Water-swellable rubber with nanotechnology-enabled super capacity as smart water-leakage sealant

Author: Nazila Dehbari

Dehbari, Nazila, 2017 Water-swellable rubber with nanotechnology-enabled super capacity as smart water-leakage sealant, Flinders University, School of Computer Science, Engineering and Mathematics

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Water-swellable rubber (WSR) attracts special interest due to their unique properties that can

provide critical advantages for applications. They can stop water not only by means of elastic

sealing, high resilience and good tensile strength but also by means of swelling in water. These new

functional polymers can expand their volumes up to several hundred times the original by absorbing

surrounding water. The more water absorbed, the higher the expansion force. WSRs were used in

the Euro Tunnel under the straits of Dover and there are some examples in segment tunnel

construction for railways, subways and highways in Japan and recently in China.

The main problem of WSR is that hydrophilic super absorbent resin cannot disperse well in

hydrophobic rubber, so it can break off from rubber matrix easily which may cause weakening

abilities of water-swelling, mechanical properties, long-term water retention, and repeated usage.

These issues have spawned a flurry of research to devise longer lasting of superabsorbent polymers

(SAPs) in WSR, with higher water absorbency (about 3times) and particular emphasis on sealing


The incompatibility between rubber and SAPs can be mitigated by modifier. By using

compatibilizer and neutralizer the dispersion of hydrophilic phase into the hydrophobic continuous

phase is greatly improved confirmed by SEM, and therefore, migration of super water-absorbent

resin from the rubber matrix dramatically reduced.

Next step basically focused on enhancing mechanical properties of WSR by introducing either

hyperbranched (HB) polymer in poly acrylic acid (PAA) hydrogel or electrospun nanofibers.

Continuous nanofibers with dual nano-macro nature and ability to bridge scales are considered to

provide in situ water channels between SAPs and enhance the mechanical strength at the same time.

The objective of this thesis was to fabricating novel WSR, manufacture of nanofibers and study the

behaviour of nanofiber reinforced WSR composites. It was shown that PAA, styrene-butadiene

styrene (SBS), PAA/SBS and poly vinyl alcohol (PVA) nanofibers manufactured using single

and/or double needle electrospinning technique are excellent candidates for reinforcement purposes.

Based on results, WSR reinforced with PVA and SBS nanofibers possess significant improvements

in tensile strength, elongation at break and toughness of WSR composites. Chapter 1 provides a general introduction of WSR composites. The classification, background of study, problem statement, were discussed. The objectives and scopes of the study and significance of the research were also introduced in Chapter 1.

Chapter 2 provides an overview of previous research on knowledge sharing and intranets in this area. It introduces the framework for the case study that comprises the main focus of the research

described in this thesis. It is also the summary of the published work in a peer-reviewed journal. Chapter 3 focuses on the initial investigations of using SAP into the Rubber. Neutralisation and compatibilization effects on WSR is going to be discussed in this chapter. Chapter 4 provides a detailed introduction towards the electrospinning of various superabsorbent nanofibers mats. It presents an outlook about the problems and challenges in electrospun nanofiber

reinforced polymer composites. In next step, electrospun nanofiber mats were added into

conventional WSR and the properties of resultant composite alongside of mechanisms of those

fibers on WSR are also discussed. Chapter 5 discusses the potential use of nanofibers of PAA and SBS to reinforce WSR composites. The mechanisms and effects of these nanofiber mats in enhancing the mechanical and water

swelling properties of WSR are investigated here. Chapter 6 relates to the reinforcement of PAA hydrogel by using HB polymer. The physical and mechanical properties of the prepared hydrogels were investigated in this chapter.

Chapter 7 shows the possibility of significant enhancement of WSR in both swelling ability and mechanical strength by introducing PVA/SBS nanofiber. Chapter 8 summarizes the thesis, discusses its findings and contributions, points out limitations of the current work, and also outlines directions for future research.

Keywords: Water-swellable rubber, superabsorbent polymers, electrospinning, hyperbranched polymer, Mechanical Properties, composites

Subject: Engineering thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Computer Science, Engineering and Mathematics
Supervisor: Dr.Youhong Tang