# Tag Info

107

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 condition. In particular it is a lot more resistant to scratches than comparable plastics and isn't really subject to much in the way of environmental degradation. ...

44

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 UV light, and (towards the LH end) you can see a cubelike pattern of stress cracks, rather like a toughened glass windscreen after a pebble hit it. You really ...

30

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 an engineering point of view) Most transparent plastics are not resistant enough. Plexiglas is one example which fulfills the requirements enough to be used ...

14

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 to get the protective paper off I both scraped and melted the plastic. We want hard windows for houses and primary buildings. So what you describe would be ...

12

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 pairs of electrons on neighboring atoms in a generally tetrahedral arrangement, giving carbon a large versatility in molecular configuration and conformation. The ...

9

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 glass windows are: Up to 80% of all recycled glass can be reclaimed. Recycled glass uses 40% less energy than manufacturing new glass. Recycling doesn’t ...

8

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 widely: It is versatile. It is used as a grease (like other greases, e.g. petroleum based ones) because it provides good lubrication. It is used as a caulk (like ...

7

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 when inserted into the well, while being filled with water, or when it is being removed from the well. You mention your wells are cased with concrete pipes. They ...

7

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 plastic. This causes the polar molecules in the plastic to align so that one side of the film has a positive charge and the other side has a negative one. ...

6

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 volume $\mu$ is the ratio of ball mass to bar mass $v$ is velocity of impacting ball Per Roark's Formula's for stresses and strains 7th edition, this can ...

6

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 gravity if possible. ABS sinks in water (SG = 1.06), Polypropylene would float (SG = 0.946).

6

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 / contraction than those for glass windows. http://www.eplastics.com/Plastic/plastics_library/Coefficients-of-Thermal-Expansions-of-Plexiglass http://www.sdplastics....

6

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 get an increase in deformation. During the process of elastic deformation, if you decrease the load to zero you will not have any residual non-zero deformation. ...

6

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 the case of a complex design, vinyl cutters perform the task quite well. The stencil is applied using transfer tape, after which etching chemicals are applied. ...

6

6

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" means the material has absorbed moisture from an environment with 50% relative humidity until it has reached an equilibrium state.

5

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 byproduct of machining. Using a method like EDM will alter the properties of a polymer nearby, as it will heat the polymer. If you are interested in ...

5

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 inaccuracies and inconsistencies. Rapid prototyping is very reliable and not subject to the same issues as machining like tool wear and fixturing issues, but no part ...

5

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 removed. Acetone will detect ABS really well if your specific solvent is more slow acting. The blemish is usually just a dull area in the surface. Remember that ...

5

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 stuff works as well, but the 2.3 mm allows you to place a weld bead on the edge using standard weld rod and plastic welding tools. If not, for a pretty ...

5

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 why something is never the solution 100% of the time. Here are some instances where I think fire retardant fillers would not be preferred: Filler Capacity - A ...

5

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 steel construction predominates in cars, too. For small boats, the cost equation leans more toward the ease of manufacture of that size of structure out of ...

4

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 will experience. However, cannot see how this could this could be kept in place without some additional reinforcement; I am pretty sure there is a sheet piece of ...

4

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 fit. Equally rather that trying to reinvent the wheel you would be better using off the shelf connectors which are known to work. It would be fairly trivial ...

4

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 test would only be valid for that supplier of polypropylene, and only for that thickness. This uncertainty in testing results from several interesting factors: ...

4

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. Regulations have been established for commercial steel ships (DNV GL, Lloyds, ABS, individual countries). These regulations take into account the harsh marine ...

3

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 is much more resistant to such effects compared to plastics. There is also something called creep, which is essentially time-dependent deformation during long ...

3

You seem to want an a slight interference fit so the top will snugly seat into the housing. Depending on your wall thickness and size you could probably oversize the "male" portion of the cap like .002-.003" compared to the "female" dimension. That being said, and understanding that 3D printing generally cannot hold those tolerances I would try an ...

3

The type of hinge used in products to hold displays in place at various angles and for similar tasks are called generically torque hinges. There are many different constructions. Design would be a typical mechanical engineering problem- coefficients of friction, tolerances and so on. If they have discrete positions where they prefer to stay they may be ...

3

that part was injection molded in an unscrewing mold which allows fully-formed threads to be molded into a part. Ordinarily, the resulting undercuts would prevent the part from being extracted from the mold but in an unscrewing mold, a motorized shaft inside the mold unscrews the finished part from the mold after the plastic has solidified and the two halves ...

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