反应挤出方法制备高熔体强度聚丙烯

利用反应挤出机通过反应挤出微交联的方法制备出高熔体强度聚丙烯（PP）。考察了反应单体用量、过氧化物用量、反应温度以及螺杆转速对产物熔体强度、熔体流动速率和凝胶含量的影响。结果表明。在100．00份PP中加入1．00份的反应单体二乙烯基苯，以0．04份的过氧化二异丙苯作为引发剂，机筒反应段温度为190℃、螺杆转速为40r／min时，得到产物的熔体强度最佳。比原料PP的提高10倍。产物中有微量的交联，产物的熔融峰温略有提高。仍然可用普通PP相同的成型方法。     

聚合物反应挤出技术及其应用研究进展

聚合物反应挤出技术是一门将聚合反应与挤出成型结合在一起的新兴工艺,简述了聚合物反应挤出技术的原理及特点,综述了聚合物反应挤出技术在本体聚合、接枝反应、反应共混、以及可控降解等方面的应用研究新进展。     

反应挤出技术在高聚物本体聚合中的应用进展

反应挤出技术是高聚物加工的一种新技术，是目前国际上竞相投资的热点。在高聚物本体聚合中反应挤出技术具有广阔的发展前景。重点介绍了反应挤出技术的特点，阐述了用反应挤出技术进行本体聚合制备高聚物的优点，综述了国内外近十年来反应挤出技术在高聚物本体聚合中的应用进展。     

Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers

Exfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry     

Production of Thermoplastic Starch/MMT‐Sorbitol Nanocomposites by Dual‐Melt Extrusion Processing

A “green” processing method, dual‐melt extrusion, was used to prepare thermoplastic starch/montmorillonite nanocomposites without organic reactions in the solution. XRD demonstrates that sorbitol enlarged the interlayer distance of MMT during the first step. MMT‐sorbitol, formamide and starch were used to obtain TPS/MMT nanocomposites in the second step. XRD and TEM reveal that TPS intercalated the layers of MMT. With increasing MMT content, improvements in thermal stability, tensile strength, Young's modulus and energy break, and a slight decrease of elongation at break, appeared. The effect of water content on the tensile strength and elongation at break was also studied.

     

Highly exfoliated poly(ϵ‐caprolactone)/organomontmorillonite nanocomposites prepared by in situ polymerization

Ethylene–propylene–diene rubbers (EPDM) with 2-ethylidene-5-norbornene (ENB), dicyclopentadiene (DCPD), and 1,4-hexadiene (HD) as third monomers have been vulcanized with peroxide and with a conventional sulfur vulcanization recipe, and their devulcanization was subsequently investigated for recycling purposes. The behavior of these vulcanizates during pure thermal devulcanization depends on the EPDM third monomer and the crosslinker used. Peroxide vulcanizates of ENB-EPDM devulcanize only to a small extent and predominantly by random scission, whereas peroxide vulcanizates of HD-EPDM devulcanize by crosslink scission. In contrast, sulfur vulcanizates of ENB-EPDM, devulcanize mainly by crosslink scission. During devulcanization of sulfur-cured HD-EPDM, scission of both crosslinks and main chains occurs. Sulfur-cured DCPD-EPDM cannot be devulcanized but shows further crosslinking instead. In those cases, where purely thermal devulcanization is already effective to a certain extent, diphenyldisulfide as devulcanization agent increases the effectivity during thermochemical devulcanization. Hexadecylamine as an alternative devulcanization agent is effective for ENB-EPDM but does not contribute to thermochemical devulcanization of HD-EPDM. In summary, devulcanization proceeds by different mechanisms in ENB-EPDM, DCPD-EPDM, and HD-EPDM. Explanations are given in terms of the chemical structures of the third monomers, the corresponding crosslinks, and devulcanization agents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable block copolymers with poly(ethylene oxide) and poly(glycolic acid‐valine) blocks

Biodegradable ABA triblock copolymers with poly(ethylene oxide) and poly(glycolic acid‐valine) blocks were synthesized via ring‐opening polymerization of cyclo(glycolic acid‐valine) using Ca‐alcoholates of hydroxytelechelic PEO as the initiator. The L‐valine residue racemized during copolymerization of cyclo(glycolic acid‐valine). The crystallization of the block copolymers decreases with decreasing PEO content in the triblock copolymers and with increasing length of the poly(glycolic acid‐valine) block. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2916–2919, 2002     

Synthesis and characterization of novel lipid functionalized poly(ε‐caprolactone)s

A series of novel lipid functionalized poly(ε‐caprolactone)s (PCLs) were synthesized through ROP of ε‐caprolactone in the presence of threo‐9,10‐dihydroxyoctadecanoic acid, synthesized from oleic acid. PCLs with different molecular weights were obtained by controlling the molar ratio of the initiator to the monomer. DSC and XRD analysis indicate that the crystallinity of PCLs decreased when compared to unfunctionalized PCL. The enzymatic degradation study shows that for samples with lower lipid derivatives content, a higher enzymatic degradation rate was observed because the lipase enzymes attack the ester bonds of the polymer; increased lipid content therefore inhibits the action of the lipase enzymes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of unsaturated poly(ε‐caprolactone) with a new titanium alkoxide initiator

Titanium alkoxides are widely used in the ring‐opening polymerization of ε‐caprolactone. In this study, functional poly(ε‐caprolactone) was synthesized with a new titanium initiator by a two‐step procedure: First, the titanium initiator, with an unsaturated group, was prepared by a classical organic reaction between 2‐hydroxyethylmethacrylate or 2‐allyloxyethanol with titanium tetrapropoxide; then, we initiated the polymerization of the ε‐caprolactone monomer in a glass reactor or twin‐screw extruder. By means of NMR spectroscopy, the structures of the initiators and polymers were determined. When 2‐hydroxyethylmethacrylate was used, there was a side reaction (transesterification) during the preparation of the initiator, and so it was impossible to obtain the expected product. With 2‐allyloxyethanol, the designed titanium initiator was synthesized with high purity, and the allyl moiety remained intact after the polymerization of ε‐caprolactone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable Polymers, 9. Technologically Relevant Aspects of Kinetics and Mechanism of Ring‐Opening Polymerization of L,L‐Dilactide

Poly(L ‐lactide) is manufactured by a cascade process comprising the fermentation of glucose substrate, oligomerization of L ‐lactic acid, cyclization depolymerization to L ,L ‐dilactide and ring‐opening polymerization of the cyclic diester. The process development requires detailed knowledge of kinetics, thermodynamics and reaction mechanism in all process stages. This paper aims to show the influence of micro‐ and macrokinetic factors on the course of the ring‐opening polymerization and the molecular parameters of the formed polyester. Monomer conversion and molecular weight of the polyester are determined by chemically active process parameters, like kind and concentration of catalyst and initiator, respectively, reaction temperature or presence of cocatalysts as well as by the intensity of mixing of the polymerizing melt. The highest polymerization rate is observed in presence of tin octoate, but this catalyst leads to a fast degradation of the formed polymer.     

In Situ synthesis of multiblock copolymers of poly(ϵ‐caprolactone) with different poly(ether diols) based polyurethane by reactive extrusion

Polyurethanes with multiblock copolymers of poly(?‐caprolactone) (PCL) and poly(tetramethylene oxide) glycol (PTMG) or poly(ethylene glycol) (PEG) as a soft segment were synthesized in situ via reactive extrusion from ?‐caprolactone (CL) and 4,4′‐diphenylmethane diisocyanate (MDI). The titanium alkoxide mixture generated from an ester‐exchange reaction between titanium propoxide [Ti(OPr)₄], and excessive PTMG or PEG was used as an initiator and catalyst. Compared to the reported fabrication of polycaprolactone‐based polyurethane (PCLU), the in situ reactive extrusion preparation not only explored a new rapid route for the fabrication of PCLU but also offered a simplified, controllable approach for the production of PCLU in a successive mass scale. A series of PTMG–PCLUs and PEG–PCLUs with different PCL block‐average degrees of polymerization (DP_n's) were prepared by only an adjustment of the relative concentration of CL in the reaction system, with a certain constant molar ratio of MDI to titanium alkoxide. ¹H‐NMR, gel permeation chromatography, and differential scanning calorimetry results indicate that all of the CL monomers were converted in the polymerization, and the molecular weight of the copolymers was about 8 × 10⁴ g/mol with a polydispersity index of approximate 2.4. With an increase in the PCL block‐average DP_n in PTMG–PCLU from 25 to 40, the tensile strength increased from 16.5 to 22.7 MPa, and the melting point increased from 46.1 to 49.5°C. It was also verified by PEG–PCLU prepared with organic Ti of lowered content in the initiator mixture that the mechanical properties could be greatly affected and dropped with decreasing content of organic Ti in the initiator mixture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Impact Fracture and Failure Behavior of in‐situ Polymerized,Ethylene/Butyl Acrylate Rubber Toughened Polyamide‐12

The fracture and failure behavior of in‐situ polymerized polyamide‐12 (PA‐12) blends prepared by reactive extrusion were studied in instrumented high‐speed (v = 1.2 m/s) impact bending tests using the linear elastic fracture mechanics approach. PA‐12 was polymerized in presence (up to 9 wt.‐%) of ethylene/butyl acrylate copolymers (E/BA) of varying BA content and melt viscosity. From the tests performed on injection molded specimens at ambient temperature and –40°C, respectively, the fracture toughness (K_d) and initiation fracture energy (G_d,i) were derived. K_d was less sensitive to either testing temperature or E/BA type and content. G_d,i, on the other hand, went through a maximum at room temperature and monotonously increased at T = –40°C as a function of modifier content. E/BA with higher melt viscosity and lower polarity (lower BA content) performed better than the lower melt viscosity, higher polarity E/BA counterpart. The dominant failure modes and their change both with temperature and modifier content were studied by fractography and discussed.     

pH‐responsive core crosslinked polycarbonate micelles via thiol‐acrylate Michael addition reaction

A facile method for the construction of pH‐responsive core crosslinked micelles (CCLMs) based on polycarbonate was developed. Biodegradable amphiphilic block copolymer monomethoxy poly(ethylene glycol)‐b‐Poly(AC) (mPEG‐b‐poly(AC)) with pendant acrylate group was synthesized by means of ring opening polymerization of acryloyl carbonate (AC). Then CCLMs were obtained via thiol‐acrylate Michael addition reaction between the pendant acrylate group in the hydrophobic block and the crosslinker 1,6‐hexanedithiol. DLS results showed that the CCLMs prepared from mPEG‐b‐poly(AC)₂₅ were more stable than uncrosslinked micelles (UCLMs) upon dilution by 10‐fold DMF. Model drug Coumarin 102 was then encapsulated into the micelles. The pH‐responsive release of coumarin 102 from the CCLMs was demonstrated by fluorescence spectroscopy. The core crosslinked polycarbonate micelles have a potential as efficient intracellular smart drug delivery platforms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44421.     

Continuous polymerization of lactam–lactone block copolymers in a twin‐screw extruder

Continuous copolymerizations of ?‐caprolactone with ?‐caprolactam and ω‐lauryl lactam were carried out in a modular intermeshing corotating twin‐screw extruder. Sodium hydride (initiator) and N‐acetyl caprolactam (coinitiator) were used to synthesize lactam–lactone copolymers in a twin‐screw extruder. We consider the variables of feeding order and feed rate of comonomers on the reactive extrusion of lactam–lactone copolymers. It was observed that simultaneous feeding of both monomers with initiator and coinitiator in the first hopper produced a mixture of homopolymers. When we fed the lactam into the first hopper and caprolactone sequentially into the second hopper, we obtained the lactam–caprolactone block copolymers. However, when we fed caprolactone first into the first hopper and the lactam into the second hopper, the extruded product was a mixture of poly(?‐caprolactone) and lactam monomer. We synthesized high molecular weight copolymers of poly(caprolactam‐b‐caprolactone) and poly(lauryl lactam‐b‐caprolactone) with different block lengths by sequential feeding of monomers. The block length of the block copolymer could be adjusted by controlling the feed rate of each monomer during reactive extrusion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1429–1437, 2003     

Continuous polymerization of ε‐caprolactone initiated by titanium phenoxide in a twin‐screw extruder

The continuous polymerization of ε‐caprolactone initiated by titanium phenoxide was carried out in both an internal mixer and a twin‐screw extruder. The polymerization was performed under different processing conditions, including various temperatures and screw speeds. To perform a kinetic study, samples were collected along the time axis (internal mixer) and along the screw axis (extruder). Size exclusion chromatography and proton nuclear magnetic resonance were used to study the evolution of the conversion degree with mixing time and with the extruder. The rheological behavior was also characterized. Temperature had a strong effect on conversion in the internal mixer, whereas in the twin‐screw extruder, both temperature and screw speed played major roles. The specificity of the titanium phenoxide to lead to high‐molar‐mass poly(ε‐caprolactone) under these processing conditions was also confirmed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Optical Fibers by Reactive Extrusion of Butyl Methacrylate

Summary: A process for the production of poly(butyl methacrylate) optical fibers by reactive extrusion is developed. The reactive system is adapted to the reduced reaction time in the extruder combining concepts based on the free volume theory and a kinetic model for the mass polymerization of butyl methacrylate. A kinetic model is proposed and the reaction evolution is simulated at different temperatures and initiator concentrations. This allows the choice of reaction conditions adequate for reactive extrusion technical limitations. Reactive extrusion experiments are carried out in a twin‐screw extruder and the effect of the different kinetic and process conditions on the reaction are analyzed in relation to the residence time distribution measured by an UV fluorescence method. Some optical properties of poly(butyl methacrylate) fibers are reported.

Conversion versus the position along the screw length.     

Direct Melt Extrusion Processing of Nylon 6/Clay Nanocomposites Based on Pristine Montmorillonite

Summary: An original direct melt extrusion processing of nylon 6/clay nanocomposites was reported based on pristine (Na⁺‐based) montmorillonite as well as a simple approach using a typical two‐screw extruder. By the application of intercalation agents as the thermodynamic assistants, this method is as an appropriate procedure for industrialized manufacture together with much lowered production cost. Interestingly enough, the synergistic effects of montmorillonite with other inorganic particulates was observed for the first time here.

X‐ray diffraction patterns of pristine MMT and nylon 6/MMT composites with grouped intercalation agents.     

Reactive blending approach to modify spin‐coated epoxy film: Part I. Synthesis and characterization of star‐shaped poly(ϵ‐caprolactone)

To effectively modify the properties of an epoxy, branched oligomers were synthesized from ?‐caprolactone (CL) and end‐functionalized to realize network precursors that can be reactively blended with the epoxy. The ring‐opening polymerization (ROP) of the CL in the presence of polyglycerol (PGL) initiator (3.9 and 9.1 mol %) and Sn(II) 2‐ethylhexanoate catalyst yielded oligomers with hydroxyl end‐groups, which were converted to carboxylic acid functionality by reaction with succinic anhydride. The functionalized oligomers had a four‐armed structure and the molecular weight of the oligomers could be controlled by the ratio of CL to PGL in the feed. To achieve an adequately crosslinked network in the reactive blending, a dual‐catalyzed reaction scheme was employed. First the oligomer was incorporated into the epoxy matrix in an imidazole‐catalyzed reaction and then the crosslinking was completed with an acid‐catalyzed ROP of the residual epoxies. Investigations showed that toughened coatings could be prepared from the inherently brittle epoxy through proper choice of the blending ratio of oligomer to epoxy. The blending increased surface hydrophobicity at high concentrations of functionalized oligomer, but did not have an adverse effect on the inherently advantageous endothelial cell spreading. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3677–3688, 2006     

Non‐catalyst synthesis and in vitro drug release property of poly(5,5‐dimethyl‐1,3‐dioxan‐2‐one)‐block‐methoxy poly(ethylene glycol) copolymers

A series of poly(5,5‐dimethyl‐1,3‐dioxan‐2‐one)‐block‐methoxy poly(ethylene glycol) (PDTC‐b‐mPEG) copolymers were synthesized by the ring‐opening polymerization of 5,5‐dimethyl‐1,3‐dioxan‐2‐one (DTC) in bulk, using methoxy poly(ethylene glycol) (mPEG) as initiator without adding any catalysts. The resulting copolymers were characterized by Fourier transform infrared spectra, ¹H NMR and gel permeation chromatography. The influences of some factors such as the DTC/mPEG molar feed ratio, reaction time and reaction temperature on the copolymerization were investigated. The experimental results showed that mPEG could effectively initiate the ring‐opening polymerization of DTC in the absence of catalyst, and that the copolymerization conditions had a significant effect on the molecular weight of PDTC‐b‐mPEG copolymer. In vitro drug release study demonstrated that the amount of indomethacin released from PDTC‐b‐mPEG copolymer decreased with increase in the DTC content in the copolymer. © 2013 Society of Chemical Industry