Title page for ETD etd-7497-232759

Type of Document Master's Thesis
Author Gray, Robert Williamson IV
Author's Email Address rogray@vt.edu
URN etd-7497-232759
Title The Effects of Processing Conditions on Thermoplastic Prototypes Reinforced with Thermotropic Liquid Crystalline Polymers
Degree Master of Science
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Bohn, Jan Helge
Davis, Richey M.
Baird, Donald G. Committee Chair
  • Polymer
  • Composite
  • TLCP
  • Prototype
  • FDM
Date of Defense 1997-07-30
Availability restricted
This work is concerned with preliminary studies on

developing thermoplastic composite materials suitable for

use in fused deposition modeling (FDM). Polypropylene (PP)

strands reinforced with continuous thermotropic liquid

crystalline polymer (TLCP) fibrils were generated in a

novel dual extruder process. Strands were then re-extruded

to form short fiber composite monofilaments that were used

as feed stock in the FDM 1600 rapid prototyping system.

Prototypes containing 40 wt% Vectra A were shown to have

tensile properties twice those of parts built using

acrylonitrile butadiene styrene copolymer (ABS), a

commercially available material used in the FDM 1600 rapid

prototyping system. It was also shown that the final

mechanical properties of a composite prototype can be

tailored to a specific application by adjusting the

lay-down pattern, increasing the functionality of the

prototype. In order to obtain the maximum tensile

properties in these composite prototype, additional

studies were performed to determine the effects of thermal

and deformation histories on the mechanical properties of

monofilaments that were re-extruded from long fiber TLCP

reinforced strands. Strands were consolidated uniaxially

at temperatures just above the melting point of the matrix

in order to determine the effects of thermal history, and

an approximate 20% reduction in tensile modulus relative

to the modulus of the strands was observed. Monofilaments

that could be used as feed stock in FDM were extruded from

long fiber TLCP reinforced strands using a capillary

rheometer in order to study the effects of capillary

diameter, capillary L/D, and apparent shear rate on the

tensile properties.

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