High‐density polyethylene pipe resins

Böhm, Ludwig; Enderle, H.-F.; Fleifßner, Manfred

doi:10.1002/adma.19920040317

Cited by 87 publications

(62 citation statements)

References 21 publications

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“…2,3 The present research into the fracture mechanics of SCG has shown that the process has two phases. 9,10 Ludwig et al 11 found that a new bimodal PE-HD material with a broad bimodal molecular-weight distribution and a favorable short-chain branch distribution has superior mechanical properties and ESCR. A material with a large amount of voids and a brillar structure is formed in this phase.…”

Section: Introductionmentioning

confidence: 99%

Effect of different morphologies on slow crack growth of high-density polyethylene

et al. 2015

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With the wide application of polymer pipes in the world, people pay more attention to the longevity of the pipes. Slow crack growth is one of the most important factors that influence the longevity of materials, especially PE pipes. Thus, the study of slow crack growth has become deep and concrete. In this paper, slow crack growth in specimens with different morphologies was studied. A self-designed oscillatory shear injection molding (OSIM) device was utilized to prepare pure HDPE 5000s specimens with different morphologies. The process of slow crack growth in OSIM specimens was compared with that in specimens prepared by conventional injection molding (CIM); so it was possible to study the influence of the different morphologies in specimens on the process of slow crack growth under the same external conditions. Different morphologies have great influences on the ability of materials to resist slow crack growth. The time taken for the slow crack growth to fracture in the OSIM specimens is considerably longer than that in the conventional ones. Under the same conditions of 80 C and 9.0 MPa, the time of complete fracture is 650 min in OSIM specimens, in contrast to 60 min in conventional specimens. Moreover, in the OSIM specimens, the initial stress of the brittle-ductile transition is increased. At 80 C, the brittle-ductile transition takes place at 4.7 MPa for conventional specimens, whereas for OSIM specimens, it occurs at 5.6 MPa. Furthermore, the mechanisms of their slow crack growth processes are different. The SCG process in conventional specimens is that stress concentration initiates craze, which grows rapidly and becomes a crack. However, the process in OSIM specimens is a cyclic process, in which stress concentration initiates craze, the crack grows, a new craze appears, and the new crack grows until the specimens fracture.

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Section: Introductionmentioning

confidence: 99%

Effect of different morphologies on slow crack growth of high-density polyethylene

et al. 2015

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“…The internal defects of the material cause localized plastic yielding that eventually result in the initiation of craze. As the strain increases, the craze extends to form numerous highly oriented microfibrils, which help to reduce the stress concentration in the crack‐tip region . Over a longer time, the highly oriented load‐bearing tie chain networks of microfibrils within the craze start to relax and untangle from each other until the number of remaining linkages becomes extremely small.…”

Section: Resultsmentioning

confidence: 99%

“…One is stiffness (high modulus) and the other is an excellent long‐term performance. Adjusting the content of the pure tie chain and the entangled tie‐molecule density can achieve excellent slow stress crack resistance (SCGR), which is beneficial to the long‐term performance of the pipe . The stiffness of polyethylene materials can be improved by higher crystallinity and thicker lamellae.…”

Section: Introductionmentioning

confidence: 99%

Influence of comonomer distribution on crystallization kinetics and performance of polyethylene of raised temperature resistance

Zhang

Bing

Ding

et al. 2019

Polymer International

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Three polyethylene of raised temperature resistance (PE‐RT) materials have been used to explore the factors that cause the differences in crystallization kinetics and mechanical performance between different classes and between the same classes. 1‐PE‐RT and 3‐PE‐RT belong to the same class (type II) but with different comonomer, while 2‐PE‐RT (type I) and 3‐PE‐RT use the same comonomer. The results of tensile and bending tests and isothermal crystallization indicate that different classes or even the same classes of PE‐RT have differences in high‐temperature resistance and long‐term performance. Characterization of the molecular chain structure shows that the comonomer content within the high molecular weight chains is significantly higher than that within the low molecular weight chains, and the comonomer is not uniformly distributed over the short‐chain molecules, which makes 1‐PE‐RT have higher modulus and better long‐term performance. Because the difference of comonomer content in long‐chain molecules and short‐chain molecules is small and the comonomer is relatively uniformly distributed over the short‐chain molecules, 3‐PE‐RT cannot balance the stiffness and the long‐term performance very well. For 2‐PE‐RT, the comonomer content in the long‐chain molecules and the short‐chain molecules is approximately the same and there is no intramolecular comonomer distribution, and thus it has the best long‐term performance but the lowest modulus. 2‐PE‐RT cannot have rigidity and good long‐term performance at the same time. © 2019 Society of Chemical Industry

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“…Reactor blends comprising a small fraction of very high molecular weight polyethylenes (molecular weight larger than 500 000 g/mol) containing a small amount of comonomer, in conjunction with lower molecular weight polyethylenes affords polyethylene reactor blends exhibiting improved mechanical property, toughness and extraordinary fatigue life. [159] This significant improvement is assigned to the bonding of polyethylene crystallites by means of the high molecular weight tie molecules. A typical example of such reactor blends with multimodal molecular weight distribution is displayed in Figure 26.…”

Section: Reactor Blendsmentioning

confidence: 99%

Catalytic Polymerization and Post Polymerization Catalysis Fifty Years After the Discovery of Ziegler's Catalysts

Mülhaupt

2003

Macro Chemistry & Physics

275

193

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During the 1950's the discoveries of Ziegler's organometallic catalyst systems and Natta's stereoselective olefin polymerization set the stage for extraordinary progress in polymer science and technology. Today advanced catalyst systems are available for catalytic carbon carbon bond formation by means of polyinsertion, metathesis, coupling reactions, and controlled radical polymerization. Modern catalytic olefin polymerization processes and polyolefins are environmentally friendly and meet the demands of a sustainable development. The architectures of homo‐ and copolymers based upon olefin, cycloolefin, diene, styrene and arene feed stocks are tailored as a function of single site catalysts' ligand frameworks. Polymer properties are varied over a very wide range, e.g., liquid/solid, rigid/soft, crystalline/amorphous/rubbery, permeable/impermeable, opaque/transparent, moldable/thermosetting, insulating/conducting. Advanced polymerization reaction engineering, copolymerization processes, reactor granule and reactor blend technologies, tailor‐made single site catalysts, catalyst blends and tandem catalysis improve property profiles, stability, morphology, and melt processing. Tuned cycloolefin polymers are new functional materials for electronic applications. Catalytic chain transfer (CCT) and atom transfer polymerization (ATRP) produce a variety of new functional polymers, reactive oligomers, and block copolymers. Aqueous polyolefin emulsions are obtained when catalytic olefin polymerization is performed in nanodroplets of catalyst miniemulsions. The scope of catalytic polymerization and post polymerization catalysis is progressing well beyond the frontiers of commodity polyolefin manufacturing. Advanced catalytic processes produce polar polymers such as polyethers, polyketones, polyesters, polycarbonates, polyamides, polyaramids, and polyimides. The new phosgene free polycarbonate syntheses are based upon the palladium catalyzed oxidative carbonylation. This overview highlights history, recent progress and modern trends in catalytic polymerization and catalytic polymer modification illustrated by selected examples.

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High‐density polyethylene pipe resins

Abstract: A d ) Mut(v 4 (1992) No 3 C i ) VCH V e r l u g~g~s e l l~~h u f t mhH, W-6940 W(wherm, 1992 0935-9648/92/0303-0235 $ 3 SO+ 2SjO

Cited by 87 publications

References 21 publications

Effect of different morphologies on slow crack growth of high-density polyethylene

Effect of different morphologies on slow crack growth of high-density polyethylene

Influence of comonomer distribution on crystallization kinetics and performance of polyethylene of raised temperature resistance

Catalytic Polymerization and Post Polymerization Catalysis Fifty Years After the Discovery of Ziegler's Catalysts

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