Changes of mechanical properties in cold-crystallized syndiotactic polypropylene during aging

Schwarz, Ingmar; Stranz, Michael; Bonnet, Martin; Petermann, J.

doi:10.1007/s003960100488

Cited by 27 publications

(21 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…38 If one makes the reasonable assumption that elongation (i.e., strain) at break behaves similarly to strain at yield, then we see from their work that both EЈ and ⑀ b for PP decrease with aging. Thus, two reports from the literature indicate that our definition of brittleness can be used even to explain the brittleness that occurs with aging.…”

Section: Discussionmentioning

confidence: 82%

Sliding wear, viscoelasticity, and brittleness of polymers

2006

View full text Add to dashboard Cite

We have connected viscoelastic recovery (healing) in sliding wear to free volume in polymers by using pressure-volume-temperature (P-V-T) results and the Hartmann equation of state. A linear relationship was found for all polymers studied with a wide variety of chemical structures, except for polystyrene (PS). Examination of the effect of the indenter force level applied in sliding wear on the healing shows that recovery is practically independent of that level. Strain hardening in sliding wear was observed for all materials except PS, the exception attributed to brittleness. Therefore, we have formulated a quantitative definition of brittleness in terms of elongation at break and storage modulus. Further, we provide a formula relating the brittleness to sliding wear recovery; the formula is obeyed with high accuracy by all materials including PS. High recovery values correspond to low brittleness, and vice versa. Our definition of brittleness can be used as a design criterion for choosing polymers for specific applications.

show abstract

Section: Discussionmentioning

confidence: 82%

Sliding wear, viscoelasticity, and brittleness of polymers

2006

View full text Add to dashboard Cite

show abstract

“…a decrease in the yield stress of 5 and 10 MPa and a decrease in the time‐to‐failure of one and two orders of magnitude for the 4.5 and 9% impact modified material, respectively. The yield stress of all polymers, including PC, can be significantly increased by annealing,35–39, 57–59 and indeed the same increase can be realized for impact modified PC. This is demonstrated in Figure 5, where the yield stress is plotted as a function of annealing time for different annealing temperatures and increases linearly with the logarithm of the annealing time.…”

Section: Resultsmentioning

confidence: 61%

Improvement of the Long‐Term Performance of Impact‐Modified Polycarbonate by Selected Heat Treatments

Engels

Schrauwen

Govaert

et al. 2009

Macro Materials & Eng

View full text Add to dashboard Cite

Next to the intended increase of the impact toughness, impact modification of polycarbonate generally results in an unwanted decrease in yield stress and time‐to‐failure under constant stress. It is demonstrated that this loss in strength can be fully compensated for by an annealing treatment, or by increasing the mold temperature. The influence of impact modification on the short‐ and long‐term strengths of glassy polymers is predicted by the extension of existing models with a scaling rule based on the filler volume percentage. Introduction of this scaling rule in the evolution of yield stress during physical aging even allows for the direct prediction of yield stress on the basis of processing conditions.magnified image

show abstract

“…However, as it was also reported for sPP copolymers, [47] it is impossible to assure the non-coexistence of this polymorph with a certain small amount of disordered modification of Form II containing kink-bands, [9,48] appearing this latest contribution at 2y around 17-188. All of these changes within the crystalline regions significantly affect some other parameters such as density, [49] physical properties, [50] and mechanical behavior, as will be discussed below.…”

Section: Resultsmentioning

confidence: 99%

“…There are many opinions which support the absence [50,53] of any relaxation above the b process for sPP. However, its presence has been recognized by some authors, [54,55] though its origin is not clear.…”

Section: Resultsmentioning

confidence: 99%

Evolution of a Metallocenic sPP with Time: Changes in Crystalline Content and Enthalpic Relaxation

Arranz-Andrés

Benavente

Ribeiro³

et al. 2006

Macro Chemistry & Physics

View full text Add to dashboard Cite

Summary: The structural evolution of a metallocenic syndiotactic poly(propylene), sPP, with time has been studied. Due to the low syndiotactic content, the analyzed sPP sample can be easily quenched to a completely amorphous state. This amorphous sample, when left at room temperature is able to crystallize at relatively long times. The degree of crystallinity, as a function of time, has been analyzed by X‐ray diffraction and DSC. The DSC melting curves show the presence of a very important low‐temperature endotherm, besides the main melting peak. Real‐time variable–temperature synchrotron experiments have been performed in order to analyze the origin of the two melting peaks. They seem to arise from the melting of two populations of sPP crystals with different size and/or perfection, rather than from the melting of different polymorphs. The changes in the crystalline regions are accompanied by important variations in the mechanical behavior, as revealed by DMTA and microhardness (MH) measurements. In addition, the sPP crystallization has been analyzed by MH measurements, showing the importance that a relative low crystallinity has on the stiffness of a polymeric material at temperatures above Tg. On the other hand, the kinetics of the enthalpic recovery of quenched amorphous sPP specimens has been analyzed by DSC with temperature modulation. It was found that this enthalpic relaxation can be described by the KWW model, and the relaxation times and shape parameters at three different aging temperatures have been determined, with the corresponding apparent activation energy of this process.Variation with temperature of the most probable long spacing of sPP.imageVariation with temperature of the most probable long spacing of sPP.

show abstract

Changes of mechanical properties in cold-crystallized syndiotactic polypropylene during aging

Cited by 27 publications

References 0 publications

Sliding wear, viscoelasticity, and brittleness of polymers

Sliding wear, viscoelasticity, and brittleness of polymers

Improvement of the Long‐Term Performance of Impact‐Modified Polycarbonate by Selected Heat Treatments

Evolution of a Metallocenic sPP with Time: Changes in Crystalline Content and Enthalpic Relaxation

Contact Info

Product

Resources

About