Plastic — in today’s world, it’s just about everywhere. Items we come into contact with on a daily basis, from smartphones to SmartWater bottles, make plastic ubiquitous. Sure, you may not love plastic, but the truth is, like phones and water, plastic is essential in the modern world.
Just look at the plastic parts that keep vehicles running: RL Hudson designs and manufactures a wide variety of plastic injection molded parts for medium/heavy trucks, and even provides product design and engineering for custom molded plastic engine parts. These custom plastic parts are essential not only to keep the medium/heavy trucks running but also to the companies who rely on them to keep business humming.
In reality, businesses around the globe need quick turnaround time plastic parts, and that’s where we create value as a top manufacturer of custom plastic parts. However, let’s take a step back. What is plastic? What is its history, and what’s the deal with elastomers? Continue reading and you’ll discover the answers to these questions and learn all about classifications, material profiles
What is plastic material?
Plastics are polymeric materials. That means they are composed of long chains of repeating molecules known as atoms. “Plastic” is a general term that refers to the wide range of mostly synthetic (or semi-synthetic) materials that can be formed into useful products. In fact, the term “plastic” derives from the Greek root
A history of plastics
Today, RL Hudson manufactures molded plastic parts for high-temperature applications, plastic assemblies, and even provides rapid prototyping services for product design. But how did plastics arrive here?
The modern synthetic version of plastic has been around for over 100 years. Its roots go back to the nineteenth century. In 1863, a New York billiard supply company was facing a shortage of the ivory they used to make billiard balls. They offered ten thousand dollars to anyone who could find an alternative for their products. A young printer named John Hyatt decided to give it a shot.
Experimenting with cellulose nitrate, a recently discovered material, Hyatt found he could create a more useful, moldable substance by adding camphor. It came to be known as celluloid. Although celluloid wasn’t great for billiard balls, it made excellent hair combs. Hyatt’s materials created an entire industry of hair comb manufacturing. Later, celluloid was used to make photographic film, as well as the sunglasses popularized by movie stars whose faces were immortalized on celluloid.
You can see plastics have come a long way. Today, there are a wide variety of plastic products that can be made from injection molding and other methods. We’ll discuss both plastic materials and molding later, after a discussion about elastomers and classifications.
What’s the difference between plastics and elastomers?
Many wonder about the difference between plastics and elastomers. At RL Hudson, we manufacture a wide variety of custom molded products and seals. These are molded from rubber compounds with specific resilience properties suitable for a given application. Such compounds take specific elastomers, like nitrile or silicone, as their primary ingredient. In reality, these elastomers are just polymers, long chains of repeating molecules composed of atoms like carbon and hydrogen. And for this reason, elastomers are known as polymeric materials (remember, plastics are polymeric materials, too).
The main difference between plastics and elastomers is how they respond to heat. Typically, heated elastomers undergo a chemical reaction known as vulcanization. This reaction results in the formation of permanent connections, known as cross-links, between the long molecular chains. Think of these cross-links as chemical bridges that give cured elastomers three-dimensional structures and allow them to be formed into specific shapes, such as O-rings or shaft seal lips. Since such custom parts cannot be remelted, many elastomers are great examples of thermoset plastics.
On the other hand, plastics undergo a physical change when heated, but these changes are reversible, and no permanent chemical curing occurs. Plastics often begin in pellet form, then become softer and more fluid as heat increases. This fluidity allows them to be shaped in a variety of ways, including through extrusion, calendaring, injection molding, and blow molding. As they cool, plastics harden but no chemical-crosslinking occurs. The changes are purely physical and, with the reapplication of heat, reversible. Because they retain the ability to be reshaped using heat, many plastics are referred to as thermoplastic materials.
But remember: the distinction between elastomers and plastics described here is based on responses to heat. While generally true and useful to remember, be aware there are such things as thermosetting plastics and, conversely, thermoplastic elastomers. All of that to say, “nothing is absolute”. Today, our plastic injection molded parts end up in marine engines, facilitate fluid transportation, involve plastic assemblies and more. So, when you partner with our talented team of engineers, we’ll deliver plastic molding success.
How plastics are classified
Now that we’ve delineated between plastics and elastomers, let’s talk about how plastics are classified. Plastics offer a seemingly endless array of opportunities when it comes to design. Today, there are over four dozen basic types of plastic. When compounded and otherwise manipulated, these types of plastic can result in tens of thousands of distinct and quite frankly very useful materials.
These plastic materials are sometimes classified according to the ways in which their constituent molecules are arranged. Plastics containing very well organized, dense arrangements of molecules are often referred to as crystalline. Plastics containing some organized molecule alignments as well as some random arrangements are known as semi-crystalline. And plastics in which the molecular arrangement is entirely random are called amorphous.
A given plastic’s degree of crystallization can have a big impact on its physical properties (with more crystallization typically adding rigidity). The degree of crystallization can also affect a plastics visual aspect, such as how it looks and responds to light, and plastics can be classified according to their light transmitting properties. Transparent plastic is one through which you can see. You cannot see through a translucent plastic, though light will still pass through the material. An opaque plastic allows for the passage of neither sight nor light.
From a chemical point of view, molecular-based classifications are fascinating due to their relation to material performance. After all, that’s what matters most, right? Fortunately, plastic materials can also be classified according to their mechanical, chemical, thermal and electrical properties. Three general classifications are in use today: commodity plastics, engineering plastics and high-performance plastics.
Commodity plastics are the low-end types and are typically used for high-volume disposable products where low cost is a priority. Engineering plastics are the next step up and are used for parts requiring a better range of properties, including greater durability. And, as the name implies, high-performance plastics are the high-end types. High-performance plastics are used for applications requiring excellent mechanical, chemical, thermal, and/or electrical attributes. At RL Hudson, our in-house engineers are very experienced with a wide range of plastics, especially engineering and high-performance plastics.
That’s why our products end up in applications around the globe where performance and reliability are paramount. Whether it’s plastic part design for injection molding or rapid manufacturing for plastic injected molded plastic parts, we can bring your project to the next level. With that, let’s turn our attention plastic material profiles.
Material profiles for custom molded plastic parts
When it comes to material profiles, nylon is a great example of an engineering plastic. As mentioned earlier, many polymers are composed of repeating carbon and hydrogen atoms; nylon also contains nitrogen and oxygen within its chemical structure. Often designed by the letters PA (for polyamide fiber), nylon was introduced back in the late 1930s and has since found wide acceptance due to its great strength and durability. Known by many trade names, nylon can be blended with other materials like minerals or glass to further augment strength, dimensional stability, and heat resistance. For example, our engineers recently used a glass-filled nylon compound to replace what had been a metal part for an engine application, and this resulted in significant cost savings for the customer. That’s because metal to plastic conversions for weight consideration is just one service we offer to create value as a top manufacturer of custom plastic parts.
Take polytetrafluoroethylene, for example. This material often serves as the basis for extremely useful high-performance plastics. Sometimes called PTFE but known most widely by the DuPont trade name Teflon, polytetrafluoroethylene features fluorine atoms within its chemical structure. These fluorine atoms are strongly bonded to carbon atoms, making the material extremely resistant to chemical breakdown. PFTE also functions well across a wide temperature range. As a result, PTFE parts are often used in aggressive chemical and thermal environments that would break down lesser materials.
These are just a couple of plastics we use regularly. We also have wide experience designing custom plastic parts and components made from acetal, acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), polypropylene (PP), polyetheretherketone (PEEK), high-density polyethylene (HDPE), and many other plastics.
Molding advice for custom plastic parts
Of course, good plastic materials must still be properly molded to be truly useful. Many of the plastic parts our engineers design are injection molded. Injection molding is so-named because plastic pellets are melted and injected under pressure from a heating chamber through a sprue, runner and gate system into closed molded cavities. Once filled and cooled, the mold is opened and the part removed.
Once our engineers have designed a part and selected a material, we utilize a mold flow analysis (MFA) program to spotlight any potential molding glitches. The MFA program works to predict how a material will flow into a mold cavity under variable conditions. These variables include temperature, pressure and gate and runner size and location. The ability to anticipate molding performance saves you time that would otherwise be lost awaiting factory evaluation of a design.
We are here to bring success to your next project requiring custom molded plastic components. Whether it’s multiple component assemblies for plastic parts or product design and engineering for plastic parts, our experience and capabilities mean success in your next endeavor.