Improving Surface Roughness of Polypropylene and Measuring Surface Roughness

[kat.rawlings]

Hi everyone,

I was just wondering if anybody can offer me any tips or advice for a project I am working on at the moment. We have been carrying out shot blasting using various abrasives to improve the surface roughness of some polypropylene parts that we are making for the medical industry (1m to 2.5m diameters). Various abrasives have been tested such as garnet, glass bead AB 177-297 and 801 AC, brown aluminium oxide 80/100 and 180/220, white aluminium oxide 70, 120 and 180/220, kiln dried sand, blasting grit (came free with the Sealey shot blasting gun), Honite 13 glass bead, Type 2 plastic media (Urea Formaldehyde) and Type 5 plastic media (20/30 and 30/40 acrylic).

White aluminium oxide 180/220 and acrylic blast media gave us the best results. However, when an electron microscope was used to find the surface roughness of some polypropylene samples that had been blasted with aluminium oxide 180/220, we found that the surface roughness was around 2.5 microns Ra, when it needs to be 0.8 microns Ra.

We therefore still need to improve the surface finish considerably. Does anybody have any suggestions of how we can do this? We are currently carrying out more shot blasting testing with aluminium oxide and plastic media. We are also looking into dry ice blasting.

Also, we would like to be able to measure the surface roughness of our samples on-site while we are carrying out trials. I am therefore looking into hiring/buying a surface roughness testing machine. Can anyone recommend UK companies who might be able to help with this?

Thanks

Kat

 

[Achy47]

rina


Hi Katrina,

It sounds like you have already done a lot of testing and have some good results with the white aluminium oxide 180/220 and acrylic blast media. However, it seems that the surface roughness is still not meeting your desired specifications. Here are a few suggestions that may help you improve the surface finish of your polypropylene parts:

1. Consider the size and shape of your abrasive particles: In shot blasting, the size and shape of the abrasive particles can greatly affect the surface roughness. It may be worth experimenting with different sizes and shapes of abrasive particles to see if you can achieve a smoother finish.

2. Adjust the blasting pressure and distance: The blasting pressure and distance from the surface can also impact the surface roughness. You may want to try adjusting these variables to see if it improves the finish.

3. Try a different blasting technique: Dry ice blasting is a newer and more environmentally friendly blasting technique that uses dry ice pellets as the blasting media. This may be worth exploring as an alternative to traditional shot blasting.

4. Use a different type of media: There are many types of blasting media available, each with its own unique properties. It may be worth trying different types of media, such as ceramic or steel shot, to see if they can provide a smoother finish.

As for on-site surface roughness testing, there are many companies in the UK that offer surface roughness testing services and equipment rental or purchase. Some companies that you may want to look into are Mitutoyo, Taylor Hobson, and Bowers Group. It's also worth reaching out to your local universities or research institutions, as they may have the equipment available for use or may be able to provide recommendations.

I hope this helps and good luck with your project!