Cellulose derivatives, miscibility

E. Kiran and H. Pohler, Alternative solvents for cellulose derivatives Miscibility and density of cellulosic polymers in carbon dioxide + acetone and carbon dioxide + ethanol binary fluid mixtures, J. Supercrit. Fluids, 13, 135-147 (1998). 

Miscibility of Polymers in Binary Fluid Mixtures. Cellulose Derivatives. Miscibility of cellulose derivatives in binary fluid mixtures of carbon dioxide is of recent interest because of the significance of these polymers in controlled-release drug formulations, and also because of the traditional significance of cellulose based polymers as film or fiber... 

Some cellulose derivatives and P(3HB) and P(3HB-co-3HV) have been found to show good compatibility [114-116]. These are chemically modified natural and natural biodegradable polymer blend systems. Blends obtained by melts compounding P(3HB) with cellulose acetate butyrate (CAB, degrees of butyrate and acetate substitution are 2.50 and 0.18, respectively) have been found to be miscible over the whole composition range by DSC and dynamic mechanical spectroscopy [116]. 

Cyclohe.xanol [108-93-0] has a camphor-like odor with a water solubility of 2%. It is miscible with other solvents and dissolves fats, oils, waxes, and bitumen, but not cellulose derivatives. 

Dioxane [123-91-1] has a slight odor reminiscent of butanol, and is miscible with water and organic solvents. It is a good solvent for cellulose derivatives, polymers, chlorinated rubber, and resins [14.272],... 

The properties of n-propyl acetate are, approximately, intermediate between those of ethyl and n-butyl acetates. It is miscible with alcohols, ketones, esters, oils and hydrocarbons and is a good solvent for nitrocellulose and a wide range of cellulose derivatives, especially when It is admixed with the aromatic hydrocarbons or the lower aliphatic alcohols. 

As a polyester, PHB can partake in many of the hydrogen-bonding type of specific interactions with other functional additives that lead to partial miscibility and compatibility. For example, the miscibility of polyesters with chlorinated polymers, polyamides, polycarbonates, cellulose derivatives and other functional polymers is well documented,and PHB is no exception to this general observation. However, these interactions are dominated by the tendency to self-crystallize with exclusion of the additive to the amorphous phase. For example, an 80/20 melt compounded and injection-moulded sample of PVC/PHB polyblend appears initially to be exceptionally tough with the PHB acting as a polymeric plasticizer. The presence of the PVC retards but does not stop crystallization of the PHB at room temperature and the material eventually becomes brittle. Under extreme circumstances, the PHB phase can actually achieve almost 100% crystallinity within the blend, as determined by X-ray analysis and DSC. Thus, plasticized formulations and polyblends involving PHB itself are limited to relatively low levels of additive because only the minor amorphous phase of the biopolymer is involved in the interaction. Even so, some plasticizers have been proposed for PHB. ... 

This indicated that the NR/cellulose derivative blends were partially miscible only under experimental conditions. ... 

Plasticizers are organic substances of low volatility that are miscible with polymers. They increase flow and thermoplasticity of plastic materials by decreasing the viscosity of polymer melts, the glass transition temperature (Tg), and the elasticity modulus of finished products. Plasticizers are used only with a limited number of polymers, the most important being poly(vinyl chloride) (PVC) and its copolymers (80% by weight [1]), cellulose derivatives, poly(vinyl acetate) (PVA), poly(vinyl alcohol) (PVAL), and natural and synthetic rubbers. 

Many drop stabilizers in suspension polymerization are water-miscible polymers. These materials are sometimes called protective colloids. They include naturally occurring substances, such as gelatin and pectin, and a wide range of synthetic polymers such as partially hydrolyzed poly(vinyl acetate)s. Modified natural products such as cellulose ether derivatives are also widely used. Munzer and Trommsdorff provide a detailed list of patented stabilizers [1]. Polymeric stabilizers do not all act in the same way but steric effects are often important [16]. Although transfer of stabilizer molecules from the continuous phase to the drop surfaces can sometimes be fast, the development of drop stability may be slow [17]. That may arise because rearrangement of stabilizer molecules on the drop surface is necessary. Water-miscible polymers are not expected to be good drop stabilizers when the continuous phase is nonaqueous (see Section 5.5). 

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