Effects of mixing strategy on catalyst‐assisted reactive blending of polycarbonate and polyethylene terephthalate

Reactive melt mixing of polycarbonate (PC) and polyethylene terephthalate (PET) blends with constant composition of 80:20 in the presence of a freshly added catalyst was conducted through a two‐step method. At first, PC and PET underwent premixing and melt mixed in the absence of a fresh catalyst. Then, mixing continued with catalyst addition under the same previous condition. The effects of varied premixing times from 1 to 5 min and mixing intensity at rotor speeds of 30 and 50 rev/min (rpm) were separately evaluated in transesterification reaction. The results of solubility analysis showed that the longer premixing time and the higher mixing rate enhanced the rate and extension of reaction. Fourier transform infrared (FTIR) spectroscopy and thermal analysis by differential scanning calorimetry were conducted on specimens on the basis of solubility separations. The height ratio of carbonyl group peaks of PC and PET phases were calculated for their corresponding FTIR spectra. The height ratio for PET showed a good correlation with solubility data. Moreover, crystallinity of PET phase was influenced by the reaction which was analyzed by solubility parameters. J. VINYL ADDIT. TECHNOL., 25:127–133, 2019. © 2018 Society of Plastics Engineers     

Recycling poly(ethylene terephtalate) wastes: Properties of poly(ethylene terephtalate)/polycarbonate blends and the effect of a transesterification catalyst

The article addresses the issue of recycling of poly(ethylene terephtalate) (PET) by melt blending with polycarbonate (PC). PET/PC blends containing various amounts of the immiscible polymers were prepared in a twin‐screw extruder. Selected compositions were also prepared in the presence of an Sn‐based catalyst to assess the influence of transesterification during melt mixing. The degree of miscibility in the blends was studied using differential scanning calorimetry, scanning electron microscopy, and mechanical testing. PET/PC blends exhibit enhanced tensile properties in comparison to neat components for compositions of PET higher than 50% and these properties are improved by the addition of a transesterification catalyst. The PET/PC blend containing 20 wt% of PC, prepared with stannous octoate, shows the smallest size of the dispersed phase because of transesterification reactions that generate copolymer molecules at the interface between the immiscible polymers. The melting temperature of PET is decreased with the increase of the PC content in blends extruded in the presence of the catalyst. Also, the temperatures of the cold crystallization of PET are higher than those of similar blends without added catalyst. Both features give rise to better molding properties because of a shortening of the cooling time in the range of 50–90 wt% of PET. POLYM. ENG. SCI. 46:1378–1386, 2006. © 2006 Society of Plastics Engineers     

The hydrolytic stability of glass fiber reinforced poly(butylene terephthalate), poly(ethylene terephthalate) and polycarbonate

The hydrolytic stability of glass fiber reinforced poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and polycarbonate (PC) was studied. The activation energies in kcal/mole for hydrolysis are 26 for PBT and 23 for PET. Both PBT and PET contain 30 percent glass fiber reinforcement. The hydrolysis rates for a series of experimental PC's containing 10, 30 and 40 percent glass were obtained from GPC data. These increase with glass concentration but are lower than that of the unreinforced PC. Melt flow rate changes are a good measure of the hydrolytic degradation of PET. However, in the time scale of these experiments, the tensile properties of glass reinforced PBT and PC do not correlate well with M?_w changes, unlike unreinforced PBT and PC polymers. Consequently, to compare these three glass fiber reinforced polymers, estimates of failure time must be based on changes in tensile strength rather than melt flow rate.     

Study of the reactions occurring during melt mixing of poly(ethylene terephthalate) and polycarbonate

In this work the reactions taking place during melt mixing of bisphenol-A polycarbonate (PC) with poly(ethylene terephthalate) (PET) were studied by selective degradation of PC sequences, solubility tests, and IR spectroscopy. It was found that exchange reactions between PC and PET took place, contrary to what has been previously suggested by other authors. Kinetic constants were evaluated from intrinsic viscosity measurements of PET blocks. The reaction rate was slow when only the Sb catalyst (residues of the PET polymerization) were present, but it was significantly accelerated by the addition of Ti(OBu)₄. In the presence of the latter catalyst, other side reactions, leading to discoloration and gas evolution, took place.     

钛系聚酯催化剂催化活性的影响因素研究

以二氧化钛(TiO2)为消光剂,采用钛系催化剂STiC-01或锑系催化剂乙二醇锑,在2 L间歇式聚合反应釜中制备半消光PET切片。根据PET切片的特性黏数和色度(L值及b值),比较了催化剂的催化活性,并研究了催化活性的影响因素。结果表明:在相同的聚合工艺条件下,STiC-01的钛用量为5μg/g(相对于PET质量)时的催化活性与乙二醇锑的锑用量为250μg/g(相对于PET质量)时的相当,PET切片的特性黏数达0.676 dL/g,钛系PET切片的L值高于锑系PET的,b值相当;磷化合物和镁化合物的用量应适当控制;催化剂在酯化前加入,TiO2在酯化后加入,STiC-01的催化活性不受TiO2的影响;相比乙二醇锑,STiC-01的催化活性受原料质量的影响小。     

增韧PC/聚酯合金研究

对增韧聚碳酸酯(PC)/聚酯[聚对苯二甲酸乙二醇酯(PET)和聚对苯二甲酸丁二醇酯(PBT)]合金进行了研究,结合合金的相形貌结果,分别选择PC和聚酯是连续相的合金进行了研究,同时对比了相同树脂比例下PC/PET和PC/PBT之间性能的差别。增韧剂选择甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)或MBS和接枝环氧基团的丙烯酸酯类增韧剂(X-GM A)复配物。结果表明,使用相同的增韧剂,PC是连续相的情况下,冲击强度更高,相同树脂比例情况下,PC/PET合金冲击强度比PC/PBT的差,拉伸和弯曲强度相差不大,PC/PET合金的熔体稳定性能比PC/PBT的差,PC是连续相合金的熔体稳定性比聚酯是连续相的要好,含有X-GMA的合金熔体稳定性能更好,这些结果和酯基的热分解、PET分子链运动活性比PBT的差以及酯交换程度的差异等有直接的关联。     

New catalysts for poly(ethylene terephthalate)-bisphenol a polycarbonate reactive blending

The effects of various catalysts on the reactive blending of poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) was investigated. The various catalysts employed for PET syntheses, Ti(OBu)4, SmL₃, EuL₃, Ca + Sb, CeAc₃, Er(NO₃)₃·B₁₂C₄ and Tb (acac)₃·diPy (where L is o-formylphenolate; B₁₂C₄ is a crown ether, benzo-12-crown-4; acac is acetylacetonate; and diPy is 2,2′-dipyridyl) have shown a different catalytic activity toward exchange reactions. Solubility tests, in solvents able to separate unreacted PET and PC, and selective degradation of the PC segments, combined with ¹H NMR spectroscopy and size exclusion chromatography, made it possible to order the catalysts according to their catalytic activity: Ti(OBu)4 ? SmL₃ > EuL₃ > Ca + Sb > CeAc₃～Er(NO₃)·B₁₂C₄ > Tb (Acac)₃·diPy ≈ 0. © 1995 John Wiley & Sons, Inc.     

CO2在PET熔体中的溶解度

通过高温高压磁悬浮天平(MSB)测定表观溶解度、高温高压视窗釜进行溶胀度校正的方法研究了CO₂在PET熔体中的溶解度,考察了温度、压力对改性前后PET在CO₂环境中的溶胀度和CO₂溶解度的影响。结果表明,PET在CO₂环境中的溶胀度和CO₂溶解度均随温度的增加而减小,随压力增加而增加,但高压下溶胀度的增加趋势减缓并趋于某定值;与常规线性PET相比,改性PET具有较小的溶胀度和溶解度。在250~280℃,4~6 MPa下,CO₂在PET熔体中的溶解度具有10^-2 g CO₂·(g PET melt)^-1的量级。1~6 MPa下CO₂在PET熔体中的溶解行为符合亨利定律,利用最小二乘法拟合得到了CO₂在PET熔体中的溶解热。     

Melt polycondensation of L‐lactic acid catalyzed by 1,3‐dialkylimidazolium ionic liquids

BACKGROUND: In syntheses of biodegradable and bioresorbable polymers, efficient metal‐free catalysts are very desirable as the resulting products may be more biocompatible. As an attempt to find new metal‐free catalysts, 1,3‐dialkylimidazolium salts, the most commonly used ionic liquids or organic melt salts, were used as single‐component catalysts in the melt polycondensation of L ‐lactic acid for the first time. The resulting poly(L ‐lactic acid) (PLLA) was characterized using gel permeation chromatography, ¹³C NMR, DSC and polarimetry. RESULTS: It has been found that less bulky substituents on the imidazolium ring are conducive to catalytic activity. PLLA with molar mass of about 20 000 g mol^?1 was synthesized at high yield (over 70%) in the presence of various 1,3‐dialkylimidazolium salts. The product exhibits satisfactory color (white to slightly yellow), optical purity (89–95%) and crystallinity (40–55%). A possible catalytic mechanism is proposed. CONCLUSION: As compared with the well‐known binary catalyst system SnCl₂ · 2H₂O/toluene sulfonic acid, the catalysts used in this investigation are better in terms of increasing PLLA yield and preventing discoloration and comparable in terms of racemization. Copyright © 2008 Society of Chemical Industry     

Kinetics of the reaction of propylene oxide with carbon dioxide in the presence of tetrasubstituted ammonium and phosphonium halogenides

Reactions of alkylene oxides with carbon dioxide underlie the industrial technology of ethylene- and propylene carbonates. Looking for new catalytic systems for these processes remains of interest due to the possibility of creating a new energy-saving process for the production of ethylene and propylene glycols. This work is aimed at comparing the catalytic activity of halogenides in the reaction of propylene oxide (PO) and carbon dioxide in the presence of tetrasubstituted ammonium and phosphonium halogenides, and evaluating the feasibility of using them in designing industrial technologies for the production of alkylene carbonates and glycols as active catalytic systems. Triphenylphosphine halogenides have been shown to possess high catalytic activity as compared to triethanolamine-based analogs. In terms of efficiency, triphenylphosphonium bromides are as good as the familiar catalysts based on potassium iodide. The high activity of these catalysts in the reaction for propylene carbonate (PC) production and their good solubility in the reaction medium allow us to propose them for the development of industrial technology for the subsequent production of alkyl carbonates and alkylene glycols.     

A study on blends of liquid crystalline copolyesters with polycarbonate. II. Transesterification control

The inhibited and catalyzed ester exchange (transesterification) during melt blending of poly(bisphenol-A carbonate) (PC) and liquid crystalline poly(oxybenzoate-co-ethylene terephthalate) (POB–PET 40/60; P46) was investigated with differential scanning calorimetry. It was found that the ester exchange between P46 and PC was effectively inhibited for a 20% P46 blend at 240°C, as further confirmed by nuclear magnetic spectroscopy. When the blending temperature and P46 concentration increased, only the transesterification between the PET segment in P46 and PC took place under inhibition. The morphology of the blends was analyzed with scanning electron microscopy and displayed a disconnected interface between P46 and PC under inhibition. Conversely, the transesterification took place between the POB segment in P46 and PC when a catalyst was added. © 1996 John Wiley & Sons, Inc.     

Asphaltene/polymer composites: Morphology,compatibility, and rheological properties

In this study, we investigate the use of asphaltene, a natural waste product that is inevitably formed during heavy oil processing, as a filler in polymer composites. The focus of this work is on the compatibility of various asphaltenes, featuring different polarities, with several polymers, including polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), and polycarbonate (PC). The Hansen solubility parameters were plotted to predict the compatibility of polymers with different asphaltenes. Then, polymer composites were prepared by two common techniques: melt mixing and solution mixing. The dispersion state of the asphaltenes in each polymer was investigated by using imaging and rheological techniques. This work showed that the network structure of the asphaltenes and, thus, the final properties of the composites can be controlled by the polarity of asphaltenes, mixing technique, and melt viscosity of the polymer. For instance, more polar asphaltene (Asph P) produced smaller aggregates in PMMA, which has a higher polar solubility parameter than PP or PS. At 2.5 wt.% of asphaltene, Asph P showed 26% and 177% larger asphaltene agglomerates in PP and PS, respectively, than the less polar asphaltene (Asph Al). PS/asphaltene and PMMA/asphaltene composites prepared by the solution mixing method exhibited better dispersion compared to their melt-mixed counterparts. In melt-mixed composites, the dispersion quality of the asphaltene was better for polymers with higher melt viscosity. Thus, a careful choice of polymer, asphaltene, and preparation conditions can be used to tune the properties of asphaltene/polymer composites.     

Recent Advances in Amphiphilic Polymers as the Stabilizers of Colloidal Gold Nanoparticles

Gold nanoparticles (AuNPs) exhibit high catalytic activity as catalysts and have potential applications in biomedicine. To prevent the aggregation of colloidal AuNPs, the stabilizers including organic small molecules, organic ligands, inorganic ligands, and polymers, are necessary to be added in the synthesis of colloidal AuNPs. Among these stabilizers, amphiphilic polymers have attracted significant attention from scientists in the development of polymerization and modification methods. To date, numerous efforts are employed to develop amphiphilic polymers as the stabilizers of colloidal AuNPs but are not well‐summarized yet. In this review, four parts (amphiphilic linear polymers, amphiphilic graft polymers, amphiphilic hyperbranched polymers, and amphiphilic dendrimers) according to the polymer architectures will be discussed. Comprehensive understanding of amphiphilic polymers that are used for stabilizing colloidal AuNPs is provided.     

Synthesis and chemical modification of new epoxy resins containing alkylaminopyridines

A new series of epoxy resins containing 4‐(N,N‐dialkylamine)pyridines (DAAP) functionality was prepared by reaction of 4‐aminopyridine or/and aniline with epichlorohydrin. Then, hydroxyl groups in the polymeric chain underwent a chemical modification with acyl chloride. Modification of the side group and backbone of the chain resulted in an enhancement of solubility of the linear catalyst with catalyzed system and also led to an accelerated acylation. Here, acetylation of tert‐butyl alcohol was monitored by means of chromatographic analyses for determining the catalytic power of these polymeric catalysts. Catalytic activity of the modified linear poly(4‐aminopyridine‐epichlorohydrin‐aniline) was found to be more effective than that of DMAP, and catalytic activity of network polymers in a heterogeneous system was found to be somewhat lower than that of any of its linear analogs. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1101–1105, 1999     

钛系催化剂对聚酯缩聚反应速度和热稳定性影响的研究

研究了K2TiF6、(C4H9O)4Ti、Sb2O33种催化剂的缩聚反应速度,并对3种催化剂合成的切片进行了热稳定性比较(Δ[η]、TG)。结果表明:钛系催化剂的催化活性明显高于常规Sb2O3,其中以(C4H9O)4Ti的催化活性最高;(C4H9O)4Ti的动力学曲线具有阶段性,其高催化活性体现在缩聚反应的中后期;对3种催化体系制得的PET切片进行热稳定性测试的结果表明:采用(C4H9O)4Ti作为催化剂配合稳定剂SI与Co2+可制得色相良好,热稳定性高的聚酯切片。     

高阻燃PC/PET合金材料的制备与性能

使用双螺杆挤出机熔融共混制备了聚碳酸酯/聚对苯二甲酸乙二醇酯(PC/PET)合金。研究了阻燃剂的种类、相容剂种类以及PET树脂的黏度对材料的阻燃性能、力学性能和热性能。结果表明,添加16%苯氧基四溴双酚A碳酸酯齐聚物,试样阻燃等级可以达到UL94 V-0级别(0.8 mm),缺口冲击强度达到50.2 kJ/m²,球压痕直径小于2 mm。三氧化二锑的加入会降低材料的耐热性能以及灼热丝起燃温度,乙烯-丙烯酸甲酯-甲基丙烯酸缩水甘油酯三元共聚物(E-MA-GMA)对PC/PET合金的相容作用最优,材料的冲击强度最高。丙烯酸酯-丁二烯-苯乙烯共聚物(MBS)和丙烯酸酯-有机硅共聚物对材料的增韧效果较弱,但是灼热丝起燃温度可以达到875℃。选择中等黏度PET树脂有利于提高材料的热变形温度,减小球压痕直径而高黏度PET树脂则有利于提高材料的缺口冲击强度。     

PET/PC blends: Effect of chain extender and impact strength modifier on their structure and properties

Methylene diphenyl diisocyanate (MDI) affects the morphology, rheological, mechanical, and relaxation properties, as well as tendency to crystallize of PET in PET/PC/(PP/EPDM) ternary blends produced by the reactive extrusion. Irrespective of the blend phase structure, the introduction of MDI increases the melt viscosity (MFI dropped), resulting from an increase in the molecular weight of the polymer chains; the PET crystallinity was also reduced. MDI favors compatibility of PET with PC in PET/PC/(PP/EPDM) blends. This is explained by intensified interphase interactions on the level of segments of macromolecules as well as monomer units. The presence of MDI causes a substantial rise in the dynamic shear modulus within the high‐elastic region of PET (for temperature range between T_g,PET and that of PET cold crystallization); the processes of PET cold crystallization and melt crystallization become retarded; the glass‐transition temperatures for PET and PC become closer to each other. MDI affects insignificantly the blend morphology or the character of interactions between the disperse PP/EPDM blend and PET/PC as a matrix. PP/EPDM reduces the intensity of interphase interactions in a PET/PC/(PP/EPDM), but a rise in the degree of material heterogeneity. MDI does not change the mechanism of impact break‐down in the ternary blends mentioned above. Increased impact strength of MDI‐modified materials can be explained by higher cohesive strength and resistance to shear flow at impact loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PET/PC合金的制备

介绍了开发聚酯PET/PC合金的必要性及应用优势,用熔融共混法制备PET/PC的工艺条件。对PET/PC合金的相容性和力学性能进行了研究。结果表明:制备PET/PC合金可行,且其力学性能完全满足工程塑料方面的应用。并在某些方面改善了PC的力学性能。     

Dendronized Poly(Ru‐BINAP) Complexes: Highly Effective and Easily Recyclable Catalysts For Asymmetric Hydrogenation

A new kind of dendronized polymeric chiral BINAP ligands has been synthesized and applied to the Ru‐catalyzed asymmetric hydrogenation of simple aryl ketones and 2‐arylacrylic acids. These dendronized poly(Ru‐BINAP) catalysts exhibited high catalytic activity and enantioselectivity, very similar to those obtained with the corresponding parent Ru(BINAP) and the Ru(BINAP)‐cored dendrimers. It was found that the pendant dendrons had a major impact on the solubility and the catalytic properties of the polymeric ligands. These polymeric catalysts could be easily recovered from the reaction solution by using solvent precipitation, and the reused catalyst showed no loss of activity or enantioselectivity.     

Pseudocrown ethers based on polyphosphazene as effective catalysts of nucleophilic substitution reactions

Summary Polymer pseudocrownethers based on polyphosphazene are active catalysts of nucleophilic substitution reactions. With respect to the catalytic activity, polyphosphazene is a more suitable carrier of oligo(oxyethylenes) than poly(styrene-co-divinylbenzene). With increasing length of oligo(oxyethylene) branches the catalytic activity of polymers increases. The favorable effect of the content of pseudocrownether structures is particularly visible in polymers having a longer oligo(oxyethylene) chain in those reactions in which the polymer acts as a solid cosolvent. The catalysts preserve their activity also if reused.