scholarly journals In situ ozonolysis of polypropylene during extrusion to produce long-chain branches with the aid of TMPTA

RSC Advances ◽  
2017 ◽  
Vol 7 (36) ◽  
pp. 22531-22539 ◽  
Author(s):  
Guang-Jian He ◽  
Bing-Yu Yuan ◽  
Ting-Ting Zheng ◽  
Wen-li Zhu ◽  
Xiao-Chun Yin
Keyword(s):  
Extrusion Process ◽  
Secondary Products ◽  
Long Chain

The introduction of long-chain branches (LCBs) in polypropylene (PP) during the extrusion process is normally induced by peroxide chemicals which are known to cause to the formation of secondary products in the resin.

Biophysics (and sociology) of ceramides.

2005 ◽  
Vol 72 ◽  
pp. 177-188 ◽  
Author(s):  
Félix M. Goñi ◽  
F-Xabier Contreras ◽  
L-Ruth Montes ◽  
Jesús Sot ◽  
Alicia Alonso
Keyword(s):  
Cell Biology ◽  
Positive Curvature ◽  
Acyl Chain ◽  
Cell Signalling ◽  
Hexagonal Structure ◽  
Lipid Monolayer ◽  
Flip Flop ◽  
Long Chain ◽  
Bilayer Permeability

In the past decade, the long-neglected ceramides (N-acylsphingosines) have become one of the most attractive lipid molecules in molecular cell biology, because of their involvement in essential structures (stratum corneum) and processes (cell signalling). Most natural ceramides have a long (16-24 C atoms) N-acyl chain, but short N-acyl chain ceramides (two to six C atoms) also exist in Nature, apart from being extensively used in experimentation, because they can be dispersed easily in water. Long-chain ceramides are among the most hydrophobic molecules in Nature, they are totally insoluble in water and they hardly mix with phospholipids in membranes, giving rise to ceramide-enriched domains. In situ enzymic generation, or external addition, of long-chain ceramides in membranes has at least three important effects: (i) the lipid monolayer tendency to adopt a negative curvature, e.g. through a transition to an inverted hexagonal structure, is increased, (ii) bilayer permeability to aqueous solutes is notoriously enhanced, and (iii) transbilayer (flip-flop) lipid motion is promoted. Short-chain ceramides mix much better with phospholipids, promote a positive curvature in lipid monolayers, and their capacities to increase bilayer permeability or transbilayer motion are very low or non-existent.

Development of high melt strength polypropylene and its application in thermoplastic elastomeric composition

2021 ◽  
pp. 009524432110510
Author(s):  
Mousumi De Sarkar ◽  
Nishant Chandel ◽  
Shib Shankar Banerjee ◽  
Subhabrata Saha ◽  
Anil K Bhowmick ◽  
...  
Keyword(s):  
Fixed Ratio ◽  
Reactive Extrusion ◽  
Extrusion Process ◽  
Structure Property ◽  
Chain Branching ◽  
Melt Strength ◽  
Long Chain Branching ◽  
Zinc Diethyldithiocarbamate ◽  
Long Chain ◽  
High Melt Strength Polypropylene

High melt strength polypropylene (HMS-PP) with a long-chain branched structure is a modified form of polypropylene (PP) which has basic properties of regular PP but with superior melt drawability. This paper reports on the development of gel-free HMS-PP from a linear isotactic PP through the introduction of long-chain branching on its backbone via a reactive extrusion process, using dicetyl-peroxydicarbonate (PODIC) alone or in combination with a coagent. The melt strength and the mechanical properties such as impact and flexural strength of PP showed improvements with the modification with PODIC. 5000 ppm by weight of PODIC was found to provide the best balance of properties. The efficacies of zinc diethyldithiocarbamate (ZDC) and tetramethyl thiuram disulphide (TMTD) as coagents in combination with PODIC to augment properties of HMS-PP further were explored. TMTD offered slightly enhanced performance benefits as compared to ZDC at an optimized concentration of 100 ppm by weight. The application potential of HMS-PP in thermoplastic elastomeric blends of HMS-PP with ethylene-propylene-diene monomer (EPDM) rubber at a fixed ratio of 35/65 by weight was also investigated. Structure-property correlations were established between the extent of long-chain branching in the modified PP and the properties of the resultant thermoplastic elastomeric composition.

scholarly journals Scalable High Refractive Index polystyrene-sulfur nanocomposites via in situ inverse vulcanization

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Vijay S. Wadi ◽  
Kishore K. Jena ◽  
Kevin Halique ◽  
Brigita Rožič ◽  
Luka Cmok ◽  
...  
Keyword(s):  
Refractive Index ◽  
Low Cost ◽  
High Refractive Index ◽  
Extrusion Process ◽  
Melt Processing ◽  
Process Formation ◽  
Polystyrene Matrix ◽  
One Step ◽  
Extrusion Method

Abstract In this work, we demostrate the preparation of low cost High Refractive Index polystyrene-sulfur nanocomposites in one step by combining inverse vulcanization and melt extrusion method. Poly(sulfur-1,3-diisopropenylbenzene) (PS-SD) copolymer nanoparticles (5 to 10 wt%) were generated in the polystyrene matrix via in situ inverse vulcanization reaction during extrusion process. Formation of SD copolymer was confirmed by FTIR and Raman spectroscopy. SEM and TEM further confirms the presence of homogeneously dispersed SD nanoparticles in the size range of 5 nm. Thermal and mechanical properties of these nanocomposites are comparable with the pristine polystyrene. The transparent nanocomposites exhibits High Refractive Index n = 1.673 at 402.9 nm and Abbe’y number ~ 30 at 10 wt% of sulfur loading. The nanocomposites can be easily processed into mold, films and thin films by melt processing as well as solution casting techniques. Moreover, this one step preparation method is scalable and can be extend to the other polymers.

scholarly journals Delaminated Polymer/Lamellar Aluminophosphate Nanocomposites Prepared via in SITU Polymerization

2006 ◽  
Vol 15 (5) ◽  
pp. 096369350601500 ◽  
Author(s):  
Jingyu Wang ◽  
Guoping Chen ◽  
Quan Zhou
Keyword(s):  
Polymer Matrix ◽  
In Situ Polymerization ◽  
Short Chain ◽  
Long Chain

A method to synthesize completely delaminated polymer/lamellar aluminophosphate (Mu-4) nanocomposites has been successfully developed, wherein organo-modification of Mu-4 followed by in situ polymerization was applied. It can be found that the long chain n-dodecylamine molecules can favor the intercalation of Mu-4 and thus readily make the Mu-4 layers delaminated in the polymer matrix compared with the short chain N,N-dimethylpropane-1,3-diamine.

scholarly journals Properties of „In Situ” 7475 Alloy Matrix Composites Reinforced Al3Ti Intermetalic Compound Extruded in Semi-Solid State

2016 ◽  
Vol 61 (1) ◽  
pp. 433-438 ◽  
Author(s):  
W. Szymański
Keyword(s):  
Heat Treatment ◽  
Solid State ◽  
Aluminium Alloy ◽  
Extrusion Process ◽  
Liquid Aluminium ◽  
Alloy Matrix ◽  
Electron Microscopies ◽  
Semi Solid ◽  
Composite Hardness

Studies were conducted to improve the mechanical properties of composites based on 7475 aluminium alloy reinforced with Al3Ti particles fabricated by the “in situ” process. The first step involved “dissolving” of titanium in the liquid aluminium alloy and fabricating in this way composite materials with different content of the reinforcing phase (15-45wt%). A relationship between the composite hardness and content of the reinforcing phase was confirmed. The second step involved the improvement of cohesion between the reinforcing particles and composite matrix. By extrusion of samples in semi-solid state, an average increase in hardness by 15-20% relative to the unextruded composite was obtained. In the third step, the fabricated composite was subjected to a heat treatment corresponding to the state T6 in 7475 alloy, which raised the hardness by about 30%. Structure examinations carried out by means of optical microscopy and scanning electron microscopies as well as the results of hardness measurements were described. They enabled estimating the effect of the content of produced Al3Ti particles, and of the extrusion process in semi-solid state and heat treatment parameters on the composite properties. In compression test, the yield strength and compressive strength of the heat-treated composites were determined.

Synthesis and Characterization of Copper(II) Complexes with Long Chain Dithiocarbamates

2014 ◽  
Vol 976 ◽  
pp. 164-168 ◽  
Author(s):  
Nayely Torres-Gomez ◽  
Alfredo R. Vilchis-Nestor ◽  
Rosa Maria Gomez-Espinosa ◽  
Ivan Garcia-Orozco
Keyword(s):  
Infrared Spectroscopy ◽  
Copper Complexes ◽  
Nanocrystalline Structure ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Chain ◽  
Scanning Electron

Copper complexes of dithiocarbamates ligands were obtained from RNH2 (R = C6H13-, C12H25- y C18H37-) and an excess of CS2 in the presence of NaOH. Sodium hexyldithiocarbamate is not possible to isolate from solution but the other two were obtained and characterizedby infrared spectroscopy, UV-vis and powder X-ray diffraction. Copper complexes were obtained in situ from ligand solution as greenish powders. All the complexes were characterized by infrared spectroscopy, UV-vis, powder X-ray diffraction and Scanning Electron Microscopy. The complexes show an amorphous phase in the case of DCu12 and nanocrystalline structure for DCu18, as observed in XRD.

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