Preparation of polyester nanofibers and nanofiber yarns from polyester/cellulose acetate butyrate immiscible polymer blends

Development of high throughput production processes for making thermoplastic nanofiber and nanofiber yarns are urgently needed. PET, PTT, and PBT nanofibers were prepared from PET/CAB, PTT/CAB, PBT/CAB immiscible polymer blends by in situ microfibrillar formation during the melt extruding process. The diameter distribution and crystallization properties of PET, PTT, and PBT nanofibers were analyzed. After removing the CAB matrix phase, the nanofibers could be collected in the forms of random or aligned nanofibers and nanofiber bundles or yarns. To understand the formation mechanism of the nanofibers, the morphology development of three different polyesters in the dispersed phase were studied with samples collected at different zones in a twin‐screw extruder. The morphological development mechanism of the dispersed phases involved the formation of sheets, holes and network structures, then the size reduction and formation of nanofibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Formation and morphology development of poly(butylene terephthalate) nanofibers from poly(butylene terephthalate)/cellulose acetate butyrate immiscible blends

Nano‐scale poly(butylene terephthalate) (PBT) fibers were prepared from PBT/cellulose acetate butyrate (CAB) immiscible polymer blends due to in situ microfibrillar formation during a melt extruding process. The morphological development of the dispersed phase was studied with samples collected at different zones in a twin screw extruder. It was found that the holistic developmental trends of PBT dispersed phase were nearly the same. Fibers began to form even under the shear flow of the twin‐screw extruder. The morphology developmental mechanism of the dispersed phase involved the formation of sheets, holes and network structures, then the size reduction and formation of nanofibers. The effect of viscosity ratio, blend ratio, and shear rate on the morphology evolution was also studied by analyzing the shape and size distribution of the samples. The diameter distribution of the nanofibers could be affected by viscosity ratio, blend ratio, and shear rate. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Improved fracture toughness of immiscible polypropylene/ethylene-co-vinyl acetate blends with multiwalled carbon nanotubes

Functionalized multiwalled carbon nanotubes (f-MWCNTs) have been introduced into immiscible polypropylene/ethylene-co-vinyl acetate (PP/EVA) blends. Two different compositions, one (PP/EVA = 80/20) exhibits the typical sea-island morphology and the other (PP/EVA = 60/40) exhibits the cocontinuous morphology, have been prepared with different contents of f-MWCNTs. The impact measurement shows that f-MWCNTs induce the great improvement of fracture toughness of cocontinuous PP/EVA blends. The results based on the morphologies and the rheological properties of the composites suggest that, a local “single-network structure” of f-MWCNTs exists in PP/EVA (80/20) system whereas a “dual-network structure” of f-MWCNTs and EVA phase exists in PP/EVA (60/40) system, and the latter structure accounts for the largely improved fracture toughness of the composites.     

Role of clay in compatibilization of immiscible high melt strength polypropylene and ethylene vinyl acetate copolymer blends

The compatibilization efficiency of organically modified layered silicates (clay) was studied for immiscible high melt strength polypropylene/ethyl vinyl acetate (EVA) blends for the first time. The size of the dispersed EVA phase in the polypropylene matrix decreased with addition of small amounts of clay (cloisite 20A) to the blend. Scanning electron micrographs (SEM) show an efficient mixing of polymers in the presence of clay. The X‐ray diffraction (XRD) and transmission electron microscopy patterns demonstrate that silicate layers are well dispersed within the phases and are also present at the interphase. This results in substantial size reduction of the dispersed phase. The blends show a drastic increase in mechanical properties with the addition of clay. Differential scanning calorimetry thermo grams further help in understanding blend miscibility in the presence of clay as denoted by the change in the melting range of the components and the crystallization behavior of the components. The dynamic rheology tests reveal a emulsion‐like behavior for the blend system as denoted by the presence of a curvature or kink at lower frequencies, which further increases for the system with clay particles due to decrease in size of the dispersed phase. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Morphology development in immiscible polymer blends

This paper presents the results obtained using a new method for analyzing polymer blend morphologies. The method is based on the selective solubilization of the matrix followed by a separation of the dispersed phase in suspension by filtering. A suspension of the nodular part going through the filter is obtained and can be analyzed with a particle counter. The other part of the dispersed phase retained by the filter is constituted of fibers. The average droplet diameters were compared with those obtained using a Scanning Electron Microscope on fracture surfaces for different compositions and flow conditions. The average diameter obtained with the counter technique increases with the dispersed phase content up to an optimum where simultaneously a decrease in the mean diameter and an increase of the fibrillar part are observed, which means that there is a concentration range where these two types of morphologies are present in the blends. The results indicates that the stability of the fibrillar part seems to determine whether the blend morphology will evolve into nodules by the Rayleigh mechanism or into phase inversion by coalescence of stable fibers.     

Reverse osmosis characteristics of cellulose acetate butyrate membranes

Cellulose acetate butyrate membranes were cast from five different formulations. The pure water flux through the membrane increased with evaporation period. The separation of 4000 ppm NaCl aqueous solution remained unchanged until it reached a critical flux; at that point, separation decreased inversely proportional to the flux. Scanning electron microscope photography of the membranes corresponding to each evaporation period is reported.     

Fiber and film developments from immiscible blends of cellulose acetate propionate and poly(butylene terephthalate)

Binary blends of cellulose acetate propionate (CAP) and poly(butylene terephthalate) (PBT) in the composition range of 5–15 wt % for CAP were prepared in the form of films and fibers by compression molding and spinning, respectively. The presence of two invariant glass‐transition temperatures corresponding to the CAP and PBT components and viscosities lower than those of the neat PBT of the CAP–PBT blends implied that the CAP–PBT blends were immiscible. Moreover, the crystallinity of the PBT component was higher in the spun fibers than in the films; this was possibly due to the different cooling methods or the chain orientation in the spinning process. In the meantime, the CAP component could not undergo crystallization because of its rigid structure and alkyl substituents. For the CAP–PBT films, the amorphous CAP was present as dispersed particles in the PBT matrix; but it became rods in the spun fibers. In addition, the presence of the amorphous CAP resulted in a decrease in the tensile strength and an increase in the elongation at break for the CAP–PBT fibers. The CAP–PBT films and fibers could be applied in a wide range of applications requiring renewable properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45013.     

Physical aging and biaxial creep in cellulose acetate butyrate

Torsional and tension-torsion creep studies have been performed on cellulose acetate butyrate at 65°C. The aging shift factor, μ, at this temperature has been determined to be 0.85. This is somewhat higher than 0.75 which was suggested as a maximum value for cellulose acetate butyrate (5). Axial stresses cause the torsional retardation times to become shorter. The change in retardation time is mainly determined by the magnitude of the axial stress and not by the length of time during which the axial stress is applied. Torsional stresses cause the axial retardation times to shift in a similar manner. The shifting of retardation times follows a maximum shear stress criterion.     

The dynamics of montmorillonite clay dispersion and morphology development in immiscible ethylene-propylene rubber/polypropylene blends

The evolution of morphology during the melt compounding of polypropylene (PP), maleated ethylene-propylene rubber (EPR-g-MAn) and onium-ion exchanged montmorillonite clay (NR₄⁺-MM) is described. Irrespective of the ratio of components, clay partitions into the EPR-g-MAn phase exclusively, with significant amounts of mineral exfoliation occurring in the very early stages of compounding. These changes in filler distribution and dispersion are accompanied by reductions in the size of the dispersed PP phase, as the rate of droplet coalescence falls in response to an elevated EPR-g-MAn matrix viscosity. However, when NR₄⁺-MM is localized in a dispersed EPR-g-MAn phase, coalescence increases as a result of hindered particle break-up.     

Modified polyacrylonitrile blends with cellulose acetate: Fibers' properties

Fiber forming polyacrylonitriles (PAN) were modified by copolymerizing acrylonitrile monomer with methyl acrylate (MA) and 2-acrylamido-2-methyl propane sulfonic acid (AP), respectively, and blended with collulose acetate (CA). Fibers of MA-PAN, AP-PAN, and their blends with CA were wet-spun in dimethylformamide in a broad range of coagulation bath concentrations (CBC). The effects of hydrophilic and hydrophobic modification of PAN and the CBC, as well as the coagulation behavior, were studied in terms of morphology, mechanical properties, and water regain property of the fibers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1937–1946, 1997     

Compatibilization of immiscible blends of polypropylene and isosorbide containing copolyester with silica nanoparticles

In the present study, compatibilization of immiscible blends of polymers was investigated based on the Pickering emulsion concept with various mixing procedures. Silica nanoparticles were incorporated into poly (1,4-cyclohexanedimethylene isosorbide terephthalate) (PEICT)/isotactic polypropylene (iPP) blends. Localization of nanoparticles was effectively modified by varying mixing procedures. Relocation of hydrophilic silica occurred in a secondary mixing procedure with the PEICT, which has relatively high affinity when primarily mixed with iPP. The final location of the silica nanoparticles was confirmed by SEM images. SEM and an optical microscope were used to follow morphological change. By simply changing the mixing procedure, the hydrophilic silica nanoparticles were able to perform the role of a morphology modifier successfully without modifying the surface characteristics. The mechanical properties and crystallization behavior were also compared depending on the surface characteristics of the silica nanoparticles and their final localization.     

Carbon black‐filled immiscible polypropylene/epoxy blends

Carbon black‐ (CB) filled immiscible thermoplastic/thermosetting polymer blends consisting of polypropylene (PP) and epoxy resin were reported in this paper. The PP/epoxy/CB blends with varied compositions and different processing sequences were prepared by melt‐mixing method. The CB distribution and the relationship between morphology and electrical properties of the PP/epoxy/CB blends were investigated. Scanning electron microscopy (SEM), optical microscopy, and extraction experimental results showed that in PP/epoxy blends CB particles preferentially localized in the epoxy phase, indicating that CB has a good affinity with epoxy resin. The incorporation of CB changed the spherical particles of the dispersed epoxy phase into elongated structure. With increasing epoxy content, the elongation deformation of epoxy phase became more obvious and eventually the blends developed into cocontinuous structure. When CB was initially blended with PP and followed by the addition of epoxy resin, the partial migration of CB from PP to the epoxy phase was observed. When the PP/epoxy ratio was 40/60, the percolation threshold was reduced to about 4 phr CB, which is half of the percolation threshold of the PP/CB composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 461–471, 2006     

Dispersion and properties of cellulose nanowhiskers and layered silicates in cellulose acetate butyrate nanocomposites

The aim of this work was to develop well dispersed nanocomposites, in a non water soluble polymer using a non aqueous, low polarity solvent as a dispersion medium. The nanoreinforcements were cellulose whiskers and layered silicates (LSs) and matrix was cellulose acetate butyrate (CAB). Before nanocomposite processing, a homogenizer was used in combination with sonification to achieve full dispersion of the nanoreinforcements in a medium of low polarity (ethanol). After processing, the cellulose nanowhiskers (CNW) showed flow birefringence in both ethanol and dissolved CAB, which indicated well dispersed whiskers. The microscopy studies indicated that the processing was successful for both nanocomposites. The CNW showed a homogeneous dispersion on nanoscale. The LS nanocomposite contained areas with lower degree of dispersion and separation of the LS sheets and formed mainly an intercalated structure. The produced materials were completely transparent, which indicated good dispersion. Transparency measurements also indicated that the nanocomposite containing CNW showed similar performance as the pure CAB. Dynamic mechanical thermal analysis (DMTA) showed improved storage modulus for a wide temperature range for both nanocomposites compared with the pure CAB matrix. This study indicated that CNW have a potential application in transparent nanocomposites based on fully renewable resources. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of a low-molecular-weight compatibilizer on the immiscible blends of cellulose acetate propionate and poly(butylene terephthalate)

Blends of poly(butylene terephthalate) (PBT) and cellulose acetate propionate (CAP) were found to be immiscible. In order to improve the interfacial strength and miscibility of the PBT/CAP blends, a low-molecular-weight poly(ethylene glycol) (PEG) was thus pre-mixed with the CAP to form the P-CAP mixture. It was then blended with the PBT up to 15 wt% using a twin-screw extruder to prepare the PBT/P-CAP blends, and subsequently processed into the films and fibers by compression-molding and melt-spinning, respectively. The thermal and dynamic mechanical analyses suggested that the PBT and CAP became partially miscible and the interfacial strength was thus improved in the PBT/P-CAP blends, owing to the addition of PEG. The PEG was not only miscible with the CAP but also with the PBT, and it served as a plasticizer as well as a compatibilizer. From the observation of the fractured surface of the PBT/P-CAP films, the PBT component was present as dispersed particles in the P-CAP matrix with size ranging from 1.4 to 3.0 μm; yet it became nanofiber in the spun fibers. Successful fibers of the PBT/P-CAP blends with an average diameter of 20 μm could be spun, where the tensile strength and elongation at break were in the range of 0.6?0.7 g/denier and 12?16%, respectively. Finally, the ultra-fine PBT nanofibers with diameters in the range of 50?70 nm were observed after removing the P-CAP matrix with acetone from the fibers, owing to the formation of PBT nanofibers during spinning and orientation processes. This method thus could successfully produce nano-scale PBT fibers with fineness comparable with the nanofibers developed via electrospinning technology.     

醋酸丁酸纤维素与聚丙烯酸乙酯共混体系的研究

通过差热分析和拉伸试验研究了醋酸丁酸纤维素CAB－35－1与聚丙烯酸乙酯（PEA）物理共混、半一互穿网络共混体系的相容性和力学性能，并用扫描电镜观察了共混物的形态。     

A new perspective and comparative study on demixing and gelation behavior of cellulose acetate,cellulose acetate propionate and cellulose acetate butyrate ternary solutions

Cellulose acetate (CA), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB) were fabricated as membrane via nonsolvent induced phase separation process. N,N‐Dimethylformamide (DMF) and N,N‐Dimethylacetamide (DMAc) as solvents and water as nonsolvent were employed. Ternary phase diagrams for all six ternary systems were constructed using Flory‐Huggins theory. In this way, cloud points as well as Berghman's points were determined. Modulus of polymers steepened in various concentration of solvent/nonsolvent mixtures were measured to find the weight fraction of polymer (w_p) in which vitrification takes place. W_P values for CA, CAP, and CAB were obtained 0.59, 0.67, and 0.74 in presence of DMF while those were 0.69, 0.74, and 0.84 in presence of DMAc; whereas glass transition temperatures (T_g) for three polymers were determined 180°C, 142°C, and 101°C correspondingly. Pure water flux for CA, CAP, and CAB membrane increased from 75.7 to 83.4 and 290.3 and from 109.6 to 116.1 and 400.3 L/m² h bar when DMF and DMAc were used as solvents, respectively. Results revealed that as T_g of polymer decreases, the membrane structure vitrifies at higher polymer concentration with more porous structure, bigger pores, higher permeate flux followed by decrease in mechanical strength. POLYM. ENG. SCI., 58:1135–1145, 2018. © 2017 Society of Plastics Engineers     

Characterization of carbon black‐filled immiscible polypropylene/polystyrene blends

The electrical and rheological behaviors of carbon black (CB)‐filled immiscible polypropylene (PP)/polystyrene (PS) blends were investigated. The compounding sequence influences the phase morphology of the ternary CB/PP/PS composites and the distribution of CB aggregates. Simultaneous measurements of resistance and dynamic modulus were carried out to monitor the phase coalescence of the ternary composites and CB migration and agglomeration in the PS phase during annealing at temperatures above the melting point of PP. The variation of resistivity is mainly attributed to CB agglomeration in the PS phase and the interfacial region, while the variation of dynamic modulus is regarded as the superimposition of the phase coalescence and CB agglomeration in the PS phase. The ternary composites with the majority of CB particles distributed in the interfacial region show the lowest conductive percolation threshold and the most stable resistivity–temperature performance during heating–cooling cycles. Copyright © 2011 Society of Chemical Industry     

Rheological properties and microstructures of cellulose acetate phthalate/hydroxypropyl cellulose blends

Cellulose acetate phthalate (CAP)/hydroxypropyl cellulose (HPC) blends were investigated by means of attenuated total reflection‐Fourier transform infrared spectroscopy, thermogravimetry/differential thermal analysis, shear viscosity, oscillatory shear tests, and atomic force microscopy (AFM). Effect of solution concentrations in 2‐methoxyethanol, blend compositions, and shear rate on the rheological functions reflects the mobility of the chain segments or their orientation—with thinning behavior in the shear field. Specific interactions, such as the hydrogen bonds between polymer components and 2‐methoxyethanol used in casting solutions of films, influence the resulting morphology. Supernodular aggregates with different intensities and dimensions, which involve the coexistence of an isotropic and an anisotropic phase, typical for lyotropic cellulosic derivative liquid crystals at low concentrations, are evidenced by AFM images. This study is useful for applications of CAP/HPC blends in pharmaceutical domains.POLYM. COMPOS., 33:2072–2083, 2012. © 2012 Society of Plastics Engineers     

Structure,nonisothermal crystallization behavior,and thermal property study of poly(trimethylene terephthalate)/cellulose acetate butyrate blends

Poly(trimethylene terephthalate) (PTT)/cellulose acetate butyrate (CAB) blends were prepared by melting blending through a co‐rotating twin screw extruder. The structures of PTT/CAB blends were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectra, and the results showed that CAB phase dispersed homogeneously in the PTT matrix and there existed evident phase interface between PTT and CAB. The nonisothermal crystallization behavior was investigated by differential scanning calorimetry (DSC) and was described with modified Avrami equation of Jeziorny and Mo equation, respectively. The results indicated that the half crystallization time (t_{1/ 2}) is much shorter, the nonisothermal crystallization kinetic rate constant (Z_c) is bigger at a given cooling rate, the cooling rate [F_z(T)] is smaller at a given relative crystallinity (X _t) of PTT/CAB blends than those of PTT, which proved that the addition of CAB improved the crystallization of PTT and made PTT crystallize more perfect and faster than pure PTT. In addition, thermogravimetric analysis (TGA) curves of PTT and PTT/CAB blends showed that effects of CAB content on the thermal decomposition of PTT/CAB blends were little. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers