I recently posted a comment on a video on youtube about the Galaxy Tab vs the iPad. Ignoring other details, I did mention the iPad has a much bigger screen, but weighs nearly twice as much as a result. I got the following reply:

@gxcad iPad is mainly heavier because its made of aluminium where as the galaxy tab is made of plastic.

While I am pretty sure the reply is mistaken, I found the topic a little interesting. I argued that while plastic is lighter than aluminum of the same volume (or should I say mass?), aluminum is stronger, allowing the use of less material to gain the same structural strength, and that I believed the drastic weight difference is instead in the difference in size of the devices, and the size of the internal batteries. For example, macbooks made of aluminum usually weigh less than macbooks of similar size made of plastics. In fact, interestingly, the unibody 13 inch plastic macbook weighs 4.7 pounds, while the non unibody 13 inch plastic macbook weighs 5.0 pounds. I wonder if the additional structural strength of a unibody architecture allowed the use of thinner plastics to maintain the desired strength? Of course, the difference is small enough that it could simply be a difference in internal components, but still fun to ponder about.

So I was wondering if anyone would care to bite and add to this discussion? The video in which I commented is found below:

http://www.youtube.com/watch?v=LYivabHHj9g

It is a pretty popular video so you'd have to hunt to find my comments (under 'gxcad') but its also a good video to see the physical size difference between the Galaxy Tab and the iPad.

I'm in the injection molding business. We are manufacturing automotive parts. Other than 'standard' materials such as ABS, PP, PE, there are also endless number of materials, which we call engineering plastics. These are resins that are being produced by mixing different off-the-shelf plastics with additives, depending on the specifications of the required application. These specifications are usually being given by the client.

For example, SABIC, one of the leading plastic resin manufacturers, has introduced an new material last May, which is supposed to be 50% lighter and 40% stronger than aluminium.

http://www.sabic-ip.com/gep/en/NewsRoom/PressReleaseDetail/may_27_2010_sabicinnovativeplasticsrevolutionary.html