What do the Differences Between ABS and PBT mean for Keycaps

What do the differences between ABS and PBT mean for keycaps?

 

“PBT is superior to ABS”.  This has been the narrative from the time I first fell victim to the swallowing demise of the rabbit hole that is the mechanical keyboard world.  The first time you heard it yourself, it probably went a little like this.  “ABS is not as durable as PBT” or “PBT has a better feel than ABS”.  Broadly speaking these statements are true, but if you break it down a little further, you will see that there are a number of trade offs between the two apart from price.

 

What is ABS and PBT?

ABS (Acrylonitrile butadiene styrene), and PBT (polybutylene terephthalate) are both thermo plastic polymers.  Polymers are essentially chains molecules that have very strong binding characteristics making them ideal for molds and are used in many facets of our daily life.  Fun fact, Lego bricks are made from ABS plastic. 

The same Shiny smooth plastic you know from Lego is the same ABS used in keycaps

 

Differences in Durability

Being made of different compounds, these materials have there own set of characteristics and with that their own set of pro’s  and cons.  Outside of the keycap realm, PBT is used as an insulator in electrical industries as it is resistant to solvents & UV light and is mechanically strong.  The most important properties of PBT that apply more directly to its application in keycaps is its resistance to wear and discolouration.  ABS on the other hand, while still very durable has less resistance to wear and discolouration. 

 

Structural integrity

ABS is a much easier plastic to work with as it is a softer and more flexible material to work with compared to PBT.  The chemical compounds of both of these materials result in a big difference in moulding temperatures.  ABS is moulded at a temperature of 105 degrees Celsius in its glass transition state, while PBT requires much higher temperatures of at least 230 degrees Celsius.  These temperatures have an affect on the materials during the cooling process. 

The lower moulding temperature for ABS make it a much easier plastic to work with.  PBT can be stubborn because of the harder and more rigid characteristics and can experience warping in the cooling process.  This is why you often hear about some spacebars from certain manufacturers or batches being warped.  This warping severely limits what you can do with PBT and restricts its use to smaller, simpler and more rigid moulds which is why ABS is used as the plastics in keyboard cases. 

Here’s a tip!  You can mend some minor warping of your spacebar by placing the spacebar in hot water and placing something heavy on it and allowing the water to gradually cool before removing the weight. 

 

Differences in Look and Touch

These materials and their methods for moulding also contribute to the look and feel on the surface.  Over time ABS will wear quicker becoming more smooth and can even develop a shiny like glisten on the surface of keys that are used more than others.   In order to reduce this obvious trait of wear, the moulds between ABS and PBT are actually made differently with PBT incorporating the texture into the mould itself while ABS using moulds that result in a smoother surface to reduce this wear that would present itself somewhat rapidly.

Apart from looking unpleasant this wear can also contribute to performance issues with less grip and even slippery keys if your hands are sweaty or oily.  Typically speaking, consumers who are invested in this hobby will likely purchase a new set of keycaps for an aesthetic change before these performance issues become obvious.

 

Shine left on ABS from wear from normal usage appears shiny and can become slippery with oil and sweat

 

Difference in sound

The sound of keycaps has become an increasingly more important criteria in the purchasing decision.  For keycaps, the sound can vary with the material, the thickness and the shape of the keycap.  As we already know PBT is stronger and more rigid than ABS which is softer and more flexible in the ways you can use it, but PBT has its own downfall as it can be brittle when moulded to thin.  To combat this, PBT keycaps are made much thicker than ABS and as a result the keycaps are stronger, more rigid and structurally stable.  This results in PBT sounding more crisp and dense.  Granted this does not apply for all ABS keycaps as some higher end ABS sets are made extra thick to combat this. 

 

Limitations

In this blog post, we have gone over the limitations with moulding PBT and the warping issues it has but there are a few more limitations for both ABS and PBT to point out.  One being Dye Sublimation which is not possible on ABS as the surface is to smooth for the plastic to be printed on and the will result in dye to bleed.  On the flip side, PBT is unable to be laser etched so ABS has greater flexibility for shine through options without having to create a new moulds, such as front facing engravings and more detailed designs such as the shine through found on Ducky’s add on spacebars. 

Other limitations for PBT where ABS has an edge and one of those is colour.  ABS is typically able to achieve brighter more vibrant colours while PBT takes on a duller more pastel like colouring.   In addition, because of the rigidness of PBT and the difficulties cooling during the moulding process, the legends in PBT can sometimes be inconsistent. 

 

Pastel like colouring found in PBT Keycaps is less vibrant and more soft; Tai-Hao Sunset PBT Keycap set.

 

Summary

In conclusion there are plenty of trade offs between ABS and PBT.

• PBT is more resistant to wear, discolouration and UV damage
• PBT is more difficult to work with and can warp in larger moulds
• PBT is stronger and more rigid while ABS is softer and more flexible in ways it can be used.
• PBT keycaps resistance to wear allows for the surface to be textured while ABS are moulded differently with a smooth surface to reduce the affects of wear.
• ABS can lose its finish easier and take on a shiny slippery surface.
• PBT has a more crisp and pronounced sound signature while ABS is lower pitched and slightly more hollow sounding
• ABS has the ability to achieve brighter more vibrant colours and can use lighter colours in the legends which is difficult to achieve with PBT due to restrictions with the inner legends requiring darker colours.
• Dye Sublimation is only possible on PBT as ABS will result in the dye bleeding.
• PBT is harder to work with and has limitations with legends running into inconsistencies

But how does all of this factor into price? 

It is no secret that PBT is more expensive than ABS but let us explain that it is not due to marketing efforts but rather production costs.  The main reason is that PBT has the requirement to be thicker and thus more plastic is used in PBT keycap sets.  The manufacturing process is also more complicated which drives up costs and in addition, sourcing the raw materials itself is more expensive.  It is worth noting that ABS keycaps can be just as expensive and are often seen in small batch group by offering with high quality thick ABS keycaps. 

Overall, it is hard to say that PBT is better than ABS or vise versa.  It is really up to personal preference and what it is that you are looking for in your keycap set.  If you are happy with the colourway options of PBT and value typing experience than PBT is generally a better option if it fits within your budget.  If you are looking more vibrance, or a smoother feel or a more budget friendly option or you are looking to pick up 2 or 3 keycap sets, then maybe ABS is better for you!  Either way.. by the time you get your new set of keycaps equipped on your board, it won’t be long till you start fantasizing about your NEXT keycap set.