Conveyor belt causes static and anti-static methods
Polyvinyl chloride (PVC) plastic conveyor belt as a new product, with its light weight, long life, good flame resistance, not easy to produce friction, etc., are widely used
in coal, mining and various factories and enterprises. However, because PVC is a good insulator, the surface resistance, poor conductivity in the coal-rich gas that occasion and
easy to produce static electricity, vulnerable to accumulation of static electricity caused an explosion or fire or other serious accidents. Therefore, the need to improve the
flame-retardant PVC belt formulation design antistatic properties.Heat Exchanger
Electrostatic generation mechanism and anti-static methods
An electrostatic generation process uses plastic and rubber material in the coal mine conveyor belt is running, due to the friction caused by the body with positive and negative
charges arising from loss of balance electrostatic charge, electrostatic charge accumulated on the belt surface is not easy to disappear, When it reaches a certain value, be
grounded object produce sparks, causing a fire or gas explosion.
Currently static method, the plastic antistatic methods is to control the generation and accumulation of static electricity, the generation of static electricity is mainly
controlled by reducing friction and to reduce or prevent the generation of static electricity; control accumulation of static electricity by grounding conduction mainly to
increase the relative humidity and adding antistatic agent or a conductive material (such as conductive carbon black, metal powder) to accelerate static leakage to avoid large gravity skatewheel conveyor
accumulation of static electricity.
Therefore, in order to make good insulation properties of the plastic has a certain conductivity, mainly the following methods: ① adding antistatic agent in plastics or
antistatic agent for surface coating of the article. ② to add a conductive filler in plastics (such as conductive carbon black, metal powder). ③ polymer by graft
copolymerization of changing the structure to a group with a more polar or ionic groups, to increase conductivity. ④ with strong oxidants plastic surface to increase
Retardant PVC conveyor belt in the actual production process, the general formulation of the covering layer and the conductive filler added antistatic agent approach to reduce
the belt and the volume resistivity of the surface resistance, it has a certain anti-static properties.
Second, anti-static formula for coal exploration and discussion with PVC flame retardant conveyor speaking, antistatic formula is a very important issue, in order to run the
conveyor electrostatic charge generated in the process itself, in a timely manner through conduction and leak out, We must process conditions, production costs, and other
factors to consider, select the appropriate antistatic agent and a conductive material, to reduce the surface resistance of flame-retardant PVC conveyor belt to ensure that the
conveyor belt surface resistance of less than 3 × 10 8Ω.
Antistatic agents choose to make flame-retardant PVC conveyor belt has good antistatic properties, currently used in the recipe is the traditional method of adding quaternary
ammonium cationic antistatic agents; while proved quaternary ammonium cationic antistatic Although strong adhesion agents, antistatic performance, but it is in actual use, there
are many shortcomings. First, the quaternary ammonium antistatic agent itself is inferior in heat resistance, easy to heat decomposition, can reduce the thermal stability of PVC
resin, PVC resin to accelerate the aging process, which point we use single fatty alkyl trimethyl ammonium halides antistatic agent for the production process has been fully
confirmed; secondly, cationic quaternary ammonium antistatic agent formulation with the flame-retardant PVC conveyor lead stearate, barium stearate, metal soap-based heat
stabilizer chemical reaction to form stable complexes, thus affecting conveyor antistatic effect, reduces the thermal stability of the resin. Therefore, heat-resistant conveyor
belt requires a very high flame-retardant PVC should not be used during the production of cationic quaternary ammonium antistatic agent, use thermal stability and excellent
antistatic properties are very non-ionic antistatic agent.
PVC conveyor belt according to the actual processing conditions and take the antistatic agent used in the formulation of other additives and the mutual influence of this ester
using the non-ionic antistatic agent to reduce the surface resistance of flame-retardant PVC belt. Non-ionic antistatic agent good heat resistance, good compatibility with other
additives, not ionic antistatic agent is liable to cause aging of plastic disadvantage during use in the processing of physical and mechanical properties of the products and no
adverse effects. Such antistatic agent is the main mechanism are: ① the hydrophilic group of the antistatic agent to increase the surface of the absorbent article to form a
conductive monomolecular film; ② in the plastics antistatic agent molecular layer formed on the surface, increase the product surface smoothness, thereby reducing friction,
reduce static charge generation. After repeated tests proved that the amount of more than 30 parts of plasticizer, flame retardant added to the formulation belt cover layer
non-ionic antistatic agent KJ - 210, and a flame retardant three (β-chloroethyl) phosphate (TCEP), After mixing to evenly dispersed in the originally non-conductor PVC plastic,
the molding belt can gradually migrate to the surface, forming an antistatic molecular layer, thereby reducing the resistance of the belt surface, the flame-retardant PVC
conveyor belt has good resistance to electrostatic properties and flame retardance.
Conductive material of choice because black is a natural semiconductor materials, conductive performance lasting stability, can significantly adjust the resistivity of polymer
materials, coupled with wide variety of sources, the price is cheap, therefore, the choice of carbon black as a conductive filler. From lower production costs and many other
factors to consider, this recipe uses acetylene black as a conductive material.
Using carbon black as a conductive material, to reduce the volume resistivity of PVC plastic, it has a certain conductivity. Usually people think, carbon black is dispersed in
the PVC resin particles, with the increase in the amount of carbon black added, the particle spacing shrinking, proximity or contact when the particle is formed when a large
number of conductive network channel, PVC plastic conductivity of the is greatly increased. But PVC plastic products resistivity decreased, the added amount of carbon black is
not a linear relationship, when the additive amount reaches a certain, even if the carbon black to increase its conductivity changes no longer significant. According to the
information reported when greater than 7 parts of carbon black added after the network has been the formation of a conductive carbon black, carbon black to add more products to
PVC plastic surface resistance has little effect, but with the increasing amount of carbon black, PVC plastic tensile strength, impact strength, elongation dropped
significantly, the hardness was increased, and in the PVC plastic combustion will produce red embers, reduce flame-retardant effect. Therefore, to solve the problem retardant
PVC antistatic conveyor belt only carbon black method is more desirable, to select the best usage.
It is intended that the best flame-retardant PVC anti-static conveyor formula of: PVC, 100; KJ - 210, 7; acetylene black, 5; TCEP, 9; stabilizer, 6; lubricants, processing aids,
Experimental process and test results 3.1 Process and Requirements retardant antistatic PVC conveyor belt of the trial process is as follows: PVC resin, various additives mixing
kneading mastication kneading rolling flat molding sample temperature control: 105 ~ 115 ℃. Two roll mill Temperature Control: front roll, 150 ~ 155 ℃; After the roll, 145 ~
150 ℃. 3-roll calender temperature control: the upper rollers, 140 ~ 145 ℃; the rollers, 150 ~ 155 ℃; lower roll, 90 ~ 100 ℃. Flat molding temperature control: the maximum
temperature does not exceed 165 ℃.
Test results using the antistatic formula, through production processing conveyor belt made of flame-retardant PVC antistatic by the National Coal Mining Machinery Quality
Supervision and Inspection Center, its conductive properties and flame retardant properties are in line with MT914 - 2002 "the whole fabric for use in mines flame retardant
conveyor belt "standards, the performance test results as shown.
In the production of flame-retardant PVC conveyor belt, adding non-ionic antistatic agent KJ - 210, and a conductive material of acetylene black, it is possible to reduce
production costs, greatly improve the PVC conveyor antistatic properties and flame retardance and it has good mechanical properties.