Discussion of craze formation and growth in amorphous polymers in terms of the multiplicity of glass transition at low temperatures

Donth, E.; Michler, Goerg H.

doi:10.1007/bf01410431

Cited by 18 publications

(5 citation statements)

References 24 publications

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“…The figures in Table show that the middle part of the main transition can rather be described as a kind of flow similar to small-molecule systems. Assuming formally a viscosity η CF for the “confined flow zone” (CF), , it must be small as compared to the viscosity η 0 of the flow zone beyond the terminal dispersion. Thus η CF is of order G g ‘τ α ≪ η 0 , with τ α the characteristic relaxation time for the α relaxation.…”

Section: Introductionmentioning

confidence: 99%

Fine Structure of the Main Transition in Amorphous Polymers: Entanglement Spacing and Characteristic Length of the Glass Transition. Discussion of Examples

Donth¹,

Beiner²,

Reissig³

et al. 1996

Macromolecules

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117

101

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The main transition of amorphous polymers is analyzed with respect to a fine structure by means of new experimental dynamic shear, dielectric, and heat capacity data for the following polymers: poly(n-alkyl methacrylate)s with alkyl = methyl, ethyl, propyl, butyl, and hexyl, polystyrene, poly(vinyl acetate), a series of weakly vulcanized natural rubbers, a series of butyl rubbers with different carbon black content, polyisobutylene, and bromobutyl rubber. The components of the fine structure are assumed to be a proper glass transition at short times, followed by a confined flow zone, and, at large times, a hindering zone caused by entanglements at large times. Two lengths are assumed to correspond to the first and third components, respectively, the characteristic length to the proper glass transition and the entanglement spacing to the hindering zone. The confined flow will be described by a dispersion law (general scaling) across the main transition. The characteristic length of the glass transition for the poly(n-alkyl methacrylate)sonly of order 1 nm as determined by calorimetryis confirmed by backscaling from the entanglement spacing by means of a Rouse dispersion law for shear. The fate of the Rouse modes below the αβ splitting of the glass transition is discussed for the other amorphous polymers. Finally, a speculative molecular picture of the different modes in the main transition is described. The new element is a low-viscosity longitudinal motion of individual chain parts in the confined flow zone. A simple rheological model for the confined flow is also presented.

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Section: Introductionmentioning

confidence: 99%

Fine Structure of the Main Transition in Amorphous Polymers: Entanglement Spacing and Characteristic Length of the Glass Transition. Discussion of Examples

Donth¹,

Beiner²,

Reissig³

et al. 1996

Macromolecules

Self Cite

117

101

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“…Additionally, the diagonal crack region is also recognized as a plastic deformation region where shear bands formed around the craze zone [ 28 ]. This also demonstrated that the crystalline behavior of PLA/PAni film was approaching to become an amorphous behavior [ 29 ]. As a result, the formation of crazes on the PLA/PAni film also desired to induce a higher biodegradation rate of the PLA/PAni film.…”

Section: Resultsmentioning

confidence: 97%

Crazing Effect on the Bio-Based Conducting Polymer Film

et al. 2021

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The biodegradability problem of polymer waste is one of the fatal pollutFions to the environment. Enzymes play an essential role in increasing the biodegradability of polymers. In a previous study, antistatic polymer film based on poly(lactic acid) (PLA) as a matrix and polyaniline (PAni) as a conductive filler, was prepared. To solve the problem of polymer wastes pollution, a crazing technique was applied to the prepared polymer film (PLA/PAni) to enhance the action of enzymes in the biodegradation of polymer. This research studied the biodegradation test based on crazed and non-crazed PLA/PAni films by enzymes. The presence of crazes in PLA/PAni film was evaluated using an optical microscope and scanning electron microscopy (SEM). The optical microscope displayed the crazed in the lamellae form, while the SEM image revealed microcracks in the fibrils form. Meanwhile, the tensile strength of the crazed PLA/PAni film was recorded as 19.25 MPa, which is almost comparable to the original PLA/PAni film with a tensile strength of 20.02 MPa. However, the Young modulus decreased progressively from 1113 MPa for PLA/PAni to 651 MPa for crazed PLA/PAni film, while the tensile strain increased 150% after crazing. The significant decrement in the Young modulus and increment in the tensile strain was due to the craze propagation. The entanglement was reduced and the chain mobility along the polymer chain increased, thus leading to lower resistance to deformation of the polymer chain and becoming more flexible. The presence of crazes in PLA/PAni film showed a substantial change in weight loss with increasing the time of degradation. The weight loss of crazed PLA/PAni film increased to 42%, higher than that of non-crazed PLA/PAni film with only 31%. The nucleation of crazes increases the fragmentation and depolymerization of PLA/PAni film that induced microbial attack and led to higher weight loss. In conclusion, the presence of crazes in PLA/PAni film significantly improved enzymes’ action, speeding up the polymer film’s biodegradability.

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“…Here, the modulus of the glassy SAN matrix decreases to the level of the rubber. Under the action of a tensile stress this situation can be considered similar to the glass transition range of matrix material, discussed in detail in [14,15]. Whereas the smaller (harder) rubber particles show a modulus similar to the matrix modulus (moduli ratio G S R /G M % 1) the bigger (weaker) rubber particles are somewhat weaker than the matrix (moduli ratio G R b / G M`1 ).…”

Section: Toughness Of Abs With Polybutadiene Rubber Particlesmentioning

confidence: 83%

“…Local stress concentration at voided particles acts as an effect of local decrease of glass transition temperature. Such a stressinduced reduction of T g was used to understand craze formation in amorphous polymers first in [21] and later on in [14,15]. This idea has also been transformed to semicrystalline polymers in [22].…”

Section: Low-temperature Toughness Of Particle-modi®ed Ppmentioning

confidence: 99%

Microstructural construction of polymers with improved mechanical properties

Michler

1998

Polym. Adv. Technol.

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Mechanical properties of materials are based on structure or morphology and on the micromechanical processes of deformation and fracture, i.e. on the “micromechanics”. Developments mainly in electron microscopy and scanning force microscopy opened up a wide range of experiments previously impossible, including the in situ study of micromechanical processes. Direct microscopic techniques on the basis of scanning, transmission, and high‐voltage electron microscopy are used to study micromechanical properties of different polymer blends of amorphous and semicrystalline polymers. Of particular interest are polymer blends with improved toughness. Blends with styrene–acrylonitrile as matrix polymer and different types of modifier particles, with their diameters ranging between about 100 nm and 1 μm, have been investigated. Examples of blends with a semicrystalline matrix are polypropylene (PP) blends with different amounts of various rubber and modifier particles. New micromechanical mechanisms have been found, which can change the toughness of some acrylonitrile–butadiene–styrene grades or improve low‐temperature toughness of PP. The examples show that detailed knowledge of the morphology and micromechanical mechanisms helps to define criteria of improved properties. This “microstructural” analysis and construction of polymeric systems provides a new basis of polymer modification. © 1998 John Wiley & Sons, Ltd.

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Discussion of craze formation and growth in amorphous polymers in terms of the multiplicity of glass transition at low temperatures

Cited by 18 publications

References 24 publications

Fine Structure of the Main Transition in Amorphous Polymers: Entanglement Spacing and Characteristic Length of the Glass Transition. Discussion of Examples

Fine Structure of the Main Transition in Amorphous Polymers: Entanglement Spacing and Characteristic Length of the Glass Transition. Discussion of Examples

Crazing Effect on the Bio-Based Conducting Polymer Film

Microstructural construction of polymers with improved mechanical properties

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