Choosing the right plastic for your application can be confusing, particularly if you are new to the industry. In our recent blog post, “When it Comes to material selection, not all plastics are created equal,” we gave a quick overview of the polymers that Impact extrudes, touching on their general characteristics and typical uses.
In this next blog post, we narrow our focus to discuss one of the materials we extrude in greater detail – High Impact Polystyrene (HIPS). HIPS is a very versatile, economical and tough material that exhibits good impact strength, easy processing and works very well with thermoforming processes. Below are 7 important facts about HIPS plastic:
- HIPS is a modified form of polystyrene:
Polystyrene (PS) plastic is a naturally transparent thermoplastic material that is available in several forms. The most basic form of PS is general purpose PS (GPPS), also known as crystal PS. GPPS is a result of styrene monomer polymerization and it is a transparent product. Another common grade of PS is expandable PS (EPS). EPS is a foamed version of this material, often referred to as “styrofoam” which is a name for EPS trademarked by Dow Chemical Company in 1941. This material is commonly used in packaging applications such as foam meat trays or foam egg cartons.
- HIPS is a high impact strength material:
As the name would suggest, HIPS is a form of PS that carries with it a higher impact strength. Homopolymer PS can often be brittle, and can be made more impact resistant if combined with other materials. This form of PS typically is produced by adding around 5-10% rubber or butadiene copolymer. This increases the toughness and impact strength of the polymer and results in a very stiff product ideal for packaging applications. Due to the durable nature of this material, high impact polystyrene sheet frim Impact Plastics is used in packaging applications for a wide range of applications in the food, medical, consumer goods, cosmetics, industrial and horticultural markets among others.
- HIPS is an amorphous polymer:
Polymers exhibit two types of morphology in a solid state – amorphous and semi-crystalline. Whereas a semi-crystalline polymer refers to a plastic with organized and tightly packed molecular chains, the polymer chains for amorphous plastic materials are more disorganized. In an amorphous polymer the molecules are oriented randomly and are intertwined. To give you visual, the organization, or lack thereof, of the polymer chains for amorphous materials are often compared to a plate of cooked spaghetti. Amorphous polymers like HIPS are isotropic in flow, meaning that shrink uniformly in the direction of the flow and transverse to flow. This typically results in less shrinkage and less warping than semi-crystalline polymers. Amorphous polymers are typically transparent, however HIPS is a translucent white in its natural state.
- HIPS is compatible with food packaging applications:
HIPS is available in FDA approved grades and is compatible with food packaging applications. The rigid nature of this material makes it ideal for food packaging applications such as cookie and bakery trays or deli sandwich clamshells. While the moisture vapor transmission numbers aren’t as good as with other polymers, HIPS has inherent moisture barrier properties that make this material suitable for short shelf life products. In addition, improvements to particular grades of HIPS have resulted in good environmental stress crack resistance (ESCR), making this material suitable for the packaging of fatty foods such as butter. This material can be used in low-heat food packaging applications but it is not recommended for applications where the packaging will undergo heat higher than approximately 185°F.
- HIPS is a good printable substrate:
High impact polystyrene can be decorated using a variety of printing methods including screen printing, offset lithography, and flexography. This material is compatible with corona treatment processes which helps mitigate problems with adhesion to the plastic.
- HIPS is a recyclable material:
HIPS is a 100% recyclable material and is identified by the resin ID code ‘6.’ However, while HIPS and other forms of PS can be recycled, not all recycling centers and municipalities in the US accept this material. According to the 2015-16 Centralized Study on Availability of Recycling, it is estimated that between 20 – 60% of the US population has access to recycling programs that accept PS products such as cups, containers clamshells and lids, while less than 20% have access to programs that accept PS cutlery, Foam PS trays/containers, foam clamshells, and other EPS packaging. Impact plastics offers a recycled grade Utility HIPS for non-FDA applications.
- HIPS can be easily customized:
HIPS from Impact plastics is an easily customized material and is available in virtually any color under the sun. This material is compatible with a variety of processes and is therefore available in a vast range of colors, finishes and additive package formulations. Additional customization of HIPS sheet from Impact include:
- Custom color match HIPS including pearl, iridescent, and metallic colors
- Custom Embossing including small square, diamond plate & brushed metal
- Custom laminates including mylar, mirror, brushed metal & wood grain
- High gloss COEX and Matte surface finishes
- Electro Static Dissipative
- Double-sided corona treatment
- Clear HIPS
- Multi-layer Coextrusion
Interested in learning more about our HIPS products? Download our HIPS data sheets!