scholarly journals Relaxation in Polyethylene: Orientation of Lamellar Crystals

1964 ◽  
Vol 36 (5) ◽  
pp. 1041-1041
Author(s):  
R. K. Eby ◽  
J. P. Colson
Keyword(s):  
Lamellar Crystals

Research on In Situ Anionic Polymerization of PA6/PI Alloy

2011 ◽  
Vol 295-297 ◽  
pp. 21-25
Author(s):  
Hong Kai Zhao ◽  
Li Guang Xiao ◽  
Hong Jie Wang
Keyword(s):  
Molecular Weight ◽  
Bisphenol A ◽  
High Performance ◽  
Hot Spot ◽  
Microscopic Analysis ◽  
Infrared Analysis ◽  
Elongation At Break ◽  
System Temperature ◽  
Lamellar Crystals

High performance trend of plastics has become a hot spot of current research. Select bisphenol A dianhydride and bisphenol A diamine with excellent water resistance as the reactant monomers to obtain anhydride-terminated polyimide with very high molecular weight by two-step polymerization, graft the active radicals of acyl caprolactam using the activity of anhydride and obtain PI modified nylon resin by polymerization.When the system temperature is above 160 °C and the added modifiers are greater than 10%, the system viscosity increases very fast; when the system temperature reaches 140 °C and the added modifiers are at 5%, the system viscosity increases very slowly. It is proved that the reaction in each above step is successful through infrared analysis. The mechanical properties of modified PI nylon increases with the increase of consumption and molecular weight of polyimide, when the molecular weight is selected to be about 8000~10000 and the adding amount is 10wt%~15 wt%, the tensile strength reaches over 85MPa, the notch impact strength is increased to 19.6kJ.m-2 and the elongation at break reaches 18%, which are remarkably better than general engineering plastics.Through microscopic analysis, the molecules of polyimide does not enter crystallization phase of nylon resin, but forms compact lamellar crystals existing in nylon matrix.

Self-Nucleation of β-Form Isotactic Polypropylene Lamellar Crystals in Thin Films

2021 ◽  
Author(s):  
Binghua Wang ◽  
Gang Wang ◽  
Shanshan He ◽  
Taicheng Sun ◽  
Jingbo Chen ◽  
...  
Keyword(s):  
Thin Films ◽  
Isotactic Polypropylene ◽  
Lamellar Crystals

scholarly journals Double-Twisted Helical Lamellar Crystals in a Synthetic Main-Chain Chiral Polyester Similar to Biological Polymers. Volume 32, Number 2, January 26, 1999, pp 524−527.

2000 ◽  
Vol 33 (2) ◽  
pp. 647-647
Author(s):  
Chritopher Y. Li ◽  
Donghang Yan ◽  
Stephen Z. D. Cheng ◽  
Feng Bai ◽  
Tianbai He ◽  
...  
Keyword(s):  
Main Chain ◽  
Biological Polymers ◽  
Lamellar Crystals

scholarly journals Competition between crystal growth and intracrystalline chain diffusion determines the lamellar thickness in semicrystalline polymers

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Martha Schulz ◽  
Mareen Schäfer ◽  
Kay Saalwächter ◽  
Thomas Thurn-Albrecht
Keyword(s):  
Decisive Role ◽  
Semicrystalline Polymers ◽  
Lamellar Thickness ◽  
Polarization Microscopy ◽  
Polymer Systems ◽  
X Ray Scattering ◽  
Special Cases ◽  
Lamellar Crystals ◽  
Nmr Methods

AbstractThe non-equilibrium thickness of lamellar crystals in semicrystalline polymers varies significantly between different polymer systems and depends on the crystallization temperature Tc. There is currently no consensus on the mechanism of thickness selection. Previous work has highlighted the decisive role of intracrystalline chain diffusion (ICD) in special cases, but a systematic dependence of lamellar thickness on relevant timescales such as that of ICD and stem attachment has not yet been established. Studying the morphology by small-angle X-ray scattering and the two timescales by NMR methods and polarization microscopy respectively, we here present data on poly(oxymethylene), a case with relatively slow ICD. It fills the gap between previously studied cases of absent and fast ICD, enabling us to establish a quantitative dependence of lamellar thickness on the competition between the noted timescales.

Research on Performance of Polyimide In Situ Modification Anionic Polymerization Nylon 6

2014 ◽  
Vol 1052 ◽  
pp. 242-248
Author(s):  
Hong Kai Zhao ◽  
Hong Li Wang
Keyword(s):  
Bisphenol A ◽  
Water Absorption ◽  
In Situ Polymerization ◽  
Microscopic Analysis ◽  
Nylon 6 ◽  
Grafting Reaction ◽  
Lamellar Crystals ◽  
End Capping ◽  
Short Time

Through the polymerization and grafting reaction of bisphenol A dianhydride and bisphenol A diamine, the polyimide activator (PI activator) of acyl caprolactam end capping is obtained and then the anionic in-situ polymerization modified nylon 6 resin is obtained. Viscosity analysis shows that PI consumption is higher than 0.1 (of monomer mass), the reaction temperature is higher than 160°C, the viscosity rises rapidly in a short time and the rapid polymerization molding can be realized; when PI consumption is higher than 0.15 (of monomer mass), the water absorption of matrix resin will be lower than 1.4%; compared with the nylon resin, its water absorption is significantly lowered and its mechanical property is improved greatly; microscopic analysis shows that PI molecules fail to enter the crystalline phase of the nylon 6 and form lamellar crystals in the nylon matrix, which plays a role of enhancement and obstruction; differential thermal analysis shows that PI reduces the melting enthalpy and melting point temperature of nylon 6 resin, which indicates that PI reduces the crystallization capacity of nylon 6.

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