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1.
A water-soluble styrene–maleic anydride copolymer (SMA) is derivatized with different lipophilic groups, butylamine and dodecylamine, with different degrees of substitution (5, 15, and 30%). These lipophile-grafted SMAs are water-soluble, and their solutions are transparent. A plot of I1/I3 as a function of polymer concentrations indicates the extent of aggregate formation. Surface tension methods also verify the existence of aggregates. It is found that the aggregates begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I1/I3 as a function of polymer concentrations for SMAs of different molecular weights derivatized with different lipophile with varying degrees of substitution show that the polymers with a higher degree of substitution and lower molecular weights aggregate at lower concentrations. Polymers substituted by butylamine form aggregates at a very high concentration, independent of the degree of sub-stitution. These phenomena are interpreted in terms of hydrophobic interactions as in micelles formed from surfactants. The higher degree of dodecyl-substituted SMA solubilizes pyrene at higher concentrations, and these pyrene solubilized solutions show pyrene excimer emission spectra. These emission spectra are used to characterize the relative size and hydrophobicity of aggregates. © 1993 John Wiley & Sons, Inc. 相似文献
2.
Souheng Wu 《Polymer Engineering and Science》1990,30(13):753-761
We present chain structure, phase morphology, and toughness relationships in thermoplastic polymers and polymer/rubber blends. In neat polymers, molecular aspects of craze/yield behavior are controlled by two chain parameters: entanglement density νe and characteristic ratio C∞. The crazing stress is proportional to ν, and the yield stress is proportional to C∞. The dispersed rubber toughens a polymer/rubber blend mainly by promoting energy dissipation of the matrix. The toughening efficiency correlates with the rubber phase morphology and the chain structure of the matrix. 相似文献
3.
The tensile behavior of polyethylene/ethylene vinyl acetate (PE/EVA) polymer blends filled with calcium carbonate (CaCO3) was studied using tensile and viscoelastic tests. The relations between tensile properties (modulus, strength, etc) of oriented and unoriented PE/EVA-CaCO3, and void volume of polymer/CaCO3 interface, PE/EVA blend ratio, and CaCO3 content were investigated. The results indicated that the tensile strength and elongation of PE/EVA-CaCO3 decreased with CaCO3 content and PE blend ratio for unoriented PE/EVA-CaCO3 systems. In the case of oriented samples, the relative modulus (E/E, where E and E are the modulus of oriented composites and the modulus of oriented matrix, respectively) of PE/EVA-CaCO3 is larger than that of PE/CaCO3 by increasing the EVA content relative to PE and CaCO3. The value of E/E can be simply expressed as the function of void volume and CaCO3 modulus to polymer matrix modulus. 相似文献
4.
Bamidele Ogbe Solomon Volker Hecht Clemens Posten Wolf-Dieter Deckwer 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):94-97
An estimation of the true growth yields and maintenance coefficients for Comamonas acidovorans DSM 6426 under continuous cultivation on quinoline has been performed. The data were checked for consistency using available electron, carbon and nitrogen balances. The true biomass energetic yields, ηmax, and energetic maintenance coefficients, me, were estimated using two models based on control of growth rate and control of substrate uptake rate, respectively. The estimations were converted to the various familiar true growth yield and maintenance units such as substrate-based (Y, mS/X), oxygen-based (Y, m) and carbon dioxide-based (Y, m) units. For the complete mineralization of quinoline by C. acidovorans, values of ηmax = 0.371 and me = 0·0426 h?1 were obtained. 相似文献
5.
Droplets of polymer blends flowing through convergent channels undergo collisions and coalescence because of the appropriate wineglass‐shaped flow paths with essential flow constriction at the entrance zone. Therefore, an attempt has been undertaken to use capillary flow for studying coalescence phenomena in polymer blends. When the initial drop diameters in a barrel (before extrusion), db, and in the extrudate, de, are measured, coalescence efficiency can be easily calculated as Ec = d/d, provided that no breakup of elongated domains occurs. Compared with methods employing simple shear flow, it has several advantages. For example, the convergent flow pattern combining both shear and extensional flows is directly related to industrial processing operations like extrusion, injection molding, blowing, etc. The method imposes minor limitations on processing parameters and materials used. Applicability of the technique proposed was verified by systematic studies of coalescence in PMMA/PS binary melts blends during capillary extrusion and by comparing these results to theoretical predictions and experimental data from literature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
6.
A calorimetric study for estimating crosslinking densities of polydimethylsiloxane (PDMS) networks is presented. It involves the experimental determination of the heat capacities of the polymer with (C) and without (C) crosslinking. The theoretical basis of the method is described as well as the procedure used for the determination of the Cps. The crosslinking densities of PDMS networks, determined by absorbency (swelling) measurments, using the Flory-Rehner equation, and by the method described here, are compared. The PDMS, obtained by the anionic synthesis of octamethylcyclotetrasiloxane, was analyzed by gel permeation chromatography and infrared spectroscopy. Separate samples of the polymer were further crosslinked at different network densities. The Cps and the thermal stabilities were determined by DSC and TGA, respectively. The results indicate that the crosslinking density ratios of the polymer networks calculated by the relation ΔC/C are in reasonable agreement with those obtained from absorbency measurements. The crosslinking density can also be obtained from heat capacity measurments if the density of the network is known at the temperature that ΔCp is obtained. © 1995 John Wiley & Sons, Inc. 相似文献
7.
V. I. Dakin 《应用聚合物科学杂志》1996,60(7):999-1003
The computed dependencies of elastic characteristics of branched-network polymers were obtained on the basis of the Takayanagi series model. The moduli ratio (λ) for branched-network and branched polymers increases as a result of an increase of the moduli ratio of network and branched phases (E/E) and the network phase fraction (Vnet). The λ-increase as a function of Vnet is larger than in the case of the E/E dependence. On the basis of computed dependencies, the experimental results for the radiation crosslinked SBS block copolymer were considered. The experimental results agree with the computed de-pendencies for the hetergeneous branched-network polymers with E/E ≈︁ 20. The influence of entanglements on the elastic characteristics of branched-network polymers is discussed. © 1996 John Wiley & Sons, Inc. 相似文献
8.
With the help of a counter‐rotating transparent rheometer equipped with an optical microscope, the erosion of single, commercial carbon black agglomerates suspended in a polyisobutylene fluid was accurately recorded in situ. We observed that clouds of very small aggregates were leaving the agglomerate at 45 and 225° in the shear gradient–flow direction plane, where the stress is maximum. The distribution of the arrached aggregates is more efficient when the carbon black agglomerate is more asymmetric. A spherical agglomerate of critical radius R0 will reach a radius Rt at time t following R ? R = at, a being a constant. This implies that the rate at which the number of aggregates is leaving the agglomerate is a constant, independent of the size of the agglomerate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1627–1629, 2001 相似文献
9.
This article reports the scaling laws relating the synthesis conditions with the crosslinking density (νe) and swelling degree (S) of poly(N‐vinylimidazole) hydrogels (PVI) prepared by radical crosslinking copolymerization in aqueous solution, with N,N′‐methylene bisacrylamide (BA) as crosslinker. Multiple linear regression of νe versus BA concentration ([BA]) and total comonomers concentration (CT) in double log scale render the scaling law νe ~ C × [BA]1.04 as comparable to that predicted by the model of polymer network with pendant vinyl groups (νe ~ CT × [BA]), and showing inverse dependence on CT to that expected, following from stoichiometry, for an ideal network (νe ~ 2[BA]/CT). S scales with νe through a solvent‐dependent exponent ranging from ?0.46 to ?0.54, only slightly over the value predicted by the Flory–Rehner theory (?0.6) or the blob's model by de Gennes (?0.5 to ?0.8). Finally, the scaling law of S with the composition of the reacting mixture is also solvent‐dependent and it seems to result not only from the dependence of νe on CT and [BA] but also from that of v2r, the polymer volume fraction in the reference state, and χ, the polymer–solvent interaction parameter. Models used seem to overestimate the contribution of entanglements to the effective crosslinking density of PVI. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 263–269, 2007 相似文献
10.
Organic polymer plating properties of 6‐substituted‐1,3,5‐triazine‐2,4‐dithiol mono sodium salts were investigated in the presence of various supporting electrolytes. Among these, the NaNO2 supporting electrolyte greatly accelerated the film formation rate in polymer plating. The accelerating effect of NaNO2 was further confirmed by comparing plating potentials in the presence of NaNO2 and Na2CO3. The potentiostatic polymer plating of DAN in the presence of the NaNO2 supporting electrolyte took place in the potential range of 1.65–1.8 V (compared against saturated calomel electrode reference). Film formation was influenced by such factors as the pH of solution and both the chemical structure and the concentration of triazine dithiol. In polymer platings, NO anions are thought to be electrochemically oxidized to yield NO radicals and these radicals react with DAN to yield new thiyl radicals. The thiyl radicals in the DAN molecules couple with each other by means of disulfide bonds, resulting in the growth of polymer film. Organic polymer plating films are shown to contain disulfide bonds, monosulfide bonds obtained by the reaction between allyl groups and thiyl radicals, and network chains. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2300–2309, 2001 相似文献
11.
The viscoelastic properties of a rubber–resin blend, which influences performance of the blend as a pressure-sensitive adhesive, depend upon the structure of the resin as well as its molecular weight. The effect of the concentration of a compatible resin in the blend was examined using a mechanical spectrometer. Four types of resins were used. These are the rosin esters, polyterpenes, pure monomer resins such as polystyrene and poly(vinyl cyclohexane), and petroleum stream resins. Each was examined in blends with both natural rubber and styrene–butadiene rubber over a range of concentrations. It is shown that the temperature of the tan δ peak for compatible systems can be predicted by the Fox equation, T = W1T + W2T, where W1 and W2 are the weight fractions of the resin and rubber, respectively, and the Tg's are the tan δ peak temperatures in K. The plateau modulus G for a blend can be identified as the G′ value in the rubbery plateau at the point where tan δ is at a minimum. The relationship between G and G, the plateau modulus for the undiluted elastomer, is shown to be proportional to the volume fraction of the elastomer raised to the 2.3–2.4 power for natural rubber with six different compatible resins. The exponent for styrene–butadiene rubber is 2.5–2.6 with four different resins. Using these relationships, both the tan δ peak temperature and plateau modulus can be predicted for a rubber–resin system from data on the unmodified elastomer and on one typical rubber–resin blend. 相似文献
12.
Toshiaki Matsunaga 《应用聚合物科学杂志》1977,21(10):2847-2854
The dispersion force component of surface free energy, γ, and the nondispersive interaction free energy between solid and water, I, were determined by the two-liquid contact-angle method, i.e., by the measurement of contact angles of water drops on plain solids in hydrocarbon, for commercialy available organic polymers such as nylons, halogenated vinyl polymers, polyesters, etc. A method to estimate the I values from the knowledge of the polymer composition is also proposed, on the basis of the assumption of the spherical monomer unit and the sum of interactions between functional groups and water molecules at the surface. 相似文献
13.
Alkali oxides added to methanol catalysts increase the formation of ethanol, n-propanol and isobutyl alcohol. This result has been known for many years, yet few quantitative studies have been reported in the literature. Data obtained on a commercial copper-zinc oxide catalyst promoted with K2 CO3 are presented and compared with published work. The optimum promoter concentration was about 0.5% by weight. The H2 to CO feed ratio was important in determining the higher alcohol selectivity. The rate of production of isobutyl alcohol varied as p p while for methanol, ethanol and n-propanol both exponents were positive and less than 1.6. Decreasing the hydrogen to carbon monoxide ratio from 2 to 0.5 more than doubled the isobutyl alcohol selectivity. Chain growth schemes predicting the higher alcohol selectivity are presented and estimates of the parameters are given. 相似文献
14.
M. Berghmans S. Govaers H. Berghmans F. C. De Schryver 《Polymer Engineering and Science》1992,32(20):1466-1470
A fluorescence technique is used to study the mechanism and dynamics of thermoreversible gel formation in concentrated polymer solutions. Two examples of these ordered structures were studied: isotactic polystyrene (iPS) in decalin and syndiotactic poly(methyl methacrylate) (sPMMA) in toluene. iPS can form two types of gels in decalin solutions. Turbid suspensions are formed between 60°C and 130°C. When the solution is quenched beneath 20°C, transparent gels are formed. In the former solution the polymer has a 31 helix structure; in the latter a 121 helix is formed. These structures formed by iPS in decalin solution have different fluorescence spectra. The ratio (Im/Ie) of the intensity of the monomer fluorescence band in the spectrum over the intensity of the excimer emission band is higher in the spectra of transparent gels. The formation of the transparent gels from a solution can be followed by plotting Im/Ie as a function of temperature. The kinetics of the gel formation are studied by following Im/Ie as a function of time at a fixed temperature. sPMMA forms gels in toluene by a mechanism called “conformational gelation.” This mechanism consists of two steps: a fast conformational change followed by a slower aggregation of polymer chains. Both steps were followed by measuring fluorescence of a pyrene label attached to the polymer. The fluorescence lifetime of this probe is sensitive to the polarity of the environment. When the polymer conformation goes from a random coil to an all trans conformation, the environment of the fluorescent label becomes increasingly richer in solvent. This change in polarity is reflected in a change in fluorescence lifetime. The change in fluorescence anisotropy of the label reflects the second step of the mechanism and correlates with the occurrence of chain aggregation. 相似文献
15.
Vinyl chloride–diallyl phthalate (VC–DAP) suspension copolymerization was carried out in a 5‐L autoclave and 200‐mL stainless steel vessel at 45°C. The apparent reactivity ratios of VC–DAP suspension copolymerization system were calculated as rVC = 0.77 and rDAP = 0.37. It shows that VC–DAP copolymer contains no gel when the feed concentration of DAP (f) is lower than a critical concentration (fcr, inside the range of 0.466–0.493 mmol/mol VC at 80–85% conversion), the polymerization degree (DP) of copolymer increases with the increase of f and conversion. VC–DAP copolymer is composed of gel and sol fractions when f is larger than fcr. The DP of sol fraction decreases as f increases, but the gel content and the crosslinking density of gel increase. The gel content also increases as conversion increases. The results also show that the index of polydispersity of molecular weight of sol changes with f, a maximum value appears when f is close to fcr. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 156–162, 2000 相似文献
16.
W. H. Tuminello 《Polymer Engineering and Science》1986,26(19):1339-1347
A method for determining the molecular weight distribution (MWD) of a polymer melt has been developed using the dynamic elastic modulus (G'), plateau modulus (G), and zero shear complex viscosity (η). The cumulative MWD was found to be proportional to a plot of (G'/G)0.5 vs. measurement frequency (ω). Frequency (ω) was found to be inversely proportional to (MW)3.4, as expected. Results were scaled to absolute values using the empirical relationship η ∝ (M?w)3.4, where M?w is the weight-average MW. M?w, M?n (number-average MW) and M?w/M?n calculated from melt measurements were found to agree with size exclusion chromatography usually well within 10 percent for broad and bimodal distribution samples. M?w/M?n tended to be approximately 20 percent higher for narrow distribution samples (M?w/M?n < 1.2) because we did not account for a finite distribution of relaxation times from a collection of monodisperse polymer chains. We also did not account for the plasticizing effect of short chains mixed with long ones which caused peak positions to be closer together for Theological vs, size exclusive chromatography (SEC) determinations of MW for bimodal distribution blends. 相似文献
17.
Hydrophobic microblock length effect on the interaction strength and binding capacity between a partially hydrolyzed microblock hydrophobically associating polyacrylamide terpolymer and surfactant
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Yongjun Guo Yan Liang Xueshan Yang Rusen Feng Rutong Song Jingda Zhou Feilong Gao 《应用聚合物科学杂志》2014,131(16)
Poly(acrylamide/sodium acrylate/N‐dodecyl acrylamide)s [poly(AM/NaAA/C12AM)s] with different hydrophobic microblock lengths (NH's) were prepared by the micellar copolymerization of acrylamide and sodium acrylate with a low amount of N‐dodecyl acrylamide (0.2 mol %), and the molecular structure was characterized by Fourier transform infrared spectroscopy, 1H‐NMR, and static light scattering. A combination of experiments involving viscosity measurement, fluorescence, and conductometry was applied to investigate the effect of NH on the interaction strength and binding capacity between poly(AM/NaAA/C12AM)s and C12H25SO4Na [sodium dodecyl sulfate (SDS)]. The viscosity, I3/I1 (the intensity ratio of the third vibrational band to the first band of pyrene molecules), and conductivity of the mixed system of copolymers with SDS all had different variation trends with the concentration of SDS. The binding capacity of the copolymers with SDS was calculated according to quantitative differences between the critical micelle concentration of the pure SDS solution and the mixed system. All of the results show that the interaction strength of SDS with the copolymers rose, and the binding capacity decreased with increasing NH. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40633. 相似文献
18.
Both pyrene-fluorescence probe and fluorescence label techniques are used to investigate the association behaviors of hyperbranched poly(sulfone-amine) (HPSA) in aqueous solution. In the presence of HPSA, excimer emission peak evidently appeared, while no excimer peak was observed in the emission spectra in the absence of HPSA. The excitation spectrum monitored at excimer emission red shifts by about 38-40 nm compared to that monitored at monomer emission, which shows that the excimer is formed by preassociated pyrene chromophores. In the same concentration of pyrene, monomer emission of pyrene decreases but excimer emission increases with increasing the concentration of HPSA; the ratio of excimer-to-monomer emission intensity (IE/IM) gradually increases, reaches a critical point at 5-7 g/l, and sharply increases with the concentration. Pyrene-labeled hyperbranched poly(sulfone-amine) (Py-HPSA) was synthesized from 4-(1-Pyrene)butyroyl chloride and HPSA. The monomer emission and excimer emission of Py-HPSA show the concentration-quenching effect, while IE/IM increases monotonously, approaches a critical point, and then suddenly increases with increasing the concentration of Py-HPSA. Influences of acidity and solvents on the fluorescence emission were studied. In high concentrations of hyperbranched polymer, pH and DMSO significantly influence the emission of pyrene, and excimer peak disappears at 72% of DMSO fraction. 相似文献
19.
Andrzej Wolff 《化学工程与技术》1990,13(1):277-288
The present paper is a case study of an application of sensitivity analysis in chemical kinetics. Emphasis is laid upon chemical interpretation of sensitivity information and on identification of the most important model important model parameters. The kinetic model for reforming of C6 hydrocarbons proposed by Mobil [14] is extended to the analysis of the behavior of n-hexane conversion in an adiabatic reactor. The importance of six initial conditions (feed composition and initial temperature) is analyzed by the computation of normalized first order sensitivity gradients (y/y) (δyi/δy). The relative importance of 21 model parameters αj is estimated by the computation of normalized sensitivity gradients of the type (αj/yi) (δyi/δαj). The influence of the decisive model parameters ΔH and ΔH (activation enthalpies of benzene hydrogenation and methyl cyclopentane isomerization, respectively) as well as operating parameters is presented. The problem of uncertainly in the value of ΔH and its influence on the model solution is also sown. Finally, some advantages of the application of normalized gradients of the explanation of process behavior are discussed. 相似文献
20.
Commercial high density polyethylene (HDPE), low density polythylene (LDPE), and linear low density polyethylene (LLDPE) resins were tested at 150, 170, and 190°C in steady state, dynamic, and extensional modes. Within the low rates of deformation \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω ≤ 0.3, the steady state and dynamic functions agreed: η = η′ and N1 = 2G′; at the higher rates, the steady state parameters were larger. The elongational viscosity, ηe, was measured under a constant rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, or stress, σ, condition. In the first case for LLDPE, the transient η reached an equilibrium plateau value, ηe. For HDPE, η increased up to the break point. For LDPE, stress hardening was recorded. Under constant stress the ηe, could always be determined; its value, within experimental error, agreed with the maximum value of η determined in a constant \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document} experiment. The maximum strain at break was only ε = 1.5 for HDPE and 3, to 4 for LDPE and LLDPE. The rate of deformation dependence of the η (or η′) and ηn may be discussed in terms of the Trouton ratio, RT = ηe/3η at \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω = \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document}: RT ≤ 1.2 for LLDPE, RT ≤ 2.5 for HDPE, and RT ≤ 15 for LDPE. The PE resins were extruded at 190°C through a laboratory extruder equipped with a slit or rod die. The rotational speed of the screw varied from 0 to 90 rpm. Extrusion pressure, output, and energy were measured and correlated with the rheological parameters of the resins. 相似文献