Low resolution pulse nuclear magnetic resonance in the agro-food industry

Rutledge, Douglas

doi:10.1051/jcp/1992890273

Cited by 10 publications

(11 citation statements)

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“…A 90Њ pulse is the simplest the T 2 . 20, 21 In a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, a single 180Њ pulse is LRP-NMR experiment. The protons are excited by a second magnetic field B 1 produced by a radioreplaced by many equally spaced 180Њ pulses, and the summit of the spin echoes is measured.…”

Section: Methodsmentioning

confidence: 99%

Crosslinking of unsaturated polyester resins studied by low-resolution1H-NMR spectroscopy

Hietalahti

Root

Skrifvars

et al. 1997

J. Appl. Polym. Sci.

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ABSTRACT:The curing behavior of five unsaturated polyester resins with different molar ratios of styrene to the double bonds in the polyester chain (MR) was investigated. The gel time was measured according to a standard method by the Society of the Plastic Industry (SPI) and by low-resolution pulse nuclear magnetic resonance (LRP-NMR). The gel and curing times decreased and the maximum temperature of the reaction increased when the MR was decreased. The proton mobilities and populations were measured by LRP-NMR. Three components could be seen in the crosslinking reaction: styrene (very mobile, T 2 à 3 s), free polyester polymers (less mobile, T 2 à 150 ms), and cured resin (immobile, T 2 à 0.04 ms). The third component, cured resin, could be detected at the gel point. At this point, the proton mobilities of styrene and free polyester polymers were rapidly decreasing and the proton populations of the cured resin started to increase.

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Section: Methodsmentioning

confidence: 99%

Crosslinking of unsaturated polyester resins studied by low-resolution1H-NMR spectroscopy

Hietalahti

Root

Skrifvars

et al. 1997

J. Appl. Polym. Sci.

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“…The LFNMR approach is decribed by Rutledge (1992). In short, the spin-spin relaxation time (T 2 ) determined by LFNMR is a measure of how tight the water is bound: the more tight the bonding, the shorter the T 2 .…”

Section: Introductionmentioning

confidence: 99%

The states of water in Norway spruce (Picea abies (L.) Karst.) studied by low-field nuclear magnetic resonance (LFNMR) relaxometry: assignment of free-water populations based on quantitative wood anatomy

Fredriksson

Thygesen

2016

Holzforschung

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The states of water in Norway spruce (Picea abies (L.) Karst.) studied by low-field nuclear magnetic resonance (LFNMR) relaxometry: assignment of free-water populations based on quantitative wood anatomy DOI 10.1515/hf-2016-0044 Received February 23, 2016 accepted August 15, 2016; previously published online September 22, 2016 Abstract: Low-field nuclear magnetic resonance (LFNMR) relaxometry was applied to determine the spin-spin relaxation time (T 2 ) of water-saturated Norway spruce (Picea abies (L.) Karst.) specimens cut from mature sapwood (sW) and mature and juvenile heartwood (hW), where earlywood (EW) and latewood (LW) were separated. In combination with quantitative wood anatomy data focusing on the void volumes in various morphological regions, the NMR data served for a more reliable assignment of free-water populations found in water-saturated solid wood. Two free-water populations were identified within most sample types. One was assigned to water in the tracheid lumen and the other to water inside bordered pits. Whether water in the ray cell lumina was included in one or the other of these two populations depends on the curve-fit method applied (continuous or discrete). In addition, T 2 differences between the different tissue types were studied and, for comparison, sorption isotherms were measured by means of a sorption balance. There was a significant difference between EW and LW as well as between juvenile wood and mature wood in terms of T 2 related to the cell wall water. However, no differences were seen between the sorption isotherms, which indicates that the observed T 2 differences were not due to differences in cell wall moisture content (MC).

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“…To differentiate between different pools of water within the wood structure, low-field nuclear magnetic resonance (LFNMR) can be used [54][55][56][57][58][59][60][61][62][63][64] (for a theoretical background, see Rutledge [65]). Here, spin-spin relaxation time (T 2 ) distributions are evaluated from exponential decay functions.…”

Section: Location and State Of Watermentioning

confidence: 99%

On Wood–Water Interactions in the Over-Hygroscopic Moisture Range—Mechanisms, Methods, and Influence of Wood Modification

Fredriksson

2019

Forests

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Wood is a hygroscopic material that absorbs and desorbs water to equilibrate to the ambient climate. Within material science, the moisture range from 0 to about 95–98% relative humidity is generally called the hygroscopic moisture range, while the exceeding moisture range is called the over-hygroscopic moisture range. For wood, the dominating mechanisms of moisture sorption are different in these two moisture ranges; in the hygroscopic range, water is primarily bound by hydrogen bonding in cell walls, and, in the over-hygroscopic range, water uptake mainly occurs via capillary condensation outside cell walls in macro voids such as cell lumina and pit chambers. Since large volumes of water can be taken up here, the moisture content in the over-hygroscopic range increases extensively in a very narrow relative humidity range. The over-hygroscopic range is particularly relevant for durability applications since fungal degradation occurs primarily in this moisture range. This review describes the mechanisms behind moisture sorption in the over-hygroscopic moisture range, methods that can be used to study the interactions between wood and water at these high humidity levels, and the current state of knowledge on interactions between modified wood and water. A lack of studies on interactions between modified wood and water in the over-hygroscopic range was identified, and the possibility of combining different methods to acquire information on amount, state, and location of water in modified wood at several well-defined high moisture states was pointed out. Since water potential is an important parameter for fungal growth, such studies could possibly give important clues concerning the mechanisms behind the increased resistance to degradation obtained by wood modification.

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Low resolution pulse nuclear magnetic resonance in the agro-food industry

Cited by 10 publications

References 0 publications

Crosslinking of unsaturated polyester resins studied by low-resolution1H-NMR spectroscopy

Crosslinking of unsaturated polyester resins studied by low-resolution1H-NMR spectroscopy

The states of water in Norway spruce (Picea abies (L.) Karst.) studied by low-field nuclear magnetic resonance (LFNMR) relaxometry: assignment of free-water populations based on quantitative wood anatomy

On Wood–Water Interactions in the Over-Hygroscopic Moisture Range—Mechanisms, Methods, and Influence of Wood Modification

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