Physical and mechanical characterization of oriented polyoxymethylene produced by die-drawing and hydrostatic extrusion

Mohanraj, J.; Bonner, Mark; Barton, D.C.; Ward, I. M.

doi:10.1016/j.polymer.2006.05.056

Cited by 24 publications

(36 citation statements)

References 34 publications

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“…Figure 7 also shows the 2Θ vs scattering intensity plots from the (100) plane for POM and POM/HAp nanocomposites after injection moulding. The intensity of the reflections from the (100) plane changes with the HAp content in samples because of the change in the degree of crystallinity [25][26][27]. For T2 copolymer the highest intensity was observed for pure POM and it decreases with an increase of HAp content.…”

Section: Resultsmentioning

confidence: 99%

The influence of molecular weight on the properties of polyacetal/hydroxyapatite nanocomposites. Part 1. Microstructural analysis and phase transition studies

Pielichowska

2012

J Polym Res

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In this work the influence of molecular weight of three polyoxymethylene (POM) copolymers on the properties of (POM)/hydroxyapatite (HAp) nanocomposites for long-term bone implants have been investigated by various physicochemical methods. Electron microscopy observations confirmed uniform dispersion of HAp in the polymer matrix, whereby DSC results show that HAp influences the degree of crystallinity of POM matrix. Temperature modulated differential scanning calorimetry (TMDSC) was applied to study the melting and recrystallization processes of POM matrix-it was found that with decreasing of POM molecular weight the amout of reversible melting increases. WAXD results show no shift in 2θ for pure POM copolymers and all POM/hydroxyapatite nanocomposites, indicating that the addition of HAp does not change the hexagonal system of POM. For all three copolymers, Young's modulus increases with increasing hydroxyapatite concentration, whereby elongation at break decreases. On the contrast, HAp concentration does not have a significant influence on the tensile strength.

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Section: Resultsmentioning

confidence: 99%

The influence of molecular weight on the properties of polyacetal/hydroxyapatite nanocomposites. Part 1. Microstructural analysis and phase transition studies

Pielichowska

2012

J Polym Res

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“…However, it is noted that the degrees of molecular and crystal orientation are much lower than those in the hot rolling POM films 27 and die-drawing POM samples. 28 This could be related to imperfect fiber orientation. As shown in Figure 2a, there are always some parts of the fibers which are not aligned along the direction of stretching in the stretched electrospun mat, even at high elongation.…”

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confidence: 99%

High-Elongation Fiber Mats by Electrospinning of Polyoxymethylene

Zhang

Xiang-zhong

et al. 2008

Macromolecules

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Electrospinning is a recently explored simple and versatile fabrication technique for producing nano-to microscale fibers. The electrospun fiber mats possess a number of characteristics such as high specific surface area, high aspect ratio, and high porosity as a result of random deposition of the fibers, which allow a wide range of potential applications such as optoelectronics, sensor technology, catalysis, filtration, and medicine. 1,2 The mechanical properties of the electrospun fibers or mats are usually different from those of the corresponding bulk materials. Sometimes, the difference is enormous and surprising. [3][4][5] For example, Gu et al. 4 reported a Young's modulus of 50 GPa for polyacrylonitrile single nanofibers, which is much greater than that of the corresponding cast film (1.2 GPa). Kim et al. 5 observed the phenomenon of "necking" with poly(methyl methacrylate) (PMMA)/montmorillonite nanocomposite electrospun single fibers, whereas PMMA is known as a brittle plastic.Polyoxymethylene (POM) is a versatile engineering plastic. 6,7 It is widely used in automobile and electronic industries due to good properties such as good strength, stiffness, abrasion, and chemical resistance. 8,9 Although almost 100 polymer solutions or melts have been electrospun into fibers, 4 to the best of our knowledge, electrospinning of POM has not yet been reported due to presumably poor solubility in common solvents. However, POM is soluble in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), which is frequently used in electrospinning of natural biopolymers such as collagen and chitin. [10][11][12][13] In this work, electrospinning of POM solutions in HFIP is investigated, and to our surprise, a very high elongation to break was observed with the POM electrospun fiber mats. Figure 1 shows the morphology of the electrospun POM mat obtained from a 5 wt % solution at 30°C with a relative humidity of 40%. The average diameter is 940 nm, and microporous structure was observed with an average pore size of 150 nm. It is well-known that microporous structure is frequently obtained when volatile solvents are used for electrospinning, 14,15 and that high relative humidity also favors formation of pores. 1,16 HFIP is a volatile solvent with a boiling point of 58°C. The formation of microporous structure in the current case is understandable, although the electrospun fibers of biopolymers reported so far have no obvious pores. [10][11][12][13] The mechanical properties of the nonwoven POM electrospun mats were measured by tensile tests after thorough drying at 40°C under vacuum, and a typical load-elongation curve is shown in Figure 2a. Elongation of 460% was observed. For comparison, the elongation at break of bulk POM such as a tensile bar obtained from injection molding is known to be 40-50%, 9 and that of the thin film cast from the same solution used for electrospinning is only 1%. Therefore, the elongation at break of the electrospun nonwoven mat is about 10-fold of that of the bulk tensile bar and about 460-fold of that of the...

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“…Since then numerous works have been reported on the hydrostatic extrusion of both semi-crystalline and amorphous polymers. In this process, the billet is forced through the die by the pressurized hydraulic fl uid as shown in Figure 4.5 [63]. Hydrostatic extrusion was successfully adapted to many thermoplastics, covering not only semi-crystalline (PE, PTFE, PP, PET, POM, and PA) but also amorphous polymers (PMMA) [64,65].…”

Section: Solid-state Extrusionmentioning

confidence: 99%

“…In this processing technique, the deformation takes place with no net tensile stress, and the fl ow stress increases due to strain hardening at high degrees of plastic strain and also due to the eff ect of the hydrostatic component of stress. Increasing the extrusion pressure is then counterproductive and the fl ow stress rises to the point where the extrusion rate is negligible and in practical terms no further increase in pressure is benefi cial [63]. Substantial chain orientation is forced, leading to greatly improved physical properties such as signifi cantly increased transparency with crystalline polymers, elevated melting point, lower permeability and diff usion rate, enhanced chemical resistance, increased thermal conductivity along the extrusion direction and increased resistance to indentation and wear [66].…”

Section: Solid-state Extrusionmentioning

confidence: 99%

Polyoxymethylene Processing

Pielichowska¹

2014

Polyoxymethylene Handbook

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In this chapter major issues of polyoxymethylene (POM) and its nanocomposites processing are presented. Diff erent processing methods-injection molding, extrusion, blow molding, melt blowing, compression molding, rolling, sintering and spinning-as well as fabrication of highly oriented products, waste recycling, machining and assembling of moldings and semi-fi nished parts are described in regard to POM, which is an important engineering polymer used as structural material in all industrial sectors. However, processing of POM requires special attention since this polymer undergoes facile decomposition with evolution of formaldehyde. Some of the processing methods are for POM at infancy stage, such as electrospinning, due to poor solubility of this polymer in common solvents. Only recently has the successful electrospinning of polyoxymethylene nanofi bers with porous surface using a hexafl uoroisopropanol (HFIP)-based solvent been reported on. Polyoxymethylene types include impact modifi ed, fi lled and reinforced polymers in a wide range of sorts-this diversity may cause some problems during recycling by recompounding and remelting where extensive POM decomposition should be avoided because of formaldehyde release.

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Physical and mechanical characterization of oriented polyoxymethylene produced by die-drawing and hydrostatic extrusion

Cited by 24 publications

References 34 publications

The influence of molecular weight on the properties of polyacetal/hydroxyapatite nanocomposites. Part 1. Microstructural analysis and phase transition studies

The influence of molecular weight on the properties of polyacetal/hydroxyapatite nanocomposites. Part 1. Microstructural analysis and phase transition studies

High-Elongation Fiber Mats by Electrospinning of Polyoxymethylene

Polyoxymethylene Processing

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