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| Leader hopeful on coordinated Euro crisis response Sun, 12 Oct 2008 14:19:34 GMT |
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| PARIS (AP) -- The president of the European Commission said he was very hopeful that a meeting of European leaders Sunday would take an important step toward a coordinated response to the global financial crisis.... |
| Palin has mixed record as fiscal conservative Sun, 12 Oct 2008 14:21:21 GMT |
| ANCHORAGE, Alaska (AP) -- Alaska Gov. Sarah Palin, the Republican nominee for vice president, bills herself as a fiscal conservative. But that can be a relative term when you're governor of a state gushing with oil money.... |
| Developing countries feeling fallout from meltdown Sun, 12 Oct 2008 12:43:07 GMT |
| WASHINGTON (AP) -- Searching for ways to tackle the unfolding economic crisis, global finance ministers are turning attention to the fallout in developing countries and poor nations.... |
| Efforts on global warming chilled by economic woes Sun, 12 Oct 2008 14:22:41 GMT |
| WASHINGTON (AP) -- The economic free fall gripping the nation may bring down one of the main environmental objectives: capping the greenhouse gases that are blamed for global warming.... |
| Bailout managers may be buying own securities Sun, 12 Oct 2008 14:28:01 GMT |
| WASHINGTON (AP) -- The government's plan to make sure private managers of a $700 billion bailout plan are free of conflicts of interest is weak, according to some critics, and allows too much room for abuse.... |
| Analysts: GM would need cash to acquire Chrysler Sun, 12 Oct 2008 09:14:01 GMT |
| DETROIT (AP) -- For General Motors Corp. to acquire Chrysler LLC and all of its warts, GM would have to get desperately needed cash as part of the deal. Lots of it, according to industry analysts.... |
| Tax rebate, food stamp money possible in aid plan Sun, 12 Oct 2008 09:12:45 GMT |
| WASHINGTON (AP) -- After consulting with Barack Obama, Democratic leaders are likely to call Congress back to work after the election in hopes of passing legislation that would include extended jobless benefits, money for food stamps and possibly a tax rebate, officials said Saturday.... |
| Emirates officials say nation's banks are strong Sun, 12 Oct 2008 11:01:43 GMT |
| DUBAI, United Arab Emirates (AP) -- Officials in the United Arab Emirates say the country's financial institutions remain healthy despite growing fears the global credit crisis will hurt the booming Gulf economy.... |
| Bush visits finance officials, urges cooperation Sun, 12 Oct 2008 00:23:05 GMT |
| WASHINGTON (AP) -- Global finance leaders are pledging cooperation between rich and poor nations to deal with a severe credit crisis after President Bush discussed the seriousness of the current situation.... |
| All that money you've lost _ where did it go? Sat, 11 Oct 2008 16:41:59 GMT |
| NEW YORK (AP) -- Trillions in stock market value - gone. Trillions in retirement savings - gone. A huge chunk of the money you paid for your house, the money you're saving for college, the money your boss needs to make payroll - gone, gone, gone.... |
Factors For Selecting Acrylic
Author: Savey Bakarne
Total views: 49
Word Count: 463
When selecting material on basis of environmental conditions features that figure into the selection are chemicals likely to be encountered, sterilization methods, humidity, temperature, and thermal cycling. Additional important factors are mold and part design, processing requirements, and assembly methods. When selecting the best grade of acrylic to use, these same factors must be considered. The higher molecular weight grades are more resistant to crazing from chemical exposure and mechanical stress, but have lower melt-flow rates. But as the level of impact modifier is increased in impact-grade acrylic, other properties such as clarity, light transmission, and tensile strength often diminish. It is difficult to predict processing requirements as flow patterns and mold-filling problems can result from large part surfaces, deep ribs or flanges, asymmetrical geometries, and unbalanced thick and thin sections. While experimenting with several different grades in the prototype tool is recommended. Molds are designed for acrylic, ABS, and polycarbonate parts typically accommodate a shrinkage level of 0.006 in allowing for convenient trial runs of acrylic in molds used for ABS or polycarbonate parts. But direct comparison of the parts molded from different materials can help determine the best one for the application.
When compared with other polymers, acrylic is relatively easy to process. It can be molded with little or no residual stress and is available in formulations specifically designed for injection molding or extrusion in a wide range of melt-flow rates. When processing is done under normal conditions, acrylic produces melts that are typically higher in viscosity than those of many other thermoplastic polymers. Also the higher molecular weight grades are generally recommended for extrusion. As acrylic has higher viscosity flow properties, injection molding runners and sprees used to process it need to have larger diameters than those handling polystyrene or polyethylene. Parts with large injection molded or parts with thin-wall geometries require a high melt-flow rate. On processing acrylic in molds built for polycarbonate or polyester, lower injection pressures should be used, as it is less likely to warp than polyesters and is more forgiving in molds not designed with well-balanced gates.
As acrylic has a higher melt viscosity than polystyrene or styrene alloys thus it requires higher injection pressures when selected in place of those materials. Also higher clamping forces may also be required. Acrylic is a hygroscopic material thus it absorbs water and must be dried prior to molding. But if it is molded while wet, it exhibits moisture splay, leaving streaks, bubbles, and a rough surface on the part. Thicknesses for acrylic parts range from 0.040 to 0.500 inches. The thick or thin part can be achieved with special designs or processing methods such as injection/ compression molding. Main consideration is consistency and any changes in thickness should be gradual, and feature radiuses edges.
Article Source: FreeBusinessContent.net
About the Author
Savey Bakarne is a professional retail display specialist and teaches store owners how to gain profits from utilizing the proper Custom Retail Store Displays.
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