Cellulose Triacetate Films Research Articles

Design of birefringence and its wavelength dispersion for cellulose derivatives using substitution, low-mass additives, and porous structures

Birefringence and its wavelength dependence are important properties for optical applications, such as liquid crystal displays and pick-up lenses. Cellulose esters, which are eco-friendly materials from biomass resources, have been used in optical materials due to their transparency and heat resistance. This review summarized our recent works on birefringence control of cellulose esters by substitution of multiple ester groups, addition of low-mass molecules, and formation of a porous structure. Cellulose acetate propionate (CAP), which has acetyl and propionyl groups in a pyranose unit, exhibited positive birefringence with extraordinary wavelength dispersion owing to contributions from its two esters, while cellulose triacetate (CTA) showed negative birefringence with ordinary dispersion. Moreover, the effect of substitution sites (C-2, C-3, and C-6) on birefringence and its wavelength dependence was investigated by comparing birefringence data of CTA and xylan acetate. The addition of low-mass molecules improved the value of birefringence due to the intermolecular orientation correlation with the matrix cellulose esters. The anisotropic porous structure in CTA films, which was prepared by thermoinduced phase separation, generated extraordinary wavelength dispersion of birefringence. We successfully controlled birefringence and its wavelength dispersion of cellulose esters by choosing different ester substitution groups and sites, controlling the orientation of the crystal, adding low-mass molecules, and forming microscale porous structures. The substitution of two ester groups could provide extraordinary wavelength dispersion of birefringence, which is important for wide-range retardation films. The low-mass additives enhance birefringence values due to the intermolecular orientation correlation with matrix cellulose esters. The anisotropic microporous structure produced by thermoinduced phase separation generates form birefringence, which improves the total birefringence of cellulose esters.

A study on beam profile of an industrial electron accelerator

ABSTRACTExperimental evaluation of electron beam profile of a recently upgraded industrial electron accelerator has been carried out to study characteristics of the beam required for the irradiation of various industrial products. Calibrated cellulose triacetate (CTA) film strip dosimeters were used for the measurement of dose profile along and transverse to the scanning direction at different distances in air under the beam extraction window in dynamic (conveyor) and static mode of operation. Two-dimensional dose distribution mapping under the beam has also been measured by using a large number of CTA strip dosimeters. The obtained result shows that the electron beam emerging out from scanning horn has a good uniformity along the scanning direction within 90% of the average maximum dose. Also, the paper reports depth dose distribution in unit density material under the 4.5 MeV beam. Using this study, area affecting dose to the product is controlled within the limit for the irradiation.

Oil-Water Separation of Electrospun Cellulose Triacetate Nanofiber Membranes Modified by Electrophoretically Deposited TiO₂/Graphene Oxide.

Recycled waste industrial cellulose triacetate (TAC) film, which is one of the key materials in polarizers, was used to produce nanofiber membranes by electrospinning and synergistic assembly with graphene oxide (GO) and titanium dioxide (TiO2) for oil-water separation. In this study, GO and TiO2 coated by an electrophoretic deposition method introduced super hydrophilicity onto the recycled TAC (rTAC) membrane, with enhanced water permeability. The results indicate that when the outermost TiO2 layer of an asymmetric composite fiber membrane is exposed to ultraviolet irradiation; the hydrophilicity of the hydrophilic layer is more effectively promoted. Moreover, this coating could efficiently repel oil, and demonstrated robust self-cleaning performance during the cycle test, with the aid of the photocatalytic properties of TiO2. The rTAC membrane of networked hydrophobic fibers could also increase the speed of the filtrate flow and the water flux of the oil-water emulsion. The permeate carbon concentration in the water was analyzed using a total organic carbon analyzer. Incorporation of TiO2/GO onto the rTAC membrane contributed greatly towards enhanced membrane hydrophilicity and antifouling performance. Therefore, the novel TiO2/GO/rTAC asymmetric composite fiber has promise for applications in oil-water separation.

Water/salt transport properties of organic/inorganic hybrid films based on cellulose triacetate

The synergized optimization of water flux and salt rejection by blending with inorganic fillers has been achieved for the polyamide (PA) thin film nanocomposite (TFN) membrane. However, it is difficult to characterize its mass transport properties due to the very thin and heterogeneous PA film. In this work, we select cellulose triacetate (CTA) as the base to prepare hybrid films and their transport properties were studied according to solution-diffusion theory. A series of inorganic fillers, such as reduced graphene oxide (RGO), zeolites, ZIF-8, SiO2 and graphene oxide (GO) were incorporated. The SEM and EDX results indicate a less than 1 wt% filler content for a uniform dispersion. The blending of inorganic fillers leads to enhanced glass transition temperature (Tg) and density, little effect on the water transport property but dramatically decreased salt permeability values, which are nearly ten-fold of that of the CTA film. The blending of GO can densify and hydrophilize CTA simultaneously, which is most promising for a desalination application. The increased water uptake should contribute to its increased water permeability, while the decreased free volume size and FFV value and various interactions between the ions (Na+, Cl-) and GO sheets account for salt permeability decrease.

Analysis of molecular interaction using a pulse-induced ring-down compression ATR-DIRLD step-scan time resolved spectroscopy/2D-IR

A rheo-optical method, based on pulsed compression ATR dynamic infrared linear dichroism (DIRLD) step scan time-resolved-FT-IR/2D-IR spectroscopy, is further improved. By inserting a tungsten carbide block with massive weight between a film sample and a piezo electric actuator, a ring-down response was successfully generated according to the inertial effect. The improved method is used to analyze molecular interactions in cellulose acetate propionate (CAP) films including tricresyl-phosphate (TCP), as compared with cellulose triacetate (CTA) films with the TCP case. The result suggests that the existence of molecular interaction among propionyl groups in the CAP, the TCP's Methyl, and phenyl rings, which is not observed in the CTA-TCP system.

Dual Function of Cellulose Triacetate–Graft–Polymethacrylic Acid Films for Dyes Removal and for High-Dose Radiation Dosimetry

Graft copolymerization of methacrylic acid (MAc) onto cellulose triacetate (CTA) films was conducted by gamma rays. The grafting conditions were optimized. The structure of grafted CTA films was characterized by Fourier transform infra red–attenuated total reflection, scanning electron microscopy, thermal gravimetric analysis, CHNS/O microanalyzer and, surface area and porosity analyzer. The grafted CTA films were exploited in adsorption of ethyl violet (EV) and phenol red (PR) dyes. The adsorption capacity of the grafted CTA films was investigated at various variables. The adsorption isotherms and kinetic study were examined. Further, the dyed grafted CTA films were used in measurements of high dose radiation. The results indicate that the useful dose range extents up to 440 and 300 kGy for EV and PR, respectively. The effects of relative humidity during irradiation, shelf-life, pre- and post-irradiation storage in dark and indirect daylight conditions on dosimeters performance were investigated.

Preparation and characterization of microporous cellulose acetate films using breath figure method by spin coating technique

This work reports the preparation and characterization of microporous cellulose triacetate films. Cellulose triacetates were obtained from homogeneous acetylation of cellulose extracted from wood by an effective method totally free of chlorine. The microporous films were produced by breath figure method by spin coating technique. In the breath figure method, the formation of the pores in the polymer films involves the phenomenon of condensation of water vapor on a polymer solution surface, so that the condensed water droplets act as a template for formation pores. The porous films were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films showed pores with rounded morphology and the pore diameter ranged from 0.1 to 0.5 µm. The effects of the solvent, concentration of the polymer solution and polymer molecular weight were investigated on the formation, morphology and size of the pores. Large porous structures are observed when lower polymer concentrations and higher molecular weight are used. Higher pore densities were observed when dichloromethane was used as solvent. The films produced could be used as biomaterials such as cell culture substrate or in sensing devices. From the results obtained in this work it is possible to predict the pore depth, size and density in cellulose triacetate films, allowing the manipulation of these parameters for future desired applications.

Tea: An Alternative Adsorbent for the Preservation of Cellulose Triacetate Film

Cellulose triacetate (CTA) film, the main film base of the Twentieth Century, is inherently unstable, affected by autocatalytic deterioration through hydrolysis. The release of, and subsequent exposure to, acetic acid known as ‘vinegar syndrome’ accelerates deterioration, placing all cellulose acetate materials at risk or actively deteriorating. Preservation techniques rely on cold storage to slow deterioration or microenvironments with adsorbent materials to remove corrosives and/or pollutants. However, commercially available adsorbents can be expensive and difficult to access. This research investigated the potential for tea and tea waste to act as an alternative, low cost, accessible adsorbent for the preservation of CTA film. Adsorption capabilities of various tea varieties and treatments were compared with activated charcoal, silica gel and molecular sieves. Testing established tea as an effective adsorbent of water and acetic acid vapour, with an aversion to adsorption of the plasticiser dibutyl-phthalate. Use of tea waste also involves additional cost, sustainability and accessibility benefits along with lessened corrosive potential. These findings support tea as a potentially viable alternative adsorbent for the preservation of CTA film, requiring further research into optimum application systems.

Interfacial layer thickness design for exploiting the reinforcement potential of nanocellulose in cellulose triacetate matrix

The contribution of the interfacial layer thickness to composite properties was investigated using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofiber (TOCN) and cellulose triacetate (CTA). To control the interfacial layer thickness, the surface of the TOCNs was modified by grafting amine-terminated poly(ethylene glycol) (PEG-NH2) with different molecular weights. Neat TOCNs or PEG-grafted TOCNs were compounded with CTA to prepare nanocomposite films with different interfacial layer thicknesses. We demonstrated that thinner interfacial layers enhanced the stiffness of the nanocomposite films, whereas thicker interfacial layers enhanced their ductility. The high transparency and low birefringence of the CTA films were preserved even with the addition of TOCNs or PEG-grafted TOCNs. Although the thermal expansion of the nanocomposite films was suppressed by TOCN addition, the presence of PEG layers on the TOCN surfaces had a negative impact on their restraint of the thermal expansion. These results suggest that the interfacial layer thickness plays an important role in the mechanical and thermal properties of nanocellulose-reinforced composites.

Transparent nanostructured cellulose acetate films based on the self assembly of PEO-b-PPO-b-PEO block copolymer

In this study fabrication and characterization of transparent nanostructured composite films based on cellulose triacetate (CTA) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (EPE) triblock copolymer were presented. The effect of the addition of EPE triblock copolymer on the thermal stability, morphology, and mechanical properties of cellulose triacetate films was investigated. The triblock EPE was chosen since PEO blocks interact favorably with CTA, whereas, PPO blocks remain immiscible which provokes a microphase separation. This allows to obtain EPE/CTA composite films with ordered microphase-separated structures where PPO spherical microdomains are well-dispersed in PEO/CTA matrix by simple solvent-evaporation process. During this process, PEO block chains selectively interact with CTA by strong interpolymer hydrogen-bonding while PPO block microseparated. The addition even 40wt% of EPE leads to nanostructured EPE/CTA composite. The cytotoxicity assay of CTA and EPE/CTA composite films confirm non-toxic character of designed transparent nanostructured composites based on sustainable matrices.

Oligo- and Polyfluorenes Meet Cellulose Alkyl Esters: Retention, Inversion, and Racemization of Circularly Polarized Luminescence (CPL) and Circular Dichroism (CD) via Intermolecular C–H/O═C Interactions

Detecting chiral/helical interactions among noncharged molecules and polymers is difficult due to their unlimited intra- and intermolecular rotational freedom. To clarify the chirality and/or helicity transfer from a chiral polymer to noncharged achiral molecules, we chose stiff cellulose triacetate (CTA) and cellulose acetate butyrate (CABu) as nonchromophoric helical/chiral polymers. Here, we highlighted stiff 9,9-dialkylfluorene oligomers and polymers (repeating number n = 1, 2, 3, 5, 7, 47, 201) as achiral chromophoric luminophores. These fluorenes revealed clear circularly polarized luminescence (CPL) and bisignate circular dichroism (CD) signals when embedded into CTA and CABu films. In the ground state, when n = 1–7, CTA and CABu commonly induced (+)-CD signals, whereas when n ≥ 47, they induced (+)- and (−)-CD signs, respectively. In the photoexcited state, when n ≥ 3, CTA and CABu induced (+)- and (−)-CPL signs, respectively. Upon comparing the ground and photoexcited states, when n = 2–7, CABu i...

Practical considerations for operability of an 8″ spiral wound forward osmosis module: Hydrodynamics, fouling behaviour and cleaning strategy

A better understanding of large spiral wound forward osmosis (SW FO) module operation is needed to provide practical insight for a full-scale FO practical implementation desalination plant. Therefore, this study investigated two different 8″ SW FO modules (i.e. cellulose tri acetate, CTA and thin film composite, TFC) in terms of hydrodynamics, operating pressure, water and solute fluxes, fouling behaviour and cleaning strategy. For both modules, a significantly lower flow rate was required in the draw channel than in the feed channel due to important pressure-drop in the draw channel and was a particularly critical operating challenge in the CTA module when permeate spacers are used. Under FO and pressure assisted osmosis (PAO, up to 2.5bar) operations, the TFC module featured higher water flux and lower reverse salt flux than the CTA module. For both modules, fouling tests demonstrated that feed inlet pressure was more sensitive to foulant deposition than the flux, thus confirming that FO fouling deposition occurs in the feed channel rather than on the membrane surface. Osmotic backwash combined with physical cleaning used in this study confirmed to be effective and adapted to large-scale FO module operation.

Cellulose triacetate films obtained from sugarcane bagasse: Evaluation as coating and mucoadhesive material for drug delivery systems

Cellulose triacetate (CTA) films were produced from cellulose extracted from sugarcane bagasse. The films were characterized using scanning electron microscopy (SEM), water vapor permeability (WVP), mechanical properties (MP), enzymatic digestion (ED), and mucoadhesive properties evaluation (MPE). WVP showed that more concentrated films have higher values; asymmetric films had higher values than symmetric films. MP showed that symmetric membranes are more resistant than asymmetric ones. All films presented high mucoadhesiveness. From the WVP and MP results, a symmetric membrane with 6.5% CTA was selected for the coating of gellan gum (GG) particles incorporating ketoprofen (KET). Thermogravimetric analysis (TGA) showed that the CTA coating does not influence the thermal stability of the particles. Coated particles released 100% of the KET in 24h, while uncoated particles released the same amount in 4h. The results highlight the CTA potential in the development of new controlled oral delivery systems.

Cellulose triacetate doped with ionic liquids for membrane gas separation

Cellulose triacetate (CTA) is a workhorse polymeric membrane material for industrial CO2/CH4 separation. This study investigates the doping of CTA with ionic liquids (ILs) to reduce the crystallinity of the CTA and enhance its affinity with CO2, thus increasing CO2 permeability and CO2/light gas selectivity. CTA films doped with 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) and 1-ethyl-3-methylimidazolium dicyanamide ([emim][dca]) were prepared; and the effect of IL loading on properties of the CTA, such as crystallinity, density, degradation temperature, glass transition temperature, and gas transport properties, were determined. The IL doping reduces the glass transition temperature and degree of crystallinity of CTA, increasing gas diffusivity and permeability. The IL doping also increases CO2/CH4 solubility selectivity and CO2/N2 permeability selectivity, due to the affinity of these ILs with CO2, compared to light gases such as CH4 and N2. This study demonstrates a promising route in manipulating the morphology and gas transport properties of semi-crystalline polymers by doping with ILs.

Dosimetry Commissioning of Tunisian Electron Beam Accelerator

The Tunisian Beta irradiation facility (LINAC, CIRCE III) has been put into operation at the end of 2009. Such facility is designed essentially for sterilization of medical devices and conservation of foodstuff. The delivery and validation of a specified dose are key concerns of operators of electron beam irradiation facilities. In order to adjust the treatment conditions and to control the optimal operation of the accelerator, it is necessary to evaluate the absorbed dose and its distribution within material in the radiation field. Consequently, aspects from installation qualification to operation qualification are described together with the associated process variables. Technical parameters that directly influence the absorbed dose distribution in the product were examined by dosimetric measurements and compared to the data specified by the facility manufacturer. Two dosimeter types were used for measurements: radiochromic B3 and cellulose triacetate films.

Effect of acetylation site on orientation birefringence of cellulose triacetate

The effect of a substitution site on orientation birefringence for cellulose triacetate (CTA) was investigated by the addition of xylan ester. Since CTA has three substitution sites (C-2, C-3, and C-6) while xylan ester has two substitution sites (C-2 and C-3), the change of birefringence by xylan acetate (XylAc) is attributed to the contribution of the C-6 acetyl group. Dynamic mechanical analysis and thermal measurements showed a single glass transition peak, indicating that XylAc is miscible with CTA at any compositions. The orientation birefringence (Δn) of CTA/XylAc films stretched beyond the glass transition temperature increased with increasing the XylAc content. The result for the stretched film suggested that the contribution of acetyl group in the C-2 and C-3 sites to Δn is positive while that in the C-6 is negative. The negative sign for the C-6 site is in agreement with the result simulated by using the molecular dynamics method. In addition, Δn of CTA films containing xylan propionate (or butyrate) indicated that the propionyl and butyryl groups in the C-2 and C-3 sites show positive birefringence similar to the acetyl group.

31.1: Evolution of Cellulose Triacetate (TAC) Films for LCDs: Novel Technologies for High Hardness, Durability, and Dimensional Stability

We have successfully developed two types of cellulose triacetate (TAC) polarizer protection films that meet the LCDs trends toward thinner and larger panels. The novel 25µm TAC film, which has high‐hardness and high‐durability, solves the problems caused by the reduction in the thickness of polarizers and is suitable for small‐sized LCDs. The novel Z‐TAC film, which has high‐dimensional‐stability, reduces warpage of large sized IPS‐TVs.

Low-birefringent and highly tough nanocellulose-reinforced cellulose triacetate.

Improvement of the mechanical and thermal properties of cellulose triacetate (CTA) films is required without sacrificing their optical properties. Here, poly(ethylene glycol) (PEG)-grafted cellulose nanofibril/CTA nanocomposite films were fabricated by casting and drying methods. The cellulose nanofibrils were prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and amine-terminated PEG chains were grafted onto the surfaces of the TEMPO-oxidized cellulose nanofibrils (TOCNs) by ionic bonds. Because of the nanosize effect of TOCNs with a uniform width of ∼3 nm, the PEG-TOCN/CTA nanocomposite films had high transparency and low birefringence. The grafted PEG chains enhanced the filler-matrix interactions and crystallization of matrix CTA molecules, resulting in the Young's modulus and toughness of CTA film being significantly improved by PEG-grafted TOCN addition. The coefficient of thermal expansion of the original CTA film was mostly preserved even with the addition of PEG-grafted TOCNs. These results suggest that PEG-TOCNs are applicable to the reinforcement for transparent optical films.

Nature of chromogens of protonated azobenzene

Changes in the absorption spectra of azobenzene in UV-Vis light are studied with respect to its protonation in sulfuric acid solutions and interaction with gaseous HCl in cellulose triacetate films. In both processes, the emergence of an intense orange color is shown to represent the electronic structure of forming monocations where the positive charge of NH+ groups shifts electrons from the o- and p-positions of Nphfragment phenyls. It was found that the charge distribution and color was the same as observed for the cations of the benzyl and phenylaminyl types. The mechanism of azobenzene monocation photocyclization in sulfuric acid is presented, and the origin of the red color of azobenzene dications formed in oleum is explained.

Development of microporous structure and its application to optical film for cellulose triacetate containing diisodecyl adipate.

Phase separation in plasticized cellulose triacetate (CTA) films is investigated to produce a microporous film that can be used in optical devices. Hot-stretched CTA films containing diisodecyl adipate (DIDA) show negative orientation birefringence similar to the hot-stretched pure CTA. After extracting DIDA from the stretched films by immersion into an organic solvent, however, the films exhibit positive birefringence. Moreover, the magnitude of the birefringence increases with the wavelength, known as extraordinary dispersion, which is an essential property in the preparation of an ideal quarter-wave plate. Numerous ellipsoidal pores with micro-scale were detected in the film after the immersion, indicating that DIDA were segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. These results indicate that extraordinary wavelength dispersion is given by the combinations of orientation birefringence from CTA and form birefringence from micropores. Furthermore, it was found that annealing time and stretching condition affect the phase separation as well as the shape and size of pores.