Inferring meaningful relaxation spectra from experimental data

Bio-based poly(L-lactide)/poly(amide-11) blends (PLA/PA11, 80/20 w/w) and poly(L-lactide)/poly(amide-6) blends (PLA/PA6, 80/20 w/w) are processed by twin-screw extrusion followed by injection-moulding and key rheological parameters controlling their morphologie are investigated. The same work is done using the same PLA modified by a multi-step reactive extrusion route with an epoxy-based chain extender to obtain modified poly(lactide)/poly(amide-11) (PLA-j/PA11 80/20 w/w) blends. The morphologies of the extruded materials and of the injection moulded parts are characterized by SEM and their formation is deeply discussed via rheological investigation to highlight the contribution of viscosity, elasticity and interfacial tension. The existence of a critical shear rate related to the transition from nodular to fibrillar morphology is highlighted and the results are in good agreement with the condition of fibrillation Ca/Ca (crit) $ 4. Interestingly, with the exception of PLA/PA6 specimens, all blends obviously display uniform thin-thread fibrillar morphologies after injection-moulding. Compared with pure PLA, a drastic increase of the ductility was observed in the blends exhibiting a fiberlike structure without meanwhile sacrificing the stiffness. This study confirms that, through the appropriate choice of blend components (viscosity and elasticity ratio, flow conditions, interfacial tensions) the in situ fibrillation concept provides access, at a reasonable cost, to new materials with improved thermomechanical performances, without sacrificing weight and ability to be recycled.

show abstract

“…Germany) 60 which is a numerical procedures based on the regularization method proposed by Honerkamp and Weese, 61 following the eqn (13):…”

Section: View Article Onlinementioning

confidence: 99%

Development of nanofibrillar morphologies in poly(l-lactide)/poly(amide) blends: role of the matrix elasticity and identification of the critical shear rate for the nodular/fibrillar transition

et al. 2018

View full text Add to dashboard Cite

show abstract

“…In addition the dynamical-mechanical data were used to determine tentative relaxation spectra according to the method of Stadler and Bailly, 24 which was found to provide the most accurate spectra among several methods tested. 25 This method does not calculate the spectrum itself by determining different modes individually but describes the spectrum with a spline whose knots (as spectrum descriptors) are adjusted in logarithmized relaxation strength logH-position and logarithmized relaxation time log to set up a continuous spectrum, discretized at 10 modes per decade. This is sufficient to describe all except for the most sharp spectra for which a higher mode density is necessary to obtain an accurate spectrum.…”

mentioning

confidence: 99%

Hydrogen Bonding in a Reversible Comb Polymer Architecture: A Microscopic and Macroscopic Investigation

et al. 2016

View full text Add to dashboard Cite

Abstract:In this work an investigation of the hydrogen bonding mechanism in a transiently branched comb-like polymer system in the melt is reported. The system under investigation consists of a polybutylene oxide (PBO)-based backbone, randomly functionalized with thymine (thy) groups, in combination with shorter PBO graft chains, end-functionalized with diaminotriazine (DAT) groups. The functional groups are able to associate through hydrogen bonding. The hetero-complementary association of these groups leads to the formation of a transiently branched comb-like polymer system. Since recently virtually exclusive heterocomplementary association could be observed in the supramolecular association of telechelically-modified oligomeric PEG chains, here we aim to extend the supramolecular assembly mechanism towards branched structures. The present work combines Small Angle Neutron Scattering (SANS) experiments on a selectively labeled system with macroscopic dynamics measured in linear rheology response. The association of thy-and DAT-modified components was studied as a function of temperature and composition. The scattering function reveals the formation of a block copolymer and can be exclusively attributed to heterocomplementary association of the hydrogen bonding groups. Scattering functions of nonfunctionalized blends are also reported as references and evidence the change in the microstructure induced by the hetero-complementary association. All scattering profiles were described by means of the Random Phase Approximation (RPA) formalism from which the average aggregation number i.e. comb arm functionality and the equilibrium association constant could be determined directly in the melt state as a function of temperature. On the other hand, rheological measurements were performed in the melt state to study the influence of the reversible bonds on the macroscopic dynamics of the polymer system. The rheology data are in good agreement with the SANS results and confirm the transient comb-like branched architecture. The supramolecular association exhibits characteristic bonding times of the groups in the order of 1 s at -25 °C and therefore makes the thy-DAT pair an ideal candidate for the development of responsive materials that combine permanent and transient linkages for novel applications and self-healing properties.

show abstract

“…From this viewpoint, the work of Dealy and coworkers is valuable (McDougall et al 2014). They compared three algorithms of continuous spectrum (FPI, NLREG, and CHS) and an algorithm of discrete spectrum [IRIS (Baumgärtel and Winter 1989)].…”

Section: Comparison With Simulated Datamentioning

confidence: 99%

“…This is Fig. 6 of McDougall et al (2014). It must be noted that the modulus data for this calculation were generated with 4 % random error [see Fig.…”

Section: Comparison With Simulated Datamentioning

confidence: 99%

“…It must be noted that the modulus data for this calculation were generated with 4 % random error [see Fig. 2 of McDougall et al (2014)] Although all algorithms give almost same spectra within the Davies-Anderssen limit, both spectra from PSA and BLM are wavier than others in long time regime. [2] For m Â n matrix K, the theorem of singular value decomposition reads…”

Section: Comparison With Simulated Datamentioning

confidence: 99%

See 1 more Smart Citation

Viscoelastic Spectrum

Cho¹

2016

Viscoelasticity of Polymers

View full text Add to dashboard Cite

This chapter deals with the mathematical fundamentals and numerical algorithms of relaxation and retardation spectra. The first section consists of the importance of spectrum, the Fuoss-Kirkwood relations, the ill-posedness in inferring viscoelastic spectra and some mathematical formulas related with the spectra. The second and third sections are the introduction to the algorithms of continuous and discrete spectra, respectively.

show abstract

Inferring meaningful relaxation spectra from experimental data

Cited by 38 publications

References 20 publications

Development of nanofibrillar morphologies in poly(l-lactide)/poly(amide) blends: role of the matrix elasticity and identification of the critical shear rate for the nodular/fibrillar transition

Development of nanofibrillar morphologies in poly(l-lactide)/poly(amide) blends: role of the matrix elasticity and identification of the critical shear rate for the nodular/fibrillar transition

Hydrogen Bonding in a Reversible Comb Polymer Architecture: A Microscopic and Macroscopic Investigation

Viscoelastic Spectrum

Contact Info

Product

Resources

About