Crystalline and supermolecular structures in linear polyethylene irradiated with fast electrons

Gielenz, G.; Jungnickel, B.‐J.

doi:10.1007/bf01452064

Cited by 23 publications

(12 citation statements)

References 23 publications

(22 reference statements)

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“…The preservation of the X-ray crystallinity on irradiating NMWPE with low doses is presented in [15].…”

Section: Resultsmentioning

confidence: 99%

DSC of?-irradiated ultra-high molecular weight polyethylene and high density polyethylene of normal molecular weight

Minkova

1988

Colloid & Polymer Sci

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Abstract:The melting and the crystallization of y-irradiated (doses: 0-6 Mrad) ultra-high molecular weight nascent polyethylene (UHMWPE) and high density nascent polyethylene with normal molecular weight (NMWPE) were investigated by DSC. The heat of melting of the nascent UHMWPE (DSC degree of crystallinity, respectively) increases up to a dose of 3 Mrad, after which it slightly decreases. The heat of the second melting of UHMWPE and of the first and second melting of NMWPE increases slightly up to a dose of 3 Mrad, after which it does not change. The X-ray degree of crystallinity of the nascent non-irradiated and irradiated polymers was 0.62 _+ 0.02. The calorimetric crystallinity was compared to the X-ray one. The results show that radiation does not affect the polymer crystallinity, but influences the thermodynamic heat of melting. The increase of Hm vs. dose in UHMWPE is explained in terms of processes of tie molecule scission within the amorphous regions and on the surface of the crystals, which predominate over crosslinking up to a dose of 3 Mrad. That leads to an increase in the conformational mobility of the molecules and to an increase in the enthalpy, according to Peterlin's formula. The scission of the chains at the points of entangling of the tie molecules leads to a decrease in the temperature and to an increase in the enthalpy of crystallization of UHMWPE vs. dose. In NMWPE these effects are considerably weaker.

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“…The preservation of the X-ray crystallinity on irradiating NMWPE with low doses is presented in [15].…”

Section: Resultsmentioning

confidence: 99%

DSC of?-irradiated ultra-high molecular weight polyethylene and high density polyethylene of normal molecular weight

Minkova

1988

Colloid & Polymer Sci

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“…Indeed, on irradiation of PE in the melt, the segmental mobility was suppressed when the value of Mc in the homogeneous molecular lattice formed dropped to 20 CH2 groups [4].…”

Section: Effect Of Irradiation On Relaxational Transitionsmentioning

confidence: 98%

“…Akad~miai Kiadd, Budapest [4][5][6]. The influence of irradiation not only on crystaUites, but also on relaxations in intercrystalline regions, appears to have been studied by DSC only in [7,8].…”

Section: John Wiley and Sons Limited Chichestermentioning

confidence: 99%

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Differential scanning calorimetry of irradiated polymers

Bershteĭn

Sirota

Egorova

1992

Journal of Thermal Analysis

121

193

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A. E IOFFE PHYSICAL-TECHNICAL INSTITUTE OF THE RUSSIAN ACADEMY OF SCIENCES, ST. PETERSBURG, 194021, RUSSIA DSC was used to study the influence of fast electron irradiation on the molecular mobility and melting of semicrystalline polymers and copolymers of ethylene and of fluorocopolymer. The heat eapacity-temporature dependences obtained in the range from 100 K to 500 K revealed the specific features of the irradiation effect on four relaxational transitions associated with the appearance of segmental motion in different molecular elements of the disordered regions in the polymer. The pronounced dependence of the radiation stability of crystallites on the thermal prehistory of the object under study was found. The results were interpreted on the basis of the decisive role of the molecular mobility and free volume for the predominance of the radiation cross-linking of the molecules. Correlations were established between the characteristics of the thermal transitions and the mechanical properties of the irradiated polymers.

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“…The method has not been generalized for poorly crystalline polymers like branched and cross-linked polyethylene. Recently, considerable attention has been drawn to investigate several aspects of branched and cross-linked polyethylene [11,12,[16][17][18][19]; and in particular, considerable activity has focused on the role of morphology in the formation of ,,water trees" in high voltage transmission cables of cross-linked polyethylene [20][21][22][23][24][25][26][27][28][29]. Some of these morphological investigations on cross-linked polyethylene using a permanganic acid etching technique combined with scanning electron microscopy (SEM), have yielded conflicting results.…”

Section: Introductionmentioning

confidence: 99%

Etching and the morphology of branched and cross-linked polyethylene

Gohil

1986

Colloid & Polymer Sci

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A permanganic acid etching technique was used to characterize the genuine morphologies of bulk crystallized samples of linear, branched, and crosslinked polyethylene. Four different kinds of artifacts as large as 15-20 p~a were detected. It was also noted that artifact density could be drastically reduced by proper selection of etching conditions. The morphologies of artifacts were independent of specimen crystallinity and the orientation of lamellar crystals; however, their rate of production was susceptible to the crystallinity of samples. The formation of a fresh surface involved the preferential etching of edge-on and secondary lamellae. As the growth features of cross-linked polyethylene were less than 6 paxa and were mainly sheaf-like structures, growth features could be readily distinguished from the artifacts by transmission electron microscopy. Another type of artifact (globules morphology) produced at angstrom scale was found to depend on the crystallinity and the surface structure of lamellar crystals. It is demonstrated that the fine lamellar details of branched and cross-linked polyethylene can be observed using transmission electron microscopy. Increasing the number of cross-links in polyethylene, modifies the size and nature of supermolecular structures, the periodic twisting of lamellar crystals, and the nature of the nucleation process. The study of a blend of branched and cross-linked polyethylene showed that the structurally dissimilar molecules co-crystallized at low crystallization temperatures, while there is a tendency for molecular fractionation at higher crystallization temperatures.

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Crystalline and supermolecular structures in linear polyethylene irradiated with fast electrons

Cited by 23 publications

References 23 publications

DSC of?-irradiated ultra-high molecular weight polyethylene and high density polyethylene of normal molecular weight

DSC of?-irradiated ultra-high molecular weight polyethylene and high density polyethylene of normal molecular weight

Differential scanning calorimetry of irradiated polymers

Etching and the morphology of branched and cross-linked polyethylene

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