摘要:

AbstractModels of chain addition polymerizations have been analyzed for effects of reaction parameters on thermal behavior during reaction and, consequently, on properties of the polymer formed. Emphasis was placed on the investigation of thermal drift phenomena in particular. Several dimensionless parameters were identified and their role in predicting thermal behavior was established.

ISSN:0032-3888    

DOI:10.1002/pen.760141102

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractZirconium compounds dispersed in polymers often bond the polymer molecules together, increasing their stability. This can generally be attributed to the formation of covalent bonds between zirconium atoms and small atoms of high electronegativity of the polymer molecule, to overlapping of pi orbitals of unsaturated moieties of the organic compound with sigma orbitals of the zirconium atoms, to fractional bond formation between zirconium and organic hydrogen, and to combinations of these. Bonding and its effects on physical properties have been achieved by molecular dispersions of zirconium compounds in the polymer, by dispersion of insoluble particles of zirconium compounds, and through residues from zirconium catalysts used in polymer preparation. Coatings and plastic components have been improved in strength and in durability by the dispersions. Compounds of other metals often perform similarly. The totality of relevant properties of zirconium compounds often leads to their preferential use.

ISSN:0032-3888    

DOI:10.1002/pen.760141103

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe flux models can be used to accurately predict the transmission or absorption of radiant energy through an absorbing scattering plastic. The apparent absorbing and scattering coefficients are dependent upon the physical characteristics of the body and the incident radiation as well as the actual absorption and scattering coefficients of the material. The apparent interfacial reflectivity can be estimated from the degree of scattering within the material.

ISSN:0032-3888    

DOI:10.1002/pen.760141104

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractPolymer properties were measured as a function of temperature at 5 and 10°C per minute heating rates and as a function of time at constant temperature, using the Du Pont 940 thermal‐mechanical analyzer. Data are reported on deflection temperature under load, vicat softening temperature, and creep properties. These results have been correlated with ASTM values. These tests require short times and are applicable to thermoplastics, thermosets, and elastome

ISSN:0032-3888    

DOI:10.1002/pen.760141105

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractPlastics injection molding is a complex, multi‐variable process which has not yet been clarified. The hardware controller is difficult to build without a realistic mathematical model. One powerful technique for solving such a difficulty is to employ digital control technology which can utilize sophisticated control strategies in order to optimize the system performance. Machine operation and resultant production can be tightly controlled by using computer monitoring, data storage and data logging. This paper presents elements of the various problems that process engineers may encounter in designing a computer‐controlled system for plastics injection‐molding machinery. The variables of the process and a functional analysis of process control are discussed. A hardware system design; including specification of computer, selection of peripheral devices, system design, and input/output interfacing; is pres

ISSN:0032-3888    

DOI:10.1002/pen.760141106

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA rheological investigation of the saturated fatty acids as lubricants for PVC was made in a Sieglaff‐McKelvey rheometer over a wide temperature range. Results reveal that with an increase in carbon chain, fatty acids became more effective in reducing the melt viscosity of PVC. It was also discovered that the maximum viscosity variation due to these materials was observed at 350°F. At test temperatures of 400°F and above, no major viscosity differences were observed. Furthermore, the changes in the melt viscosity were more pronounced at shear rates less than 200 sec−1. The usefulness of the measured viscosity variations at the critical test temperature of 350°F was shown by extrusion. An excellent correlation between the apparent melt viscosity and extrusion melt temperature was found. The criticalness of the test temperature in assessing the effect of lubricants on PVC flow is dis

ISSN:0032-3888    

DOI:10.1002/pen.760141107

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractElectron microscopy studies indicate that the microfibrils are a well defined element of many uniaxially oriented polymers. On the basis of these results it was inferred that the mechanical responses of uniaxially oriented polymers are similar to those of a parallel ensemble of the microfibrils. An important consequence of this microfibrillar model is that the type of load transfer is independent of crystallite aspect (length/diameter) ratio. The analysis of anisotropy in modulus of uniaxially oriented nylon 6, however, indicates that the load transfer characteristics of these polymers are dependent on crystallite dimension. A series response is observed only with fibers or films of low and intermediate draw ratio. Highly oriented structures, however, exhibit a nearly isotropic response in load transfer. These results show that uniaxial polymers must be analyzed in terms of a model where the crystallites are embedded in an “amorphous” matrix. The equations are derived for modulus, strength, and coefficient of diffusion in terms of crystallite dimensions, and the results compared with the experimental d

ISSN:0032-3888    

DOI:10.1002/pen.760141108

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe steady shear viscosities of high density polyethylene disolved in highly branched isoparaffin solvents have been measured with a high‐pressure autoclave viscometer at temperatures ranging from 150 to 250°C and over a range of shear rates from 0.02 to 170 sec−1. Laboratory measurements on solutions ranging from 15 to 67 wt percent polymer were used to develop and calibrate a mathematical model for solution viscosity intended for a range of from 10 to 100 wt percent polymer. The foundation for the model consists fo two equations: the modified Martin equation is used to describe the effect of concentration, and the Sabia equation is used to describe pseudoplastic behavior. The model correlates viscosities that can range over nine orders of magnitude with sufficient accuracy for most process design work, averaging less than 10 percent error. Both the data and the model indicate that at constant stress the activation energies (EA) for the effect of temperature on viscosity are higher for solutions in the midrange of composition than for either of the pure components. This peak inEAis related to the density difference between polymer and sol

ISSN:0032-3888    

DOI:10.1002/pen.760141109

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA theory is presented which describes the dynamics of blade‐coating of a viscoelstic fluid onto a moving sheet. The method begins with the usual “lubrication” approximation, and develops the solution as a perturbation about the Newtonian case. Viscoelasticity is described by an empirical constitutive equation which shows non‐Newtonian viscosity and finite normal stress behavior consistent with typical observations of polymeric fluids. Theoretical results indicate a small increase in coating thickness due to departure from Newtonian behavior, and a significant decrease in the magnitude of the pressure developed under the blade. Consequently, the blade loading can be reduced significantly by viscoelastic effects. The results for the loading may be an artifact of the specific constitutive model, since it can be shown that some viscoelastic fluids, specifically an “elastic Newtonian” fluid, would exhibit increased loading relative to the inelastic New

ISSN:0032-3888    

DOI:10.1002/pen.760141110

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA specially‐designed mold with interchangeable cavity plates was built and used with an Instron capillary rheometer, type MCR, to investigate the injection molding process. Flow patterns in the mold cavity were illustrated with a visual tracer technique. The complete deformation history of the tracers was recorded on a motion picture for several runs. The flow patterns provide data for computing the components of the rate‐of‐deformation tensor which is used to identify specific shear and extensional flows. The tracer marks in the cross section of a molding offer information on the skin thickness and the dimensions of the core ch

ISSN:0032-3888    

DOI:10.1002/pen.760141111

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY