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Molecular degradation

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Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780359
EISBN: 978-1-62708-281-5
... modulus, tan delta Temperature-dependent behavior, aging/degradation, solid-liquid interactions Gel permeation chromatography (GPC) Weight-average molecular weight, molecular weight distribution Degradation, suitability of material for use Melt flow rate (MFR) Melt viscosity Degradation...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 August 2013
DOI: 10.31399/asm.tb.ems.t53730099
EISBN: 978-1-62708-283-9
...Abstract Abstract This chapter discusses the structural classifications, molecular configuration, degradation, properties, and uses of polymers. It describes thermoplastic and thermosetting polymers, degree of polymerization, branching, cross-linking, and copolymers. It also discusses glass...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780146
EISBN: 978-1-62708-281-5
... reagent by the polymer. Environmental conditions can promote brittle fracture in normally ductile plastics at levels of stress or strain well below those that would usually cause failure at all. Actual degradation of a polymer, which reduces molecular weight and therefore mechanical properties, does...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780336
EISBN: 978-1-62708-281-5
... of the biodegradability of plastics or lack thereof has been conducted ( Ref 1 ). Many plastics, such as polyethylene (PE), polypropylene (PP), and polystyrene (PS), do not support microbial growth. Low-molecular-weight hydrocarbons, however, can be degraded by microbes. They are taken up by microbial cells, activated...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2012
DOI: 10.31399/asm.tb.ffub.t53610327
EISBN: 978-1-62708-303-4
... to hydrolytic degradation that a reduced polymer molecular weight is found during failure analysis. The challenge for the analyst then becomes deciding whether the degradation occurred during fabrication of the part or on exposure to an aqueous service environment. High-molecular-weight polymers will also...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2010
DOI: 10.31399/asm.tb.scm.t52870063
EISBN: 978-1-62708-314-0
.... Polymeric matrices for advanced composites are classified as either thermosets or thermoplastics. Thermosets are low molecular weight, low viscosity monomers (≈2000 centipoise) that are converted during curing into three-dimensional crosslinked structures that are infusible and insoluble. Crosslinking ( Fig...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780343
EISBN: 978-1-62708-281-5
... approach pertinent to structure analysis. This is followed by a review of the characterization of plastics by infrared and nuclear magnetic resonance spectroscopy. The article then provides information on the distribution of molecular weight of an engineering plastic. It further discusses the methods used...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780329
EISBN: 978-1-62708-281-5
..., and physical stresses all combine to produce changes in the chemical composition of the material. These changes may take the form of polymer molecular weight reduction due to main-chain cleavage, the formation of cross links, or the formation of oxidized and other functional groups. As the chemical composition...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2010
DOI: 10.31399/asm.tb.scm.t52870401
EISBN: 978-1-62708-314-0
... absorption. However, paint systems are useful in protecting composite structures from ultraviolet (UV) radiation. Ultraviolet radiation is the band of light from 300 to about 4000 Å. It can cause degradation through molecular weight change and crosslinking in the resin system. However, this damage...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780028
EISBN: 978-1-62708-281-5
...Abstract Abstract This article describes in more detail the fundamental building-block level, atomic, then expands to a discussion of molecular considerations, intermolecular structures, and finally supermolecular issues. An explanation of important thermal, mechanical, and physical properties...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780314
EISBN: 978-1-62708-281-5
..., the degradation rate over most of the temperature range is approximately halved when the relative humidity is reduced from 100 to 75%. As indicated in the discussion on thermoplastic polyesters, the hydrolytic degradation leads to a progressive reduction in molecular weight and eventually to a loss...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 October 2012
DOI: 10.31399/asm.tb.lmub.t53550325
EISBN: 978-1-62708-307-2
...Abstract Abstract This chapter describes the molecular structures and chemical reactions associated with the production of thermoset and thermoplastic components. It compares and contrasts the mechanical properties of engineering plastics with those of metals, and explains how fillers...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780267
EISBN: 978-1-62708-281-5
.... and Feast J. , Ed., John Wiley & Sons , 1978 3. Pooley C.M. and Tabor D. , Friction and Molecular Structure: The Behaviour of Some Thermoplastics , Proc. R. Soc. (London) A , Vol 329 , 1972 , p 251 – 274 10.1098/rspa.1972.0112 4. Steijn R.P. , The Sliding...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780404
EISBN: 978-1-62708-281-5
... if the polymers employed are not properly stabilized. Mechanical stress is known to enhance degradative effects. Degradation usually involves molecular-weight reduction by one of several mechanisms ( Ref 9 ). Surface embrittlement and consequent microcracking occur. This promotes crack initiation and possibly...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780089
EISBN: 978-1-62708-281-5
... Using NMR and GPC Techniques , J. Appl. Polym. Sci. , Vol 16 , 1972 , p 1953 – 1958 10.1002/app.1972.070160809 23. Batzer H. , and Zahir S.A. , Studies in the Molecular Weight Distribution of Epoxide Resins. II . Chain Branching in Epoxide Resins, J. Appl. Polym. Sci. , Vol 19...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780115
EISBN: 978-1-62708-281-5
... becomes rubbery. The T g is also a measure of the onset of long-range molecular movement in the plastic. Because the transition from glass to rubber is not a thermodynamic transition, but rather a manifestation of viscoelasticity, the exact value of the T g depends on the method used to measure...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2003
DOI: 10.31399/asm.tb.cfap.t69780003
EISBN: 978-1-62708-281-5
... to form a polymer. These variations in structure within the molecule may involve stereoisomerism, branching, molecular weight and distribution, end groups and impurities, and copolymerization. Polymer size is quantified primarily by molecular weight (MW), molecular-weight distribution (MWD), and branching...
Series: ASM Technical Books
Publisher: ASM International
Published: 30 April 2021
DOI: 10.31399/asm.tb.tpsfwea.t59300391
EISBN: 978-1-62708-323-2
... Water content Mostly in used oil Corrosivity Ability of an oil to attack solids Molecular weight Size of molecules in predominating oil Viscosity index (VI) Temperature dependence of the viscosity of an oil (high VI means less change) Fig. 14.11 Schematic of an air bearing...
Series: ASM Technical Books
Publisher: ASM International
Published: 30 April 2021
DOI: 10.31399/asm.tb.tpsfwea.t59300301
EISBN: 978-1-62708-323-2
...-molecular-weight polyethylene; PTFE, polytetrafluoroethylene; PEEK, polyetheretherketone; ABS, acrylonitrile butadiene styrene; PPS, polyphenylene sulfide Fig. 11.7 Two-body abrasion test results of selected plastics. UHMWPE, ultrahigh-molecular-weight polyethylene; PTFE, polytetrafluoroethylene...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2010
DOI: 10.31399/asm.tb.omfrc.t53030237
EISBN: 978-1-62708-349-2
.... The change in the molecular composition may extend only a few nanometers on the surface but can continue to progress into the bulk of the composite matrix. Composite materials having polymeric matrices are susceptible to degradation from heat, sunlight, ozone, atomic oxygen (in space), moisture, solvents...