Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

Jung, A; Endres, Manuel; Weichold, Oliver

doi:10.3390/polym12102185

Cited by 8 publications

(4 citation statements)

References 48 publications

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“…Such a significant increase in the degree of swelling at low crosslinking densities has already been observed for other crosslinked hydrogel systems [ 25 ]. These values are comparable to common acrylate superabsorbent polymers [ 26 , 27 ], and are another indication of the homogeneous nature of these gels. In contrast, the coherent gel with the lowest concentration of BIS could only absorb 116 g/g.…”

Section: Resultssupporting

confidence: 77%

Multivalent Allylammonium-Based Cross-Linkers for the Synthesis of Homogeneous, Highly Swelling Diallyldimethylammonium Chloride Hydrogels

Mrohs

Weichold

2022

Gels

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N,N’-methylenebisacrylamide (BIS) is a very popular cross-linker for the radical polymerisation in water. It is highly reactive but prone to alkaline hydrolysis and suffers from a low solubility. This study shows that with slow polymerising systems such as N,N-diallyldimethylammonium chloride, only inhomogeneous networks are formed. As a consequence, gels with very low cross-linking densities, i.e., high swelling capacities, disintegrate during the swelling test and firm, coherent gels are not accessible due to the solubility limit. A promising alternative are multivalent tetraallyl-based compounds, of which tetraallylammonium bromide (TAAB), N,N,N’,N’-tetraallylpiperazinium dibromide (TAPB) and N,N,N’,N’-tetraallyltrimethylene dipiperidine dibromide (TAMPB) are the subject of this study. With these, the cross-linking polymerisation appears to be statistical, as gels formed at low monomer conversion have essentially the same swelling properties as those formed at high conversions. This is not observed with BIS. However, gelation with the tetraallyl cross-linkers is much slower than with BIS and follows the order TAPB < TAMPB < TAAB, but the differences become significantly smaller with increasing content. At low contents, all three allow the preparation of gels with high swelling capacities of up to 360 g/g.

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Section: Resultssupporting

confidence: 77%

Multivalent Allylammonium-Based Cross-Linkers for the Synthesis of Homogeneous, Highly Swelling Diallyldimethylammonium Chloride Hydrogels

Mrohs

Weichold

2022

Gels

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“…Three trends can be observed from Figure 4 : (i) as expected, the degree of swelling decreases for all gels with increasing crosslinker content, (ii) this seems to be less pronounced for TAAB ( 1a ) than for TAMPB ( 1c ), as the ratio of the degrees of swelling increases from 4.6 at 2% to 10 at 10% and to 13.1 at 50%, and (iii) TAAB ( 1a ) consistently results in by far the highest degrees of swelling, with a measurable value of up to 397 g/g at a content of 2%. These values are comparable to common acrylate superabsorbent polymers [ 15 , 16 ]. BIS, on the other hand, is not only limited by the solubility but also by a seemingly much stronger decrease in the degree of swelling.…”

Section: Resultssupporting

confidence: 73%

Hydrolytic Stability of Crosslinked, Highly Alkaline Diallyldimethylammonium Hydroxide Hydrogels

Mrohs

Weichold

2022

Gels

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The aim of this study was to evaluate the persistence of alkaline hydrogels based on a common (N,N′-methylenebisacrylamide, BIS) and three recently published tetraallyl crosslinkers. Such hydrogels have been shown to be suitable materials for the rehabilitation of cementitious materials. Of the four crosslinkers under investigation, N,N,N′,N′-tetraallylpiperazinium dibromide decomposed quickly in 1 m KOH solution and was not considered further. BIS showed the first signs of a decomposition after several days, while tetraallylammonium bromide and N,N,N′,N′-tetraallyltrimethylene dipiperidine dibromide remained unaffected. In contrast to BIS, which suffers from low solubility in water, the two tetraallyl crosslinkers show unlimited miscibility with diallyldimethylammonium hydroxide solutions. For the study, gels with up to 50 wt % crosslinker were prepared. Of these, gels containing tetraallylammonium bromide always show the highest degrees of swelling, with a peak value of 397 g/g at a content of 2 wt %. Under accelerated ageing at 60 °C for 28 d, gels crosslinked with BIS ultimately turned liquid, while the storage modulus and the degree of swelling of the two tetraallyl-crosslinked gels remained unchanged. This indicates that alkaline gels can be suitable for long application periods, which are common for rehabilitation measures in the construction industry.

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“…The amount of used cross-linker at the SAP production seems to be an important factor affecting the swelling capability of used SAPs and thus void formation in a material matrix, as was reported for cement composites by Jung et al [ 39 ]. The swelling reduction of SAPs used in lime-based plasters analyzed in this paper was caused most likely by the physical restriction of the formed polymer chains due to the presence of physical cross-links and changes in the ion concentration.…”

Section: Resultsmentioning

confidence: 83%

Effects of Secondary Porosity on Microstructure and Mechanical Properties of SAP-Containing Lime-Based Plasters

et al. 2022

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Despite the many benefits associated with the utilization of superabsorbent polymers (SAPs), several drawbacks have been reported. In particular, the effect of SAPs on microstructure, together with its consequences for mechanical properties, is not fully understood yet for some composite materials. This study analyzes the role of SAPs in the formation of the microstructure of lime composites, taking into account their chemical composition. The obtained experimental results show that the particle size and cross-linking density of used SAPs are crucial parameters affecting both the microstructure and mechanical performance of the analyzed composites. Coarser SAPs with low cross-linking density in the dosage of 0.5 and 1 wt.% are found as the most suitable solution, leading even to a slight improvement of mechanical parameters. The secondary porosity formed by swelled hydrogels is identified as a very significant factor since hydrogel-filled voids do not contribute to the strength parameters. The formation of the affected zone around SAP cores depends on the chemical composition of SAPs considerably as the higher cross-linking density influences the desorption rate. Based on achieved results, utilization of SAPs in building materials should be studied at a more detailed level with particular importance on the definition of SAP-related voids and affected zone around SAP particles.

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Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

Cited by 8 publications

References 48 publications

Multivalent Allylammonium-Based Cross-Linkers for the Synthesis of Homogeneous, Highly Swelling Diallyldimethylammonium Chloride Hydrogels

Multivalent Allylammonium-Based Cross-Linkers for the Synthesis of Homogeneous, Highly Swelling Diallyldimethylammonium Chloride Hydrogels

Hydrolytic Stability of Crosslinked, Highly Alkaline Diallyldimethylammonium Hydroxide Hydrogels

Effects of Secondary Porosity on Microstructure and Mechanical Properties of SAP-Containing Lime-Based Plasters

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