CAB blends

R. Xiao, M. Li, S. Liao, G. Sun, Effect of rheological behaviors on the formation of fibrillar dispersed phases in the thermoplastic (TP)/ceUulose acetate butyrate (CAB) blends, in Proceedings of the Eiber Society 2009 Spring Conference, 2009, pp. 500-501. 

Fig. 41. Variation in glass-transition temperature with composition in PCL/CAB blends for (A) unquenched and (A) quenched samples, with a Fox equation fit for latter data taken from [58]...

For the 50 50 and 25 75 PCL/CAB blends, the latter group found double crystal-melting temperatures which were attributed to two populations of crystals arising from a morphological effect. It was also found that at low CAB (PCL>50 wt %) in as cast samples the Tj and AH for PCL were raised relative to those for pure PCL. This effect (which has been found in two other systems) was attributed to an improvement of crystal quality and increased lamellar thickness relative to those found for pure PCL. (This effect is inconsistent with melting point depression but the components are not miscible in the melt.) The effect, which was not explained, persisted after thermal cycling in blends with low CAB contents (20-30 wt %). 

Vazquez-Torres and Cruz-Ramos [121] also reported shear modulus and tan5 data for CAB blends samples were dried under vacuum for one week at 80 °C and were subsequently pressed into samples. Tg for pure CAB was at about 150 °C,in agreement with DSC data. Addition of PCL (25% and 50%) introduced two more relaxations. One was PCL melting at 50-60 °C and a larger peak at about 100 °C attributed to T for the blend. The T relaxation for CAB persisted... 

PCL/CAB blends, after heating, were examined by NMR and solubility tests. It was concluded that, under the heating cycle employed, no transesterification occurred which might have been responsible for the observed effects [121]. 

Vazquez-Torres and Cruz-Ramos studied blends of PCL with cellulose triacetate (CTA), cast from methylene chloride and dried for 48 h at 80 °C. No glass-transitions were observed and therefore no conclusions on polymer-polymer miscibility were drawn [121]. Double PCL melting peaks were seen and, in this case, the lower T j was the smaller, cf. CAB blends. Values of T j and AH of PCL were not increased by CTA. There was some evidence for CTA crystalHmty on heating to high temperatures in the differential scanning calorimeter [121]. 

Dave V, Glasser WG (1997) Cellulose-based fibers from Uquid crystalline solutions 5 Processing and morphology of CAB blends with Ugnin. Polymer 38 2121-2126... 

Dave, V., and Glasser, W.G. (1997) Cellulose-Based Fibres from Liquid Crystalline Solution.5. Processing and Morphology of CAB Blends with Lignin, Polymer, 38, 2121-2126. 

Blend water, ALS, ALES-4, Monateric CAB-LC, Monalux CAD-LC, Nonoxynol 10 and heat to 40-60C. Stir cool to 35-40C and adjust pH to 6-6.5 with 50% citric acid. 

As an impressive phase study, it was observed that a blend system composed of CAB having 54 mol % butyryl side groups and polyfethylene oxide) (PEO Mn = 35 000) yielded a phase diagram with a lower critical solution temperature (LCST) boundary, and a cloud point of 168 °C at the critical composition of CAB/PEO = 40/60 (w/w) [112]. 

There have been many related works by other research groups that are concerned with the phase behavior, isothermal crystallization kinetics, and tensile properties of cellulose propionate (DS = 2.75)/PHB blends [129], the miscibility and crystallization behavior of CAB/PHB blends [ 130], or the melt... 

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]. 

Blending is a logarithmic function and, as an example shown in Figure 5, CAB-381-20 (Ester "A"), which has an ASTM viscosity of 20 s, may be blended with CAB-381-2 (Ester "B") having a 2-s viscosity, and a 40/60 weight ratio to obtain an effective viscosity range of 5 s. 

In this application, the CAB is dissolved at 25% solids in an 80/20 toluene/ethyl alcohol blend before addition to the enamel. 

Cellulose butyrate contains the bulkier butyryl group these esters are more compatible and soluble than acetates, but are too soft for most coating applications. Cellulose esterified with blends of alkyl groups can provide many intermediate properties needed in coatings. Selection of the appropriate cellulose acetate butyrate [9004-36-8] (CAB) and cellulose acetate propionate [9004-39-f] (CAP) content must be based on specific application requirements. 

CAB Cellulose acetate-butyrate ECB Ethylene copolymer blends... 

Nanofiltration (NF) (TFCP), cellulose acetate blend (CAB), cellulose triacetate (CTA) TFCP 10-30 A flow Preferential sorption-capillary osmotic pressure Net applied pressure in excess over the... 

In the woik of Olde Riekerink et al. (2002), one type of UF (cellulose triacetate, CTA) membrane and one type of RO (cellulose acetate blend, CAB) membrane were selected for CO2 plasma modification. CTA ultrafilters are well known for their low fouling properties and CAB membranes are widely used for desalination. CO2 plasma treatment resulted in the gradual etching of the membrane s dense top layer. 

Fig. 10.46 FTIR spectra of Pure PMMA and blend of PMMA/CAB of 50/50 composition (Meaurio et al. 2005)...

Table 14. Peak temperatures for tan5 data in blends of PCL with CAB data taken from [121]...

WAXS data for as-cast blends showed that crystal melting peaks for PCL (relative to PCL contents) were nearly constant there was a small increase in crystallinity on addition of CAB in line with DSC data. On thermal cycling to 237 °C there was a massive loss of PCL crystallinity as solvent history was lost and the blend took on its own properties, consistent with DSC and differential thermal analysis data. It was noted that in as-cast blends one of the crystal diffraction peaks decreased in relative intensity. This effect was attributed (possibly) to distortion of unit cell dimensions, an effect found elsewhere in paracrystalUne materials. 

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