Glossary - P

Packaging Efficiency:
A quantification of the efficiency by which competing packaging materials deliver product to market. It is derived by comparing the volume of product delivered per pound of packaging. It is one way to quantify the achievement of source reduction, i.e., delivering the most product per unit of packaging. ("Factoring the Value of Source Reduction into Packaging Use/Post-Use Economics," Ronald Perkins, Recycle 93 Sixth Annual Forum, Davos, Switzerland).

Pelletizing:
A process for producing a uniform particle size of virgin or recycled plastic resins. Molten polymer from an extruder is forced through a die to form multiple strands of resin (similar to the chopping of spaghetti from extruded dough). Traditionally the strands are pulled by nip rolls through a water bath to cool and solidify and then into a cutting chamber where they are chopped into approximately 1/4" lengths. Modern systems incorporate underwater pelletizers where the strands are cut by a rotating knife immediately upon exiting the die. This operation takes place in a closed head as water circulates through to cool and carry the pellets away. Both methods move the pellets to a dewatering/drying system prior to final packout. (Modern Plastics Encyclopedia 1995).

Phthalate Ester (o-phthalic ester):
Any of a large class of plasticizers produced byt he direct action of alcohols on phthalic anhydride. The phthalates are the most widely used of all plasticizers and are generally characterized by moderate cost, good stability, low toxicity and good all-around properties. (Whittington's Dictionary of Plastics, published by Technomic Publishing). To find out more go to the Phthalate Esters Panel's new website or visit the American Chemistry Council website. A special web site has been established to adress the facts about phthalates esters in toys. To find out more, go to http://www.vinyltoys.com/.  

Plastic:
(1) One of many high-polymeric substances, including both natural and synthetic products, but excluding the rubbers. At some stage in its manufacture, every plastic is capable of flowing, under heat and pressure if necessary, into the desired final shape. (2) Made of plastic; capable of flow under pressure or tensile stress. (Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., edited by Michael L. Berins, 1991).

Plastic Bottle:
A rigid container that is designed with a neck that is narrower than the body, normally used to hold liquids and emptied by pouring. (How To Develop a Viable post-consumer plastic Handling Business, APC, 1993).

Plastic Film:
A thin flexible sheet that only holds a particular shape when supported. (How To Develop a Viable post-consumer plastic Handling Business, APC, 1993).

Plastic Packaging:
When a host of different plastics, such as polyethylene, polypropylene, polyester, polystyrene, polyvinyl chloride, polyvinylidene dichloride (Saran), nylon, etc., provide containment, protection, information and utility-of-use (convenience) for commercial products. (Plastic Packaging Opportunities and Challenges, APC, 1992).

Plastics Recovery Facility (PRF):
A facility that receives recyclable plastics and then separates, removes contamination, sorts by resin type and color, condenses, and stores the segregated plastic types. Sorted plastic bottles and containers are then Baled and shipped to recycling markets. (Q & A: Plastics Recovery Facility fact sheet, The Garten Foundation, 1994).

Polyethylene Terephthalate (PET or PETE):
PET is clear, tough and has good gas and moisture barrier properties. Some of this plastic is used in PET soft drink bottles and other blow molded containers, although sheet applications are increasing. Cleaned, recycled PET flakes and pellets are in great demand for spinning fiber for carpet yarns and producing fiberfill and geotextiles. Other applications include strapping, molding compounds and both food and non-food containers. (Adapted from Modern Plastics Encyclopedia 1995).

Polymer:
A high-molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the monomer (e.g., polyethylene, rubber, cellulose). Synthetic polymers are formed by addition or condensation polymerization of monomers. If two or more different monomers are involved, a copolymer is obtained. Some polymers are elastomers, some plastics. (Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., edited by Michael L. Berins, 1991).

Polypropylene (PP):
Polypropylene has excellent chemical resistance, is strong and has the lowest density of the plastics used in packaging. It has a high melting point, making it ideal for hot-fill liquids. In film form it may or may not be oriented (stretched). PP is found in everything from flexible and rigid packaging to fibers and large molded parts for automotive and consumer products. (Adapted from Modern Plastics Encyclopedia 1995; Plastic Packaging Opportunities and Challenges, APC, February 1992).

Polystyrene (PS):
Polystyrene is a very 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, containers, lids, cups, bottles, trays and tumblers. (Plastic Packaging Opportunities and Challenges, APC, February 1992).

post-consumer plastic Plastic:
Any plastic that has entered the stream of commerce, served its intended purpose, and has now been diverted for recycling or export. This includes residential, commercial and institutional plastic. This does not include industrial scrap material like factory regrind and plant scrap used within the primary manufacturing facility. (post-consumer plastic resin is also known as PCR). (1995 post-consumer plastic Plastics Recycling/Recovery Rate Survey, Glossary of Terms, R.W. Beck & Associates).

Process Engineered Fuels (PEF):
PEF, (some known as pellet fuels), are produced from a mixture of industrial and/or commercial plastic scrap and other industrial and/or commercial scrap materials and/or from plastic and other materials diverted from the waste stream, along with binding agents and Additives. The proportions of the major plastic and other components can be varied to yield a pellet fuel possessing the desired combustion characteristics. PEF is designed to provide a highly predictable and uniform Btu content, burn rate and flame temperature, and PEF of a particular composition will yield ash with known characteristics. (Comments of the American Plastics Council on Proposed Revisions to Title V Operating Permit Regulations, submitted to the U.S. EPA, October 30, 1995).

Pyrolysis:
The thermal decomposition of organic material through the application of heat in the absence of oxygen. (The Recycler's Lexicon: A Glossary of Contemporary Terms and Acronyms, Resource Recycling Inc., 1995).

Permeability
Material constant characterising gas penetration, like water vapour, oxygen or carbondioxide.

Peroxide
Peroxides are a group of compounds that contain the O2- ion. It is used to initiate the polymerization for high-pressure free radical polymerization processes.

Polyaddition
A polymerization in which the growth of a polymer chain proceeds by addition reactions between molecules of all degrees of polymerization, not accompanied by the formation of low-molar-mass by-product(s).

Polycondensation
A polymerization in which the growth of a polymer chain proceeds by condensation reactions between molecules of all degrees of polymerization accompanied by the formation of low-molar-mass by-products(s). The growth steps are expressed by P_x+P_y -> P_x+y + L {x} element of {1, 2, ... ¡Ä}; {y} element of{1, 2, ...¡Ä} where P_x and P_y denote chains of degree of polymerization x and y, respectively, and L a low-molar-mass by-product. In a polycondensation where the total amounts of the monomers are present from the beginning of the polymerization, the average degree of polymerization increases with conversation of reactive groups.

Polyolefin
This is the collective name given to those polymers that are made from the lower olefins: ethylene, propylene, butylene and isoprene. The polyolefins are thermoplastic polymers

Prepolymerization
A process where polymerization is started to increase the activity of the catalyst getting over the induction time of the catalyst and not to overheat the catalyst particle by to sudden onset of polymerization. Prepolymerization will also help in ensuring more even polymerization on the catalyst particles reducing the probability of creating a high fraction of fines in the later reaction steps.

Processability
A concept to describe the behavior of the polymer in a converting process, such as blow molding machine and film line. A good processability means a stable behavior in the process and a high processing speed.

Pseudo-copolymer
An irregular polymer, the molecules of which are derived from one species of monomer but for which one finds it convenient to use copolymer terms. Where appropriate, adjectives specifying the types of "copolymer" may be applied to "pseudo-copolymer". The term statistical pseudo-copolymer, for instance, may be used to describe an irregular polymer in the molecules of which the sequential distribution of configurational units obeys known statistical laws.