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polymer cross linking

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Published: 15 May 2022
Fig. 6 Cross-linked polymer More
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006915
EISBN: 978-1-62708-395-9
... corresponding to soft-and-weak, soft-and-tough, hard-and-brittle, and hard-and-tough plastics and temperature-modulus plots representative of polymers with different degrees of crystallinity, cross-linking, and polarity. It explains how viscosity varies with shear rate in polymer melts and how processes align...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006925
EISBN: 978-1-62708-395-9
... or no side branching or strong hydrogen bonds (as in nylon) crystallize more easily, whereas crystallization is inhibited in heavily cross-linked polymers and in polymers containing bulky side groups. As noted, amorphous polymers exhibit a T g , when the amorphous regions become mobile. In contrast...
Image
Published: 15 May 2022
Fig. 21 Structure of a phenol formaldehyde. (a) Two phenol rings join with a formaldehyde molecule to form a linear chain polymer and molecular by-product. (b) Excess formaldehyde results in the formation of a network thermosetting polymer due to cross linking. Source: Ref 4 More
Image
Published: 15 May 2022
Fig. 1 Five regions of viscoelastic behavior for a linear, amorphous polymer. Also illustrated are the effects of crystallinity (dashed line) and cross linking (dotted line). More
Image
Published: 15 May 2022
Fig. 1 Variation of elastic modulus with the temperature for a typical amorphous polymer. T g is the glass-transition temperature, and the horizontal dashed line shows the effect of slight cross-linking. More
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006924
EISBN: 978-1-62708-395-9
.... During the curing process, chemical reactions take place that are structured to cause the reactants to polymerize and link together. This results in cross links formed by chemical bonds, resulting in a network structure. In the final fully cured state, the cross-linked network provides desirable...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006931
EISBN: 978-1-62708-395-9
...; the particular state—whether amorphous, semicrystalline, or crystalline; and the nature of any network structure. These elements, by which all polymers can be classified, are illustrated in Fig. 2 and described with examples in Table 1 . Clearly, there should be no network structure or cross-linking...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006920
EISBN: 978-1-62708-395-9
... subsequently with a polymeric alkyl radical to an amino ether ( Fig. 19 ). This amino ether can react with other radicals such as a peroxy radical to form a cross-linked polymer peroxide and regenerate the nitroxy radical, which can react with new alky radicals ( Ref 47 ). This process is catalytic...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006923
EISBN: 978-1-62708-395-9
... to the high degree of molecular motion possible at these temperatures. As temperatures continue above the T g , the modulus of linear amorphous polymer continues to drop off slowly; if the polymer is cross linked, improved rubber elasticity is observed, as shown as a dotted line in Fig. 1 . If the polymer...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006865
EISBN: 978-1-62708-395-9
... structure. In general, polymers that have a reasonably regularly ordered chain structure and little or no side branching will crystallize under suitable conditions. Crystallization is inhibited in heavily cross-linked (thermoset) polymers and in polymers that contain bulky side groups. There are three...
Book Chapter

Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003541
EISBN: 978-1-62708-180-1
... themselves into an orderly structure. In general, simple polymers (with little or no side branching) crystallize very easily. Crystallization is inhibited in heavily cross-linked (thermoset) polymers and in polymers containing bulky side groups. There are three categories of polymers: thermoplastics...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003550
EISBN: 978-1-62708-180-1
... chemicals more readily than crystalline polymers, and the rate varies inversely with the degree of crystallinity. Cross-linked polymers will not dissolve but will swell significantly when exposed to chemicals having similar solubility-parameter values. The impact of these interactions on the mechanical...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006944
EISBN: 978-1-62708-395-9
... the effect of lightly cross-linked material which prevents viscous flow and in turn eliminates the final region. Fig. 1 Variation of elastic modulus with the temperature for a typical amorphous polymer. T g is the glass-transition temperature, and the horizontal dashed line shows the effect of slight...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006782
EISBN: 978-1-62708-295-2
... can appear as discoloration, crazing, and softening to complete breakdown of the polymeric materials. The most common environments that cause degradation of polymers are ultraviolet radiation, industrial chemicals, humidity, ozone and oxygen, microorganisms, and temperature. A combination of two...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006918
EISBN: 978-1-62708-395-9
... weight, crystallinity, degree of cross linking, and backbone molecular structure of the polymer ( Ref 26 – 60 ). Polymers are also prone to time-dependent behavior, and fatigue characterization must incorporate viscoelastic effects; such effects may include sustained loading, sensitivity to peak stress...
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001391
EISBN: 978-1-62708-215-0
... and an epoxy similar to the polymer epoxy gold coating. These results were consistent for the binder in the thick-film ink on resistors from groups 1 and 2. These consistencies indicated that the epoxy contained a polyamide curing agent. This material, if fully cross-linked, would not melt, but would also...
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.9781627083959
EISBN: 978-1-62708-395-9
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006867
EISBN: 978-1-62708-395-9
... solubility parameters exist, the solvent will have no apparent effect. Amorphous polymers absorb chemicals more readily than crystalline polymers, and the rate varies inversely with the degree of crystallinity. Cross-linked polymers will not dissolve but will swell significantly when exposed to chemicals...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003571
EISBN: 978-1-62708-180-1
... applications. The problem encountered with such polymers is their tendency to fail in a catastrophic manner when the glass-transition temperature is reached. Examples of this class of polymer are PMMA, PS, and polycarbonate (PC). Cross-linked polymer PEEK also behaves in a way similar to glassy polymers ( Ref...