Blends of Linear and Long-Chain Branched Poly(l-lactide)s with High Melt Strength and Fast Crystallization Rate

2012 ◽  
Vol 51 (30) ◽  
pp. 10088-10099 ◽  
Author(s):  
Liangyan Wang ◽  
Xiabin Jing ◽  
Haibo Cheng ◽  
Xiuli Hu ◽  
Lixin Yang ◽  
...  
Keyword(s):  
Crystallization Rate ◽  
Melt Strength ◽  
Long Chain

scholarly journals Star Shaped Long Chain Branched Poly (lactic acid) Prepared by Melt Transesterification with Trimethylolpropane Triacrylate and Nano-ZnO

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 796 ◽  
Author(s):  
Le Yang ◽  
Zaijun Yang ◽  
Feng Zhang ◽  
Lijin Xie ◽  
Zhu Luo ◽  
...  
Keyword(s):  
Lactic Acid ◽  
High Efficiency ◽  
Synergistic Effects ◽  
Transesterification Reaction ◽  
Poly Lactic Acid ◽  
Cell Diameter ◽  
Nano Zno ◽  
Melt Strength ◽  
Trimethylolpropane Triacrylate ◽  
Long Chain

Long chain branched poly (lactic acid) (LCBPLA) was prepared via transesterification between high molecular weight poly (lactic acid) (PLA) and low molar mass monomer trimethylolpropane triacrylate (TMPTA) during melt blending in the presence of zinc oxide nanoparticles (nano-ZnO) as a transesterification accelerant in a torque rheometer. Compared with the traditional processing methods, this novel way is high-efficiency, environmentally friendly, and gel-free. The results revealed that chain restructuring reactions occurred and TMPTA was grafted onto the PLA backbone. The topological structures of LCBPLA were verified and investigated in detail. It was found that the concentration of the accelerants and the sampling occasion had very important roles in the occurrence of branching structures. When the nano-ZnO dosage was 0.4 phr and PLA was sampled at the time corresponding to the reaction peak in the torque curve, PLA exhibited a star-shaped topological structure with a high branching degree which could obviously affect the melt strength, extrusion foaming performances, and crystallization behaviors. Compared with pristine PLA, LCBPLA showed a higher melt strength, smaller cell diameter, and slower crystallization speed owing to the synergistic effects of nano-ZnO and the long chain branches introduced by the transesterification reaction in the system. However, severe degradation of the LCBPLAs would take place under a mixing time that was too long and lots of short linear chains generated due to the excessive transesterification reaction, with a sharp decline in melt strength.

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.

Origin of Characteristic Properties of Natural Rubber—Synergistic Effect of Fatty Acids on Crystallization of cis-1,4-Polyisoprene: II, Mixed and Esterified Fatty Acids in Natural Rubber

1996 ◽  
Vol 69 (4) ◽  
pp. 608-614 ◽  
Author(s):  
Naoyuki Nishiyama ◽  
Seiichi Kawahara ◽  
Takashi Kakubo ◽  
Eng Aik Hwee ◽  
Yasuyuki Tanaka
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Natural Rubber ◽  
Free Fatty Acids ◽  
Crystallization Rate ◽  
Chain Fatty Acid ◽  
Long Chain Fatty Acid ◽  
Esterified Fatty Acids ◽  
Deproteinized Natural Rubber ◽  
Long Chain

Abstract Crystallization behavior of deproteinized natural rubber at −25°C was investigated by dilatometry in connection with the effect of long-chain fatty acid groups, esterified to the rubber chain, as well as free fatty acids and their esters. The overall crystallization rate decreased after removal of the acetone-extractable free fatty acids and their esters, while it increased significantly when the fatty acid groups esterified to natural rubber molecule were removed by transesterification with sodium methoxide. Both the acetone-extracted and transesterified rubbers showed a significant increase in the overall crystallization rate after the addition of 1 wt % stearic acid. The crystallization of acetone-extracted rubber was accelerated by the addition of 1 wt % methyl linoleate, a plasticizer of natural rubber, whereas it was suppressed in the case of transesterified rubber in which the esterified fatty acid groups were removed completely. The fatty acid groups esterified to natural rubber molecule gave rise to the accelerated crystallization of the rubber in conjunction with free fatty acids and their esters.

Enhancing crystallization rate and melt strength of PLLA with four-arm PLLA grafted silica: The effect of molecular weight of the grafting PLLA chains

2017 ◽  
Vol 135 (2) ◽  
pp. 45675 ◽  
Author(s):  
Xiang-Ling Lai ◽  
Wei Yang ◽  
Zhao Wang ◽  
Da-Wei Shi ◽  
Zheng-Ying Liu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Crystallization Rate ◽  
Melt Strength

Improvement of Melt Strength and Crystallization Rate of Polylactic Acid and its Blends

2014 ◽  
Vol 70 (8) ◽  
pp. 38-42 ◽  
Author(s):  
Manoj Nerkar ◽  
Juliana Ramsay ◽  
Marianna Kontopoulou ◽  
Bruce Ramsay
Keyword(s):  
Polylactic Acid ◽  
Crystallization Rate ◽  
Melt Strength

scholarly journals Expanded Beads of High Melt Strength Polypropylene Moldable at Low Steam Pressure by Foam Extrusion

Polymers ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 205
Author(s):  
Daniele Tammaro ◽  
Alberto Ballesteros ◽  
Claudio Walker ◽  
Norbert Reichelt ◽  
Ulla Trommsdorff
Keyword(s):  
Ad Hoc ◽  
Steam Pressure ◽  
Molding Pressure ◽  
Cell Content ◽  
Melt Strength ◽  
Foam Extrusion ◽  
Molded Parts ◽  
Cost Efficient ◽  
Line Design ◽  
Long Chain

We explore the foam extrusion of expanded polypropylene with a long chain branched random co-polypropylene to make its production process simpler and cheaper. The results show that the presence of long chain branches infer high melt strength and, hence, a wide foamability window. We explored the entire window of foaming conditions (namely, temperature and pressure) by means of an ad-hoc extrusion pilot line design. It is shown that the density of the beads can be varied from 20 to 100 kg/m3 using CO2 and isobutane as a blowing agent. The foamed beads were molded by steam-chest molding using moderate steam pressures of 0.3 to 0.35 MPa independently of the closed cell content. A characterization of the mechanical properties was performed on the molded parts. The steam molding pressure for sintering expanded polypropylene beads with a long chain branched random co-polypropylene is lower than the one usually needed for standard polypropylene beads by extrusion. The energy saving for the sintering makes the entire manufacturing processes cost efficient and can trigger new applications.

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