My Science School

The first songwriter to receive the Nobel Prize, Bob Dylan courted controversy over his win. Firstly, he did not accept the award till 2017. Then, he was criticized for plagiarizing parts of his lecture from an online study guide. The lecture is the only requirement to claim the 8m kronor prize money.

The Academy praised him for “creating new poetic expressions within the great American song tradition”. Despite this, Dylan failed initially to acknowledge the honour, and was branded “impolite and arrogant” by one member of the Academy for failing to respond.

Dylan finally spoke about being awarded the Nobel Prize over two weeks after it was announced he was receiving the honour.

“It’s hard to believe,” he told the Daily Telegraph in an interview.

Asked why he chose to stay silent about it for so long, Dylan only replied: “Well, I’m right here.”

 

Picture Credit : Google

Another incident in 2017 showed how the awards platform can be used for doing well. Actress Meryl Streep used her acceptance speech for the Cecil B. DeMille Award during the Golden Globes to call out the then President-elect Donald Trump for trampling on the freedom of the press and reminded those in Hollywood of the responsibility of empathy.

Streep voiced her heartbreak at Trump’s mocking of a disabled reporter. “And this instinct to humiliate when it’s modeled by someone in the public platform, by someone powerful, it filters down into everybody’s life, because it kind of gives permission for other people to do the same thing,” she said. “Disrespect invites disrespect. Violence incites violence.” Indeed, Streep’s speech remains relevant even today.

 

Picture Credit : Google

A Pixel is a tiny dot of color, which, together with millions of other dots, makes up a picture on a computer or television screen. It is short for "picture element". A pixel is the smallest unit of a digital image or graphic that can be displayed and represented on a digital display device.

A pixel is the basic logical unit in digital graphics. Pixels are combined to form a complete image, video, text or any visible thing on a computer display. A pixel is also known as a picture element.

A pixel is represented by a dot or square on a computer monitor display screen. Pixels are the basic building blocks of a digital image or display and are created using geometric coordinates. Depending on the graphics card and display monitor, the quantity, size and color combination of pixels varies and is measured in terms of the display resolution.

For example, a computer with a display resolution of 1280 x 768 will produce a maximum of 98,3040 pixels on a display screen. Each pixel has a unique logical address, a size of eight bits or more and, in most high-end display devices, the ability to project millions of different colors.

The pixel resolution spread also determines the quality of display; more pixels per inch of monitor screen yields better image results.

 

Inside the processing unit of a computer are collections of integrated circuits (microchips) and other components, usually positioned on circuit boards. There are also slots for floppy disks and CDs to be inserted, a “hard disk” on which data is stored, and perhaps devices such as fans to keep the components cool. Portable computers also have space for a battery, which can be recharged.

It is imperative to understand the name and function of each component in a computer in order to understand how it functions as a whole. Attempt to always remember that a computer is based off the human body and functions in the same way. You cannot expect to understand the human body without first understanding its organs and their functions. A computer is composed of components in the same way that the body is composed of organs that together work to make the body or computer function. A basic computer has at least 8 basic components which include a computer case or tower, motherboard, Central Processing Unit (CPU), Power Supply Unit (PSU), Random Access Memory (RAM), hard drive (HDD), Graphic Processing Unit (GPU) and some type of optical drive which would be your CD/DVD drive. These 7 components are the backbone of every healthy, functioning computer.

Motherboards

Motherboards often referred to as a logic board, main board or “mobo” for short, are the “back-bone” of the computer. Its purpose is to connect all the parts of the computer together and make everything centralized using its printed circuit board. The central processing unit, hard drives, memory, graphic processing unit, printers, and other ports all connect to the computer directly or via special cables that attach on to the motherboard. When you plug in a USB or thumb drive to a computer you are actually plugging it directly into the computer!

Power Supply

True to its name, the power supply powers all other components of the machine. It usually plugs into the motherboard to power the other parts. The power supply connects to either an internal battery (on a laptop) or a plug for an outlet (on a desktop).

Central Processing Unit (CPU)

A CPU, sometimes referred to as a computer's brain, is the workhorse of the machine. It performs the calculations needed by a system, and can vary in speed. The work that a CPU does generates heat, which is why your computer has a fan inside. A more powerful CPU is necessary for intense computer work like editing high-definition video or programming complex software.

Random-access Memory (RAM)

RAM is temporary memory. Whenever you open up a Microsoft Word window, your computer places it in RAM, and when you close the window, that RAM is freed. Since RAM is volatile, its contents are lost if the machine loses power. This is why you lose a Word document when the power goes out if you didn't save it.

Hard Disk Drive / Solid State Drive

Since RAM is temporary, your computer needs a place to store data permanently. That's where the hard drive comes in. The traditional hard drive consists of several spinning platters with an arm that physically writes data to the disk. However, these drives are slow and are starting to be replaced by the faster solid-state drives.

Video Card

A video card is a dedicated unit for handling the output of images to a display. Video cards have their own dedicated RAM for performing these functions. A high-end video card is required to process extremely intense visual functions, such as computer drafting by engineers. Like many components, many types of video cards are available with varying power and prices.

Optical Drives

Though less common than they used to be, many machines still have an optical drive for reading CDs and DVDs. These can be used to listen to music or watch movies, place information onto a blank disc, or install software from a disc. Since most software nowadays is installed from the internet instead of using discs, these aren't as important as they once were, especially on laptops.

Input and Output Devices

Depending on your particular computer, you can connect a variety of devices to send information into it or out of it. Common input devices include mice (touchpads on laptops), keyboards, and webcams, while output devices consist of monitors, printers, and speakers. Removable media such as flash drives and SD cards can also be used to transfer data between computers.

An optical mouse is technologically much more advanced than a mechanical mouse. Unlike the latter, an optical mouse is completely electronic and therefore has no moving parts. It consists of an LED (that generates the signature red light), a light-detector chip, a switch mechanism and a few other simple components. Some mice have another LED that lights up a plastic strip installed at the back of the mouse as an indication of the mouse’s operation.

The LED installed at the bottom of the mouse emits a bright light in the downward direction. Since a mouse is usually used on plain surfaces, the light bounces back from the surface and enters a photocell that’s also mounted on the bottom, almost next to the LED. This photocell has a frontal lens that magnifies any light reaching it. As you move the mouse around, the pattern of the reflected beam changes; this is then used by the light-detector chip to figure out how and in which direction you’re moving the mouse.

Some optical mice have two LEDs. The first one shines light down onto the desk. The light from that is picked up by the photocell. The second LED lights up a red plastic strip along the back of the mouse so you can see it's working. Most optical mice also have a wheel at the front so you can scroll pages on-screen much faster. You can click the wheel too, so it functions like the third (center) button on a conventional ball mouse.

Optical mice are much lighter and faster than mechanical ones, and have therefore gained enormous popularity all over the world. With improvements in technology, newer and even more advanced mice – that address issues like ergonomics and the health of the user – are taking center stage. The choice of the right variant rests with the user, but one thing remains universally true – computers and mice shall always remain inseparable.

A Mouse is a device for giving the computer information (an input device). When the mouse is pushed around on a mat, a pointer on the computer’s screen is moved, indicating how data needs to be changed, moved or processed. Tiny beams of light inside the mouse shine through slotted wheels. The ball of the mouse moves as it is pushed across the mat, and the beams of light are interrupted in a way that tells the computer the direction that the mouse is moving.

A mouse is something you push along your desktop to make a cursor (pointing device) move on your screen. So what a mouse has to do is figure out how much you're moving your hand and in which direction. There are two main kinds of mice and they do this job in two different ways, either using a rolling rubber ball (in a ball-type mouse) or by bouncing a light off your desk (in an optical mouse).

How does a mouse like this actually work? As you move it across your desk, the ball rolls under its own weight and pushes against two plastic rollers linked to thin wheels. One of the wheels detects movements in an up-and-down direction (like the y-axis on graph/chart paper); the other detects side-to-side movements (like the x-axis on graph paper).

How do the wheels measure your hand movements? As you move the mouse, the ball moves the rollers that turn one or both of the wheels. If you move the mouse straight up, only the y-axis wheel turns; if you move to the right, only the x-axis wheel turns. And if you move the mouse at an angle, the ball turns both wheels at once. Now here's the clever bit. Each wheel is made up of plastic spokes and, as it turns, the spokes repeatedly break a light beam. The more the wheel turns, the more times the beam is broken. So counting the number of times the beam is broken is a way of precisely measuring how far the wheel has turned and how far you've pushed the mouse. The counting and measuring is done by the microchip inside the mouse, which sends details down the cable to your computer. Software in your computer moves the cursor on your screen by a corresponding amount.

There are various problems with mice like this. They don't work on all surfaces. Ideally, you need a special mouse mat but, even if you have one, the rubber ball and its rollers gradually pick up dirt, so the x- and y-axis wheels turn erratically and make the pointer stutter across your screen. One solution is to keep taking your mouse to pieces and cleaning it; another option is to get yourself an optical mouse.

Traditional mice have a rubber ball inside them. Open one up and you can see the heavy ball clearly and the spring that keeps it in position.

(1) Switch detects clicks of left mouse button. (2) Switch for middle button. (3) Switch for right button. (4) Old-style connection to PS/2 socket on computer. (5) Chip turns back-and-forth (analog) mouse movements into numeric (digital) signals computer can understand. (6) X-axis wheel turns when you move mouse left and right. (7) Y-axis wheel turns when you move mouse up and down. (8) Heavy rubber wheel. (9) Spring presses rubber ball firmly against X- and Y-axis wheels so they register movements properly. (10) Electrolytic capacitor (11) Resistors. (See picture):

Inside a computer is a “hard disk”, which is able to store information (data) even when the machine is turned off. There are also two other kinds of storage in a computer. ROM (read-only memory) stores the instructions that tell the computer how to start working when it is first switched on. RAM (random-access memory) stores data that is in use. To make sure that data is permanently stored, it must be “saved” on the hard disk before the computer is switched off.

At the core of the computer is the central processing unit or CPU, the source of control that runs all programs and instructions. In order to function, computers use two types of memory: primary and secondary. The main storage is the primary memory, and data and programs are stored in secondary memory.

Data is stored as lots of binary numbers, by magnetism, electronics or optics. ... The computer's operating system, for example, contains instructions for organizing data into files and folders, managing temporary data storage, and sending data to application programs and devices such as printers.

Magnetic storage is commonly used on the hard disc drives found on most computers. Information is stored using positive and negative magnetic charges to correspond with the 1s and 0s noted above. Optical discs like CDs and DVDs store information as binary code that can be read by an optical sensor in a disc drive.

The hardware of a computer consists of all the parts you can hold in your hand: the machine itself and any other machinery that is attached to it. But a computer by itself is simply a collection of components. In order to do anything at all, it must be programmed (given a set of instructions). Programs are what are known as software. They are written in a code that a computer can “understand” and act upon. The codes in which programs are written are sometimes called languages.

Computer hardware is any physical device used in or with your machine, whereas software is a collection of programming code installed on your computer's hard drive. In other words, hardware is something you can hold in your hand, whereas software cannot be held in your hand. You can touch hardware, but you cannot touch software. Hardware is physical, and software is virtual.

For example, the computer monitor you are using to read this text, and the mouse you are using to navigate this web page are computer hardware. The Internet browser allowing you to view this page, and the operating system that the browser is running on are considered software. A video card is hardware, and a computer game is software. You can touch and feel the video card, and the computer uses it to play a computer game, but you cannot touch or feel the programming code that makes up the computer game.

All software utilizes at least one hardware device to operate. For example, a video game, which is software, uses the computer processor (CPU), memory (RAM), hard drive, and video card to run. Word processing software uses the computer processor, memory, and hard drive to create and save documents.

Hardware is what makes a computer work. A CPU processes information and that information can be stored in RAM or on a hard drive. A sound card provides sound to speakers, and a video card provides an image to a monitor. Each of these are examples of hardware components.

The central processing unit (CPU) is the “brain” of a computer, where its calculations take place. It is contained within a larger processing unit. In order to give instructions to the computer, input devices, such as a keyboard, stylus, mouse, or joystick, are needed. The monitor enables the user to see data on a screen. Many other machines, called peripherals, can also be connected to the computer. They include printers, scanners and modems.

The Central Processing Unit

The central processing unit, or CPU, can be thought of as the "brain" of a computer. Using a combination of arithmetic functions, logic processes and input/output commands, the CPU receives instructions from various computer programs in use and executes them as needed. The modern CPU exists in the form of a microprocessor, which features a single integrated circuit design. This is a dramatic departure from the earliest CPU units, which featured a transistor-based construction. Compared to the CPUs used in the second half of the 20th century, modern hardware is highly efficient, portable and relatively inexpensive to manufacture.

The Motherboard

A CPU can’t achieve its intended purpose without the assistance of the motherboard. The motherboard is a printed circuit board, or PCB, found inside a computer which not only hosts the CPU but also acts as a connected gateway to various other computer peripherals, including sound cards, hard drives, video cards and so on. The motherboard hosts a number of sockets into which microprocessors, such as the CPU, can be plugged. The motherboard is also connected to the computer's power supply and distributes electrical voltage to the attached components. Simply put, a motherboard provides a critical platform on which the rest of a CPU's hardware can operate. Without the motherboard in place, a computer couldn't function.

Hard Drives and RAM

The hard drive often shortened to HD, stores data which can then be accessed by various other programs at any given time. Hard drives provide users with various levels of storage capacity, with more expensive units often providing greater space for data storage and faster rates of data transmission.

It's somewhat easy to confuse the function of the hard drive with that of random access memory, or RAM. Unlike a hard drive, RAM is composed of a series of chips which allow for temporary data storage only. Whereas a hard drive will continue to store data even after a computer has been powered off, RAM will be cleared. RAM is often used to act as a holding zone for open files or critical data that a program may need to access intermittently during use. RAM should not be thought of as storage, per say, but instead as a "place holder" for valuable information. Nevertheless, it remains one of the 4 main parts of a computer that is still in use today.

Monitor

The monitor works with a video card, located inside the computer case, to display images and text on the screen. Most monitors have control buttons that allow you to change your monitor's display settings, and some monitors also have built-in speakers.

Keyboard

The keyboard is one of the main ways to communicate with a computer. There are many different types of keyboards, but most are very similar and allow you to accomplish the same basic tasks.

Mouse

The mouse is another important tool for communicating with computers. Commonly known as a pointing device, it lets you point to objects on the screen, click on them, and move them. There are two main mouse types: optical and mechanical. The optical mouse uses an electronic eye to detect movement and is easier to clean. The mechanical mouse uses a rolling ball to detect movement and requires regular cleaning to work properly.

In the early 1830s, an English inventor called Charles Babbage (1792-1871) designed the first programmable computer and began to build it. In fact, he never finished, as the machine was extremely complicated! This computer was entirely mechanical. Over a hundred years had to pass before the electronic components that are used today were invented.

We could argue that the first computer was the abacus or its descendant, the slide rule, invented by William Oughtred in 1622. But the first computer resembling today's modern machines was the Analytical Engine, a device conceived and designed by British mathematician Charles Babbage between 1833 and 1871. Before Babbage came along, a "computer" was a person, someone who literally sat around all day, adding and subtracting numbers and entering the results into tables. The tables then appeared in books, so other people could use them to complete tasks, such as launching artillery shells accurately or calculating taxes.

It was, in fact, a mammoth number-crunching project that inspired Babbage in the first place [source: Campbell-Kelly]. Napoleon Bonaparte initiated the project in 1790, when he ordered a switch from the old imperial system of measurements to the new metric system. For 10 years, scores of human computers made the necessary conversions and completed the tables. Bonaparte was never able to publish the tables, however, and they sat collecting dust in the Academia des sciences in Paris.

In 1819, Babbage visited the City of Light and viewed the unpublished manuscript with page after page of tables. If only, he wondered, there was a way to produce such tables faster, with less manpower and fewer mistakes. He thought of the many marvels generated by the Industrial Revolution. If creative and hardworking inventors could develop the cotton gin and the steam locomotive, then why not a machine to make calculations [source: Campbell-Kelly]?

Babbage returned to England and decided to build just such a machine. His first vision was something he dubbed the Difference Engine, which worked on the principle of finite differences, or making complex mathematical calculations by repeated addition without using multiplication or division. He secured government funding in 1824 and spent eight years perfecting his idea. In 1832, he produced a functioning prototype of his table-making machine, only to find his funding had run out.

Plastic materials can be shaped very efficiently by machines, so plastic objects are cheaply made in great numbers. Some people think that this has contributed to the “disposable society”, where we are inclined to throw something away when it is worn or broken, instead of trying to mend it, as would have happened in the past. They warn, too, that most plastics do not easily decay, so our thrown-away food cartons and shopping bags will remain to pollute the planet for years to come. However, plastics have also brought great benefits, playing a part in so many aspects of our lives that it is difficult now to imagine the world without them.

There has been no material more revolutionary than modern plastic. Used in almost every single industry in a vast range of ways thanks to its versatility, high durability and ability to be molded into whatever shape necessary, no material has changed (and in many ways, shaped) the world like plastic has.

Since then, plastic took over the world. Thanks to its ability to remain sterile while acting as a container, plastic was used in the formation of bottles for items such as milk, which no longer had to be delivered in glass bottles. In the food industry, plastic has had an amazing, incalculable effect. Raw meat can be kept in plastic packaging to prevent potential diseases, while the use of plastic trays to keep food fresh has helped to diminish waste in stores.

Plastic has had a profound impact on almost every industry it has touched. Medicine benefited greatly from the development of the disposable plastic syringe in 1955, for instance. In fact, if we were to swap plastic for any other material to be used in the same way, it would exponentially increase greenhouse gases being emitted. The effect plastic has had on the nascent industrial world cannot be denied.

Basically, plastics are lightweight, inexpensive and high in quality. Before, buckles are made of metal and are heavier compared to the quick release buckles we use today. Weight really matters a lot in any industry because of storage and shipping issues. It is far easier and lighter to ship plastic buckles than metal buckles, making it more ideal for manufacturers, suppliers, and dealers alike.

Although plastics are considered cheaper, we cannot deny the quality it can offer. Aside from the fact that it is easier to store and ship, manufacturing plastics allow for more flexibility and creativity of the part of plastic manufacturers. Since it is highly malleable, plastics are very easy to customize so practically, any design brought to mind can be manufactured in no time at all!

Take for example plastic spoons and forks. If you will account the cost of damaged or lost utensils, values are probably going to stack up but if you will be using the plastic type, it would the most economical option. Aside from that, you don’t have to wash it with soap and water again and again because it is disposable. Same economics may be applied to quick release buckles too.

Another reason why plastics are preferred over metal is due to is hygienic qualities. It helps prevent the spread of diseases due to improperly cleaned metal cutlery. Now that you know the advantages of using plastics, can you imagine a day in your life without using it more than once? Is it even possible to run your day without it?

Starch, rubber, wool, silk and hair are all natural polymers. Their molecular structure, under the right conditions, makes them strong and flexible.

A polymer is basically synthesized by joining small molecules or substances into a single giant molecule by a chemical process. The small molecules which are used in synthesizing a polymer are called as monomer. Natural Polymers are those substances which are obtained naturally. These polymers are formed either by the process of addition polymerization or condensation polymerization.

Polymers are extensively found in nature. Our body too is made up of many natural polymers like nucleic acids, proteins, etc. The Cellulose is another natural polymer which is a main structural component of the plants. Most of the natural polymers are formed from the condensation polymers and this formation from the monomers, water is obtained as a by-product.

Latex is known to be a kind of rubber, and rubber is a natural polymer. This latex occurs in both the forms either synthetic or natural. The natural form of latex is mainly collected from the rubber trees and it is also found in variety of plants which includes the milkweed. It can also be prepared artificially by the process of building up long chains of molecules of styrene.

Natural rubber, also called by other names of India rubber, latex, Amazonian rubber, caucho, as initially produced, consists of polymers of the organic isoprene, with minor impurities of other organic compounds, plus water. Thailand and Indonesia are two of the leading rubber producers. Types of polyisoprene that are used as natural rubbers are classified as elastomers.

Currently, rubber is harvested mainly in the form of the latex from the rubber tree or others. The latex is a sticky, milky colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called “tapping”. The latex then is refined into rubber that is ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup. The coagulated lumps are collected and processed into dry forms for marketing.

Some plastics, such as polythene, can be melted and reshaped over and over again. These plastics are recyclable and are called thermoplastics. Other plastics are more resistant to heat and cannot be melted and reshaped. They are known as thermoset. Plastic kitchen work-surfaces and the hard plastic casings around some electrical goods are made from thermoset.

Though thermoset plastics and thermoplastics sound similar, they have very different properties and applications. Understanding the performance differences can help you make better sourcing decisions and improve your product designs.

The primary physical difference is that thermoplastics can be remelted back into a liquid, whereas thermoset plastics always remain in a permanent solid state. Think of thermoplastics as butter – butter can be melted and cooled multiple times to form various shapes. Thermoset is similar to bread in that once the final state is achieved, any additional heat would lead to charring.

Thermoset

Thermoset plastics contain polymers that cross-link together during the curing process to form an irreversible chemical bond. The cross-linking process eliminates the risk of the product remelting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances.

Thermoset plastics significantly improve the material’s mechanical properties, providing enhances chemical resistance, heat resistance and structural integrity. Thermoset plastics are often used for sealed products due to their resistance to deformation.

Thermoplastics

Thermoplastics pellets soften when heated and become more fluid as additional heat is applied. The curing process is completely reversible as no chemical bonding takes place. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties.

There are multiple thermoplastic resins that offer various performance benefits, but most materials commonly offer high strength, shrink-resistance and easy bendability. Depending on the resin, thermoplastics can serve low-stress applications such as plastic bags or high-stress mechanical parts.

Plastic may be shaped in various ways. It can be extruded (pushed through a nozzle when liquid) to form sheets, tubes and fibers. Molten plastic can be poured into moulds. Vacuum forming is a way of making complicated plastic shapes. A sheet of warm plastic is placed over a mould, and then the air is sucked from under it so that the sheet is pulled firmly against the sides of the mould. When the plastic is cooled, it retains the mould’s shape. Disposable cups are often made in this way.

Metalworking using machines and machine tools includes cutting using a lathe, plastic forming, and welding. When grouped with other such metalworking techniques, plastic forming is also called stamping and makes the designed shapes by pressing the material into a die. This processing method utilizes the plasticity—the characteristic that a material remains in the shape it is changed to by the application of a certain force—of metals and other solids. Plastic forming is primarily used in the metalworking of steel materials such as those for automobile parts. Unlike cutting with a lathe, this method does not produce chips and also allows mass production of the same parts through mold pressing.

There are two types of plastic forming: Cold-plastic forming, which is performed at ambient temperatures, and hot-plastic forming, which uses heat. When heated, metal undergoes thermal expansion and changes shape. As such, cold-plastic forming is used whenever possible and hot-plastic forming is used only when the material of the target being produced is hard.

Some examples of other types of plastic forming include forging for manufacturing nuts and bolts; extrusion, wire drawing, and pultrusion for forming wire materials and pipes; deep drawing for creating spherical surfaces in metal sheets; bending for producing leaf springs; riveting for securing assemblies in place; and shearing for cutting metal sheets.

Almost anything can be made from plastic! Plastic packaging keeps food fresh and protects it from bacteria. A plastic coating, called Teflon, can prevent food from sticking to cooking pans. Plastic can be elastic, like the skin of a balloon, or very rigid and reinforced with other fibers, as in a protective helmet. Plastic can also be a good insulator. A plastic sleeve on electrical wiring protects the wires from corrosion and the user from electric shocks. Polystyrene packaging can help to keep take-away food warm. Plastic can be dyed in bright colours or completely transparent, to make spectacles and contact lenses. Without plastics, there would be less music in our lives, with no cassette tapes, compact discs or even old-fashioned records.

Plastic, polymeric material that has the capability of being molded or shaped, usually by the application of heat and pressure. This property of plasticity, often found in combination with other special properties such as low density, low electrical conductivity, transparency, and toughness, allows plastics to be made into a great variety of products. These include tough and lightweight beverage bottles made of polyethylene terephthalate (PET), flexible garden hoses made of polyvinyl chloride (PVC), insulating food containers made of foamed polystyrene, and shatterproof windows made of polymethyl methacrylate.

Many of the chemical names of the polymers employed as plastics have become familiar to consumers, although some are better known by their abbreviations or trade names. Thus, polyethylene terephthalate and polyvinyl chloride are commonly referred to as PET and PVC, while foamed polystyrene and polymethyl methacrylate are known by their trademarked names, Styrofoam and Plexiglas (or Perspex).

Industrial fabricators of plastic products tend to think of plastics as either “commodity” resins or “specialty” resins. (The term resin dates from the early years of the plastics industry; it originally referred to naturally occurring amorphous solids such as shellac and rosin.) Commodity resins are plastics that are produced at high volume and low cost for the most common disposable items and durable goods. They are represented chiefly by polyethylene, polypropylene, polyvinyl chloride, and polystyrene. Specialty resins are plastics whose properties are tailored to specific applications and that are produced at low volume and higher cost. Among this group are the so-called engineering plastics, or engineering resins, which are plastics that can compete with die-cast metals in plumbing, hardware, and automotive applications. Important engineering plastics, less familiar to consumers than the commodity plastics listed above, are polyacetal, polyamide (particularly those known by the trade name nylon), polytetrafiuoroethylene (trademark Teflon), polycarbonate, polyphenylene sulfide, epoxy, and polyetheretherketone. Another member of the specialty resins is thermoplastic elastomers, polymers that have the elastic properties of rubber yet can be molded repeatedly upon heating.