Waterproofing characteristics

When fatty-acid or wax emulsion type damp-proofers are used in conjunction with lignosulfonate or hydroxycarboxylic-based admixtures, heavy air entrainment results with attendant strength reduction. Both these effects decrease waterproofing characteristics. At higher workabilities, ligno sulfonates counteract the reduced bleeding effect obtained with waxes and increase bleeding rates [83]. 

Decrease in the waterproofing characteristics due to the extraction of lime when the concrete is subjected to a continuous exposure to moisture. 

We know the most about cuticular hydrocarbons, because they are abundant and because it is relatively easy to isolate and identify them. They are also the most hydrophobic lipid components, and so should provide the best barrier to water-loss. -Alkanes isolated from insect cuticles typically have chain lengths of 20-40 carbons. These can be modified by insertion of cis double bonds, or addition of one or more methyl groups. Relatively polar surface lipids include alcohols, aldehydes, ketones and wax esters (see Chapter 9). Given this diversity, is it possible to predict lipid phase behavior (and, by extension, waterproofing characteristics) from composition alone If so, a large body of literature would become instantly interpretable in the context of water balance. Unfortunately, this is not the case. 

Finally, we will briefly describe polymer-based resin formulations. Resins are suitable as the carriers for active ingredients, such as metofluthrin. Their durability, waterproof characteristic, and highly flexible properties make them highly suitable for both indoor and outdoor use. 

The Teijin Company in Japan developed a fabric named Snper-Microft with high water repellency by emulating the strncture of a lotns leaf. Water rolls like mercnry from the lotus leaf, whose surface is microscopically rough and covered with a waxlike substance with low snrface tension. It was reported that Snper-Microft exhibits good water-repellent dnrability and a high wear resistance, and at the same time it possesses moisture permeability and waterproof characteristics. 

Table 2.5 Effect of plasma coatings on the waterproof characteristics of fabrics with respect to traditional coating...

Both melamine—formaldehyde (MF) and resorcinol—formaldehyde (RF) foUowed the eadier developments of phenol—, and urea—formaldehyde. Melamine has a more complex stmcture than urea and is also more expensive. Melamine-base resins requite heat to cure, produce colorless gluelines, and are much more water-resistant than urea resins but stiU are not quite waterproof. Because of melamine s similarity to urea, it is often used in fairly small amounts with urea to produce melamine—urea—formaldehyde (MUF) resins. Thus, the improved characteristics of melamine can be combined with the economy of urea to provide an improved adhesive at a moderate increase in cost. The improvement is roughly proportional to the amount of melamine used the range of addition may be from 5 to 35%, with 5—10% most common. 

At constant PBT/PTMO composition, when the molar mass of PTMO block is >2000, partial crystallization of the polyether phase leads to copolymer stiffening. The properties of polyesterether TPEs are not dramatically different when PTMO is replaced by polyethers such as poly(oxyethylene) (PEO) or poly(oxypropylene). PEO-based TPEs present higher hydrophilicity, which may be of interest for some applications such as waterproof breathable membranes but which also results in much lower hydrolysis resistance. Changing PBT into a more rigid polymer by using 2,6-naphthalene dicarboxylic acid instead of terephthalic acid results in compounds that exhibit excellent general properties but poorer low-temperature stiffening characteristics. 

A few miscellaneous tests that fall under neither input nor output characteristics, are surveillance tests, delay times, waterproofness, workmanship, duds, tumbling and some others... 

High explosives like RDX, HMX or PETN with a polymeric binder form a flexible explosive material that can be rolled into sheet form which can be cut and applied to any contour. They have a variety of applications from metal cutting to demolition and blasting to armor protection. Some important characteristics of sheet explosives are-flexibility, moldability, waterproofness and safety in handling. Also, sheet explosives can easily be cut and initiated. 

Expl compns having high safety characteristics in the presence of firedamp and coal-dust, were provided by mixing 6—12% sensitizer (such as NG with NGc), 87—89% ion-exchange mtxt of an oxidizer (such as Na or K nitrate) with Amm chloride, up to 0,5% waterproofing agent (such.as Ca stearate) and ca 2.5% other additives. E.g 70/30-NG/NGc mixt 9.5,... 

In above proplnts DNT acts as a gelatinizing waterproofing agent and, being a weak expl, it contributes to ballistic characteristics. It has also a slight flash-reducing action... 

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