Cellulose acetate/Research Development
Cellulose acetate extraction
Process for obtaining cellulose acetate from agricultural by-products by Biswas et al 2006 demonstrated yields of cellulose acetate from hemicellulose sugar depleted biomass. The study utilized a pretreatment to remove sugars and then an acetylation step followed by filtration to gather cellulose acetate. Feedstocks utilized were rice straw, wheat hull, and corn fibers and untreated and pretreated biomass were compared. The yield of the pretreated samples increase from 0.5, 1.8, 13.5% respectively to all around 25%. The value of cellulose acetate ~$2.00 is used to compare the cost of reagents. The pretreatment consists of milling followed by a hot hexane wash to remove oils. Corn fibers were then slurried 0.5% H2SO4 and pretreated in an autoclave at 121 C for 15 min, while rice hulls (15%, w/v) and wheat straw (8.6%, w/v) were slurried in 1% (v/v) H2SO4 separately and pretreated in an autoclave at 121 C for 1 h. Pretreated fibers were neutralized to pH 5.0 using 10 M NaOH. The solids were separated from the liquid, washed with water, and dried at 60 C for 24 hr for use in acetylation. Acetylation consisted of combining 2 grams of sample along with 0.5 g of acetic acid, 5.0 g of acetic anhydride, 30 ml of methylene chloride, and 0.04 g of sulfuric acid in a 100 ml round bottom ﬂask. The mixture was heated to 80 C with stirring for 4 hr under a reflux condensor. The mixture was cooled and sieved through a #60 filter. The remaining cellulose acetate was recovered from the residue with 60 ml chloroform and stirred for 30 minutes. The sample was filtered through Tyler #60 filter and the filtrate combined with the first filtrate.
Low degree substituted cellulose acetate
Cellulose/starch/glycerol thermomolded bioplastic
Additive Manufacturing of Cellulosic Materials with Robust Mechanics and Antimicrobial Functionality by Pattinson and Hart (2017) details 3D printing of a cellulose acetate (CA)/ acetone mixture. The cellulose acetate used had an average molecular weight of 30,000 - 50,000 and 39.7 wt. % acetyl groups. The optimal concentration of CA for 3D printing was 25–35 wt % and parameters for toolpaths are discussed. CA can be converted to cellulose by treatment with a base (sodium hydroxide). The technique requires rapid evaporation of the solvent.
Novel biorenewable composite of wood polysaccharide and polylactic acid for three dimensional printing by Xu et al (2018) prepared composites of PLA and hemicellulose by mixing with solvents (DMSO) and isolation for preparation of filament. Filaments could be used in 3D printing by melting.
PHYSICO-CHEMICAL CHARACTERIZATION OF SPRUCE GALACTOGLUCOMANNAN SOLUTIONS: STABILITY, SURFACE ACTIVITY AND RHEOLOGY by Xu et al (2007) describes isolation of galactoglucomannan (a type of hemicellulose) using filtration and and chemical treatments.
U.S. Patent 5,288,318 issued to Mayer et al on Feb 22 1994 details a biodegradable bioplastic made with 30-70% cellulose acetate (28-62 kDa, >2.2 degree of substitution), 10-60% raw starch, and 5-35% plasticizer (glycerol and its modified forms). High substitution numbers create a less biodegradable product and other anhydrides (besides acetate) may be used to increase durability. Starch can be formed into bioplastic polymers but is relatively high cost and unstable with water, mixing cellulose acetate and starch creates a biodegradable bioplastic with good strength and optical properties that is desirable for many applications. In this method a dry mixture of the cellulose acetate and starch bioplastic in pellet form is combined and the plasticizers added and mixed before extrusion at 100-170 C. Water content must be kept >4%. A number of other compounds can be included to improve certain product properties including shellac for water resistance, boric acid for fire resistance, and agricultural or mineral waste for fillers.
Reinforcement of Starch-based Biocomposite Film by Microcrystalline Cellulose from Corn Husk by Augustin et al (2009) examines the use of microcrystalline cellulose (MCC) as a reinforcement agent in a starch bioplastic. Microcrystalline cellulose is a purified partially depolymerized form of cellulose that was isolated by delignifying corn husks with alkaline pulping treatment and extraction using 30% v/v sulfuric acid at 60 C for 10 hr and room temperature for 14 hr with agitation. The suspension was centrifuged and the pellet washed with water until neutral. The MCC was sonicated and its characteristics measured with electron microscopy and a diffractometer. MCC yield was 9% and its crystallinity increased compared to the starting material to 72%. Starch bioplastic was prepared with a starch:glycerol:water weight ratio of 100:35:30 and MCC added at 3%, 5%, 10%, 15% (w/w) of the starch component. The mixture was compressed to form a final product. MCC increased tensile strength and elastic modulus, but high levels of cellulose acetate aggregate and formed cavities in the biocomposite. A 3% MCC showed the highest tensile strength and a high measure of elastic modulus.
Youtube demonstrations of simple starch based bioplastics
Cellulose acetate membranes
Water flux through cellulose triacetate films produced from heterogeneous acetylation of sugar cane bagasse by Fihlo et al (2000) produces cellulose triacetate from sugar cane bagasse and measures the movement of water through membranes of different thicknesses. Cellulose triacetate films with a high degree of crystallinity can be produce with heterogeneous acetylation are used in osmosis and reverse osmosis operations and a measure of their utility is the ability to move through the membrane. To measure the structure and properties of the product FT-IR, WAXES, DSC. FT-IR showed an absorption band located at around 1740 cm−1 which corresponds to the acetate's carbonyl. WAXES measurements showed acetylation treatment of 48 hours was necessary and produced multiple peaks corresponding to areas of semi-crystallinity and a distinguishing peak for cellulose at 8°. DSC measurements show the 48 hour acetylated sample has a higher enthalpy of fusion corresponding to 300 C, however the results are difficult to interpret because the authors question the literature stated value of the enthalpy of fusion of perfectly crystalline cellulose acetate. According to their value their sample is 62.5% crystalline. Water flux was measured using a suction cupped method and was found to be 50+/-2mm was (9.10+/-0.06)10−7 gs−1 cm−2 using a normalized graph of different thicknesses. Bagasse was purified using by combining 76.00 ml of 0.25M NaOH with 4.0 g of dried and ground bagasse at room temperature for 18 h. The sample was filtered and suspended in distilled water, then the pH was adjusted to 4.5–5.0 with HCl. The sample was filtered again, followed by addition of 76 ml of 4.2M ethylenediamine (EDA) was added and the pH was readjusted. The mixture was filtered again dried at room temperature. Then the sample was refluxed with 20% EtOH/HNO3 (v/v) for 3.0 h, with the EtOH/HNO3 mixture being changed every hour. Purified bagasse was washed with distilled water and dried at 105.
[http://pintassilgo2.ipen.br/biblioteca/2007/11910.pdf Water flux, DSC, and cytotoxicity characterization of membranes of cellulose acetate produced from sugar cane bagasse, using PEG 600] by Fihlo et al uses polyethylene glycol 600 as a pore forming additive to cellulose acetate films.
http://www.google.com/patents/US2487892 describes a method to acetylate cellulose sheets by passing them over a suction machine. The sheet is soaked by overhead spray and suction from below. The pretreatment is water followed by glacial acetic acid, and then treatment with catalyst and acetate anhydride.