Resins and types of packaging
Plastic is often a more efficient material to choose than alternatives. That’s because plastics are incredibly energy efficient to manufacture and because they are lighter than alternative materials. Just two pounds of plastic can deliver 10 gallons of a beverage. You’d need three pounds of aluminum, eight pounds of steel, or over 40 pounds of glass to bring home the same amount of a beverage. Here’s a look at some plastic resins and some of the ways they’re commonly used in packaging applications.
High Density Polyethylene (HDPE)
About
HDPE is the most widely used type of plastic. It’s used to make many types of bottles and containers. Unpigmented bottles are translucent, have good barrier properties and stiffness, and are well suited to packaging products with a short shelf life such as milk. Because HDPE has good chemical resistance, it is used for packaging many household and industrial chemicals such as detergents and bleach. Pigmented HDPE bottles have better stress crack resistance than unpigmented HDPE.
Properties
Excellent resistance to most solvents
Higher tensile strength compared to other forms of polyethylene
Relatively stiff material with useful temperature capabilities
Common Packaging Applications
Bottles for milk, water, juice, cosmetics, shampoo, dish and laundry detergents, and household cleaners
Bags for groceries and retail purchases
Cereal box liners
Low Density Polyethylene (LDPE)
Includes Linear Low Density Polyethylene (LLDPE)
About
LDPE is used predominately in film applications due to its toughness, flexibility, and relative transparency, making it popular for use in applications where heat sealing is necessary. LDPE also is used to manufacture some flexible lids and bottles as well as in wire and cable applications.
Properties
Excellent resistance to acids, bases, and vegetable oils
Toughness, flexibility, and relative transparency; good combination of properties for packaging applications requiring heat-sealing
Commom Packaging Applications
Bags for dry cleaning, newspapers, bread, frozen foods, fresh produce, and household garbage
Shrink wrap and stretch film
Coatings for paper milk cartons and hot and cold beverage cups
Container lids
Squeezable bottles (e.g., honey and mustard)
Polyethylene Terephthalate (PET, PETE)
About
PET is clear, tough, and has good gas and moisture barrier properties. This resin is commonly used in beverage bottles and many injection- molded consumer product containers. Cleaned, recycled PET flakes and pellets are in great demand for spinning fiber for carpet yarns and producing fiberfill and geotextiles.
Properties
Clear and optically smooth surfaces for oriented films and bottles
Excellent barrier to oxygen, water, and carbon dioxide
High impact capability and shatter resistance
Excellent resistance to most solvents
Capability
Commom Packaging Applications
Plastic bottles for soft drinks, water, juice, sports drinks, beer, mouthwash, catsup, and salad dressing
Food jars for peanut butter, jelly, jam, and pickles
Ovenable film and microwavable food trays
Polypropylene (PP)
About
PP has good chemical resistance, is strong, and has a high melting point making it good for hot-fill liquids. This resin is found in flexible and rigid packaging, fibers, and large molded parts for automotive and consumer products.
Properties
Excellent optical clarity in biaxially oriented films and stretch blow molded containers
Low moisture vapor transmission
Inertness toward acids, alkalis, and most solvents
Commom Packaging Applications
Containers for yogurt, margarine, takeout meals, and deli foods
Medicine bottles
Bottle caps and closures
Bottles for catsup and syrup
Polystyrene
About
PS is a versatile plastic that can be rigid or foamed. General purpose polystyrene is clear, hard, and brittle. It has a relatively low melting point. Typical applications include protective packaging, food service packaging, bottles, and food containers. PS is often combined with rubber to make high impact polystyrene (HIPS) which is used for packaging and durable applications requiring toughness, but not clarity.
Properties
Excellent moisture barrier for short shelf life products
Excellent optical clarity in general purpose form
Significant stiffness in both foamed and rigid forms
Low density and high stiffness in foamed applications
Low thermal conductivity and excellent insulation properties in foamed form
Commom Packaging Applications
Food service items, such as cups, plates, bowls, cutlery, hinged takeout containers (clamshells), meat and poultry trays, and rigid food containers (e.g., yogurt)
These items may be made with foamed or non-foamed PS.
Polyvinyl Chloride (PVC, Vinyl)
About
In addition to its stable physical properties, PVC has good chemical resistance, weatherability, flow characteristics, and stable electrical properties. The diverse slate of vinyl products can be broadly divided into rigid and flexible materials.
Properties
High impact strength
Brilliant clarity
Excellent processing performance
Resistance to grease, oil, and chemicals
Commom Packaging Applications
Rigid packaging applications include:
Blister packs and clamshells
Flexible packaging uses include:
Bags for bedding and medical, shrink wrap, deli and meet wrap and tamper resistance
Source: Plastic Packaging Facts