Preparation and characterization of cellulose acetate organic/inorganic hybrid films

A series of organic/inorganic hybrid (OIH) films were prepared using cellulose acetate (CA) as the organic component and tetraethyl orthosilicate (TEOS) as the inorganic component. The chemical, morphological, and mechanical properties of these films were evaluated with a variety of analytical techniques. The results of these evaluations showed that crosslinked CA OIH films were formed during the sol-gel reactions. The structure of OIH films was very sensitive to the CA/TEOS ratio and film formation conditions. All of the films with added TEOS were two phase on a molecular level, i.e., inorganic TEOS domains surrounded by a CA matrix. Under some film formation conditions the presence of TEOS, a nonsolvent for CA, led to solvent/nonsolvent phase separation on the micron scale. © 1995 John Wiley & Sons, Inc.     

Compostability of cellulose acetate films

Composting is an accelerated biological decay process viewed by many to be a potential solution to the solid-waste management crisis existing in many parts of the world. As part of a program to develop environmentally nonpersistent polymers that are compatible with a composting environment, we have developed a bench-scale compost methodology that emulates a high efficiency municipal windrow composting operation. A series of cellulose acetate films, differing in degree of substitution, were evaluated in this bench-scale system. In addition, commercially available biodegradable polymers such as poly(hydroxybutyrate-co-valerate) (PHBV) and polycaprolactone (PCL) were included as points of reference. Based on film disintegration and on film weight loss, cellulose acetates, having degrees of substitution less than approximately 2.20, compost at rates comparable to that of PHBV. NMR and GPC analyses of composted films indicate that low molecular weight fractions are removed preferentially from the more highly substituted and slower degrading cellulose acetates. © 1994 John Wiley & Sons, Inc.     

The chemistry of Pd in cellulose acetate

Pd(OAc)₂ complex has been incorporated in cellulose acetate (CA) as a dispersion medium using cosolvent (THF). The interactions Pd(II) complexes and cellulose acetate are examined by infrared spectroscopy and thermal analysis (DSC). The chemical reactivities of Pd–CA films have been investigated by reacting Pd sites with CO, H₂, O₂, and C₂H₄ in the temperature range 25–150°C and at the pressure of less than 1 atm. Two different Pd-carbonyls and a Pd(O)-hydride species formed in CA are characterized by their infrared spectra. Treatment of 10 wt % Pd–CA films with hydrogen (600 torr) at 70°C produces small Pd metal particles of ca. 30–60 Å in diameter in CA, which show catalytic activities under mild conditions in the reactions such as hydrogenation of C₂H₄ and oxidation of CO.     

Preparation of Rh-containing polycarbonate films and the study of their chemical properties in the polymer

RhCl[P(C₆H₅)₃]₃ complexes have been incorporated in polycarbonate (PC) as a dispersion medium using cosolvent (THF). The interactions between Rh(I) complexes and polycarbonate polymer molecules are studied by infrared spectroscopy and thermal analysis. The reaction chemistry of Rh in PC films has been investigated by reacting Rh sites in PC with small gaseous molecules like CO, H₂, D₂, O₂, NO, C₂H₂, and C₂H₄ in the temperature range 25∼150°C. Various Rh–carbonyls, –hydride, –nitrosyl, and –superoxo dioxygen species formed in PC films are characterized by infrared spectroscopy. The Rh complexes in PC are easily reduced by reacting them with H₂ gas and such reduction results in the formation of small Rh metal particles of 20∼30 Å in diameter in PC. The Rh complexes in PC show interesting catalytic reactivities such as hydrogenation of olefin and acetylene, oxidation of CO, reduction of NO, methanol synthesis from CO or CO_2, and oxidation of alcohol under relatively mild conditions.     

Isothermal transient current studies in cellulose acetate films

Step voltage transient current studies have been made in cellulose acetate films as a function of filed and thickness. A logarithmic plot (Scherr-Montroll plot) of the transient current vs. time gives a knee at a time t_T, which is interpreted as the transit time of the charge carrier. The value of the carrier mobility has been estimated to be 3.9 × 10^?9 cm².V^?1.S^?1 in cellulose acetate film. The carrier mobility in iodine-doped (2% w/w) cellulose acetate film has also been determined from Scher-Montroll plot and is found to be 3.3 × 10^?7 cm².V^?1.S^?1.     

Sorption of vapors and gases by cellulose acetate films

Cellulose diacetate and triacetate films 6–55 µm thick with a total porosity of 0.8–2% were prepared by pouring a solution on an immobile surface and by calendering. Sorption of H₂S and CO₂ gases and acetone vapors on these films was investigated in static and dynamic conditions. It was shown that films 6–10 µm thick prepared by calendering should be used for purification of air from H₂S and CO₂ and films 15–20 µm thick prepared by pouring should be used for removal of acetone vapors.Engels Institute of Technology, Saratov State University. Translated from Khimicheskie Volokna, No. 6, pp. 44–46, November–December, 1995.     

Dielectric behaviour of pure and nickel-doped cellulose acetate films

Pure and Ni (0·05%, 0·1% and 0·15%)-doped cellulose acetate (CA) films were formed on well-cleaned glass substrates using a solution growth technique. Metal–insulator–metal (MIM) sandwich structures of thin film capacitors were fabricated. Dielectric studies were carried out in the frequency range 1kHz to 10MHz in the temperature range 303–450K. The variation of capacitance and dielectric loss with temperature were studied at various frequencies. The variation of dielectric constants (ε′ and ε″) with frequency and temperature is discussed. An increase in capacitance with temperature was observed and this may be due to the chaotic oscillations of molecules in the polymer matrix. β (at lower temperature) and α (at higher temperature) relaxation loss peaks were observed. Doping results in the formation of charge transfer complexes/molecular aggregates in the polymer, which cause the shift of C_max value and the β and α relaxation loss peaks towards higher temperature. An appreciable dispersion of tan δ at lower frequency was noticed in all the samples studied. © 1998 SCI.     

Pyroelectric behaviour of solution-grown cellulose acetate polymer films

The pyroelectric behaviour of cellulose acetate polymer films was studied in a vacuum of 10^?3 torr under a polarizing field strength range of 6.25 × 10⁵–50 × 10⁵ V/m and a polarizing temperature range of 304–406 K. The pyroelectric coefficient exhibited abnormal behaviour, starting initially on the negative side and then changing sign from negative to positive. Negative coefficients are believed to be due to dipolar orientation, whereas space charge polarization is responsible for positive pyroelectric coefficients.     

秸秆醋酸纤维素的制备

农作物秸秆是自然界中数量极大的可再生资源,本研究以农作物秸秆为反应原料,采用无污染蒸汽爆破技术活化预处理,然后进行乙酰化反应,通过溶剂萃取分离并制备出高附加值的醋酸纤维素。实验结果表明：秸秆汽爆后明显增加了反应活性,制备醋酸纤维素的适宜条件是123℃,2 h,催化剂用量为7％,汽爆秸秆中性洗涤剂处理后的乙酰化结果效果最好,不同汽爆秸秆中小麦秸秆乙酰化效果最佳,优化实验条件下,秸秆醋酸纤维素聚合度均在120以上,取代度2.80以上,并且用红外图谱、1H NMR进行了表征。与目前工业上采用α-纤维素含量较高的高级浆为反应原料相比,不仅原料和预处理成本大大降低,而且工艺流程简单。     

氨基磺酸盐型水性醋酸纤维乳液的制备与性能

采用乙二胺基乙磺酸钠(AAS)作为亲水剂,在二月桂酸二丁基锡(DBTDL)的催化下,通过异佛尔酮二异氰酸酯(IPDI)将亲水基引入二醋酸纤维(CA)分子中,制得了一种氨基磺酸盐型水性醋酸纤维乳液(SWCA)。利用FTIR、DLS、黏度计、TEM、SEM、接触角测量仪、XRD、TGA,对SWCA结构及涂膜性能进行表征。考察了IPDI与AAS物质的量比对SWCA乳液粒径、黏度、涂膜表观形貌及耐水性的影响。结果表明:当n(IPDI)∶n(AAS)=1.1∶1时,乳液最稳定,微观形态呈水包油型(O/W)核壳结构,乳液粒径和分散系数(PDI)最小,分别为128nm和0.112,此时乳液表观黏度最大,为73.5m Pa·s,所成涂膜致密平整,接触角可达110.2°±2°,表现出明显的疏水性;此外,与二醋酸纤维相比,SWCA涂膜结晶性减弱,呈微晶态或次晶态结构,且具有较好的耐热性。     

Space charge limited currents in pure and iodinated cellulose acetate films

Current as a function of voltage has been studied in pure and iodine doped cellulose acetate in the temperature range 313–373 K. The space charge limited currents (SCLC) have been found to exist in pure and doped samples. The temperature dependence of conductivity is found to correspond to two activation energies. The activation energies calculated from conductivity vs. temperature plots for ohmic and SCLC regions were almost equal showing the extrinsic nature of conduction. The break point at 78°C in conductivity vs temperature plots for pure cellulose acetate may correspond to effective glass transition temperature (T′_g). This has been verified from the differential thermal analysis studies. The effect of iodine doping on the electrical conduction in cellulose acetate has been investigated and the results are reported. The infrared studies reveal that iodine stays in the polymer as a neutral molecule and some of which may interact with the polymer molecules.     

高吸水醋酸纤维素胶囊膜的制备

把醋酸纤维素制成胶囊膜，并将高吸水树脂封入胶囊中，制成高吸水醋酸纤维素胶囊膜，此膜可以用来浓缩水中的脲酶或悬浮微粒。     

Deacetylation behavior of binary blend films of cellulose acetate and various polymers

For binary blend films of cellulose acetate (CA) and various polymers, the elution behavior of the polymers from the CA films in different environments (i.e., soil, water) was examined. For the CA film containing poly(ethylene glycol) (PEG), the PEG eluted to the periphery of the film completely. On the other hand, polyvinylpyrrolidone blended with CA remained in the CA film. A CA film containing acrylic acid was prepared, and this film was heated. The elution of acrylic acid was inhibited by its polymerization. These results suggested that the internal polymers were capable of remaining in the CA film by polymer entanglement. Second, we examined the deacetylation and biodegradation behavior of CA films containing polymers with a phosphoric acid moiety in the side chain, such as poly(2‐hydroxyethyl methacrylate phosphoric acid ester) [poly(HEMA‐P)]. Poly(HEMA‐P) had the ability to deacetylate the CA, and the biodegradation rate of the CA films containing poly(HEMA‐P) increased in comparison with that of the nonadditive CA films. The elution of internal 2‐hydroxyethyl methacrylate phosphoric acid ester was inhibited by the copolymerization with 2‐hydroxyethyl methacrylate or crosslinking. In the case of both 2‐hydroxyethyl methacrylate phenyl phosphoric acid ester and 10‐methacryloyloxydecyl dihydrogen phosphate, the acetone‐soluble polymers were obtained by radical polymerization in a mixture of acetone and water. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1816–1823, 2006     

Deterioration behavior of cellulose acetate films in acidic or basic aqueous solutions

The deterioration behavior of cellulose acetate (CA) films (degree of substitution = 2.5) was examined in hydrochloric acid (HCl) and sodium hydroxide (NaOH) solutions of various concentrations to determine acid and base catalytic effects in heterogeneous systems at room temperature. With concentrations of 0.5N HCl and 0.01N NaOH and higher, the physical properties of the films changed. The films, recovered after 1–10 days of immersion, were slightly opaque and rubbery from swelling in the solutions before drying. They became brittle and shrank when they dried. For HCl immersion, the weight change of a film depended on the HCl concentration and the immersion time. With 6.0N HCl, the film shape was broken, and a fine powder was deposited in the solution with a recovery of 53.8 wt %. The infrared spectrum of this deposit indicated that it was completely deacetylated cellulose. For NaOH immersion, although the weight change depended on the NaOH concentration, the weight loss reached 40–50% within the first 24 h, and it was constant with respect to the immersion time and base concentration in 0.5N NaOH or NaOH of a higher concentration. The infrared and gel permeation chromatography analyses showed that this deterioration mainly depended on the deacetylation of CA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3354–3361, 2004     

Preparation and characterization of transparent cellulose films using an improved cellulose dissolution process

Effective dissolution of cellulosic macromolecules is the first predominant step to prepare functional bio‐based materials with desirable properties. In this study, we developed an improved dissolution process using a freeze‐drying pretreatment to promote the dissolution of cellulose. Rheological measurements of cellulose solutions and physicochemical characterization of regenerated cellulose films (scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis) were performed. Cellulose solution prepared from 5% microcrystalline cellulose (w:v) in the solvent exhibits a Newtonian fluid character while cellulose solutions at higher concentrations show a pseudo‐plastic fluid behavior. Results from physicochemical characterization indicate that a freeze‐drying pretreatment step of cellulose leads to a complete dissolution at 5% concentration while only part of cellulose is dissolved at 10% and 15% concentrations. The results obtained indicated that the use of a freeze‐drying pretreatment step under mild conditions lead to a complete dissolution of cellulose at 5% concentration. The cellulose films prepared from 5% concentration exhibited desirable properties such as good optical transparency, crystallinity, and thermal stability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44871.     

Preparation of gelatin-based films modified with nanocrystalline cellulose

Gelatin is a natural biological macromolecule derived from the collagen in the connective tissue of the skin, bone and other tissues. It has been widely used in medicine, food and industrial production and other fields for easy molding, excellent compatibility and biodegradability. However, physical and chemical disadvantages impede its further application, seriously. Therefore, modification of the gelatin films becomes more and more important. In this study, the gelatin/nanocrystalline cellulose (NCC) composite films were prepared by casting method with 4% glycerol as plasticizer. The effect of NCC on the properties of the composite films was investigated by the characterization of its morphology and mechanical, thermal, and optical properties and water adsorption. The results showed that mechanical, thermal stability and water absorption properties of the gelatin/NCC composite film were obviously improved. The composite films showed the highest tensile strength (13.56?±?0.25 MPa) when the mass concentration of NCC was 0.6%. Adding NCC to gelatin benefited the thermal stability of composite films. The gelatin/NCC composite film of 0.4% NCC had the highest melting transition temperature (138.9 °C). The composite films exhibited the lower water absorption (271.1%) when mass concentration of NCC was 1.0%. Thus, these results indicated that NCC could affect the properties of gelatin-based composite films, and showed it has potential for application in food packing.     

Preparation and release of avermectin‐loaded cellulose acetate ultrafinefibers

In this study, avermectin (AVM) was successfully dispersed in a cellulose acetate (CA) solution. CA/AVM composite fibers were fabricated by electrospinning the blending solution containing different amounts of AVM. Further investigation indicated that the composite fibers showed continuously changed morphologies with the concentration of AVM increasing. The electrospun fibers were characterized by field emission scanning electron microscope, X‐ray diffraction, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. The release behavior of the composite fibers was studied at pH = 7.4 and buffer media at 27°C and the amounts of AVM at different release steps were determined by high performance liquid chromatography analysis. Furthermore, AVM release from the CA/AVM samples showed two stages‐initial fast and later slow release. The two stages supplied a continuous release to achieve the effective utilization of AVM. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Preparation and properties of foamed cellulose acetate/polylactic acid blends

In order to improve the foaming performance of pure cellulose acetate (CA), blends were prepared by mixing polylactic acid (PLA) in CA and foamed by supercritical CO₂ (ScCO₂) in this study. The effect of PLA content (percentage by mass of blend) on structure, thermal properties, rheological properties, foaming properties and mechanical properties of the blends was investigated. The results showed that the addition of PLA destroyed the original hydrogen bonds of CA, while the blends had good crystallization properties. At the same time, compared with pure CA, the glass transition temperature (T_g) of the blends decreased, and the initial decomposition temperature (T₀) was reduced from 349.41°C (pure CA) to 334.68°C (CA/20%PLA). In addition, the rheological properties of the blends were improved, and the viscosity was reduced, which was obviously beneficial to foaming process. The pore size and density of the foamed blends both reached the maximum value at 20%PLA. The presence of PLA could degrade the mechanical properties of the blends. However, the overall drop (1.01 KJ/m²) of impact strength of the blends after foaming is much smaller than that before foaming (12.11 KJ/m²), indicating that the improvement of foaming performance was beneficial to improve its impact strength.     

Preparation and properties of films and fibers of disordered cellulose

The preparation and properties of films and fibers of highly disordered cellulose are described; the basis of the preparation is the regeneration of cellulose from cellulose derivatives in non-aqueous media. These cellulose are at least 97% hydrogen-bond disordered (as measured by the infrared-deuteration technique), give x-ray diagrams showing poor three-dimensional order, and are practically completely accessible to swelling agents such as water and formic acid. The crystallization of these disordered celluloses is described. The effects on native cellulose of ball milling, mercerization, amine treatment, swelling in acid and salt solutions, and swelling in solutions of potassium hydroxide in non-aqueous solvents are described with reference to changes in fine structure as measured by the infrared-deuteration technique.