Chemistry Reference
In-Depth Information
Comparison of normal and weldline bars
∗
.
Table 5.17.
Material
Specimen
Tensile
Elongation
Tensile
strength
modulus
PES
Normal
56.1 MPa
19.6%
2.65 GPa
Weldline
60.5 MPa
9.68%
2.61 GPa
PES/LCP polyesteramide
Normal
88.9 MPa
1.45%
7.45 GPa
Weldline
10.3 MPa
0.19%
6.07 GPa
Ardel
Normal
40.1 MPa
4.27%
1.87 GPa
Weldline
28.7 MPa
1.44%
2.19 GPa
Ardel/LCP polyester
Normal
73.1 MPa
2.72%
3.87 GPa
Weldline
18.6 MPa
0.61%
3.27 GPa
Ardel/LCP polyesteramide
Normal
76.2 MPa
1.69%
5.59 GPa
Weldline
32.3 MPa
1.25%
3.06 GPa
Lexan
Normal
58.9 MPa
97%
2.34 GPa
Weldline
45.2 MPa
36%
2.28 GPa
Lexan/LCP polyester
Normal
80.0 MPa
3.4%
3.89 GPa
Weldline
32.3 MPa
1.25%
2.92 GPa
Lexan/LCP polyesteramide
Normal
120 MPa
1.99%
8.07 GPa
Weldline
29.6 MPa
0.71%
4.38 GPa
∗
Source: Kiss, 1987.
There has been a great challenge in material design to fully utilize
the superior properties of liquid crystalline polymers while limiting the
inferior influence to the lowest possible extent. Significant progress has
been made in recent years. These include a better understanding of the
processing-structure-property relationship, the development of advanced
mixing techniques, and application studies. A recent review was given by
Isayev (1996). Some statements in this review are cited below. Rheologi-
cal studies have suggested that the most important parameter governing
the fibrillation is the viscosity ratio of thermoplastic to liquid crystalline
polymer. Most results indicate that the fibrillation is enhanced as the vis-
cosity ratio of liquid crystalline polymer to thermoplastic becomes less than
unity. The fibrillation is also affected by the type of deformation. The
prevailing opinion is that the elongational flow causes more extensive fib-
rillation than shear flow. Concentration of liquid crystalline polymer also
plays a significant role in fibrillation. There are many cases where liquid
crystalline polymer fibrils are found in blends at low concentrations. In
many others a strong fibrillation was observed at a high concentration of
liquid crystalline polymer. Apparently, the effect of the concentration on
fibrillation in blends depends on the nature of components. The fibrilla-
tion is also dependent on mixing techniques. The dual-extruder mixing
