Polymer nanocomposites polyester/clay

Incorporation of modified clays into thermosetting resins, and particularly in epoxy35 or unsaturated polyester resins, in order to improve thermal stability or flame retardancy, has been reported.36 A thermogravimetric study of polyester-clay nanocomposites has shown that addition of nanoclays lowers the decomposition temperature and thermal stability of a standard resin up to 600°C. But, above this temperature, the trend is reversed in a region where a charring residue is formed. Char formation seems not as important as compared with other polymer-clay nanocomposite structures. Nazare et al.37 have studied the combination of APP and ammonium-modified MMT (Cloisite 10A, 15A, 25A, and 30B). The diluent used for polyester resin was methyl methacrylate (MMA). The... 

R.K. Bharadwaj, A.R. Mehrabi, C. Hamilton, C. Trujillo, M. Murgs, R. Fan, A. Chavira, and A.K. Thomson, Structure-properties relationships in crosslinked polyester-clay nanocomposites, Polymer, 2002, 43 3699-3705. 

Improvements in the reduction of flammability of polymers with low clay contents and better processability have been reported, in addition to reductions in the concentration of toxic vapors produced in the combustion stage [116-120]. In connection to their flame-retardant properties, exfoliated nanocomposites based on PP [121, 122, 115, 123], PS [115, 123, 124], poly(ethylene-vinyl acetate) [125, 126], styrene-butadiene rubber [127], PMMA [128], polyesters... 

How does nanoclay in vegetable oil-based polymer nanocomposites act as a catalyst in the biodegradation of polyester/clay nanocomposites ... 

U. Konwar, N. Karak and M. Mandal, Mesua ferrea L. seed oil based highly thermostable and biodegradable polyester/clay nanocomposites , Polym Degrad Stab, 2009, 94, 2221-30. 

Le Digabel F, Boquillon N, Dole P et al (2004) Properties of thermoplastic composites based on wheat-straw lignocellulosic fillers. J Appl Polym Sci 93 428-436 Lee S -R, Park FI-M, Lim H et al (2002) Microstructuie, tensile properties, and biodegradability of aliphatic polyester/clay nanocomposites. Polymer 43 2495-2500 Lee SFI, Ohkita T, Kitagawa K (20(M) Eco-composite from poly(lactic acid) and bamboo fiber. Flolzforschung 58 529-536... 

This system does not increase the carbon monoxide or soot produced during the combustion, as many commercial FRs do [233]. Other polymer silicate nanocomposites based on a variety of polymers, such as polystyrene, epoxy and polyesters, have been prepared recently by melt intercalation [236]. A direct synthesis of PVA-clay (hectorite) complexes in water solution (hydrothermal crystallization) was reported [237]. It was assumed that the driving force of this phenomenon, at least kinetically, can be described in terms of a simple diffusion reaction of polymers/monomers into clay-layered structures. 

Bharadwaj, R.K. Mehrabi, A.R. Hamilton, C. Trujillo, C. Murga, M. Fan, R. Ch-avira. A. Thompson, A.K. Structure-property relationships in cross-linked polyester-clay nanocomposites. Polymer 2002, 43, 3699-3705. 

For polyester, the reported work82 done in Sichuan University of China, involves adding MMT clay in a copolymer of poly(ethyleneterephthalate), which with a phosphorus-containing monomer could produce PET with higher thermal stability and char-forming tendency. However, fibers were not produced from this PET-nanocomposite polymers. 

The procedure to obtain nanocomposites based on unsaturated polyester resins leads to improvements in the order of 120% in the flexural modulus, 14% in flexural strength and 57% increase in tensile modulus with 4.7% of clay slurry content. Thermal stability augments and the gelation temperature increases to 45 °C, as compared to that of the resin (Fig. 31.6). It seems that adding water to the MMT allows better intercalation of polymer chains into the interlamellar space. Because clay is first suspended in water, this improves dispersion and distribution of the particles in the resin matrix. Longer gelation times lead to more uniform and mechanically stronger structures and to yield stresses (Fig. 31.7). Enhanced polymer-clay interactions are revealed by XPS in this case (Fig. 31.8). 

Besides melt intercalation, described above, in situ intercalative polymerization of E-caprolactone (e-CL) has also been used [231] to prepare polycaprolactone (PCL)-based nanocomposites. The in situ intercalative polymerization, or monomer exfoliation, method was pioneered by Toyota Motor Company to create nylon-6/clay nanocomposites. The method involves in-reactor processing of e-CL and MMT, which has been ion-exchanged with the hydrochloride salt of aminolauric acid (12-aminodecanoic acid). Nanocomposite materials from polymers such as polystyrene, polyacrylates or methacrylates, styrene-butadiene rubber, polyester, polyurethane, and epoxy are amenable to the monomer approach. 

Recently, the authors of this chapter have prepared polymer/clay nanocomposites using a water-soluble hyperbranched aliphatic polyester (Bottom from Perstorp) [Decker et al., 2009]. The nanocomposites were prepared via a solution-intercalation method using deionized water as the solvent medium. The nanocomposite preparation recipe was similar to that used by Plummer et al. [2002]. There are several advantages of this system compared to many other polymer/clay nanocomposite systems. These include the fact that no surfactant is required, the polymer is amorphous, and a broad range of composites from 0 to 95 wt% can be easily prepared. This... 

Cha Chaeichian, S., Wood-Adams, P. M., Hoa, S. V. In situ polymerization of polyester-based hybrid systems for the preparation of clay nanocomposites. Polymer 54 (2013) 1512-1523. 

U. Konwar and N. Karak, Hyperbranched poiyether core containing vegetable oil modified polyester and its clay nanocomposites . Polymer I, 2011, 43, 565-76. 

The effect of loading (0.5,1.0 and 2.0 wt%) nanostructured polyaniline (PANI) on the physiochemical, physicomechanical, morphological and thermal properties of soybean oil-based polyester nanocomposites has also been reported. The nanocomposites of conjugated linseed oil, acrylic acid and divinylbenzene are synthesised using modified montmoriUonite clay. The resultant nanocomposites exhibit a storage modulus in the range of 17-79 MPa at the glass transition temperature compared to the pristine polymer which is 2.1 MPa. The nanocomposites show better thermal stability (up to 200°C) than the pristine polymer. 

Nanocomposites of thermoset polymers like unsaturated polyester and epoxy can be fabricated by this method. In this process, the monomers/ prepolymers are allowed to intercalate the layer spacing of the clay platelets. Polymerization will then be initiated either by the application of heat or radiation or by introducing suitable organic initiator. The intercalated monomer swells the clay and during polymerization increases the interlayer spacing and results in the formation of intercalated or exfoliated nanocomposites. 

The co-continuous structure and the final rheological properties of an immiscible polymer blend are generally controlled by not only the viscoelastic and interfacial properties of the constituent polymers but also by the processing parameters. For example, the effect of plasticizer on co-continuity development in blends based on polypropylene and ethylene-propylene-diene-terpolymer (PP/EPDM), at various compositions, was studied using solvent extraction. The results showed more rapid percolation of the elastomeric component in the presence of plasticizer. However, the same fuUy co-continuous composition range was maintained, as for the non-plasticized counterparts (Shahbikian et al. 2011). It was also shown that the presence of nanoclay narrows the co-continuity composition range for non-plasticized thermoplastic elastomeric materials (TPEs) based on polypropylene and ethylene-propylene-diene-terpolymer and influences their symmetry. This effect was more pronounced in intercalated nanocomposites than in partially exfoliated nanocomposites with improved clay dispersion. It seems that the smaller, well-dispersed particles interfere less with thermoplastic phase continuity (Mirzadeh et al. 2010). A blend of polyamide 6 (PA6) and a co-polyester of... 

Biodegradable polymers can be mainly classified as agro-polymers (starch, protein, etc.) and biodegradable polyesters (polyhydroxyalkanoates, poly(lactic acid), etc.). These latter, also called biopolyesters, can be synthesized from fossil resources but main productions can be obtained from renewable resources (Bordes et al. 2009). However for certain applications, biopolyesters cannot be fully competitive with conventional thermoplastics since some of their properties are too weak. Therefore, to extend their applications, these biopolymers have been formulated and associated with nano-sized fillers, which could bring a large range of improved properties (stiffness, permeability, crystallinity, thermal stability). The resulting nano-biocomposites have been the subject of many recent publications. Bordes etal. (2009) analyzed this novel class of materials based on clays, which are nowadays the main nanoflllers used in nanocomposite systems. 

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