Resins and Plastics Used in Rotomolding
Introduction
Are you looking to learn more about the raw materials needed for the rotomolding process? Explore with Rotoplast the essential information about the resins and plastics crucial for designing rotomolded products. Rotomolding is a technique that involves heating plastic material in powder form within a rotating mold. This process ensures the production of hollow, solid parts with high precision.
Common Resins and Plastics in Rotomolding
Plastic resins are the primary raw materials essential for the rotomolding process. Before any manufacturing process, these materials are typically available in powder form or sometimes as a viscous liquid. The plastics used for rotomolding must meet certain qualities and characteristics, such as viscosity, also known as "rotomoldability." The raw material must have a sufficiently low viscosity when melted to flow easily and evenly coat the mold's surface during rotation. Too high a viscosity would prevent a uniform distribution of the material, creating thicker and thinner zones.
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The plastics regularly used to manufacture a product by rotational molding are :
High-Density Polyethylene (HDPE):
HDPE is one of the most widely used plastics for manufacturing rotomolded products. This raw material also has good impact resistance, even in cold conditions, and abrasion resistance.
HDPE has numerous qualities. Its strength is ideal for manufacturing products intended for intensive use. High-density polyethylene resists a wide range of chemicals, such as acids, bases, and solvents, making it suitable for applications in harsh environments. If you plan to design a rotomolded product for outdoor use, HDPE is a pertinent choice due to its good resistance to sunlight and weather. It can be used to manufacture a variety of products, including containers, storage tanks, urban furniture, designer furniture, and buoys. HDPE packaging is used in many sectors, including cosmetics, healthcare, food, and chemicals, making it an ideal solution for oily, liquid, and food products.
Medium-Density Polyethylene (MDPE or LLDPE):
MDPE polyethylene is another widely used plastic in rotomoulding due to its various properties, which are suited to this manufacturing technique. It accounts for 80 to 90% of all polymers producing rotomolded plastic parts. Medium-density polyethylene is also called LLDPE since it is a copolymer. Due to its flexibility and malleability, this material is more easily shaped and processed than HDPE. MDPE polyethylene can also be a less expensive raw material than HDPE.
Polyethylene has many desirable properties, including lightweight, easy to process, chemical and impact resistance, low friction coefficient, and excellent electrical insulation qualities.
Polyvinyl Chloride (PVC):
PVC, from the English term polyvinyl chloride, is a flexible or rigid plastic material. It is one of the most used materials in rotomolding after polyethylene, representing about 10 to 15% of polymers. Its relatively low cost and the simplicity of the rotomolding process make it possible to produce economical parts. Rotomolded PVC products also have a long lifespan due to the material's resistance to weather, corrosion, and wear, as well as its easy maintenance.
Polycarbonate PC:
Polycarbonate PC is a thermoplastic known for its exceptional optical and mechanical properties. Its characteristics make it a suitable raw material for various applications that require both strength and lightness. Polycarbonate PC is highly valued for its toughness. It is so resilient that it is used in the manufacture of riot shields and anti-vandalism displays. Its transparency is comparable to that of glass, making it ideal for applications requiring high light transmission.
Polyurethane (PU):
Polyurethane (PU) used in rotomoulding offers many advantages. This material is used as a foaming agent to insulate or reinforce rotomolded parts. It is widely used to manufacture coolers and other containers that require thermal insulation.
Polypropylene PP:
Polypropylene or PP is a thermoplastic material offering several interesting characteristics for rotomoulding. One of its main qualities is its high rigidity. This attribute makes it an ideal raw material for creating robust and durable products capable of withstanding significant forces without deforming. In addition to its rigidity, PP also has notable resistance to high temperatures. This characteristic is particularly important for applications where the product is likely to be exposed to heat, as this raw material ensures that the product retains its shape and mechanical properties even at high temperatures. However, in rotomoulding, the use of Polypropylene is less common compared to polyethylene due to its tendency to be more brittle at lower temperatures.
Polyamide PA:
Polyamide PA is more commonly known by the commercial name Nylon. This thermoplastic is widely used in various industries, including rotomoulding. Polyamide PA has a low coefficient of friction and high abrasion resistance, making it suitable for the manufacture of products with good impact resistance. PA also has an exceptional capacity to withstand dynamic loads, dampen noise and vibrations, and resist impact forces. It is available in powder form for rotomoulding, to create robust, durable, and resilient products.
Linear Low-Density Polyethylene (LLDPE) and Cross-Linked High-Density Polyethylene (XLHDPE):
XLHDPE and LLDPE are two types of plastic in the polyethylene family. These two materials each have their qualities:
XLHDPE is a material that retains its rigidity and strength even at very low temperatures. If you plan to manufacture products suitable for use in cold environments, this plastic is ideal. It can also withstand prolonged contact with chemicals without degrading. For designing a container intended to store a product like diesel, XLHDPE is perfectly suited.
LLDPE offers moderate flexibility and high resistance to impact and puncture. This material is chosen for applications requiring a certain degree of flexibility while ensuring good robustness, resistant to puncture by sharp or pointed objects.
Depending on the manufacturer and the product requirements to be rotomolded, other types of plastics can also be used. Low-Density Polyethylene (LDPE), Medium-Density Polyethylene (MDPE), High-Density Polyethylene (HDPE), Polypropylene (PP), Polyamide (PA), or Polyurethane (PU) are all raw materials for rotomolding.
How the Rotomolding Process Transforms Plastic Resins
Rotomolding, also known as rotational molding, is an interesting technique for creating hollow plastic objects. Complex parts of various shapes can be manufactured using this process. The plastic material is introduced into an open mold, carefully prepared. The amount of plastic material loaded depends on the size and thickness desired for the final product.
In rotomolding, the slow rotation of the mold on two axes ensures the uniform distribution of the plastic powder. The mold is rotated and heated to melt the plastic material and distribute it. A cooling step then solidifies the melted plastic, giving it the mold's shape. The part is then demolded, cleaned, and possibly deburred to remove surface imperfections.
Conclusion
The numerous qualities of resins and plastics in rotomolding offer a wide range of possibilities. Do you want to produce a piece resistant to extreme temperatures or suitable for outdoor use? Opt for a product made from resins and plastics through the rotomolding process. Whatever the desired qualities for your final project, we provide tailored advice on plastic selection before manufacturing your rotomolded object.