Mechanical degradation of filter polymer materials:
Polyphenylene sulfide
Winyu Tanthapanichakoon
*
, Mitsuhiko Hata, Koh-hei Nitta, Masami Furuuchi, Yoshio Otani
Faculty of Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan
Received 5 April 2006; received in revised form 11 May 2006; accepted 17 May 2006
Available online 11 July 2006
Abstract
Polyphenylene sulfide (PPS) is known as a material resistant to high temperature and chemicals; however, there are arguments on the dura-
bility of PPS non-woven fabrics to chemicals, such as nitric acid (HNO
3
), sulfuric acid (H
2
SO
4
), and hydrochloric acid (HCl). Therefore, this
work aims at investigating the degradation of PPS non-woven fabrics in HNO
3
,H
2
SO
4
and HCl, and at confirming acid durability of PPS non-
woven fabrics. In addition, this paper also studies the interaction among these three acids by measuring the retention of strength in binary or
tertiary mixtures of these three acids. A discussion has been made on the acceleration/retardation of PPS degradation by the interactive effects,
and also on the chemistry related to the degradation by these acids. Furthermore, there is a linear relationship between the nitric acid concen-
tration and the proportion of carbon in the remaining PPS structures after 100 h of acid exposure. Also, this proportion of carbon is a good
indicator of the retained strength in PPS fabrics.
Ó 2006 Published by Elsevier Ltd.
Keywords: Polyphenylene sulfide; PPS; Fabric; Degradation; Chemistry; Interaction
1. Introduction and objectives
Polyphenylene sulfide (PPS) is often regarded to be durable
at high temperature (160e240
C) and resistant against several
chemicals. According to Vives et al. [6], the PPS non-fabric
material with no filler or reinforcement could retain 96, 100
and 100% of its original tensile strength after 24 h exposure
to, respectively, 10% nitric acid (HNO
3
), 37% hydrochloric
acid (HCl) and 30% sulfuric acid (H
2
SO
4
)at93
C.
In general, fabrics react in a different manner from non-
fabric materials. According to a PPS commercial brochure,
PPS fabrics, for the exposure time of 24 h at 93
C, decreases
its tensile strength of down to 72, 91 and 94% in 37% HCl,
10% HNO
3
and 30% H
2
SO
4
, respectively. These data are
very much different from the previous data reported for film
or sheet materials, and this might be related to the structural
difference of films and fabrics.
There is a big argument whether PPS non-woven fabrics, of-
ten used as bag filter materials in incinerating plants, would still
be durable toward acid liquids. These bag filters are exposed to
acidic gases such as hydrochloride, SO
x
(SO
2
and SO
3
) and NO
x
(NO and NO
2
), which could form a solution of HNO
3
, HCl and
H
2
SO
4
when the operational temperature is under the acid dew
point. These acid solutions in condensed droplets could stay
long enough to severely degrade the PPS fabric. Durability of
PPS non-woven fabrics against these acids is therefore signifi-
cant to such industries as coal-fired power plant.
Although longer exposure time to acids reduces the fabric
strength as shown in Table 1, the effect of acid concentration
is not fully understood yet. Only for 37% HCl, 10% HNO
3
and
30% H
2
SO
4
the data have been reported. Even if Table 1 and
the results from Vives et al. [6] might imply that HNO
3
is the
most degrading, followed by HCl and H
2
SO
4
from the view-
point of retention of strength with respect to the exposure
time, this needs to be verified. This is because the acid
* Corresponding author. Tel.: þ81 76 234 4813; fax: þ81 76 264 6239/þ662
254 4189.
E-mail addresses: twinyu_a@yahoo.ca, twinyu@hotmail.com
(W. Tanthapanichakoon).
0141-3910/$ - see front matter Ó 2006 Published by Elsevier Ltd.
doi:10.1016/j.polymdegradstab.2006.05.005
Polymer Degradation and Stability 91 (2006) 2614e2621
www.elsevier.com/locate/polydegstab