Calculation of crosslink density in short chain networks

Hill, Loren W.

doi:10.1016/s0300-9440(97)00081-7

Cited by 307 publications

(164 citation statements)

References 14 publications

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“…The higher the number of active or effective crosslink points or junctions, the higher is the crosslink density. 33 The higher amount of epoxy functional groups in BGC provides a higher number of active crosslink points and a more densely crosslinked network by reacting with the active hydrogen atoms of the amine crosslinkers. The increase in the content of non-reactive EP in the resins results in a decrease in the crosslink density.…”

Section: Dynamic Mechanical Analysismentioning

confidence: 99%

The influence of structural modification and composition of glycidyl carbamate resins on their viscosity and coating performance

Harkal

Muehlberg

et al. 2010

J Coat Technol Res

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The synthesis, characterization, and coatings performance of a series of glycidyl carbamate (GC) resins synthesized from a hexamethylene diisocyanate biuret resin, glycidol, and alcohols were explored. The partial replacement of glycidol with alcohols was explored as a way to reduce the viscosity of multifunctional GC resins. Six modified GC resins were obtained by replacing one-third of the glycidol with alcohols and ether alcohols. The modified GC resins were characterized using FTIR and 13 C NMR. The alcoholmodified GC resins had significantly lower viscosity than that of the control GC resin. The effect of amount of alcohol modifier on resin viscosity was also studied by making a series of resins with different levels of modifier. Both amine-cured and self-crosslinked coatings were prepared from the resins. Coating properties such as hardness, impact strength, methyl ethyl ketone double rubs, flexibility, and adhesion were studied. Differential scanning calorimetry and thermogravimetric analysis were also used to study the thermal properties of the coatings. The resin structures and their coating performance showed an excellent correlation. The coating performance was found to be governed by the type of modifier, structural compositions of the modifier in the resins, type of amine crosslinkers, and techniques of crosslinking used.

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Section: Dynamic Mechanical Analysismentioning

confidence: 99%

The influence of structural modification and composition of glycidyl carbamate resins on their viscosity and coating performance

Harkal

Muehlberg

et al. 2010

J Coat Technol Res

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“…The literature reported that the high functionality of lignin gives rise to an increase in crosslink density of polyurethanes, so that several stress properties such as Young's modulus increased with lignin content [34]. The crosslink density, an average number of crosslinked points per unit volume, can be calculated from the storage modulus at the rubbery plateau using equation (4) [35]. (4) where v e is the crosslink density (×10 -5 mol/cc), E' is the compressive storage modulus (dyne/cm 2 ), ρ is the foam density (g/cc), R is the gas constant (8.3144×10 7 erg/K·mol) and T is the absolute temperature (K).…”

Section: Resultsmentioning

confidence: 99%

Compressive viscoelastic properties of softwood kraft lignin-based flexible polyurethane foams

et al. 2013

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Softwood kraft lignin (SKL)-based water-blown flexible polyurethane foams were prepared using SKL as a crosslinking agent and a hard segment polyol. Polyethylene glycol (PEG) as a soft segment diol and 2,4-toluene diisocyanate (TDI) were used. While increasing hard segment content caused the increase in crosslink density in foams, the foams became more and more viscous with increasing hard segment content due to the distinctive phase heterogeneity in foams. In this case, the contributiveness of the filler-like behaviors of separated hard segments always overtook the crosslinking effects derived from SKL in terms of overall viscoelasticity, thus the resultant viscometric properties such as tanδ max and hysteresis loss increased as hard segment content increased. Furthermore, increasing M n,PEG caused the severer microphase separation and intensified the filler effects in foams, thus the foams became more viscous with increasing M n,PEG . The 25 % and 65 % CFD values and Young's moduli of foams increased with increasing hard segment content due to the increase in crosslink density for foams, and the properties also increased with increasing foam density. Most of foams showed the support factors in the range of 2-3, which are suitable values for cushioning use. Even though the microscopic deformation behaviors in foams are irrelevant to foam density, the cyclic compressive tests showed that the higher foam density possess the better shape recovery performances.

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“…31 Dynamic mechanical thermal analysis was performed on dynamic mechanical thermal analyzer (NETZSCH 242 C, Germany) at a heating rate of 5°C min À1 in the range of À50 to 120°C with the sheet of 10 9 591 mm obtained under irradiation by UV plane light source (RW-UVAC301-40bh, Runwo Co., China) with light intensity 30 mW cm À2 for 60 s. The glass transition temperature (T g ) was defined as the peak of tand curve. The crosslinking densities (m e ) were calculated from the following formula based on the kinetic theory of rubber elasticity 32 :…”

Section: Instrumentationmentioning

confidence: 99%

Synthesis and properties of polyurethane acrylate modified by different contents of stearyl alcohol

Qin

Nie

2014

J Coat Technol Res

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Polyurethane acrylates (PUAs) modified by different amounts of stearyl alcohol were synthesized from stearyl alcohol (SA), isophorone diisocyanate, 2-hydroxyethyl acrylate, and polycaprolactone triol. The molecular structure was characterized by Fourier transform infrared spectroscopy. Real time infrared spectroscopy was used to investigate the kinetics of photopolymerization of synthesized PUAs. The volume shrinkage was measured by laser displacement sensor. The adhesion on glass, polycarbonate (PC), and polyvinyl chloride (PVC) was tested by the laser micrometer and universal testing machine. The glass transition temperature (T g ) and storage modulus (E¢) were measured by dynamic mechanical analyzer (DMA). The pendulum hardness, pencil hardness and flexibility were also measured. The results showed that the greater the amount of SA in synthesized PUAs, the lower the volume shrinkage and the better the adhesion to glass, PC, and PVC substrates.

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Calculation of crosslink density in short chain networks

Cited by 307 publications

References 14 publications

The influence of structural modification and composition of glycidyl carbamate resins on their viscosity and coating performance

The influence of structural modification and composition of glycidyl carbamate resins on their viscosity and coating performance

Compressive viscoelastic properties of softwood kraft lignin-based flexible polyurethane foams

Synthesis and properties of polyurethane acrylate modified by different contents of stearyl alcohol

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