Thermoplastic properties

Crystallization and Melting Point. The abihty of PVA to crystallize is the single most important physical property of PVA as it controls water solubiUty, water sensitivity, tensile strength, oxygen barrier properties, and thermoplastic properties. Thus, this feature has been and continues to be a focal point of academic and industrial research (9—50). The degree of crystallinity as measured by x-ray diffraction can be directly correlated to the density of the material or the swelling characteristic of the insoluble part (Fig. 2). 

The solvation by plasticiser also gives celluloid thermoplastic properties owing to the reduction in interchain forces. On the other hand since the cellulose molecule is somewhat rigid the product itself is stiff and does not show rubbery properties at room temperature, cf. plasticised PVC. 

Fig. 8.1. Effects of crosslinking on various properties (X) of the polymer. The deviation [X — XcoJ/Xa, from the thermoplastic property (X ) is plotted against Me1, the inverse molecular mass between crosslinks.

The polymerization of cyclic low-molar-mass polycarbonates, polyarylates, and PBT to high-molar-mass thermoplastics has been extensively studied by the General Electric Company during the last decade.57,58 Due to very low viscosity, cyclic oligoesters can be processed like thermosetting resins but retain thermoplastic properties in the final state, after polymerization in the presence of suitable... 

As previously discussed, solvents that dissolve cellulose by derivatization may be employed for further functionahzation, e.g., esterification. Thus, cellulose has been dissolved in paraformaldehyde/DMSO and esterified, e.g., by acetic, butyric, and phthalic anhydride, as well as by unsaturated methacrylic and maleic anhydride, in the presence of pyridine, or an acetate catalyst. DS values from 0.2 to 2.0 were obtained, being higher, 2.5 for cellulose acetate. H and NMR spectroscopy have indicated that the hydroxyl group of the methy-lol chains are preferably esterified with the anhydrides. Treatment of celliflose with this solvent system, at 90 °C, with methylene diacetate or ethylene diacetate, in the presence of potassium acetate, led to cellulose acetate with a DS of 1.5. Interestingly, the reaction with acetyl chloride or activated acid is less convenient DMAc or DMF can be substituted for DMSO [215-219]. In another set of experiments, polymer with high o -celliflose content was esterified with trimethylacetic anhydride, 1,2,4-benzenetricarboylic anhydride, trimellitic anhydride, phthalic anhydride, and a pyridine catalyst. The esters were isolated after 8h of reaction at 80-100°C, or Ih at room temperature (trimellitic anhydride). These are versatile compounds with interesting elastomeric and thermoplastic properties, and can be cast as films and membranes [220]. 

Margolis, J. M., editor. Engineering Thermoplastics, Properties and Applications Marcel Dekker New York, 1985. 

Thermoplastic processing, 10 178-179 of poly(ethylene oxide) resins, 10 684 Thermoplastic properties... 

It has been reported that thermoplastic properties can be imparted to wood by modification of wood particles with fatty acid chlorides in a dinitrogen tetroxide -dimethylformamide - pyridine mixture (Funakoshi etal., 1979 Shiraishi etal, 1979, 1983). A method has also been developed for the modification of wood sawdust without the addition of organic solvents (Thiebaud and Borredon, 1995), and the thermal properties of such modified wood determined (Thiebaud etal, 1997). 

Benzylation has been performed on wood in order to impart thermoplastic properties to the substrate (Hon and Ou, 1989). Wood is pre-treated with aqueous NaOH solution, then with benzyl chloride. Benzylation of the surfaces of wood blocks and chips for selfbonding of wood surfaces has also been reported (Kiguchi, 1990a,b Kiguchi and Yamamoto, 1992). A vapour-phase benzylation method has also been developed (Kiguchi, 1993). Carboxymethylation of NaOH-treated wood using various solvent systems has been studied (Shiraishi and Kishi, 1986 Honma and Nakano, 1991). Wood modified in this way has been used to make wood-phenolic adhesives (Kishi and Shiraishi, 1986). 

Timar, M.C., Maher, K., Me, M. and Mihai, M.D. (2000a). Preparation of wood with thermoplastic properties. Part 2. Simplified technologies. Hol orschung, 54(1), 77-82. 

Some sets of thermoplastic properties are unattainable for the other materials, for example ... 

Blending of the lowest price commodity polymers from synthetic and carbohydrate polymer families [e.g., poly(ethylene) and starch] would appear to follow these laws. Although each polymer class is produced in large volume (first law), the production rate for com starch/synthetic polymer blends is much lower than that for the synthetic polymer this slower extrusion rate directly affects the final cost. Ignoring this limitation, the film properties of the blend are significantly poorer than those of the synthetic polymer film. Both deficiencies are related to the poor thermoplastic properties of water-soluble polymers such as cora-starch. 

If the mobile phase is present in a significant concentration, as suggested by the results of solvent extraction studies (1,8), the practical meaning of the mobile phase to coal conversion processes may be profound. In coal liquefaction, two stage processes emphasizing the mobile phase and the macromolecular structure separately could well be most economical. In devolatilization kinetics, at least two sets of kinetic parameters are necessary to model the devolatilization phenomena associated with the mobile phase and the macromolecular structure respectively since the mobile phase components devolatilize at much lower temperatures than the macromolecular structure components 0. In addition, the mobile phase appears to have a significant influence on the thermoplastic properties of coal (0 and thereby on coke quality. 

The low-volatile bituminous Bulli coal which contains no liptinite and has significant thermoplastic properties has a M2J pyrogram (Figure 2 (F)) showing only one fusion transition which is lesser in extent and shifted to higher temperatures than that of the Liddell coal. This transition is, of course, attributed to aromatic-rich macerals. 

This study shows that limited oxidation at 373 K or weathering (ambient) of coal feedstock reduces the thermoplastic properties of a coal This is manifest as a transformation in char type, from cenospheres to inertoids, at high rates of heating (10 -10 K s" ) in an Entrained Flow Reactor at 1273 K. The specific types of char are related to the chemical structure of the coal and an inverse relationship exists between the occurrence of cenospheric chars and the atomic 0/C ratio of the oxidised or weathered coal from which they are derived... 

The ability of PVA to crystallize is the single most important physical properly of PVA as it controls water solubility, wrier sensitivity, tensile strength, oxygen barrier properties, and thermoplastic properties. 

Engineering Thermoplastics Properties and Applications, edited by James M. Margolis... 

All of the chemical evidence that can be marshalled indicates that wood fiberboard manufacture exploits the thermoplastic properties of lignin. Defibering is effected by the thermal softening of lignin in the middle lamella at saturated steam pressures above 130C. Interfelted fiber mats are consolidated with or without densification pressure by the thermoplastic fusion of lignin-rich fiber surfaces at high board conversion temperatures. 

It is then of interest to give thermoplastic property to wood or cellulose in order to obtain similarly workable materials as... 

Ethyl cellulose (EC) is a water-insoluble cellulose ether. It is produced by reaction of alkali cellulose with ethylene chloride. It has film-forming and thermoplastic properties. As a plastic, it can be processed by extrusion and injections. It is hard, stiff and with good resistance to impact. It is soluble in the molten state with other thermoplastics. As for its film-forming properties, it is used in the formulation of varnishes, inks and glues. It forms removable coatings. 

Ogorkiewicz RM (Ed), "Thermoplastics, Properties and Design", Wiley-Interscience, London, 1974. 

Nielsen LE, "Mechanical Properties of Polymers and Composites", 2 Vols, Marcel Dekker, New York, 1974. Ogorkiewicz RM (Ed), "Thermoplastics, Properties and Design", Wiley Intersdence, London, 1974. 

Khan, M. R., Thermoplastic Properties of Coal Pyrolysis at Elevated Pressures Effects of Experimental Variables, Inorganic Additives, and Preoxidation, Ph D. thesis, The Pennsylvania State University, pp. 333... 

Rare earth halide (in particular NdCl3)-based compounds are very active catalysts for polymerization of dienes. The products are polymers with improved elastic and thermoplastic properties caused by high stereo regularity. The polymerization process is highly efficient (i.e.) 60 000 moles of butadiene are polymerized by one atom of rare earth. Hence the demand for rare earth compounds as polymerization catalysts is low. 

Shiraishi and Goda [16] reported that allylated wood meals were given thermoplastic properties by blending with appropriate synthetic polymers or low molecular weight plasticizers such as dimethylphthalate or resorcinol. Mere allylation did not render wood thermally meltable. Films from the allylated wood-polyethylene and allylated wood-polypropylene (1 2) blends exhibit tensile strengths of 92.2 and 159.0 MPa and elongations of 14.6 and 3.8% respectively, [16]. 

As described above, the products of oligoesterification [Reaction (15)] consist of oligoesterified woods and viscous liquids consisting mainly of polymerizable free oligoesters [83-85]. The oligoesterified woods do not show good thermoplastic properties. Similarly, in the case of the wood-MA-AGE series... 

Ethylene-norbornene copolymers, which have thermoplastic properties when heated above their glass transition temperatures of ca. 200-250°C, have been commercialized by Ticona GmbH under the trade name TOPAS (Tliermoplas-tic Olefin Polymer of Amorphous Structure). Their properties - exceptional transparency, low double refraction, high stiffnes and hardness, low permeability for moisture and excellent biocompatibility - make these ethylene-norbornene copolymers particularly valuable as engineering polymers, for optical applications and as materials for food and medical packaging. 

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