Foreword

CONOR CARLIN

To simplify the complex is the task of the expert. To ensure that the expert does not over-simplify, we rely on the practitioner. We marry the theoretical and the empirical, so to say. When speaking about thermoforming-the process by which we heat and form plastic in its rubbery state (as opposed to injection molding where plastics are processed in their molten state)-we must navigate both the scientific literature and the oral tradition. This juxtaposition of theory vs. practice, therefore, compares the mathematics and physics of polymer rheology with the hard-bitten, "black art," commercial application of such theories.

To paraphrase Newton, today's practitioners of thermoforming stand on the shoulders of giants, whether or not they have read Throne1,2 or Illig.3 These seminal texts, though written in the late 1980s and early 1990s, arrived more than 40 years after the first patents were filed for methods of vacuum snap-back forming. The first thermoforming machines appeared in the early 1950s on both sides of the Atlantic, performing what we would call today, "heavy gauge sheet forming." Those pioneering practitioners were the first to harness the early promise of new polymeric materials and create innovative manufactured parts that replaced heavier, traditional materials including glass, ceramics, and metals. In subsequent decades, organizations such as the Thermoforming Division of the Society of Plastics Engineers (SPE) have been publishing articles and convening symposia since the 1970s, giving us a rich vein of history to mine as we seek to understand the evolution of this most practical of plastics processes.

Mechanical engineering and materials science converge neatly in the thermoforming process. To design molds with adequate turbulent flow requires knowledge of metallurgy and fluid dynamics. To produce thousands or millions of repeatable parts requires machine engineering and programming expertise equivalent to any other modern manufacturing process. When we stop to consider, however, that the primary input-plastic sheet-is subject to variation (in basic quality, orientation, storage conditions, and more) beyond the thermoforming practitioner's control, we must recognize the skill of the operator. We might even consider them a conductor, working to perfect a symphony of materials, equipment, and processes.

We must recognize, therefore, that thermoforming remains less precise than its plastics processing cousins such as injection molding or extrusion blow molding. This comparative lack of precision is, however, adequately compensated through efficiency, scale, and cost. We leave it to Throne, Dharia, and others for deeper physical and rheological discussions. What concerns us in the second edition of Advanced Thermoforming is the evolution of thermoforming techniques, including pre- and postprocessing, and the steady growth of markets and applications that rely on stretching and cooling polymers in their viscoelastic state.

Since the first edition of Engelmann's Advanced Thermoforming: Methods, Machines and Materials, Applications and Automation in 2012, two major events (perhaps one event and one philosophical evolution) have impacted the thermoforming world in such a way as to merit inclusion in this short commentary. The first and most obvious is the global pandemic. The second, though arguably more profound, is the public's changing perspective on plastic and its role in sustainable development.

At the time of writing, we are still dealing with the effects of supply chain disruptions stemming from an explosion in consumer demand after more than a year of global lockdowns. This is not the forum to dive into continuing financial complications including inflation and related war-induced energy shortages. It is sufficient to say that the protective properties of polymers were illustrated in stark relief to millions of people in a shockingly short amount of time. Thermoforming companies, in North America and elsewhere, were granted "essential worker" status due to the massive increase in demand for face masks, face shields, and take-out containers for food. Since the depths of the pandemic, however, the dearth of operators and shift workers in the thermoforming (and many other manufacturing) sectors has spurred an unprecedented push for automation. Though it is true that higher-cost regions such as northern Europe and Japan have integrated automated parts handling systems for years, other regions have been slower to make capital investments because they had access to a readily available pool of labor. Automation, defined either as repeatable systems meant to replace manual labor or as machine intelligence designed to reduce operator input, is therefore a critical aspect of today's thermoforming technology.

To the second event, or evolution: the public's understanding of plastics has become much more complex and looks set to resist simple explanations. The era of social media and its polarizing effects on conversation does not lend itself to nuanced debate, much less a detailed understanding of carbon accounting or life cycle assessments, both of which suggest plastics have environmental benefits in excess of their (measured) costs. Will there really be more plastics than fish in the sea? Given the difficulties in measuring both, it seems like a lazy projection at best. Both the BBC (United Kingdom) and CBC (Canada) have investigated the oft-repeated claims from the Ellen MacArthur Report4 and found that the calculations are inexact and virtually unprovable. A meme has gone viral, later was debunked, but still is repeated frequently in media reports and social media posts, including-dispiritingly-at professional industry events.

We can agree that pollution of any type is a net negative, one that causes environmental and ecological harm. One result of the broader public awareness of sustainability and the philosophy of sustainable materials management or "circular economy principles" is a deeper appreciation of plastics' forms and functions. The growth of non-fossil-based plastics such as starch-based polylactic acid (PLA) or "drop-in" materials like Braskem's biobased green polyethylene5 suggests that a material's function is at least as important as its origins. Moreover, the ability to thermoform these new materials using the most modern machine and tool technologies means that the final articles remain as light as possible, further improving their overall environmental footprint.

Thermoforming, then, might serve as a useful microcosm of how we struggle to be comfortable with ambiguity. From the doctorate-level dissertations at renowned academic establishments such as the Fraunhofer Institute or the University of Massachusetts at Lowell, to the sweaty production halls of Southeast Asia where workers churn out millions of food and beverage packages, we have a kaleidoscopic view of this most practical and efficient plastics process. It forces us to integrate economic realities and human resources in a global market where demands for convenience seem to grow exponentially. It is, perhaps frustratingly, complex and simple at the same time.

Conor Carlin

SPE President (2024-2025)

Plymouth, MA

BEN HO

China is a booming market for thermoforming products due to high demand of packaging for non-food and food packages under fast urbanization and needs for rapid growth of "take-out service" for restaurants and supermarkets. Therefore, thermoformed products become popular in such packages. We need more and more professional and experienced technicians and operators in thermoforming industry in China.

Since 2018, Mr. Sven Engelmann has been working with China Thermoforming Association (CTFA) to give his lectures at our Thermoforming seminars and classes in China.

Advanced Thermoforming is a practical thermoforming guide to help operators and technicians at their thermoforming machines and tools. I do hope that the second edition of Advanced Thermoforming will be successfully published and sold in China to help promote better knowledge of thermoforming techniques and understanding.

Ben Ho

President of China Thermoforming Association (CTFA)

Haining, China

MICHEL PY

The world, having faced a pandemic like never before, must now renew itself and face new challenges:

• the challenge of plastic bashing
• energy costs
• raw material costs and their enormous volatility

European consumers expect manufacturers to make a real ecological commitment to protect our planet. They are asking for a real use of the circular economy of green recycled products using renewable bioresources.

European and governmental commitments oblige manufacturers to review their production and transformation methods to include recycled materials at minimum levels of 30% for packaging. Other areas will follow.

We are involved in developing products that allow us to regulate climate fluctuations, water regulation, water temperature regulation, and the reduction of petroleum product use by using more and more recycled products or bioplastics.

European economic models still need to be reviewed when facing costs 5 times higher than in the United States and 10 times higher than in China

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