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111 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

There are two main reasons why glass is still preferred over say PMMA. The first is durability. As long as it isn't broken, the glass in a window can easily last for hundreds of years in good ...
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46 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Here is a plastic (most likely PMMA) window, in a boat, after only 37 years. In addition to the obvious scratches, the outer surface has developed a cloudiness : possibly from degradation due to ...
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31 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

What are the requirements for window glass? Resistance to moisture Resistance to UV radiation Resistance to cleaning agents Very high transmission in the visible spectrum (There are many more, from ...
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15 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

I actually did make windows out of plexiglas for an outbuilding. I could work them to the shape I wanted and they were lightweight. However, I discovered that they indeed scratch easily: just trying ...
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  • 257
12 votes

Silicon and silicones

Silicon forms bonds in a similar way to carbon, and has a similar outer-shell electron orbital configuration. Carbon, as you may well know, has the ability to covalently bond with up to four lone ...
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10 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

After some research, we are using glass windows as it was used traditionally. Actually plastic windows exists. Though it may take time for most of us to adapt to it. While the reasons to consider ...
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8 votes

Silicon and silicones

Starrise gave an answer describing silicone from an engineering/chemical perspective, but I disagree that this is the reason for silicone to be so widely used. The real reasons why it is used so ...
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8 votes
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How are protective sheets attached to plastics?

The material is called "Electrostatic Protective Film". It is manufactured by letting the plastic film cool in a strong electrostatic field: there are high-voltage electrodes on top and bottom of the ...
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8 votes

Why not build container ships from plastic?

In short, because steel is less expensive on a strength per dollar basis of anything else, and for large structures, it's less expensive to work, again on a strength per dollar basis. That's why ...
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  • 2,228
8 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

As your construction is 3D printed, increasing the strength at the point of current breaking will more likely transfer the damage to a new location. The obvious and possibly impractical solution is to ...
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7 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Another issue is that the coefficient of thermal expansion of many plastics is higher than that of window glass. Frames for plastic windows would have to be able to accommodate more expansion / ...
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7 votes

Can I seal the inside of a water well to use it as water reservoir when the well is dry?

Well liners are generally made to order. One of your issues will be to find a company that can make what you want. You will need to ensure the liner is the correct size and that it does not tear ...
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7 votes

Why not build container ships from plastic?

Anything is possible and lowering the lightship weight (LS) of ships will save fuel, but the key issue would be any change must not reduce the seaworthiness of ships. This question is very broad. ...
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6 votes

Best plastic composite alternative to wood

For impact: $$ \sigma_{max} = \frac{v}{V}E(1+\sqrt{\mu + \frac{2}{3}}) $$ Where: $V = \sqrt\frac{gE}{\delta}$ $g$ is Gravitational constant $E$ is Young's modulus $\delta$ is the weight per unit ...
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  • 5,303
6 votes
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What should the size difference be between a lid and a container?

To make the lid fit on reliably with as tight as possible, the only difference you need in the box and lid dimensions is the resolution of the 3-D printer. You need to account for manufacturing ...
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6 votes
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How to determine whether plastic is ABS or Polypropylene?

This is a great question. Typically the engineering method to identify plastics is with a Burn Test. As fun as it sounds, it is destructive. So the next place to go is to try to test specific ...
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6 votes

Difference between 'plastic yielding' , 'plastic yield strength', plastic strength' and 'plastic stress'?

All these terms refer to the effect of loading on the deformation of materials. Let us assume that we start with zero load and zero deformation. Elastic deformation If you increase the load you ...
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6 votes

How would I put a barcode of other scannable code on a coffee cup?

A few different marking processes are available to accomplish your objective. Glass is a good choice, for reasons of durability. Etching One creates a mask or stencil with the desired graphic. In ...
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6 votes

PTFE sheet vacuum forming

Don't make them, just google "ptfe stoppers", and buy them. (You've asked an XY problem.)
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6 votes
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What does 50% RH mean?

DAM means "dry as manufactured" or "dry as moulded", i.e. the material is in its moisture-free state immediately after manufacture. The DAM moisture content is typically less than 0.2%. "50% RH" ...
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5 votes

How to determine whether plastic is ABS or Polypropylene?

There is often a non-critical location on the plastic extrusion that you can test some of the solvent on. Rubbing a little with a paper towel you can see discoloring and if any of the plastic is ...
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5 votes
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Can I seal the inside of a water well to use it as water reservoir when the well is dry?

I see two ways: I've had great experience in my pressure vessel design with a 2.3 mm thick liner of polypropylene or polyethylene. In a pinch, you can weld PVC, but I don't recommend it. Thinner ...
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  • 5,303
5 votes

How do I cut a crack into a polymer/plastic?

Since you used some specific words in your question, I will respond a certain way. Cracks are generated by mechanical action, and cannot be machined in. They may, in certain brittle materials, be a ...
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  • 241
5 votes

Why not use fire-retardant plastics everywhere?

Fire retardant fillers are pretty cheap; often cheaper than the base plastic (Alumina Trihydrate for example). Like anything in engineering though, there are always exceptions and functional reasons ...
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  • 7,489
5 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

Build the auger around a stronger shaft which has a better connection to the motor shaft. Perhaps a carbon fibre or even a steel centre. But then consider what will be the next breaking point. Or make ...
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5 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

You might consider dealing with it in software. Sense the stepper motor current, and when it exceeds a certain threshold that indicates jamming, perform a high speed reverse rotation for one or more ...
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4 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Hardness aside, weathering effects (from e.g. rainfall, snow, hail, temperature and moisture variations etcetera) and UV degradation are of course important to consider for windows. In general, glass ...
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  • 41
4 votes
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Information regarding plastic hinges that can hold the position

A hinge bending with the material rather than mechanically is known as a living hinge. Consideration are placed upon the number times it will be bent during the lifetime and what sort of forces it ...
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4 votes

How to create an airtight connection between Stainless Steel and PTFE?

You're going to struggle to get a reliable gas tight fit with that design. For a start it would be better if the two connections were separate so they aren't fighting against each other in terms of ...
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4 votes

Shear strength polymers

The reason it is impossible to give you figures is that nobody has run the tests to verify the shear strength. Why? Wouldn't it be easy to get a block of polypropylene and run a test? Well, that ...
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