Polystyrene and styrene copolymers that are expanded into a range of useful goods are referred to as expanded polystyrene (EPS). EPS is available in polystyrene beads loaded with a blowing agent; usually, pentane and other chemical additives induce expansion properties in beads and allow them to be processed into low-density foam boxes; EPS is 90% air. EPS foam is a common packing material because of its shock-absorbing characteristics and other attributes and its low cost, strong insulating properties, custom moldability, and ease of processing. EPS packaging boxes have so many advantages
Packaging density must be considered when determining the appropriate level of cushioning. Cushion curves derived from dynamic drop testing are used in the preliminary design stages to identify the proper package configuration—foam thickness and density—to sufficiently protect the goods. The designer can suit the protection needs of a wide range of fragile objects by adjusting the density, consistency, and shape of the EPS foam.
In general, density increases strength properties; nevertheless, the geometry of the molded object, and to a lesser extent, bead size and manufacturing conditions, as well as density, affect the cushioning characteristics of polystyrene boxes. This one-of-a-kind feature allows a packaging engineer to fine-tune cushioning function without rebuilding or retooling the package.
The EPS packaging industry has established common shock cushioning curves for EPS transport packaging designers. Temperature changes do not affect the shock-absorbing characteristics of EPS. Changes in temperature between –17°C and 43°C do not affect the optimum performance characteristics of EPS, according to recent research conducted at San Jose University’s Packaging Program. The following statistics should be regarded as an accurate depiction of EPS foam performance by packaging engineers.
Another key feature of EPS foam boxes is their dimensional stability. It refers to a material’s capacity to maintain its original shape or size under altering environmental circumstances.
Different plastic polymers react differently to different use conditions and temperature and relative humidity variations. Some shrink, others expand, and still, others remain untouched. EPS has great dimensional stability and can withstand a wide range of environmental conditions. EPS foam is anticipated to have a maximum dimensional change of less than 2%, putting it in compliance with ASTM Test Method D2126.
As published in ASTM C578 Standard Specification for Rigid Cellular Polystyrene Thermal Insulation, the polystyrene foam industry has established test data for construction insulation applications. This standard covers EPS foam’s physical properties and performance characteristics related to thermal insulation in construction applications. There was no need to create such a formal document for the packaging sector. When produce, medications, and other perishables must be conveyed and stored in temperature-controlled conditions, EPS is practical and cost-effective packing material. The homogeneous, closed cellular structure of EPS provides excellent heat flow resistance.
Moisture resistance refers to a packing material’s capacity to keep water out of its structure without destroying its mechanical characteristics. EPS’ cellular structure is essentially water-resistant and has no capillarity. Due to the small interstitial spaces between the molded beads, EPS may absorb moisture when entirely immersed. Under pressure differentials, molded EPS is moderately permeable to water vapor but highly impermeable to liquid water. The density and thickness of a material determine its vapor permeability. Water and water vapors do not affect the mechanical characteristics of EPS.
Water and aqueous salt, and alkali solutions do not affect expanded polystyrene. The vast majority of organic solvents are incompatible with EPS. This should be considered when choosing adhesives, labels, and coatings for direct application to the product. All unknown-composition chemicals should be checked for compatibility. Exposing molded polystyrene to the material at 120°–140° F can be used for accelerated testing. Molded polystyrene is slightly affected by UV rays. It induces surface yellowing and friability but does not influence the physical qualities of the material.
At 73 degrees Fahrenheit and 50% relative humidity, the volume resistivity of molded polystyrene in the 1.25–2.5 PCF density range is 4 x 1013 ohm-cm. The dielectric strength is estimated to be around 2KV/mm. The permittivity is 1.02–1.04 for frequencies up to 400 MHz, with a loss factor of less than 5 x 10⁻⁴ and less than 3 x 10⁻⁵ at 400 MHz. To meet electronic industry and military packaging rules, molded EPS can be treated with antistatic chemicals.
The primary goals of transport packing materials are to preserve and safeguard a product from damage from start to finish, from manufacturing to delivery to the consumer. When selecting the ideal packaging material, many variables must be considered, including ease of handling and storage, weight, cushioning properties, manufacturing efficiency, simplicity of identification, customer needs, cost, and more.
The physical characteristics of EPS protective packaging enable package designers to address various protection and distribution challenges. When combined with excellent engineering design considerations, these properties allow the design freedom to create cost-effective protective packaging. Contact Styrene Insulation Industry (SII), the pioneer in EPS manufacture, if you want to learn more about EPS Packaging options.