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According to "Thermal properties of polymers" n. Therefore the random arrangement characteristic of the liquid persists down to temperatures at which the viscosity is so high that the material is considered to be solid". These amorphous solids undergo a process known as glass transition at a certain temperature instead of melting "Glass transition", At the specified temperature, the substances will become softer and more pliable, eventually becoming a liquid "Glass transition", Solvent welding happens in three steps Dukane Corporation, The first step is pressing, and it is required to ensure contact between the two pieces being welded, maintain proper orientation of the pieces and to force intermolecular diffusion between the two pieces.
The second step is getting the temperature of the material over its Tg by use of a cement. This is achieved by lowering the Tg of the material until it goes below the temperature of the material. Doing so allows for the polymer chains to diffuse between the two pieces "What is solvent welding? The last step is restoring the temperature of the material back under its Tg. This solidifies the pieces together and ensures that they will not continue to move around, creating a rigid joint between the two pieces Dukane Corporation, The second step of the solvent welding process requires the use of a cement, which is composed partly of PVC Oatey, This helps the two pieces of material in that it provides a surface on which the two materials can fuse.
It also contains acetone, which softens the materials to ensure maximum joint strength. In addition to the cement, a primer may also be used during the solvent welding process to presoften the material to fuse and create maximum joint strength Oatey, According to Hong and Wu , the acetone used in their tests lowered the Tg of epoxy resins during their curing by decreasing the degree of cross-linking.
The lowered Tg that the acetone in primer allows for the diffusion of the polymer chains at a lower temperature than would normally be required. Therefore, in solvent welding, the heat normally required by other types of welding is not required "Thermal properties of polymers", n.
There are two "classes" of cement. The reason for performing this investigation is that there are disagreements between professional plumbers on the necessity of primers in the process of solvent welding of plastic pipes and fittings. This study will help determine if the application of primer significantly increases the strength of cemented joints.
If primer penetrates and softens the plastic surfaces prior to the application of cement, then the inclusion of primer in the solvent welding process should achieve maximum fusion and strength. The data recorded represents the maximum readings on the digital scale with small tolerances, but are obviously less than the true compression force at the moment of failure.
However, a significant number of primed joints failed before the unprimed joints, as shown in table 1. Was primer necessary to have better joint strength? The hypothesis was that if primer penetrates and softens the plastic surfaces prior to the application of cement, then the inclusion of primer in the solvent welding process should achieve maximum fusion and strength.
This was not the case. In both tests, the primer had a negative effect on the strength of the pipes. In the compression test, more primed joints failed first than unprimed joints.
In this audio podcast, Handyguys Paul and Brian respond to a question sent in by one of their listeners via e-mail about the importance of priming, what and how much you prime and when to prime the entire house.
I have a question about painting and when to prime. One will scrape and spot prime, then paint the house. The other says they will scrape and prime the whole house, then paint. Handyguy Brian explains that the old color can bleed through to the new paint if not first primed. Handyguy Paul suggests against changing from a latex-based paint to a oil paint as this can ruin the quality of the finished paint job.
To help the new paint adhere to the surface well, Handyguy Brian advises to prime when painting over a glossy paint. Although the traditional way is to de-gloss by sanding priming is an easy way to put down a low gloss base before you paint.
If you have additional questions about when to prime or anything else for The Handyguys, simply go to the Contact Us tab of www. Additionally, you can view some of our videos in our YouTube channel and subscribe to the show in iTunes. Definitely good to know! Some examples would be factory coated metal sidings, ceramic tile, glazed block, plastic and vinyl shutters , and surfaces with a high gloss finish.
If you choose the correct bonding primer for your application you will be far more likely to get great adhesion of your finish coat to the surface. We would advise people to not think of these products as something that will save you a coat of primer, but instead think of them as an opportunity to use an additional coat of the same material instead of switching products between the base coat and the finish coats.
On new drywall, you will use 3 coats of the finish material instead of a primer coat plus 2 coats of finish. If you're in the Greater Pittsburgh or Tampa Bay Areas and you need help with your priming and painting project, please contact us for a free consultation and quote!
Ready to get started with your next painting project but unsure if it is in your budget? Reach out to the expert painting team at ImageWorks Painting to schedule a free consultation today. Give us a call at Tampa or Pittsburgh , or request a visit online. Masonry Primer There are several reasons why it is a good idea to apply a masonry primer before paint.
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