Synthesis of polypropylene with varied microstructure and molecular weights characteristics using supported titanium catalyst system

2010 ◽  
Vol 18 (2) ◽  
pp. 235-239 ◽  
Author(s):  
Priyanshu B. Vyas ◽  
Sukhdeep Kaur ◽  
Harshad R. Patil ◽  
Virendra K. Gupta
Keyword(s):  
Catalyst System ◽  
Titanium Catalyst ◽  
Molecular Weights

scholarly journals Synthesis of High cis-Polybutadiene in Styrene Solution with Neodymium-Based Catalysts: Towards the Preparation of HIPS and ABS via In Situ Bulk Polymerization

2016 ◽  
Vol 2016 ◽  
pp. 1-11
Author(s):  
Ramón Díaz de León ◽  
Florentino Soriano Corral ◽  
Francisco Javier Enríquez-Medrano ◽  
Gabriela Bosques Ibarra ◽  
Patricia de León Martínez ◽  
...  
Keyword(s):  
Catalyst System ◽  
Bulk Polymerization ◽  
Activation Process ◽  
Morphological Development ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Butadiene Polymerization ◽  
Melting Endotherm ◽  
Synthesized Materials

In a first step, 1,3-butadiene was selectively polymerized at 60°C in styrene as solvent using NdV3/DIBAH/EASC as the catalyst system. The catalyst system activation process, the addition order of monomers and catalyst components, and the molar ratios [Al]/[Nd] and [Cl]/[Nd] were studied. The catalyst system allowed the selective 1,3-butadiene polymerization, reaching conversions between 57.5 and 88.1% with low polystyrene contents in the order of 6.3 to 15.4%. Molecular weights ranging from 39,000 to 150,000 g/mol were obtained, while cis-1,4 content was found in the interval of 94.4 to 96.4%. On the other hand, the glass transition temperatures of synthesized materials were established in the range of −101.9 to −107.4°C, explained by the presence of polystyrene segments in the polybutadiene chains; in the same sense, the polybutadienes did not show the typical melting endotherm of high cis-polybutadienes. In a second step, the resulting styrene/high cis-1,4 polybutadiene solutions were used to synthesize ABS (adding a fraction of acrylonitrile monomer) and HIPS via in situ bulk polymerizations and the results were discussed in terms of morphological development, molecular parameters, dynamical mechanical behavior, and mechanical properties.

Dependence of Tack Strength on Molecular Properties

1959 ◽  
Vol 32 (1) ◽  
pp. 48-66 ◽  
Author(s):  
W. G. Forbes ◽  
L. A. McLeod
Keyword(s):  
Molecular Weight ◽  
Shear Viscosity ◽  
Catalyst System ◽  
Chain Entanglement ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
The Difference ◽  
Catalyst Systems ◽  
Time Required ◽  
Butadiene Styrene

Abstract A method has been developed for the measurement of the tack strength of fresh and reproducibly smooth rubber surfaces. Using this method the tack strength of natural rubber is shown to be independent of polymer purity, and, to a large extent, Mooney viscosity, intrinsic viscosity, gel content and molecular weight distribution. The relative tack strengths of polyisoprenes of different molecular weights prepared in different catalyst systems are measured. The results are discussed in terms of microstructure. A study of the tack strength of oil-extended butadiene-styrene copolymers indicates that relative tack strength is related to the shear viscosity of the bulk polymer. Measurements of relative tack strength on Alfin and free radical butadiene-styrene copolymers, butyl, brominated butyl and butadiene-acrylonitrile copolymers confirm the inportance of shear viscosity in controlling tack strength. Choice of catalyst system and temperature of polymerization cause the largest variation in polymer viscosity. The contact time required for the relative tack strength to become unity is shown to be inversely dependent upon the value of the relative tack strength itself. Shear viscosity measurements are given for six classes of polymer and the values shown to correlate with relative tack strength. It is postulated that molecular weight (and probably also chain entanglement) is the controlling variable. The bond strength between two different uncured polymers is shown to depend upon the difference in cohesive energy densities of the two polymers.

Stabilized polypropylene synthesis using supported titanium catalyst system in presence of phenolic compounds

2014 ◽  
Vol 17 (6) ◽  
pp. 582-589 ◽  
Author(s):  
Ajay Vinodlal Kothari ◽  
Umesh Chhaganlal Makwana ◽  
Bhavesh Kiritbhai Desai ◽  
Virendra Kumar Gupta
Keyword(s):  
Phenolic Compounds ◽  
Catalyst System ◽  
Titanium Catalyst

Melt Polycondensation and Analysis of Hydroxyl-Terminated Poly(L-lactic Acid) Using Small Molecular Diols as Terminating Agents

2013 ◽  
Vol 328 ◽  
pp. 890-894
Author(s):  
Jing Che ◽  
Rong Jie Yang
Keyword(s):  
Lactic Acid ◽  
Ethylene Glycol ◽  
Gel Permeation Chromatography ◽  
Catalyst System ◽  
Molecular Weights ◽  
H Nmr ◽  
Melt Polycondensation ◽  
Direct Melt Polycondensation ◽  
Group Structures ◽  
End Group

The synthesis of hydroxyl-terminated poly (L-lactic acid) (PLLA) by direct melt polycondensation of L-lactic acid and use of small molecular diols as terminating agents was investigated. L-lactic acid was dewatered to prepare the dehydrated prepolymer at first. Then PLLA was prepared through melt polycondensation in a melt with catalyst system including TSA, SnCl2and Sn (Oct)2. Finally, ethylene glycol, 1,4-butanediol, and 1,8-octanediol, respectively, were used in hydroxyl termination of the PLLA. The molecular weights and end-group structures of all products were characterized by gel permeation chromatography (GPC) and1H-NMR. DSC and Disc Polarimeter were used to characterize crystallinity and racemization, respectively. The results show that two kinds of hydroxyl-terminated PLLA polymers were obtained: complete hydroxyl-terminated PLLA prepared by using ethylene glycol or 1,4-butanediol, incomplete hydroxyl-terminated PLLA prepared by using 1,8-octanediol or combination of two kinds of diols. Combination of ethylene glycol or 1,4-butanediol with 1,8-octanediol can reach high hydroxyl termination of PLLA, and maintain the molecular weight by decrease of alcoholysis at the same time.1H-NMR was found as an effective estimating way for extents of reactions. The hydroxyl-terminating reactions of PLLA by the diols reduced the crystallinity and resulted in racemization to some extent.

Effect of an external donor upon chain-transfer reactions in propylene polymerization with a MgCl2-supported titanium catalyst system

Polymer ◽  
1998 ◽  
Vol 39 (25) ◽  
pp. 6309-6313 ◽  
Author(s):  
Shin-ichi Kojoh ◽  
Toshiyuki Tsutsui ◽  
Norio Kashiwa ◽  
Masaaki Itoh ◽  
Akira Mizuno
Keyword(s):  
Chain Transfer ◽  
Catalyst System ◽  
Propylene Polymerization ◽  
Transfer Reactions ◽  
External Donor ◽  
Titanium Catalyst
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