Influence of thermal runaway in styrene–acrylonitrile bulk copolymerization revealed by computational fluid dynamics modeling

The computational fluid dynamics (CFD) and kinetic-based moment methods coupled approach is adopted to simulate the bulk copolymerization of styrene–acrylonitrile (SAN) in a stirred tank reactor. Numerical simulations are carried out to investigate the impacts of impeller speed, monomer ratio, initiator ratio, and initial reaction temperature on the copolymerization process and product properties. Particularly, the Chaos theory is selected as a criterion for evaluating the occurrence of the thermal runaway. The Flory's and Stockmayer's distributions are employed to calculate chain length distribution and copolymer composition distribution of copolymer. The simulation results highlight that the appearance of thermal runaway can be postponed by properly increasing the rotation speed, decreasing the initiator loadings, initial acrylonitrile contents and initial reactor temperature. Furthermore, significant differences exist in the product properties that predicted by the ideal and non-ideal models, which demonstrates that the temperature heterogeneity plays a crucial role in SAN copolymerization. This study could offer references for the safe operation and design of polymerization processes.     

Combination of nuclear magnetic resonance spectroscopy and nonlinear methods to analyze the copolymerization of phosphonic acid derivatives

We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The ¹H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of r_HEMA = 1.83; r_ECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256.     

Synthesis and Characterization Superabsorbent Polymers Made of Starch,Acrylic Acid,Acrylamide, Poly(Vinyl Alcohol), 2-Hydroxyethyl Methacrylate, 2-Acrylamido-2-methylpropane Sulfonic Acid

Three polymers with excellent absorption properties were synthesized by graft polymerization: soluble starch-g-poly(acrylic acid-co-2-hydroxyethyl methacrylate), poly(vinyl alcohol)/potato starch-g-poly(acrylic acid-co-acrylamide), poly(vinyl alcohol)/potato starch-g-poly(acrylic acid-co-acrylamide-co-2-acrylamido-2-methylpropane sulfonic acid). Ammonium persulfate and potassium persulfate were used as initiators, while N,N′-methylenebisacrylamide was used as the crosslinking agent. The molecular structure of potato and soluble starch grafted by synthetic polymers was characterized by means of Fourier Transform Infrared Spectroscopy (FTIR). The morphology of the resulting materials was studied using a scanning electron microscope (SEM). Thermal stability was tested by thermogravimetric measurements. The absorption properties of the obtained biopolymers were tested in deionized water, sodium chroma solutions of various concentrations and in buffer solutions of various pH.     

偶联剂对PLA/PBAT/WF复合材料3D打印性能的影响

以聚乳酸（PLA）和聚己二酸/对苯二甲酸丁二酯（PBAT）为基体，杨木粉（WF）为填充增强材料，使用混炼机熔融共混制备PLA/PBAT/WF复合材料，采用熔融沉积成型（FDM）技术制备标准实验试样，通过扫描电子显微镜、红外光谱分析、旋转流变测试以及力学试验等方法，研究不同含量的硅烷偶联剂KH550对PLA/PBAT共混物以及PLA/PBAT/WF的相容性、流变性及力学性能的影响。结果表明，在偶联剂用量为3 %（质量分数，下同）时，拉伸强度提高了136 %；偶联剂KH550与 PLA和PBAT共价键偶联生成接枝聚合物，二者相容性得到提高；同时偶联剂与WF表面羟基发生缩聚反应有效的改善了其与PLA/PBAT的基体相容性，PLA/PBAT/WF复合材料的FDM的制件力学性能得到较大提升；复合材料的黏度随偶联剂含量的增加呈下降的趋势，含量为3 %时线材的综合打印性能及制品质量最佳。     

Metal complexation studies of amylopectin‐graft‐poly[(N,N‐dimethylacrylamide)‐co‐(acrylic acid)]: a biodegradable synthetic graft copolymer

Synthesis of amylopectin‐graft‐poly[(N,N‐dimethylacrylamide)‐co‐(acrylic acid)] was carried out using solution polymerization technique with potassium persulfate as the initiator. The graft copolymer was characterized by measuring molecular weight using size exclusion chromatography, thermal analysis and Fourier transform infrared (FTIR) spectroscopy. The synthetic graft copolymer was used for the removal of some potentially toxic metal ions, Cu(II), Zn(II) and Ni(II), from their aqueous solutions. Various operating parameters like the amount of adsorbent, solution pH, contact time and temperature were studied. The adsorption data were well described by the pseudo‐second‐order and Langmuir isotherm models. Metal complexation studies were carried out experimentally using cyclic voltammetry and UV‐visible and FTIR spectroscopies. The metal complex structure was also studied theoretically using density functional theory with the Gaussian 09 program and the geometry of the complex structure was optimized. The metal complexation ability of the graft polymer was in the order Cu(II) > Ni(II) > Zn(II). Calculation of the various thermodynamic parameters was also done. The negative value of free energy change indicates the spontaneous nature of the adsorption. © 2015 Society of Chemical Industry     

Polydimethylsiloxane macromonomer bearing N‐vinylcaprolactam as end group: thermosensitive graft copolymers via free radical polymerization

A polydimethylsiloxane macromonomer was synthesized via anionic ring‐opening polymerization of hexamethylcyclotrisiloxane using N‐vinylcaprolactam anion as initiator and trimethylsilyl chloride as terminating agent. The polydimethylsiloxane macromonomer was copolymerized with N‐vinylcaprolactam in different molar ratios via a free radical mechanism. The new class of graft copolymers thus obtained shows cloud points in water because of an excess of N‐vinylcaprolactam units in the polymer chain. These cloud points can be shifted using randomly methylated β‐cyclodextrin as complexing agent. © 2015 Society of Chemical Industry     

Synthesis,characterization, rheological and thermal behavior of metallocene ethylene − norbornene copolymers with low norbornene content using pentafluorophenol modified methylaluminoxane

Ethylene ? norbornene copolymers were synthesized using rac‐ethylene bis(indenyl) zirconium dichloride/pentafluorophenol modified methylaluminoxane. First, the effect of using a modifier in combination with a low ratio of Al/Zr on the catalyst activity and co‐monomer incorporation was studied. The results of copolymerization reveal a 20% co‐monomer incorporation improvement and a rise of activity by 2‐fold in the presence of the modifier. Rheological measurements show a higher molecular weight in copolymers synthesized using modified methylaluminoxane. The alternative and dyad block microstructures of copolymers become possible in the case of a norbornene content of more than 14 mol%. Second, the effect of co‐monomer content on the rheological and thermal behavior of the synthesized copolymers was investigated. The results of the rheological study indicate a lower molecular weight in samples containing a higher norbornene content. Dynamic mechanical thermal analysis confirms the influence of different microstructures on the glass transition temperature. The crystal structure of copolymers having a higher molecular weight is emphasized using wide angle X‐ray scattering and DSC even with a greater incorporation of norbornene. © 2015 Society of Chemical Industry     

The improvement of electro‐optical properties of polymer‐dispersed liquid crystals with graft copolymer matrix synthesized by reversible addition–fragmentation chain transfer and atom transfer radical polymerization

Aiming to decrease the memory effect of polymer‐dispersed liquid crystals (PDLCs), a type of graft macroinitiator, synthesized by reversible addition–fragmentation chain transfer and atom transfer radical polymerization, was employed to prepare PDLCs with graft copolymer matrix in our previous work. Compared with linear copolymer matrix PDLCs prepared using a linear macroinitiator, it was found that, although low‐memory‐effect PDLCs were obtained, the driving voltage and transmittance of the PDLCs were unfortunately sacrificed to some extent. Thus, it is necessary to improve the electro‐optical properties of PDLCs on the basis of the original research performed by us. In the work reported in this article, a kind of linear macroinitiator with high refractive index and another graft macroinitiator with flexible branched chains were employed to prepare PDLCs. The results showed that by using mixed macroinitiators, the electro‐optical properties of PDLCs could be improved, and a possible mechanism is proposed.     

四氢呋喃对M-1催化剂性能的影响

结合乙烯气相流化床反应工艺的特点,深入探讨分析四氢呋喃对M-1催化剂的作用和影响,结果表明,四氢呋喃的含量直接影响M-1催化剂的活性和催化乙烯与丁烯-1共聚生产的树脂产品性能。为了生产性能优良的乙烯与丁烯-1共聚产品,需要将四氢呋喃的含量严格控制在较窄的范围。     

Core–shell type multi‐arm azide polymers based on hyperbranched copolyether as potential energetic materials in solid propellants

A series of novel multi‐arm azide copolymers (POGs) with the same hyperbranched poly[3‐ethyl‐3‐(hydroxymethyl)oxetane] core (PEHO‐c) and different content of linear glycidyl azide polymer shell (GAP‐s) have been synthesized by sequential cationic ring‐opening polymerization and azidation. Detailed structural information of these copolyethers was deduced from Fourier transform infrared, ¹H NMR and inverse gated decoupled ¹³C NMR spectroscopies, matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry, gel permeation chromatography and elemental analysis. The molecular weight of POG having GAP‐s and PEHO‐c with a molar ratio 14.95:1 (R_s/c) was around 31 000 g mol^?1, far above that of linear GAP (around 4000 g mol^?1). The apparent viscosity and glass transition temperature (?51 to ?23 °C) decreased first and then slightly increased with increasing molecular weight. Thermal analysis revealed that all the obtained POGs exhibited excellent resistance to thermal decomposition up to 220 °C. Moreover, the energetic properties, investigated using oxygen bomb calorimetric measurements, indicated that the enthalpy of formation of the POGs was higher than that of general linear GAP, but similar to that of branched GAP under reasonable R_s/c. The compatibilities of the POGs with common materials used in solid propellants were studied using differential scanning calorimetry and the results indicated that the POGs had good compatibility with these materials. © 2017 Society of Chemical Industry