Characterization of polyethylene of raised temperature resistance (PE-RT) materials - a mini review and insights

Schneider N, Kaschta J, Heiduk I, Schubert DW (2023)

Publication Language: English

Publication Type: Conference contribution, Abstract of a poster

Publication year: 2023

Event location: Kopenhagen DK

Abstract

Since the development of the first pipe sys-
tems over 5500 years ago, various materials in-
cluding terracotta, metals and polymers, were
used in this field of application. High-density
polyethylens (HDPE) display good processabil-
ity and chemical resistance at low costs since
their first pipe application in 1954 [1, 2].
Polyethylenes in long-term high temperature
implementations tend to failure mechanisms
such as slowcrack-growth (SCG) and
environmental-stress-cracking (ESC). In both
failure mechanisms, long-term stresses lead
to the formation of so-called craze-structures,
where crystals rotate in stress direction with
an alternating pattern of crystalline and amor-
phous segments (fibrills) between accruing
voids, promoted by raised temperatures. The
cohesion of crystallites within the craze is main-
ly assured by tiemolecules, amorphous chains
that are incorporated in several crystallites,
forming intercrystalline bridges [3]. Therefore,
creep resistant materials such as cross-linked
polyethylene (PE-X) and polyethylene of raised
temperature resistance (PE-RT) were invented
to impede the failure in the amorphous regions.
In the case of PE-RTs, the macromolecules in
the high molecular mass fractions are short-
chain branched by multistep polymerisation
with α-olefins. Consequently, their crystalli-
zation is hindered. The crystalline matrix is
formed by the almost linear low molar mass
fractions, whereas the highbranched high
molecular mass fractions are incorporated in
multiple crystals and so form tie-molecules.
This work reviews several methods to char-
acterize those polyethylenes with respect to
their comonomer distribution and tie mole-
cule density. Due to the necessity to locate
the comonomer solely on the long chains,
polymers will be separated by means of their
molar mass by chemical precipitation frac-
tionation or by successive self-nucleation and
annealing treatment (SSA). The precipitates
molar mass distributions are subsequently
analysed by high temperature gel permeation
chromatography (HT-GPC) measurements.
The comonomer content and is determined by
Fourier-transform infrared spectroscopy (FTIR),
whereas the SSA spectrum provides informa-
tion about the intra-fractional distribution of
the comonomer. The long-term performance
of such materials can be estimated by the
measurement of their strain hardening modu-
lus (SH-Modulus) at elevated temperature [4]

Authors with CRIS profile

Nicolai Schneider Lehrstuhl für Werkstoffwissenschaften (Polymerwerkstoffe) Joachim Kaschta Lehrstuhl für Werkstoffwissenschaften (Polymerwerkstoffe) Dirk Schubert Lehrstuhl für Werkstoffwissenschaften (Polymerwerkstoffe)

Involved external institutions

Fränkische Rohrwerke Gebr. Kirchner GmbH & Co. KG DE Germany (DE)

How to cite

APA:

Schneider, N., Kaschta, J., Heiduk, I., & Schubert, D.W. (2023, May). Characterization of polyethylene of raised temperature resistance (PE-RT) materials - a mini review and insights. Poster presentation at Nordic Polymer Days 2023, Kopenhagen, DK.

MLA:

Schneider, Nicolai, et al. "Characterization of polyethylene of raised temperature resistance (PE-RT) materials - a mini review and insights." Presented at Nordic Polymer Days 2023, Kopenhagen 2023.

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