摘要:

AbstractThere are over 50 different organic peroxides and azo compounds (in over 100 different formulations) produced commercially as free radical initiators (curing agents) for the polymer and resin industries. Thus, the user has many initiators to choose from and has usually relied on the resin and/or initiator producer to select his initiator system. This paper will discuss these initiators in general showing the different types‐ of initiator classes; how and why the activity of each class of initiator is varied by structure changes; how different initiators and/or promoter levels affect the curing process; and present guidelines that an end user might use to choose the right initiator for his resin syste

ISSN:0032-3888    

DOI:10.1002/pen.760190902

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe adaptation of a cylindrical geometry fracture toughness test specimen to testing of polymeric dental biomaterials is demonstrated. The specimen configuration facilitates the fabrication of small specimens and simplifies the experimental study of environmental effects on properties of dental biomaterials. The test method is used to measure critical stress intensity factor,KICfor poly (methyl methacrylate) (PMMA), particulate composite restorative materials, and dental polymers. Values obtained are in agreement with data reported for other specimen configurations.

ISSN:0032-3888    

DOI:10.1002/pen.760190903

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA comparative experimental study of extrudate swell from long slit and capillary dies is reported for rheologically characterized polystyrene and polypropylene melts. Generally extrudate swell from a slit is greater than that from a capillary die. At low die wall shear rates it goes to a value of about 1.2 as opposed to about 1.1 found for capillary dies. The onset and character of extrudate distortion have been studied. The experimental results are compared with theories of swell based on unconstrained recovery from Poiseuille flow in these geometries. A detailed analysis of such theories of extrudate swell based on the original work of Tanner has been carried out. The analysis is placed in a more general form which should be valid for a range of die cross‐section

ISSN:0032-3888    

DOI:10.1002/pen.760190904

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA broad range of experiments on carbon black filled polystyrene melts shows the reinforcing effect of the filler. This study represents one of the most extensive investigations of a series of highly filled polymer melts. Stress relaxation and dynamic experiments characterize the small strain behavior while the steady state shear viscosity, normal stresses, and elongational flow experiments describe the large strain deformation rate response. Extrudate swell and unconstrained shrinkage of extrudates are also measured. Highly filled systems exhibit yield values. This is seen in the dynamic experiments and in the shear and elongational viscosities. Viscosity does not level off at finite values with decreasing deformation rate but continues to increase in an approximately inverse manner. This corresponds to yield values of order 5 × 105dynes/cm2. The storage modulus also does not tend to zero at low frequencies. The small strain dynamic properties and stress relaxation results suggest high memories for small strain experiments. Txtrudate swell values are however small and the systems exhibit minimal delayed recovery. The implications of this are considered. Generally it is argued that at volume loadings between 10 and 20 percent, the system takes on the characteristics of a gel and the response is similar to that of a Schwedoff body

ISSN:0032-3888    

DOI:10.1002/pen.760190905

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA procedure is described which permits the classification of solvents according to their effect on polycarbonate (PC):Class I—dissolve amorphous or crystalline PCClass II—dissolve only amorphous PCClass III—convert amorphous PC to crystalline PCClass IV—none of the above.This classification is achieved by comparing solvents to CH2Cl2with respect to the exotherm and rate of crystallization observed when the solvents are brought into contact with PC under controlled con

ISSN:0032-3888    

DOI:10.1002/pen.760190906

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractOrder‐disorder transitions occur in fiber orientation and distribution during extrusion of fiber‐filled poly (ethylene terephthalate) and its blends with other polymers. Associated with these transitions are three characteristic regimes of extrudate surface morphology, cross‐sectional structure and fiber distribution. Low wall shear rates result in a “smooth porcupine” surface, polygonal cross section, and uniform fiber distribution. Medium wall shear rates produce a “rough porcupine” surface, irregular cross section and tubular depletive fiber distribution with fibers depleting at a relative radial positionr/Rof 0.63 and accumulating at the surface and the axis. This is exactly opposite to the tubular pinch effect observed for neutrally buoyant rigid spheres which accumulate atr/Rof 0.63 and deplete at the surface and the axis. High wall shear rates give a “shorn porcupine” surface, rounded or distorted polygonal cross section and radial migration of fibers toward the axis. The extant of disorder decreases with increasing pseudoplasticity, of the fluid, suggesting that the characteristic fiber orientation, distribution and transitions arise from normal stress effect and/or the eccentric rotation of fibers dictated by the complex velocity profile of the flowing fluid. These phenomena have not been pr

ISSN:0032-3888    

DOI:10.1002/pen.760190907

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractAn analysis of fluid transport in a polymer processor consisting of a hollow vertical cylinder with rotating blades is presented. The action of the rotating blades causes a thin film to be deposited on the inner surface of the processor and a bow wave to form in front of the blade. Fluid transport through the processor depends upon flow within the bow wave. Three types of flows are identified as contributing to the fluid transport: flow under the influence of a pressure gradient, flow due to gravitational force, and drag flow due to the action of the rotating blades. Equations describing these flows are derived as well as an equation for the bow wave profile. Experimental data in good agreement with the theoretical development are presented.

ISSN:0032-3888    

DOI:10.1002/pen.760190908

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760190901

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY