scholarly journals Synergistic lignin construction of a long-chain branched polypropylene and its properties

RSC Advances ◽  
2020 ◽  
Vol 10 (62) ◽  
pp. 38120-38127
Author(s):  
Bo Tian ◽  
Jinfeng Li ◽  
Zhigang Li ◽  
Ningdi Xu ◽  
Gang Yao ◽  
...  
Keyword(s):  
Chain Branching ◽  
Long Chain Branching ◽  
Foaming Property ◽  
Branched Polypropylene ◽  
Long Chain ◽  
Long Chain Branched Polypropylene

Polypropylene with long chain branching behavior was constructed by lignin, which foaming property and polarity were improved.

Novel Dynamically Vulcanized Elastomer-Polypropylene Blends with Improved Elasticity

2003 ◽  
Vol 76 (1) ◽  
pp. 202-211 ◽  
Author(s):  
M. D. Ellul
Keyword(s):  
Residual Deformation ◽  
Thermoplastic Elastomer ◽  
Chain Branching ◽  
Low Frequencies ◽  
Long Chain Branching ◽  
Rubber Phase ◽  
Polypropylene Blends ◽  
Branched Polypropylene ◽  
Long Chain ◽  
Long Chain Branched Polypropylene

Abstract High elasticity in dynamically vulcanized EPDM-Polypropylene blends, as demonstrated by lower residual deformation upon release of constraint, is a much desired attribute. It has been found that this property can be improved beyond the conventional norms of highly crosslinking the rubber phase. This is achieved through the use of a polypropylene phase with a high degree of long-chain branching. The branching index, g', at molecular weight greater than 1×106 should be less than about 0.6. It is postulated that in the melt and at low frequencies the long-chain branched polypropylene behaves as a network. Therefore in the melt, the dynamically vulcanized alloy behaves as a dual network material: one network being the chemically crosslinked rubber phase, and the other being the physical network arising from the high level of long-chain branching in polypropylene. In the solid state, the co-continuous morphology arising from the choice of long-chain branched polypropylene contributes to the enhanced elasticity of the dynamically vulcanized thermoplastic elastomer.

Influence of molecular structure on the foamability of polypropylene: Linear and extensional rheological fingerprint

2017 ◽  
Vol 54 (3) ◽  
pp. 515-543 ◽  
Author(s):  
Ebrahim Bahreini ◽  
Seyed Foad Aghamiri ◽  
Manfred Wilhelm ◽  
Mahdi Abbasi
Keyword(s):  
Molecular Structure ◽  
Small Amplitude ◽  
Function Model ◽  
Chain Branching ◽  
Small Amplitude Oscillatory Shear ◽  
Long Chain Branching ◽  
Molecular Stress Function ◽  
Branched Polypropylene ◽  
Long Chain ◽  
Long Chain Branched Polypropylene

The foaming structure and rheological properties of four different isotactic homo-polypropylenes with various molecular weights and an isotactic long chain branched polypropylene were investigated to find a suitable rheological fingerprint for PP foams. The molecular weight distribution and thermal properties were measured using GPC-MALLS and differential scanning calorimetry, respectively. Small amplitude oscillatory shear data and uniaxial extensional experiments were analyzed using the frameworks of van Gurp-Palmen plot (δ vs. | G*|) and the molecular stress function model, respectively. These analyses were used to find a correlation between the molecular structure, rheological properties and foaming structures of linear and long chain branching polypropylenes. Two linear viscoelastic characteristics, | G*| at δ = 60° and | η*| at ω = 5 rad/s were used as criteria for foamability of these polymers, where decreasing of both parameters by increasing the long chain branching content results in smaller cell size and higher cell density. The molecular stress function model was able to quantify the strain hardening properties of long chain branching blends using small amplitude oscillatory shear data and two nonlinear material parameters, 1 ≤  β ≤ 2.2 and 1 ≤ [Formula: see text] ≤ 600, where the minimum and maximum values of these parameters belong to the linear and long chain branched polypropylene, respectively. Increasing the long chain branched polypropylene content of the PP blends increased strain hardening, and therefore improved the foaming characteristics significantly by suppressing the coalescence of cells. Dilution of linear PP with only 10 wt% of long chain branched polypropylene enhanced the cell density from 5.7 × 106 to 2.7 × 107 cell/cm3 and reduced the average cell diameter from 58 to 26 µm, respectively, while their volume expansion ratio remained in the same range of 2–3. Increasing of long chain branching to 50 and 100 wt% enhanced the V.E.R. to 6.2 and 7.8, respectively.

scholarly journals Influence of Different Types of Peroxides on the Long-Chain Branching of PP via Reactive Extrusion

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 886 ◽  
Author(s):  
Sascha Stanic ◽  
Gergö Gottlieb ◽  
Thomas Koch ◽  
Lukas Göpperl ◽  
Klaus Schmid ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Gel Permeation Chromatography ◽  
Reactive Extrusion ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Single Screw Extruder ◽  
Strength Behavior ◽  
Different Temperatures ◽  
Branched Polypropylene ◽  
Long Chain

Long-chain branching (LCB) is known as a suitable method to increase the melt strength behavior of linear polypropylene (PP), which is a fundamental weakness of this material. This enables the modification of various properties of PP, which can then be used—in the case of PP recyclates—as a practical “upcycling” method. In this study, the effect of five different peroxides and their effectiveness in building LCB as well as the obtained mechanical properties were studied. A single screw extruder at different temperatures (180 and 240 °C) was used, and long-chain branched polypropylene (PP-LCB) was prepared via reactive extrusion by directly mixing the peroxides. The peroxides used were dimyristyl peroxydicarbonate (PODIC C126), tert-butylperoxy isopropylcarbonate (BIC), tert-Butylperoxy 2-ethylhexyl carbonate (BEC), tert-amylperoxy 2-ethylhexylcarbonate (AEC), and dilauroyl peroxide (LP), all with a concentration of 20 mmol/kg. The influence of the temperature on the competitive prevalent reactions of degradation and branching was documented via melt mass-flow rate (MFR), rheology measurements, and gel permeation chromatography (GPC). However, via extensional rheology, strain hardening could be observed in all cases and the mechanical properties could be maintained or even improved. Particularly, PODIC C126 and LP signaled a promising possibility for LCB in this study.

Characterization of long chain branching: Dilution rheology of industrial polyethylenes

2002 ◽  
Vol 46 (2) ◽  
pp. 401-426 ◽  
Author(s):  
B. J. Crosby ◽  
M. Mangnus ◽  
W. de Groot ◽  
R. Daniels ◽  
T. C. B. McLeish
Keyword(s):  
Chain Branching ◽  
Long Chain Branching ◽  
Long Chain

Character of long-chain branching in highly purified natural rubber

2010 ◽  
Vol 115 (6) ◽  
pp. 3645-3650 ◽  
Author(s):  
Sureerut Amnuaypornsri ◽  
Lucksanaporn Tarachiwin ◽  
Jitladda T. Sakdapipanich
Keyword(s):  
Natural Rubber ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Long Chain

The effect of long chain branching on the processability of polypropylene in thermoforming

2004 ◽  
Vol 44 (5) ◽  
pp. 973-982 ◽  
Author(s):  
A. D. Gotsis ◽  
B. L. F. Zeevenhoven ◽  
A. H. Hogt
Keyword(s):  
Chain Branching ◽  
Long Chain Branching ◽  
Long Chain
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