Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. I. Structure–property relationships

Fujiyama, Mitsuyoshi; Wakino, Tetsuo

doi:10.1002/app.1991.070421012

Cited by 94 publications

(74 citation statements)

References 10 publications

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“…However, from the pole densities it is possible to observe that the c-axis orientation of the lamellae is higher in the flow direction than in the a*-axis orientation. This specific bimodal crystalline orientation has been discussed in the literature 31,32,44 . Mendoza and coworkers 24 described that the two components (a*-axis component and c-axis component) have a large orientation distribution, the a*-axis lamellae could nucleate locally on the c-axis lamellae which have the same crystallographic b-axis.…”

Section: Molecular Orientation By Pole Figuresmentioning

confidence: 57%

“…This molecular orientation gradient is responsible for the improved properties in the orientation direction; on the other hand, the properties along the perpendicular direction usually are worse [22][23][24][25] . The parameters that affect the molecular orientation are: shear and elongation tensions imposed to the molten polymer during their solidification, processing conditions (injection and mold temperatures, packing pressure and flow rate, among others) and intrinsic characteristics of the polymer (relaxation time, crystallization kinetics and chains rigidity, for example [22][23][24][25][26][27][28][29][30][31][32][33] ). However, the complete knowledge of the correlation between molecular orientation and processing parameters of injection molded samples is still subject of research.…”

Section: Introductionmentioning

confidence: 99%

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A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

2009

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The development of α and β-phases and the molecular orientation of injection molded disks of two isotactic polypropylene (i-PP) resins were studied by wide angle X-ray diffraction (WAXD) and pole figures. A nucleated (NPP) and non-nucleated (HPP) polymers were analyzed. The main proposal of this article was the comprehensive study of the interrelations between the processing conditions, phase contents and PP α-phase molecular orientation of injection molded PP resins. In both resins, it was observed that the α-phase was present in all regions along the thickness while the β-phase was present mainly in the external layers, decreasing from the surface to the core; however this last phase was present in a very small amount in the NPP resin. For both polymers, the orientation of the macromolecules c-axis was higher along the flow direction (RD) than along the transverse direction (TD). The b-axis of the PP α-phase molecules was oriented to the thickness direction (ND). The orientation of the c-axis along RD and b-axis along ND of the NPP samples was considerably higher than of the HPP samples, due to the NPP faster crystallization kinetics. For both polymers, the most influential processing parameters on the molecular orientation were the mold temperature and flow rate. The results indicate that, as the mold temperature increased, the characteristic molecular orientation of PP α-phase, with c-axis along RD and b-axis along ND, decreased. With increase in the flow rate an increase of the c-axis molecular orientation of the samples along RD was observed.

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Section: Molecular Orientation By Pole Figuresmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

2009

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“…If the ratio is greater than 1.5, then the a axis is parallel to the surface. [22][23][24][25] The results derived from DSC data and I(110)/I(040) values of the matrices are given on following Table 2. Endothermic melting point peaks in heating curves and crystallization peaks in cooling curves were clearly observed in Figure 5 Melting points of the matrices are also close and changes between 160 to 162 o C. There is not much change in melting and crystallization temperatures by DLP addition and they are similar to the results gathered in our previous study.…”

Section: Resultsmentioning

confidence: 99%

Influence of Dilauroyl Peroxide on Mechanical and Thermal Properties of Different Polypropylene Matrices

Şirin¹,

Yavuz²,

Çanlı³

2015

Polymer Korea

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In this study, the influence of dilauroyl peroxide on mechanical and thermal properties of different polypropylene (PP) matrices was investigated. Polypropylene matrices, different molecular weight isotactic PP containing 0.01, 0.02, 0.04, 0.06, 0.08, and 0.1 wt% of dilauroyl peroxide (DLP) were prepared by using a single-screw extruder. The effect of the visbreaking agent (DLP) on mechanical, physical, thermal and morphological properties of different molecular weight PP had been studied. Mechanical properties (tensile strength at break point, at yield and elongation at break point), melt flow index (MFI), scanning electron microscope (SEM) and differential scanning calorimetric (DSC) analyses of these matrices were examined. Melting (T m ) and crystallization (T c ) temperatures, crystallinity ratio (%) and enthalpies were determined. The microstructure of isotactic polypropylene matrix was investigated by scanning electron microscopy (SEM). From SEM analysis, it was observed that the surface disorder increased by the increasing amount of DLP. As a result of DSC analyses, the crystallinity ratio of the PP matrices has varied between 1.64-7.27%. Mechanical properties of the matrices have been improved. Particularly, the mechanical tests of PP have given interesting results when compounded with 0.06-0.08 wt% dilauroyl peroxide (DLP). Mechanical properties and thermal decomposition processes were all changed by increasing the amount of DLP in the matrix structure.

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“…The most important effect of particulate fillers is their ability to act as nucleating agents. The very strong nucleating effect of talc in PP was proved many times [64,65]. Similarly to talc, layered silicates, and especially montmorillonite (MMT), were shown to nucleate polypropylene quite strongly [66][67][68][69][70].…”

Section: Crystalline Matrices Nucleationmentioning

confidence: 99%

Particulate Fillers in Thermoplastics

Móczó

Pukánszky

2017

Fillers for Polymer Applications

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The characteristics of particulate filled thermoplastics are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape, while the main matrix property is stiffness. Segregation, aggregation and the orientation of anisotropic particles determine structure. Interfacial interactions lead to the formation of a stiff interphase considerably influencing properties. Interactions are changed by surface modification, which must be always system specific and selected according to its 2 goal. Under the effect of external load inhomogeneous stress distribution develops around heterogeneities, which initiate local micromechanical deformation processes determining the macroscopic properties of the composites. INTRODUCTUIONParticulate filled polymers are used in very large quantities in all kinds of applications. The total consumption of fillers in Europe alone is currently estimated as 4.8 million tons (Table 1) [6]. In spite of the overwhelming interest in nanocomposites, biomaterials and natural fiber reinforced composites, considerable research and development is done on particulate filled polymers even today. The reason for the continuing interest in traditional composites lays, among others, in the changed role of particulate fillers. In the early days fillers were added to the polymer to decrease price.However, the ever increasing technical and aesthetical requirements as well as soaring material and compounding costs require the utilization of all possible advantages of fillers.Fillers increase stiffness and heat deflection temperature, decrease shrinkage and improve the appearance of the composites [9][10][11][12][13]. Productivity can be also increased in most thermoplastic processing technologies due to their decreased specific heat and increased heat conductivity [9,10,[14][15][16][17]. Fillers are very often introduced into the polymer to create new functional properties not possessed by the matrix polymer at all like flame retardancy or conductivity [18][19][20][21]. Another reason for the considerable research activity is that new fillers and reinforcements emerge continuously among others layered silicates [7,[22][23][24][25][26][27][28][29], wood flour [30][31][32][33][34][35][36][37], sepiolite [38][39][40][41][42][43][44][45][46][47][48][49], etc.The properties of all heterogeneous polymer systems are determined by the same four factors: component properties, composition, structure and interfacial interactions [9,50]. Although certain fillers and reinforcements including layered silicates, other nanofillers, or natural fibers possess special characteristics, the effect of these four factors is universal and valid for all particulate filled materials. As a consequence, in this paper 3 we focus our attention on them and discuss the most important theoretical and practical aspects of composite preparation and use accordingly. The general rules of h...

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Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. I. Structure–property relationships

Cited by 94 publications

References 10 publications

A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

Influence of Dilauroyl Peroxide on Mechanical and Thermal Properties of Different Polypropylene Matrices

Particulate Fillers in Thermoplastics

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