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. Here’s a look at some plastic resins and some of the ways they’re commonly used in packaging applications
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.
- Excellent resistance to most solvents
- Higher tensile strength compared to other forms of polyethylene
- Relatively stiff material with useful temperature capabilities
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)
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.
- Excellent resistance to acids, bases and vegetable oils
- Toughness, flexibility and relative transparency (good combination of properties for packaging applications requiring heat-sealing)
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).
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, producing fiberfill and geotextiles.
- 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
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.
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.
- Excellent optical clarity in biaxially oriented films and stretch blow molded containers
- Low moisture vapor transmission
- Inertness toward acids, alkalis and most solvents
Containers for yogurt, margarine, takeout meals, and deli foods. Medicine bottles. Bottle caps and closures. Bottles for catsup and syrup.
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, foodservice 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.
- 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
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.
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.
- High impact strength, brilliant clarity, excellent processing performance
- Resistance to grease, oil and chemicals
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.