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Plastic products and Impact Resistance

When my wife dropped her old cell phone from the balcony to the concrete-paved yard, the phone took a few bounces and distributed itself then in several pieces around it. That was it, I thought. But as we collected the pieces, snapped them together and turned the power on, the phone worked perfectly again despite the few scratches it had gained. Excellent job on mechanical design, I had to conclude (the phone was, by the way, an ancient Nokia).

Impact resistance (or impact strength) describes a material’s or a product’s ability to absorb shock or impact energy without breaking.

Something that feels strong and stiff might be surprisingly easy to break with a bump to the right spot. Resistance against impacts is one of the key requirements in plastic product design. It is clear that a helmet or a ski boot should have high impact resistance, but almost every plastic product is subjected to impacts at some point of its service life and the consequences are often irreversible. All products should preferably be impact resistant to a degree for more reasons than one. They may fall down from store shelf before they ever meet the customer, to begin with.

Impact resistance is in fact one of the key strengths of plastics. It is why they are used in e.g. helmets, riot shields and sports gear. They replace glass in many applications, and in some cases they can be more durable than metals; if you kick a metal bucket, for example, you easily make a dent in it. A well designed plastic bucket would take the impact with no problem. Impact resistance is not, however, an inherent material property to all plastics grades. Some grades are rather poor in withstanding impact, as we all may have noticed with cheap plastic toys or other similar products.

Selecting the right material is in main role when designing impact resistant products but the mechanical design/geometry makes a big difference as well. Tips on material selection and mechanics can read by pressing the links below.

Related articles:

Impact Resistance - tips for plastic material selection

Plastic product Impact resistance - what can you do with the geometry

 

This blog focuses on the hands-on design of injection molded plastic products. If it is something close
to your heart, please share your own experiences with all of us. You can also follow plasticprop.com on
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Thank you for reading,

Markus Paloheimo, Managing Editor, plasticprop.com

  • Markus Paloheimo (Ms.Sc) is a Product Designer with two decades of experience in the field of functional consumer and industrial products. His specific area of expertise and source of enthusiasm is injection molded plastic products. Markus Paloheimo is in LinkedIn.

Comments

William Gomez
thank you for posting valuable information.
Chris lloyd
Hi William, Can you tell me if PA6 Grade plastic can be formed exactly the same as PA66 Grade?
Markus
Chris, To my experience they are very similar to form (PA66 might require slightly higher temperature). I recommend you compare the manufacturer datasheets on both materials. Markus
Francis
Hi Markhus I am currently looking a good polymer for domestic gas tank manufacture. I am wondering about good polymers to be used for the rotational moulding. I am thinking about MDPE. I am not sure about grade to use. Any info is welcome. Tks Francis
Markus
Hello Francis, You mean Medium Density PE? I am not the greatest expert on rotational molding, but that sounds like a feasible material to me. I would rely on the suppliers help when selecting the grade. Markus

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