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1.
Steady state fluorescence (SSF) and UV–visible techniques have been used to study neck growth and equilibration processes during the coalescence of hard latex particles. Latex films were prepared separately by annealing pyrene (Py) labelled and unlabelled poly(methyl methacrylate) (PMMA) particles above their glass transition temperature. During the annealing processes, the optical clarity of the films increased considerably. Direct fluorescence emission of excited pyrene from labelled latex films was monitored as a function of annealing temperature to detect this change. Void closure temperature (Tc) and time (tc) were determined at the point where the fluorescence emission intensity became maximal. Below this point, the increase in fluorescence intensity (Iop) against temperature was used to determine the activation energy for viscous flow (ΔH≈47kcalmol−1). The decrease in Iop above the void closure temperature was used to determine the backbone activation energy (ΔE≈44kcalmol−1) for the interdiffusing chains. Unlabelled PMMA particles were used to prepare films for UV–vis measurements. The transmitted photon intensity (Itr) from these films increased as the annealing temperature was increased. This behaviour was also used to determine the backbone activation energy (ΔE≈35kcalmol−1) for the interdiffusing chains. © Society of Chemical Industry. 相似文献
2.
Void closure process due to viscous flow was studied during film formation from high-T latex particles. Steady-state fluorescence and photon transmission techniques were used to probe the evolution of optical clarity during film formation. The latex films were prepared from pyrene (P)-labeled poly(methyl methacrylate) particles and annealed in 10-min time intervals above glass transition temperature. Fluorescence intensity from P was measured after each annealing step. A relation for void closure time versus fluorescence intensity was derived, using the Vogel—Fulcher equation. Viscosity constant B was measured from the above relation and found to be as 11 × 103 K. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 655–661, 1997 相似文献
3.
A photon transmission method has been used to study interdiffusion processes during film formation from hard latex particles. Films with different latex content were prepared separately by annealing poly(methyl methacrylate) (PMMA) particles above the glass transition temperature. The transmitted photon intensity from these films increases as the annealing temperature is increased. Monte Carlo simulations are performed for photon transmission through a rectangular lattice. The increase in the transmitted photon intensity (Itr) is attributed to the latex content (film thickness) for the annealed film samples. It is observed that as the latex particles are packed (film thickness is increased) fewer voids or cracks are formed in the films. A negative absorbance coefficient has been measured above the 180 °C annealing temperature. Packing coefficients are obtained for films having various latex contents. © 2000 Society of Chemical Industry 相似文献
4.
Saziye Ugur Ayse Alemdar Önder Pekcan 《Journal of Coatings Technology and Research》2005,2(7):565-575
This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene
(PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles
and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature
(t3) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (Is) and fluorescence intensity (Ip) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite
films was monitored by using photon transmission intensity, Itr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum
film formation temperature, Tq, and healing temperatures, Th, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It
was observed that both activation energies increased as the percent of SNaM was increased in composite films. 相似文献
5.
In this work, the effect of hard particle size and blend ratio on the film formation behavior of hard polystyrene (PS) and soft poly(n‐butyl acrylate) (PBA) latex blends was studied by means of steady‐state fluorescence and UV–visible techniques in conjunction with atomic force microscopy. Three different sets of latexes were synthesized: PBA latex (diameter 97 nm), pyrene (P)‐labeled large PS (LgPS; diameter 900 nm), and small PS (SmPS; diameter 320 nm). Two different series of latex blends (LgPS/PBA and SmPS/PBA) were prepared with varying blend composition at room temperature separately. Films were then annealed at elevated temperatures above glass transition (Tg) temperature of PS. Fluorescence intensity (IP) from P and photon transmission intensity (Itr) were measured after each annealing step to monitor the stages of film formation. The results showed that a significant change occurred in IP and Itr at a certain critical weight fraction (Rc) of PBA. Below Rc, two distinct film formation stages, which are named as void closure and interdiffusion, were seen. However, at PBA concentrations nearer to or above Rc, no film formation can be achieved. Comparing to the LgPS/PBA, the sintering process of SmPS/PBA particles occurred at much lower temperatures. Film formation stages for R < Rc were modeled, and related activation energies were calculated. Void closure (ΔH) and interdiffusion (ΔE) activation energies for SmPS/PBA were also found smaller in comparing with LgPS/PBA series. However, ΔH and ΔE values were not changed much with the blend composition for both series. POLYM. COMPOS., 31:1637–1652, 2010. © 2009 Society of Plastics Engineers 相似文献
6.
We have employed steady sate fluorescence (SSF) and UV‐visible (UVV) techniques to determine the film formation behavior of latex blends. Blend films were prepared from mixtures of a high‐Tg pyrene (P) labeled polystyrene (PS) latex and a low‐Tg copolymer of poly(butyl acrylate‐co‐methyl methacrylate) (BuA/MMA4). Eleven different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass‐transition (Tg) temperature of polystyerene for 10 min. Fluorescence intensity (IP) from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, Itr. Film morphologies were examined by atomic force microscopy (AFM). A significant change occurs in both IP and Itr intensities at a certain critical weight fraction of hard latex (Rc = 0.3). Above Rc, two distinct film formation stages, which are named as void closure and interdiffusion processes, were seen in fluorescence data. Transparency of the films was decreased with decreasing PS content, indicating that a phase separation process occurs between PS and BuA/MMA4 phases by thermal treatment, which results in turbid films. However, below Rc, no change was observed in IP and Itr upon annealing, whereas transparency increased overall with increasing BuA/MMA4 ratio. We explained this result as the phase separation process between PS and BuA/MMA4 blends. These results were also confirmed by AFM pictures. Film formation stages above Rc were modeled and related activation energies were calculated. POLYM. COMPOS., 27:431–442, 2006. © 2006 Society of Plastics Engineers 相似文献
7.
Film formation from surfactant‐free polystyrene (PS) latex was performed in the presence of 5% Na‐montmorillonite (NaMMT). The composite films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures above the glass‐transition (Tg) temperature of polystyrene. Scattered light (Is) and fluorescence intensity (IP) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T0, and healing temperatures, Th, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities. POLYM. COMPOS., 27:299–308, 2006. © 2006 Society of Plastics Engineers 相似文献
8.
Steady‐state fluorescence technique was used for studying film formation from TiO2 covered nano‐sized polystyrene latex particles. The composite films were prepared from pyrene (P)‐labeled PS particles by covering them with various layers of TiO2 at room temperature. These films then annealed at elevated temperatures in 10 min time interval above glass transition (Tg) temperature of polystyrene. Five different composite films were studied in various TiO2 layer contents. Fluorescence emission intensity, IP from P was measured after each annealing step to monitor the stages of film formation. Films present significant increase in IP above the certain onset temperature called minimum film forming temperature, T0. However, at higher annealing temperatures, IP showed a decrease. Increase and decrease in IP were modeled by void closure and interdiffusion processes and related activation energies were determined, respectively. Dissolution of annealed PS film, with high TiO2 content presented a nice, ordered nano‐sized ceramic structure, which may predict the construction of nano‐layer photonic crystals. POLYM. COMPOS., 27:651–659, 2006. © 2006 Society of Plastics Engineers 相似文献
9.
A steady state-fluorescence (SSF) technique for studying film formation from surfactant-free, slightly crosslinked polystyrene
(PS) latex particles is reported. The powder films were prepared from fluorescein (F)-labeled PS particles at room temperature.
The mechanically strong films were obtained by annealing these films at elevated temperatures in 5, 10, 20, and 30 min time
intervals above the glass transition (Tg) temperature of polystyrene. Scattered light (Is) and fluorescence (IF) intensities from F were monitored after each annealing step to investigate the three different film formation stages called
void closure, healing, and interdiffusion. The evolution of transparency of the latex films was monitored by using a photon
transmission technique. Scanning electron microscopy (SEM) was employed to detect the variation in physical structure of the
annealed latex films. Onset temperature for void closure, Tm’, and healing temperatures, Th, were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were also modeled
and the related activation energies were also determined. It was observed that lower energy is needed for the void closure
process than interdiffusion of chains across the particle-particle boundaries. 相似文献
10.
This work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)‐labeled nano‐sized polystyrene (PS) and poly(n‐butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (Tg) of polystyerene. Monomer (IP) and excimer (IE) intensities from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, Itr. Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component (PS) in the blend is decreased, a significant change occurred in both IE/IP and Itr curves at a certain critical weight fraction (50 wt%) of PS hard latex. Two distinct film formation stages, which are named as void closure and interdiffusion were seen in (IE/IP) data above this fraction. However, below 50 wt% PS no film formation was observed. AFM pictures also confirmed these findings. Void closure and interdiffusion stages for (50–100) wt% range of PS were modeled and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition in this range. POLYM. COMPOS., 31:1611–1619, 2010. © 2009 Society of Plastics Engineers 相似文献
11.
A UV-visible (UVV) technique was used to monitor the evolution of transparency during film formation from hard latex particles. Two different latex films were prepared from particles with high and low molecular weight (HM and LM) poly(methyl methacrylate) (PMMA) separately and annealed at elevated temperatures in various time intervals above the glass transition temperature (Tg). In both films, a continuous increase in the transmitted photon intensity (Itr) was observed above 160°C as the annealing temperature was increased. However, the reflected photon intensity (Irf) first decreased and then increased by showing a minimum in the same temperature range as the annealing temperature was increased. The increase in the transmitted photon intensity (Itr) is attributed to increase in the “crossing density” at the junction surface. The activation energies for back-and-forth motion (ΔEtr) were measured and found to be around 35 and 25 kcal/mol for the reptating polymer chain across the junction surface in the LM and HM films, respectively. The decrease in Irf was explained by the void-closure mechanism, and the increase in the Irf above 160°C was again attributed to the increase in the crossing density at the junction surface. Back-and-forth activation energies (ΔErf) were measured to be around 47 and 18 kcal/mol and the void-closure constants (B) were found to be around 24 × 103 and 12 × 103 K for the LM and HM film samples, respectively. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 339–351, 1998 相似文献
12.
In this study, the effect of multi‐walled Carbon nanotube (MWNT) on film formation behavior of Polystrene (PS) latex film was investigated by using steady state fluorescence technique. Films were prepared by mixing of pyrene (P)‐labeled PS latex with different amounts of MWNTs varying in the range between 0 and 20 wt%. After drying, MWNT containing films were separately annealed above glass transition temperature (Tg) of PS ranging from 100 to 270°C for 10 min. In order to monitor film formation behavior of PS/MWNT composites, Scattered light (Is) and fluorescence intensities (IP) from P were measured after each annealing step to monitor the stages of film formation. At 0–20 wt% range of MWNT content films, minimum film formation (To), void closure (Tv), and healing, (Th) temperatures were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that while void closure activation energies increased, backbone activation energies decreased as the percent of MWNT is increased in the composite films. POLYM. COMPOS., 35:817–826, 2014. © 2013 Society of Plastics Engineers 相似文献
13.
The steady-state fluorescence technique was used to examine the healing and interdiffusion of polymer molecules as a function of solid content during annealing of latex films above the glass transition (Tg). Films were prepared from a mixture of naphthalene (N)- and pyrene (P)-labeled poly(methy methacrylate) (PMMA) latex particles. Above Tg, interdiffusion of polymer chains was observed by detecting the steady-state energy transfer from excited naphthalene to pyrene molecules. Various latex films with different latex content were used to measure the critical occupation percent for the reliable steady-state fluorescence measurements. Diffusion activation energies in these latex films were measured and found to be around 30 kcal/mol, which was attributed to the backbone motion of PMMA chains. © 1996 John Wiley & Sons, Inc. 相似文献
14.
This work reports a steady state fluorescence (SSF) technique for studying film formation from mixture of Al2O3 and polystyrene (PS) latex particles. The composite films were prepared from dispersion of pyrene (P)‐labeled PS particles in Al2O3 solution at room temperature and annealed at elevated temperatures in 10‐min time interval above glass transition (Tg) temperature of polystyrene. Nine different composites film were studied in various latex contents. Fluorescence intensities (IP) from P were measured after each annealing step to monitor the stages of film formation. No variations in IP were detected for the films prepared with higher than 33 wt% Al2O3 content. However films prepared below 33 wt% Al2O3 content show considerable increase in IP above the certain onset temperature called minimum film forming temperature, T0. Healing temperatures Th, were determined from the maxima of IP. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 20 and 97 kJ.mol–1, respectively. POLYM. COMPOS., 26:352–360, 2005. © 2005 Society of Plastics Engineers 相似文献
15.
Steady state fluorescence (SSF) technique conjunction with optical microscopy were used to study the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend upon annealing above glass transition in elevated time intervals. The PS/PMMA blends were prepared from dissolution of pyrene (P) and naphthalene (N) labeled PS and PMMA particles, respectively. Monte Carlo simulations were performed to model the N and P fluorescence intensities (IN and IP), using photon diffusion theory. Number of N and P photons (NN and NP) emerging from the front surface of the blend are calculated when only N is excited, where NP photons are combined of photons from radiative (NPR) and nonradiative (NPNR) energy transfer processes. Optical microscopy images were taken at each annealing step to support our findings from fluorescence measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2104–2110, 2006 相似文献
16.
Latex films were prepared by annealing pyrene (Py)‐labeled poly(methyl methacrylate) particles at glass‐transition temperature (100°C). These films were then irradiated by γ‐rays from 60Co in a gamma cell at room temperature at the same dose rate (rad/h) for 30 min. Before dissolution films were annealed at elevated temperatures for a 30‐min time interval to complete the film formation process. Steady‐state fluorescence (SSF) technique were used to monitor the dissolution of these irradiated latex films. The dissolution of films in chloroform–heptane (80–20%) mixture was monitored in real time by the Py fluorescence intensity change. Relaxation constants k0 and desorption coefficients Dd of polymer chains were measured. It was observed that both Dd and k0 values first increased and then decreased by increasing the annealing temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 129–137, 2002 相似文献
17.
A photon‐transmission method was used to probe the evolution of transparency during film formation from polystyrene (PS) particles with different molecular weights. The latex films were formed at room temperature from the PS particles having two different average molecular weights and annealed at elevated temperatures in various time intervals above the glass transition (Tg). Onset temperatures (TH) at given times (τH) for the optical clarity of films formed from low (LM) and high molecular (HM) weight PS particles were used to calculate the healing activation energies for the minor chains and found to be 22.0 ± 0.5 and 27.0 ± 0.6 kcal/mol, respectively. The increase in the transmitted photon intensity, Itr, above the TH was attributed to increase in the number of interfaces that disappeared. The Prager–Tirrell (PT) model was employed to interpret the increase in crossing density at the junction surface. The backbone activation energies (ΔE) were measured and found to be 127.8 ± 2.5 kcal/mol for a diffusing polymer chain across the junction surface for LM and HM latex films. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 866–874, 2000 相似文献
18.
The contribution of viscous flow to void‐closure processes during film formation with hard latex particles was studied. Film optical clarity was used to follow the progress of this event. The latex films were prepared from poly (methyl methacrylate) (PMMA) particles and annealed in 10 min time intervals above the glass transition (Tg) temperature. Scanning electron microscopy (SEM) was used to detect the variation in the physical structure of the annealed films. To mimic the latex film‐formation process, Monte Carlo simulations were performed for photon transmission through the latex film and the number of transmitted and scattered photons are calculated as a function of the mean free path. A relation for transmitted light intensity, Itr versus void closure (time)1/2 (t1/2) was derived by using the Vogel–Fulcher viscosity equation. The viscosity constant, B, was produced using this Itr(t1/2) relation at various temperatures and found to be 12.8 × 103 K. It is shown that Monte Carlo results justified the Itr(t1/2) relation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 981–988, 1999 相似文献
19.
A new technique, based on steady-state fluorescence measurements, is introduced for studying dissolution of polymer films. These films are formed from naphthalene and pyrene labeled poly(methyl methacrylate) (PMMA) latex particles, sterically stabilized by polyisobutylene. Diffusion of solvent (chloroform) into the annealed latex film was followed by desorption of polymer chains. Annealing was performed above Tg at various temperatures for 30-min time intervals. Desorption of pyrene labeled PMMA chains was monitored in real time by the pyrene fluorescence intensity change. Desorption coefficients were found to be between 1 and 4 × 10−10 cm2/s and two different dissolution mechanisms were detected. © 1996 John Wiley & Sons, Inc. 相似文献
20.
aziye Uur
nder Yarg Yasemin Yüksel Durmaz Bünyamin Karagz Niyazi Bak Yusuf Yac
nder Pekcan 《Polymer Composites》2011,32(6):869-881
This work reports on the application of steady state fluorescence (SSF) technique for studying film formation from poly(methyl methacrylate) (PMMA) latex and poly(divinylbenzene) (PDVB) microsphere composites. Pyrene (P) functionalized PDVB cross‐linked spherical microspheres with diameters of 2.5 μm were synthesized by using precipitation polymerization technique followed by click coupling reaction. The diameter of the PMMA particles prepared by emulsion polymerization were in the range of 0.5–0.7 μm. PMMA/PDVB composite films were then prepared by physically blending of PMMA latex with PDVB microspheres at various composition (0, 1, 3, 5, 10, 20, 40, and 60 wt%). After drying, films were annealed at elevated temperatures above Tg of PMMA ranging from 100 to 270°C for 10 min time intervals. Evolution of transparency of the composite films was monitored by using photon transmission intensity, Itr. Monomer (IP) and excimer (IE) fluorescence intensities from P were measured after each annealing step. The possibility of using the excimer‐to‐monomer intensity ratio (IE/IP) from PDVB microparticles as a measure of PMMA latex coalescence was demonstrated. Diffusion of the PMMA chains across the particle–particle interfaces dilutes the dyes, increasing their separation. The film formation stages of PMMA latexes were modeled by monitoring the IE/IP ratios and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the PDVB composition in the studied range. SEM images of PMMA/PDVB composites confirmed that the PMMA particles undergo complete coalescence forming a continuous phase in where PDVB microspheres are dispersed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers 相似文献