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PCBs , or polychlorinated biphenyls , are a class of man-made chemicals. The commercial production of PCBs started in but their use has been banned or severely restricted in many countries since the s and 80s because of the possible risks to human health and the environment. As PCBs are resistant to acids and bases as well as to heat, they have been used as an insulating material in electric equipment, such as transformers and capacitors , and also in heat transfer fluids and in lubricants.
PCBs have also been used in wide range of products such as plasticizers , surface coatings, inks, adhesives, flame-retardants , paints, and carbonless duplicating paper. Sources of PCB pollution:. Concise international chemical assessment document 55 Section 1 Executive summary and Section 4, Sources of human and environmental exposure.
PCBs , or polychlorinated biphenyls , are a class of man-made organic chemicals. Each PCB molecule contains two phenyl rings. A phenyl ring is a ring of 6 carbon atoms to which hydrogen atoms are attached. In PCBs, chlorine atoms replace some of these hydrogen atoms. Chlorine atoms may be present at some or all of the 10 possible positions which are numbered 2—6 on one ring, and 2'—6' on the other ring see figures below.
In total, different PCBs can be formed. These different combinations are called congeners , each having a specific number of chlorine atoms located at specific positions. Two different systems are used for naming PCBs. In the IUPAC system used in the examples above, the numbers at the beginning of the name specify the sites where chlorines are attached to the phenyl rings.
Another system assigns a separate number, from 1 to , to each of the specific PCB congeners. PCBs which have the same number of chlorine atoms attached but at different positions, are referred to as isomers. The two rings in a PCB molecule can rotate around the bond connecting them.
The shape of the molecule is further influenced by the repulsion between nearby chlorine atoms so that the rings of a specific PCB will either lie approximately in the same plane called coplanar or in different, more perpendicular planes termed non-planar.
Those PCBs which have both rings lying in the same plane are considered to be most toxic , based on combined health effects considerations. They are also referred to as " dioxin-like ". Physical properties of PCBs :. Although in general PCBs do not easily evaporate, especially those with more chlorine atoms, PCB evaporation does occur, and can account for significant amounts of PCB transport see question 2.
PCBs can be measured in:. This summary is free and ad-free, as is all of our content. You can help us remain free and independant as well as to develop new ways to communicate science by becoming a Patron! Languages: English [en]. Next Question. Level 1: Summary Level 2: Details. What are PCBs? See also GreenFacts' Dioxins Study. Glossary Links About. Get involved! Published under the authority of the GreenFacts Scientific Board.
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Output jobs are configured as an OutJob file, giving you full control over print-based output. A new printout can be added to the current configuration by choosing the Insert Printout command from the PCB Printout Properties dialog's right-click menu.
By default, all options in the Include Components column will be enabled. This dialog appears directly when adding a new layer. If you are adding a new layer to a printout, first select the layer you would like to add from the Print Layer Type drop-down list.
The list contains all currently defined layers for the source PCB document, allowing you to include any PCB layer on a printout. This gives you complete control over what appears on the printed page. All options defined in this dialog apply to each print-based output that can be generated. This region allows you to control the coloring that is used for each possible layer than can be printed. For each layer, you can define the color used when printing in gray scale or color.
Click on the left-hand color swatch to access the range of gray scale shades. Click on the right-hand color swatch to access the Choose Color dialog, from where you can choose from a range of predefined colors or create your own, custom color. In addition to adding mechanical layers individually to a printout, you can also automatically include them in all printouts when the print job s for the parent document type is sent to the nominated printing device.
Use the options in this region of the dialog to specify and enable substitution fonts. The Print Keepout Objects option gives you full control over whether keepout designated design objects are included on the printed document or not.
Enable the Use Net override color checkbox if you want to use the net override color in your printout. The following list of commands are available from the right-click menu, accessed from anywhere within the PCB Printout Properties dialog:. Remember, you can have multiple instances of any printout use the Add New Documentation Output control from the OutJob in the Output Containers region to do this , which is particularly useful for 3D since you can print out views of the board from differing perspectives if you wish.
The dialog is divided into four regions:. A custom view of your board can include it being rotated to an angle, zoomed, have various settings for surface colors, visibility, opacity, and board thickness.
You can use these options to generate views that provide high levels of detail to highlight areas of your design or even create effects.
Configuration options defined here are distinct and separate from those defined for the same output type in an Output Job file. Again, the former will be stored with the project file, the latter with the Output Job file. If would like to speak with a representative, please contact your local Altium office. Download Altium Designer Installer. You may receive communications from Altium and can change your notification preferences at any time.
If you are not an active Altium Subscription member, please fill out the form below to get your free trial. Just fill out the form below to request your Student License today. Upverter is a free community-driven platform designed specifically to meet the needs of makers like you. Click here to give it a try! Configuring PCB Printouts. Using Altium Documentation. Any additional new layer is added at the bottom of the layer list. This means that this layer will be drawn first in the printer's memory when the image is rendered.
Each layer above is then rendered on top in turn. Use the Move Up and Move Down buttons to change its position in the render order. Using this feature will overwrite the right-hand color swatch for each layer. The gray scale color definitions will remain unchanged unless you manually change them. To print in color or gray scale, the corresponding option Color or Gray must be enabled in the associated page setup dialog for the print output.
The color printing mode for the nominated printing device must also be set accordingly in the associated properties dialog. Printer-friendly version. Found an issue with this document?
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