scholarly journals Dependence of Crystallization Behavior of Interacting Telechelic Poly(butylene succinate) Oligomer on Molecular Weight

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1530
Author(s):  
Cong Chen ◽  
Xue-Wen Zhang ◽  
Hai-Mu Ye
Keyword(s):  
Growth Rate ◽  
Crystallization Rate ◽  
Crystal Nucleation ◽  
Nucleation Density ◽  
Butylene Succinate ◽  
Nucleation Behavior ◽  
Crystalline Polymers ◽  
Molecular Weights ◽  
Primary Nucleation ◽  
The Impact

A large spherulite structure deteriorates the mechanical properties of crystalline polymers, and therefore various methods have been explored to increase primary nucleation density. Recently, chain-end modification has been proposed as an effective approach for regulating polymer crystal nucleation. However, the relevant nucleation mechanism still requires investigation. Therefore, in this work, 2-ureido-4[1H]-pyrimidinone (UPy) units, which can form stacks via quadruple hydrogen bonds with each other, are introduced as end groups for the preparation of interacting telechelic poly(butylene succinate) (PBS-UPy) oligomers with different molecular weights (Mns). The crystallization, especially the nucleation behavior of PBS-UPy, is studied in detail by comparing with the corresponding pre-polymer, the hydroxyl-terminal PBS (PBS-OH). The thermal properties of PBS-UPy exhibit similar Mn-dependent tendency to those of PBS-OH, but with weaker total crystallization rate. The spherulite growth rate is significantly reduced, whereas the primary nucleation density is highly promoted, after introducing UPy groups. Further investigation reveals that the mechanism of UPy stacks’ influence on nucleation ability changes from inhibition to promotion with respect to Mn. Even under an inhibition of nucleation ability, the final nucleation density is obviously increased because of a significant decline of the growth rate. In addition, the change in the impact of UPy stacks on nucleation ability is speculated to originate from the memory expression feasibility of ordered conformation in the melt during crystallization.

scholarly journals Poly(butylene succinate-co-butylene acetylenedicarboxylate): Copolyester with Novel Nucleation Behavior

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 365
Author(s):  
Yi Li ◽  
Guoyong Huang ◽  
Cong Chen ◽  
Xue-Wei Wei ◽  
Xi Dong ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Specific Interaction ◽  
Crystallization Rate ◽  
Amorphous Region ◽  
Nucleation Mechanism ◽  
Crystal Modification ◽  
Butylene Succinate ◽  
Nucleation Behavior ◽  
Primary Nucleation ◽  
New Type

Big spherulite structure and high crystallinity are the two main drawbacks of poly(butylene succinate) (PBS) and hinder its application. In this work, a new type of copolyester poly(butylene succinate-co-butylene acetylenedicarboxylate) (PBSAD) is synthesized. With the incorporation of acetylenedicarboxylate (AD) units into PBS chains, the crystallization temperature and crystallinity are depressed by excluding AD units to the amorphous region. In contrast, the primary nucleation capability is significantly strengthened, without changing the crystal modification or crystallization kinetics, leading to the recovery of total crystallization rate of PBSAD under the same supercooling condition. The existence of specific interaction among AD units is found to be crucial. Although it is too weak to contribute to the melt memory effect at elevated temperature, the interaction continuously strengthens as the temperature falls down, and the heterogeneous aggregation of AD units keeps growing. When the aggregating process reaches a certain extent, it will induce the formation of a significant amount of crystal nuclei. The unveiled nucleation mechanism helps to design PBS copolymer with good performance.

scholarly journals Monte Carlo Simulation for the Morphology and Kinetics of Spherulites and Shish-Kebabs in Isothermal Polymer Crystallization

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Chunlei Ruan ◽  
Chuntai Liu ◽  
Guoqiang Zheng
Keyword(s):  
Growth Rate ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Crystallization Rate ◽  
Polymer Crystallization ◽  
Nucleation Density ◽  
Length Growth ◽  
Average Size ◽  
Kinetics Of

Monte Carlo method is used to capture the evolution of spherulites and shish-kebabs and to predict the crystallization kinetics in isothermal polymer crystallization. Effects of nucleation density and growth rate of spherulites, nucleation density, and length growth rate of shish-kebabs, respectively, on crystallization are investigated. Results show that nucleation densities of both spherulites and shish-kebabs strongly affect crystallization rate as well as morphology. An increase in nucleation density of either spherulites or shish-kebabs leads to a quicker crystallization rate and a smaller average spherulite size. It is also shown that nucleation density of shish-kebabs has a stronger impact on crystallization rate. Growth rate of spherulites and length growth rate of shish-kebabs also have significant effect on crystallization rate and morphology. An increase in growth rate of spherulites or length growth rate of shish-kebabs also speeds up the crystallization rate; additionally, a decrease in growth rate of spherulites or an increase in length growth rate of shish-kebabs results in a more highly anisotropic shish-kebab structure and a smaller average size of spherulites. Results also show that the effect of growth rate of spherulites is more important than the effect of length growth rate of shish-kebabs on crystallization.

Effect of poly(vinyl alcohol) as an efficient crystallization-assisting agent on the enhanced crystallization rate of biodegradable poly(l-lactide)

RSC Advances ◽  
2015 ◽  
Vol 5 (61) ◽  
pp. 49216-49223 ◽  
Author(s):  
Yuping Zhao ◽  
Zhaobin Qiu
Keyword(s):  
Growth Rate ◽  
Vinyl Alcohol ◽  
Crystallization Rate ◽  
Poly Vinyl Alcohol ◽  
Nucleation Density ◽  
Biodegradable Poly

PVA increases both the nucleation density and the growth rate of PLLA spherulites in blends.

scholarly journals Assessment of Crystallinity Development during Fused Filament Fabrication through Fast Scanning Chip Calorimetry

2019 ◽  
Vol 9 (13) ◽  
pp. 2676 ◽  
Author(s):  
Dries Vaes ◽  
Margot Coppens ◽  
Bart Goderis ◽  
Wim Zoetelief ◽  
Peter Van Puyvelde
Keyword(s):  
Rapid Heating ◽  
Single Layer ◽  
Weld Strength ◽  
Fused Filament Fabrication ◽  
Crystalline Polymers ◽  
Molecular Weights ◽  
Heating And Cooling ◽  
Chip Calorimetry ◽  
The Impact ◽  
Fast Scanning Chip Calorimetry

Although semi-crystalline polymers are associated with considerably better mechanical properties and thermal stability compared to their amorphous counterparts, using them as feedstock for Fused Filament Fabrication still poses some major challenges. Hence, the development of printed part crystallinity during printing should be fully understood in order to control the developed weld strength, as well as part shrinkage and warpage. Infrared thermography was utilized to record the thermal history of deposited layers while printing a single-layer wall geometry, employing two PA 6/66 copolymers with distinct molecular weights as feedstock. Print settings were varied to establish which settings are essential to effectively monitor final part crystallinity. The resulting temperature profiles were simulated in a Fast Scanning Chip Calorimetry device that allows for the rapid heating and cooling rates experienced by the printed polymer. Both liquefier temperature and print speed were found to have very little influence on the total attained crystallinity. It became apparent that the build plate, set at a temperature above the polymer’s glass transition temperature, imposes a considerable annealing effect on the printed part. A reduced molecular weight was observed to enhance crystallinity even more strongly. The presented methodology proves that Fast Scanning Chip Calorimetry is an effective tool to assess the impact of both print parameters and feedstock characteristics on the crystallization behavior of semi-crystalline polymers over the course of printing.

International trade: Research of the reasons for the fall

2019 ◽  
pp. 79-91 ◽  
Author(s):  
V. S. Nazarov ◽  
S. S. Lazaryan ◽  
I. V. Nikonov ◽  
A. I. Votinov
Keyword(s):  
Growth Rate ◽  
International Trade ◽  
Exchange Rate ◽  
Global Economy ◽  
Structural Changes ◽  
Global Value Chains ◽  
Value Chains ◽  
Negative Contribution ◽  
Basic Commodity ◽  
The Impact

The article assesses the impact of various factors on the growth rate of international trade. Many experts interpreted the cross-border flows of goods decline against the backdrop of a growing global economy as an alarming sign that indicates a slowdown in the processes of globalization. To determine the reasons for the dynamics of international trade, the decompositions of its growth rate were carried out and allowed to single out the effect of the dollar exchange rate, the commodities prices and global value chains on the change in the volume of trade. As a result, it was discovered that the most part of the dynamics of international trade is due to fluctuations in the exchange rate of the dollar and prices for basic commodity groups. The negative contribution of trade within global value chains in 2014 was also revealed. During the investigated period (2000—2014), such a picture was observed only in the crisis periods, which may indicate the beginning of structural changes in the world trade.

scholarly journals The impact of non-pharmaceutical interventions on COVID-19 epidemic growth in the 37 OECD member states

2021 ◽  
Author(s):  
Francisco Pozo-Martin ◽  
Heide Weishaar ◽  
Florin Cristea ◽  
Johanna Hanefeld ◽  
Thurid Bahr ◽  
...  
Keyword(s):  
Growth Rate ◽  
Early Phase ◽  
Policy Decision ◽  
Multilevel Modelling ◽  
Daily Growth ◽  
Public Places ◽  
Member States ◽  
Unit Increase ◽  
Policy Decision Making ◽  
The Impact

AbstractWe estimated the impact of a comprehensive set of non-pharmeceutical interventions on the COVID-19 epidemic growth rate across the 37 member states of the Organisation for Economic Co-operation and Development during the early phase of the COVID-19 pandemic and between October and December 2020. For this task, we conducted a data-driven, longitudinal analysis using a multilevel modelling approach with both maximum likelihood and Bayesian estimation. We found that during the early phase of the epidemic: implementing restrictions on gatherings of more than 100 people, between 11 and 100 people, and 10 people or less was associated with a respective average reduction of 2.58%, 2.78% and 2.81% in the daily growth rate in weekly confirmed cases; requiring closing for some sectors or for all but essential workplaces with an average reduction of 1.51% and 1.78%; requiring closing of some school levels or all school levels with an average reduction of 1.12% or 1.65%; recommending mask wearing with an average reduction of 0.45%, requiring mask wearing country-wide in specific public spaces or in specific geographical areas within the country with an average reduction of 0.44%, requiring mask-wearing country-wide in all public places or all public places where social distancing is not possible with an average reduction of 0.96%; and number of tests per thousand population with an average reduction of 0.02% per unit increase. Between October and December 2020 work closing requirements and testing policy were significant predictors of the epidemic growth rate. These findings provide evidence to support policy decision-making regarding which NPIs to implement to control the spread of the COVID-19 pandemic.

scholarly journals The Impact of Policy Measures on Human Mobility, COVID-19 Cases, and Mortality in the US: A Spatiotemporal Perspective

2021 ◽  
Vol 18 (3) ◽  
pp. 996
Author(s):  
Yun Li ◽  
Moming Li ◽  
Megan Rice ◽  
Haoyuan Zhang ◽  
Dexuan Sha ◽  
...  
Keyword(s):  
Growth Rate ◽  
Human Mobility ◽  
Public Information ◽  
Key Factors ◽  
Information Campaigns ◽  
Rapid Spread ◽  
The Us ◽  
Policy Measures ◽  
The Impact ◽  
At Home

Social distancing policies have been regarded as effective in containing the rapid spread of COVID-19. However, there is a limited understanding of policy effectiveness from a spatiotemporal perspective. This study integrates geographical, demographical, and other key factors into a regression-based event study framework, to assess the effectiveness of seven major policies on human mobility and COVID-19 case growth rates, with a spatiotemporal emphasis. Our results demonstrate that stay-at-home orders, workplace closures, and public information campaigns were effective in decreasing the confirmed case growth rate. For stay-at-home orders and workplace closures, these changes were associated with significant decreases (p < 0.05) in mobility. Public information campaigns did not see these same mobility trends, but the growth rate still decreased significantly in all analysis periods (p < 0.01). Stay-at-home orders and international/national travel controls had limited mitigation effects on the death case growth rate (p < 0.1). The relationships between policies, mobility, and epidemiological metrics allowed us to evaluate the effectiveness of each policy and gave us insight into the spatiotemporal patterns and mechanisms by which these measures work. Our analysis will provide policymakers with better knowledge regarding the effectiveness of measures in space–time disaggregation.

scholarly journals Analysis of the Impact on the Mechanical Properties of Modification of Oligohydroxyethers in Organic Solvent Solution with Rubbers

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 519
Author(s):  
Vitalii Bezgin ◽  
Agata Dudek ◽  
Adam Gnatowski
Keyword(s):  
Mechanical Properties ◽  
Scientific Paper ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Molecular Weights ◽  
Wide Range ◽  
Strength Tests ◽  
Materials Used ◽  
Styrene Butadiene ◽  
The Impact

This paper proposes and presents the chemical modification of linear hydroxyethers (LHE) with different molecular weights (380, 640, and 1830 g/mol) with the addition of three types of rubbers (polysulfide rubber (PSR), polychloroprene rubber (PCR), and styrene-butadiene rubber (SBR)). The main purpose of choosing this type of modification and the materials used was the possibility to use it in industrial settings. The modification process was conducted for a very wide range of modifier additions (rubber) per 100 g LHE. The materials obtained in the study were subjected to strength tests in order to determine the effect of the modification on functional properties. Mechanical properties of the modified materials were improved after the application of the modifier (rubber) to polyhydroxyether (up to certain modifier content). The most favorable changes in the tested materials were registered in the modification of LHE-1830 with PSR. In the case of LHE-380 and LHE-640 modified in cyclohexanol (CH) and chloroform (CF) solutions, an increase in the values of the tested properties was also obtained, but to a lesser extent than for LHE-1830. The largest changes were registered for LHE-1830 with PSR in CH solution: from 12.1 to 15.3 MPa for compressive strength tests, from 0.8 to 1.5 MPa for tensile testing, from 0.8 to 14.7 MPa for shear strength, and from 1% to 6.5% for the maximum elongation. The analysis of the available literature showed that the modification proposed by the authors has not yet been presented in any previous scientific paper.

scholarly journals Poly(Lactic Acid)–Poly(Butylene Succinate)–Sugar Beet Pulp Composites; Part I: Mechanics of Composites with Fine and Coarse Sugar Beet Pulp Particles

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2531
Author(s):  
Rodion Kopitzky
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Sugar Beet ◽  
Cell Structure ◽  
Sugar Beet Pulp ◽  
Poly Lactic Acid ◽  
Butylene Succinate ◽  
Fracture Patterns ◽  
Beet Pulp ◽  
The Impact

Sugar beet pulp (SBP) is a residue available in large quantities from the sugar industry, and can serve as a cost-effective bio-based and biodegradable filler for fully bio-based compounds based on bio-based polyesters. The heterogeneous cell structure of sugar beet suggests that the processing of SBP can affect the properties of the composite. An “Ultra-Rotor” type air turbulence mill was used to produce SBP particles of different sizes. These particles were processed in a twin-screw extruder with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) and fillers to granules for possible marketable formulations. Different screw designs, compatibilizers and the use of glycerol as a thermoplasticization agent for SBP were also tested. The spherical, cubic, or ellipsoidal-like shaped particles of SBP are not suitable for usage as a fiber-like reinforcement. In addition, the fineness of ground SBP affects the mechanical properties because (i) a high proportion of polar surfaces leads to poor compatibility, and (ii) due to the inner structure of the particulate matter, the strength of the composite is limited to the cohesive strength of compressed sugar-cell compartments of the SBP. The compatibilization of the polymer–matrix–particle interface can be achieved by using compatibilizers of different types. Scanning electron microscopy (SEM) fracture patterns show that the compatibilization can lead to both well-bonded particles and cohesive fracture patterns in the matrix. Nevertheless, the mechanical properties are limited by the impact and elongation behavior. Therefore, the applications of SBP-based composites must be well considered.

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