摘要:

The PVC-powder kernel contains aggregates of different orders of magnitude, whose shape and size depend on type and conditions of polymerization.

ISSN:0022-2348    

DOI:10.1080/00222347708212904

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Dr. J. Chauffoureaux (Solvay, Brussels, Belgium): Professor Menges will speak first about research now being carried out in Aachen. Dr. Avenas will talk about calendering and other work he is doing at the Ecole des Mines de Paris. Finally, Dr. Gould will discuss the relationship between processing and the fatigue properties of PVC.

ISSN:0022-2348    

DOI:10.1080/00222347708212905

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Using a power-law viscosity, then connecting power-law fluid and thermo-dependence of the viscosity, we compute the applied stresses between the rollers during calendering (pressure curve-maximum pressure and shear stress-roll separating force and the applied opposing torque) as well as the temperature evolution of the polymer in the contact. We checked this model by measuring r (ratio of spread height to nip width), the power consumed by the roll of the calender, the roll separating force, and the torque on a simulation apparatus.

ISSN:0022-2348    

DOI:10.1080/00222347708212906

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Major types of defects appearing in calendered films and sheets are described. The conditions for the appearance of air bubbles and mattness were studied for the particular case of calendering crystal-clear, rigid, toughened PVC. A correlation was found between the presence of air bubbles in the film and a distribution of air inclusions in the bank. The existence of air inclusions is also related to a critical pressure, which has been calculated with the aid of a theoretical model (pseudoplastic fluid). The variation of mattness with various parameters of the calendering process, such as speed, friction, temperature, and lubrication, was measured on a laboratory calender. The influence of the calender size (laboratory and industrial) on the occurrence of mattness was also investigated. The calculated critical parameters to be considered, in order to define the onset of mattness, appear to be a shear stress or a maximum pressure. A comparison of model calculations and experimental observations allows the definition of appropriate boundary conditions for calendering a given PVC compound as a function of calender size.

ISSN:0022-2348    

DOI:10.1080/00222347708212907

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Structure-property relationships were investigated for blends of grafted rubbery polymers with PVC. Increasing grafting levels as well as higher blending temperatures improved the dispersion of the graft copolymers in PVC, lowered the impact strength, and reduced stress whitening. Presuming a mechanistic connection between impact strength and stress whitening, the causes of whitening due to mechanical deformations were studied by a variety of methods. Electron microscopy of stress-whitened zones revealed a large number of cavities formed by rupture of rubber particles, which correlated with the extent of whitening. Density measurements and quantitative evaluations of the volume increase due to the cavities in the stress-whitened zones were in agreement and proved that crazing did not significantly contribute to either volume dilation or stress-whitening. Light scattering studies indicated the existence of reflecting planes oriented at an angle of 55 to 64° to the direction of the applied stress, depending on the particle size of the modifier in the blends. The orientation of the scattered light could not be attributed to the cavities in the rubber particles because of their smallness (< 0.5 μm). An explanation was finally found by transmission light microscopy at various resolving powers. It was demonstrated that the ruptured rubber particles were accumulated in bands which corresponded to shear bands in the PVC matrix. Thus it was concluded that the rubber particles improved the impact strength of PVC by initiating shear bands and not by generating crazes.

ISSN:0022-2348    

DOI:10.1080/00222347708212908

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Good mixing of the raw material and the various additives is a prerequisite to satisfactory quality of the product. Five screws with different geometrical dimensions were tested in combination with different cylinders. Excellent mixing efficiency could be achieved by combining the screws with a pinned cylinder with mixing pins reaching nearly to the bottom of the melt channel.

ISSN:0022-2348    

DOI:10.1080/00222347708212909

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A prototype injection-molding machine with a melting system created by shearing between coaxial cylinder and cone (capacity 10 g) is presented. Its ability to process two PVC samples with viscosity number in solution of 80 (for injection) and 115 (for extrusion) is discussed. Correct melting of the sample was determined by testing the solution properties in acetone and from the elongation at break. The output rate is 9 kg/hr at 215°C without degradation for the first PVC and 2.3 kg/hr at 220-320°C without degradation for the second PVC.

ISSN:0022-2348    

DOI:10.1080/00222347708212910

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The processing properties of a rigid PVC compound with various amounts of different lubricants were studied with a torque rheometer. The plasticizing behavior was measured in a mixer and recorded as torque versus time. The fusion time and the torque at fusion and of the molten material were evaluated. The compounds were extruded with a laboratory extruder and a capillary die. The torque of the screw, the melt pressure, and temperature in the barrel and the die and the output were measured. The shear stress and shear rate were calculated from these results. The lubricants, one paraffin and five polyethylenes, had molecular weights of 700 to 3500. The dependence of the processing behavior on the molecular weight of the lubricants is discussed. There is no single value which can be given but numerous interdependent parameters can be used to obtain a prediction of the processing properties of the material.

ISSN:0022-2348    

DOI:10.1080/00222347708212911

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A highly efficient stabilization system has been developed for asbestosreinforced rigid PVC compounds. With this stabilization system, direct extrusion of rigid PVC/asbestos sheets, pipes, and other profiles as well as injection molding are possible. The present article summarizes data on dynamic heat stability of asbestos/rigid PVC compounds as a function of PVC polymerization method (suspension and bulk) and molecular weight; asbestos loading, source, fiber length, and iron content. Typical mechanical and thermal properties at two asbestos loadings are also reported.

ISSN:0022-2348    

DOI:10.1080/00222347708212912

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Dr. J. Chauffoureaux (Solvay, Brussels, Belgium): I suggest that we start the discussion with the problems related to the modification of the structure of PVC during processing. What happens in a singlescrew extruder o r in a twin-screw extruder? What a r e the influences of the particle structure of the PVC polymer and of additives on the fusion o r the gelation during processing?

ISSN:0022-2348    

DOI:10.1080/00222347708212913

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor