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Better Choice:Linear Long chains Rather than Branched Ones to Improve Mechanical Performance of Polyethylene through Generating Shish-Kebabs

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Chinese Journal of Polymer Science 2020年第7期38卷 715-729,I0006页

作者： Lu-Feng Deng Xi-Xi Zhang Dong Zhou Jian-Hua Tang Jun Lei Jun-Fang Li Zhong-Ming Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu 610065China College of Chemical Engineering Sichuan UniversityChengdu 610065China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

We utilized two structurally different long chains(linear and branched ultra-high molecular weight polyethylene)to reveal the dependence of flow-induced crystallization on long chain architecture,and prepared two bi-disperse systems of 98 wt%short chain and 2 wt%long chain.A flow field was applied to the bi-disperse polyethylene melt by a modified injection-molding machine,known as oscillation shear injection molding(OSIM).For the first time,the structural influence of long chains on flow-induced shish-kebab formation was systematically *** the intermediate layer of OSIM samples,the branched long chains were better than the linear long chains at inducing shish-kebab formation,agreeing with the reported literatures,because the branches can maintain their oriented conformations *** unexpectedly,the reverse is the case for the core layer of OSIM samples,where the shear flow was much weaker than the intermediate *** understand the unexpected phenomenon,the lifetime of shishes induced by different long chains was *** demonstrated that the linear-induced shishes possessed higher thermal stability than the branched-induced ones so that the linear-induced shishes could survive in the core layer of OSIM ***,unlike other methods for flow-induced crystallization,OSIM could create samples for measuring mechanical properties,and thus offer the chance to reveal the relationship between structure and *** mechanical results demonstrated that both long chains remarkably enhanced the mechanical properties because of the significant promoting effect of long chains and intense flow fields on shish-kebab ***,the linear long chains induced more stable and flawless shishes with higher tensile strength and modulus(80.4 and 1613.5 Mpa,respectively)than the branched ones(74.4 and 1489.3 Mpa).Our research not only helps elucidate the mechanism of shish-kebab formation but also provides a better choice to reinforce

关键词： Polyethylene Crystallization Shear-induced Long chain short chain

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Scholz’s First Conjecture: A Brief Demonstration

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Applied Mathematics 2016年第1期7卷 70-76页

作者： José M. Sautto Agustín Santiago Carlos N. Bouza Veró nica Campos Campus Costa Chica Universidad Aut&oacute noma de Guerrero Guerrero M&eacute xico Facultad de Matemá ticas Universidad Aut&oacute noma de Guerrero Acapulco M&eacute xico Facultad de Matemá tica y Computació n Universidad de la Habana Ciudad de La Habana Cuba

This paper presents a brief demonstration of Schulz’s first conjecture, which sets the upper and lower limits on the length of the shortest chain of addition. Two methods of the upper limit are demonstrated;the second one is based on the algorithm of one of the most popular methods for obtaining addition chains of a number, known as the binary method.

关键词： Addition chain Exponentiation short chain Scholz’s Conjecture Binary Method

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