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Abstract: Mainly aiming at the requirements of communication equipment, the influence of different types of resins, fillers and catalysts on weather resistance was studied, and special powder coatings
for communication equipment with excellent solvent resistance, salt spray resistance, good adhesion and weather resistance were developed.
With the improvement of people's living standards and entering the information age, various communication equipment has been integrated into people's lives, and the base station communication equipment that provides signals for these wireless communication devices is naturally very important
.
Generally, powder coating as a decorative material, base station communication equipment is often coated with powder coating protection, the performance of powder coating coating is of great significance to the continuity and stability of communication signals coating online coatingol.
com
.
The powder coating involved in this study is mainly applied to the coating protection of communication equipment (Ethernet switches, large routers, communication servers and controllers, etc.
) of communication cabinets, chassis, and plug-in boxes of communication base stations to ensure that these equipment can operate normally under various climatic conditions
.
Therefore, it is required that the powder coating of such communication equipment has excellent salt spray resistance, scratch resistance, organic solvent stability and good weather resistance
.
1.
Test part
1.
1 Raw materials and formulas
The basic formula of powder coating for communication equipment is shown
in Table 1.
1.
2 Main equipment and instruments
Twin screw extruder, crusher, ACM milling equipment, electrostatic spraying equipment, salt spray test chamber, impact meter, thickness gauge, xenon lamp exposer instrument, hundred grid tester, etc
.
1.
3 Test methods
Weigh the raw materials according to the formula, mix evenly in the mixing cylinder, extrude by twin screw extruder, crush by high-speed crusher after cooling and crushing, and obtain powder coating
with particle size (equivalent particle size D50) of 30~50μm by rotary sieve.
2.
Results and discussion
2.
1 Effect of polyester resin acid value on weather resistance
In general, the curing reactivity of the system is not only related to the type of curing agent, but also affected by the amount of curing agent
.
In this experiment, terminal carboxyl polyester resin, triglycidyl isocyanurate (TGIC) curing agent, catalyst, auxiliaries and outdoor pigment filler were used as raw materials, and the coating performance under different acid values of polyester resin was compared, and the results are shown
in Table 2.
Abstract: Mainly aiming at the requirements of communication equipment, the influence of different types of resins, fillers and catalysts on weather resistance was studied, and special powder coatings
for communication equipment with excellent solvent resistance, salt spray resistance, good adhesion and weather resistance were developed.
With the improvement of people's living standards and entering the information age, various communication equipment has been integrated into people's lives, and the base station communication equipment that provides signals for these wireless communication devices is naturally very important
.
Generally, powder coating as a decorative material, base station communication equipment is often coated with powder coating protection, the performance of powder coating coating is of great significance
to the continuity and stability of communication signals.
The powder coating involved in this study is mainly applied to the coating protection of communication equipment (Ethernet switches, large routers, communication servers and controllers, etc.
) of communication cabinets, chassis, and plug-in boxes of communication base stations to ensure that these equipment can operate normally under various climatic conditions
.
Therefore, it is required that the powder coating of such communication equipment has excellent salt spray resistance, scratch resistance, organic solvent stability and good weather resistance
.
1.
Test part
1.
1 Raw materials and formulas
The basic formula of powder coating for communication equipment is shown
in Table 1.
1.
2 Main equipment and instruments
Twin screw extruder, crusher, ACM milling equipment, electrostatic spraying equipment, salt spray test chamber, impact meter, thickness gauge, xenon lamp exposer instrument, hundred grid tester, etc
.
1.
3 Test methods
Weigh the raw materials according to the formula, mix evenly in the mixing cylinder, extrude by twin screw extruder, crush by high-speed crusher after cooling and crushing, and obtain powder coating
with particle size (equivalent particle size D50) of 30~50μm by rotary sieve.
2.
Results and discussion
2.
1 Effect of polyester resin acid value on weather resistance
In general, the curing reactivity of the system is not only related to the type of curing agent, but also affected by the amount of curing agent
.
In this experiment, terminal carboxyl polyester resin, triglycidyl isocyanurate (TGIC) curing agent, catalyst, auxiliaries and outdoor pigment filler were used as raw materials, and the coating performance under different acid values of polyester resin was compared, and the results are shown
in Table 2.
As can be seen from Table 2, the salt spray resistance and physical properties of resin D (20~28mgKOH/g) coating are relatively poor, and resin B (30~35mgKOH/g) performs well
in all aspects.
The weather resistance of resin C (40~50mgKOH/g) and D (20~28mgKOH/g) is slightly worse, and resin A (30~35mgKOH/g) has better coating performance in all aspects, and the price is more reasonable
.
Resin A has excellent properties, and although resin B performs well in all aspects, it is more expensive
.
Resin A
is selected for comprehensive performance and cost considerations.
Secondly, the resin of different acid value types was selected in the experiment, and according to the requirements of special powder for weather-resistant communication equipment, the resin D acid value was low, the crosslinking density was insufficient during heating and curing, the curing was not complete enough, and the mechanical properties and weather resistance of the coating were slightly worse;
Saturated end carboxyl polyester resin is made of polyol and polyacid polymerization, resin C acid value is high, for the preparation of high acid number polyester resin usually add trimellitic anhydride, trimethylolpropane raw materials
.
The use of trifunctional monomer will cause mild cross-linking of the resin itself, thereby affecting the fluidity of the resin, so that the prepared powder coating appears orange peel and thus affect the luster, so the coating leveling and weather resistance prepared by resin C are slightly worse
.
In addition, the cost of high acid number resin C is high, so polyester resin
with high acid value is not suitable.
In summary, resin A, that is, saturated end carboxyl polyester resin with an acid value of 30~35mg KOH/g, is appropriate
.
2.
2 Effect of wrinkle agents on weather resistance
It can be seen from Table 4 that the extruded CAB, P-115 wrinkle agent has a strong three-dimensional sense and is easy to expose the bottom, and when it is produced, the grain is unstable and not easy to control, which will reduce the production efficiency when preparing powder, and the cost of such wrinkle agent is high
.
So don't choose
.
The external mixed wrinkle agent BBM can produce a strong three-dimensional orange pattern, but white spots are easy to appear when wiping with xylene, and the commercial wrinkle agent does not react with the coating, and it is easy to float on the surface of the coating when curing, and the weather resistance is slightly worse, so less commercial wrinkle agent
is used in the production of powder.
Due to the addition of pigment filler and curing agent, the particle size and density of the self-made wrinkle agent D are comparable to the base powder, and the spraying and recycling process are not easy to separate, and have good construction stability
.
Finally, the homemade wrinkle agent has the same color as the primer, reacts with the coating when cured, does not appear white spots when wiping with xylene resistance, and has excellent
weather resistance.
In summary, it is appropriate
to choose homemade wrinkle agent D with excellent weather resistance and good construction performance.
2.
3 Effect of catalyst on coating properties
The catalyst can significantly reduce the coating film forming temperature or shorten the coating curing time, and at the same time improve the surface properties, weather resistance and outdoor stability of the coating, and reduce the crosslinking reaction temperature and accelerate the reaction speed
in powder coating.
With the increase of catalyst usage
(1) The reaction speed gradually increases, the crosslinking density gradually increases, and the weather resistance of the coating gradually improves;
(2) The gelling time gradually becomes shorter, the viscosity of the system gradually increases, and the coating is cured when the melting leveling is not sufficient, so the leveling of the coating gradually deteriorates;
(3) Excess catalyst will reduce the storage stability
of powder coatings.
Comprehensive performance, cost and customer consideration of coating grain characteristics, coating site and use requirements
.
The recommended dosage of catalyst is 0.
3%~0.
6%.
2.
4 Effect of salt spray resistance additives on coating properties
It can be seen from Table 6 that the addition of salt spray resistant additive A to Formula 13 has the same effect as formula 12 without salt spray resistance additives, and the adhesion is grade
1.
It shows that the salt spray resistant additive has no obvious effect on this formula, and the adhesion of salt spray resistant additives B and C is 0 grade
.
The salt spray resistant additive is a mixture of a variety of organic complexes, which can produce a resistance effect in the coating, a potential difference with the metal cation, and a shielding effect
.
It can form an inert inorganic complex layer with metal to prevent oxidation, corrosion and other effects, so as to delay metal corrosion; It can improve the adhesion between the coating and the metal substrate, and at the same time improve the moisture resistance
of the coating and the metal.
This improves the salt spray resistance
of the coating.
Since the price of C is higher than B, in the powder coating of this weather-resistant communication equipment, the economical salt spray resistant additive B
is selected.
3.
Conclusion
The study found that:
(1) The saturated end carboxyl polyester resin with acid value of 30~35mg KOH/g is selected, and the polyester/TGIC system with excellent weather resistance can ensure the weather resistance and impact resistance
of the leveling powder coating.
(2) In terms of wrinkle powder coating, the selection of suitable homemade wrinkle agent D is conducive to improving the construction stability and adaptability of wrinkle powder; The selection of suitable catalysts is conducive to improving the crosslinking density and weather resistance of coatings.
(3) The addition of suitable salt spray resistance additives can significantly improve the salt spray resistance of the coating, so as to obtain the powder coating
of communication equipment with excellent salt spray resistance, organic solvent stability and good weather resistance.
As can be seen from Table 2, the salt spray resistance and physical properties of resin D (20~28mgKOH/g) coating are relatively poor, and resin B (30~35mgKOH/g) performs well
in all aspects.
The weather resistance of resin C (40~50mgKOH/g) and D (20~28mgKOH/g) is slightly worse, and resin A (30~35mgKOH/g) has better coating performance in all aspects, and the price is more reasonable
.
Resin A has excellent properties, and although resin B performs well in all aspects, it is more expensive
.
Resin A
is selected for comprehensive performance and cost considerations.
Secondly, the resin of different acid value types was selected in the experiment, and according to the requirements of special powder for weather-resistant communication equipment, the resin D acid value was low, the crosslinking density was insufficient during heating and curing, the curing was not complete enough, and the mechanical properties and weather resistance of the coating were slightly worse;
Saturated end carboxyl polyester resin is made of polyol and polyacid polymerization, resin C acid value is high, for the preparation of high acid number polyester resin usually add trimellitic anhydride, trimethylolpropane raw materials
.
The use of trifunctional monomer will cause mild cross-linking of the resin itself, thereby affecting the fluidity of the resin, so that the prepared powder coating appears orange peel and thus affect the luster, so the coating leveling and weather resistance prepared by resin C are slightly worse
.
In addition, the cost of high acid number resin C is high, so polyester resin
with high acid value is not suitable.
In summary, resin A, that is, saturated end carboxyl polyester resin with an acid value of 30~35mg KOH/g, is appropriate
.
2.
2 Effect of wrinkle agents on weather resistance
It can be seen from Table 4 that the extruded CAB, P-115 wrinkle agent has a strong three-dimensional sense and is easy to expose the bottom, and when it is produced, the grain is unstable and not easy to control, which will reduce the production efficiency when preparing powder, and the cost of such wrinkle agent is high
.
So don't choose
.
The external mixed wrinkle agent BBM can produce a strong three-dimensional orange pattern, but white spots are easy to appear when wiping with xylene, and the commercial wrinkle agent does not react with the coating, and it is easy to float on the surface of the coating when curing, and the weather resistance is slightly worse, so less commercial wrinkle agent
is used in the production of powder.
Due to the addition of pigment filler and curing agent, the particle size and density of the self-made wrinkle agent D are comparable to the base powder, and the spraying and recycling process are not easy to separate, and have good construction stability
.
Finally, the homemade wrinkle agent has the same color as the primer, reacts with the coating when cured, does not appear white spots when wiping with xylene resistance, and has excellent
weather resistance.
In summary, it is appropriate
to choose homemade wrinkle agent D with excellent weather resistance and good construction performance.
2.
3 Effect of catalyst on coating properties
The catalyst can significantly reduce the coating film forming temperature or shorten the coating curing time, and at the same time improve the surface properties, weather resistance and outdoor stability of the coating, and reduce the crosslinking reaction temperature and accelerate the reaction speed
in powder coating.
With the increase of catalyst usage
(1) The reaction speed gradually increases, the crosslinking density gradually increases, and the weather resistance of the coating gradually improves;
(2) The gelling time gradually becomes shorter, the viscosity of the system gradually increases, and the coating is cured when the melting leveling is not sufficient, so the leveling of the coating gradually deteriorates;
(3) Excess catalyst will reduce the storage stability
of powder coatings.
Comprehensive performance, cost and customer consideration of coating grain characteristics, coating site and use requirements
.
The recommended dosage of catalyst is 0.
3%~0.
6%.
2.
4 Effect of salt spray resistance additives on coating properties
It can be seen from Table 6 that the addition of salt spray resistant additive A to Formula 13 has the same effect as formula 12 without salt spray resistance additives, and the adhesion is grade
1.
It shows that the salt spray resistant additive has no obvious effect on this formula, and the adhesion of salt spray resistant additives B and C is 0 grade
.
The salt spray resistant additive is a mixture of a variety of organic complexes, which can produce a resistance effect in the coating, a potential difference with the metal cation, and a shielding effect
.
It can form an inert inorganic complex layer with metal to prevent oxidation, corrosion and other effects, so as to delay metal corrosion; It can improve the adhesion between the coating and the metal substrate, and at the same time improve the moisture resistance
of the coating and the metal.
This improves the salt spray resistance
of the coating.
Since the price of C is higher than B, in the powder coating of this weather-resistant communication equipment, the economical salt spray resistant additive B
is selected.
3.
Conclusion
The study found that:
(1) The saturated end carboxyl polyester resin with acid value of 30~35mg KOH/g is selected, and the polyester/TGIC system with excellent weather resistance can ensure the weather resistance and impact resistance
of the leveling powder coating.
(2) In terms of wrinkle powder coating, the selection of suitable homemade wrinkle agent D is conducive to improving the construction stability and adaptability of wrinkle powder; The selection of suitable catalysts is conducive to improving the crosslinking density and weather resistance of coatings.
(3) The addition of suitable salt spray resistance additives can significantly improve the salt spray resistance of the coating, so as to obtain the powder coating
of communication equipment with excellent salt spray resistance, organic solvent stability and good weather resistance.
