Lamellar Growth in Melt-Crystallizing Polymers: Some Effect Related to a Nucleating Agent

2003 ◽  
pp. 366-377 ◽  
Author(s):  
Gaetano Di Marco ◽  
Marco Pieruccini
Keyword(s):  
Nucleating Agent ◽  
Lamellar Growth ◽  
Crystallizing Polymers

scholarly journals Effect of a nucleating agent on lamellar growth in melt-crystallizing polyethylene oxide

2003 ◽  
Vol 93 (9) ◽  
pp. 5839-5841 ◽  
Author(s):  
F. Aliotta ◽  
G. Di Marco ◽  
R. Ober ◽  
M. Pieruccini
Keyword(s):  
Polyethylene Oxide ◽  
Nucleating Agent ◽  
Lamellar Growth

scholarly journals Crystallization of Random Metallocene-Catalyzed Propylene-Based Copolymers with Ethylene and 1-Hexene on Rapid Cooling

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2091
Author(s):  
Daniela Mileva ◽  
Jingbo Wang ◽  
René Androsch ◽  
Katalee Jariyavidyanont ◽  
Markus Gahleitner ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Metallocene Catalyst ◽  
Nucleating Agent ◽  
Random Copolymers ◽  
Rapid Cooling ◽  
Significant Difference ◽  
Chip Calorimetry ◽  
High Cooling Rates ◽  
Fast Scanning Chip Calorimetry

Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates.

scholarly journals Fabrication and characterization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) modified with nano-montmorillonite biocomposite

e-Polymers ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 038-046
Author(s):  
Xu Yan ◽  
Wanru Zhou ◽  
Xiaojun Ma ◽  
Binqing Sun
Keyword(s):  
Thermal Stability ◽  
Oxygen Permeability ◽  
Water Vapor Permeability ◽  
Barrier Properties ◽  
Nucleating Agent ◽  
Vapor Permeability ◽  
Casting Method ◽  
Increasing Trend ◽  
Solution Casting Method

Abstract In this study, a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) modified with nano-montmorillonite biocomposite (MMT/PHBH) was fabricated by solution-casting method. The results showed that the addition of MMT increased the crystallinity and the number of spherulites, which indicated that MMT was an effective nucleating agent for PHBH. The maximum decomposition peak of the biocomposites moved to a high temperature and residue presented an increasing trend. The biocomposites showed the best thermal stability at 1 wt% MMT. Compared with PHBH, 182.5% and 111.2% improvement in elastic modulus and tensile strength were obtained, respectively. Moreover, the oxygen permeability coefficient and the water vapor permeability of MMT/PHBH biocomposites decreased by 43.9% and 6.9%, respectively. It was also found that the simultaneous enhancements on the crystallizing, thermal stability, mechanical, and barrier properties of biocomposites were mainly caused by the formation of intercalated structure between PHBH and MMT.

scholarly journals Effect of C-S-H Nucleating Agent on Cement Hydration

2021 ◽  
Vol 11 (14) ◽  
pp. 6638
Author(s):  
Wenhao Zhao ◽  
Xuping Ji ◽  
Yaqing Jiang ◽  
Tinghong Pan
Keyword(s):  
Fractal Dimension ◽  
Cement Hydration ◽  
Nucleating Agent ◽  
Crystal Nucleation ◽  
Enhancement Effect ◽  
Hydration Products ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Cement Mortars ◽  
Early Strength

This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

scholarly journals The Effect of Stereocomplex Polylactide Particles on the Stereocomplexation of High Molecular Weight Polylactide Blends

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2018
Author(s):  
Muhammad Samsuri ◽  
Ihsan Iswaldi ◽  
Purba Purnama
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Nucleating Agent ◽  
Solution Casting ◽  
Casting Method ◽  
Crystalline Fraction ◽  
Crystalline Structures ◽  
Solution Casting Method

Stereocomplexation is one of several approaches for improving polylactide (PLA) properties. The high molecular weight of poly L-lactide (PLLA) and poly D-lactide (PDLA) homopolymers are a constraint during the formation of stereocomplex PLAs (s-PLAs). The presence of s-PLA particles in PLA PLLA/PDLA blends can initiate the formation of s-PLA crystalline structures. We used the solution casting method to study the utilization of s-PLA materials from high molecular weight PLLA/PDLA blends for increasing s-PLA formation. The s-PLA particles initiated the formation of high molecular weight PLLA/PDLA blends, obtaining 49.13% s-PLA and 44.34% of the total crystalline fraction. In addition, the mechanical properties were enhanced through s-PLA crystalline formation and the increasing of total crystallinity of the PLLA/PDLA blends. The s-PLA particles supported initiation for s-PLA formation and acted as a nucleating agent for PLA homopolymers. These unique characteristics of s-PLA particles show potential to overcome the molecular weight limitation for stereocomplexation of PLLA/PDLA blends.

scholarly journals Preparation of Organic Crystal Seed and Its Application in Improving the Functional Period of Biodegradable Agricultural Film

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 826
Author(s):  
Runmeng Qiao ◽  
Xin Wang ◽  
Guangjiong Qin ◽  
Qi Liu ◽  
Jialei Liu ◽  
...  
Keyword(s):  
Degradation Rate ◽  
Low Cost ◽  
Water Vapor Permeability ◽  
Growth Period ◽  
Nucleating Agent ◽  
Degree Of Crystallinity ◽  
Vapor Permeability ◽  
Agricultural Films ◽  
Degradation Degree ◽  
Water Holding

White pollution caused by agricultural films has recently attracted great attention. In some areas, the content of micro plastic in the soil has reached 30 kg/ha. The most effective way to solve this problem is to replace traditional polyethylene agricultural films with degradable agricultural films. The consistency between the degradation rate and the crop growth period has become the biggest obstacle for the wide application of such novel agricultural films. In this paper, crystallinity regulation is used to adjust the functional period of degradable agricultural films. In addition, an organic nucleating agent of polyethylenimine (PEI) is selected by doping it to poly(butylene adipate-co-terephthalate) (PBAT) polymers using a double-screw extruder. The PBAT doped with 1 wt% PEI films revealed a significant increase in mechanical properties, water holding capacity, and crystallinity compared with the pure PBAT film. There was a 31.9% increase in tensile strength, a 30.5% increase in elongation at break, a 29.6% increase in tear resistance, a 30.9% decrease in water vapor permeability, and a 3.1% increase in crystallinity. Furthermore, the induction period of PBAT doped with 1 wt% PEI under photoaging (without soil) was about 160 h longer than PBAT film, and the experienced biodegradation in soil (without light) was 1 week longer than PBAT film. Experimental results exhibited that the change of degradation degree was linearly proportional to the degree of crystallinity. This study proposes a convenient, low-cost, and effective method to adjust the crystallinity and change the degradation rate.

scholarly journals Fly Ash Utilisation in Mullite Fabrication: Development of Novel Percolated Mullite

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 84
Author(s):  
Pramod Koshy ◽  
Naomi Ho ◽  
Vicki Zhong ◽  
Luisa Schreck ◽  
Sandor Alex Koszo ◽  
...  
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
Mineral Resources ◽  
Nucleating Agent ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Stable Phase ◽  
Power Stations ◽  
Firing Shrinkage

Fly ash is an aluminosilicate and the major by-product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al2O3·2SiO2) is the only stable phase in the Al2O3-SiO2 system and is used in numerous applications owing to its high-temperature chemical and mechanical stabilities. Hence, fly ash offers a potential economical resource for mullite fabrication, which is confirmed by a review of the current literature. This review details the methodologies to utilise fly ash with different additives to fabricate what are described as porous interconnected mullite skeletons or dense mullite bodies of approximately stoichiometric compositions. However, studies of pure fly ash examined only high-Al2O3 forms and none of these works reported long-term, high-temperature, firing shrinkage data for these mullite bodies. In the present work, high-SiO2 fly ashes were used to fabricate percolated mullite, which is demonstrated by the absence of firing shrinkage upon long-term high-temperature soaking. The major glass component of the fly ash provides viscosities suitably high for shape retention but low enough for ionic diffusion and the minor mullite component provides the nucleating agent to grow mullite needles into a direct-bonded, single-crystal, continuous, needle network that prevents high-temperature deformation and isolates the residual glass in the triple points. These attributes confer outstanding long-term dimensional stability at temperatures exceeding 1500 °C, which is unprecedented for mullite-based compositions.

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