请问有谁能说说铁佛龙是怎样焊接的??

sqqd.12 · 发表于 2007-10-19 15:29:02

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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 · 发表于 2007-10-19 20:56:17

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 · 发表于 2007-11-16 18:40:38

? 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 · 发表于 2007-11-16 20:09:05

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
normally suitable for applications where the fluoropolymer
does not carry large loads such as those
experienced by chemical processing equipment.
Welding or adhesiveless joining is a method by which
parts for load-bearing applications are manufactured.
The load could consist of temperature, chemical corrosion,
and force. This method also known as welding
or joining allows economical fabrication of complex
parts by joining individual components.
It is possible to obtain a good bond between fluoropolymers
themselves, without the use of adhesives,
by application of heat and pressure. Pressure can help
drive 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
the substrate. Examples of parts made by this technology
include glass cloth-backed polytetrafluoroethylene
sheet, or multi-ply circuit board and coated
aluminum or copper sheet. Achieving this type of
bonding is more complex with polytetrafluoroethylene
than melt processible polymers. PTFE does not flow
after melting due to its extremely high viscosity.
It is possible to achieve adhesiveless bonding using
standard PTFE in special applications where the
polymer 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
are smooth, or the objects being bonded are too large.
In such cases, a different type of polytetrafluoroethylene
is required.
Polytetrafluoroethylene for these applications is
known as “modified” which refers to the presence of
a small amount of a second perfluorinated monomer,
known as a modifier, in its structure. The modifier
molecule 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.
How does it work? A simple explanation is offered
here, based on the author’s own experience. The
modification reduces the molecular weight of the polymer,
which in turn reduces its melt viscosity. Lower
melt viscosity increases the mobility of the polytetrafluoroethylene
chains. This facilitates diffusion and
entanglement of polymer chains at the bonding interface.
The pendent group of the modifier disrupts the
crystals of PTFE, thus preventing excessive crystallization.
Crystallinity which is too high results in poor
mechanical properties such as poor tensile and flex
properties. An optimally modified PTFE has good
mechanical properties in addition to weldability.
Welding can be achieved using PTFE made by
dispersion or suspension polymerization. Most applications
involve welding of parts made from granular
resins (suspension polymer). Dispersion polymerized
PTFE is also used for application such as wire
coating. 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
to its good interlayer adhesion, around the conductor
at the completion of sintering cycle.
16.4.1 Welding Technique
Quality 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
that the weld line would fall near its center (Fig. 16.5).
Tensile strength and elongation can be determined by
extensiometry. Weld factor is defined by Eq. 16.1 as
the 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
different polymers are welded together.
Three variables are significant in welding a given
modified PTFE part: welding temperature, pressure
and time. Optimal combinations of these three pa
rameters must be found for successful welding of parts.
Temperature 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
35 kPa, pressure is required for welding. It is normally
not possible to trade higher welding pressure
for lower temperature and vice versa. Time, the third
variable of the process, is dependent on the size and
shape 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
do not accelerate the process due to the low thermal
conductivity of PTFE. Heat rates similar to those of
sintering cycles of preforms can be expected.
The 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
sintering oven without additional pressure. A weld
factor of one can be routinely obtained in the combined
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
to cool the welded parts slowly to minimize
stresses stored in the part. Figure 16.6 illustrates a
device for hot-tool welding films and sheets.
Figure 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
welded to itself, the weld factor attains value of 0.80–
0.85. Weld factors for welding of conventional and
modified PTFE have been reported in the range of
0.66–0.87.[13]
Another 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
until it is in gel state. The PFA rod is molten and used
to fill the seam.

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[已解决] 请问有谁能说说铁佛龙是怎样焊接的??

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