Polybenzobisthiazoles – Critical issues in their performance and properties - Polyimides and Other High Temperature Polymers - page 235

Table 3.
Compressive properties of modified PBZT fibres

Modified PBZT fibres E t (GPa)

σ t (GPa) σ c (GPa)

Fluorine moiety in PBZT 240 2.1 0.32-0.55

Terphenyl PBZT 220 2.4 0.21-0.49

Methyl pendent PBZT 200 2.3 0.3-0.4

Hydroxy PBZT 180 2.1 0.14-0.41

Unmodified PBZT 325 4.1 0.21-0.46

Where E t = tensile modulus, σ t = tensile strength, σ c = compressive strength.

oxidized layer at the fibre surface that protected PBZT from degradation. There-
fore, it is possible to produce PBZT/metal composites using liquid aluminium al-
loy to improve compressive properties.
The compressive strength could also be enhanced using other techniques, e.g.,
(1) Introducing some H-bonding groups in the polymer chain.
(2) Introducing nano-metal or nano-ceramic materials in the fibre at the spinning
stage.
(3) Blending of PBZT fibre with high compressive strength fibres. Hydrogen
bonding groups are expected to enhance the intermolecular interaction and
contribute to increased compressive properties. Similarly nano-metal/nano-
ceramic particles in appropriate proportion should enhance compressive prop-
erties because these particles would be attached chemically to co-ordinating
groups. Blending of fibres is an established art in textile technology and fibres
such as graphite or alumina could be considered for this purpose.

5. SUMMARY

PBZT is the most thermally stable organic fibre synthesised to date and compares
well with PBZO in this respect. The tensile strength of these fibres is also of high
order and is higher than the tensile strength of carbon fibre. As for density it is
only slightly higher than Kevlar and is lower than all other reinforcing fibres.
PBZT has one disadvantage that its compressive properties are lowest among
all reinforcing fibres. Many efforts have been made in this regard such as varia-
tion in the backbone, introduction of cross-linking via radiation method, introduc-
tion of hydrogen bonding groups etc but all these methods have yielded insignifi-
cant improvements. It is, therefore, concluded that this area is open for active
research.