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Electrostatic effect isCharged bodyWhen moving close to the insulated conductor,conductorThe phenomenon of being charged by induction.polymerWithchargeIt can change the local concentration of small molecular reactants in the polymer wire group, thus affecting their reaction activity.
On conductors andCharged bodyInduced by similar partschargeChargedElectrical dissimilarity；The farther part is charged with the same charge.This phenomenon is due to the fact that the object is exposed toelectrostatic fieldAnd the polarization effect.
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Electrostatic effect
The influence of electrostatic coulomb interaction in solution on the reaction rate between ions in liquid phase.The basic assumptions of the model with more general significance are:
① A and B ions (ordipole）Generated activationcomplex compound(indicated by subscript ≠) is spherical;
③solventThe dipole moment of molecule is relatively small;
④ The deviation of non electrostatic action to the ideal condition is ignored;
⑤ The system isdilute solution, and the ionic strength is zero;
⑥ The medium is continuous;
⑦ The formation of the activated complex can be regarded as the charging process of the sphere.
Advantages and disadvantages of static electricity
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Utilization and prevention
Electrostatic effect
There are many advantages and disadvantages of static electricity and its prevention. The first kind of harm comes from the interaction of charged bodies.When the aircraft body rubs with air, moisture, dust and other particles, it will make the aircraft electrified. If no measures are taken, it will seriously interfere with the normal work of aircraft radio equipment, making the aircraft deaf and blind;In the printing factory, the static electricity between the paper pages will cause the paper pages to stick together, which is difficult to separate, bringing trouble to printing;In the pharmaceutical factory.Because static electricity attracts dust, the purity of drugs will not reach the standard;When playing TV, the static electricity on the screen surface is easy to absorb dust and oil, forming a layer of dust film, which reduces the clarity and brightness of the image;The dust that is common on the blended clothes but not easy to shoot off is also the ghost of static electricity.
The second major hazard of static electricity is the possibility of explosion due to the ignition of certain flammable objects by static sparks.In the dark night, when we take off nylon and woolen clothes, sparks and "beeps" will be emitted, which is basically harmless to human body.However, on the operating table, electrostatic sparks can cause the explosion of anesthetic, hurting doctors and patients;In coal mines, it will cause gas explosion, which will lead to death and injury of workers, and the mine will be scrapped.
Polymer materials
Electrostatic effect
In the mid twentieth century, with the rapid development of industrial productionPolymer materialsOn the one hand, the extensive application of some high resistivity polymer materials such as plastic, rubber and other products and the high-speed modern production process have made the electrostatic energy accumulate to a high degree; on the other hand, the production and use of electrostatic sensitive materials such as light oil products, gunpowder, solid state electronic devices, etc,The harm of static electricity to industrial and mining enterprises is becoming more and more prominent, which has caused quite serious consequences and losses.It has caused an annual loss of tens of billions of dollars in the electronic industry, which does not include potential losses.
In the aerospace industry, electrostatic discharge causes launch failure of rockets and satellites, and interferes with the operation of spacecraft.In the petrochemical industry, there were 116 fire and explosion accidents caused by static electricity in the United States from 1960 to 1975.At the end of 1969, in less than a month, the static electricity generated by the three 200000 ton super tankers from the Netherlands, Norway and the United Kingdom during tank cleaning caused explosions in succession, which attracted the attention of scientists around the world to electrostatic protection.
More than 30 major electrostatic accidents have occurred in petrochemical enterprises in China, of which several have lost more than one million yuan.For example, the 2000m3 toluene tank of a petrochemical company in Shanghai, the rubber slag tank of a petrochemical company in Shandong, and the aviation kerosene tank of a petrochemical company in Fushun all caused serious fire and explosion accidents due to static electricity.After World War II, many industrial developed countries have established electrostatic research institutions.
Electrostatic hazard
Electrostatic effect
be caused byElectrostatic forceAnd electrostatic spark. The most serious electrostatic discharge in electrostatic hazards causes fire and explosion of combustible materials.It is often said that the preventive measures to prevent static electricity are generally to transform the process links with strong electrification and use equipment and materials with less electrification.The simplest and most reliable way is to ground the equipment with wires, which can lead the electric charge to the ground and avoid the accumulation of static electricity.Careful passengers will probably find that;Discharge brushes are installed on both wing tips and the tail of the aircraft. When the aircraft lands, in order to prevent passengers from being shocked when flying down, the landing gear of the aircraft mostly uses special grounding tires or grounding wires;To discharge the static charge generated by the aircraft in the air.
We often see an iron chain at the tail of the tanker, which is the grounding wire of the tanker.Properly increase the humidity of the working environment so that the charge can be discharged at any time, which can also effectively eliminate static electricity.This is why it is not easy to do static electricity test in wet weather.The antistatic agent researched by the researchers can eliminate the static electricity inside the insulator well.
However, everything has two sides. For static electricity, as long as we understand its temper, we can also make it serve human beings.For example, electrostatic printing, electrostatic spraying, electrostatic flocking, electrostatic dedusting and port power separation technologies have been widely used in industrial production and life.static electricityThey also began to show their skills in desalination of seawater, pesticide spraying, artificial rainfall, low-temperature freezing and many other aspects, and even installed electrostatic devices such as electrostatic feeders on spaceships.
Basic overview
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Electrostatic effect
Generally, any object has positivenegative chargeIt is equivalent when compared with other objectsfriction, contact, and separation due to mechanical action, due to the different friction electrification sequence of two objects, it accumulates on one objectpositive chargeThe other object accumulates negativecharge, generate static electricity on various objects, and form static electricity field externally.Friction between two substances is a way to generate static electricity.Like water droplet adsorption in spraying operationIn airThe negative ions of N, N, N, N can promote the formation of double electric layers on its surface, which can also generate static electricity.The results of modern scientific research show that,Electric effect、Piezoelectric effect、conductor(or dielectric) electrostatic induction can produce static electricity.The electrostatic field generated by static charge has the following three physical effects that have a great impact on the electronic industry.
Electrostatic effect
For the reaction between ions, the dipole momentμBoth are zero, and the last term of the equation is zero, which becomes the single sphere activated complex modelBonn expression。For the interaction of dipoles, there is no net charge,ZBoth are zero, the second term on the right of the equation can be deleted, and the electrostatic effect is determined by the last term.For the reaction between ions and dipoles, the latter two terms must be included. Usually, the second term is small and is mainly predicted by the last term.But no matter what kind of reaction, the equation can use lnkFor 1/εDraw the linear relationship, the slope and the radiuschargeanddipole momentofBromoacetateandThiosulfateThis can be proved by the ionic reaction.It is difficult to use this equation for accurate quantification, but the semi quantitative relationship is very useful. It can show the influence of the dielectric constant on the reaction rate constant.
For example, when a neutral molecule is ionized, the activated complex has a large dipole momentμ＞μA、μB，According to this equation, the reaction rate constant increases with the increase of dielectric constant.This means that solvent with high dielectric constant is conducive to generating any particle with large dipole moment.For the interaction between ions, the last term of the equation can be deletedrA≈rB≈rAB,The result shows that: ① For the same numberIonic reaction, set lnkFor 1/εThe slope is negative, that is, the dielectric constant of the medium increases, and the reaction is accelerated; ②The reaction of different ions has a positive slope, the dielectric constant increases, and the reaction rate decreases.This is the result that the electrostatic coulomb force between ions is weakened by solvent molecules with high dielectric constant.static electricityThe action contributes to the activation free energy, so it affects the activation entropySIt also has contributions, thus affecting the frequency factor, which is proportional to the estimated frequency factorZAZB makes a jump change, which has been confirmed by experimental data.
preventive measure
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Anti static technology mostly follows the following three principles:inhibition、Dredging、neutralization。Because it is generally believed that it is impossible to completely prevent the generation of static electricity, but only to inhibit the accumulation of static charges. For example, strictly limit the transport speed of logistics and the operating speed of personnel, and try to make the equipment pipeline as smooth and flat as possible to avoid the occurrence ofAngularitywait.If you can't restrain it, try to dredge it and release it to the ground. For example, humidify the air in the workplace, ground all conductors, and lay conductors on the workbench and groundElectrostatic materialOperators wear static conductive clothing, shoes and socks, and even wear conductiveWrist strap Etc.
If not, try to neutralize in place, such asInductive suppressor、High voltage electrostatic eliminator、Ion wind eliminatorEtc.Although some measures have been taken to eliminate static electricity and achieved certain results, they have not completely eliminated static electricity hazards. After years of analysis and research on the application and effects of various anti-static means, people finally realize that those methods are still local prevention and control, and there are always areas that are not protected by prevention and control measures that may produce static electricity hazards,So people imagine whether they can find a comprehensive and environmental electrostatic prevention method.
The answer is yes. This is a new concept of modern electrostatic prevention -- all-round and all-around environmental electrostatic prevention. Different from the traditional electrostatic prevention concept, all-round and all-around environmental electrostatic prevention no longer focuses on specific parts or working surfaces that generate static electricity, but on the whole space of the whole working area. Its core is to eliminate allequipment、materiel、personnelThe possibility of electrostatic accumulation due to flow friction in all working processes of each link.This new concept has become the guiding principle for modern industry, office automation and household electronic equipment to prevent electrostatic hazards.According to this guiding principle, the following key technologies must be developed in order to achieve all-round and environmental electrostatic prevention:
1. In a relatively closed production or working environmentground、wall、ceilingTake corresponding measures to make it have good electrostatic conductivity.
2. Surface treatment measures shall be taken for all equipment worktops, chairs, etc., to effectively change the surface impedance of various materials so that they will not generate static electricity or static charges will not collect when subjected to friction.
3. Take comprehensive measures for the operation or staff in the environmentAnti static protectionTo minimize the static electricity of human body.
The anti-static measures taken above shall have nothing to do with the relative humidity of the ambient air, or the space of the environment shall be treated to increase the electrostatic conductivity coefficient of the air.
Structural factors
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polymerThe influence of its own structure on its chemical reaction performance is called polymer effect.Polymer effects mainly include the following:
1. Neighborhood effect
a. Steric hindrance effect: due to the steric hindrance of new successful energy radicals, it is difficult for adjacent functional radicals to continue to participate in the reaction.
b. Electrostatic effect: the electrostatic effect of adjacent groups can reduce or improve the reaction activity of functional groups.Such as polyacrylamideAcid catalyzed hydrolysisThe reaction rate increases with the progress of the reaction, because the carboxyl group generated by hydrolysis can form a cyclic transition state of acid anhydride with the adjacent unhydrolyzed amide group, thus promoting the departure of NH2 in the amide group to accelerate hydrolysis.andpolyacrylamideWhen hydrolyzed under strong alkaline conditions, when the adjacent groups of one amide group have been converted intoCarboxylateLater, because the attacking OH - and the COO - generated on the polymer chain have the same charge and repel each other, it is difficult to contact the attacked amide group and cannot be further hydrolyzed, so the degree of hydrolysis is generally below 70%.
