Composites of polylactide containing graphite nanoplates as a filler in the concentration range 1&#x2013;20&#x2009;wt&#x0025; were prepared in methylene chloride using the sonication technique. The thermal characteristics and phase transitions were studied by DSC and TGA methods. The temperatures and heats of glass transition, crystallization, and melting were determined, and the degree of crystallinity during primary and secondary heating was calculated. It is shown that the introduction of graphite nanoplates leads to an increase in the elastic modulus and a decrease in the breaking stress and elongation at break. These changes are especially pronounced at 20&#x0025; GNP content in the composition, when the corresponding mechanical parameters are characteristics of brittle polymer systems. The study of the electrical properties of the composites showed that the percolation threshold in these materials is close to 7&#x2009;wt&#x0025;, which is significantly lower than in the case of spherical particles of comparable density. The SEM study of the filled composites showed a system of pores, which were apparently formed during the evaporation of solvent in the process of their preparation. Diverse structures of PLA/GNP composites films after hot pressure were established by the SEM method.

Svetlana Rogovina

Sergei Lomakin

Sergey Usachev

Miraga Gasymov

Olga Kuznetsova

Natalya Shilkina

Vitalii Shevchenko

Aleksey Shapagin

Eduard Prut

Aleksander Berlin

The Study of Properties and Structure of Polylactide&#x2013;Graphite Nanoplates Compositions

The β-nucleating agent (β-NA), zinc phthalate (ZnPht), was prepared from a mixture of zinc oxide (ZnO) and phthalic anhydride (Pht) during the extrusion of isotactic polypropylene (iPP). To establish the relationship between the crystalline characteristic of ZnO and the crystallization of iPP, single-crystalline ZnO (ZnO(S)) and polycrystalline ZnO (ZnO(P)) were selected and mixed with Pht, respectively, to in situ inducing the β-crystal form of iPP (β-iPP). Compared to ZnO(S)/Pht, ZnO(P)/Pht has the selectivity of β-crystal nucleation during the crystallization of iPP; indeed, the relative content of β-crystal (<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-5.52897pt" id="M1" height="14.8173pt" version="1.1" viewBox="-0.0498162 -9.28833 12.4577 14.8173" width="12.4577pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-108" d="M480 416C480 431 465 448 438 448C388 448 312 383 252 330C217 299 188 273 155 237H153L257 680C262 700 263 712 253 712C240 712 183 684 97 674L92 648L126 647C166 646 172 645 163 606L23 -6L29 -12C51 -5 77 2 107 8C115 62 130 128 142 180C153 193 179 220 204 241C231 170 259 106 288 54C317 0 336 -12 358 -12C381 -12 423 2 477 80L460 100C434 74 408 54 398 54C385 54 374 65 351 107C326 154 282 241 263 299C296 332 351 377 403 377C424 377 436 372 445 368C449 366 456 368 462 375C472 386 480 402 480 416Z"/></g><g transform="matrix(.0091,0,0,-0.0091,6.474,3.132)"><path id="g50-224" d="M563 583C563 664 501 710 433 710C381 710 334 692 285 648C212 582 178 506 149 350L74 -56C49 -190 36 -222 24 -226L30 -257C52 -256 95 -247 121 -229C131 -222 134 -206 165 -21L219 303C254 510 296 665 397 665C447 665 481 626 481 572C481 512 446 457 390 420C367 405 351 400 323 397L302 349C398 338 466 285 466 197C466 117 419 45 306 45C268 45 224 59 198 74L186 50C197 20 228 -14 274 -14C318 -14 359 3 401 26C478 68 554 144 554 225C554 322 493 367 412 396C490 446 563 500 563 583Z"/></g></svg>) improved from 18.0% for ZnO(S)/Pht/iPP to 84.6% for ZnO(P)/Pht/iPP. Moreover, the impact strength of the ZnO(P)/Pht/iPP was nearly 2.0 times greater than pure iPP; for ZnO(S)/Pht/iPP, it was approximately 1.4 times greater than pure iPP. To explain these phenomena, we propose a mechanism that the content of ZnPht generated by ZnO(P)/Pht is more than that of ZnO(S)/Pht during its in situ reaction; evidence from Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and thermogravimetric infrared spectroscope analysis was consistent with this mechanism. This study may provide a new perspective to control the crystal type of polymorphic polymer by adjusting the crystalline characteristic of the nucleating agent.

Shuya Cheng

Kai Zhang

Guomin Xu

Chunyan Shan

Min He

Shuhao Qin

Jie Yu

Crystalline Characteristic Effect of In Situ Interaction between ZnO and Pht on Inducing &#x3b2; Nucleation of Isotactic Polypropylene

The uniform bulk mesomorphic iPP is prepared by rapid compression, and its structural evolution under stretching at different temperatures is studied by combining wide-angle X-ray diffraction and small-angle X-ray scattering. Results show that stretching can induce mesophase to crystallize into &#x3b1;-phase or promote this phase transformation synergistically with temperature, which depends on the selection of stretching temperature. When the temperature is lower than the glass transition temperature of rigid amorphous fraction (RAF), stress could make RAF devitrify firstly and then induce meso-&#x3b1; phase transition during the strain-softening process. As the temperature increases, the high temperature could induce meso-&#x3b1; phase transition to occur before the strain softening, while stretching could promote this transition. When the temperature is higher than a critical value around 100&#xb0;C, the mesophase can be transformed into &#x3b1;-phase completely during stretching. SAXS results show that all the transformed &#x3b1;-crystal exhibits nodular morphology, and they are ductile with greatly enhanced deformability. Based on the results, a reasonable mechanism of meso-&#x3b1; transformation in the stretching process is proposed, explaining the phase transition that goes through several different steps.

Mingkun Xu

Jiaxiang Lin

Xiaolin Zhang

Zhenyin Li

Chuntai Liu

Changyu Shen

Chunguang Shao

Crystallization Behavior of Rapid-Compression-Induced Mesomorphic Isotactic Polypropylene during Uniaxial Stretching at Different Temperatures

Many grades of homopolymer polypropylene (HPP) and impact copolymer PP (ICPP) with a wide range of mechanical properties have been developed for a variety of applications in different industrial sectors. Management of this wide range of materials is a challenge for material suppliers and manufacturers and product developers. This research was to provide insights for managing material supplies through formulating PP with specific mechanical properties using melt compounding of ICPP and HPP. ICPP and HPP were compounded with an internal mixer at different ratios and then the mixtures were injection molded into specimens for characterization. The mechanical behaviors, fracture surfaces, and thermal properties of the mixtures were then characterized. The fracture surface results indicated that the morphologies of the rubber particles in ICPP changed after compounding with HPP, leading to different mechanical and thermal behaviors of the mixtures. Notched and unnotched impact strengths increased linearly with increasing ICPP contents. The crystallization peak temperatures increased linearly with increasing ICPP contents while the degrees of crystallinity of the mixtures decreased linearly. The thermal compounding process and the original material properties mainly determine the final mixture behaviors, and the mixture properties can be predicted based on the weight ratios of the two components.

Yucheng Peng

Shaoyang Liu

Pixiang Wang

Yifen Wang

Xueqi Wang

Formulating Polypropylene with Desired Mechanical Properties through Melt Compounding of Homopolymer and Impact Copolymer

It is well known that the processing conditions in polymer processing have a high impact on the resulting material morphology and consequently the component&#x2019;s mechanical behavior. However, especially for semicrystalline polymers, the tools available for predicting the final morphology of injection molding parts still have significant limitations. In order to investigate the potential of injection molding simulation for the prediction of the morphology, POM homopolymer specimens were injection molded. The crystallization kinetics data were measured, and simulations in 3D and 2.5D with and without crystallization analysis were conducted in Autodesk Moldflow. The simulations are found to be good accordance with the experiments. Predicted spherulite size and crystalline orientation factor reveal a good qualitative correlation with optical micrographs. Also, the evolution of these parameters along the flow path is plausible. The simulation is found to be a powerful tool for morphology prediction in polymeric parts. Its applicability, however, is still limited to 2.5D models in Autodesk Moldflow, which, of course, is insufficient for complex, thick-walled 3-dimensional parts.

Theresia Schrank

Michael Berer

Bernd Haar

Bruno Ramoa

Thomas Lucyshyn

Michael Feuchter

Gerald Pinter

Vito Speranza

Roberto Pantani

Injection Molding Simulation of Polyoxymethylene Using Crystallization Kinetics Data and Comparison with the Experimental Process

We investigated the effect of the chemical structure of alkylammonium salt on the crystallization behavior of poly(vinylidene fluoride) (PVDF) by DSC, optical microscopy, light scattering, and FT-IR. The nonisothermal and isothermal crystallizations of PVDF were accelerated by adding alkylammonium salt consisting of short alkyl chains and small anion species, and the spherulite size and the ordering in the spherulite became smaller due to the nucleation agent effect. The FT-IR spectra revealed that electroactive &#x3b3;-phase was preferentially formed by adding alkylammonium salts though the accelerated crystallization was suppressed due to the steric hindrance effect by the long alkyl chain and large anion species. On the other hand, the formation of the &#x3b3;-phase was suppressed when the dispersion of the salt in the PVDF matrix was poor due to the high melting temperature.

Tatsuaki Miyashita

Hiromu Saito

Nucleation Effect of the Chemical Structure of Alkylammonium Salt on the Crystallization Behavior of Poly(Vinylidene Fluoride)

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Polymer Crystallization - Table of contents 2022

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Polymer Crystallization provides a platform to serve both the scientific and engineering communities, publishing research on all aspects of polymer crystallization.

Polymer Crystallization