Moisture in plastics

Splay marks Circular pattern around gate High moisture in plastic, trapping of gas in rib... 

This method has been used to determine the level of moisture in plastic materials for quite some time. The test is carried out by heating the material at a preset temperature and determining the resulting loss of weight by evaporation. The test can be conducted using either a simple laboratory oven and an accurate gram scale or a newly developed sophisticated instruments. 

You see that vacuum adapter stuck to the top of the condenser in fig. 7a Well, a closer look at it in fig. 7b will show that it has some drying agent sandwiched between two cotton balls and the nipple (tee heel) sealed with plastic wrap or foil. The drying agent can be either a commercial product called Drierite or calcium chloride. This attachment is placed on top of a condenser when refluxing solutions that have no water in them and must remain that way during the time they are refluxed. All this is to prevent moisture in the outside air from coming into contact with the cold surface of the of the inside walls of the condenser. This will surely happen and the condensed outside-air water will drip down into the reaction flask and ruin the experiment. This is not so much a... 

Aryl Phosphates. Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate. CeUulosics are a significant area of use but are exceeded now by plastici2ed vinyls (93—95). Principal appHcations are in wire and cable insulation, coimectors, automotive interiors, vinyl moisture barriers, plastic greenhouses (Japan), furniture upholstery, conveyer belts (especially in mining), and vinyl foams. 

Metal Pan Assemblies. These units consist of tiles and panels formed from perforated aluminum or steel with pads of fiber glass or mineral wool inserted into the pans to provide the sound absorption. They are used primarily for ceilings in a similar manner to acoustical tiles and panels. The pads are sometimes sealed in plastic film to prevent absorption of moisture, dirt, and odors. The perforated metal is relatively sound transparent and functions as the finished ceiling and the support for the sound-absorbing material. The perforated metal by itself has no acoustical value. 

The usual containers for shipping are glass for small quantities, and steel cans, dmms, or tank cars for bulk items. Over a period of time, moisture passes through the walls of some plastic containers. If this occurs, the more hydrolytically unstable borate esters may hydroly2e. Thus caution should be used when storing borate esters in plastic. In addition, shipping in metal cans or dmms is not acceptable where hydrolysis can lead to a corrosive product, such as a halogenated alcohol. 

The effect of exposure of plastics to the environment for a length of time. The specific effect and degree depend on the moisture in, and temperature and composition of, the environment, in addition to the length of exposure. 

The mechanical properties of composites are mainly influenced by the adhesion between matrix and fibers of the composite. As it is known from glass fibers, the adhesion properties could be changed by pretreatments of fibers. So special process, chemical and physical modification methods were developed. Moisture repel-lency, resistance to environmental effects, and, not at least, the mechanical properties are improved by these treatments. Various applications for natural fibers as reinforcement in plastics are encouraged. 

The moisture content of a plastic affects such conditions as electrical insulation resistance, dielectric losses, mechanical properties, dimensions, and appearances. The effect on the properties due to moisture content depends largely on the type of exposure (by immersion in water or by exposure to high humidity), the shape of the product, and the inherent behavior properties of the plastic material. The ultimate proof for tolerance of moisture in a product has to be a product test under extreme conditions of usage in which critical dimensions and needed properties are verified. Plastics with very low water-moisture absorption rates tend to have better dimensional stability. 

In addition to the additives used in a formulation to help stabilize the protein to freezing, the residual moisture content of the lyophilized powder needs to be considered. Not only is moisture capable of affecting the physicochemical stability of the protein itself, equally important is the ability of moisture to affect the Tg of the formulation. Water acts as a plasticizer and depresses the Tg of amorphous solids [124,137,138]. During primary drying, as water is gradually removed from the product, the Tg increases accordingly. The duration and temperature of the secondary drying step of the lyophilization process determines how much moisture remains bound to the powder. Usually lower residual moisture in the finished biopharmaceutical product leads to enhanced stability. Typically, moisture content in lyophilized formulations should not exceed 2% [139]. The optimal moisture level for maximum stability of a particular product must be demonstrated on a case-by-case basis. 

Splay is a common term for surface imperfections that occur on injection-molded parts. Like the term gels for films, splay can occur from several root causes. Many of the root causes originate from the plasticating system and are related to moisture in... 

Vegetable waste has a very high moisture content Liquid will tend to accumulate in plastic worm bins, and the worms may drown unless adequate drainage is provided. If there is a reservoir at the bottom of the bin, the liquid can be drained off through a spigot This liquid contains some plant foods, which can be recycled by watering it onto the compost pile. 

Bac-Terra requires soil moisture greater than 20%. Covering the treated area with plastic to prevent evaporation may be sufficient to maintain soil moisture in some areas. All information is from the vendor and has not been independently verified. 

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