Virgin polymers

Most off-quahty or scrap polypropylene fibers may be repeUetized and blended in small percentages with virgin polymer to produce first-grade spunbonded fabrics. The economics are of great importance in a process where high yields are required in order to be competitive. Some manufacturing equipment direcdy recycles edge-trim back into the extmder where it is blended back into the polymer melt (see Fibers, olefin). 

Until the 1960s, reclaimed mbber was an important raw material in molded and extmded mbber products, eg, tires, mbber mats, and hard mbber battery cases. With the advent of vinyl, other plastics, and less expensive oil-extended synthetic polymers, reclaimed mbber sales stabilized and decreased. In 1973, the oil embargo and rising energy costs increased costs of the energy-intensive mbber reclaiming process to the point where they matched virgin polymer costs. Increased radial tire production required crack resistance that could not be provided by reclaimed mbber compounds (46). 

The principal benefit of using red aim is its lower cost compared to virgin mbbers. Reclaim typicaUy seUs for 20—30% of the cost of its none-reclaimed counterparts. Reclaimed mbber also imparts some desirable improvements in processing it has much lower nerve than virgin polymers. As a result, compounds containing reclaim have much lower die sweU and extmsion rates. It also increases calender rates and improves flow and mold filling. 

Variation of apparent viscosity with the blend ratio for both preblends and preheated blends is shown in Fig. 1. Comparing preblends and preheated, the viscosity of preheated 50 50(NBR-Hypalon) blends becomes maximum, whereas the prebends show a continuous decrease in viscosity from 100% Hypalon to 100% NBR in all shear rates studied. This decrease is explained by the difference in viscosity between two virgin polymers. Preheating of the blends may result in interchain cross-linking and it seems to be maximum at a 50 50 ratio. 

Identifies a plastics with Nothing Else Added To. It is a true virgin polymer since it does not contain additives, fillers, etc. These are very rarely used. 

Polymer layered-silicate day nano-composites (PLCN) attracted lately major interests into the industry and academic fields, since they usually show improved properties with comparison by virgin polymers or their conventional micro and macro-composites. Improvements induded increase in strength, heat resistance (Giannelis, 1998), flammability (Gilman, 2000) and a decrease in gas permeability (Xu et ah, 2001) as well as an increase in biodegradability (Sinha et al., 2002). 

The unsaturated nature of the volatiles generated during decomposition of the complexes, compared to the monomeric species released by the virgin polymer, probably... 

Figure 5.22 Scattering in the degree of polycondensation of the PET product, as a result of variations in the particle size and intrinsic viscosity in the virgin polymer s/mp, standard deviation of the particle mass [12b]. From Weger, F., Solid-state postcondensation of polyesters and polyamides, presentation given at the FrankI and Thomas Polymer Seminar, June 16,1994, Greenville, SC, USA, and reproduced with permission of EMS Inventa-Fischer, GmbH Co. KG...

The BFS container is formed as an integral part of the process from medical-grade virgin polymer granules. A recent study of the lethality of the extrusion process chal-... 

Thermalageing at 80°C. The remarkable efficiency of EPDM (POLY) grafted with TP A can be seen on figure 8. Fig. 8a shows that the stabilization with 10 % w/w of EPDM-TPA in the crude elastomer. The effect of vulcanization is reported in fig. 8b, in this time scale the increase of stability is only seen on the virgin polymer. 

The thermophysical properties, such as glass transition, specific heat, melting point, and the crystallization temperature of virgin polymers are by-and-large available in the literature. However, the thermal conductivity or diffusivity, especially in the molten state, is not readily available, and values reported may differ due to experimental difficulties. The density of the polymer, or more generally, the pressure-volume-temperature (PVT) diagram, is also not readily available and the data are not easily convertible to simple analytical form. Thus, simplification or approximations have to be made to obtain a solution to the problem at hand. 

We can now compare these calculated values with test results. Technical brochures issued by raw material manufacturers supply an abundance of data on their products, also on the tensile moduli of the virgin polymers and on those containing a certain weight fraction of glass fibres. Combination of these data for a number of polymers (POM, PPE/PS, PC, PBTP, PET, PA-6) results in Figure 9.16. We can read from this... 

Polymer of Virgin Polymer Change in Presence of Clay HRR (%)... 

Once the plastic has been separated into its various types, it can be recycled by reprocessing. More commonly, some recycled polymer is added to virgin polymer, although this may limit the application of the resulting material. For example, poly(vinyl chloride) containing 25% recycled resin is available, but only for applications in which it does not come into contact with food. 

H polymers that when recycled would sell for more than virgin polymer... 

There are different types of plastics that are usually identified by their composition and/or performance. As an example there are virgin plastics. They are plastic materials that have not been subjected to any fabricating process. NEAT polymers identify plastics with Nothing Else Added To. They are true virgin polymers since they do not contain additives, fillers, etc. They are very rarely used. Plastic materials to be processed are in the form of pellets, granules, flakes, powders, flocks, liquids, etc. Of the 35,000 types available worldwide there are about 200 basic types or families that are commercially recognized with less than 20 that are popularly used. Examples of these plastics are shown in Table 1.1. 

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