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Preparation and application of wear-resistant fluorine resin coating

Heistman 2013-6-5 12:30:15 Browse:5242 times

 

Preparation and application of
wear-resistant fluorine resin coating





Currently ,
because the fluorine resin coating having good heat resistance , weather
resistance, oil resistance , solvent resistance, and non- adhesive , and is
widely used in the textile , fiber, metal , plastic, rubber and other materials
coated or impregnated . Meanwhile fluorine resin coating can also be applied to
the heat roller office automation equipment ( such as copiers , printers ,
etc.) , heat tape or heat-resistant surface coating film , but in due course
the existence of non- adhesive coating abrasion lead decreased and other
issues.



The
long-term non- adhesive coating , the researchers had the heat -resistant resin
or rubber material , applying the aqueous coating was carried out, but due to
the fluorine resin film is formed thick , the substrate is missing follower
nature , occur due to thermal expansion of the substrate resulting in the
coating cracking and other issues.



In response
to these problems, this paper presents a good abrasion resistance and
long-lasting non- adhesive form a smooth coating of fluorine resin coating .
The polymeric resin coating is primarily an average particle size 0.3 ~ 5μm,
can be melted pulverized particles of the fluorine resin . Then the fluorine
resin particles to be dispersed in water to obtain a fluorine resin coating , a
surface active agent and an alcohol solvent. After the emulsion polymerization
and dispersing the resulting coating compared to the coating with good abrasion
resistance, non- adhesion persistence, forming a smooth coating propertie



Fluorine resin polymer particles



    11 Polymerization method



A fluorine
resin polymerization bulk polymerization , suspension polymerization, solution
polymerization, emulsion polymerization and the like. By the temperature ,
pressure, polymerization initiator and other additives to control other process
conditions , to obtain the desired fluororesin.



   In
order to obtain good coating properties , suspension polymerization is
preferably a fluorine resin obtained legally . After the fluorine-containing
resin obtained by suspension polymerization , and then coagulated and dried to
obtain an average particle diameter of the fluorine resin particles of 25 ~
1000μm .



    12 Polymerizing monomer



    In order to
obtain the fluorine resin polymer may be below 320
melt processing , the polymerizable monomer used may be of
tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymer (FEP), TFE /
perfluoroalkyl vinyl ether copolymer (PFA), TFE / HFP / perfluoroalkyl vinyl
ether copolymer (EPA), TFE / chlorotrifluoroethylene (CTFE) copolymers , TFE /
ethylene copolymer (ETFE), polyvinylidene fluoride ethylene (PVDF),
polytetrafluoroethylene molecular weight less than 300,000 (LMW-PTFE) and the
like.



    Molecular
fluoroalkyl vinyl ether as follows :


 
 
 
 
 
 
 
 
 
 
 
 






Perfluoroalkyl vinyl ether Formula



    From the non-
adhesive , the surface smoothness consideration , use FEP, PFA and EPA is
preferably a fluorine resin copolymer , considering the heat resistance , the
use of the copolymer is preferably PFA .



    13 Crushing method



   Pulverized
fluororesin in two stages , first at atmospheric pressure dry- crushing ,
crushed fluororesin is dispersed in an aqueous medium , then the pressure in
the high pressure 5 ~ 1000MPa pulverized to obtain the desired fluororesin
particles.



Dry crushing under
pressure , a fluorine resin and the high-speed rotating devices in the device
activity constant collision , friction and shear , impact and friction force
generated by the material to be ground until a constant up to a certain
fineness. This method is not used in a liquid medium. Equipment such as teeth
grinding mill, jet mill , turbo mill , knife mill and hammer mill and other
uses.



    In order to
obtain the desired particle size , sieved using a sieve and wind and grading .
The average particle diameter is preferably in the dry -milling between 25 ~
1000μm .



    In the
high-pressure pulverization, the fluorine resin particles dispersed in an
aqueous medium under high pressure , when the impact force is small , and the
action of vacuum generated by the discharge opening , to pulverization and
dispersion and emulsification . In the grinding process , can be used in two
ways : 1 ) under high pressure , the fluorine resin particles dispersed in an
aqueous medium , diversion, and then merging , shocks , friction, collision ,
to grinding, dispersion , emulsion ; 2 ) under high , fluororesin aqueous
solution discharged from the nozzle from the high pressure to normal pressure ,
as the pressure drop , to grinding, dispersion , emulsion and the like.
Discharge port diameter , with the required pressure and the fluororesin
particle size varies , the crushing effect can also be achieved by repeating
the operation .



    2·Additives



    21 Solvent



    After the
crushing pressure of water to be added organic solvent , water-soluble solvent
such as ethanol, surfactants , and the aqueous medium. From the grinding
efficiency, a fluorine resin, an aqueous medium is preferably insoluble , may
be added to an aqueous medium , a surface active agent and various additives in
a high-pressure pulverization like.



    Wetting the aqueous medium and the
fluorine resin having fluidity, high boiling point solvent is dried from the
effect of the retarder , after sintering the dried coating , the coating prevents
the occurrence of cracking. Even a high-boiling solvent was evaporated under a
molding temperature of the fluororesin , the coating film does not have an
impact. The aqueous medium used, such as boiling point lower than 100

methanol , ethanol, tert-butanol , acetone, methyl ethyl ketone and other
organic solvents ; boiling point of the organic solvent such as methyl
cellosolve ( methoxyethanol ) 100 ~ 150
, and ethyl cellosolve ; A boiling point of above 150 N, N- dimethylacetamide
, N, N- dimethylformamide , ethylene glycol, propylene glycol, glycerin, butyl
cellosolve , 1,4 - butanediol , diethylene glycol , triethylene glycol ,
tetraethylene glycol high -boiling organic solvent. If a mixture of two or more
solvents to better dispersion stability of the fluorine resin coating , this
safety considerations, select a high boiling point solvent glycols better .



    Add 1% to 30% of total
accounts coating solvent is good. When using a low boiling organic solvent ,
add less , bubbles are easily generated internally , the addition amount is
large, the aqueous dispersion is easily formed in the combustion ; boiling
organic solvent when in use , the addition amount , after coating and drying ,
the recovery of fluorine resin not sintered powder , the added amount of
residual easily in the coating film , impact on the environment after sintering
; high-boiling organic solvent , the amount is large, there is left in the
coating after sintering , the impact on the environment .



22 Surfactant    Surfactant is fluororesin
particle comprises 15% to 80% coating uniformly dispersed. Anionic surfactants
, cationic surfactants, nonionic surfactants and amphoteric surfactants. E.g. ,
sodium alkyl sulfate , alkyl ether sulfate, triethanolamine alkyl sulfate ,
triethanolamine alkyl ether sulfate , ammonium alkyl sulfate , ammonium alkyl
ether sulfate , alkyl ether phosphate , and sodium fluoroalkyl carboxylate
anionic surfactant ; ammonium salt , alkyl benzyl ammonium salt cationic surfactant; Polyhydroxy alkyl vinyl esters, propylene glycol -
propylene oxide copolymer , perfluoroalkyl ethylene oxide by-product 2 -
ethylhexyl alcohol ethylene oxide additions such nonionic surfactants ;
alkylamino acid betaines, alkylamido betaine , betaine amphoteric surfactants
such as imidazole and the like. Wherein the anionic and nonionic surfactant is
preferably less after the thermal decomposition of the residual hydroxyl
ethylene chain nonionic surfactants are preferred. May also be used alone or in
combination of hydrocarbons , fluorine , silicon , acetylenic surfactants.
After the coating was dried by heating them in the coating film does not remain
such surfactants , less impact on the environment from the viewpoint of
surfactant is preferably ethynyl .



    The
amount of surfactant added is usually 0.2% to 20% of the amount of fluorine
resin , the addition amount , the uneven dispersion of the fluorine resin ,
floating portion . Added amount , sintering , multi- residue surfactant
decomposition , easy to color , the heat resistance of the coating , the non-
adhesion decreased .    



23 Other Additives



    The
fluorine resin coating , are also typically added other additives such as
pigments , stabilizers, thickening agents, decomposition accelerators , rust
preventives , preservatives, defoamers and the like. The pigment may be inorganic
pigments, compound oxide pigments , such as carbon black , white carbon,
calcium carbonate, barium sulfate, talc ( powder ) , calcium silicate and the
like. Desired color pigments can be added as needed .



    3·Select base



Coated substrate may be iron, stainless
steel , copper, aluminum , brass and other metals , glass, glass fiber woven
fabric and nonwoven fabric of glass products. Polypropylene , polyimide ,
polysulfone , and other common materials; heat-resistant resin and the coated
article ; SBR, BR, NBR, EPDM, silicone rubber, fluorine rubber, and rubber
coated article ; natural fibers and synthetic textile fabrics and nonwovens .



   Coating a
substrate with the heat-resistant rubber layer may be , which can hold the
fluororesin sintering temperature ( typically 250 ~ 400
) rubber , fluorine
rubber and silicone rubber. Fluorine rubber having heat resistance and good
adhesion with the advantages of a fluorine coating film is formed to improve
the adhesion and heat resistance of the coating rubber layer . Silicone rubber
is a polymer consisting of alkoxy silane or alkoxy silane composition and an
organic titanate .



    4·Coating
methods



   There are
many , such as spray coating , roll coating, blade coating , dip coating method
for coating - centrifugal coating, dip coating, spin coating, curtain coating
method and the like . After coating, by drying and calcining to obtain coated
articles . Drying to remove the aqueous medium , such as at room temperature ~
120
, heating 5 ~
30min. Sintering is above the melting temperature of the fluororesin , i.e. 200
~ 400
, calcination
time is preferably 10 ~ 60min .



   Laminating order is
usually coated article : a substrate , the heat resistance of the rubber layer
, a fluorine resin coating , or the substrate , primer, coating fluororesin .

The fluorine resin coating , the amount of fluorine resin to account for 20 %
to 50 % of the total weight of the preferred . When the amount is less than the
lower limit of fluorine resin , low viscosity when the substrate surface
coating, easy to shed , not coated with thick ; excessive amount of paint flow
is not good, not easy to paint . Specific amount according to the coating
method and coating thickness can be adjusted within the above range .



    5·Preparation
of test



    51
experiment



    511
PFA

PFA fluororesin coating formulation



    1) Smash



   After drying to obtain a
monomer tetrafluoroethylene (TFE) and perfluoro vinyl ether (PFVE) by
suspension polymerizing a copolymer PFA ( melting point 300 ℃, MFR25g/10min),
jet mill and then pulverized to an average particle PFA powder of 10μm diameter
.    2)Premixed



 The obtained 100 parts by weight of PFA
fine powder and 10 parts of acetylene glycol dispersing agents , nonionic surface
active agent and 10 parts of ion- exchanged water 280 parts mixture was
sufficiently stirred to obtain a dispersion of PFA .



    3) Crushing,
emulsifying



The PFA dispersion was
filtered through a 100 mesh screen , and then high-pressure emulsifying machine
to obtain an average particle size of 0.6μm PFA emulsion.   



 4)Coating



    PFA 100 parts by weight
of the emulsion , a nonionic surface active agent 2.5 parts , 2.5 parts of
ethylene glycol , 20 parts of ion- exchanged water to obtain the desired coating
mixture .



    512
The
production of coated plate



   1 ) coated plates 1

Within 15min, the 80 ~ 100 ℃, the surface of the aluminum plate was washed with
acetone , PFA spray coating, drying, cooling , place the room temperature to
obtain a coating thickness of about 30μm . Then, the coated plate PFA spray
coating , and dried at room temperature for 1h, and dried at 80 ~ 100 ℃ for
15min , and calcined at 250 ℃ 60min, calcined or 325 ℃ 30min, to obtain a
coated plate thickness of 35μm .



  2 ) coated plates 2

First, the aluminum surface blasting , reaching 2 ~ 3.5μm roughness. Then , the
primer coating thickness of 10 ~ 15μm , the 80 ~ 100 ℃ dried 15min, cooled.
Then spray PFA coating thickness of 15μm or more , after 80 ~ 100 ℃ drying
15min, and then calcined at 380 ℃ 15min, cooled to room temperature .



    5.1.3 Coating
Performance Evaluation

1 ) film appearance

In coated plate 1 , coating the surface of the visual crack , bubble , swelling
of absence .

2 ) Surface roughness

In the coated sheet 1, the coating film was measured with a surface roughness
meter of the surface roughness Rz ( measured length = 4mm).

3 ) Gloss

1 coated plates with variable angle gloss meter surface gloss of the coating
film (60 ~ 60 °).

4 ) Contact angle

In a drop of water on the coated plate with a contact angle goniometer .

5 ) taper wear test





   500g weight of the
coated sheet 2 , heated on a taper wear wheel abrasion test machine . After the
coated plate is fixed on the apparatus , heated to 200 ℃, was measured before
and after 1000 revolutions of the rotating mass , the amount of wear is to
reduce the amount .

5.2 Experiment 2

In Experiment 1 , except that PFA pulverization , the emulsification step , the
average particle diameter became 0.8μm outside , the same test was performed
and an experiment .

5.3 Experiment 3

In Experiment 1 , except that PFA pulverization , the emulsification step , the
average particle diameter became 1.0μm outside , the same test was performed
and an experiment . 5.4 Comparative Experiment



    1 ) Comparative Example 1

In Experiment 1 , except instead of the PFA powder coating with other PFA
dispersion ( average particle size 0.3μm), for the same tests as in Example 1 .

2 ) Comparative Example 2

In Experiment 1 , except instead of the PFA powder coating with an aqueous
coating PFA (average particle diameter 25μm), for the same tests as in Example
1 .

3 ) Comparative Example 3

In Experiment 1 , except cancel crushing, emulsifying step , the same test was
performed , and an experiment .

6 • The experimental results

Examples and Comparative experimental results shown in Table 1 .



Table 1 Test results of Examples and Comparative

7 • Conclusion

The coating film formed by coating a fluorine resin having excellent abrasion
resistance, non- adhesive , film smoothness and so on.

Use of the paint coating of articles , and more suitable for use in heat
resistance, solvent resistance , lubricity, non- adhesive condition. Such as
heat rollers used on copiers, printers and other office automation equipment ,
tapes, films, sleeves , sheets, hoses , chemical resistance , flame tubes,
seals and other chemical equipment .