Ps

Other

LDPE/LLDPE 27.4%

HDPE 39.2%

Figure 4.5. Plastics resins in packaging in U.S. municipal solid waste stream, 1998 [1].

HDPE 39.2%

Figure 4.5. Plastics resins in packaging in U.S. municipal solid waste stream, 1998 [1].

and/or multilayer packages containing two or more different polymers are used. Figure 4.5 shows the proportions of major plastics found in packaging in U.S. municipal solid waste in 1998.

4.5.1. High-Density Polyethylene

In 2000, approximately 15,602 million pounds of virgin high-density polyethylene (HDPE) resin were used in the United States and Canada [3]. Packaging film and containers accounted for a major fraction of this use, over 38% if grocery sacks and merchandise bags are included as packaging (Fig. 4.6).

The largest category of HDPE use in packaging, by far, is bottles. For virgin resin, nearly 50% of these bottles were used for food, 6% for motor oil, and the remaining 44% for household and industrial chemicals of various types [3]. Within the food category, the largest fraction is milk and water bottles. In 1998, HDPE milk and water bottles amounted to more than 18% of all plastic containers in the MSW stream. Bottles and containers totaled 31.4% of all HDPE packaging in the MSW stream, and packaging represented over 78% of all HDPE in the MSW stream [1]. HDPE offers reasonable stiffness and strength, excellent moisture barrier, the ability to use pigments to achieve a wide variety of colors, and low cost. Its primary drawback is its lack of transparency and its poor barrier to most gases.

In the United States, recycling of HDPE bottles through curbside collection and dropoff systems is very common. According to the American Plastics Council, more than 20,000 American communities have access to plastics recycling,

Resellers other 3rd p 12.1%

Other blow molding 8.9%

Rotational molding 0.9%

Resellers other 3rd p 12.1%

Other blow molding 8.9%

Rotational molding 0.9%

Pipe and conduit 11.1%

Other injection molding 4.7%

Blow-molded bottles 17.8%

Figure 4.6. Uses of HDPE in United States and Canada, 2000 [3].

Other injection molding 4.7%

Other non-packaging -- film 3.7%

Injection-molded containers 9.7%

Other extrusion 7.7%

Pipe and conduit 11.1%

Blow-molded bottles 17.8%

Figure 4.6. Uses of HDPE in United States and Canada, 2000 [3].

and nearly all major communities include HDPE bottles in their collection programs [4]. Recycling of nonbottle HDPE containers, and of other forms of HDPE packaging, is much less common.

Milk and water bottles are the highest value type of recycled postconsumer HDPE because their lack of pigment permits them to have a wide variety of potential uses. They also have the highest recycling rate of HDPE containers, 31.4% in 1998 in the United States. The overall HDPE packaging recycling rate in 1998 was 10.3% [1]. The HDPE bottle recycling rate was 30.7% in 1998 but fell to 29.7% in 1999. The amount of HDPE bottles recycled in 1998 increased to nearly 750 million pounds but did not increase as fast as production [4].

In Alberta, Canada, a voluntary stewardship program for HDPE milk bottles achieved a provincewide recovery rate of 40%, with 16 communities achieving rates of 70% or more. The program provided a guaranteed floor price to collection organizations along with funds for promotional activities [5].

Recycled HDPE is an important material in manufacturing of certain types of HDPE packaging. Most HDPE bottles for laundry products such as detergent and fabric softener are manufactured with a three-layer structure, containing postconsumer recycled HDPE blended with regrind from the bottle production process in the middle layer. Many motor oil bottles contain a blend of postconsumer recycled plastic with virgin plastic in a single-layer structure. Recycled HDPE from milk bottles is often used in manufacture of merchandise bags.

The U.S. Food and Drug Administration (FDA) has issued a letter of nonobjection for at least one process for use of recycled HDPE in a buried inner layer in packaging for certain types of food products.

4.5.2. Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE)

About 17,565 million pounds of virgin low-density polyethylene and linear low-density polyethylene were used in the United States. and Canada in 2000 [3], primarily in film applications. Packaging film alone represented over 28% of LDPE and LLDPE use, if carryout bags are included (Fig. 4.7). EPA estimates that LDPE/LLDPE bags, sacks, and wraps accounted for 85.6% of all LDPE and LLDPE packaging in the MSW stream in 1998, and that packaging accounted for 50.7% of all LDPE and LLDPE in the MSW stream [1]. LDPE and LLDPE provide excellent flexibility, good strength, moderate transparency, good moisture barrier, and low cost.

Linear low-density polyethylene came into widespread use in packaging, displacing the older LDPE in many applications, because LLDPE's more uniform linear copolymer structure with a narrower molecular weight distribution resulted in improvement in both tensile and tear properties compared to highly branched LDPE. Despite its higher price per pound, this permitted cost savings because of the ability to use much thinner film (downgauge) while maintaining desired performance. Heat seal performance of LLDPE, however, is inferior to LDPE. In applications such as coatings, LDPE is used much more than LLDPE. In a number of film applications, blends of LDPE and LLDPE are used to obtain the best combination of properties. Often, the term LDPE is used generically to refer to LDPE, LLDPE, and blends of the two materials.

Other, including 3rd party 20.0%

Export 21.6%

Rotomolding 3.2%

Blow molding 0.4%

Food packaging film 8.3%

Export 21.6%

Food packaging film 8.3%

Other, including 3rd party 20.0%

Rotomolding 3.2%

Blow molding 0.4%

Non-food packaging film 9.6%

Stretch and shrink wrap 8.7%

Carryout bags 1.8%

Non-packaging film 15.1%

Coating 5.6%

Sheet 0.7%

Injection molding 5.0%

Figure 4.7. Uses of LDPE and LLDPE in the United States and Canada, 2000 [3].

Non-food packaging film 9.6%

Stretch and shrink wrap 8.7%

Carryout bags 1.8%

Non-packaging film 15.1%

Coating 5.6%

Sheet 0.7%

Injection molding 5.0%

Figure 4.7. Uses of LDPE and LLDPE in the United States and Canada, 2000 [3].

The introduction of metallocene catalysts has permitted new variants of LLDPE to be produced, with much improved ability to tailor properties to end-use requirements. LLDPEs that incorporate higher a-olefins as co-monomers have much improved heat seal properties, for instance. These new polymers are likely to further displace LDPE and result in even greater ability to downgauge films in both LDPE and LLDPE applications. These same catalyst systems are likely to also permit source reduction through downgauging in HDPE, PP, and other applications.

Recycling of LDPE and LLDPE is much less common than recycling of HDPE. The EPA reported a recycling rate for LDPE/LLDPE bags, sacks, and wraps of 5.2% in 1998 and an overall LDPE/LLDPE packaging recycling rate of 4.4%. The vast majority of this material was collected from businesses, rather than from individual households, and originated in stretch wrap for pallet loads of goods. Collection of LDPE, LLDPE, and HDPE grocery and merchandise sacks at retail stores used to be fairly common, although it never captured a large portion of the material available. Many retailers have discontinued such programs because of cost and contamination issues. Some drop-off collection is still available for such materials, sometimes through schools or community organizations. Collection of plastic film at curbside is available only in a handful of communities in the United States. In Ontario, Canada, curbside collection of plastic film is common. The Environment and Plastics Industry Council (EPIC) has published a guide to such collection [6].

A major use of recycled LDPE and LLDPE is in the manufacture of trash bags. Some is also used in the manufacture of merchandise bags. A use of growing importance is, mixed with wood fibers, plastic lumber for applications such as window frames.

4.5.3. Polyethylene Terephthalate

Consumption of virgin polyethylene terephthalate (PET) resin in the United States and Canada totaled 5110 million pounds in 2000 [3]. Bottles were by far the largest application (Fig. 4.8). Soft drink bottles continue to be the largest use for PET bottles, but other applications (custom bottles) have been growing at a much faster rate for the past several years. According to EPA estimates, soft drink bottles accounted for 49.4% of all PET packaging in U.S. municipal solid waste in 1998, and 53.2% of all PET containers in municipal solid waste [1].

PET is used in packaging applications where its excellent transparency, stiffness, strength, improved high-temperature performance, and reasonably good barrier properties are sufficient to justify its extra cost compared to HDPE.

According to the EPA, the soft drink bottle recycling rate was 35.4% in 1998, and the overall PET container recycling rate was 23.4% [1]. The American Plastics Council reported a 24.4% recycling rate for PET bottles in 1998, which declined to 22.8% in 1999, continuing a pattern of decline from its high of 50% in 1994. The tonnage of PET bottles recycled has grown during this period but has been outstripped by gains in the amount of PET used.

Like HDPE, PET bottles are collected through most curbside and drop-off recycling programs in the United States. In nine states, PET soft drink bottles

Export 14.1%

Export 14.1%

Figure 4.8. Uses of PET in the United States and Canada, 2000 [3].

are subject to a deposit, usually 5 cents. California has a quasi-deposit system that provides a refund value for the containers. In both California and Maine, the deposit/refund value systems have been extended to non-soft-drink beverages. In most cases, the true deposit systems achieve a recovery rate of over 90%.

In Europe, PET recycling rates in 1999 ranged from 70 to 80% in Sweden and Switzerland, down to less than 5% in the United Kingdom.

The U.S. FDA has issued letters of nonobjection for several processes for incorporation of recycled PET in food packaging. Such approval has been granted for systems using the recycled PET blended with virgin PET in direct contact with food, as well as in a buried inner layer. Often, these processes have used PET bottles collected through deposit systems, which have been shown to yield cleaner materials than curbside bottles. Chemically recycled PET that has been broken down to monomer, purified, and repolymerized has also been approved. Recently, Plastic Technologies, Inc. (PTI) of Bowling Green, Ohio, announced the first commercial production in the world of a plastic bottle made of 100% mechanically reprocessed curbside recycled PET.

During the past several years, Coca-Cola, and more recently Pepsi, have come under attack for failure to use recycled PET in the manufacture of soft drink bottles. While incorporation of up to 25% recycled content is common in a few countries, it was never widespread in the United States and all but disappeared by the late 1990s. Coca-Cola has begun to use small amounts of recycled PET in soft drink bottles and in early 2001 announced a plan to use an average of 10% recycled content in all its PET bottles by 2005.

The movement by brewers to introduce beer in enhanced barrier PET bottles has also spawned controversy. PET recyclers were initially quite concerned about the effect of such containers on their processes and profitability, particularly because many of the bottles are amber in color. Environmental and consumer organizations, and also some legislators, voiced concern as well. Commitment by industry to somewhat modify the design of the bottle label and closure, to buy the amber recycled PET, and to include recycled PET in an inner layer in the containers satisfied most processors, as well as some of the other protestors.

In addition to limited use in beverage bottles, recycled PET packaging is used in nonfood bottles, trays, blisters, strapping, and other packaging applications. It also has a wide variety of nonpackaging uses, especially as fiber.

In many of its packaging applications, PET has replaced glass. Usually this has resulted in large reductions in both the volume and weight of packaging used to deliver products. The savings occur not only in the primary package but also in associated distribution packaging, since goods packaged in PET take up significantly less space than those packaged in glass. Energy savings are also usually substantial.

4.5.4. Polypropylene

Polypropylene (PP) is used in packaging in much smaller amounts than HDPE, LDPE/LLDPE, and PET. Its uses are also more evenly divided between various markets. The EPA estimated PP in packaging in municipal solid waste to be 13.8% in containers, 48.9% bags, sacks, and wraps, and 37.2% "other plastics packaging" [1]. A significant fraction of the latter category is caps. The majority of plastic closures (caps) are made of PP. Polypropylene films are often used for packaging applications where a stiff, highly transparent film is desired. Since it was first introduced, PP has captured nearly all the packaging film markets once held by cellophane. In container markets, PP is also used where its improved high-temperature performance, transparency, and stiffness compared to HDPE are an advantage, such as in applications where containers are hot filled. Clarified grades of PP can provide sufficient transparency to enable PP to compete with PET.

Recycling of PP packaging is much less common than recycling of HDPE, LDPE/LLDPE, and PET, at least in part because there is less of it that can be readily recovered. PP is rarely included in either curbside or drop-off collection programs, and there is little recycling of PP from business sources. All-plastic-bottle collection programs, which exist in a few locations, do include PP bottles. The EPA estimated the 1998 recycling rate for PP packaging as 3.2% [1].

Some PP is collected, often inadvertently, when HDPE or PET bottles are collected and have their PP closures in place. On HDPE bottles in particular, this is problematic since HDPE and PP are not separable in common sink-float or hydrocyclone processes designed to separate heavier-than-water from lighter-than-water materials. Even very small amounts of pigmented PP caps cause discoloration in unpigmented HDPE streams. While PP is more readily tolerated in pigmented HDPE streams, large amounts of PP cause unacceptable decreases in performance of the recycled material. PP contamination of PET is not a major issue since the materials can be readily separated.

Just as there is little recycling of PP packaging, there are few uses in packaging for recycled PP.

4.5.5. Polystyrene

Polystyrene (PS) is used in packaging applications in both foamed and highly transparent nonfoamed (crystal) form. High-impact polystyrene (HIPS) is partially a blend and partially a copolymer, designed to have greatly improved impact strength. PS finds applications in containers, film, and, very importantly, as cushioning material. Foamed PS cushioning is produced in molded and die-cut shapes and in loosefill form. Uses of virgin PS in the United States and Canada are shown in Figure 4.9. In packaging materials in MSW in 1998, 28.6% of PS was in containers, 28.6% in bags, sacks, and wraps, and 42.9% in the "other packaging" category that included cushioning materials.

PS is a stiff, brittle material with relatively poor barrier properties. Crystal PS has excellent transparency. In its foamed form, PS has very good cushioning abilities, as well as insulation properties. Cost is relatively low, especially in molded expanded polystyrene (EPS) and extruded foam PS, where a small amount of mass can yield a large volume. PS is readily shaped by injection molding, extrusion, or thermoforming, in either foamed or unfoamed form.

Recycling of PS in the United States is limited almost exclusively to recycling of cushioning materials. The EPA calculated the recycling rate for PS packaging in 1998 at 4.8%. The Alliance of Foam Packaging Recyclers (AFPR) reported a 9.6% recycling rate for EPS packaging in 1999, up from 9.5% in 1998 [7]. The International EPS Alliance Task Force (ITF), launched in 1991, established an international recycling agreement for EPS, which has now been signed by more than 25 countries [8]. A major market for recycled EPS is the manufacture of new EPS cushioning. Loosefill cushioning, especially, can also be reused. Many AFPR members cooperate with mailing service organizations to collect

Export

Injection ig

Export

Injection

Injection molded non-packaging 23.4%

Figure 4.9. Uses of PS in the United States and Canada, 2000 [3].

Extrusion, non packaging 22.0%

Extrusion, packaging 20.5%

Injection molded non-packaging 23.4%

Figure 4.9. Uses of PS in the United States and Canada, 2000 [3].

EPS from consumers for reuse or recycle, and the organization maintains a listing of collection sites [9].

Polystyrene, particularly foamed polystyrene, came under considerable attack from environmental organizations in the 1980s, due to its association with litter and with ozone depletion. While some PS foams, including packaging foams, were manufactured with chlorofluorocarbon (CFC) blowing agents, EPS molded foams never used CFCs. In all industrialized countries, use of CFCs in packaging materials, including PS, was phased out a number of years ago. The blowing agents used today, for both molded and extruded foams, are hydrocarbons or, increasingly, carbon dioxide.

The litter problem remains with us. While it is certainly true that litter is a consequence of unacceptable human behavior, not inherent in the material, when littered, PS does not biodegrade, so it can remain in the environment for a very long period of time. The static cling tendencies of PS also contribute to its propensity to be littered, as can be attested to by anyone who has tried to pour a box of loosefill cushioning into their trash — especially if there was even a gentle breeze at the time!

4.5.6. Polyvinyl Chloride

Packaging is only a small part of the market for polyvinyl chloride (PVC), which has seen declining market share in packaging over the last decade or so. PVC packaging in U.S. municipal solid waste is predominantly in the "other packaging" category (Fig. 4.10), especially in the form of trays and blister packaging. These are used in a variety of applications, including wide use in medical packaging.

The properties of PVC packaging can be manipulated to a very wide degree by plasticization. Therefore, PVC packaging ranges from relatively stiff and brittle containers to very soft flexible film used for wraps. In general, PVC is a highly transparent material, with some tendency to yellow over time, especially if it is

Containers 30.2%

Other packaging 58.1%

Other packaging 58.1%

Figure 4.10. PVC Packaging in U.S. municipal solid waste, 1998 [1].

Figure 4.10. PVC Packaging in U.S. municipal solid waste, 1998 [1].

exposed to sunlight. It thermoforms very readily, making it often the material of choice for blister packaging. The barrier performance ranges from reasonably good in bottles to relatively poor in films.

PVC has been under attack from environmental groups on a variety of grounds for a number of years. Because PVC contains chlorine, it may lead to the formation of chlorinated dioxins if it is disposed by incineration. While evidence suggests that the presence or absence of PVC is not very significant in dioxin emissions from well-controlled incineration, less important than combustion conditions, there is reason for concern about its presence in poorly controlled incineration systems. PVC has also been attacked because of concerns related to the carcinogenicity of its vinyl chloride monomer. Increasingly, lead and cadmium stabilizers used in some PVC resins are being restricted or banned, due to concerns about toxic effects of these heavy metals.

Another set of concerns relates to the plasticizers used in PVC, in particular, the endocrine-mimicking effects of phthalate plasticizers. This concern led to widespread abandonment of PVC in soft toys for infants and more recently to calls for discontinuation of the use of phthalate-plasticized bags for intravenous (IV) solutions used in hospitals. In April, 2001, the European Parliament voted for stricter standards on the use of PVC, which is likely to lead to more switching away from PVC packaging [10].

PET (including PET copolymers such as glycol modified PET, PETG) has emerged as a strong competitor to PVC in both bottle and thermoformed sheet markets. PET offers transparency as good or better than PVC, and recent price reductions for PET have made it highly competitive. Additionally, PET does not carry the negative environmental image of PVC.

In the United States, there is very little recycling of PVC packaging materials. As mentioned, most recycling collection programs target only bottles. Since relatively few PVC bottles are available, they are generally not accepted in collection programs, with the exception of those collecting all plastic bottles. Recycling of PVC bottles is also problematic if they are mingled with PET bottles. PET is extremely susceptible to degradation from even very small amounts of PVC. The "look-alike" nature of PVC and PET bottles means that if both are collected, hand sorting is likely to result in some degree of contamination. Very effective automated sorting systems have been developed for PET/PVC separation of intact containers, but it is relatively expensive, and not all separation facilities can afford the capital investment. Contamination of PET from PVC components in packages, such as liners in closures, labels, and the like, can also be a significant problem. Density-based separation systems cannot be used effectively to separate these two resins, as their density ranges overlap.

4.5.7. Other Plastics

As mentioned, a variety of plastics are used in lesser quantities than the major packaging plastics discussed above. These materials are, in general, significantly more expensive but have specific properties that make them important for particular types of applications.

Nylons (polyamides) excel when high-temperature performance is required, such as for boil-in-bag packaging for frozen foods. They provide excellent odor and flavor barrier, moderate oxygen barrier, and excellent strength and toughness.

Ethylene vinyl alcohol (EVOH) and polyvinylidene chloride (PVDC) are the usual choices when excellent oxygen barrier is required. EVOH offers better oxygen barrier when dry than PVDC, but barrier decreases substantially at high humidity. EVOH is also more readily processed than PVDC. Both are commonly used as one component in a multilayer structure, rather than alone.

Polycarbonate (PC) is highly transparent, and very strong and tough. It has been the material of choice for refillable 5-gal water bottles but is beginning to experience competition from PET in this market. It also has a number of applications in medical packaging.

Polyethylene naphthalate (PEN) is a polyester with improved properties compared to PET. It is a better barrier and has improved strength and high-temperature stability, but it is considerably more expensive than PET. So far, its high cost has prevented its widespread use in packaging.

Polyvinyl acetate (PVA) and ethylene vinyl acetate (EVA) are widely used in adhesive formulations and also have some use as packaging films.

Polyacrylonitrile (PAN) in copolymer form is used in high-barrier containers, particularly for household or industrial chemicals.

A number of other specialty polymers are used in packaging as well. Recycling of these materials is essentially nonexistent. Small amounts may be incorporated in mixed-plastic recycling systems that manufacture items such as plastic lumber. The relatively small amounts of these plastics that are available for recovery, and the additional complication that they often form part of multilayer structures, make their recovery and recycling as pure materials impractical in most cases.

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