Consider the various combinations of properties you might find in different types of materials. This variation is what makes one material different from another. These properties may include:
- Electrical properties,
- Thermal properties,
- Magnetic properties,
- Flexibility or rigidity, and
- Resistance to damage.
By manipulating and exploiting such properties, chemical engineers are able to develop and fabricate an ever-expanding array of desirable, imaginative, and revolutionary new end products.
It is hard to go through an average day without coming into contact with at least some of the many different forms of plastic that currently abound. But it was only about 100 years ago that the first true plastic to be commercialized, Bakelite, was invented. Since then, owing to the adaptability of the physical properties of plastic, the development and the fabrication of plastic products have accelerated rapidly.
At our fingertips, meeting our needs
Plastics are widely popular materials because of the many desirable characteristics they possess, such as:
- Broad resistance to chemicals,
- Functional thermal and electrical insulation,
- Light weight with varying degrees of strength, and
- Processing flexibility.
Working to achieve unique and innovative combinations of these properties, chemical engineers are able to create a great variety of materials and products that affect, advance, and improve our daily lives in countless ways.
Creating, improving, and enhancing desirable end products
Plastics are composed of long, chain-like molecules produced when individual chemical compounds are linked together in a process called polymerization.
In general, by altering the chemical composition and varying the processing methods, it is possible to modify the physical properties of a plastic and thus to control its behavior. Most plastics are produced by carefully formulating a mixture of polymer resins with a variety of performance-enhancing fillers, chemical additives, and reinforcing agents. The combination of these materials is what gives the particular polymer blend its desired characteristics, including:
- Improved tensile and impact strength;
- Improved flame retardance;
- Increased conductivity and antistatic, antibacterial, and fungicidal capabilities; and
- Increased resistance to oxygen, ozone, or ultraviolet-radiation damage.
Because of the broad flexibility of their properties, today’s plastics are widely used in consumer, industrial, medical, electrical and electronic, packaging, building construction, and other applications. Their uses range from the everyday—children’s toys, beverage bottles, clothing, and carpeting and packaging materials—to the more esoteric—industrial machine components, automotive parts, biomedical implants, and medical instruments.
Environmentally focused bio-based plastics
Historically, plastics have been produced from materials derived from hydrocarbon sources—specifically chemicals produced from petroleum, natural gas, and coal.
More recently, however, the chemical-engineering community has been working on “bio-based” plastics produced from such renewable raw materials as corn, soybeans, and other agricultural and forest crops. This results in “greener” plastics that not only help reduce society’s reliance on fossil fuels but are also more biodegradable - breaking down faster in landfills and producing only carbon dioxide, water, and nontoxic biomass—compared with traditional, hydrocarbon-based plastics. Promising early products include garbage bags and baby diapers, with more to come.
Computers have become thoroughly ingrained in our daily lives. And so the demand for smaller, faster, smarter, and cheaper computers has escalated. Revolutionary advances in materials science have been largely responsible for the evolution of progressively smaller semiconductor chips that boast ever-increasing speed, greater memory, and broader functionality.
The revolution is going strong
As a society we have skyrocketed out of the Industrial Revolution straight into the Computer Revolution. And it has thoroughly embraced us. Computers are found in just about every aspect of modern life, enabling key technologies in such areas as education, business, industry, and communications. And as our dependence grows, we demand that our electronic devices become smaller, faster, smarter, and cheaper.
Evolution of the semiconductor chip
Semiconductor chips provide the backbone for modern computing systems. They are complex microelectronic circuits composed of a base material with electrical conductivity greater than an insulator but less than a conductor. The typical base material is silicon, although germanium is also used.
Chemical engineers are deeply involved in developing specialized materials and complex chip-manufacturing processes. Their constant quest is for progressively smaller semiconductor chips and computer components that provide ever-increasing speed, greater memory, and broader functionality.
An application of specialized knowledge
In the creation of progressively advanced semiconductor chips and other computer components, chemical engineers apply their expertise in:
- Kinetics and thermodynamics in the crystallization of silicon wafers;
- Polymer science in the development of patterned photoresist coatings;
- Heat transfer to maintain desired temperatures and manage heat buildup during the chip-making process; and
- Mass transfer to improve etching of complex semiconductor-chip patterns and the plating of electronic microchannels.
We have come to depend on instantaneous global telecommunications and data transmission. This reliance has come about in large part because of the contributions of chemical engineers working with fiber-optic cables. The enhancement of optical properties and the reduction of inherent brittleness have allowed many millions of miles of fiber-optic cable to be put to practical use.
Connecting at the speed of light
Fiber-optic cables are bundles of long, thin glass fibers, each narrower than a human hair. These glass strands transmit light signals over thousands of miles. Total internal reflection (100% of the light is reflected off the walls of the fiber, so no light is lost) guides light through these cables, enabling it to bend around corners and reach its destination very rapidly. This allows for real-time telecommunications and digital data transfer, without which modern communications would be impossible. Affected areas would include:
- Modern “land-line” telephones,
- Cable television,
- Videoconferencing, and
- Electronic commerce.
Creating a strong, flexible backbone
Today, millions of miles of fiber-optic cables form the backbone of our instantaneous, worldwide voice-, video-, and data-transmission systems. But before this technology could become a reality, a reliable process for fabricating flexible fiber-optic cables had to be developed.
Although drawing glass into small-diameter fibers is a straightforward process, the thin glass fibers produced are very brittle and fracture easily. To solve this problem chemical engineers invented a process (called modified chemical vapor deposition, or MCVD) that coats the drawn glass fibers with a specialized polymer. This coating maintains the optical properties needed to guide light and data through the fibers, and even more important, it prevents the fibers from fracturing, no matter how severely they are bent.
Innovative biocompatible materials have helped improve our quality of life and lengthen our life span. Chemical engineers have been at the forefront of these advances, creating materials for use in such familiar items as the ubiquitous gel cap, as well as in less common items, such as artificial joints, vascular meshes, and the membranes used in kidney dialysis.
Fanttastic voyages into the human body
Ingenious advances in nearly every aspect of modern medicine have been achieved through the use of biocompatible materials developed by the chemical-engineering community. These discoveries have helped extend and enhance our quality of life, improve disease diagnosis and treatment, and ease pain and suffering.
In the field of biomedicine, chemical engineers focus their efforts on the discovery and optimization of biocompatible materials. For use within the human body these specialized materials must be:
- Well tolerated, and
- Damage and degradation resistant.
Turning materials into medical marvels
Among the wide variety of biocompatible materials that have been developed for use today, those used in vivo, or inside the body, include the following:
- Vascular grafts used to repair or reinforce existing veins and arteries (fabricated from specialized polyester, they are lightweight yet strong);
- Stents used to facilitate drainage and reinforce weak arterial tissue (they are fabricated from specialized stainless-steel alloys that are both strong and lightweight);
- Spinal, cardiovascular, and ophthalmic implant devices made from a variety of specialized polymers, ceramics, and metals; and
- Artificial knees and hips (fabricated from combinations of biocompatible polymers and surgical titanium, they are rugged yet still highly flexible).
In addition to in vivo materials significant breakthroughs have also been made in materials used in vitro, or outside of the body, such as dialysis membranes used in artificial kidney machines.
For patients who have regained comfort, flexibility, and mobility and have seen their quality of life and their prospect for longevity increase, these pioneering materials breakthroughs are truly miracles of modern medicine.
Getting drugs to where they work best
Chemical engineers have also led the way in creating innovative materials that have been used to deliver drugs more effectively. The goal is to improve the precise targeting and delivery of therapeutic agents to maximize the efficacy of the drug while minimizing any potential side effects. These inventions range from the common gel cap to complex controlled-release mechanisms that use tiny hollow spheres made from specialized polymers.