On the determination of the crystalline fraction of isotactic polypropylene from x‐ray diffraction

Weidinger, A.; Hermans, P. H.

doi:10.1002/macp.1961.020500107

Cited by 244 publications

(66 citation statements)

References 7 publications

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“…The program GRAMS 58 was used to fit the spectra by scaling the intensities of the 2 regions at 10, 16, and ϳ 30°. 54,57 The result, shown in Figure 5, coincides with the position and shape of the amorphous halo obtained from the procedure suggested by Natta et al 54 This procedure was thus adopted in this work to define the amorphous scattering of the poly(propylenes).…”

Section: Resultsmentioning

confidence: 78%

“…54 This procedure has been used among others, by Farrow, 55 Quynn et al, 56 and Weidinger and Hermans. 57 We have first assessed the validity of this procedure before proceeding to the analysis of the WAXS patterns of our samples. To check whether one obtains the correct shape and position of the amorphous scattering by Natta's method, we have measured the diffractogram of an atactic completely amorphous poly(propylene) sample, hydrogenated poly (2-methyl-1,3-pentadiene) at both room temperature and at an elevated temperature.…”

Section: Resultsmentioning

confidence: 99%

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The degree of crystallinity of monoclinic isotactic poly(propylene)

Isasi

Mandelkern

Galante

et al. 1999

J. Polym. Sci. B Polym. Phys.

103

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The degree of crystallinity of a set of monoclinic (alpha) isotactic poly(propylenes), prepared by a metallocene‐type catalyst, were determined at room temperature. Three different methods were used: density, enthalpy of fusion, and wide‐angle X‐ray scattering, and the results compared. The relation between the heat of fusion and the specific volume of these poly(propylenes) was found to be nonlinear, thus precluding any linear extrapolation to obtain the heat of fusion of the pure crystal (ΔHu). The value of ΔHu obtained from depression of the melting temperature by diluents is used. Based on the unit cell density of monoclinic crystals formed from a low defected fraction, the density obtained crystallinity levels were found to be between 0.l5–0.25 higher than those calculated from the heat of fusion. This relatively large difference holds for the isothermally crystallized and quenched isotactic poly(propylenes), and reflects the contribution of the interphase to the density determined crystallinity, which does not contribute to the heat of fusion. Paralleling results found in other systems, the crystallinity levels obtained from wide‐angle X‐ray scattering agree with those obtained from density, indicating a significant contribution of the partially ordered phase to the total diffraction. Emphasis is given on the need to account for the large differences in the crystallinities of poly(propylene) measured by different techniques when evaluating the dependence of properties on this quantity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 323–334, 1999

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Section: Resultsmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 99%

The degree of crystallinity of monoclinic isotactic poly(propylene)

Isasi

Mandelkern

Galante

et al. 1999

J. Polym. Sci. B Polym. Phys.

103

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“…The separation of amorphous scattering from the crystalline peaks was made by the method suggested by Weidinger and Hermans. 6 …”

Section: On-line Measurementmentioning

confidence: 99%

The Effect of Prehistory on Elongational Viscosity and on Crystallization of Running Filament in Melt Spinning

Koyama

Ishizuka

1980

Polym J

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ABSTRACT:Three polypropylene samples (sample A, B, and BIO) having different prehistory were prepared: sample A was prepared by quenching the melt screw extrudated, and samples B and B I 0 were prepared by isothermal crystallization from I% solution and from I 0% solution in xylene, respectively. The effects of prehistory on elongational viscosity and on crystallization were studied by a on-line measuring method in isothermal melt spinning and in melt spinning. The elongational viscosities were in the order sample A> sample BIO > sample B. The difference in the results of online measurement between samples A and B is very evident in 'the second region' along the spinning way which is the region from I 0 em to 35 em below the spinneret. In the last half of the second region, the elongational viscosity for sample B takes on a larger value than that of sample A. The crystallization for sample B begins at a point nearer to the spinneret or at higher temperature than that for sample A in this region, but the progress of crystallinity for sample A was more rapid than that for sample B. These results were compared with the data of quiescent crystallization, and are discussed in this paper in terms of the differences in melt structure and in crystal structure of polymers with different prehistories.KEY WORDS Polypropylene I Prehistory I Elongational Viscosity I Crystallization I Isothermal I Melt Spinning I Melt Structure I Entanglement / In a preceding paper/ the effects of prehistory were studied by measuring melt rheological properties and the physical properties of the spun filaments of two polypropylene samples of different prehistory. The first sample (sample A) was prepared by quenching extrudated melt screw. The second sample (sample B) was prepared by solution crystallizing from a 1% xylene solution. The results of shear viscosity, die swell and spinnability of the melts showed differences according to prehistory: the melt properties were affected by the difference in entanglement between sample A and B. The measurements of thermal shrinkage and tensile testing showed that spun filament A had a larger fraction of tie chain and that spun filament B was rich in the fold-type crystal fraction.spinning. Crystallization behavior was studied for both samples A and B. The relationships between crystallization and melt structure or crysral structure is discussed.In this paper, the effect of prehistory is examined by on-line measurements of the running filaments having different prehistory. The elongational viscosity of a melt having a different prehistory was measured by isothermal melt spinning and by melt EXPERIMENTAL MaterialsThe samples investigated in this paper were similar to those prepared in our earlier paper 1 and are summarized in Table I. The prehistory of the shear deformation was applied to each sample by a screw extruder; the extruded melt was then quenched in ice-water at the exit of the extruder (sample A). One half of an extruded sample was freed from the prehistory of shear deformation by dissolving ...

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“…Dois ensaios foram realizados para obtenção de um valor médio. O cálculo da cristalinidade foi determinado de acordo com o procedimento de Weidinger e Hermans [9] . Realizou-se também ensaios por calorimetria exploratória diferencial (DSC), utilizando …”

Section: Metodologiaunclassified

Efeito de Plastificantes à base de Poliisobutenos nas Propriedades Físicas e Mecânicas do Polipropilen

Nascimento¹,

Timóteo²,

Rabello³

2013

Polímeros

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IntroduçãoO polipropileno (PP) é um dos polímeros termoplásticos mais utilizados pela indústria, com uma diversidade de aplicações que incluem embalagens rígidas e flexíveis, descartáveis, tubos e produtos injetados para os mais variados usos. A indústria petroquímica disponibiliza vários tipos de polipropilenos, quais sejam: PP homopolímero, PP copolímero heterofásico e PP copolímero randômico. O PP homopolímero contém apenas o monômero propeno em sua cadeia molecular e, sendo predominantemente de configuração isotática, pode atingir um grau de cristalinidade de até 60%.Como consequência da presença do grupo lateral metil, o PP possui maior temperatura de transição vítrea (T g ) e maior rigidez quando comparado ao polietileno, mas exibe baixa resistência ao impacto em baixas temperaturas. Com isso, sua microestrutura torna-se mais susceptível à propagação de falhas. A síntese do PP copolímero, normalmente utilizando o etileno como comonômero, é uma solução conhecida para aumentar a tenacidade do PP em baixas temperaturas, uma vez que ocorre uma redução tanto da temperatura de transição vítrea como do grau de cristalinidade [1] . A produção de copolímeros, por se tratar de uma solução que envolve alteração no processo de polimerização, apresenta duas consequências negativas do ponto de vista industrial: (i) maior custo, uma vez que não se tem o ganho em escala que ocorre com o PP homopolímero; (ii) menor versatilidade, ou seja, alterações nas propriedades requerem alterações na processo de síntese, com todos as dificuldades operacionais decorrentes. Assim, o emprego de PP copolímero, para aplicação em produtos de menor valor agregado, torna-se frequentemente inviável.Um procedimento pouco estudado para alcançar boa resistência ao impacto seria a adição de plastificantes ao PP homopolímero. Os plastificantes são largamente utilizados, principalmente no PVC, alcançando-se uma grande variedade de propriedades e aplicações [2,3] . Uma restrição a essa abordagem é que são poucos os polimeros comerciais para os quais existem plastificantes adequados para a utilização industrial. No caso do polipropileno a semelhança química indica que os poliisobutenos poderiam ser plastificantes compatíveis. Os poliisobutenos (PIB´s) são copolímeros de baixa massa molar, predominantemente formados por isobutileno e baixo teor de buteno e são utilizados como plastificantes para alguns tipos de polímeros, como polietileno de baixa densidade para aplicação como filme esticável (stretch film) [4,5] , promovendo uma maior flexibilidade e elasticidade.Os trabalhos pioneiros sobre o uso de poliisobutenos como plastificantes para o PP foram os desenvolvidos independentemente por Sanders [4] e Khungar [5] . Eles investigaram o efeito plastificante dos polibutenos nas propriedades mecânicas de filmes de PP, tendo observado uma redução no módulo elástico e aumento no índice de fluidez, fatores que indicam uma ação plastificante. Entretanto, os autores citados não exploraram a influência deste aditivo nas propriedades térmicas, cristalinidade e ...

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On the determination of the crystalline fraction of isotactic polypropylene from x‐ray diffraction

Cited by 244 publications

References 7 publications

The degree of crystallinity of monoclinic isotactic poly(propylene)

The degree of crystallinity of monoclinic isotactic poly(propylene)

The Effect of Prehistory on Elongational Viscosity and on Crystallization of Running Filament in Melt Spinning

Efeito de Plastificantes à base de Poliisobutenos nas Propriedades Físicas e Mecânicas do Polipropilen

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