Activation Energy Of Swelling Research Articles

The effect of PF/PVAC weight ratio and ambient temperature on moisture absorption performance of bamboo‐bundle laminated veneer lumber

The veneer preprocessing densification is a vital procedure in the manufacturing process of long‐span bamboo‐based engineering material, bamboo‐bundle laminated veneer lumber (BLVL). The adhesive used in the preprocessing densification process was the mixture of phenol formaldehyde (PF) resin and polyvinyl acetate (PVAC) resin. The objective of this study was to investigate the effect of PF/PVAC weight ratio on the moisture absorption performance of BLVL, as well as the effect of ambient temperature on the hygroscopic swelling performance for BLVLs with a PF/PVAC ratio of 6:1. The results indicated that the water absorption swelling rate and weight gain rate of the BLVLs decreased as PF/PVAC ratio increased at 63°C. The absorption behavior of BLVL was found to obey Fick's law at 63°C approximately. The higher the PF/PVAC ratio, the lower swelling parameter KSR and D values were obtained. However, PF/PVAC ratio exerted little effect upon the bending properties(modulus of rupture and elasticity) of BLVL. Temperature has a significant effect on the moisture absorption performance of BLVL (6:1 PF/PVAC ratio). The higher the temperature, the greater swelling and weight gain rate was obtained, as well as KSR and D values. The calculated swelling activation energies (ES) were 25.79 and 22.45 KJ mol−1 for BLVLs with 6:1 PF/PVAC ratio and the ones with neat PF resin, respectively, while the diffusion activation energies (ED) were 10.62 and 8.47 KJ mol−1. POLYM. COMPOS., 37:955–962, 2016. © 2014 Society of Plastics Engineers

Temperature effect on the swelling of PAAm‐κ‐carrageenan composites

AbstractThe steady‐state fluorescence (SSF) technique was used for studying swelling of disc‐shaped polyacrylamide (PAAm)‐κ‐carrageenan (κC) composites which were prepared by free‐radical crosslinking copolymerization at 80°C. Pyranine was introduced as a fluorescence probe during polymerization. Swelling experiments were performed in water at various temperatures by real‐time monitoring of the pyranine (Py) fluorescence intensity, I which decreased as swelling proceeded. Stern–Volmer equation is modified for low quenching efficiencies to interpret the behavior of Py intensity during the swelling of PAAm‐κC composites. The Li‐Tanaka equation was used to determine the swelling time constants, τ1, and cooperative diffusion coefficients, D0, from fluorescence intensity, weight, and volume variations of the composites at various temperatures. It was observed that τ1 first decreased up to 40°C and then increased; naturally, D0 increased up to 40°C and then decrease for all κC content gels. Swelling activation energies, ΔE, were measured for the swelling composites, which are found to be exothermic and endothermic in between 30–40 and 40–60°C, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Swelling activation energy of κ‐carrageenan in its gel state: A fluorescence study

AbstractA steady‐state fluorescence technique was employed to study the swelling of κ‐carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. The fluorescence intensity of pyranine was measured during the insitu swelling process of κ‐carrageenan gels. The fluorescence intensity increased exponentially as the swelling time increased. The increase in the fluorescence intensity was modeled with the Li–Tanaka equation, from which the swelling time constants and cooperative diffusion coefficients were determined. The swelling time constants decreased and the cooperative diffusion coefficients increased as the swelling temperature was increased. The swelling activation energies were measured to be 47.05 kJ/mol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Study on swelling of hydrogels (PAAm) at various temperatures by using fluorescence technique

Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) hydrogels. Disc-shaped gels were prepared by free-radical crosslinking copolymerization of acrylamide (AAm) with N, N′- methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine was measured during in situ swelling process at various temperatures and it was observed that fluorescence intensity values decreased as swelling is proceeded. Li–Tanaka equation was used to determine the swelling time constants, τc and cooperative diffusion coefficients, Dc from intensity, weight and volume variations during the swelling processes. It is observed that swelling time constants, τc decreased and diffusion coefficients, Dc increased as the swelling temperature is increased. The swelling activation energies, ΔE were measured from the intensity, weight and volume variations and found to be 10.7, 32.2 and 64.1 kJ mol−1, respectively.

Small Molecule Diffusion into Swelling Iota-Carrageenan Gels: A Fluorescence Study

Small molecule diffusion into Iota-Carrageenan gel was studied by using steady-state fluorescence (SSF) technique. Pyranine, dissolved in water was used as fluorescence probe. Fluorescence emission intensity, Ip, and scattered light intensity, Isc, were monitored to study diffusion and swelling processes at various temperatures respectively. Fickian and Li-Tanaka models were elaborated to produce diffusion, D, and collective diffusion, D 0, coefficients. Diffusion and swelling activation energies were also obtained and found to be 20.5 kj mol−1 and 28.2 kj mol−1, respectively.

Influence of temperature on radiation-induced graft polymerization of styrene onto poly(ethylene terephthalate) nuclear membranes and films

The effect of temperature on the kinetics of radiation-induced graft polymerization of styrene onto poly(ethylene terephthalate) (PETP) nuclear membranes with varying parameters (pore diameter, pore density and average distance between the pores) and onto PETP films of different thickness has been studied. Graft polymerization was carried out by preirradiation in air and in vacuum. The overall activation energy of grafting and the activation energy of swelling of PETP in toluene have been obtained. It was found that for preirradiation in vacuum, an Arrhenius plot has two linear ranges for the initial grafting rate. The activation energy in the low temperature range correlates with the activation energy for PETP swelling. The activation energy in the high temperature range is determined by the kinetics of graft polymerization. For preirradiation in air, the Arrhenius plot of the initial grafting rate gives an activation energy which approximately corresponds to the initiation of grafting by oxy radicals. The dependence of the critical thickness of the PETP matrix on temperature has also been obtained for preirradiation in vacuum. The form of this dependence is identical to that of the rate of graft polymerization.