Figure
4. DTA patterns of PPS-based bag filter materials with different loading
units.
As a key indicator for the semi-crystalline of PPS, the melting point
(Tm) could reflect intuitively its crystalline
characteristics[27]. DTA patterns of pure PPS and fifteen samples
collecting from factories were conducted by a thermal analyzer system
and summarized in Fig. 4. It can be observed that Tmreduces progressively and the width of peak of melting point becomes
broaden with increase of content of SO2 for all
categories regardless of loading unit
(below
200 MW, 200-300MW and above 300 MW). Generally, crystal is an ordered
arrangement of molecular chains, while the melting destroys the assembly
structure of molecules wholly to form the disordered molecular
chain[27, 35]. Higher crystallinity of polymer is, more regular of
arrangement of molecular chains is, and higher temperature to destroy
its assembly structure needs, and thus higher the melting point gets for
the same material. The appearance of new functional groups including
-SO-, -SO2- and -SO3H in the molecular
chain of PPS would break its structural regularity along with the
decreasing of crystallinity, and reduction of melting point of fifteen
samples can be explained. Besides, the lower of melting point is, the
more serious damage of crystal is, and thus the lower of crystallinity
is for the same material. Therefore, the crystallinity of PPS gradually
declines with the addition of content of SO2 from 1# to
5#, 6# to 10# and 11#-15#, which is in good agreement with those
obtained from the SEM and FTIR analysis.
3.3 Mechanical properties of
PPS-based
bag filter materials
As a crucial index to evaluate superiority or inferiority of mechanical
properties of PPS-based bag filter materials during the running of the
filter bag, CD strengths of all samples were introduced and shown in
Fig. 5.