Plastic provides the most durable, cost-effective and eco-friendly solution available to meet industrial packaging needs today. The following is a guide to the different types of plastic resins used for containers and their packaging applications.
High Density Polyethylene (HDPE) is the most widely used resin for plastic containers. This material is economical, impact resistant, and provides a good moisture barrier. HDPE is compatible with a wide range of products including acids and, when fluorine treated, becomes an effective package for solvents and oxygen sensitive extracts. It is usually supplied in FDA/EU approved food grade. HDPE is naturally translucent and flexible. The addition of colour makes HDPE opaque although not glossy. Adding extra weight yields a rigid container. HDPE can be supplied surface-treated and is suitable for silk screen decoration. While HDPE provides good protection at below freezing temperatures, it cannot be used with products filled at over 180°F or products requiring a hermetic seal. A glossy surface can be achieved with the use of the special copolymer resin, High Gloss HDPE.
Post Consumer Resin (PCR) is a blend of reclaimed natural HDPE (primarily from milk and water containers) and virgin resin. The recycled material is cleaned, ground and recompounded into uniform pellets along with prime virgin material especially designed to build up environmental stress crack resistance. PCR has no odour but exhibits a slight yellow tint in its natural state. This tint can be hidden by the addition of colour. PCR is easily processed and inexpensive. However, it cannot come into direct contact with food or pharmaceutical products. PCR can be produced in a variety of recycled content percentages up to 100%.
Low Density Polyethylene (LDPE) is similar to HDPE in composition. It is less rigid and generally less chemically resistant than HDPE, but is more translucent. LDPE is used primarily for squeeze applications. LDPE is significantly more expensive than HDPE, but will yield a glossy container when produced in colours.
Medium Density Polyethylene (MDPE) combines the characteristics of low and high density polyethylene. Containers are less translucent than LDPE but more flexible than HDPE. Like LDPE, MDPE is glossy when produced in colours.
Polypropylene (PP) is a naturally translucent material which provides contact clarity and an excellent moisture barrier. One major advantage of polypropylene is its stability at high temperatures, up to 200°F. Therefore, it is used for hot fill products such as pancake syrup. Polypropylene is also autoclavable and offers the potential for steam sterilization. PP has excellent chemical resistance, but provides poor impact resistance in cold temperatures. Oriented PP offers improved impact resistance and clarity at low temperatures. Produced in colour, PP exhibits a glossy finish.
Polystyrene (PS) offers excellent clarity and stiffness at an economical cost. It is commonly used with dry products including vitamins, petroleum jellies and spices. Styrene does not provide good barrier properties and exhibits poor impact resistance. It can be screen printed without being flame treated and lends itself well to offset printing.
Polyvinyl Chloride (PVC) is naturally clear, has extremely good resistance to oils, and has very low oxygen transmission. It provides an excellent barrier to most gases and its drop impact resistance is also very good. This semi-rigid material is also very chemically resistant, but it is vulnerable to solvents.
PVC is available in general purpose grade, food grade, and fragrance-guard perfume grade. The occurrence of the blue tint in clear PVC can be modified by controlling the toner levels in each of these grades. General Purpose PVC will distort at 160°F, making it incompatible with hot filled products. New PVC grades are able to withstand temperatures up to 190°F and can be hot filled. It is not compatible with hot filled products. Since it provides a good oxygen barrier, PVC is an excellent choice for salad oil, mineral oil, and vinegar. It is also commonly used for shampoos and cosmetic products.
Polyethylene Terephthalate (PET) is a durable material offering outstanding clarity, good impact and scratch resistance, high gloss finish and good barrier properties. PET containers are lightweight and safe compared to glass (no breakage on filling lines, in transit, retail stores and in homes). Containers manufactured with PET resin are ideal for packaging a wide range of food product, toiletries, cosmetics and household and pharmaceutical products. Each application should be tested to ensure that the product is compatible with the container, especially with products that contain alcohol.
Because of their range of properties and design technologies, plastics offer benefits unsurpassed by other materials. A deeper description of the history and chemistry of plastics can be found at The Society of the Plastics Industry (SPI)
| Properties | PET Oriented | PET Unoriented | PETG | PVC Unoriented | HDPE | LDPE | PP |
| Clarity | Clear + | Clear + | Clear + | Clear | Translucent | Translucent+ | Translucent+ |
| Scuffing Resistance | poor/fair | poor/fair | fair | good | very good | very good | very good |
| Impact Strength | good to excellent | poor to fair | poor to fair | fair to good | good to excellent | excellent | poor to good |
| Stiffness | moderate to high | moderate to high | moderate to high | moderate to high | moderate | low | moderate to high |
| Maximum Hot Fill* | 120°F | 140°F | 140°F | 140°F | 180°F | 150°F | 240°F |
| Permeability to: | |||||||
| Water | moderate | moderate | moderate | moderate | very low | low | very low |
| Oxygen | low | low | low | low | high | very high | high |
| CO2 | very low | low | low | low | high | very high | moderate to high |
| Resistance to: | |||||||
| Acids | fair to good | fair to good | fair | good to very good | fair to very good | fair to very good | fair to very good |
| Alcohols | good | good | poor | good to very good | good | fair to very good | good |
| Alkalis | poor to fair | poor to fair | poor to fair | good to very good | good to very good | good to very good | very good |
| Minimum Temperature (Brittleness) |
- 40°C | — | - 40°C | 30°C | - 100°C | - 100°C | 0°C |
| Density | 1.35-1.40 | 1.35-1.40 | 1.27-1.35 | 1.35 | .94-.965 | .91-.925 | .89-.91 |
| *This chart is a guideline only. Variables such as container weight and wall thickness may have an effect on material performance. Testing is always recommended. | |||||||