Polypropylene The invention of PP was nearly simultaneous in the U.S. and Europe. Today, PP is the largest volume commodity thermoplastic. The American Plastics Council (APC) pegs North American PP consumption last year at 16.446 billion lb. This compares with 6.438 billion lb for LDPE, the only polyolefin that existed prior to 1955.

In 1953, Prof. Giulio Natta at Milan Polytechnic in Italy further developed the breakthrough of that same year by Prof. Karl Ziegler at the Max Planck Institute for Coal Chemistry in Germany. Prof. Ziegler discovered that titanium tetrachloride could catalyze stereospecific polymerization of polyethylene. With financial aid from Montecatini (later Montedison), a large Italian chemical company, Prof. Natta extended Prof. Ziegler�s discovery to the development of isotactic PP, which Montecatini was the first to produce on an industrial scale in 1957 in its Ferrara plant. At NPE 1956, Montecatini exhibited PP film and monofilaments.


Two of the first major applications for PP were monofilament (below) and bi-oriented film for bread wrap and other packaging. (Photos: Enjay Laboratories, U.S.I.)
In the U.S., meanwhile, Paul Hogan and Robert Banks of Phillips Petroleum (now Chevron Phillips) were experimenting with high-octane gasoline when they discovered high-melting crystalline PP in 1952. Phillips did not start commercial production of PP until the early �60s. The first commercial producer in the U.S. was Hercules Powder Co. (bought by Montedison and ultimately part of Basell) in 1958. Others quickly followed.

By NPE 1958, PP homopolymers were available from Hercules, Chemore, Spencer Chemical (marketing for Exxon), and Capac Plastics. Besides Montecatini, Hoechst in Germany and ICI in England were bringing on commercial capacity. Avisun Corp. soon after was producing PP homopolymer and random copolymer at New Castle, Pa. Although Montecatini was first to make both random and impact copolymers, Avisun introduced the first impact copolymers in the U.S. at NPE �61, with Hercules and others soon to follow. Avisun was acquired by Amoco in 1967.

Among the very first commercial PP applications were monofilaments for fabrics, carpets, and ropes, as well as clear, biaxially oriented (BOPP) films used as replacements for cellophane in cigarette wrap, bread wrap, and retail packaging for shirts and other garments. Closely following in the late 1950s and early �60s were extruded pipe, strapping, drinking straws, and wire/cable coatings. One of the first injection molded products was a two-piece bed pan. This was followed by a variety of electrical parts, washing-machine tubs and impellers, hypodermic syringe barrels, medicine bottles, and food containers. A big breakthrough was the screw cap with a living hinge for Seagram�s liquor bottles. This essentially knocked polystyrene out of the closure business and led the way for PP into all types of consumer bottle caps.


A breakthrough application for molded PP was the first washing-machine agitator�this 3-lb unit was molded for Kelvinator by American Motors� Evart Products Co. on a 1200-ton, three-stage plunger machine with preplasticator.
By the early 1960s, PP and its copolymers were being used in several automotive applications. This included the use of impact copolymers for battery cases and fender liners, random copolymers for washer-fluid reservoirs, and filled homopolymers for air-intake and heater ducting. Impact copolymers were soon used for auto door interior trim and liners, as well as dashboards. There is currently an average of more than 50 lb of PP used in an automobile.

In the late �60s, blow molded containers, such as bottles for detergents, food, shampoos, and other liquids, made a splash. The first was for Procter & Gamble�s Dawn dish soap in 1967, which initially was made by the Phillips Orbet extrusion stretch-blow molding process, made obsolete a decade later by PET injection stretch-blow molding. PP�s impact resistance and ease of blow molding soon spawned applications such as ice chests, water coolers, housewares, toys, furniture, appliance housings, dairy containers, and snack-food packaging (metalized BOPP film).


HDPE ( High Density Polyethylene )

The invention of the low-pressure process to make HDPE took place in both the U.S. and Europe at nearly the same time and centered around the development of types of catalysts that promoted ethylene polymerization at milder temperatures and pressures than were (and still are) used for LDPE.


The Hula Hoop craze of 1957, based on a circular tube of HDPE, sparked the development of HDPE pipe. (Photo: Chevron Phillips)
The first of these new catalysts was discovered in 1951 by Robert Banks and John Hogan at Phillips Petroleum (who were also pioneers in PP polymerization). In 1953, Prof. Karl Ziegler at Germany�s Max Plank Institute for Coal Chemistry developed another low-pressure/low-temperature catalyst system. By the late 1950s, both methods were being used for HDPE production. In Europe, the first full-scale low pressure HDPE plant was erected by Farbwerke Hoechst AG in late 1955. Plastics Technology reported in September 1955 that Hoechst�s Hostalen resin, with a density of 0.94 g/cc, was the talk of the Hanover Industrial Fair in Germany, where it was shown for the first time in applications such as film, pipe, tubing, and molded household articles.

In the U.S., Phillips produced the first commercial HDPE (0.963 density) under the Marlex tradename in the summer of 1956, although it had provided pilot plant quantities as early as 1955. At NPE 1958, commercial HDPE resins were featured by Celanese, Phillips, Spencer Chemical (marketing for Exxon), and W.R. Grace. These suppliers highlighted the potential of blow molded rigid HDPE for replacing glass containers. Other early suppliers to follow included Hercules, Koppers, and Dow.

Among the earliest products were extrusion blow molded bottles for bleach and detergents, baby bottles, and injection molded housewares, such as the famous Tupperware containers.


Baby bottles were one of the first applications for HDPE. (Photo: Chevron Phillips)
One of the largest volume applications emerged in an unexpected way in 1957, when the Hula Hoop, an extruded tube bent into a circle, became a fad among teenagers throughout the U.S. and abroad. Wham-O, which trademarked the Hula Hoop name and was its most successful manufacturer, produced the toy using Phillip�s Marlex HDPE. It was this fad that led to large-volume manufacturing of extruded HDPE pipe for high-performance applications such as natural-gas distribution, handling mine tailings, and sewer lines.

Use of blow molded HDPE bottles grew far beyond detergents and bleach to include shampoos, motor oil, drug and cosmetic products, water, and milk. Milk bottles, in fact, are the single biggest volume HDPE package. Other large-volume applications are ice chests, beverage coolers, jerry cans, trash cans, storage drums, auto fuel tanks, injection molded food containers (e.g., for margarine and yogurt), and wire/cable coatings�including trans�oceanic cables.

Meanwhile, high-molecular-weight (HMW) HDPE made its impact in the film market a bit later. In 1979, Sonoco tested the shopping/grocery bag potential of HMW-HDPE. At NPE �88, HDPE blown film lines were a highlight.

The American Plastics Council (APC) figures North American HDPE consumption in 2004 at 15.264 billion lb, making it the second-largest volume commodity thermoplastic after PP.


The modern era of engineering thermoplastics was launched in 1953 when Dr. Hermann Schnell of Bayer AG in Germany and Dr. Daniel W. Fox of GE Plastics in Pittsfield, Mass., independently discovered the versatile engineering resin called polycarbonate.


In the 1980s, optical discs became a huge new market for PC. (Photo: Bayer MaterialScience)
Fox was conducting a series of experiments while working to develop a new wire insulation material when he found himself with a transparent substance that hardened in a beaker. That marked the beginning of GE�s Lexan polycarbonate business. Schnell discovered polycarbonate while working on aromatic derivatives at Bayer�s main lab in Uerdingen, Germany. As result, the company�s Makrolon PC business was born. Both companies began to commercially produce PC in 1958. (It was first reported in the New Materials section of Plastics Technology in December of that year.)

The first commercial production of bisphenol-A (BPA), an important feedstock for PC, was a turning point. BPA was first made for epoxy resins but its reaction with phosgene made commercial production of PC possible.


Architectural glazing is an important market for clear, impact-resistant PC sheet. (Photo: GE Plastics)
Polycarbonate today is one of the most widely used engineering thermoplastics in the world. It has found extensive use in business equipment, automobiles, and telecommunications products. Polycarbonate was first used for electrical and electronic applications such as distributor and fuse-box covers and later was extruded into sheet and used as glazing for greenhouses and other architectural applications. In the 1980s, polycarbonate�s clarity, light weight, and impact resistance made it the ideal replacement for glass in automotive headlamps. For car makers, the use of PC brought vast new potential for front-end design.

Another breakthrough application came in 1982 with the introduction of the compact disc with PC as the substrate. Other major applications include 5-gal water bottles, cell phones, eyeglass lenses, DVDs, and bullet-proof glazing. Today, the PC market is growing about 8% annually and total global consumption is about 5.4 billion lb/yr.


ABS Resins

The addition of butadiene rubber as a third monomer to styrene-acrylonitrile resulted in development of a new range of widely used thermoplastics called ABS. Marbon (later Borg-Warner Chemicals and then GE Plastics), Monsanto, and Union Carbide were key developers of the technology in the 1950s but Marbon emerged as the leading supplier. In 1954, Marbon launched Cycolac ABS resin and in 1958 a $12-million plant was commissioned in Washington, W.Va. By 1962, Marbon was selling about $1 million worth of ABS a month.

Because the three-monomer system could be tailored to yield different balances of properties, ABS grew to become the largest-volume engineering thermoplastic. ABS served as a bridge between commodity plastics such as PE and PS and higher performance materials such as polycarbonate and nylon.

Initially, the big-volume breakthrough applications were the RCA portable radio and Western Union telephone handset. By 1961, ABS had launched a major assault on phenolics and cellulosics in phone handsets. Other successes included appliances, computer and office-equipment housings, lawn-mower housings, safety helmets, luggage shells, pipe, and fittings.

World consumption of ABS amounted to approximately 12.1 billion lb in 2004, with Asia accounting for almost 70%. Major markets include appliances and electrical/electronic parts, with lesser use in autos and recreational vehicles, pipe and fittings, and miscellaneous consumer products. The top ten ABS producers in the world�Chi Mei of Taiwan, LG Chemicals of Korea, GE Plastics, BASF, Lanxess, Cheil in Korea, Formosa Plastics in Taiwan, Dow, Grand Pacific in Taiwan, and Techno Polymer in Japan�accounted for 74% of world capacity, according to SRI.

PET ( Polyethylene Ethylene Tere Phthalic Acid)

PET was invented in 1941 by ICI in the U.K. and played its first role as a fiber, and its second as film with DuPont�s introduction of Mylar in 1952. It took more than 20 years for PET molding grades to come onto the scene. When they did, they revolutionized the packaging industry with oriented bottles.

In 1973, DuPont�s Nathaniel Wyeth patented the oriented PET beverage bottle. Because DuPont lacked solid-state PET resin production, its initial efforts to produce bottle preforms were unsuccessful, owing to insufficient intrinsic viscosity (I.V., a measure of molecular weight). The first commercial production of PET resin suitable for injection molding preforms came from Goodyear in 1974, which had solid-state capability in place. Between 1976 and 1978, three other suppliers�Celanese, American Hoechst, and Eastman�brought on PET bottle-resin capacity

At NPE 1979, Eastman Chemical introduced �spruce green� bottle-grade PET resins so that plastic bottles could match the color of glass bottles. In the early 1980s, CPET (crystallized PET) arrived as a highly heat-resistant material for thermoformable, dual-ovenable food trays for prepackaged meals and entrees. At NPE 1991, amorphous PET (APET) resins for extrusion blow molding of handleware were introduced by Eastman, DuPont, and Goodyear. APET did not take off, as the market found it too costly because of the thicker walls required. More successful was a glycol-modified amorphous PET, called PETG, introduced by Eastman in 1977. It has been successful in injection and blow molded containers and extruded sheet and profiles.

The current U.S. PET resin market is approaching 7 billion lb/yr. PET dominates the soda and �premium� water bottle market for 2-liter and smaller bottles, where handles are not required.


In 1978, DuPont�s Rynite introduced glass-reinforced PET engineering compounds for injection molding. (Photo: Rynite coil form)
Engineering PET compounds
Glass- or mineral-filled PET was introduced by DuPont in 1978. Rynite PET constituted the first �engineering� grade of PET for general-purpose injection molding. It overcame the limitations of previous reinforced PETs, which were difficult to mold and suffered poor surface quality, brittleness, and warpage. Many of the earliest applications were electrical parts, such as coil forms, automotive ignitions, transformer housings, terminal blocks, motor end brackets, fuse caps, and light housings. Some other applications in Rynite�s first decade were chair shells and arms, bicycle drive parts, and boat propellers. Within five years, Rynite had at least four domestic competitors and at least 15 by the end of the 1980s.

PBT was first in molding
PBT for injection molding was first brought to the market in 1969 by Celanese, with its Celanex 3300, a 30% glass-filled grade. In 1972, GE introduced both unreinforced Valox PBT and a 30% glass-filled grade. Not long after, GE launched flame-retardant grades. By 1977, Eastman, GAF, LNP, and Thermofil had entered the business, with Fiberfil and Mobay not far behind.

The earliest PBT applications were in the electrical/electronic connectors, switches, controls, and automotive high-energy ignition systems. PBT also played a major part in the development of plastic automotive bumper systems. GE alloyed PBT with PC to produce Xenoy, a material with high impact strength at low temperatures plus heat and chemical resistance that enabled all-plastic auto-bumper systems to replace steel. The 1984 Ford Taurus/Mercury Sable were the first cars to utilizes this system in both front and rear bumpers.



Chemical Blowing Agents

Despite early experiments with sodium bicarbonate�ordinary baking soda�the era of foamed plastics had to await the results of German work on hydrazine-based rocket propellents during World War II. Information on these azo compounds leaked out to Uniroyal in the U.S., so that by 1950, both this company and Bayer in Germany were using exothermic blowing agents in rubber.

Uniroyal commercialized its blowing agents under the Celogen name. They were based on hydrazine, hydrazide, or azodicarbonamide. The last became one of the most widely used exothermic chemical blowing agents (CBAs) for plastics. One of its first big uses was PVC plastisol flooring in the late 1950s to early 1960s. Another, which developed in the mid-�60s, was low-density crosslinked LDPE foams. Applications included cushioning materials for car door interior panels as well as packaging and athletic equipment padding. Injection molded PS, ABS, and PP foams also originated in the mid-�60s using azo CBAs.

A major early extrusion application in the early to mid-1970s was telephone wire and cable insulation, primarily of foamed HDPE. In the mid-1970s, structural foam�HIPS, HDPE, PP, and ABS�began to become prominent. Initially, structural foam makers had used direct injection of nitrogen gas, but that required a costly license and specially modified equipment. The availability of chemical blowing agents allowed all molders, including smaller ones, to produce both small and large parts economically.

Use of CBAs for rotomolding foamed parts began in the early 1980s. About that time, interest in foamed TPEs for soft-touch applications took off. Activated azos with reduced initiation temperatures were among those used.

In 1984, CBAs of the endothermic variety came to the U.S. from Europe. The first was Hydrocerol from Germany�s Boehringer Ingelheim (now a product of Clariant Masterbatches.) Ironically, they were based on sodium bicarbonate plus citric acid. These products were less sensitive to loading levels and were said to produce finer cell structures and smoother surfaces. Also, endothermics were �cleaner,� producing only CO2 and water, and left no deposits on screws or molds. Faster degassing of parts was also claimed, and they contributed less color to foamed parts.