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cross-linking polymers

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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
... to fracture at relatively low elongations in tension (2 to 4%). These include PS, PMMA, and rigid (unplasticized) PVC. Crazing is the dominant mechanism of failure in such polymers. Highly cross-linked polymers, such as epoxies and unsaturated polyesters, are also brittle, yet their fracture involves...
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
... 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 having similar solubility-parameter values...
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
... film can easily change if the sliding direction is changed. Reprinted with permission from Ref 4 The quasi-adiabatic interfacial wear involves glassy thermoplastics (not cross linked) and cross-linked polymer systems such as elastomers and thermosets. These polymers show a range of wear...
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
... exposed to heat. Thermosets are densely cross linked and degrade upon heating. Elastomers/rubbers are moderately cross-linked networks, and they deform with application of moderate force. Corrosion of polymers can be classified as disintegration or degradation due to absorption/permeation, oxidation when...
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
.... These consistencies indicated that the epoxy contained a polyamide curing agent. This material, if fully cross-linked, would not melt, but would also exhibit a T g . The metallization interface was analyzed by preparing samples from group 3, the group that exhibited consistent gross delamination. Samples were...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006757
EISBN: 978-1-62708-295-2
...Basic characteristics of engineering polymers Table 1 Basic characteristics of engineering polymers Location (a) Characteristics Examples (b) 1 Flexible and crystallizable chains PEPPPVCPA 2 Cross-linked amorphous networks of flexible chains Phenol-formaldehyde cured...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003522
EISBN: 978-1-62708-180-1
... of which all polymers can be classified, are illustrated in Fig. 23 and described with examples in Table 1 . Thermoplastics should, in theory, have no cross linking, but, in practice, small amounts occur as a result of thermal and oxidative degradation or through the processing of the polymeric material...
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.auto.c0090451
EISBN: 978-1-62708-218-1
... an increase in the viscosity of the dried resin relative to the virgin resin. This increase was suggestive of an increase in molecular weight, possibly through partial cross linking. Testing of the resin samples and the molded parts via GPC produced results that reconciled the discrepancy. The GPC results...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003525
EISBN: 978-1-62708-180-1
... the performance of the molded part. Changes can result in molecular weight decreases through such mechanisms as chain scission, oxidation, and hydrolysis, or as increases through destructive cross linking. Because of this, the characterization of molecular weight is an important aspect of a thorough failure...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006780
EISBN: 978-1-62708-295-2
... the mechanical properties of the component. For amorphous polymers, properties are dependent on chain flexibility and cross linking. Nevertheless, creep damage in polymers is realized through the formation of microscopic cracking and crazing and, potentially on a macroscopic scale, whitening. Surface...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006776
EISBN: 978-1-62708-295-2
... fatigue crack initiation. Source: Ref 12 Fig. 7 Unetched metallographic cross section through gear tooth showing subsurface fatigue crack formed by rolling contact. Original magnification: 132×. Source: Ref 12 Fig. 8 Unetched metallographic cross section through hardened steel...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003539
EISBN: 978-1-62708-180-1
... Fig. 7 Unetched metallographic cross section through gear tooth showing subsurface fatigue crack formed by rolling contact. 132×. Source: Ref 12 Fig. 8 Unetched metallographic cross section through hardened steel roller test specimen with sliding plus rolling contact (sliding to left...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006778
EISBN: 978-1-62708-295-2
.... However, bonding between chains can be covalent (cross linked) or van der Waals. Bonds between atoms can occur in various spatial orientations. The spatial arrangement of atoms can be random (amorphous) or periodic in either two or three directions, resulting in sheet structures (two-dimensional...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003537
EISBN: 978-1-62708-180-1
... not always reveal beach marks and fatigue striations. Macroscale ductile versus brittle fracture: Macroscale ductile fracture is revealed by obvious changes in cross section of the fracture part and/or by shear lips on the fracture surface. Macroscale brittle fractures have fracture surfaces...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006774
EISBN: 978-1-62708-295-2
... polymeric material, carbon atom backbone chains and pendant atoms on the chain are covalently bonded. The individual polymeric chains are then either van der Waals bonded or may be cross linked, that is, covalently bonded. Covalent (and ionic) bonds are typically high-strength bonds, while the van der Waals...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003508
EISBN: 978-1-62708-180-1
... Conchoidal or “rock candy” fracture C 412 (a) Network of cracks over entire cross section Intergranular corrosion Defective Surface D 100: Casting surface irregularities D 110: Fold markings on the skin of the casting D 111 Fold markings over rather large areas...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003543
EISBN: 978-1-62708-180-1
... and ceramic materials are predominantly ionically bonded. Carbon atoms in the backbone of polymer chain are covalently bonded and the pendant side groups are covalently bonded to the backbone. However, bonding between chains may be covalent (“cross linked”) or van der Waals. The bonds between atoms may...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006788
EISBN: 978-1-62708-295-2
... in biologically active soil box experiments under anaerobic conditions Fig. 14 (a) Surface view of interdendritic microbiologically influenced corrosion (MIC) attack at the fusion line of a weld in stainless steel; nondendritic at “A” and dendritic at “D.” (b) Cross section of damage associated with MIC...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003564
EISBN: 978-1-62708-180-1
... nitride balls ( Ref 42 , 43 ). Fig. 3 Loading configuration of five-ball machine Figure 4 shows a cross-sectional view of the test rig. The test unit has a unidirectional thrust bearing configuration, which consists of three balls or rollers equally spaced at 120° by a retainer and loaded...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006789
EISBN: 978-1-62708-295-2
... (cross sections) Optical microscopy Microhardness profiles Advanced techniques Collected wear particles Visual inspection Scanning electron microscopy Transmission electron microscopy (especially on very fine, submicrometer airborne particles) X-ray diffraction Wear Mechanisms...