PI, the total interfacial area is preserved. Hence, an excellent dispersion of rubber particles in the continuous plastic phase melt is produced in product B. It is important to point out that at this point, coalescence of the dispersed rubber particles will take place. Coalescence is further promoted by the highly unfavorable r RUBEERl piAsnc > 3.5. Methods to prevent coalescence in order to preserve the desired dispersion are required, such as in-situ grafting of a functionalized rubber and the polymer. 

Urea is also used as feed supplement for mminants, where it assists in the utilization of protein. Urea is one of the raw materials for urea—formaldehyde resins. Urea (with ammonia) pyrolyzes at high temperature and pressure to form melamine plastics (see also Cyanamides). Urea is used in the preparation of lysine, an amino acid widely used in poultry feed (see Amino acids Feeds and feed additives, petfoods). It also is used in some pesticides. 

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