Dynamic mechanical analysis and its relationship to impact transitions

Woo, Lecon; Westphal, Stanley P.; Ling, Michael T.K.

doi:10.1002/pen.760340507

Cited by 40 publications

(15 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently there has been a revival of the interest in homogeneous copolymers because of catalytic developments in this field. In particular by metallocene catalysis [18][19][20][21][22][23] in combination with specific polymerization processes a new class of homogeneous copolymers are currently being developed with properties different from those of the existing heterogeneous copolymers.…”

Section: --4466/96/$ 5 O0 9 1996 Akaddmiai Kiadd Budapest John mentioning

confidence: 99%

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

View full text Add to dashboard Cite

Ethylene-propylene (EP) and ethylene-octene (EO) copolymers polymerized with the aid of homogeneous vanadium and metallocene catalysts were compared by DSC and time-resolved simultaneous SAXS-WAXS-DSC at scanning rates of 10 and 20~ rain -1 using synchrotron radiation. An EP eopolymer with a density of 896 kg m -3 (about 89 mol% ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [wC(7)] calculated from these reflections using the two-phase model was in good agreement with we(T) calculated from Cp measurements using DSC. The Cp measurements also enabled calculation of the baseline Cp and the excess Cp. The SAXS measurements revealed a strong change in the long period in cooling and in heating. The SAXS invariant as a function of temperature showed a maximum in both cooling and heating, which could be explained from the opposing influences of the crystallinity and the electron density difference between the two phases. Two EO eopolymers with densities of about 871 kg m -3 (about 87 mol% ethylene) no longer showed any clear WAXS reflections, although DSC and SAXS measurements showed that these eopolymers did crystallize. The similarity between the results led to the conclusion that the copolymers, though based on different catalyst systems -vanadium and metallocene -did not have strongly different sets of propagation probabilities of chain growth during polymerization. On the basis of a Monte Carlo simulation model of crystallization and morphology, based on detailed knowledge of the mierochain structure, the difference between WAXS on the one hand and DSC and SAXS on the other could be explained as being due to loosely packed cryz,tallized ethylene sequences in clusters. These do cause the density and the electron density of the cluster to increase (which is measurable by SAXS) and the enthalpy to decrease (which is measurable by DSC) but the clusters are too small and/or too imperfect to give constructive interference in the case of WAXS. Of an EP copolymer with an even lower ethylene content (about 69 mol%), the crystallization and melting processes could still be readily measured by DSC and SAXS, which proves that these techniques are eminently suitable for investigating the crystallization and melting behaviour of the copolymers studied.

show abstract

Section: --4466/96/$ 5 O0 9 1996 Akaddmiai Kiadd Budapest John mentioning

confidence: 99%

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

View full text Add to dashboard Cite

show abstract

“…More specifically, it was suggested that polymers possessing low temperature secondary transitions, especially those related to main‐chain motions, would display good impact toughness at room temperature. The proposed connection was based on the similarity in the position and activation enthalpy of fracture mode transitions and secondary loss transitions 12–18. There are, however, also numerous exceptions to the rule 11, 19…”

Section: Introductionmentioning

confidence: 99%

Rate‐ and temperature‐dependent strain softening in solid polymers

Breemen

Engels

Klompen

et al. 2012

J Polym Sci B Polym Phys

114

View full text Add to dashboard Cite

It is demonstrated that a large number of solid polymers (PMMA, PLLA, iPP, PS) display a pronounced change in kinetics (strain-rate and temperature dependence) after yield. The phenomenon finds its origin in the fact that, in specific ranges of temperature and strain rate, two different molecular processes may contribute to the yield stress. Because of strain softening, the post-yield response is only controlled by one of the two, resulting in a strain-rate dependence of the yield drop. The universality of the phenomenon is discussed in connection to the alleged influence of secondary transitions on the impact response of polymer glasses. A modification of the finite-strain elasto-viscoplastic EGP-model is proposed to enable an accurate description of the mechanical response of solid polymers in the transition range. The versatility of the model is demonstrated on the temperature and strain-rate dependence of the intrinsic mechanical behavior of PMMA, iPP, PS, and PLLA.

show abstract

“…The relevant relaxation processes are the first secondary relaxation below T g . Hartmann and Lee [17] and Woo et al [18] had reported a method that by doing a Fourier analysis to obtain the complete frequency spectrum of the impact pulse and comparing this spectrum with the room-temperature frequency spectrum of the loss factor of the secondary transition, the impact resistance was correlated with the secondary transition. They also obtained good agreement between the calculated value and the measured value.…”

Section: Introductionmentioning

confidence: 99%

Interfacial toughening and consequent improvement in fracture toughness of carbon fiber reinforced epoxy resin composites: induced by diblock copolymers

Deng¹,

Zhou²,

Zhu³

et al. 2013

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. Carbon fibers chemically grafted with hydroxyl-terminated diblock copolymer poly (n-butylacrylate)-b-poly (glycidyl methacrylate) (OH-PnBA-b-PGMA), were used as the reinforcement for epoxy composites. The multi-filament composite specimens were prepared and measured by dynamic mechanical analysis (DMA), to study the interfacial toughness of carbon fiber reinforced epoxy composites with the diblock copolymers. The loss modulus and loss factor peaks of !-relaxation indicated that composites with diblock copolymers could dissipate more energy at small strain and possess better interfacial toughness, whereas composites without the ductile block PnBA having the worse interfacial toughness. The glass transition temperature and the apparent activation energy calculated from the glass transition showed that the strong interfacial adhesion existed in the composites with diblock copolymers, corresponding with the value of interfacial shear strength. Therefore, a strengthening and toughening interfacial structure in carbon fiber/epoxy composites was achieved by introducing the diblock copolymer OH-PnBA-b-PGMA. The resulting impact toughness, characterized with an Izod impact tester, was better than that of composite without the ductile block PnBA.

show abstract

Dynamic mechanical analysis and its relationship to impact transitions

Cited by 40 publications

References 6 publications

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Rate‐ and temperature‐dependent strain softening in solid polymers

Interfacial toughening and consequent improvement in fracture toughness of carbon fiber reinforced epoxy resin composites: induced by diblock copolymers

Contact Info

Product

Resources

About