ISSN:0193-7197    

DOI:10.1002/vnl.730130102

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA review of relevant microscopic processes, both chemical and physical, which occur during suspension, bulk and emulsion polymerization (both before and after pressure drop) is given. The state of the art of kinetic modelling of monomer consumption rate, reactor pressure, molecular weight and short and long chain branching development and polymer chain microstructure is illustrated. The effects of diffusion‐controlled termination and propagation reactions and the significant decrease in initiator efficiency and decomposition rate constant at high monomer conversions on the relative rates of various chemical reactions are discussed. The application of temperature programming and semibatch operation are emphasized. Finally, attempts to model polymer particle morphology are describe

ISSN:0193-7197    

DOI:10.1002/vnl.730130103

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractProper choice of a suspending agent will help the PVC manufacturer achieve control of resin particle size, particle size distribution, and resin bead porosity. The results of research work at Dow has revealed that certain properties of cellulsoe ethers (a hydroxypropyl methylcellulose ether structure) are useful in helping control the properties of the PVC resin. In vinyl chloride polymerizations, cellulose ethers act as both an emulsifier; and during the polymerization, as a protective colloid to prevent excessive coalescence of the monomer droplets. The average particle size of the organic droplets in the aqueous phase during the PVC polymerization reaction is a function of the interfacial tension, intensity of agitation, viscosity of the two phases, and the volume fraction of the dispersed phase. The average particle size of the PVC resin was found to be a direct function of the interfacial tension multiplied by the 0.2 power of the gel strength of the cellulose ether solution. The interfacial tension of the cellulose ether solution/organic interface is probably the most important factor in determining the resin particle size. Particle size distribution widens with an increase in interfacial tension. Resin bead porosity is also important and is directly related to the solubility of the cellulose ethers in the organic phase. This observation supports the proposed seed stabilization theory that can explain the formation of a porous resin bead. The use of a proper suspension agent like cellulose ethers with or without a secondary surfactant will help control important properties of the PVC resin product. Control of the average molecular wight, degree of substitution, and grouping distribution on the cellulose chain of the cellulose ether suspension agent (all of which affect interfacial tension) is important for the PVC manufacturer.

ISSN:0193-7197    

DOI:10.1002/vnl.730130104

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractTriaryl and alkylaryl phosphates are plasticizers/flame retardants for polyvinyl chloride. The former are more effective flame retardants and the latter are better plasticizers. The latter also gives less smoke. A new phosphate ester blend with good plasticizer properties and low smoke is reported. A brominated triaryl phosphate ester is shown to be a highly effective flame retardant giving plasticized polyvinyl chloride compositions with oxygen index values up to 36. These compositions are suitable for high temperature wire and cable products.

ISSN:0193-7197    

DOI:10.1002/vnl.730130105

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractWeathering characteristics of the PVC compounds used for exterior applications, such as house siding, window and door frames, must be determined in order to predict their performance in actual use. In this study color weatherability of various PVC compounds, determined in the QUV accelerated weatherometer, was compared to the outdoor exposure in Arizona, Ohio, and Florida. The effect of the compound base formulation and color on correlation of the QUV to the outdoor weathering has been also analyzed.

ISSN:0193-7197    

DOI:10.1002/vnl.730130106

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractHistrorically, the measure of thermal performance on given PVC compositions has been approximated by the metal content of the chosen heat stabilizer. However, advances in tin and ligand chemistry necessitate the evaluation of thermal stabilizers on criteria other than metal content. Many factors including the nature of the metallic species and relative activity of the organic ligands must be considered. A discussion will be given on the facets of heat stabilizer compositions and their effects upon PVC formulations and processing. Performance criteria for organotin stabilizers. The take‐home point will be that tin content alone, in most formulations, is not the most important determinant in PVC heat stabilizer effectivenes

ISSN:0193-7197    

DOI:10.1002/vnl.730130107

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractProfitable production and sale of rigid PVC water pipe is difficult even in the best of economic times. The industry is intensively cost driven. The development of lower cost formulations is, therefore, of great interest.Conventional pressure pipe formulas do not provide sufficient hydrostatic strength when calcium carbonate filler levels exceed 5 parts per hundred resin (phr). This paper will describe the development of a pressure pipe formulation which contains up to 10 phr filler while maintaining physical properties exceeding all of the required minimum standards.The presentation will include the physical property testing required to develop the formulation including cell classification and long‐term hydrostatic design stress tests. These will be contrasted with data obtained from conventional formulas containing 10 phr of fillers.The quality of commercially extruded pressure pipe made with the new formula will be discussed as a function of raw material selection, blending, and extrusion condition

ISSN:0193-7197    

DOI:10.1002/vnl.730130108

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe hierarchical structures in PVC are such that the larger structures formed during polymerization are broken down to smaller structures during processing. These smaller structures have properties dependent on their microstructure. While PVC's microstructure is mostly amorphous, it contains crystallites that act as physical crosslinks connected together by tie molecules. The microstructure is extended to a larger three dimensional structure by melting during processing followed by recrystallization upon cooling. The strength of this larger three dimensional structure is interpreted from the roughness of extrudate from a zero land length die. This visual method is more sensitive for detecting large three dimensional network structure than measuring capillary entrance pressures, especially for very weak three dimensional structures. Both higher processing temperatures and higher molecular weight PVCs contribute strength to this three dimensional structure which plays a large role in determining lzod impact and stress rupture. Plasticized PVC has a structure similar to rigid PVC as judged by the roughness characteristics of its extrudate. In this case, the plasticizer is soluble in the amorphous phase leaving the crystallites intact.

ISSN:0193-7197    

DOI:10.1002/vnl.730130109

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractExcessive distortion, warpage, and sagging resulting from heat generation by electrical components and transporting environments has limited the penetration of PVC into high flow injection molding applications such as business machine, appliance, and electrical housings. High flow PVC formulations lose their rigidity at temperatures typical of these applications because the application temperatures are very close to the glass transition temperature (Tg) of PVC. In addition, thermal stresses built in during processing relax near theTgof the material. Adding a glutarimide acrylic copolymer increases theTgof PVC; consequently, raising the temperature at which the PVC/glutarimide copolymer blend loses its rigidity well above required application temperatures. This paper describes the effect of adding a glutarimide copolymer on the heat distortion properties and other physical and rheological properties important to high flow injection molding applications.

ISSN:0193-7197    

DOI:10.1002/vnl.730130110

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractCompositions based on PVC, containing DIDP or TOTM plasticizers, and in several cases also containing chlorinated polyethylene (CPE) as property modifier, have been crosslinked by irradiation, using di‐ and tri‐functional acrylic crosslinking agents. Crosslinking effectiveness has been analyzed by solvent swelling data, and the effects of irradiation up to dosages of about 10 Mrad on the mechanical properties of the systems have been recorded. The interaction potential of components used in these systems has been determined by recently‐developed methods of inverse gas chromatography (IGC). These classify PVC and CPE as electron acceptors, and the plasticizers as donors. Expectedly, increased moduli and decreased elongational properties follow exposure to gamma‐rays. The plasticizers reduce the effectiveness of crosslinking, the magnitude of the reduction being related to the degree of acid/base interaction between PVC and plasticizing fluids. When present, CPE competes with PVC for plasticizer so that for given quantities of DIDP or TOTM, the fraction available to solubilize the host polymer is reduced. In compounds with CPE, therefore, the crosslinking effectiveness of irradiation is raised, consistent with the acid/base balance of interactions, as given by the IGC results. Twin yield points have been observed in the stress‐strain curves of compounds containing CPE. It is postulated that distinct, interpenetrating crosslink networks are formed when these polymers are subjected to gamma ir

ISSN:0193-7197    

DOI:10.1002/vnl.730130111

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY