This section provides a brief description of common plastic container resin materials, their qualities, usages and limitations.
High Density Polyethylene (HDPE)
HDPE is the most widely used resin for plastic bottles, both injection and extrusion blown. This material is economical, impact resistant, compatible with a wide range of products (including acids and caustics) and provides a good moisture barrier. It is usually supplied in FDA approved food grade. HDPE is not compatible with solvents.
HDPE is naturally translucent and flexible. The addition of color will make HDPE opaque although not glossy. Adding extra weight to the bottle will yield a more rigid container.
HDPE is supplied flame-treated on a stock basis and lends itself readily to silk-screen decoration. While HDPE provides good protection at below freezing temperatures, it cannot be used with products filled at over 160 degrees. or products requiring a hermetic seal.
Low Density Polyethylene (LDPE)
LDPE is similar to HDPE in appearance and characteristics, but is less rigid and in general less chemically resistant than HDPE.
LDPE is used primarily for squeeze applications where the container is 4 oz. or less in capacity. LDPE is more expen-sive than HDPE, but will yield a glossy bottle when produced in colors.
Polypropylene is a naturally translucent material which provides contact clarity and an excellent moisture barrier.
PP is easily processed via injection molding (jars and closures), and injection or extrusion blow-molding (bottles). One major advantage of polypropylene is its stability at high temperatures (max. temp. 230 degrees-260 degrees.); it is autoclavable and offers the potential for steam sterilization. PP's compatibility with high filling temperatures is respons-ible for its use with hot fill products such as pancake syrup.
PP has excellent chemical resistance, but provides poor impact resistance in cold temperatures. Oriented PP offers improved impact resistance at low temperatures.
Produced in color PP exhibits a glossy finish.
Styrene offers excellent clarity and stiffness. 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.
PVC is naturally clear, has extremely good resistance to oils and very low oxygen transmission. It provides an excellent barrier to most gases, but is vulnerable to solvents. PVC is a semi-rigid material which, when produced on extrusion blow-molding equipment, can accommodate handled designs.
Improvements in resin formulation have increased oxygen barrier properties and chemical resistance, with a 20-30% improvement in drop impact resistance. Advances in molding expertise, as well as in resin formulation, have also yielded an injection blow molding grade of rigid PVC.
PVC exhibits low temperature resistance and will distort at 160 degrees. It is not compatible with hot filled products. Because 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.
PVC can also be molded via the stretch and blow process. These oriented bottles provide improved barrier properties while allowing light-weighting of the container. Chemical resistance is also improved due to the elimination of the PVC modifiers which are frequently attacked. Handled containers, however, cannot be produced via the stretch and blow process. Food grade and non-food grade resins must be specified.
Similiar to PVC in clarity and rigidity, but lacks significant barrier properties, "K" Resin is a material easily processed and produced on polyethylene equipment. It is frequently used for display packaging (such as candy, beef jerky, etc.) and is and excellent choice when the product incorporates inner packaging.
Barex is a rubberized compound which provides excellent compatibility with solvents. It is similar in nature to PVC and can be produced on equipment used for PVC blow molding.
Barex is an excellent material for automotive additives, insecticides, lighter fluid, dry cleaning products and all products containing toluene, xylene, trichloroethane, benzene, and most solvents. Barex is not compatible with ketones (acetones or methyl ethyl ketone).
Barex has a slight brownish tint in its natural state, but is glossy when produced in colors. this material exhibits poor drop impact resistance at temperatures below freezing and cannot be subjected to temperatures above 150 degree F.
Barex costs approximately 10% more than PVC and is a material subject to minimum run quantities.
Nyalene is a proprietary name for the combination of Nylon (Selar) with HDPE in ratios from 5-20 percent by weight. This combination, known as nylon alloying, produces a bottle similar in appearance to HDPE with exceptional barrier properties to hydrocarbons and aromatic solvents. Nyalene also resists penetration by oxygen and carbon dioxide and is excellent for use with insecticides, photo-chemicals, agrochemicals, household cleaners, waxes, paint thinner and gasoline.
Nyalene is available on a stock basis in one gallon and smaller sizes. Nyalene can be decorated without regard to heat sensitivity. It is a moderately expensive material.
A Teflon lining can be produced inside an HDPE bottle with or subjecting it to flouorine gas. This Teflon coating yields an effective barrier to most solvents. Fluorine gas is dangerous and corrisive making this a high-priced material.
Crystal clear, strong and rigid, Polycarbonate is autoclavable, non-toxic, and unbreakable. FDA approved for food and drug applications, this resin is the toughest of all thermoplastics, but is soluble in various organic solvents.
Polycarbonate is ideal for high temperature applications and can also withstand low temperatures. It is commonly used as the alternative to glass 5 gallon water bottles.
New multi-layer technology holds potential for PC use as the outer and inner layers of a multi-layered bottle providing clarity, glass and high temperature resistance.
Lexan is GE's trade name for Poly-carbonate.
Polyester (PETG, and PET)
PETG: Glycol modified Polyethylene Terephthalate is a tough, durable material with excellent gloss and clarity and the sparkle desired for clear bottles. PETG can be processed via conventional extrusion blow-molding methods, generally on machines designed to process PVC or Polycarbonate.
Applications include shampoos, soaps, detergents and products not requiring high oxygen or moisture barriers.
PET: Polyethylene Terephthalate is an excellent material for use in orientation-blow-molding (stretch blow molding). It is commonly used for carbonated beverage bottles.
Oriented PET provides very good alcohol and essential oil barrier properties, generally good chemical resistance (although acetones and ketones will attack PET) and a high degree of impact resistance and tensile strength. The orienting process also serves to improve gas and moisture barrier properties.
This material does not provide resistance to high temperature applications (max. temp. 140 degrees). Further the orienting process does not lend itself to the production of handled bottles.
A saran or PVDC film can be spray applied to PET , dramatically improving gas barrier properties and allowing for light weighting of containers.