Memory effect of the molecular topology of lamellar polyethylene on the strain-induced fibrillar structure

Humbert, Séverine; Lame, Olivier; Chenal, Jean-Marc; Séguéla, Roland; Vigier, G.

doi:10.1016/j.eurpolymj.2012.03.010

Cited by 21 publications

(25 citation statements)

References 57 publications

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“…However increasing the draw temperature reduces the propensity for cavitation or interfibrillar density fluctuations [48] so that more samples can be investigated during drawing at elevated temperature than in the case of the drawing at RT. This is one of the major benefits from the present study compared to our previous one [37]. Figure 2 shows the evolution of the meridian intensity profile of quenched PE-A as a function of strain at two different T d .…”

Section: Resultsmentioning

confidence: 72%

“…This is in agreement with our previous findings at RT. Finally a correlation was attempted with the interfacial layer thickness which worked fairly well at RT [37]. Figure 6 shows the D f versus X i plots at various T d .…”

Section: Resultsmentioning

confidence: 95%

“…In the case of scattering cylinders, the relevant Guinier's approximation function is given by Equation (4) [43]: (4) where D f is the cylinder diameter with D f = 2R f where R f is the radius of gyration. Fitting the experimental intensity data with Equation (4) enabled computing only one diameter value for each sample as demonstrated in the previous study [37]. The standard deviation of the D f data was about 1.0 nm or less.…”

Section: Saxs Measurementsmentioning

confidence: 96%

“…The samples called 'isotherm' were melted at 170°C and then cooled in a thermostatic oil bath at the temperature T c and held at this temperature for 15 hours. More details on the sample preparation are given elsewhere [37,40].…”

Section: Experiments 21 Materials and Sample Preparationmentioning

confidence: 99%

“…So that one may foresee some consequences on the microfibril morphology in spite of the meltingrecrystallization process. In a previous paper [37] we reported an in situ SAXS study of the fibrillar transformation at room temperature of a series of polyethylene materials covering a wide range of crystallinity 0.48 < X c < 0.80 and long period 17 nm < L p < 37 nm. It was shown that though the fibrillar long period did not depend on the initial morphology, the width of the microfibrils displayed a correlation with the initial semi-crystalline morphology.…”

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confidence: 99%

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On the strain-induced fibrillar microstructure of polyethylene: Influence of chemical structure, initial morphology and draw temperature

Xiong¹,

Lame²,

Chenal³

et al. 2016

Express Polym. Lett.

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A general feature of the morphogenesis of semicrystalline polymers is the regular stacking of chainfolded lamellar crystals alternating with amorphous layers. This stacking s characterized by an intercrystalline long period L p including the crystalline lamella and amorphous layer thicknesses. The stacking long period is in the range of a few nanometers to a few tens. When crystallization is performed from a quiescent melt, the resulting microstructure is isotropic with a spherulitic arrangement of the lamella stacks as a result of the radial growth of the crystals from a common multiple nucleus often designated as axialite [1]. The size scale of spherulites ranges from a few to several hundred microns. Upon plastic deformation at large strains, isotropic semicrystalline polymers transform into fibrillar materials that aroused a great interest from both academic and industrial standpoints owing to their remarkable mechanical performances [2-6] to be used as ropes, textile fibers for high performance tissues and fabrics, reinforcing fibers for polymer-based composites, etc. Abstract. The influence of crystalline microstructure and molecular topology on the strain-induced fibrillar transformation of semi-crystalline polyethylenes having various chemical structures including co-unit content and molecular weight and crystallized under various thermal treatments was studied by in situ SAXS at different draw temperatures. The long period of the nascent microfibrils, L pf , proved to be strongly dependent on the draw temperature but non-sensitive to the initial crystallization conditions. L pf was smaller than the initial long period. Both findings have been ascribed to the straininduced melting-recrystallization process as generally claimed in the literature. The microfibrils diameter, D f , was shown to depend on the draw temperature and initial microstructure in a different way as L pf . The evolution of D f was shown to correlate with the interfacial layer thickness that mainly depends on the chemical structure of the chains. It was concluded that, in contrast to L pf , the microfibril diameter should not be directly sensitive to the strain-induced melting-recrystallization. The proposed scenario is that after the generation of the protofibrils by fragmentation of the crystalline lamellae at yielding, the diameter of the microfibril during the course of their stabilization should be governed by the chain-unfolding and subsequent aggregation of the unfolded chains onto the lateral surface of the microfibrils. The morphogenesis of the microfibrils should therefore essentially depend on the chemical structure of the polymer that governs its crystallization ability, its chain topology and subsequently its fragmentation process at yielding. This scenario is summed up in a sketch.

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Section: Resultsmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 95%

Section: Saxs Measurementsmentioning

confidence: 96%

Section: Experiments 21 Materials and Sample Preparationmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

On the strain-induced fibrillar microstructure of polyethylene: Influence of chemical structure, initial morphology and draw temperature

Xiong¹,

Lame²,

Chenal³

et al. 2016

Express Polym. Lett.

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Influence of temperature on the microstructure and mechanical properties of stretched polypropylene

Xiong

Cao

2015

J of Applied Polymer Sci

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Microstructure and mechanical properties of isotactic polypropylene (iPP) stretched at different temperatures were studied. Strain‐induced fibrils were observed after stretching. Crystallinity (Xc), crystallite thickness (Lc), long period (Lpf), and diameter (Df) of fibrils were characterized by Differential Scanning Calorimetry and Small angle X‐ray scattering. Lpf of stretched iPP below 60°C was found to be lower than undrawn iPP. Xc, Lc, and Df increased with increasing draw temperature. Tensile test showed that Young's moduli of stretched iPPs were negatively dependent on Xc and Lc. The fraction of taut tie molecules was estimated from the mechanical model. Results showed that more tie molecules were formed in the samples stretched at lower temperatures. Dynamical mechanical analysis showed that glass transition temperature was strongly dependent on the draw temperature. The glass transition peak disappeared in stretched iPPs obtained below 80°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42622.

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Analysis of the influence of the injection molding process on the crystallization kinetics of a HDPE

Giboz

Copponnex

Mélé

2016

J of Applied Polymer Sci

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Thermal analyses of microparts in high density polyethylene (HDPE) have shown that the specific processing conditions used in microinjection molding have irreversible consequences on the polymer morphology. This result has been demonstrated with the analysis of the non-isothermal crystallization behavior of a HDPE with different thermal histories. The evolution of the absolute crystallinity has been analyzed with a relevant model able to separate the primary and secondary mechanisms all over the crystallization duration. This model has emphasized that the evolution of the primary crystallinity with time is different for the microparts compared to the conventional objects. These differences were attributed to variations of the crystallization mechanisms, especially within the nucleation phase, where a persistent melt memory effect of the former chains orientation/extension was assumed.

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Memory effect of the molecular topology of lamellar polyethylene on the strain-induced fibrillar structure

Cited by 21 publications

References 57 publications

On the strain-induced fibrillar microstructure of polyethylene: Influence of chemical structure, initial morphology and draw temperature

On the strain-induced fibrillar microstructure of polyethylene: Influence of chemical structure, initial morphology and draw temperature

Influence of temperature on the microstructure and mechanical properties of stretched polypropylene

Analysis of the influence of the injection molding process on the crystallization kinetics of a HDPE

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