Cellulose acetate, mechanical properties

Wibowo AC, Misra M, Park H-M, Drzal LT, Schalek R, Mohanty AK (2006) Biodegradable nanocomposites from cellulose acetate mechanical, morphological, and thermal properties. Compos A 37(9) 1428-1433... 

Polymer blends have been categorized as (1) compatible, exhibiting only a single Tg, (2) mechanically compatible, exhibiting the Tg values of each component but with superior mechanical properties, and (3) incompatible, exhibiting the unenhanced properties of phase-separated materials (8). Based on the mechanical properties, it has been suggested that PCL-cellulose acetate butyrate blends are compatible (8). Dynamic mechanical measurements of the Tg of PCL-polylactic acid blends indicate that the compatability may depend on the ratios employed (65). Both of these blends have been used to control the permeability of delivery systems (vide infra). 

The first major application of microfiltration membranes was for biological testing of water. This remains an important laboratory application in microbiology and biotechnology. For these applications the early cellulose acetate/cellulose nitrate phase separation membranes made by vapor-phase precipitation with water are still widely used. In the early 1960s and 1970s, a number of other membrane materials with improved mechanical properties and chemical stability were developed. These include polyacrylonitrile-poly(vinyl chloride) copolymers, poly(vinylidene fluoride), polysulfone, cellulose triacetate, and various nylons. Most cartridge filters use these membranes. More recently poly(tetrafluo-roethylene) membranes have come into use. 

To improve the thermal, mechanical, and viscoelastic properties of cellulose acetate butyrate, it was reinforced with nanocellulose crystals prepared from BC by acid hydrolysis. Using this nanosized cellulose (Sect. 1) a significant improvement in the properties of the composites was demonstrated [57]. 

The very wide range of the numerical values of the mechanical properties is evident. The modulus of organic polymer fibres varies between 1 and 350 GPa. The tenacities or tensile strengths may even vary from about 0.07 GPA (0.05 N/tex) for the weakest (cellulose acetate) to about 7 GPa (4 N/tex) for the strongest fibre (PIPD or M5 ) the compressive strengths reaches up to 1.7 GPa and the temperature resistance up to 400 °C. The ultimate elongation may vary from about 1% for the stiffest fibre (carbon) to about 600% for the most rubber-elastic. 

Abstract This article summarizes a large amount of work carried out in our laboratory on polysiloxane based Interpenetrating Polymer Networks (IPNs). First, a polydimethylsiloxane (PDMS) network has been combined with a cellulose acetate butyrate (CAB) network in order to improve its mechanical properties. Second, a PDMS network was combined with a fluorinated polymer network. Thanks to a perfect control of the respective rates of formation of each network it has been possible to avoid polymer phase separation during the IPN synthesis. Physicochemical analyses of these materials led to classify them as true IPNs according to Sperling s definition. In addition, synergy of the mechanical properties, on the one hand, and of the surface properties, on the other hand, was displayed. 

Guo, J.-H. Effects of plasticizers on water permeation and mechanical properties of cellulose acetate antiplasticization in slightly plasticized polymer film. Drug Dev. Ind. Pharm. 1993, 19 (13), 1541-1555. 

Williams RO, Wheatley TA, Liu J. Influence of plasticization and curing conditions on the mechanical properties of aqueous based cellulose acetate films. STP Pharma Set 1999 9(6) 545—553. 

The membrane material is important for cell attachment and growth. Common materials are polycarbonate, cellulose esters (acetate and nitrate) and PET (polyester). These materials sometimes need to be coated for cells to grow and differentiate. The different membrane materials have very different optical and mechanical properties, which must be considered when planning any experiment. 

The MF membranes are usually made from natural or synthetic polymers such as cellulose acetate (CA), polyvinylidene difiuoride, polyamides, polysulfone, polycarbonate, polypropylene, and polytetrafiuoroethylene (FIFE) (13). Some of the newer MF membranes are ceramic membranes based on alumina, membranes formed during the anodizing of aluminium, and carbon membrane. Glass is being used as a membrane material. Zirconium oxide can also be deposited onto a porous carbon tube. Sintered metal membranes are fabricated from stainless steel, silver, gold, platinum, and nickel, in disks and tubes. The properties of membrane materials are directly reflected in their end applications. Some criteria for their selection are mechanical strength, temperature resistance, chemical compatibility, hydrophobility, hydrophilicity, permeability, permselectivity and the cost of membrane material as well as manufacturing process. 

Changes during storage in the moisture permeability of cellulose acetate films used to effect controlled release (Fig. 173) were predicted from changes in mechanical properties of the films.705 The mechanical properties measured were relaxation time versus mechanical stress. 

---