Plastic resin is a major player in the raw-materials world. According to the American Chemistry Council, U.S. production of resin reached 7.7 billion pounds in October 2020, a year-over-year increase of 5.6 percent. Allied Market Research also noted that the sector makes a major global impact, reaching a value of $403.1 billion in 2019 that’s expected to grow to $522.5 billion in 2027. Resin is a major component in many types of products — including centrifugal sealless magnetic drive pumps.
In this post, we’ll explain what plastic resin is, how many types of plastic resins have industrial applications, the plastic resin types we use here at March Pump, and the various ways in which different resins can benefit end users.
What is Plastic Resin?
When you hear the words “plastic resin,” you may conclude that resin is plastic. In truth, though, resin is only a part of plastic’s family tree and not a plastic proper. In most cases, it’s a plastic precursor, but since “plastic” serves as something of an umbrella term, you may find people refer to resins as “plastic resins.” Yes, it sounds confusing, but the whole thing makes much more sense when considered chemically.
Many resins are naturally occurring, plant-based compounds that share certain unique characteristics. DifferenceBetween.com explains that resins are categorized as a group of solid or semi-solid amorphous compounds. The compounds are obtained directly from plants as “exudations and usually have a clear yellowish-brown color and are highly viscous substances that harden into transparent solids with treatment.” When wondering is resin biodegradable, you can confidently answer yes to this sort of resin.
However, these natural resins contain certain downsides, such as a lack of stability, which has led to the development of synthetic resins. When these resins undergo specific kinds of chemical treatments and refinements (typically called polymerization), they become plastic. These materials typically get stored as plastic resin pellets that can be melted and molded into an end-use product, but it’s not unheard of for certain kinds of material to get marketed as a plastic resin liquid that hardens when combined with some sort of curing agent.
But this is only the start to what plastics are. All of the various plastic resin grades have different physical characteristics, different recyclability requirements, and different industrial or end-product uses. We will discuss some of these in the following section.
Types of Plastic Resins & Advantages
Plastic resin breaks down into seven types (although note that one of them is a catch-all category). These categories are listed according to their numerical plastic-resin recycling codes and were originally established in 1988. According to Miller Recycling Corporation, those are:
- 1 – PET or PETE (Polyethylene Terephthalate)
- 2 – HDPE (High-Density Polyethylene)
- 3 – PVC (Polyvinyl Chloride)
- 4 – LDPE (Low-Density Polyethylene)
- 5 – PP (Polypropylene)
- 6 – PS (Polystyrene)
- 7 – Ryton & Kynar and/or Other
Each of these plastic resins have different physical characteristics, different end uses, and differing degrees of recyclability. However, one of the more common characteristics is that recycled plastic resin often isn’t damaged when heated, which means that it sometimes can be reclaimed and injection molded into a new form.
Once processed, PETE creates a rigid or semi-rigid plastic that doesn’t weigh much and is naturally transparent. It stands up well to temperatures reached by most microwaves and ovens. You can recycle all forms of PETE, and you’ll find it in many consumer products such as food packaging (e.g., peanut-butter bottles, liquor bottles, cooking-oil bottles).
High Density Polyethylene (HDPE) appears in more places than most people imagine. Ironically, this easy-to-mold material has a high melting point. It also boasts a stout strength-to-density ratio, with 60 grams of HDPE easily able to support about eight pounds of weight. Naturally opaque, HDPE resists fungal growth, which is why you’ll find it in water piping, milk jugs, detergent containers, lotion bottles, and vinegar bottles. It also is recyclable.
Not only is PVC incredibly widely used, it can be produced in two forms: flexible and inflexible. The former finds use in electrical insulation and flooring, while the latter gets employed most often as piping. Extremely hard, strong, and cheap, PVC can emit toxic fumes if it gets burned. You cannot recycle it.
Low-Density Polyethelene (LDPE) shares many characteristics with its cousin HDPE. However, it’s softer, naturally translucent, and has a shinier finish. It shows up in end-use products that require flexibility, such as plastic carbonated-beverage rings, shampoo bottles, food-storage containers, and dry-cleaning bags. You can recycle some items made with LDPE, but not all.
Given its high melting point, fatigue resistance, ability to take any color or transparency, and ability to withstand the heat and pressure produced for sterilization purposes by an autoclave, polypropylene resin finds uses in food storage and various industrial processes. While it functions poorly in cold temperatures due to a susceptibility to impact damage, it is strongly resistant to many types of chemicals. Not all kinds of polypropylene can be recycled.
From packing material and insulation to sporting goods and aircraft parts, polystyrene appears in all sorts of goods. In addition to the puffy particulate foam with which most consumers are familiar, polystyrene can also be shaped into straws, bottle caps, disposable eating utensils, and fast-food containers. You can never recycle this kind of material.
The final category of plastic resin is simply titled Other, and it includes any resin created after 1988. As you can imagine, this category is wildly diverse and includes examples such as compostable PLA, mixed resins, polycarbonate, LEXAN, and epoxy. For those wondering is epoxy resin recyclable, the answer is almost always no — and the same is true for most of this grade of resin.
Common Applications for Plastic Resins in Pumps
March Pump employs three different kinds of plastic resins in our centrifugal sealless magnetic drive pump: Polypropylene (schedule 5), Ryton (schedule 7), and Kynar (schedule 7). Each of these resins has its own general uses and specific applications for our pumps.
Polypropylene plays several specific roles in pumps. Because of its relative cost effectiveness, it’s the most common material to encounter in all kinds of pumps. It tolerates pressure and temperature up to 50 psi 190 degrees Fahrenheit, and it competes admirably against metal pumps when it comes to stress-induced damage or cracking. Its relative lightness makes for easier installation, and it’s possible to create polypropylene pumps that meet FDA guidelines, opening them up for a wider variety of uses. Finally, polypropylene pumps resist etching and erosion from caustic substances such as:
- Sulfuric Acid
- Fluosilicic Acid
- Hydrogen peroxide
- Hydrochloric Acid
- Potassium Hydroxide
- Nitric Acid
- Phosphoric Acid
- Sodium Hydroxide
Ryton pumps operate within the same heat and pressure parameters as polypropylene. Where they really shine is in chemical resistance. No other thermoplastic can tolerate chemical exposure as well. Some of the substances that these pumps can manage include:
- Freon 11
- Benzene Sulfonic Acid
- Copper Chloride
- Ethyl Chloride
- Petroleum Ether
Finally, Kynar pumps typically operate at higher temperatures (up to 200-degree Fahrenheit) and pressures (up to 75 psi) than the previous two materials mentioned. While it’s more costly, it also thrives in applications where polypropylene or Ryton would struggle or fail. Some of the substances that Kynar pumps move include:
- Sodium Hypochlorite
- Chrome Alum
- Ethylene Dichloride
- Hydrofluoric Acid
- Phosphorus Trichloride
Financial Benefits to the Customer
In the world of pumping, the gold standard has traditionally been stainless steel pumps and pumps lined with ETFE or PFA. It’s hard to argue that these pumps don’t excel when it comes to pumping under extremely high pressures or particularly harsh substances. Another thing is also true, though: These types of pumps are almost always cost prohibitive for smaller applications (i.e., end uses that don’t require the movement of more than 200 gallons per minute), and very few kinds of chemicals require this kind of rigor to properly handle.
If you have a smaller flow chemical pumping application, call us at (847) 725-0580 or contact us to learn more about our polypropylene, Ryton, and Kynar centrifugal sealless magnetic drive pumps. Stable, reliable, and customizable, our pumps have aided clients since 1962 with applications as diverse as refrigeration, heat transfer, vending, ventricle assist devices, electrostatic painting, etching, water treatment, desalination, and more!