Virginity

The greatest concern with PVC is as a contaminant in other polymers being recycled, particularly PET. Approximately 12 million pounds of PVC was recycled in 1993, about half from packagiag (25). AppHcations for recycled PVC iaclude as an inner layer sandwiched between two virgin PVC layers in pipe and sheet for bHster packagiag and other packagiag appHcations. 

These lower prices make it more difficult for recycled plastics to compete with virgin resins in the absence of legislation mandating plastics recycling. 

Scrap and Recycle. Acetal resins can be processed with very Htde waste. Spmes, mimers, and out-of-tolerance parts can, in general, be ground and the resins reused. Up to about 25% of regrind can usually be safely recycled into virgin resin. However, the amount of regrind that can be used in a particular circumstance varies. The appropriate Hterature from the suppHer should be consulted. 

About half of the wodd production comes from methanol carbonylation and about one-third from acetaldehyde oxidation. Another tenth of the wodd capacity can be attributed to butane—naphtha Hquid-phase oxidation. Appreciable quantities of acetic acid are recovered from reactions involving peracetic acid. Precise statistics on acetic acid production are compHcated by recycling of acid from cellulose acetate and poly(vinyl alcohol) production. Acetic acid that is by-product from peracetic acid [79-21-0] is normally designated as virgin acid, yet acid from hydrolysis of cellulose acetate or poly(vinyl acetate) is designated recycle acid. Indeterrninate quantities of acetic acid are coproduced with acetic anhydride from coal-based carbon monoxide and unknown amounts are bartered or exchanged between corporations as a device to lessen transport costs. 

W. Virgin ski. Paper presented at the 46th Annual Technical Conference of the Society of Plastics Engineers, May 1988, p. 205. 

Fertilizer Use. The worldwide use of fertilizers has an important, positive effect on the environment. Conservative estimates (112) iadicate that about 30% of world food production is direcdy attributable to fertilizer use. Without fertilizer, therefore, at least 30% mote virgin land would have to be devoted to agriculture, and 30% more labor and other resources would have to be expended. Even more serious would be the effects of land tillage and cropping without nutrient replenishment. Past experience has shown that, under such a condition, crop yields progressively decrease, the land eventually becomes barren, and forces of wiad and water erosion prevail. 

The process can be used to recover scrap or low quaUty resins by using them as the core layer, and using outer layers of virgin resins designed for the specific functional needs of the product such as sHp or gloss and appearance. The inner core may be a foamed resin with surface layers of supedor finish resins. Coextmded films often eliminate the need for cosdy lamination processes. 

Melting and recrystallization behavior of virgin PTEE has been studied by dsc (64). A quantitative relationship was found between and the heat of crystallization (A/T) in the molecular weight range of 5.2 x 10 to 4.5 X 1 0, where is heat of crystallization in J/g, which is independent of cooling... 

The melting point of commercial Teflon PEA is 305°C, ie, between those of PTEE and EEP. Second-order transitions are at —100, —30, and 90°C, as determined by a torsion pendulum (21). The crystallinity of the virgin resin is 65—75%. Specific gravity and crystallinity increase as the cooling rate is reduced. An ice-quenched sample with 48% crystallinity has a specific gravity of 2.123, whereas the press-cooled sample has a crystallinity of 58% and a specific gravity of 2.157. 

Several studies estimate the potential of available virgin and waste biomass as energy resources (Table 4) (10). In Table 4, the projected potential of the recoverable materials is about 25% of the theoretical maximum woody biomass is about 70% of the total recoverable potential. These estimates of biomass energy potential are based on existing, sustainable biomass production and do not iaclude new, dedicated biomass energy plantations that might be developed. 

Another factor is the potential economic benefit that may be realized due to possible future environmental regulations from utilizing both waste and virgin biomass as energy resources. Carbon taxes imposed on the use of fossil fuels in the United States to help reduce undesirable automobile and power plant emissions to the atmosphere would provide additional economic incentives to stimulate development of new biomass energy systems. Certain tax credits and subsidies are already available for commercial use of specific types of biomass energy systems (93). 

Isomerization. Isomerization is a catalytic process which converts normal paraffins to isoparaffins. The feed is usually light virgin naphtha and the catalyst platinum on an alumina or zeoflte base. Octanes may be increased by over 30 numbers when normal pentane and normal hexane are isomerized. Another beneficial reaction that occurs is that any benzene in the feed is converted to cyclohexane. Although isomerization produces high quahty blendstocks, it is also used to produce feeds for alkylation and etherification processes. Normal butane, which is generally in excess in the refinery slate because of RVP concerns, can be isomerized and then converted to alkylate or to methyl tert-huty ether (MTBE) with a small increase in octane and a large decrease in RVP. 

Used oil disposal trends include waste minimisation such as by reclaiming used fluid on site, as well as recycling of mineral oil lubricants instead of disposing by incineration. The recycling effort involves a system where spent mineral oils are collected then shipped to specialty refineries where the materials are distilled, hydrofinished, and re-refined into fresh base stocks. These re-refined materials are virtually identical to virgin feedstocks. 

Solvents. Common terminologies used interchangeably are solvents, diluents, reducers, and thinners (Table 2). Technically, solvents are materials that completely dissolve resins in the ink vehicle. Diluents are Hquids that may not completely dissolve the resin by itself. Solvents can also be thinners, but most often thinners are blends of solvents and diluents. Reducer is another name for thinner, referring to the solvent blends used to reduce the viscosity of a virgin ink on the press to miming viscosity. 

Rock wool, frequently referred to as mineral fiber, is made from non virgin siUceous materials and is formed in a similar manner to that of fiber glass. Refractory fibers (qv), also formed in a similar manner, are available for high temperature appHcations. 

Regulations generally prohibit disposal of lubricants in streams, chemical dumps, or other environmental channels. Over half of disposed lubricants are burned as fuel, usually mixed with virgin residual and distillate fuels (77). 

The permeabiHty = B jH is important information for soft magnetic materials. The most often quoted values ate the initial permeabiHty and the maximum permeabiHty ]1. These correspond to the initial and maximum slopes of the virgin magnetization curve, respectively (Fig. 1). Because the value of at S/H = 0 needs to be extrapolated from measurements at finite H, the value often is quoted ia commercial catalogues at specific B or H The quoted values usually are relative to the free-space value p.Q. 

The U.S. Defense Logistics Agency (DLA), which maintains the U.S. National Defense Stockpile (NDS), sold 267 t of stockpiled mercury in 1992 (14). The DLA also sold 103 t of secondary mercury from the Department of Energy (DOE) stocks at Oak Ridge, Teimessee. The DLA accepts bids for prime virgin mercury on a daily basis, and for secondary mercury once a month. Inventories on December 31, 1992 were 4766 t of mercury in the NDS and 121 t of DOE mercury (14). The goal for both is zero. 

Trends ia staple fiber shipments to nonwoven producers are illustrated ia Figure 1 and represent nearly 20% of all U.S. shipments of these fibers. Usage of polyester staple consumed ia fiberfiU are not iacluded ia these data. In 1992, some 182,000 t of virgin staple polyester were consumed ia this apphcation. 

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). 

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