Polypropylene is a material that is frequently compared to PVC (polyvinyl chloride). While not as frequently used as PVC, polypropylene is still a useful material for coating custom wire baskets.
Some of the polypropylene material properties that you should know when choosing a coating for your custom wire basket include:
- Chemical Resistance. Polypropylene is generally noted as having a high resistance to chemicals compared to polyethylene (“regular” plastic). Polypropylene will resist many organic solvents, acids, and alkalines. However, the material is susceptible to attack from oxidizing acids, chlorinated hydrocarbons, and aromatics.
- Tensile Strength. Compared to many materials, polypropylene has a good tensile strength—somewhere around 4,800 psi. This allows the material to withstand fairly heavy loads, despite being lightweight.
- Impact Tolerance. While polypropylene has a good tensile strength, its impact resistance leaves something to be desired when compared to polyethylene.
- Water Absorption. Polypropylene is highly impermeable to water. In a 24-hour soak test, the material absorbs less than 0.01% of its weight in water. This makes polypropylene ideal for total immersion applications where the basket material underneath has to be protected from exposure to various chemicals.
- Surface Hardness. The hardness of polypropylene is measured on the Rockwell R scale as 92—placing it on the high end of the softer materials measured on that scale. This means the material is semi-rigid. This makes it more likely to bend and flex with an impact.
- Operating Temperature. The maximum recommended operating temperature for polypropylene is 180°F (82.2°C). Beyond this temperature, the performance values of the material may be compromised.
- Melting Temperature. At 327°F (163.8°C), polypropylene will melt. This makes polypropylene unsuited to high-temperature applications of any kind.
Why You Should Use Polypropylene
An ideal use case for polypropylene would be an aqueous parts washing process where the basket being coated would be submerged in non-oxidizing agents for prolonged periods of time.
In such an environment, the impermeability of polypropylene would allow it to completely protect the coated basket from the liquid cleaning solution. Additionally, so long as the internal temperatures in the wash do not exceed 180°F, the coating would most likely last for many uses.
Another reason to use polypropylene would be to protect delicate parts from getting scratched. While not quite as soft as some formulations of PVC, polypropylene is still a semi-soft material that will absorb impacts—helping minimize the risk of parts getting scratched during the agitation cycle of many aqueous-based cleaning processes.
When You Shouldn’t Use Polypropylene
Polypropylene is not recommended for any high-temperature processes because of its low melting point. Additionally, any processes that use oxidizing acids, chlorinated hydrocarbons (such as trichloroethylene), and aromatic solvents should be avoided.
Sharp, sudden impacts from other objects can cause damage to a polypropylene coating. So, if you’re considering a polypropylene coating, it’s important to examine your production process to see if there are any points where such impacts are likely to repeatedly occur.
Is a polypropylene coating right for your custom wire basket or tray? To answer that question, it’s important to know about your process! Contact Marlin Steel to learn more about custom wire basket coatings or to get a custom basket quote with our recommendations!