扩链剂联用对PETG扩链反应与流变性能的影响

通过扩链反应对聚对苯二甲酸乙二醇1,4环己烷二甲醇酯（PETG）进行改性以提高PETG的熔体强度和黏度。采用熔体流动速率仪、旋转流变仪及转矩流变仪考查了扩链剂的使用方式对PETG结构及流变性能的影响。结果表明,酸酐类和环氧类多官能团单体联用对PETG的扩链效果最好,PETG的熔体流动速率由12.83 g/10 min降低至7.50 g/10 min,零剪切黏度（η0）由2022.8 Pa·s增加到4764.2 Pa·s,特征松弛时间（τ0）由0.78 s增加到3.58 s;改性后PETG仍保持着线形结构而未形成凝胶。     

RTM专用混合型树脂体系研究——反应特性与工艺特性研究

本文采用乙烯基酯树脂和环氧树脂体系共混改性的方法。研究和开发具有良好工艺性、耐热性和力学性能的低成本ＲＴＭ用树脂体系。研究表明，乙烯基酯树脂和环氧树脂体系具有良好的共混特性。ＤＳＣ及粘度分析研究表明，混合型树脂体系中的乙烯基酯组份分散了环氧树脂的反应放热，有效降低了７１１环氧树脂的反应速度和改善了树脂的工艺特性。使混合型树脂具有较好的ＲＴＭ工艺低粘度平台工艺性能。所研究的混合型树脂体系可用于ＲＴＭ     

The self-wiping co-rotating twin-screw extruder as a polymerization reactor for methacrylates

The self-wiping co-rotating twin-screw extruder was studied as a reactor for two polymerizations in bulk: the homopolymerization of n-butylmethacrylate and the copolymerization of n-butylmethacrylate with 2-hydroxypropylmethacrylate. The influence of the extrusion parameters on the product was analyzed. With both reactions, conversions up to 95% were obtained. Nevertheless, a significant difference was observed in the working domain of both polymerizations, in which a stable reactive extrusion process could be attained wherein the discharge rate is constant and equals the feed rate. In the case of the relatively fast copolymerization, both the throughput and the screw rotation rate could be raised without endangering the stability of the process. This was not the case for the homopolymerization studied. It was determined that the stability of the process depends on the reaction velocity and the product viscosity. Within the boundaries of the working domain, the molecular weight could be influenced by adjustments of the extrusion parameters.     

Increase in viscosity and its influence on polymerization processes

In the course of polymerization in homogeneous systems, the viscosity of the reaction mass increases by several orders of magnitude. The viscosity increase is affected by reaction conditions, concentration and properties of the formed polymer. Empirical correlations for homogeneous and heterogeneous polymerizations are given. Viscosity significantly affects the polymerization kinetics as well as heat, mass and momentum balances of the polymerization reactor. The influence of viscosity and its increase on conductive heat transfer, stirrer power input and cooling capacity, molecular diffusion and mass transfer coefficients, mixing time and residence time distribution in homogeneous and heterogeneous polymerizations in stirred tank and tubular reactors is reviewed.     

回收PET的增粘研究

分别使用均苯四甲酸二酐（PMDA）、环氧树脂及两者的混合物作为回收PET瓶的扩链剂,利用反应挤出技术在同向双螺杆挤出机中反应,研究回收PET瓶烘干时间、扩链剂种类、扩链剂用量对PET产物的特性粘度、端羧基的质量摩尔浓度的影响。实验结果表明：均苯四甲酸二酐（PMDA）和环氧树脂均对PET有一定的扩链作用,且二者合用时扩链效果更佳,反应后PET的特性粘度由0．45dl／g提高到0．58dl／g,摩尔质量也显著提高;随着干燥时间增加,改性的回收PET样品的特性粘度增加的幅度较大;其中单独使用环氧树脂为扩链剂时,可以使反应后的PET端羧基的质量摩尔浓度显著下降。     

Molecular Weights of Reactive Systems Employing Anionic Polymerization

Anionic polymerization has been successfully employed for reactive processing, the most notable example being that of nylon RIM [1] using caprolactam polymerization. Here, fast polymerization is achieved with the help of a combination of a catalyst and an initiator under practically anhydrous conditions. This polymerization method leads to a narrow molecular weight distribution and a Poisson distribution of the individual chain lengths. Analytical expressions for calculating the number-average and weight-average degrees of polymerization of the polymer chains from the degree of conversion have been derived based on this knowledge [2]. But in a reactive system where a substantial amount of monomer may be present during most of the processing time, the average must include the monomer units present. Only such averages will be of use in correlations of molecular weight with viscosity and degree of conversion with viscosity, which are of importance in the design of a reactive processing system. A method to compute such average molecular weights is presented here.     

A modified capillary dilatometer for polymerization

A relatively simple and inexpensive instrument giving good accuracy and easy operation has been developed for the measurement of volume change in monomer polymerizations. The instrument is based on a previously described capillary dilatometer intended for automatic operation.     

Effect of reactive compatibilization on the interfacial slip in nylon‐6/EPR blends

The viscosity of uncompatibilized polymer blends often shows a negative deviation from a log‐additivity rule at shear rates relevant to processing. This deviation has been attributed to interfacial slip, which is related to the loss of entanglements at the interface. In this work interfacial slip and the effect of reactive compatibilization on this phenomenon are studied in blends consisting of ethylene‐propylene rubber and nylon‐6. The viscosity and morphology of blends with various compositions and compatibilizer content are investigated systematically. The results indicate that interfacial slip can indeed be important in uncompatibilized systems whereas it is suppressed in compatibilized blends. This is further supported by a study of the viscosity of multilayer structures. Both the effect of reactive compatibilization and of the number of layers on the rheology are studied. Again it is demonstrated that reactive compatibilization suppresses interfacial slip.     

Investigation of readily processable thermoplastic-toughened thermosets. II. Epoxy toughened using a reactive solvent approach

The fracture toughness of epoxy thermosets was increased by up to 220% using very low-molecular-weight (∼ 1000 g/mol) imide thermoplastic. The objective was to produce a low-viscosity prepolymer that could be easily autoclave-processed to give a tough thermoset. Here, an homogenous epoxy prepolymer was prepared by first synthesizing very low-molecular-weight linear aromatic imide (∼ 1000 g/mol) directly in a liquid allyl phenol reactive solvent, followed by dissolution of the epoxy (Epon® 825) and the cure agent (DDS) directly in the thermoplastic solution. The allyl phenol both cures into the epoxy network, through phenol functional groups, and accelerates the cure. The viscosity of the pure epoxy was 1.4 Pa · S at 30°C. The prepolymer formulations ranged from ∼ 5–33 Pa · S at 30°C, but all reduced to less than 1 Pa · S at 90°C. The onset of cure is well above 90°C so the prepolymer viscosity is within the range for autoclave processing. The cured resin plaques were not transparent, but phase-separated domains were not found by scanning electron microscopy, indicating that the domain size is below the detection limit of the instrument. The reactive solvent causes a decrease in both the T_g and the high temperature modulus of the thermoset. Introduction of the thermoplastic results in partial recovery of the T_g and modulus. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 935–942, 1998     

Reactive polymer processing

This paper addresses some of the general engineering problems in reactive polymer processing: thermal effects on reactor stability and polymer properties due to rapid exothermic polymerization, the formulation of reaction viscosity relationships required in simulations, and the generation of flow and mixing via technology available from both ends of the viscosity spectrum, which is spanned in its entirety when going from monomer to molded polymer. Methods of analysis are discussed and general design concepts are suggested, which can be applied to the construction of innovative future processing equipment.     

In situ fluorescence spectroscopic studies of polymerization of anaerobic adhesives

Anaerobic adhesives cured by a redox initiated free radical mechanism contain acrylate monomers, stabilizers, accelerators, a nonreactive fluorophore used as an inspection aid, and various nonreactive ingredients to modify polymer properties and rheology. Fluorescence spectroscopy has shown that collisional quenching of the fluorophore due to an amine cure‐accelerator is reduced by rising viscosity during polymerization, thus resulting in an increase in fluorescence intensity. By monitoring the changes in fluorescence intensity with an in situ fiber‐optic method, room temperature polymerizations have been characterized both in a model formulation containing only reactive ingredients as well as in a real commercial formulation containing many nonreactive ingredients. The results from this fluorescence method on polymerization monitoring show excellent correlation with the FTIR results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

An automatic laboratory reactor for homogeneous polymerization of methyl methacrylate

An automatic stirred tank reactor of laboratory scale has been developed for on-line measurement of conversion, viscosity, and molar mass distribution of homogeneous polymerizations. For these on-line measurements, a fraction of the reaction mixture is bypassed through a densimeter and a viscometer. Samples are taken at intervals of 15 min, diluted semi-automatically, and then injected into a high performance gel permeation chromatograph for determination of the molar mass distribution of the polymers. A microcomputer collects the measured data, calculates the monomer conversion and the output data for different control units. In this study, methyl methacrylate is polymerized batch- and semi-batchwise with ethyl acetate as solvent and in the presence of different initiators. The semi-batch polymerizations are carried out at constant reaction rate by feeding the initiator and at a given increase in viscosity by feeding the solvent.     

Structurally controlled polymerizations of methacrylates and acrylates

Progress in the structure control of polymethacrylates and polyacrylates through stereospecific living polymerization are described. Three types of stereospecific living polymerizations have been developed for methacrylate polymerization: isotactic with t‐C₄H₉MgBr, syndiotactic with ­t‐C₄H₉Li/R₃Al, and heterotactic with t‐C₄H₉Li/bis(2,6‐di‐t‐butylphenoxy)methylaluminium [MeAl(ODBP)₂]. The last initiator system has been proved effective for monomer‐selective living copolymerization of methacrylates. The living nature of these polymerizations allows extensive use for the syntheses of stereoregular block polymers and copolymers, and end‐functionalized polymers such as macromonomers. Through stereospecific polymerizations and copolymerizations of macromonomers, comb polymers and graft copolymers with defined stereoregularities in the main chain and side chains could be obtained. Some properties of these stereoregular polymers are also described, including stereocomplex formation and solution viscosity. Stereospecific polymerizations of crotonates leading to diisotactic, diheterotactic and disyndiotactic polymers are also discussed. Supercritical fluid chromatography (SFC) has been proven to be useful for isolating uniform polymers from stereoregular poly(methyl methacrylate)s (PMMAs) with narrow molecular weight distribution. Uniform end‐functionalized polymers have been used to construct more elaborate uniform polymer architectures such as stereoblock, star, and comb polymers, and copolymers. The uniform polymers have been proven quite useful for the studies of the relationship between structures and properties such as glass transition temperature, melting temperature and solution viscosity. Particularly interesting is the use of isotactic and syndiotactic uniform PMMAs for the understanding of stereocomplex formation in certain solvents such as acetone. Furthermore, a uniform stereoblock PMMA was found to undergo intramolecular complexation in addition to intermolecular complexation in acetone. Uniform star and comb PMMAs were also prepared and found useful for discussing the effect of branching on the solution viscosity. © 2000 Society of Chemical Industry     

聚脲多元醇的合成研究

在实验室以间歇法制备了聚脲多元醇,在反应体系中加入分散剂S,研究分散剂S对体系粘度、固含量、贮存稳定性的影响,发现分散剂的加入有利于降低反应体系和产品的粘度,提高聚脲多元醇的固含量和稳定性。采用FTIR、DSC、粒径分布仪、TEM等手段分析了聚脲分散体的结构、热性能、分散性及形态。     

Novel Synthesis of Reactive Poly(ethylene glycol) grafted Poly(L-lactide) via Two Step Polymerizations

Summary Novel poly(L-lactide)-graft-poly(ethylene glycol) having reactive group at the end of grafted chain was prepared by two step polymerizations: ring-opening polymerization of L-lactide and 1,2-epoxy-5-hexene followed by radical polymerization of the product of ring-opening reaction and poly(ethylene glycol) methacrylate. Al(Et)₃·0.5H₂O and AIBN were used as catalyst and initiator for the two step polymerizations respectively. The structure of the synthesized polymers was also characterized.     

Polypropylene–phenol formaldehyde‐based compatibilizers. I. Preparation and characterization

This work deals with the synthesis of a new type of compatibilizer suitable for blends or alloys of polypropylene and engineering polymers having aromatic residues or functionality complimentary to hydroxyl. Polypropylene–phenol formaldehyde graft copolymers from thermoplastic phenol formaldehyde (PF) resins and functionalized polypropylene (f‐PP) were synthesized by reactive extrusion. The content of PF in the graft copolymer was determined by reaction variables like type and density of functionality on PP, molecular weight of PF, and viscosity ratio of f‐PP and PF. The results showed that the viscosity ratio is of primary importance for such reactive processing. Also, type and concentration of the functional groups were important variables. The glycidyl methacrylate functionality resulted in higher conversions than did PP‐g‐maleic anhydride within the available reaction times. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 347–354, 2000     

Reactive extrusion of in-situ composite based on PET and LCP blends

The “in-situ” compatibilization for a PET/LCP blend via transesterification reactions in a twin-screw extruder having a very short residence time is investigated through thermal, rheological, and mechanical studies. Inclusion of a small amount of liquid crystalline polymer (LCP) enhanced the crystallization rate of the poly(ethylene terephthalate) (PET) matrix. It acted as a nucleating agent. LCP lowered the blend viscosity above T_cn (crystalline-nematic transition temperature), working as a processing aid. However, the addition of dibutyltindilaurate (DBTDL) as a reaction catalyst was found to increase the viscosity of the blends, diminish the size of the dispersed phase, enhance its adhesion with the matrix, and lead to an increase of mechanical properties of two immiscible phases. Hence DBTDL is helpful in producing a reactive compatibilizer by reactive extrusion at the interface of this polyester blend system. The optimum catalyst amount turned out to be about 500 ppm when the reaction proceeds in 90/10 PET/LCP polyester blend systems. Its effect on the mechanical properties is discussed in detail. The structural change of reactive blend was identified by H¹ NMR and wide angle X-ray diffraction patterns.     

Synthesis and characterization of star-like microgels by one-pot free radical polymerization

A one-pot free radical polymerization process was used to prepare methyl acrylate/ethylene glycol dimethacrylate (MA/EGDMA) and methyl methacrylate/ethylene glycol dimethacrylate (MMA/EGDMA) polymers. The role of monomer and crosslinker reactivity ratios in producing different network structures was demonstrated. While both systems produced branched polymers that exhibited low intrinsic viscosities with little variation across a wide range of molecular weights, the star-like microgels formed between a less reactive monomer (MA) with a more reactive crosslinker (EGDMA) gave lower bulk solution viscosities than the more statistical polymers formed between similarly reactive monomers and crosslinkers (MMA and EGDMA). This paper presented a simple and cost-effective synthetic route for the production of polymers with high molecular weight and low viscosity with considerable potential for industrial-scale processing.     

A Novel Process for Ultrasound‐Induced Radical Polymerization in CO2‐Expanded Fluids

Summary: A strong viscosity increase upon polymerization hinders cavitation and subsequent radical formation during an ultrasound‐induced bulk polymerization. In this work, ultrasound‐induced radical polymerizations of methyl methacrylate (MMA) have been performed in CO₂‐expanded MMA in order to reduce the viscosity of the reaction mixture. For this purpose, the phase behavior of CO₂/MMA systems has been determined. With temperature oscillation calorimetry, the influence of CO₂ on the viscosity and on the reaction kinetics of ultrasound‐induced polymerizations of MMA has been studied. In contrast to polymerizations in bulk, this technique shows that a low viscosity is maintained during polymerization reactions in CO₂‐expanded MMA. As a consequence, a constant or even increasing polymerization rate is observed when pressurized CO₂ is applied. Moreover, the ultrasound‐induced polymer scission in CO₂‐expanded MMA is demonstrated, which appears to be a highly controlled process. Finally, a preliminary sustainable process design is presented for the production of 10 kg/h pure PMMA (specialty product) in CO₂‐expanded MMA by ultrasound‐induced initiation.

Process flow diagram of the ultrasound‐induced polymerization of MMA in CO₂‐expanded MMA.