ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The microstructure and fracture behavior of Injection molded samples of unfilled and filled grades of liquid crystalline polymers (Vectra® and Ultrax®) containing cold and warm knit lines have been studied by scanning electron microscopy, X-ray scattering, and Instron tensile tests. Four process parameters - melt temperature, mold temperature, injection time, and holding pressure - have been varied in accordance with a 24 factorial design experiment. In cold knit lines a 200 µm thick region with transverse orientation with Hermans orientation function f ≈ 0.12-0.18 is formed on both sides on the weld area. The strength of the cold knit lines is very low, 9.0-19.8 MPa corresponding to 15-20% of the full strength of the material. The strength of the warm knit lines increases markedly with increasing distance from the insert and is generally significantly greater (40-45 MPa, 48 mm from the insert) than in the cold welds. Annealing at 260-300°C of samples containing cold knit lines causes first a partial healing of the knit line and later extensive chemical degradation of the polymer.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760302411
Permalink
