Microhardness and density distributions in polymeric powder compacts

Crawford, R. J.; Paul, D.; Adeebnia, Y.

doi:10.1016/0014-3057(80)90145-7

Cited by 18 publications

(4 citation statements)

References 10 publications

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“…Although a few published works deal with the compaction of polymer powders [1–3, 5, 8–12], or with the sintering of polymers [3, 8, 13–17] including PTFE [4, 5, 9, 18–20], to the authors' knowledge, the work presented in this article is one of the first published studies dedicated to the qualitative identification of the different strain mechanisms, which are responsible for the macroscopic deformations developed during the sintering heat treatment of compacted PTFE powder. This work should constitute the first step of a study the aim of which is to build a predictive model of the deformations of PTFE parts during their manufacturing process, to better control this compaction and sintering process and, ultimately, to predict the physical and mechanical properties at each point of the parts before their use.…”

Section: Introductionmentioning

confidence: 99%

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Canto

Schmitt

Carvalho

et al. 2011

Polymer Engineering & Sci

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The influence of the cooling rate after melting on the crystalline weight fraction of pure poly(tetrafluoroethylene) (PTFE) was derived from differential scanning calorimetry tests. Specimens made of pure or filled PTFE were manufactured by isostatic or constrained uniaxial cold pressing, up to different values of the porosity. Dilatometry tests were carried out on these specimens while imposing various heating–cooling treatments. The deformations recorded during these tests strongly depend on the mode and level of compaction. The original procedures presented, herein, made it possible to identify that these macroscopic deformations, which are strongly anisotropic for uniaxially pressed specimens, result from the combination of different independent mechanisms. The mechanisms that were distinguished are reversible thermal expansion, void closure, crystalline to amorphous and vice versa transformations, and recovery, which were not observed for isostatically pressed specimens. It was also shown that, after being subjected to a standard sintering treatment, anisotropically pressed specimens still exhibit anisotropic crystallization strains. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

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Section: Introductionmentioning

confidence: 99%

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Canto

Schmitt

Carvalho

et al. 2011

Polymer Engineering & Sci

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“…Crawford et a1. 23 have established a direct relationship between density and microhardness in polyvinylidenechloride compacts although the nature of the relation was dependent on the compaction conditions. These results are similar to those reported for metallic powders .24-26.…”

Section: Particle Morphologymentioning

confidence: 96%

Solid state processing of polymers: A review

Jog

1993

Adv Polym Technol

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mThe solid state processing technique is used for processing of a variety of polymers such as ultra high molecular weight polyethylene, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyether etherketone, and polyphenylene sulfide. The solid state processing involves cold compaction of polymeric powders followed by sintering at temperatures above their melting point. The properties of such products are influenced by the powder characteristics and a number of process parameters encountered during the compaction and sintering processes such as compaction pressure, rate of compaction, sintering temperature, and time. The understanding of the physical processes involved in solid state processing of polymers is essential for defining the parameters to obtain the product with desired properties. In this review, the various aspects of solid state processing are discussed with reference to the physical processes. 0 1993 John Wiley & Sons, Inc.

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“…Also, the operation of an extruder or injection-molding machine Th interest in a number of fields. Recent studies (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) depends on a positive pressure at the inlet port to the barrel. This pressure is caused by the head of powder in the feed hopper and, since the pressure gradient is not linear, it is desirable to have information about the magnitude of the pressure drop due to frictional effects.…”

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confidence: 99%

Effect of compaction rate during the cold forming of polymeric powders

Crawford¹

1982

Polymer Engineering & Sci

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During many plastics processing methods, both conventional and novel, plastic powders or granules are subjected to pressure. The pressure transmissibility through the powder has an important effect on the success and efficiency of the process, and so it is desirable to be able to predict the pressure at any point from a knowledge of the applied pressure and the geometry of the system. To examine this pressure transmissibility effect, poly(vinylidene chloride) powder has been compacted in a metal die under different rates using either load or displacement control. It has been found that rate effects are particularly important for loading rates greater than 8 MPa/s and displacement rates greater than 7.5 mm/s. The ratio of transmitted pressure (P2) to applied pressure (P1) has been measured for a range of compact geometries, and it has been found that the ratio is approximately constant during the latter stages of the compaction process. Various laws for predicting the transmitted pressure have been studied, but it has been found that the simplest equation that agrees with the data is of the form

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Microhardness and density distributions in polymeric powder compacts

Cited by 18 publications

References 10 publications

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Solid state processing of polymers: A review

Effect of compaction rate during the cold forming of polymeric powders

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