Blog

Tracing the History of Polymeric Materials: PET | Plastics Technology

A 360-degree look at resin conveying systems: types, operation, economics, design, installation, components and controls.

This Knowledge Center provides an overview of resin moisture and the drying process, including information on the best drying practices for your manufacturing facility. Rel Pet Resin

Tracing the History of Polymeric Materials: PET | Plastics Technology

Combat the skilled labor shortage using this comprehensive resource to train your own plastics processing experts.

Deep dive into the basics of blending versus dosing, controls, maintenance, process integration and more.

This Knowledge Center provides an overview of the considerations needed to understand the purchase, operation, and maintenance of a process cooling system.

Learn about sustainable scrap reprocessing—this resource offers a deep dive into everything from granulator types and options, to service tips, videos and technical articles.

Second quarter started with price hikes in PE and the four volume engineering resins, but relatively stable pricing was largely expected by the quarter’s end.

While the major correction in PP prices was finally underway, generally stable pricing was anticipated for the other four commodity resins.

Despite price increase nominations going into second quarter, it appeared there was potential for generally flat pricing with the exception of a major downward correction for PP.

First quarter was ending up with upward pricing, primarily due to higher feedstock costs and not supply/demand fundamentals.

Despite earlier anticipated rollover in prices for most of the volume commodity resins, prices were generally on the way up for all going into the third month of first quarter.  

While price initiatives for PE and PVC were underway, resin prices had rollover potential for first two months of 2024, perhaps with the exception of PET.

Resin drying is a crucial, but often-misunderstood area. This collection includes details on why and what you need to dry, how to specify a dryer, and best practices.

Take a deep dive into all of the various aspects of part quoting to ensure you’ve got all the bases—as in costs—covered before preparing your customer’s quote for services.

In this collection of articles, two of the industry’s foremost authorities on screw design — Jim Frankand and Mark Spalding — offer their sage advice on screw design...what works, what doesn’t, and what to look for when things start going wrong.

In this collection, which is part one of a series representing some of John’s finest work, we present you with five articles that we think you will refer to time and again as you look to solve problems, cut cycle times and improve the quality of the parts you mold.

Gifted with extraordinary technical know how and an authoritative yet plain English writing style, in this collection of articles Fattori offers his insights on a variety of molding-related topics that are bound to make your days on the production floor go a little bit better.

In this three-part collection, veteran molder and moldmaker Jim Fattori brings to bear his 40+ years of on-the-job experience and provides molders his “from the trenches” perspective on on the why, where and how of venting injection molds. Take the trial-and-error out of the molding venting process.

Mike Sepe has authored more than 25 ANTEC papers and more than 250 articles illustrating the importance of this interdisciplanary approach. In this collection, we present some of his best work during the years he has been contributing for Plastics Technology Magazine.

In this collection of content, we provide expert advice on welding from some of the leading authorities in the field, with tips on such matters as controls, as well as insights on how to solve common problems in welding.

Mold maintenance is critical, and with this collection of content we’ve bundled some of the very best advice we’ve published on repairing, maintaining, evaluating and even hanging molds on injection molding machines.

Thousands of people visit our Supplier Guide every day to source equipment and materials. Get in front of them with a free company profile.

NPE2024: Lowering barriers to additive manufacturing adoption in toolmaking.

Allegheny Performance Plastics turned to 1factory's cloud-based manufacturing quality control software for streamlined, paperless quality systems.    

To design the best mixers for single screws, you must completely understand how polymer moves through a mixer channel or groove.   

NPE2024: Focus is on additives for plastics including PVC and WPC industries.

At NPE2024, Novatec moves to rewrite the rules for material conveying with patent-pending smart-pump technology.  

While the major correction in PP prices was finally underway, generally stable pricing was anticipated for the other four commodity resins.

With no minimum order and an impeccable record of on-time delivery, Precision Color Compounds is becoming a force in the color masterbatch business.

Thermosets were the prevalent material in the early history of plastics, but were soon overtaken by thermoplastics in injection molding applications.

After a six-year hiatus, this year’s show was a resounding success, with meaningful technologies on display that will help processors run their businesses more efficiently.  

Key factors for the progress are innovative materials, advanced automation and precision engineering.   

Topping five other entries in voting by fellow molders, the Ultradent team talks about their Hot Shots sweep.

Serendipitous Learning Opportunities at PTXPO Underscore the Value of Being Present.

Introduced by Zeiger and Spark Industries at the PTXPO, the nozzle is designed for maximum heat transfer and uniformity with a continuous taper for self cleaning.

Ultradent's entry of its Umbrella cheek retractor took home the awards for Technical Sophistication and Achievement in Economics and Efficiency at PTXPO. 

technotrans says climate protection, energy efficiency and customization will be key discussion topics at PTXPO as it displays its protemp flow 6 ultrasonic eco and the teco cs 90t 9.1 TCUs.

Shibaura discusses the upcoming Plastics Technology Expo (PTXPO) March 28-30

Line features a single touchscreen for easy setup and operation.  

Oerlikon HRSflow’s T-Flow HRS control has launched with three models that are configurable to multiples of six zones.

NPE2024: Dukane’s new Ultrasonic Thin Wall welding system is well suited for welding applications of PP to PP TD25 painted parts.

Series offers higher output, lower melt temperatures and energy savings.  

Noting that geopolitical changes require new corporate strategies, European plastics and rubber machinery trade groups announced that incoming orders fell 22% in 2023.

System tracks, controls and saves everything from material recipes to process parameters, operator activity from logging on to start, to emergency stops and more.  

Mixed in among thought leaders from leading suppliers to injection molders and mold makers at the 2023 Molding and MoldMaking conferences will be molders and toolmakers themselves. 

After successfully introducing a combined conference for moldmakers and injection molders in 2022, Plastics Technology and MoldMaking Technology are once again joining forces for a tooling/molding two-for-one.

Multiple speakers at Molding 2023 will address the ways simulation can impact material substitution decisions, process profitability and simplification of mold design.

When, how, what and why to automate — leading robotics suppliers and forward-thinking moldmakers will share their insights on automating manufacturing at collocated event.

As self-imposed and government-issued sustainability mandates approach, injection molders reimagine their operations.

August 29-30 in Minneapolis all things injection molding and moldmaking will be happening at the Hyatt Regency — check out who’s speaking on what topics today.

Get your clicking finger in shape and sign up for all that we have in store for you in 2023.  

Molding 2023 to take place Aug. 29-30 in Minnesota; Extrusion 2023 slated for Oct. 10-12 in Indiana.

Join this webinar to learn about Conair's patented Conveying with Optimizer system, which utilizes artificial intelligence (AI) to overcome resin conveying issues automatically. Conveying with Optimizer uses valves, remote sensors and AI to eliminate conveying challenges that operators face daily throughout the plant. With this new fully-retrofittable solution, interruptions like clogged filters, air leaks, changes in density or distance, moisture changes, and operators making manual adjustments can all be eliminated with Conair's Conveying with Optimizer. Agenda: What exactly is Conveying with Optimizer? What are the benefits of using Conveying with Optimizer? What problems does Conveying with Optimizer overcome? How to upgrade your system

Cooling time is typically the longest step of the molding process. How can you make it more productive? Learn how cooling time can be turned into production time by running two molding processes simultaneously on a single molding machine. For longer cycles, this can mean twice the productivity. In this webinar, you'll learn more about the Shuttle Mold System and how to calculate its potential productivity impacts for your application. Agenda: Learn how the Shuttle Mold System can deliver value to your business See the recent technical updates made to the system Calculate the potential impact on productivity

Discover possible applications in large format printing including layup tools, transport modules, film fixation devices, design components and enclosures. These are used in various industries such as automotive, aerospace, architecture and many others. Agenda:  Possible applications in large format printing: layup tools, transport modules, film fixing devices, design components and enclosures. Process reliability and component quality in component production Pros and cons of the technology Sneak peek into current development projects—What will the large format printing of tomorrow look like?

In this webinar, Cold Jet will discuss some of the ways processors use dry ice such as in-machine mold cleaning at operating temperatures, de-flashing or de-burring parts, improving OEE scores, extending mold life, cleaning parts before painting, post-processing 3D printed parts, lowering GHG emissions, and monitoring and reporting the process. Agenda: Cold Jet Overview & Dry Ice 101 Understanding the Process and Fine-Tuning Techniques Case Studies: Applications in Plastics Monitoring the Process Exploring the Importance of Dry Ice Cleaning in an ESG Era

Finding it hard to get technical talent? Experiencing the pain of a knowledgeable, long-term employee's retirement? Learn how plastics processors are training generative AIs on their operations and unlocking the value from their tribal knowledge. Plastics processors are training generative AI models on their operations — from machine manuals to tools, polymers, procedures, maintenance records and engineering projects. Applying generative AI in the right ways can lower plastics processors' costs, improve overall equipment effectiveness (OEE) and upskill teams. In this webinar, you'll learn how to deploy AI technical assistants to your teams, what works and what doesn't, and how to use AI to build an organization that never loses tribal knowledge and fosters inter-team collaboration. Agenda: What is generative AI and how can its cognitive abilities be applied to plastics? Case study: how an injection molder trained a large language model on manuals and maintenance records to reduce downtime Case study: using generative AI in engineering teams to improve product development Live demonstration of a generative AI deep-trained on plastics knowledge Looking to the future: five predictions for an AI-augmented workforce in plastics

Turnaround time can be as low as 24 hours, although two or three days might be more typical. Rapid prototyping like this is especially useful to quickly identify critical end-use part geometries that will work in the molding process. Key components include material choice, 3D printing technology selected, use of adaptable mold bases for the mold inserts and implementation of appropriate injection molding process conditions. This presentation will review work conducted toward the assessment of a high-stiffness, high-temperature-resistant ceramic modified urethane acrylate for injection molding inserts. Agenda:  Guide for 3D-printed injection mold inserts Optimization of digital light processing (DLP) printing Compatibility with various thermoplastics Real-world application success stories

Debuting in 2010, the Parts Cleaning Conference is the leading and most trusted manufacturing and industrial parts cleaning forum focused solely on delivering quality technical information in the specialized field of machined parts cleansing. Providing guidance and training to understand the recognized sets of standards for industrial cleaning, every year the Conference showcases industry experts who present educational sessions on the latest and most pressing topics affecting manufacturing facilities today.  Discover all that the 2022 Parts Cleaning Conference has to offer!

Presented by Additive Manufacturing Media, Plastics Technology and MoldMaking Technology, the 3D Printing Workshop at IMTS 2024 is a chance for job shops to learn the emerging possibilities for part production via 3D printing and additive manufacturing. First introduced at IMTS 2014, this workshop has helped hundreds of manufacturing professionals expand their additive capabilities.  

Formnext Chicago is an industrial additive manufacturing expo taking place April 8-10, 2025 at McCormick Place in Chicago, Illinois. Formnext Chicago is the second in a series of Formnext events in the U.S. being produced by Mesago Messe Frankfurt, AMT – The Association For Manufacturing Technology, and Gardner Business Media (our publisher).

How PET evolved from a material for fibers and fabrics to a force in packaging.  

Last month’s column recounted a vital step in the commercialization of PET polyester. The accompanying figure shows one of several chemical processes used to create PET. This breakthrough involved using an organic acid containing an aromatic ring, terephthalic acid, to replace the aliphatic acids that were part of the original chemistry investigated by the Carothers’ team at DuPont. The aromatic ring boosted the performance of the resulting polymer, yielding a material with a melting point just 10° C (18° F) below that of nylon 66.

Incorporating the aromatic ring into the backbone structure of the polymer created a mixture of advantages and disadvantages. While the melting point of PET is slightly lower than that of nylon 66, the glass-transition temperature is 20° C (36° F) higher. In addition, the ester group, while polar, is much less hygroscopic than the amide group in nylon due to the absence of the hydrogen bond. And the aromatic structure reduces the susceptibility of the polymer to hydrolytic degradation, an important consideration in a material targeting fibers for clothing. Polyester exhibited less dimensional change with water absorption, which translated to a fabric that did not wrinkle when washed.

While DuPont may have passed on the initial development of polyester in favor of nylon, it obviously recognized the advantages of the new aromatic chemistry and in 1946 DuPont bought the rights to PET and developed its own product by 1950, trade named Dacron. In 1952 DuPont developed a thin-film form of the material that was trade-named Mylar. Eastman Chemical entered the market in 1958 with its own commercial offering, trade named Kodel.

Throughout the remainder of the 1950s and well into the 1960s, polyester became a dominant synthetic fiber before it fell out of favor due to complaints about comfort. Few polymers have as much of an association with changing societal tastes as polyester. The convenience of polyester fibers relative to natural fibers such as cotton and wool created a huge market in the 1950s and 1960s. This was followed by a period where polyester became associated with societal trends that made it appear out of step and obsolete (the disco scene comes to mind).

But while the material was losing market share in the world of fibers and fabrics, a new opportunity was on the horizon that capitalized on the amorphous form of the material. This was as an alternative to glass for water and carbonated beverage bottles. Here was a situation where crystallinity was not needed nor was it desired. The selling points were transparency and toughness, both of which required an amorphous polymer. Nathaniel Wyeth, a DuPont engineer, patented the technology for blow molding bottles from PET in 1973. The material proved to not only have the desired appearance and toughness needed for the application, it also possessed the strength and barrier properties needed for carbonated beverages.

This is one of several chemical processes used to create PET polyester. This breakthrough involved using an organic acid containing an aromatic ring, terephthalic acid, to replace the aliphatic acids that were part of the original chemistry investigated by the Carothers team.

Ironically, DuPont did not benefit from Wyeth’s invention when it came to sales of raw material. DuPont lacked the ability to produce a polymer with a sufficiently high molecular weight for the bottle market. Both impact performance and barrier properties required this high molecular weight, and competitors such as Goodyear and Eastman brought on the capacity needed to satisfy demand.

A story regarding Wyeth’s early experiments in blow molding the polymer illustrates the difference between the properties of crystallized PET and amorphous PET. When Wyeth first attempted to blow mold a bottle from the material, the bottle shattered into small shards because the polymer had crystallized during the reheat process, making it very brittle. The importance of heating the material only slightly above the glass transition before blowing a bottle is well understood today, but the behavior of PET was still being learned in the early 1970s, and while crystallization was necessary for use of the material in fabric, it was not at all desired in bottles. Today, the systems that preheat molded preforms carefully control the temperature in order to avoid crystallization. A walk through a bottle blow molding plant will usually reveal a gaylord of scrap preforms that exhibit a cloudy appearance, a sign that the undesirable crystallization has started.

The behavior of PET was still being learned in the early 1970s ,and while crystallization was necessary for use of the material in fabric, it was not at all desired in bottles.

One of the consequences of the presence of the aromatic ring in the PET polymer backbone was a slower rate of crystallization than was typical in nylons. Because PET was used primarily in fibers, processing the material allowed for the achievement of an appropriate level of crystallization with all the associated beneficial properties. But the crystallization process was slow for the growing world of injection molded products. So, while nylon became an increasingly popular material for injection molded articles in the 1950s to the 1970s, PET remained a material for fibers and film, where the process of crystallization was slower but could be controlled through the manufacturing process.

In the amorphous state, PET polyester was relegated to applications that could accommodate the limited mechanical performance of a material with a glass-transition temperature of 80-85 C (176-185 F). Parts are injection molded in amorphous PET, but the application temperature is limited to about 65-70 C (149-158 F). The properties of amorphous PET present another challenge that can limit the maximum use temperature to an even greater degree. Because amorphous PET has one of the lowest glass-transition temperatures of any commercial amorphous polymer, it is susceptible to a phenomenon known as physical aging.

This was discovered in the early days of the plastic bottle industry when bottles stored at elevated temperatures exhibited a substantial decline in ductility in a matter of weeks. At the time there were only two mechanisms that were known to contribute to a decline in toughness—crystallization and polymer degradation. Neither of these could explain the loss in impact resistance of the PET bottles. But in 1978, L.C.E. Struik published a landmark paper outlining the mechanism of physical aging, a process in amorphous polymers that involves the collapse of the polymer chains into the free volume that exists between the chains. This creates stronger intermolecular forces that result in an increase in strength and stiffness but a decline in ductility over time.

Today amorphous PET accounts for the majority of PET resin consumed, due to over half a trillion bottles produced annually.

The rate at which physical aging occurs is dependent upon temperature, and studies by Eastman have shown that with each increase of 10° C the rate of physical aging in amorphous PET increases by a factor of nearly 10 (9.8 to be precise). My own experiments using accelerated aging techniques have confirmed this. And since the relationship is exponential, an increase of 30° C will increase the rate of physical aging by 9.83 or 941. So, a change in mechanical properties that might take a few years at room temperature can occur in a matter of days in a hot warehouse.

Today amorphous PET accounts for the majority of PET resin consumed, due to over half a trillion bottles produced annually. The ability of the polymer to be either amorphous or semi-crystalline is illustrated by the fact that much of the recycled PET from bottles is converted to fiber for clothing and other fabrics. But for applications that require heat resistance, such as under-the-hood environments, PET must be semi-crystalline. And most of these types of parts are produced by injection molding. This created problems for those wishing to use PET since the slow crystallization rate of the polymer resulted in long cycle times and the need for very high mold temperatures.

In 1978, DuPont solved the problem of slow crystallization through nucleation using a combination of additives and fillers to introduce a line of products known commercially as Rynite. But almost a decade earlier, another type of polyester had been introduced that did not exhibit the problems with slow crystallization and had already made inroads into the engineering thermoplastics market. This was PBT, a material with a structure similar to PET. The ability to achieve faster crystallization was due to a small change in the molecular structure that brought with it some compromises. PBT also revealed the potential for a remarkable level of versatility in polyesters, a topic we will cover in our next installment.

ABOUT THE AUTHOR: Michael Sepe is an independent materials and processing consultant based in Sedona, Ariz., with clients throughout North America, Europe, and Asia. He has more than 45 years of experience in the plastics industry and assists clients with material selection, designing for manufacturability, process optimization, troubleshooting, and failure analysis. Contact: (928) 203-0408 •mike@thematerialanalyst.com

The polymers we work with follow the same principles as the body: the hotter the environment becomes, the less performance we can expect.

First find out if they are the result of trapped gas or a vacuum void. Then follow these steps to get rid of them.

Let’s take another look at this seemingly dull but oh-so-crucial topic.

Flashing of a part can occur for several reasons—from variations in the process or material to tooling trouble.

The industry has learned a lot about the advantages and disadvantages of polycarbonate during its more than 60-year history, and it would be difficult to imagine a world in which it did not exist.   

How polycarbonate came about, virtually simultaneously, through the efforts of two industry giants.

The history of nylons and polyesters are intertwined, and it takes some knowledge of chemistry to understand why.  

Tracing the History of Polymeric Materials: PET | Plastics Technology

Pet Resin Future Demand Plastics Technology covers technical and business Information for Plastics Processors in Injection Molding, Extrusion, Blow Molding, Plastic Additives, Compounding, Plastic Materials, and Resin Pricing. About Us