Rheological properties tensile strength

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

The new polymers are intermediate in composition and crystallinity between the essentially amorphous EPR and the semicrystalhne iPP. The presence of the complementary blocks of elastomers for both ethylene and propylene crystallinity should not indicate a similarity, beyond the levels of the crystallinity in the properties of the E-plastomers and the P-plastomers. The E-plastomers and the P-plastomers differ in their stmctural, rheological, as well as their thermal, mechanical, and elastic properties. In a comparison of the tensile strength and tensile recovery (tension set) from a 100% elongation for a range of P-plastomers and E-plastomers, the former have lower tension set than EPR and iPP. However, for comparative E-plastomers and P-plastomers at equivalent tensile strength, the latter have significantly better tension set. In summary, P-plastomers are tough polyolefins which are uniquely soft and elastic. 

Clay hllers were surface modihed with TMPTA or triethoxyvinyl silane (TEVS) followed by EB irradiation by Ray and Bhowmick [394]. Both the untreated and treated fillers were incorporated in an ethylene-octene copolymer. Mechanical, dynamic mechanical, and rheological properties of the EB-cured unfilled and filled composites were studied and a significant improvement in tensile strength, elongation at break, modulus, and tear strength was observed in the case of surface-treated clay-filled vulcanizates. Dynamic mechanical studies conducted on these systems support the above findings. 

Figures 20.13 and 20.14 describe the effect of dibutyltin dilaurate (DBTDL) on the tensile strength and tensile modulus for the 25/75 LCP/PEN blend fibers at draw ratios of 10 and 20 [13]. As expected, the addition of DBTDL slightly enhances the mechanical properties of the blends up to ca. 500 ppm of DBTDL. The optimum quantity of DBTDL seems to be about 500 ppm at a draw ratio of 20. However, the mechanical properties deteriorate when the concentration of catalyst exceeds this optimum level. From the previous relationships between the rheological properties and the mechanical properties, it can be discerned that the interfacial adhesion and the compatibility between the two phases, PEN and LCP, were enhanced. Hence, DBTDL can be used as a catalyst to achieve reactive compatibility in this blend system. This suggests the possibility of improving the interfacial adhesion between the immiscible polymer blends containing the LCP by reactive extrusion processing with a very short residence time.

Rheological Properties. Rheological studies show that ammonia affects the compressive mechanical behavior of wood to a much higher extent than the tensile behavior (55,16). Since the compression strength is highly dependent on lignin content,... 

Fillers increase the strength, impart needed rheological properties, and reduce the cost of sealants. Tensile properties are increased significantly, depending on the type of filler, its particle size, and the type of cure. Improper filler selection can ruin the performance of a polysulfide sealant. Calcium carbonates (wet or dry ground limestone, precipitated), carbon blacks (furnace, thermal), calcined clays, silica and silicate fillers, and rutile titanium dioxide are typical fillers used in polysulfide sealants. Generally, combinations of fillers are used in formulation. Plasticizers improve the working properties while... 

Fibrous fillers may be added to impart specific rheological properties or to reinforce the system. They will usually improve both tensile strength and impact resistance. Addition levels are much lower at 10 to 50 phr, as they usually cause much more rapid thickening. Table 3 lists common fillers. 

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