Morphology, thermal properties and mechanical relaxations of metallocene syndiotactic polypropylenes

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Ester López Moya ◽  
José M. Gómez-Elvira ◽  
Rosario Benavente ◽  
Ernesto Pérez
Keyword(s):  
Thermal Properties ◽  
Temperature Gradient ◽  
Small Proportion ◽  
Molar Mass ◽  
Processing Conditions ◽  
Syndiotactic Polypropylene ◽  
Relative Contribution ◽  
Two Samples ◽  
Concurrent Processes ◽  
Crystallisation Rate

AbstractThe complex polymorphic behaviour of four syndiotactic polypropylene (sPP) samples have been analysed by means of DSC and WAXD techniques. Two samples (sPP1, sPP2) were synthesised via metallocene polymerization by using the ansa-zirconocene Ph2C(Cp)(9-Flu)ZrCl2 as catalyst. Finally, two additional specimens with different molar masses (sPP1-Fr1, sPP1-Fr2) were prepared from the most syndiotactic sPP1 sample by temperature gradient extraction. The WAXD analysis shows that together with the orthorhombic form I, form II can coexist in a variable but small proportion depending on both the chain features and the processing conditions. The relative contribution of the disordered and the ordered types of form I is also dictated by molar mass, configurational microstructure as well as processing conditions. The observed changes in the thermal properties as measured by DSC and in the mechanic-dynamical relaxations of the samples, on slowing the crystallisation rate down, can be rationalised in terms of two concurrent processes, namely the perfection undergone by the crystals and the segregation of the amorphous phase.

scholarly journals Processing of (Co)Poly(2-oxazoline)s by Electrospinning and Extrusion from Melt and the Postprocessing Properties of the (Co)Polymers

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 295 ◽  
Author(s):  
Wojciech Wałach ◽  
Natalia Oleszko-Torbus ◽  
Alicja Utrata-Wesołek ◽  
Marcelina Bochenek ◽  
Ewa Kijeńska-Gawrońska ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Properties ◽  
Molar Mass ◽  
Three Dimensional ◽  
Fused Deposition Modelling ◽  
Processing Conditions ◽  
Structure And Properties ◽  
Scanning Calorimetry ◽  
Gradient Copolymers ◽  
Fused Deposition

Poly(2-oxazoline) (POx) matrices in the form of non-woven fibrous mats and three-dimensional moulds were obtained by electrospinning and fused deposition modelling (FDM), respectively. To obtain these materials, poly(2-isopropyl-2-oxazoline) (PiPrOx) and gradient copolymers of 2-isopropyl- with 2-n-propyl-2-oxazoline (P(iPrOx-nPrOx)), with relatively low molar masses and low dispersity values, were processed. The conditions for the electrospinning of POx were optimised for both water and the organic solvent. Also, the FDM conditions for the fabrication of POx multi-layer moulds of cylindrical or cubical shape were optimised. The properties of the POx after electrospinning and extrusion from melt were determined. The molar mass of all (co)poly(2-oxazoline)s did not change after electrospinning. Also, FDM did not influence the molar masses of the (co)polymers; however, the long processing of the material caused degradation and an increase in molar mass dispersity. The thermal properties changed significantly after processing of POx what was monitored by increase in enthalpy of exo- and endothermic peaks in differential scanning calorimetry (DSC) curve. The influence of the processing conditions on the structure and properties of the final material were evaluated having in a mind their potential application as scaffolds.

Coupling effect of PVDF molar mass and carboxyl content in CNTs on microstructure and thermal properties of CNT/PVDF composites

2018 ◽  
Vol 5 (6) ◽  
pp. 065031
Author(s):  
Run Tian ◽  
Yanxia Zhang ◽  
Zhipeng Li ◽  
Yangyang Huan ◽  
Guangfen Li ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Molar Mass ◽  
Coupling Effect ◽  
Carboxyl Content

The Thermal Properties of Modified Nano-Silica with Diluent/Epoxy Composites

2013 ◽  
Vol 677 ◽  
pp. 49-54 ◽  
Author(s):  
Huey Ling Chang ◽  
Chih Ming Chen
Keyword(s):  
Thermal Properties ◽  
Composite Materials ◽  
Pyrolysis Temperature ◽  
Gravimetric Analysis ◽  
Processing Conditions ◽  
Post Processing ◽  
Nano Silica ◽  
Nano Composite ◽  
Silica Filler ◽  
Negative Effect

In this paper, we present the function of the processing conditions (the amount of filler or diluent in epoxy resin, whether post-curing or not) in thermal properties of the modified silica/epoxy nano-composite materials based on thermal gravimetric analysis (TGA).The results is showed that after post-processing for the nanocomposite materials have a better thermal properties, and adding 3.2wt.% epoxy diluent can be taken a convenience operation, but has a negative effect on thermal properties. Nano-composite materials of diluent 3.2 wt.% plus nano-silica powder 2 wt.% will reach pyrolysis temperature 278.66°C. This reinforcement reaches the highest level observed of the decomposition temperatures of 2wt.% silica filler with no diluent cases nano-composite materials, after post-processing the decomposition temperatures could be enhanced to pyrolysis temperature 308.69 °C.

High-temperature gradient HPLC and LC-NMR for the analysis of complex polyolefins

2008 ◽  
Vol 80 (8) ◽  
pp. 1747-1762 ◽  
Author(s):  
Harald Pasch ◽  
Lars-Christian Heinz ◽  
Tibor Macko ◽  
Wolf Hiller
Keyword(s):  
High Temperature ◽  
Chemical Composition ◽  
Temperature Gradient ◽  
Molar Mass ◽  
Size Exclusion ◽  
Copolymer Composition ◽  
Composition Distribution ◽  
High Temperature Gradient ◽  
Chemical Composition Distribution ◽  
On Line

The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial polymer research. One consequence of the development of new "tailor-made" polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass and chemical composition distribution. The present article briefly reviews different new and relevant techniques for polyolefin analysis. Crystallization analysis fractionation is a powerful new technique for the analysis of short-chain branching in linear low-density polyethylene (LLDPE) and the analysis of polyolefin blends and copolymers regarding chemical composition. For the fast analysis of the chemical composition distribution, a new high-temperature gradient high-performance liquid chromatography (HPLC) system has been developed. The efficiency of this system for the separation of various olefin copolymers is demonstrated. The correlation between molar mass and chemical composition can be accessed by on-line coupling of high-temperature size exclusion chromatography (HT-SEC) and 1H NMR spectroscopy. It is shown that the on-line NMR analysis of chromatographic fractions yields information on microstructure and tacticity in addition to molar mass and copolymer composition.

Temperature Gradient of Concrete Pavement Slab Overlaid with Asphalt Surface Course

2000 ◽  
Vol 1730 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Tatsuo Nishizawa ◽  
Shigeru Shimeno ◽  
Akinori Komatsubara ◽  
Masashi Koyanagawa
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Stress ◽  
Temperature Gradient ◽  
Numerical Simulations ◽  
Structural Design ◽  
Concrete Slab ◽  
Concrete Pavement ◽  
Reduction Effect ◽  
The Relationship

In the structural design of composite pavement with a concrete pavement slab overlaid with an asphalt surface course, it is very important to estimate the temperature gradient in the concrete slab. An asphalt surface course reduces the temperature gradient in an underlaid concrete slab, resulting in the reduction of thermal stress of the concrete slab. This effect was investigated by temperature measurement in model pavements and by thermal conductivity analysis. Thermal properties were estimated by a backanalysis by using measured temperatures over 1 year. From the numerical simulations varying the thickness of asphalt surface and concrete slab, the relationship between the reduction effect and the asphalt thickness was derived as a function of the thickness of asphalt surface course, which can be used in the structural design of the composite pavement.

scholarly journals Metamorphism and thermal properties of fresh snow (study in the Moscow region)

2016 ◽  
Vol 56 (2) ◽  
pp. 199-206 ◽  
Author(s):  
R. A. Chernov
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Temperature Gradient ◽  
Negative Temperature ◽  
Average Temperature ◽  
The North ◽  
Coefficient Of Thermal Conductivity ◽  
European Part Of Russia ◽  
Snow Conditions

As a result of laboratory tests were obtained values of the coefficient thermal conductivity (Keff) of new snow for different types of the solid precipitation: plates, needles, stellars, graupels. Snow samples were collected during a snowfall and placed in the freezer. For all types of sediment thermal conductivity of snow is equal to 0.03–0.04 W/m·°C. Transformation of new snow occurs within 10 days at average temperature −10 °C and the gradient temperature of 50–60 °C/m. Under these conditions, the metamorphism leads to an increase the density of snow, size of grains and rounded snow particles. At the beginning of the experiment, the thermal conductivity of snow is linearly increased in proportion to the density of the snow. However, after 3–5 days Keff stabilized at about 0.08–0.09 W/m·°C, although the density of the snow and size of grains continued to increase. This effect occurs with the appearance of faceted crystals and loosening of snow. In the future, while maintaining a negative temperature coefficient of thermal conductivity remained unchanged. Thus, the temperature gradient metamorphism affect to the thermal conductivity snow, which plays an important role in maintaining the thermal insulation properties of snow cover. The article describes the formula to calculate the thermal conductivity of the snow conditions in the temperature gradient metamorphism. Such conditions are characteristic of the vast expanses of the north and northeast of the European part of Russia. On the basis of long-term observations in Moscow shows the average minimum and maximum values for the density of the snow woods and fields on the basis of which can be calculated for the thermal properties of the snow.

Morphological, mechanical, and thermal properties of PP/SEBS/talc composites

2019 ◽  
pp. 089270571987667 ◽  
Author(s):  
Carlos Ivan Ribeiro de Oliveira ◽  
Marisa Cristina Guimarães Rocha ◽  
Joaquim Teixeira de Assis ◽  
Ana Lúcia Nazareth da Silva
Keyword(s):  
Thermal Properties ◽  
Impact Resistance ◽  
Mechanical And Thermal Properties ◽  
Processing Conditions ◽  
Screw Extruder ◽  
Crystallinity Degree ◽  
Twin Screw ◽  
The Impact ◽  
Scanning Electron ◽  
Nucleating Effect

The aim of this study is to evaluate the effect of some experimental variables such as the content of styrene–ethylene–butylene–styrene (SEBS) and talc, processing conditions and mixing protocol on the properties of polypropylene (PP). To achieve this objective, PP/SEBS blends and PP/SEBS/talc composites were processed in a corotating twin-screw extruder. A masterbatch of PP/talc was prepared before the extrusion of PP/SEBS/talc composites. The morphology of blends and composites was evaluated by scanning electron microscopy, which revealed the dispersion of small rubber droplets in the PP matrix. Moreover, the micrographs also showed that SEBS and talc particles were uniformly dispersed and distributed in the polymer matrix. Results of thermal properties showed that talc had a nucleating effect, which promoted the increase of both PP crystallization temperature and crystallinity degree. The incorporation of talc in PP/SEBS blends led to an expressive increase in the impact resistance by 70% as compared with the reference blend: PP/SEBS 80/20% (w/w). This result reveals that although the PP/SEBS/talc composites showed a separated morphology, the good dispersion and distribution of this mineral filler in the polymers contributed to avoid crack propagation and increase the impact properties. The tensile properties in the elastic region were not significantly affected.

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