Longer Curing Time Research Articles

Optimization of the replica molding process of PDMS using pennate diatoms

Biomimetic fabrication of nanostructured materials has recently attracted the attention of researchers as a cost-effective and easily applicable method of nanotexturing. Different techniques and materials have been used in order to replicate natural patterns, among which polydimethylsiloxane (PDMS Sylgard 184®) was recently used to replicate the micro- and nanoscale patterns from centric diatoms. In this paper, we test the reproducibility and precision of this approach using various morphologically different diatom species trying to optimize the molding parameters. The optimization process is focused on immobilization of diatoms on the glass support, which serves as a master for templating, as well as on the parameters of PDMS fabrication such as the ratio of the curing agent and elastomer, use of vacuum, curing time and temperature. The results indicate that higher ratios of curing agent and elastomer, longer curing time and lower temperature are the most favorable conditions to obtain negative diatom replicas of good quality with features of 50 nm. Although this method can give very precise results producing high-resolution molds with all micro- and nanostructures replicated, we revealed some limitations regarding the size and morphology of the species used. These results indicate that large round and flat diatom species seem to be more suitable for the cast molding.

Laboratory Evaluation of Warm Mix Asphalt Influence on Theoretical Maximum Specific Gravity

Abstract Warm mix asphalt (WMA) technology provides sufficient workability for asphalt mixtures at reduced mixing and compaction temperatures. Depending on the WMA technology, the typical temperature reduction range is 20 °C to 55 °C below hot mix asphalt (HMA) production temperatures. WMA involves chemical and wax additives that are added to an asphalt binder or incorporated through the use of foaming technology. The main advantages of WMA are reduced emissions and a reduction in combustible fuel consumption. Ongoing WMA research projects have documented some differences between HMA and WMA mixes, prompting numerous research projects that are investigating these concerns. The purpose of this research is to evaluate the volumetric properties by directly comparing laboratory produced WMA and HMA mixes. This study investigates the impact of WMA additives on the volumetric properties, specifically, the theoretical maximum specific gravity (Gmm). The Gmm testing followed the procedure of ASTM D2041. Two mix designs with HMA binder were produced, one without recycled asphalt pavement (RAP) and the other with 30 % RAP. After the mix designs were completed, no additional changes were made to account for the addition of the WMA technology. The mixes included the WMA technologies Sasobit and Advera, as well as an HMA control, for a total of six different laboratory produced mixes. Each mix was produced at 120 °C, 135 °C, and 150 °C, and each mix was oven cured for 1, 2, and 4 h. The test results were analyzed using statistical principles to determine whether differences in the Gmm values were statistically significant. The results show that temperature has little impact on Gmm. Gmm was not affected by curing times of 1 and 2 h, but the longer curing time of 4 h resulted in a statistically significant increase in Gmm. Further analysis revealed that the mix sensitivity to curing time depends on the amount of RAP in the mix. For the mix designs studied, the Advera Gmm values were similar to the HMA values, but the Sasobit Gmm values were statistically lower than the Advera values.

The Physical And Thermal Properties Of Modified Rotational Molding Grade Silane Cross–Linked Polyethylene Compound

Uji kaji ini dijalankan untuk mengkaji sifat fizikal dan terma bagi formulasi campuran polietilina berangkai silang gred acuan putaran berasaskan kebolehprosesan. High Density Polyethylene (HDPE) gred acuan putaran dicampur dengan pelbagai komposisi HDPE dan Low Density Polyethylene (LDPE) menggunakan penyemperit skru pendua. Indeks Aliran Lebur (MI) campuran dikaji berasaskan ASTM D 1238. Komposisi campuran tersebut disambung silang secara kimia dengan agen penyambung silang silane menggunakan 'two roll mill’. Kemudian sambung silang lembapan dilakukan di dalam water bath selama 4 jam dan 8 jam. Kandungan gel diukur mengikut ASTM D 2765 bagi menentukan darjah penyambungan silang. Bagi analisis terma,hanya sampel yang disambung silang dengan 2.0 phr agen penyambung silang silane dikaji dengan Kalorimetri Pengimbasan Pembeza (DSC) berdasarkan ASTM 3417. Ujian kestabilan terma bagi XLPE silane dilakukan dengan menggunakan Penganalisa Termogravimetri (TGA) mengikut ASTM D 3850. Keputusan bagi Indeks Aliran Lebur (MI) menunjukkan campuran antara HDPE gred acuan putaran dengan HDPE lebih tinggi berbanding LDPE, dengan itu menambahbaik kebolehprosesan bahan. Ketumpatan campuran antara HDPE gred acuan putaran HDPE meningkat sedikit manakala campuran dengan LDPE menurun sedikit. Sampel yang dicampur dengan HDPE tidak menunjukkan perubahan bagi suhu lebur, Tm manakala darjah penghabluran, Xc, mengalami penurunan. Sampel campuran dengan LDPE pula, Tm dan Xc menurun dengan bertambahnya komposisi LDPE menunjuk kepada kebolehprosesan yang lebih baik. Kandungan gel meningkat dengan penambahan kepekatan silane dan tidak bergantung kepada komposisi campuran. Masa pengawetan yang lebih panjang menghasilkan nilai gel yang tinggi. Kestabilan terma PE yang dirangkai silang lebih tinggi berbanding HDPE yang tidak dirangkai silang. Oleh yang demikian, penyambungan silang secara silane menambahkan kestabilan campuran. Kata kunci: HDPE rangkai silang silane, acuan putaran, sifat fizikal, sifat terma dan kebolehprosesan This study is aimed at investigating the physical and thermal properties of the modified rotational molding grade cross-linked polyethylene compound with respect to process ability. Rotational molding grade High Density Polyethylene (HDPE) was blended at various compositions with HDPE and Low Density Polyethylene (LDPE) using twin screw extruder. The melt index of the blends was studied according to ASTM D 1238. The blended compositions were chemically cross-linked with various amount of silane cross-linking agent using two roll-mill. Water curing was then undertaken at 100C in water bath for 4 and 8 hours. Gel content was measured according to ASTM D 2765 to determine the degree of cross-linking. For thermal analysis, only samples crosslinked with 2.0 phr silane cross-linking agent were investigated on the Differential Scanning Calorimetry (DSC) according to ASTM D 3417. The thermal stability test of the silane Crosslinkable Polyethylene (XLPE) was performed by Thermogravimetric Analyzer (TGA) according to ASTM D 3850. Results on melt index (MI) indicated that the rotational molding grade HDPE blended with HDPE showed higher MI compared to that with LDPE thus improved process ability. The density of rotational molding grade HDPE with HDPE was slightly increased whereas that blended with LDPE was slightly decreased. Samples blended with HDPE, melting temperature, Tm, barely changed and degree of crystallinity, Xc, decreased with compositions. Samples with LDPE Tm and Xc decreased with compositions thus improved process ability. As the silane concentrations increased, the gel content after curing was also increased but independent of compositions. Longer curing time resulted in higher gel content. Thermal stability of the crosslinked HDPE was higher than the uncross-linked HDPE, thus silane cross-linking help to stabilize the blends. Key words: Silane cross–linked high density polyethylene, rotational molding, thermal properties, physical properties and process ability

Effects of Curing Time on Properties of Spin-On Glass as Low-Temperature Insulator

ABSTRACTIn this work, we report the effects of curing time on properties of SiO2 films produced from Spin-On Glass (SOG) diluted with H2O and cured at 200°C. The electrical characterization showed that the insulator breakdown field for the films produced from SOG diluted with H2O with 1 Hr of curing time was approximately 5 MV/cm while for 6.5 Hrs of curing time the breakdown field was 21 MV/cm. Also, the refractive index and surface roughness were improved with longer curing time.

Effect of Curing Conditions on Strength of Fly ash-based Self-Compacting Geopolymer Concrete

This paper reports the results of an experimental work conducted to investigate the effect of curing conditions on the compressive strength of self-compacting geopolymer concrete prepared by using fly ash as base material and combination of sodium hydroxide and sodium silicate as alkaline activator. The experiments were conducted by varying the curing time and curing temperature in the range of 24-96 hours and 60-90°C respectively. The essential workability properties of freshly prepared Self-compacting Geopolymer concrete such as filling ability, passing ability and segregation resistance were evaluated by using Slump flow, V-funnel, L-box and J-ring test methods. The fundamental requirements of high flowability and resistance to segregation as specified by guidelines on Self-compacting Concrete by EFNARC were satisfied. Test results indicate that longer curing time and curing the concrete specimens at higher temperatures result in higher compressive strength. There was increase in compressive strength with the increase in curing time; however increase in compressive strength after 48 hours was not significant. Concrete specimens cured at 70°C produced the highest compressive strength as compared to specimens cured at 60°C, 80°C and 90°C.

Use of Rice Husk Ash as an Admixture to Remove Chromium from a Tannery Waste

This laboratory-scale study explored the use of rice husk ash (RHA) as an admixture to stabilize and solidify the waste sludge from a chrome-tanning process. Various ratios of RHA and tannery sludge were used, ranging from 0.25 to 1.0 by weight of the cement content, resulting in an experimental matrix of 16 runs. It was observed that although the compressive strength of solidified sludge improved at longer curing times, the increase was moderate after 7 days of curing. In addition, higher RHA and/or sludge ratios progressively reduced the strength of the samples. On the other hand, curing time had a positive effect on chromium leachability since the leaching concentration decreased considerably with an increase in curing time, up to 28 days. Furthermore, both the RHA and/or sludge content affected leachability, producing acceptable results, from a Thai regulatory perspective, at ratios of 0.50 or lower. Finally, the solidified sludge can be disposed of in a secure landfill and/or used as a construction material in a number of applications.

Durability of sea-sand containing concrete: Effects of chloride ion penetration

This paper describes an orthogonal experiment on the effect of water/cement ratio, water consumption per cubic meter, curing time, and type of sand on the response “resistance to chloride ion penetration”. A sea-sand containing concrete was used for the trials. An analysis of chloride ion diffusion coefficients at different factor levels was performed. A predictive model of chloride ion diffusion in concrete is developed through regression analysis. The experimental results show that when the water/cement ratio varies from 0.45 to 0.60, and the water consumption per cubic meter varies from 185 to 215 kg, and the curing time varies from 30 to 180 d then the size of the effects fall in the order (most significant first): curing time, type of sand, water consumption per cubic meter, and water/cement ratio. Chloride ion penetration is reduced, and better durability of the concrete is observed, with longer curing times, less water consumption per cubic meter, and a smaller water/cement ratio.

Influences of Initial Curing Conditions on the Microstructure of Fly Ash Cement System

In order to study the influences of initial curing conditions on fly ash (FA) cement concrete durability, fly ash cement samples with 30% replacement ratio were fabricated and cured in water at 10°C, 20°C, 30°Cand 40°C for 3d, 7d, 14d and 28d respectively. Hydration degrees of fly ash at early age were measured using the selective dissolve method. Correspondingly the pore structure and morphology of FA-cement mortar and compared cement mortar were studied by using MIP and SEM methods. Then early age compressive strengths of FA-cement concrete and compared normal cement concrete were tested. Experimental results show that initial curing temperatures and ages are important factors to fly ash early age hydration degree, FA-cement system microstructure, morphology and early age compressive strength etc. High curing temperatures and longer curing time can lead higher fly ash hydration degree, and then higher compressive strength of FA-cement concrete, and make the micro-structures of fly ash-cement system denser.

Experiments on integrated solidification and cementation of the cement-formation interface using the Mud Cake to Agglomerated Cake (MTA) method

Abstract Based on the scientific concept of Mud Cake to Agglomerated Cake (MTA), the integrated solidification and cementation of materials at the cement-formation interface was studied by mechanical evaluation, microstructure analysis (XRD, TG and ESEM), and fluid dissolution tests. The results of the mechanical evaluation show that compared with the existing method of MTC, the bond strength of the cement-formation interface increased by 37.81% (increasing up to 1 606.31% with longer curing time) with the MTA method. The results of microstructural analysis show that the synchronous hydration and hardening reaction between the mud cake and cement slurry occurred locally, and a little CSH(I) (calcium silicate hydrate) gel and heulandite gel formed. The results of fluid dissolution tests show that the mud cake in a finished sample made by the old method was dissolved and became a turbid drilling fluidr after it was immersed in water for 28 days. However, based on the MTA method, the agglomerated cake and hardened cement paste bonded together. The agglomerated cake was not dissolved and the water remained clear. All the above results corroborate two facts, one is that the mud cake has converted to agglomerated cake, the other is that the cement-formation interface has solidified and cemented integrally.

Proton exchange membrane bearing entangled structure: Sulfonated poly(ether ether ketone)/bismaleimide hyperbranch

Physical cross-linking of sulfonated poly(ether ether ketones) sPEEKs with hyper-branched bismaleimide oligomer (modified bismaleimide, mBMI) leads to densely packed polymer. Different curing conditions on the two sPEEK samples containing Bismaleimide (BMI) monomer and modified Bismaleimide oligomers (mBMI) mole ratios of 70:30 (mBMI(30)) and 2:98 (mBMI(98)) are present. As the amount of BMI monomer increases, the branched structure and their degree of entanglement with sPEEK polymer matrix also increase. More rigid and more compact membrane is found in the case of mBMI(30). In contrast, relatively loose entangled network is found for mBMI(98) sample where the mBMI unit remains far apart and mostly un-connected, until high concentration of mBMI(98) is present. The branched structure and their degree of entanglement with sPEEK polymer matrix increases with longer curing time. The results shows physical cross-linking with highly branched mBMI is effective in reducing water uptake, lower methanol permabiity with reduced sPEEK membrane swelling. Except for heavily entangled sample (sPEEK/mBMI(30)) annealed for 20 h, all membranes displayed fair proton conductivity above 10 −2 S/cm at room temperature. Methanol permeability is also substantially reduced to 1.39 × 10 −7 cm 2/s for sPEEK/15% mBMI(98). The DMFC single cell assembled by the sPEEK/20% mBMI(98) membrane (59 μm thickness) displayed the highest OCV of 839 mV with a power density reaching 30 mW/cm 2 at 60 °C. This value is higher than that using sPEEK membrane alone.

Potential utilization of riverbed sediments by hydrothermal solidification and its hardening mechanism

Hydrothermal solidification of riverbed sediments (silt) has been carried out in a Teflon (PTFE) lined stainless steel hydrothermal apparatus, under saturated steam pressure at 343–473 K for 2–24 h by calcium hydrate introduction. Tobermorite was shown to be the most important strength-producing constituent of the solidified silt. A longer curing time or a higher curing temperature was shown to be favorable to the tobermorite formation, thus promoting strength development; however, overlong curing time (24 h) seemed to affect the strength development negatively. The hardening mechanism consisted of the crystal growth/morphology evolution during the hydrothermal process. The species dissolved from the silt were precipitated first as fine particles, and then some of the particles seemed to build up the rudimental morphology of calcium silicate hydrate (CSH) gel. The CSH gel, with precipitated particles, appeared to cause some reorganization within the matrix, which made the matrix denser and thus gave an initial strength development. Tobermorite, transformed inevitably from the CSH gel, reinforced the matrix with its interlocked structure, and thus further promoted the strength development.

FTIR study and cation exchange capacity of Fe 3+- and Mg 2+-substituted calcium silicate hydrates

Single phases calcium silicate hydrates (1.1 nm tobermorite; Ca 5Si 6O 16(OH) 2·4H 2O), with Fe 3+ and Mg 2+ substitutions, were synthesized under hydrothermal conditions at 175 °C. The structure of different tobermorite samples was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results indicated that Fe and Mg ions played a key role in crystallization, morphology and structure of tobermorite. Mg 2+ increases crystallinity of tobermorite and changes its morphology from platy-shape at 4 h curing time to lamellar-shape at longer curing time. Fe 3+ increases imperfection of tobermerite at short curing time, however it increases crystallinity at longer curing time and the morphology of tobermorite changes magnificently from reticulated-shape to fiber-shape. FTIR proved that Fe + and Mg + increase silicate chains polymerization and increase the chain cross-linkage, which is consistent with tobermorite lamellar and fibers morphology that grow parallel to the b-axis (along the silicate chains). The cations exchange capacity (CEC) of Fe- and Mg-substituted tobermorites is lower than that of the unsubstituted tobermorite. Cross-linkage in the silicate chains was found to cause a reduction in cation exchange capacity.

Investigation of the Drug Release and Surface Morphological Properties of Film-Coated Pellets, and Physical, Thermal and Mechanical Properties of Free Films as a Function of Various Curing Conditions

The purpose of the present investigation was to elucidate the influence of curing on different physical properties of Eudragit NE and RS coating systems. Increased curing times resulted in decreased drug release rates from Eudragit NE-coated beads. However, an increase in drug release rates was noticed at longer curing times and higher temperatures for the Eudragit RS coating system. The surface morphological changes of the film-coated beads revealed that there were no visible macroscopic changes as a result of curing. The absence of any ibuprofen melting peak in the DSC thermograms of cured NE and RS coated beads confirmed that there was no surface crystallization of ibuprofen. These results indicated that the increase in drug release rates from RS coated pellets, when subjected to long curing times, resulted from loss of plasticizer. Free films of Eudragit NE exhibited an increase in tensile strength with increased curing times, whereas Eudragit RS free films showed a decrease in tensile strength beyond 4 h of curing at 70 and 90 degrees C. The film thicknesses and weights of free films of Eudragit RS prepared with triethyl citrate plasticizer were found to change more dramatically with curing than did free films of Eudragit RS prepared with ibuprofen as the plasticizer. An increase in pore volume was also observed with increased curing times for Eudragit RS free films. Such changes with curing were shown to be due to the loss of plasticizer molecules, leading to the formation of molecular-scale voids and channels.

Hydrothermal synthesis and characterization of aluminium and sulfate substituted 1.1nm tobermorites

Substitutions of sulfate and aluminum ions in calcium silicate hydrate (tobermorite) were investigated at 175 °C under saturated steam pressure. Structure and morphology of different tobermorite samples were investigated using XRD, FTIR and SEM. A sample of pure xonotlite was prepared to assist in FTIR band assignment of different tobermorites. Al 3+ decreases the degree of crystallinity at short curing time and increases crystallinity at longer curing times, with a sort of stabilization of small crystals. Al 3+ changes the morphology of tobermorite from platy-shape to lath-shape. Sulfate ion increases imperfection of tobermorite crystal structure and the morphology of tobermorite change magnificently to leafy shape. The FTIR spectra of all 1.1 nm tobermorite samples are nearly similar. All tobermorite samples have a significant concentration of Q 3 Si sites, which indicates cross-linking of the chains. Sulfate substitution for silicate in tobermorite structure is associated with the appearance of the bands at 1610 and 631 cm −1 which indicates the incorporation of CaO–H group in tobermorite structure. This indicated the charge compensation mechanism; SiO 4 4− is substituted by SO 4 2− and 2OH − .

Effect of curing on the broadband dielectric spectroscopy of powder coating

The effect of curing process of thermosetting powder coating consists of carboxylated polyester resin cured with triglycidyl isocyanurate has been investigated using broadband dielectric relaxation spectroscopy over a wide range of frequency (10 −1–10 6 Hz) and temperature (70–105 °C) for different constant curing times. The molecular dynamics of the glass relaxation process (α-process) was investigated as a function of curing time, frequency, and temperature. It has been found that, only one common α-relaxation process has been observed for all measured samples of different degree of curing stages, its dynamics and broadness were found to be curing time dependent. In addition, the curing time dependence of the dielectric relaxation strength, Δ ε, has also been examined for the α and β-relaxation processes. The Δ ε for the two relaxation processes decreased strongly at the beginning of curing process and then became almost constant at longer curing times. This finding implied that the numbers of reoriented dipoles decrease with curing time as a result of the formation of three-dimensional polymer network. Furthermore, the dislocation energy, ε s, calculated from the Meander model was found to be increased with increasing the curing time, i.e. the formation of a three-dimensional polymer network produces many structural defects or dislocation points. In addition, the activation energy of the curing process was calculated from the analysis of the calorimetric exothermic peaks of the curing process at different heating rates.

Effects of chitosan addition to DMEU‐processed cotton fabrics for adsorbing metallic ions in waste water

AbstractThis study examines the effects of adding chitosan to the curing treatment of cotton fabrics, using dimethylolethyleneurea as a crosslinking reagent; in particular, how the adsorption of the processed cotton fabrics for metallic ions is influenced. Different concentrations of added chitosan, different curing temperatures and time, as well as different adsorption times and temperatures were examined. The cotton fabrics studied were compared with other adsorptive materials, and also, were examined by Fourier Transform Infrared Analysis (FTIR), Scanning Electronic Microscope (SEM), and Thermal Gravity Analysis (TGA) to study the crosslinkage reaction. The experimental results were as follows: the adsorption of copper and zinc ions increases as chitosan concentration increases, with the best adsorption when chitosan concentration is 0.5%; the adsorption of copper and zinc ions increases as the curing temperature rises, with the best adsorption at 140°C; the adsorption increases with longer curing time, with the best adsorption at 6 min after the processing begins. For adsorption of zinc ions, the cotton fabrics containing chitosan have better adsorption than pure chitosan, but worse adsorption than activated carbon. For the adsorption of copper ions, chitosan is the best, processed cotton fabrics are the second, and activated carbon is the poorest. The adsorption of these two kinds of ions increases with the longer time and higher temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4440–4445, 2006

Curing Capability of Halogen and LED Light Curing Units in Deep Class II Cavities in Extracted Human Molars

Class II cavities were prepared in extracted lower molars filled and cured in three 2-mm increments using a metal matrix. Three composites (Spectrum TPH A4, Ceram X mono M7 and Tetric Ceram A4) were cured with both the SmartLite PS LED LCU and the Spectrum 800 continuous cure halogen LCU using curing cycles of 10, 20 and 40 seconds. Each increment was cured before adding the next. After a seven-day incubation period, the composite specimens were removed from the teeth, embedded in self-curing resin and ground to half the orofacial width. Knoop microhardness was determined 100, 200, 500, 1000, 1500, 2500, 3500, 4500 and 5500 microm from the occlusal surface at a distance of 150 microm and 1000 microm from the metal matrix. The total degree of polymerization of a composite specimen for any given curing time and curing light was determined by calculating the area under the hardness curve. Hardness values 150 microm from the metal matrix never reached maximum values and were generally lower than those 1000 microm from the matrix. The hardest composite was usually encountered between 200 microm and 1000 microm from the occlusal surface. For every composite-curing time combination, there was an increase in microhardness at the top of each increment (measurements at 500, 2500 and 4500 microm) and a decrease towards the bottom of each increment (measurements at 1500, 3500 and 5500 microm). Longer curing times were usually combined with harder composite samples. Spectrum TPH composite was the only composite showing a satisfactory degree of polymerization for all three curing times and both LCUs. Multiple linear regression showed that only the curing time (p < 0.001) and composite material (p < 0.001) had a significant association with the degree of polymerization. The degree of polymerization achieved by the LED LCU was not significantly different from that achieved by the halogen LCU (p = 0.54).

Strength Characteristics of the Cement-Stabilized Surface Layer in Dredged and Reclaimed Marine Clay, Korea

ABSTRACT A series of tests in both laboratory and field were performed to investigate the engineering and mechanical properties, especially flexural strength, of cement-stabilized soils. The strength of cement-stabilized soils mainly depends on water-to-cement ratio and curing temperature. The higher curing temperature and the longer curing time, the higher strength in cement-stabilized soils generates. The high ratio of water-to-cement results in lower strength. The compressive strength observed in the field is similar to the strength in the laboratory. Field tests on a cement-stabilized soil layer indicate that the strength is significantly affected by the thickness of the improved layer, which is directly related to the moment of inertia. In addition, the failure shape observed in a cement-stabilized layer in the field looks likes a bending failure type, because the flexural tensile strength, rather than the compressive strength, mainly dominates the failure of cement-stabilized layer. The flexural tensile strength is closely related to the moment of inertia. Therefore, the flexural tensile strength should be considered for determining the thickness and strength in improvement of soft clay.

Degree of conversion and permeability of dental adhesives

The aim of this study was to analyse the extent of polymerization of different adhesive films in relation to their permeability. One adhesive of each class was investigated: OptiBond FL; One-Step; Clearfil Protect Bond; and Xeno III. Adhesive films were prepared and cured with XL-2500 (3M ESPE) for 20, 40 or 60 s. Polymerization kinetic curves of the adhesives tested were obtained with differential scanning calorimetry (DSC) and data were correlated with microhardness. The permeability of the adhesives under the same experimental conditions was evaluated on human extracted teeth connected to a permeability device and analysed statistically. The results showed that the extent of polymerization obtained from DSC exotherms was directly correlated with microhardness. An increased level of polymerization after prolonged light-curing was confirmed for all adhesives. Simplified adhesives exhibited a lower extent of polymerization and showed incomplete polymerization, even after 60 s. An inverse correlation was found between the degree of cure and the permeability. This study supports the hypothesis that the permeability of simplified adhesives is correlated with incomplete polymerization of resin monomers and the extent of light exposure. These adhesives may be rendered less permeable by using longer curing times than those recommended by the respective manufacturer.

Salt Diffusion and Distribution in Meat Studied by23Na Nuclear Magnetic Resonance Imaging and Relaxometry

This study introduces the use of combined 23Na magnetic resonance imaging (MRI) and 23Na NMR relaxometry for the study of meat curing. The diffusion of sodium ions into the meat was measured using 23Na MRI on a 1 kg meat sample brined in 10% w/w NaCl for 3-100 h. Calculations revealed a diffusion coefficient of 1 x 10(-5) cm2/s after 3 h of curing and subsequently decreasing to 8 x 10(-6) cm2/s at longer curing times, suggesting that changes occur in the microscopic structure of the meat during curing. The microscopic mobility and distribution of sodium was measured using 23Na relaxometry. Two sodium populations were observed, and with increasing length of curing time the relaxation times of these changed, reflecting a salt-induced swelling and increase in myofibrillar pore sizes. Accordingly, the present study demonstrated that pore size and thereby salt-induced swelling in meat can be assessed using 23Na relaxometry.