Polypropylene, tensile properties

Antioxidants may be assessed in a variety of ways. For screening and for fundamental studies the induction period and rate of oxidation of petroleum fractions with and without antioxidants present provide useful model systems. Since the effect of oxidation differs from polymer to polymer it is important to evaluate the efficacy of the antioxidant with respect to some property seriously affected by oxidation. Thus for polyethylene it is common to study changes in flow properties and in power factor in polypropylene, flow properties and tendency to embrittlement in natural rubber vulcanisates, changes in tensile strength and tear strength. 

Table 11.4 Effect of percentage stretch on tensile properties of polypropylene film ...

Mechanical strength becomes an important criterion, because wound cells (spiral-type construction), in which a layer of separator material is spirally wound between each two electrodes, are manufactured automatically at very high speed. Melt-blown polypropylene fleeces, with their excellent tensile properties, offer an interesting option. Frequently two layers of the same or different materials are used, to gain increased protection against shorts for button cells the use of three layers, even, is not unusual. Nevertheless the total thickness of the separation does not exceed 0.2 - 0.3 mm. For higher-temperature applications (up to about 60 °C) polypropylene fleeces are preferred since they offer a better chemical stability, though at lower electrolyte absorption [ 114"]. 

The equilibrium shear modulus of two similar polyurethane elastomers is shown to depend on both the concentration of elastically active chains, vc, and topological interactions between such chains (trapped entanglements). The elastomers were carefully prepared in different ways from the same amounts of toluene-2,4-diisocyanate, a polypropylene oxide) (PPO) triol, a dihydroxy-terminated PPO, and a monohydroxy PPO in small amount. Provided the network junctions do not fluctuate significantly, the modulus of both elastomers can be expressed as c( 1 + ve/vc)RT, the average value of vth>c being 0.61. The quantity vc equals TeG ax/RT, where TeG ax is the contribution of the topological interactions to the modulus. Both vc and Te were calculated from the sol fraction and the initial formulation. Discussed briefly is the dependence of the ultimate tensile properties on extension rate. 

Fu SY, Lauke B, Mader E, Yue CY, Hu X. Tensile properties of short-glass-fiber- and short-carbon-fiber-reinforced polypropylene composites. Composites Part A Applied Science and Manufacturing. 2000 31(10) 1117-25. 

Eoams were extruded from low density polyethylene (LDPE) and blends of LDPE with syndiotactic polypropylene (sPP), using isobutane as the blowing agent. The extruded materials were characterised by measurement of dimensional stability at room temperature, density, tensile properties, dynamic stiffness, and crystallinity determined by differential scanning calorimetry. The sPP, with a slow crystallisation rate, did not interfere with the expansion of the LDPE, and enhanced the temperature resistance by in-situ crystallisation. The blends were flexible, dimensionally... 

The tensile properties of isotactic polypropylene materials reinforced with continuous nylon fibers were measured. Less than 10 vol % of the fibers leads to an increased yield strength and yield elongation. As little as 3 vol % of the nylon fibers increased the elongation at necking from 10 to 20%. This retarded necking arises from the fiber-matrix debonding which delocalizes the microscopic yielding processes. 

THE STRUCTURE AND TENSILE PROPERTIES OF COLD DRAWN MODIFIED CHALK FILLED POLYPROPYLENE... 

Compositions of polypropylene with unmodified and modified chalk were obtained by means of a screw extruder at 210 C. The granulated product was used to prepare compression moulded films 0.4 mm thick which were pressed at 190 C and then quenched in iced water. From films obtained in this way oarshaped samples with the dimensions as in Fig. 2 were punched. In all cases the samples were cut out form the same places in compression moulded films in order to provide approximately the same flow-induced orientation of chalk particles relative to the sample axis. For the purpose of tensile properties and volume changes measurements the samples were marked (see Fig. 2). 

S. Saengsuwan, S. Bualek-Limcharoen, G. R. Mitchell, and R. H. Olley. Thermotropic liquid crystalline polymer (Rodrun LC5000)/polypropylene in situ composite films Rheology, morphology, molecular orientation and tensile properties. Polymer, 44 3407-3415, 2003. 

P Davies, F Pomies and L A Carlsson, Influence of water absorption on transverse tensile properties and shear fracture toughness of glass/polypropylene , / Compos Mater 1996 30(9) 1004-1019. 

L. Jilk6n, G. Malhammar, R. Selden, The effect of mineral fillers on impact and tensile properties of polypropylene. Polym. Test. 10(5), 329-344 (1991)... 

The objective of this work was to use rice straw pulp cellulose fiber to prepare environmental-friendly rice straw fibril and fibril aggregates (RSF) and evaluate the fibril and fibril aggregates as a novel reinforcing material to compound polypropylene (PP)/ RSF nanocomposite. The scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD), laser diameter instrument (LDl) were used to evaluate the characteristics of RSF. The RSF/PP nanocomposite was prepared by novel extrusion process. The interface compatibility and tensile properties of nanocomposite were investigated by FTIR and tensile test, respectively. 

Polypropylene would rarely be used at ambient t peratures above 30 or so because it loses tensile properties once... 

As stated above, conventional synthetic fibres may be rendered inherently flame retardant during production by either incorporation of a flame retardant additive in the polymer melt or solution prior to extrusion or by copolymeric modification before, during, or immediately after processing into filaments or staple fibres. Major problems of compatibility, especially at the high tanperatures used to extrude melt-extruded fibres like polyamide, polyester, and polypropylene and in reactive polymer solutions such as viscose dope and acrylic solutions, have ensured that only a few such fibres are commercially available. A major problem in developing successful inherently flame retardant fibres based on conventional fibre chemistries is that any modification, if present at a concentration much above 10wt% (whether as additive or comonomer), may seriously reduce tensile properties as well as the other desirable textile properties of dyeability, lustre and appearance, and handle, to mention but a few. 

Hasan, M., Zhou, Y, Jeelani, S. (2006). Thermal and Tensile Properties of Aligned Carbon Nanofiber Reinforced Polypropylene. 11 -l 136. 

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