Composite materials are made by combining two or more substances with differing physical properties. The best composites are made from materials that complement each other, combining the strengths of the individual ingredients to create a new material that has the best characteristics of each. Plastic composites are no different, and contain fillers, powders, particles, fibers and other reinforcing materials to improve rigidity, strength or other aspects to suit a variety of purposes.
A specialized injection molding technique called reaction injection molding (RIM) is done when two parts of a liquid thermosetting polymer are mixed together, injected into a mold, and ultimately form a molded part in several seconds. The RIM process creates attributes in the molded material that sets it apart from the standard injection molding process. A key difference is how RIM promotes plastic polymerization, which gives polymers made by this method distinctive properties.
As a multistage process, RIM involves combining two or more liquid intermediates (isocyanate and polyol). The liquids are stored in separate tanks for which feeding and temperature are controlled. These liquid thermosetting polymers are then released into supply lines, channeled into a metering chamber that regulates pressure and circulated into a mixing head.
This mixing head applies pressure up to 3,000 pounds per square inch (psi), which then uses impinging mixers to combine the plastic resins. The mixture of reactants are then injected at high speed into molds. Once the mold is filled, the mixing head stops releasing the reactants, creating a plastic polymer within the mold through an exothermic chemical reaction. Once cured, the plastic polymer comes out as a solid component.
Though RIM machines deal with liquid materials, reaction injection molding depends on a relatively cool process, producing polymers through a chemical instead of thermal reaction. Molds typically are made from aluminum, nickel or steel that are clamped into a low-weight press. Cooling times vary from less than a minute to several minutes, depending on the part size. Rapid production cycles, however, are often accomplished by RIM when compared to some other molding processes like rotational molding (rotomolding).
Advantages of Lightweight Plastic Composites
The lightweight plastic composites made from RIM techniques have a number of advantages over comparable metal parts. Here is a relatively comprehensive list:
- Corrosion-resistant material such as thermosetting plastic polydicyclopentadiene (pDCPD) or polyurethane lasts longer when exposed to toxic chemicals. Unlike metal parts, it will not deform, rust or otherwise corrode. That’s why these materials are useful for manufacturing complex equipment used in highly corrosive environments like chemical generation plants.
- Durability of plastic composites allows them to withstand increased friction and heavy loads better than other types of material, including metals.
- Easier to clean and sterilize than metal, plastic composites play a vital role in the medical industry by helping prevent the spread of dangerous microorganisms.
- Fuel efficiency improves with vehicular components made from these lighter plastic composites, allowing the manufacture of less weighty vehicles that are both environmentally and economically beneficial. Studies have proved that there’s a 5-7% decrease in fuel usage when there’s a 10% reduction in weight.
- High strength to weight ratios give polyurethane, dicyclopentadienes (DCPDs), and other plastic composites an edge over other materials, offering increased durability and strength comparable with steel or concrete, while also offering lighter weights.
- Lightweight polymers are a tenth as light as most metals used for components, reducing weight and greatly improving fuel efficiency, particularly in the aerospace industry. In the medical industry, it allows for lighter and more ergonomically designed instruments and machines.
- High tensile strength of lightweight thermosetting plastics is comparable to that of metals, making them perfect to replace metal parts.
- Impact-resistant polymers allow for less cracking or denting than metal parts, perfect for vehicle or truck body panels, hoods, fenders, and so much more.
- Insulation properties of several polymers allow them to withstand electrical and thermal extremes better.
- Lower pollution results from using these lightweight polymers as a result of greater fuel efficiency. Components are also more durable, weather-resistant, tougher and more tolerant to impact, which results in vehicles that can last for several decades while releasing less waste into the environment.
- Power costs are lower during the manufacturing process, as lighter weight components made from plastic composites require less energy to produce than metal ones.
- Saving space results from allowances for thinner wall designs, allowing machinery to fit in tight places, which can easily be custom fabricated.
- Versatility of plastic composites allows for a myriad of uses, as they can be made to be flexible, dyed nearly any color, resistant to bacteria and other microbes, fire-resistant or with bubbles to provide additional insulation. Components made via the RIM process retain their shape indefinitely, and can be formed into a wide array of parts with a plethora of uses. For example, the construction industry sometimes utilizes plastics to strengthen walls, columns, chimneys, slabs and other structural elements that are subject to added service loads, deterioration or excessive refraction.
- Easy to install and long-lasting piping or filtering systems made from plastic composites are used in environments with acidic soil or chemicals, reducing maintenance costs. Also, roofing shingles made from several materials, including pDCPD, can be made to resemble standard shingles and are virtually maintenance free for a lifetime.
- Resistant to mildew and staining, some polymers are used in a wide range of commercial and residential applications, including countertops, shower receptors, hot tubs, and floor tiles.
Plastic Composites by Osborne
There are tens of thousands of uses for plastic composites, many more than can be listed in one article. Osborne Industries is at the forefront of the industry, providing custom production molding by RIM with a variety of plastic composites, including polyurethanes, polyimides, DCPDs, and hybrids or custom materials developed for individual project specifications. Osborne’s capabilities include complete design, testing, prototyping, finishing and developing services for materials used to build all manner of structurally engineered parts with close tolerances.
To learn more or inquire about a project, please contact us today!