Study of sintering of poly(methyl methacrylate)
01 Aug 1970-Journal of Applied Polymer Science (Wiley Subscription Services, Inc., A Wiley Company)-Vol. 14, Iss: 8, pp 2069-2077
TL;DR: In this article, the authors studied the sintering of poly(methyl metacrylate) spheres to the blocks of the same material at temperatures ranging from 127° to 207°C and found that the predominant mechanism responsible for this process is non-Newtonian viscous flow.
Abstract: Sintering of poly(methyl metacrylate) spheres to the blocks of the same material was studied at temperatures ranging from 127° to 207°C. The analysis of the data based on the empirical Ostwald relation indicates that the predominant mechanism responsible for this process is non-Newtonian viscous flow. The type of the flow changes with temperature of sintering, being pseudo-plastic at lower temperatures and tending to dilatancy at higher ones.
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TL;DR: Recently, non-invasive techniques, such as direct nonradiative energy transfer, atomic force microscopy, small angle neutron scattering, environmental scanning electron microscopy and various optical techniques have greatly enhanced the study of these stages as discussed by the authors.
Abstract: Latex film formation, the process by which an aqueous dispersion of polymer particles is transformed into a continuous material, has a direct bearing on the final film morphology and properties. Each of the primary stages of film formation (evaporative drying and ordering; particle deformation; and polymer interdiffusion) have been studied experimentally. Recently-developed non-invasive techniques, including direct nonradiative energy transfer, atomic force microscopy, small angle neutron scattering, environmental scanning electron microscopy, and various optical techniques have greatly enhanced the study of these stages. Even so, the exact cause (or causes) of particle deformation is still a topic of considerable debate. Several factors are experimentally known to influence latex film formation: the ambient conditions; the presence of surfactants, plasticizers and pigments; and latex particle structure. An important aim in the study of latex film formation is to understand the mechanisms by which these and other factors affect the process. New challenges lie in the study of film formation of core-shell latices, latex blends and new compositions.
520 citations
26 Oct 1998
TL;DR: In this paper, the dependence of electrical constriction resistance on the shape and dimensions of /spl alpha/spots and on the magnitude of the mechanical contact load was examined and the range of validity of the classical voltage-temperature relation for electrical contacts was also examined.
Abstract: The paper reviews the dependence of electrical constriction resistance on the shape and dimensions of /spl alpha/-spots and on the magnitude of the mechanical contact load. The range of validity of the classical voltage-temperature relation for electrical contacts is also examined. The paper describes experimental evidence of breakdown of the classical electrical contact theory when /spl alpha/-spots become too small. One of the interesting and useful properties of relatively small /spl alpha/-spots is that they are subject to large surface stresses. These stresses induce /spl alpha/-spot growth.
223 citations
Cites methods from "Study of sintering of poly(methyl m..."
...From the work of Kuczynski et al. [ 39 ], it can be shown that if sintering between two spheres is controlled by the creep law given by (18), the neck radius increases with time according to...
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TL;DR: In this article, experiments were conducted using pairs of particles inside a hot stage microscopy setup with the ultimate objective to study the coalescence, which is a crucial stage in the rotational molding process.
Abstract: Experiments were conducted using pairs of particles inside a hot stage microscopy setup with the ultimate objective to study the coalescence, which is a crucial stage in the rotational molding process. It was found that the geometry of the particles had no significant effect on the sintering rate. The sintering rate increases as the viscosity of the resin decreases. However, this effect became less important as the particle size decreased. The experimental results of this study have been compared with the available mathematical models based on balance of viscous and surface tension forces. The model developed by Frenkel and a corrected version by Eshelby predict a faster coalescence than observed experimentally. However, Hopper's model is in relatively good agreement with the present experimental data. Yet there is evidence that mechanisms other than Newtonian viscous flow may play a role in polymer sintering.
181 citations
TL;DR: In this paper, a mathematical model describing the complete polymer sintering process for viscoelastic fluids has been developed based on the approach was similar to that of Frenkel (1945) and the convected Maxwell constitutive equations were used together with the quasi-steady state approximation.
Abstract: An experimental study for polymer sintering has been carried out using pairs of powder particles. Although in many cases Newtonian sintering models successfully describe polymer sintering, they predict a faster coalescence rate than that observed with the polypropylene copolymer resins used in this study, indicating that factors other than the surface tension and the viscosity play a role in polymer sintering. Observations of coalescence under the microscope and rotational molding experiments suggest that melt elasticity slows down the process. Based on these findings, a mathematical model describing the complete polymer sintering process for viscoelastic fluids has been developed. The approach was similar to that of Frenkel (1945) and the convected Maxwell constitutive equations were used together with the quasi-steady state approximation. The proposed viscoelastic sintering model is capable of predicting the sintering rate slowdown observed in this study.
164 citations
Cites background from "Study of sintering of poly(methyl m..."
...However, based on experimental results, many authors have suggested that the Newtonian viscous flow mechanism may not adequately represent polymer sintering (Lontz, 1964; Kuczynski et al., 1970; Siegmann et al., 1986; Mazur and Plazek, 1994; Barnetson and Hornsby, 1995)....
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TL;DR: In this paper, a powder prepregging process suitable for the manufacture of high-quality powder-impregnated tapes and their subsequent consolidation to make void-free composite parts is discussed.
Abstract: The use of thermoplastic composites has been limited by the lack of reliable techniques to make prepregs of consistent quality. Dry powder impregnation methods offer a new approach to the solution of this problem. This paper discusses the features that are essential to the development of an acceptable dry powder process The physical principles that govern the manufacture of thermoplastic prepreg tapes of controllable fiber-matrix volume fractions and the consolidation of these tapes to make void-free composite parts are presentedA novel powder prepregging process suitable for the manufacture of high-quality powder-impregnated tapes and their subsequent consolidation to make void-free parts is discussed. It is shown that a well-designed dry powder process can achieve fine control over both fiber-matrix composition in the prepreg tape and intimate wetting between in dividual fibers and the thermoplastic matrix Powder prepreg tapes can be consolidated into void-free specimens with simple consolidation cycles...
100 citations