Zur Morphologie von peroxidisch vernetztem Polyethylen

Abstract

ZUSAMMENFASSUNG:Das Vernetzen von LDPE mittels Peroxiden hat neben einer Abnahme der Kristallinitat eine Veranderung der iibermolekularen Struktur zur Folge. Mit steigender Vernetzung nimmt der Durchmesser der Spharolithe bzw. der garbenfdrmigen Oberstrukturen ab. Dieses Ergebnis ist auf eine rucklaufige Kristallwachstumsgeschwindigkeit zuruckzufuhren, bedingt durch eine fallende Kristallisationstemperatur und einen Anstieg der Schmelzviskositat infolge zunehmender Vernetzungsdichte. Durch die Vernetzung entstehen zusatzliche konstitutionelle Stdrungen in der PE-Kettenstruktur, wodurch die Abmessungen der Lamellenkristalle und die Grdfie der Mosaikbldcke beeinflufit werden. SUMMARY:The crosslinking of LDPE with peroxides results in both reduction of crystallinity and change of the supermolecular structure. The diameter of the spherulites and the sheaf-shaped superstructures decrease with increasing network. This result can be referred to a decreased crystal growth rate due to an increase of the melt viscosity owing to an increasing network density and a decreasing crystallization temperature. Additional constitutional disorder in the PE chain structure arises through crosslinking; this influences the size of the lamellar crystals and the ideally imperfect crystal block.

Effect of the ultradrawing behavior of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends on their physical properties

“…To improve the anticreeping properties of common PE, the thermal stability of PE must be improved first. The applied method is the chemical crosslink method, which includes the radiation crosslink method24, 25 and the peroxide crosslink method 26, 27. The radiation method not only can produce the chemical crosslinks of polymer chains but also can break the polymer chains into shorter molecular chains to lower the tensile strength and modulus 24, 25.…”

“…This crosslink method is mainly applied before PE molecular orientation. However, when it is applied after PE molecular orientation and crystallization, oxidation crosslinking26, 27 is not easy to perform. Soo and Sik28 dissolved dicumyl peroxide in decalin, coated it onto a UHMWPE gel, and applied zone‐drawing technology to the prepared UHMWPE gel film to obtain an ultrahigh orientation.…”

Effect of zone drawing accompanied with crosslinking on the structure and properties of ultrahigh molecular weight polyethylene gel film

“…That is, this method makes up for the weak points of insufficient crosslinking after drawing, lowered draw ratio after crosslinking, and excessive chain scission due to longer crosslinking reaction time generated in the hot drawing and crosslinking methods reported previously. 15,16 Also, the morphology and thermal properties of crosslinked-undrawn and zone- Zone Drawing of Gel Film length was drawn under tensions controlled by different dead weights, respectively, on an Instron Zone drawing was carried out at 127ЊC by moving model 4201 (Fig. 2).…”

“…,16 Radiation method caused not only crosslinking but chain Introduction of Crosslinking Agent scission in polymer backbone to decrease tensile in UHMW PE Gel strength and tensile modulus. Crosslinking by peroxide was achieved by introducing a crosslink-UHMW PE gel cooled in the air to have volume ing agent in PE on drawing in the hot atmosphere.…”