请问有谁能说说铁佛龙是怎样焊接的??

sqqd.12

我们做线路板设备的,有时用到铁佛龙这个材料,不过由于焊接技术的不成熟,使用时有很大的局限性,在三维上看能不能找到一些好的解决方法!

hanjixian

聚四氟乙烯在熔点以上(380℃)其黏度仍有1010～1011Pa·s，即使加高温度也只会分解而不流动，因此对聚四氟乙烯材料的焊接区别于其他热塑性塑料。聚四氟乙烯的焊接有热压焊和热风焊两种，热压焊接是将焊接的两片PTFE材料加热至高于熔点，在不太大的压力下，将两片材料压合在一起。热风焊接是用与聚四氟乙烯性能相仿的熔融加工的氟塑料如四氟乙烯-全氟烷基能乙烯基醚共聚物(PFA)作焊条，用热空气将焊条与待焊的聚四氟乙烯同时加热、加压，使聚四氟乙烯材料通过焊条连接在一起。

lihui98765

? 基本不能焊...2楼说的只针对膜...厚点就不行了..
能具体说说电路板哪边要用PTFE? 如果是加工PTFE电路板..怎么会需要焊接的?

lihui98765

查了下..还是可以焊的..把资料给你..
16.4 Welding and Joining
The bonding techniques involving adhesives are
/ ?, r) L5 B$ A) C! Bnormally suitable for applications where the fluoropolymer
) [! _: o7 C9 ~  S& S: ~. ldoes not carry large loads such as those
3 U4 u  R7 p* s3 D6 U+ x5 vexperienced by chemical processing equipment.
) `# j! y0 Y0 rWelding or adhesiveless joining is a method by which
5 G: q4 q0 I/ @6 W1 _& `parts for load-bearing applications are manufactured.
1 ]  k- O5 K7 D: N3 y5 e2 d5 nThe load could consist of temperature, chemical corrosion,
3 L# R' e# p* C- f" C" \1 gand force. This method also known as welding
or joining allows economical fabrication of complex
3 w- w9 J. r( }! i- X1 p3 J7 I% gparts by joining individual components.
3 T; c% R+ `3 ~( y* R" \( M* fIt is possible to obtain a good bond between fluoropolymers
" {6 R. a; g% m) M9 zthemselves, without the use of adhesives,
by application of heat and pressure. Pressure can help
0 q( z- t) Z9 M: [; u" m- adrive the molten polymer into the pores of the substrate.
Bond strength is dependent on the mechanical
interlocking that is achieved by the adhesion mechanism,
improving with increased surface roughness of
0 x2 g! z4 s# L$ ~the substrate. Examples of parts made by this technology
( H1 h$ t, I, e! ninclude glass cloth-backed polytetrafluoroethylene
, E) h( N. R8 k5 h2 V2 Asheet, or multi-ply circuit board and coated
1 o) [9 Z. d* |aluminum or copper sheet. Achieving this type of
bonding is more complex with polytetrafluoroethylene
% m" G6 Y1 q; R% |9 b) n& c4 O  ]than melt processible polymers. PTFE does not flow
after melting due to its extremely high viscosity.
6 |. `/ |9 W0 D) U1 ^' R/ o/ fIt is possible to achieve adhesiveless bonding using
standard PTFE in special applications where the
5 ?8 ]6 l, \* I4 Y3 Z- J) L( spolymer can be heated to a temperature well above its
melting point. It can then be forced under pressure
into the substrate surface. These polymers are not
suitable for applications where the geometry of the
joining objects must be preserved, contact surfaces
$ B9 s& R9 B% l" m+ _" j. _are smooth, or the objects being bonded are too large.
3 H' a, u0 n! J  Z7 D$ XIn such cases, a different type of polytetrafluoroethylene
8 B5 h- I% Z+ I; x9 wis required.
$ |: r  J( ^' D- u) D: vPolytetrafluoroethylene for these applications is
1 N. t( @7 C! ^- U0 d8 B- n8 h# K3 tknown as “modified” which refers to the presence of
a small amount of a second perfluorinated monomer,
" I3 Z/ s# S5 ]  Z* `; n/ i: {$ ~known as a modifier, in its structure. The modifier
& w, m4 c" C! e8 k! Qmolecule always contains a pendent group. The
preparation method of this type of PTFE has been described
in Ch. 5. Its commercial grades have been
described in Ch. 6.
3 {! p7 x+ n0 j8 ~How does it work? A simple explanation is offered
' ?3 y; y' b( v0 y: F+ C5 vhere, based on the author’s own experience. The
modification reduces the molecular weight of the polymer,
which in turn reduces its melt viscosity. Lower
4 A# d$ s+ J- {+ B, l$ I$ \! rmelt viscosity increases the mobility of the polytetrafluoroethylene
chains. This facilitates diffusion and
8 |0 q. g/ j& E- P8 @$ y5 G5 yentanglement of polymer chains at the bonding interface.
The pendent group of the modifier disrupts the
crystals of PTFE, thus preventing excessive crystallization.
0 g0 u8 t  u3 \9 r0 ]: o' WCrystallinity which is too high results in poor
3 L+ P% u$ Z/ u2 i# m& n9 u' ~mechanical properties such as poor tensile and flex
properties. An optimally modified PTFE has good
mechanical properties in addition to weldability.
' o2 K* q) [8 E& G! B" y, xWelding can be achieved using PTFE made by
dispersion or suspension polymerization. Most applications
involve welding of parts made from granular
( q$ W" e8 v( G* J) f2 @resins (suspension polymer). Dispersion polymerized
PTFE is also used for application such as wire
: x! d+ e! B3 P7 }$ @7 kcoating. A thin (50–100 μm) tape of the “modified”
polytetrafluoroethylene is wrapped around the conductor
followed by sintering. The layers of the tape
adhere to each other and form a solid insulation, due
+ A1 b% Z- K0 W+ m/ j( ^& p- v) B: nto its good interlayer adhesion, around the conductor
at the completion of sintering cycle.
& u; ]! ^( c* L3 [( H8 P+ ]- v16.4.1 Welding Technique
2 c3 e! N% |8 g' X% j: F# VQuality of a welded area is defined by the strength
of the bond. One of the ways to measure bond strength
is to cut a microtensile bar specimen in such a way
, n1 G2 Q& t" t% zthat the weld line would fall near its center (Fig. 16.5).
( e' p+ @) o. G* aTensile strength and elongation can be determined by
; o! y+ g$ V' v) Vextensiometry. Weld factor is defined by Eq. 16.1 as
* v: _% N8 _# ~6 Mthe ratio of tensile strength of the welded specimen
(Tw) to the tensile strength of the material (Tp). The
weld factor is defined for the weakest polymer, if two
8 v' E7 \: X; e# b/ rdifferent polymers are welded together.
Three variables are significant in welding a given
- k! y% Z. a* d5 y/ {8 U) T) ]modified PTFE part: welding temperature, pressure
and time. Optimal combinations of these three pa
# O1 D" V) ^# u- C( S6 Erameters must be found for successful welding of parts.
( h: T) i5 d, K/ j; K* F6 ZTemperature should be well above the melting point
(320–330°C), typically in the range of 360–380°C.
Little pressure is required to weld the parts after reaching
gel state. Less than 350 kPa, and often less than
7 m$ e' M8 S5 z" {35 kPa, pressure is required for welding. It is normally
not possible to trade higher welding pressure
) s. m9 A) W8 m) I( xfor lower temperature and vice versa. Time, the third
' p) L4 y9 d' F0 J, @variable of the process, is dependent on the size and
) y. R* U9 n3 v! cshape of the part. The actual weld time, defined as
time at the final temperature, is of the order of 1–2
minutes. It often takes a great deal longer to heat up
the part to the welding temperature. High heating rates
, e( [4 ?; q$ Zdo not accelerate the process due to the low thermal
. n/ ]- ?' r- l. _  |- Z  Q8 lconductivity of PTFE. Heat rates similar to those of
sintering cycles of preforms can be expected.
; K( E* c3 y4 t( NThe mating surfaces should be smooth and uniform
and free from any contamination. Unsintered
preforms and sintered parts of modified polytetrafluoroethylene
can be welded. Sintering and welding can
be combined. Parts can often be stacked up in the
6 `( K4 \7 ?$ bsintering oven without additional pressure. A weld
# A1 m3 ?4 o2 J" S3 bfactor of one can be routinely obtained in the combined
* j7 M) [. E7 j6 V# \process. A higher pressure is required for welding
sintered parts to counteract the residual stresses,
which tend to move the parts upon release. It is important
& Y( q3 C6 t: ~to cool the welded parts slowly to minimize
stresses stored in the part. Figure 16.6 illustrates a
# |2 ~8 r2 {; X+ J$ A0 Jdevice for hot-tool welding films and sheets.
( Z: M/ f7 Q$ pFigure 16.7 shows a comparison of the stressstrain
curves of a conventional and a modified PTFE
for the original and welded material. The weld line in
conventional PTFE when welded to itself, at best, fails
at very low strains. In the case of modified resin
4 x" U5 R5 j/ W" X# b8 Vwelded to itself, the weld factor attains value of 0.80–
4 a3 S' h) h1 l7 J' s/ p0.85. Weld factors for welding of conventional and
modified PTFE have been reported in the range of
6 k/ U! J# \$ \2 C0.66–0.87.[13]
* E1 e8 N$ L0 l8 P" XAnother method is welding with the help of a PFA
(melt processable) rod. In this case, the conventional
or modified PTFE is heated by hot air near the seam
3 Z( `5 p7 h7 Yuntil it is in gel state. The PFA rod is molten and used
to fill the seam.