Common Packaging Plastics

The major plastic resins used in packaging are high-density polyethylene, low-density and Unear low-density polyethylene, polyethylene terephthalate, polypropylene, polystyrene, and polyvinyl chloride. A variety of plastics are used in lesser quantities nylons or polyamides, polycarbonate, polyethylene naphthalate, polyvinyhdene chloride, ethylene vinyl alcohol, polyvinyl alcohol, polyvinyl acetate, polyacrylonitrile, and more. In many applications, copolymers 

In 2000, approximately 15,602 million pounds of virgin high-density polyethylene (HOPE) 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). 

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. 

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 milUon 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]. 

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This book is intended to provide a basic understanding of piastic packaging mate-riais. It covers the properties of common packaging plastics, and relates these properties to the chemical structure of the polymers. Common processing methods for transforming plastic resins into packages are covered. 

Common packaging plastics differ considerably in properties, and therefore are suitable for differing uses. A summary of properties for some of the major plastics... 

Table 4.18 Comparative Properties of Common Packaging Plastics...

Recommended extrusion temperatures for some common packaging plastics are... 

Experimental values of crystalline heat of fusion for common packaging plastics vary from 8.2 kJ/mol for polyethylene to 43 kJ/mol for nylon 66. ASTM D3417 describes a method for measuring the heat of fusion and crystallization of a polymer by differential scanning calorimetry (DSC). 

Polyethylene (PE) is currently the most common packaging plastic in use. It is produced from the polymerization of ethylene which in turn is obtained as a petrochemical product by thermal cracking of ethane and propane. Depending on the polymerization process conditions, different types of PE can be obtained as listed in Table 4. The density ranges given in Table 4 differ in value across different literature sources, and are dependent on the synthesis techniques used for polymerization as well as on the polymerization conditions. 

Multiwall Paper Bags These bags (Fig. 21-40), made from plies of kraft paper or from combinations of kraft and special-purpose papers and plastics, are the most common packages For almost any pelleted or powdered material as well as for briquettes or bats of such solids as synthetic rubber, waxes, and insulation. 

Key findings are reported from a study by David Brown of Warwick Research Institute into the environmental aspects of plastics packaging used for snack foods. The four options of reduction, re-use, recycling and recovery are discussed. The original research examines OPP as the most commonly used plastic for snack food packaging. BODY SHOP... 

It is surprising that even on its golden jubilee polystyrene is known only to the specialists, although it has become one of the most commonly used plastics and has had its place in our daily life for many decades. We come across it in household appliances and toys, in furniture and electrical articles, in vehicles, in building and in mechanical engineering, in refrigeration and in packaging, at the workplace and in leisure activities - and scarcely anybody knows it by name. 

These criteria are not in any particular order and some may conflict with one another. Fortunately for food packaging, in cases where no single plastics monolayer can satisfy all the functional requirements, recently applied technologies such as co-extrusion and lamination can provide complete solutions. The most commonly used plastics for the manufacture of FCMs are given below. 

Lastly, another way to approach the decision about which tool to choose can be addressed from the perspective of which package type from which oxygen levels are desired. For the sake of brevity, only the three most common pharmaceutical packaging (plastic bottles, glass vials/ampoules, blister packages) configurations are discussed. 

Low density polyethylene is one of the most widely used packaging plastics. It is a member of the polyolefin family. Olefin, which means oil-forming, is an old synonym for alkene, and was, originally, the name given to ethylene. Alkenes are hydrocarbons containing carbon-carbon double bonds, such as ethylene and propylene. In the plastics industry, olefin is a common term that refers to the family of plastics based on ethylene and propylene. The term polyolefin strictly applies to polymers made of alkenes, whether homopolymers or copolymers. It includes the family of polyethylene, and the family of polypropylene. 

High density PE is a milky-white, nonpolar, linear thermoplastic. Its density ranges from 0.940 to 0.965 g/cm, and it has a melting temperature of about 128 to 138°C. It is one of the most versatile polymers, and is the second most commonly used plastic in the packaging industry. Typical applications include ... 

Plastics are, in general, good insulators. Gases are much better insulators than solids, so in a foam, the combination of the plastic and the gas pockets within it provides very low thermal conductivity. Each phase, gas and solid, contributes an amount roughly proportional to its volume fraction. Thermal conductivities of some common packaging foams are given in Table 13.1. 

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