Tensile modulus with temperature

Figure 5.109 Variation of tensile strength and tensile modulus with temperature of SiC-reinforced aluminum. Reprinted, by permission, from A. KeUy, ed.. Concise Encyclopedia of Composite Materials, revised edition, p. 189. Copyright 1994 by Elsevier Science Publishers, Ltd.

The aggregate model also has been used with success to describe the mechanical anisoti opy of several liquid crystalline polymers. Ward and co-workers [56] examined the dynamic mechanical behaviour of several thermotropic polyesters in tension and shear over a wide temperature range, and used the single-phase aggregate model to relate quantitatively the fall in tensile modulus with temperature to the corresponding fall in shear modulus. 

Figure 4.9 Variation of (a) tensile strength, and (b) tensile modulus with temperature (Arvesen).

Fig. 4. Variation of the axial tensile modulus with product diameter. Extrusion temperature 100 °C, nominal draw ratio 10, sample R 40 (for sample description see Table 2) ...

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). 

The tensile creep behaviour of oriented high-density polyethylene has been studied by McCrum and coworkers " and by Ward and co-workers. " No creep curves as such are given, but the variation of isochronous modulus with temperature for specimens cut at various angles... 

Fig, 3-21 shows the variation of 100-s 0.5% tensile secant modulus with temperature. The results indicate the significant improvement in properties by reinforcing the polymer matrices with glass fibers. The stiffness between reinforced and unreinforced thermoplastics remains fairly constant over the temperature range fi om 20 to 100 C. The most outstanding thermoplastic material in terms of stiffness is the 30% glass-filled Noryl (J). 

A method developed from temperature induced phase separation was completed to obtain PLA/bacterial cellulose composites [174]. In this work, bacterial cellulose was added to 1,4-dioxane and homogenized before PLA was added and dissolved before the mixture was added dropwise into a liquid nitrogen bath. The precipitate was collected and freeze-dried to produce composite microspheres, which were then fed into a twin-screw extruder and were mixed at 180°C, extruded, pelletized and hot press compression moulded into films. PLA films containing bacterial cellulose showed an increase in tensile modulus, with composites containing bacterial cellulose, and chemically modified bacterial cellulose shown to have improvements over PLA alone [174]. 

Fig. 5 shows the variation of loss modulus with temperature for Ni-P coated samples in tension mode. Loss modulus increases for lower Ni-P coating times. An improvement of about 32% in tensile loss modulus was... 

Figure 7. Tensile modulus with respect to machine nozzle temperature...

It may be prepared in two stereo-regular forms, cis- and trans-. The cii-polymer, which crystallises in zig-zag form, has a of 235°C, whilst the fran -polymer, which crystallises in helical form, melts at the much lower temperature of 145°C. Tensile strengths of both forms are reportedly similar to that of Penton whilst the tensile modulus of 2300 MPa is about twice as high. Unfortunately the material is rather brittle with an impact strength only about half that of polystyrene although this may be improved by orientation. 

These two moduli are not material constants and typical variations are shown in Fig. 5.3. As with the viscous components, the tensile modulus tends to be about three times the shear modulus at low stresses. Fig. 5.3 has been included here as an introduction to the type of behaviour which can be expected from a polymer melt as it flows. The methods used to obtain this data will be described later, when the effects of temperature and pressure will also be discussed. 

Table 4 shows that tensile modulus E, and strength a/, decreased with increase of the melt temperature T, and shear rate y. From fractured surfaces, TLCP domains... 

Curves showing change of tensile strength, flexural strength, and modulus with increasing temperatures or other environments. 

Typical tension stress-strain curves of baseline and irradiated unidirectional T300/934 composites tested in [0] and [90] orientations at three different temperatures (121 are shown in Figures 11 and 12. Irradiation had essentially no effect on the fiber-dominated tensile modulus of the [0] specimen and caused only a small (10-15%) reduction in strength at the low and elevated temperatures. For the matrix-dominated [90] laminates, irradiation caused a very substantial decrease in strength at three test temperatures (-38% at -157°C, -26% R.T., -13% 121°C). Irradiation increased the modulus at -157°C and R.T. (10 - 15%), but lowered it at 121°C (-15%). These results are consistent with results obtained on the neat resin specimens discussed above. 

The effect of the annealing temperature on the initial modulus is also presented in Figure 20.8. The moduli of monofilaments annealed at 160 °C for 30 min are higher than those of normal monofilaments, because the matrix polymers are recrystallized with a low PHB content, and the LCP molecules in the domain are reoriented with a high PHB content. The thermal treatment of the PHB/PEN/PET fibers can be an effective way to improve the tensile properties, especially the tensile modulus, and high-speed winding may be a promising way to obtain fibers... 

Tensile Modulus. Tensile samples were cut from the 0.125 in. plates of the compositions according to Standard ASTM D638-68, into the dogbone shape. Samples were tested on an Instron table model TM-S 1130 with environmental chamber. Samples were tested at temperatures of -30°C, 0°C. 22°C, 50°C, 80°C, 100°C and 130°C. Samples were held at test temperature for 20 minutes, clamped into the Instron grips and tested at a strain rate of 0.02 in./min. until failure. The elastic modulus was determined by ASTM D638-68. Second order polynomial equations were fitted to the data to obtain the elastic modulus as a function of temperature for each of the compositions. 

Metal ion modified polyimide films have been prepared to obtain materials having mechanical, electrical, optical, adhesive, and surface chemical properties different from nonmodified polyimide films. For example, the tensile modulus of metal ion modified polyimide films was increased (both at room temperature and 200 0 whereas elongation was reduced compared with the nonmodif ied polyimide (i). Although certain polyimides are )cnown to be excellent adhesives 2) lap shear strength (between titanium adherends) at elevated temperature (275 0 was increased by incorporation of tris(acetylacetonato)aluminum(III) (2). Highly conductive, reflective polyimide films containing a palladium metal surface were prepared and characterized ( ). The thermal stability of these films was reduced about 200 C, but they were useful as novel metal-filled electrodes ( ). 

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