Polypropylene melt

To polypropylene melt-processed into 5-mil-thick films. Samples exposed at 63°C in a "Uvatest" weathering device. 

Chapter 6 - There has been provided mathematical description of the processes of thermonuclear destruction in deformed polypropylene melts the aim was to use the criterion of destruction estimation in modelling and optimising the processing of polypropylene into products. 

Chapter 10 - There has been investigated the effect of thermo-mechanical impact conditions on destruction kinetics in polypropylene melts. The conditions served as a basis for obtaining quantitative dependencies and mathematical expressions aimed at describing destruction processes. 

During processing polypropylene melts under the action of transverse strain there occur strain-chemical conversions which can result in both decrease and increase in their molecular masses the mechanical effect on the rapidity and level of the occurring processes is considerably more prominent than the mere contribution of thermal and thermal-oxidative breakdown. These data necessitate studying the process of polymer destruction. For this purpose it would be most effective to apply the criterion of assessment of the intensity with which destructive processes happen in polymer melts. 

At the initial period of mechanical destruction in a polypropylene melt in inert atmosphere the concentration of macromolecules increases (figure 2). The dependence of destruction rate (V ) on temperature is linear in the Arrhenius coordinates. After a certain... 

Figure 7 shows the effect of filler particle shape on the viscosity of filled polypropylene melts, containing glass beads and talc particles, of similar density, loading and particle size distribution. The greater viscosity of the talc-filled composition was attributed to increased contact and surface interaction between these irregularly shaped particles. 

More recently, Lin and Masuda [47] measured the viscoelastic properties of polypropylene melts filled with small (0.15 pm) and larger (4.0 pm) calcium carbonate particles. The dynamic modulus and viscosity were found to rise with filler loading especially at low frequencies. With highly filled compositions (at... 

The viscoelastic properties of polypropylene melts containing magnesium hydroxide fire retardant fillers have been studied using parallel plate dynamic rheology [36]. In this work the filler variants differed in particle size, surface area and morphology, ranging from approximately spherical particles formed... 

Fig. 1.6. Doubled extinction angle 1% ( a) and doubled orientation angle 2 (o) vs. shear rate q for a polypropylene melt [36) at 210° C...

As a final remark it may be mentioned that the discussed polypropylene melts do not at all behave like second-order fluids in the range of shear rates and angular frequencies accessible to measurement. This is shown in Fig. 4.6. In this figure the doubled extinction angle 2 is plotted... 

Spherulites. As a polymer melt solidifies, several folded chain lamellae spherulites form which are up to 0.1 mm in diameter. A typical example of a spherulitic structure is shown in Fig. 1.15. The spherulitic growth in a polypropylene melt is shown in Fig. 1.16. 

Polypropylene - Melt flow rate after the first, third and fifth extrusion, at 500°F to determine the degree of chain scission (5). Y. I, index is also determined (6.),... 

Using the method isoclinics, Checker and coworkers [116] studied the flow of polyethylene and polypropylene melts through two dimensional contractions and used birefringence measurements to determine the relaxation behavior of these materials subject to complex flows. 

Scans by differential thermal analysis show a broadening of the polypropylene melting peak for the AFR polymer as the temperature of free radical polymerization decreases. Samples from inert polypropylene powder do not exhibit this same phenomenon. This suggests that for the AFR polymerization, more methylvinylpyridine and acrylonitrile are incorporated on the polypropylene chain as the free radical polymerization temperature is decreased. The AFR polymerization is favored by low temperatures. 

R.Fulchiron, V.Verney, G.Marin, Determination of the elongational behavior of polypropylene melts from transient shear experiments using Wagner s model, J. Non-Newt. Fluid Mech. 45 (1993), 49-61. 

Figure 6.38 Viscosity (open symbols) and first normal stress difference (closed symbols) as a function of shear stress for neat polypropylene melt (Q. )> the same melt filled with 50% by weight CaC03 particles of size 2.5 fx, (A, A), and the filled melt with a titanate coupling agent ( , ). (From Han et al. 1981, reprinted with permission from the Society of Plastics Engineers.)...

Polypropylene Melts and burns with steady Very little Hard, turns... 

Fig. 18 Dissolution temperature of additive 3 (red filled circles) and surface potential of 50 pm-thick i-PP films after annealing at 90 °C for 720 min, as a function of the additive concentration of 3 for two independently prepared series (filled triangles, open triangles). The end of the region II (grey) at 0.15 wt% marks the concentration below which the additive is completely soluble in the polypropylene melt at 260°C (horizontal dashed line) [29]. Reprinted by permission of Elsevier Ltd...

Mutel, T., Kamal, M. R., and Utracki, L. A., Elongational behavior of short glass fiber reinforced polypropylene melts, Polym. Compos., 5, 289-298 (1984). 

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