Effect of fusion conditions ofβ-polypropylene on the new crystallization

Varga, J.; Schulek-Tóth, F.; Ille, Attila

doi:10.1007/bf00657402

Cited by 43 publications

(23 citation statements)

References 17 publications

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“…(4): where T cNA , T c1 , and T c2 are the peak temperatures of the nucleated non‐nucleated and self‐seeded samples, respectively. Unfortunately, this equation cannot be adopted for β‐iPP, because the β‐nucleated samples heated slightly above the melting point of the β‐phase T m (β) recrystallize always in the α‐modification 47. Therefore, the determination of T c2 is impossible.…”

Section: Methodsmentioning

confidence: 99%

Crystallization of isotactic polypropylene in the presence of a β‐nucleating agent based on a trisamide of trimesic acid

Varga

Stoll

Menyhárd

et al. 2011

J of Applied Polymer Sci

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Tris-2,3-dimethyl-hexylamide of trimesic acid (TATA) is an new type of b-nucleating agent for isotactic polypropylene (iPP). The crystallization, melting characteristics, and the supermolecular structure of iPP nucleated with TATA were studied on the samples crystallized under nonisothermal and isothermal conditions. The b-nucleating ability of TATA was rather high even at low concentration. It was established that TATA possessed dual nucleating ability generating samples with mixed (a and b) polymorphic compositions. The b-content showed an maximum value at low concentrations (10-100 ppm) of TATA. The b-content decreased with increasing concentration of TATA in the higher concentration range. The highest b-content (about 80%) was achieved at the crystallization temperature T c ¼ 110-120 C at low concentration of TATA. The crystallization curves registered at constant cooling rate or under isothermal condition have a single peak in spite of the formation of two polymorphic modifications. The crystallization isotherms cannot be linearized according to the Avrami equation because of simultaneous crystallization of the a-and b-forms, having different nucleation and growth rate. It was also found that the b-content increased with increasing conversion during isothermal crystallization because of the higher growth rate of the b-phase. The b-phase formed in the presence of TATA consist of lamellar crystallites. In the early stage of the crystallization, hedritic structure is formed.

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Section: Methodsmentioning

confidence: 99%

Crystallization of isotactic polypropylene in the presence of a β‐nucleating agent based on a trisamide of trimesic acid

Varga

Stoll

Menyhárd

et al. 2011

J of Applied Polymer Sci

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“…Specifically, small and less perfect crystals melt at lower temperature relative to the larger and more perfect ones. Multiple peaks may be also attributed to the existence of different crystal modifications, or to melting/recrystallization processes occurring during the DSC scan 26,27 . The degree of crystallinity calculated according to Equation 1 was 49.8% and 47.0% for PHB-1 and PHB-2, respectively.…”

Section: Differential Scanning Calorimetry (Dsc) Measurementsmentioning

confidence: 99%

Environmental Stress Cracking of Poly(3-hydroxibutyrate) Under Contact with Sodium Hydroxide

et al. 2015

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Environmental stress cracking (ESC) is one of the most important causes of polymer premature failure, occurring when a combination of mechanical load and an aggressive fluid is applied. The phenomenon is well know by polymer producers and product designers but its mechanisms are not very well understood. Although the ESC effects of many commercial polymers are well known, this type of failure in biopolymers were not studied yet. In the current work, the stress cracking behaviour of poly(3-hydroxybutyrate) (PHB) with 4,0 and 6,2% of hydroxyvalerate (HV) was investigated in injection-moulded bars under contact with sodium hydroxide (NaOH) solutions. The experiments were conducted using two different types of stress arrangements: (i) an ordinary tensile testing and (ii) a relaxation experiment. In both situations the injection-moulded bars were exposed to the NaOH solution and some testing conditions where varied, like the cross-head speed of the tensile test and the maximum load of the relaxation arrangement. The results showed that NaOH acted as a strong stress cracking agent for PHB, causing surface cracking and reducing significantly the mechanical properties. Catastrophic failure with an extensive surface damage was also observed by photographed and scanning electron microscopy (SEM) images. The magnitude of the effects increased with decreasing crosshead speed and increasing loading level.

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“…Although every molecular chain in PP ␣ modification has a 3 1 helical symmetry, the bulk crystalline structure does not present triple symmetry, which is necessary for ␣ modification. ␤ modification, different in its physical and mechanical properties from ␣ modification to some degree, is obtained at about 130°C, the most favorable temperature for ␤ growth, [5][6][7][8] and a high content of ␤ crystals can be acquired under special conditions, such as the quenching of the melt within a certain temperature range, 9,10 directional crystallization in a temperature gradient field, 11 shear-induced crystallization, 12 or dop-ing of the resin with certain heterogeneous nucleating agents. [13][14][15] Previous publications have commonly reported that ␤ modification is less stable than ␣ modification, tending to transform into ␣ modification when heated within a certain temperature range 16 or stretched.…”

Section: Introductionmentioning

confidence: 99%

Stress‐induced crystallization of biaxially oriented polypropylene

Yang

Xie

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:The hot stretching of thick, extruded sheets at high temperatures is a very important process in the production of finished biaxially oriented polypropylene (BOPP) films with special inner structures. Through a simulation of hot stretching in the machine direction (MD) of the processing of BOPP films, it was found that at high temperatures, the stretching ratio greatly influenced the obtained crystalline structure, as observed by differential scanning calorimetry (DSC). Also, in MD hot stretching, the crystallinity increased by an average of 20%. Wide-angle X-ray diffraction patterns of extruded sheet samples with and without stretching confirmed the structural changes shown by DSC, and the results proved that ␤-crystal modification did not occur during the MD hot-stretching process.

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Effect of fusion conditions ofβ-polypropylene on the new crystallization

Cited by 43 publications

References 17 publications

Crystallization of isotactic polypropylene in the presence of a β‐nucleating agent based on a trisamide of trimesic acid

Crystallization of isotactic polypropylene in the presence of a β‐nucleating agent based on a trisamide of trimesic acid

Environmental Stress Cracking of Poly(3-hydroxibutyrate) Under Contact with Sodium Hydroxide

Stress‐induced crystallization of biaxially oriented polypropylene

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