Polypropylene/calcium carbonate nanocomposites

Fused deposition modeling with polypropylene

The mechanisms which have been suggested to explain the deformation of crystalline polymers are reviewed. Emphasis has been placed upon the type of information that can be gained from experimental observations and on the extent to which those observations are consistent with suggested deformation mechanisms and current ideas on polymer structure and morphology.

Deformation mechanisms in crystalline polymers

A mathematical model of ductile hole growth under the application of a mean tensile stress is developed and applied to the problem of spallation in solids. The object is to describe dynamic ductile fracture under a wide range of tensile loading conditions. The mathematical model presented here describes both plate‐impact spallation (as observed by postshot examination and time‐resolved pressure measurements) and explosively produced spallation (as observed by dynamic x‐radiographic techniques) in copper. It is found to be inapplicable to ductile fracture of expanding rings, even in the absence of possible adiabatic shear banding and classical necking instabilities, because of the fact that the mean tensile stress (void growth) and the deviatoric stress (homogeneous plastic shear strain) are not independent. A phenomenological model of void growth under uniaxial stress conditions is developed independently and applied to the numerical finite‐difference solution of fracture in an expanding ring. The initial...

/pdf/dynamic-fracture-and-spallation-in-ductile-solids-316qkcactf.pdf

Dynamic fracture and spallation in ductile solids

Correlation between degree of crystallinity, morphology, glass temperature, mechanical properties and biodegradation of poly (3-hydroxyalkanoate) PHAs and their blends

Tensile tests show that for isotactic polypropylene the graph of yield stress versus spherulite size goes through a maximum at a critical spherulite size. Scanning electron and transmission optical microscopy indicate that this represents a change-over from spherulite yield to boundary yield, caused by an increased segregation of impurities at the boundaries coupled with voidage owing to contraction of the spherulites on cooling.

The effect of spherulite size on the fracture morphology of polypropylene

The optimum conditions for butt fusion welding certain grades of polyethylene, polybutene-1 and polypropylene pipes have been determined on the basis of tensile test results. The effect of the welding bead has been discussed and the conclusion reached that removal of the welding beads enables a clearer picture to be obtained of weld performance when this is judged from a tensile test. An examination of the microstructures of each weld has shown the presence of different zones. The importance of these zones is discussed in relation to the short- and long-term strength of the welds.

The use of tensile tests to determine the optimum conditions for butt fusion welding certain grades of polyethylene, polybutene-1 and polypropylene pipes

The deformation of isotactic polypropylene has been studied by optical microscopy of thin sections cut from bulk tensile specimens. An attempt has been made to relate the three different deformation zones within a spherulite to the cross-hatched structure peculiar to polypropylene.

Some studies of deformation processes in fully-spherulitic polypropylene

Microstructural features characterizing butt welds in polyethylene and polybutene-1 pipes have been studied using scanning electron and transmission optical microscopy. The microstructures are explained on the basis of temperature gradients measured in the region of the welds and the flow of molten material during welding.

Some microstructural features of the welds in butt-welded polyethylene and polybutene-1 pipes

The butt fusion welding of four different grades of polyethylene pipe has been studied and the feasibility of producing good welds between pipes of different melt flow index has been examined. Weld quality has been assessed on the basis of tensile tests and microstructural studies. The factors influencing the microstructure are discussed; in particular, the flow of molten polymer within the welds.

J. R. Atkinson

Papers

The effect of spherulite size on the fracture morphology of polypropylene

The use of tensile tests to determine the optimum conditions for butt fusion welding certain grades of polyethylene, polybutene-1 and polypropylene pipes

Some studies of deformation processes in fully-spherulitic polypropylene

Some microstructural features of the welds in butt-welded polyethylene and polybutene-1 pipes

The use of tensile tests to determine the optimum conditions for butt welding polyethylene pipes of different melt flow index