try these:
http://www.solvayadvancedpolymers.com/static/wma/pdf/1/3/5/g430.pdf
http://www.solvayadvancedpolymers.com/static/wma/pdf/1/3/4/G930.pdf
http://www.solvayadvancedpolymers.com/static/wma/pdf/1/3/7/M345.pdf
or this enthusiastic poem from Leo:
Hello Ingemar,
I do not know the actual viscosity of typical LCP materials. Typical
LCP systems have a very small temperature range where the materials exhibit
the softening behavior from a rigid material to a high viscosity taffy-like
material (thermoplastic range) that will be injection moldable under high
pressure. Above this short temperature range (perhaps only 5-10 degrees
Celsius), the LCP shows a very rapid drop in viscosity, much like the
melting of a crystalline material like a metal. The temperature at which
this occurs is commonly above 300C, and may be above 400C for some special
materials. In this liquid, highly fluid, low viscosity state the LCP
molecules remain highly aligned and the viscosity is very low, almost like
water. The LCPs commonly exhibit shear-thinning, so with high pressure and
flow through narrow gaps, the local viscosity of material in the narrow gap
regions will drop even further. This molecular alignment with flow
direction results in typical LCP systems being highly anisotropic. The CTE
in the flow direction is much lower than the CTE transverse to the flow
direction because there is very little molecular bonding transverse to the
flow direction. So the modulus is also lower when measured perpendicular to
the flow direction. Due to the highly ordered LCP structure and presence of
almost no secondary amorphous phase, the LCP shows very low free volume
reduction or shrinkage when cooled. So the dimensions of the molded unit are
much more dependent upon the accuracy of the mold than with just about any
other thermoplastic. The very low viscosity allows very fine features to be
moldable with LCP, so if you have a 5 micrometer wide and deep scratch in
the surface of the mold, you will see a 5 micrometer wide and high raised
ridge on the surface of the molded unit when removed from the mold. Typical
thermoplastics (e.g. nylon) have a degree of "crystallinity" at the use
environment temperature, but are highly amorphous and viscous at the molding
temperature, although some degree of molecular alignment with flow direction
will occur. These materials typically requires use of fairly high mold
pressure. Since the LCP requires such high temperature injection molding,
the molds are generally heated with hot oil, not the hot water possible with
lower temp thermoplastic molding. Since the molds are typically held at a
much lower temperature than the temperature in the mold screw injection
region (typically 300 to 400C), the LCP is rapidly injected into the mold
because the temperature range from very fluid (say at 360C) to solid may
only be 5 or 10C as mentioned above. this rapid solidification allow short
cycle times between mold shoots. Due to the anisotropy of the LCP during
molding and at room temp, the mold must be carefully designed relative to
location of injection point and mold cavity venting. LCPs are very
interesting materials, and they show the lowest permeability of virtually
any commercial polymers, offering the opportunity to form quasi-hermetic
structures, assuming the premolded package is well sealed.
This may be more info than you wanted, but it came out stream of
consciousness....
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
hope not too commercial...
regards
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]
Sent: den 3 februari 2005 23:16
To: [log in to unmask]
Subject: [TN] LCP Text
Can anyone recommend a good basic text on liquid crystal polymers? Not too
academic.
Doug Pauls
Rockwell Collins
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