In situ formation and compounding of polyamide 12 by reactive extrusion

The anionic polymerization of lauryllactam was initiated at 270°C using sodium hydride as an initiator and N,N′‐ethylene‐bisstearamide (EBS) as an activator (NaH:EBS molar ratio of 2). Polymerization occurred in less than 2 min and was successfully performed in an internal mixer and a twin‐screw extruder with corotating intermeshing screws (Werner & Pfleiderer ZSK 25). The content of residual monomer, as determined by thermogravimetric analysis, was lower than 0.5 wt %. Molecular weight, as measured by size exclusion chromatography, was governed by the lauryllactam:NaH molar ratio calculated on a M_n of 25 kg/mol at a constant NaH:EBS molar ratio of 2. Blends were prepared in situ by polymerization of lauryllactam solutions of various polymers. When poly(ethylene‐co‐butylacrylate) (Lotryl®; Atofina) was dissolved in lauryllactam, rubber‐toughened polyamide 12 blends were obtained. Mechanical properties of the injection‐molded polymers were examined by stress–strain as well as notched Charpy impact tests at different temperatures. Blend morphologies were imaged by scanning electron microscopy (SEM). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 344–351, 2003     

Compatibilization of polyethylene/polyamide 6 blends with oxazoline‐functionalized polyethylene and styrene ethylene/butylene styrene copolymer (SEBS)

Study was made of the compatibilization of polyethylene/polyamide 6 (PE/PA6) blends with a ricinoloxazoline maleinate grafted polyethylene and styrene ethylene/butylene styrene copolymer. The blends were prepared in a twin‐screw midiextruder, and the specimens for mechanical tests were injection molded with a mini‐injection molding machine. The effect of compatibilizing on the mechanical properties and the morphology of the blends was studied. The toughness and ductility of the blends were substantially improved as a result of the compatibilization. Simultaneously, the strength and stiffness were slightly reduced. Morphological studies showed that the particle size was reduced and the adhesion of the dispersed phase to the matrix was improved by the compatibilization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1443–1450, 1999     

In situ compatibilization of polypropylene/polystyrene blend by controlled degradation and reactive extrusion

In situ compatibilization of polypropylene (PP) and polystyrene (PS) was achieved by combinative application of tetraethyl thiuram disulfide (TETD) as degradation inhibitor and di‐tert‐butyl peroxide as degradation initiator in the process of reactive extrusion. The PP/PS blends obtained were systematically investigated by rheological measurement, scanning electron microscopy, and differential scanning calorimetry. The results indicate that peroxide‐induced degradation of PP can be effectively depressed by adding TETD, which may favor the formation of PP‐g‐PS copolymer during melt processing. The PP‐g‐PS copolymer formed may act as an in situ compatibilizer for PP/PS blends, and subsequently decreases the size of dispersed PS phase and changes both rheological and thermal properties of the blends. Based on the present experimental results, the mechanisms for the controlled degradation of PP and in situ formation of PP‐g‐PS copolymer in the PP/PS blends have been proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure and properties of polyamide 6 blends with low‐density polyethylene grafted by itaconic acid and with neutralized carboxyl groups

A comparative study of the structure and properties of two‐phase blends of polyamide 6 (PA6) and low‐density polyethylene (LDPE) modified in the course of reactive extrusion, by grafting of itaconic acid (IA) without neutralization of carboxyl groups (LDPE‐g‐IA) and with neutralized carboxyl groups (LDPE‐g‐IA^?M⁺) was carried out. It was shown that 30 wt % of LDPE‐g‐IA^?M⁺ introduced to PA6 resulted in blends of higher Charpy impact strength compared with that of PA6/LDPE‐g‐IA blends. The maximum increase was achieved when Mg(OH)₂ was used as a neutralizing agent. The blend morphology has a two‐phase structure with blurred interphases because of increased adhesion between the phases. The neutralization of carboxyl groups in grafted IA did not lead to two‐phase morphology of blends, which had a negative influence on the mechanical properties. It is believed that the differences in the impact strength were caused by the influence of the added neutralizing agents on the structure of interphases, which depends on both the interfaces adhesion and structural effects resulting from the nucleating behavior of the neutralizing agent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1702–1708, 2004     

反应挤出就地增容HDPE/PS合金

在单螺杆挤出机上,利用路易斯酸实现了大分子间的Friedel—Crafts烷基化反应。考察了不同催化剂体系、催化剂用量及工艺条件对合金性能的影响。结果显示：对于质量比为70．0：30．0的高密度聚乙烯／聚苯乙烯合金体系,通过反应挤出,可以就地生成接枝共聚物;苯乙烯单体的加入有利于接枝物的形成;加入0．8份AlCl3、0．5份苯乙烯单体,控制合适的螺杆温度以及螺杆转速为60r／min时,合金的综合性能较好。     

A novel approach to the preparation of thermoplastic polyurethane elastomer and polyamide 6 blends by in situ anionic ring‐opening polymerization of ε‐caprolactam

Blends of thermoplastic polyether‐based urethane elastomer (TPEU) and monomer casting polyamide 6 (MCPA6) were prepared using ε‐caprolactam as reactive solvent, with caprolactam sodium as a catalyst in the presence of TPEU, with TPEU content varying from 2.5% to 10% by weight. In situ anionic ring‐opening polymerization and in situ compatibilization to prepare TPEU/MCPA6 blends were carried out in one step. The TPEU chains, which underwent thermal dissociation in amine solvents to bear isocyanate groups, acted as macroactivator to initiate MCPA6 chain growth from the TPEU chains and form graft copolymers of TPEU‐co‐MCPA6 to improve compatibility between TPEU and MCPA6. The structure and thermal properties were characterized by means of Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, differential scanning calorimetry and scanning electron microscopy. Copyright © 2006 Society of Chemical Industry     

In situ synthesis of bone‐like hydroxyapatite/polyamide 6 nanocomposites

BACKGROUND: Polymer/hydroxyapatite (HA) nanocomposites have emerged in recent years as a new class of biomaterials that can be used as artificial bone. Compared to pure HA or HA‐based bioceramics, and metallic implants, they exhibit good plasticity, improved toughness and good mechanical compatibility with natural bone. Compared to their microcomposite counterparts and the pristine polymer matrix, they show increased tensile strength and modulus, and enhanced bioactivity. RESULTS: In this study, polyamide 6 (PA6)/nanoscale HA (n‐HA) nanocomposites were prepared via in situ hydrolytic ring‐opening polymerization of ε‐caprolactam in the presence of newly synthesized n‐HA aqueous slurry. The synthesized n‐HA, which is similar to bone apatite in chemical composition, microscopic morphology and phase composition, dispersed uniformly in the composites even if its loading was up to 60 wt%. The PA6/n‐HA composites show a similarity to natural bone in chemical composition to a certain extent. Mechanical tests show that the composites are reinforced considerably by the incorporation of needle‐like n‐HA, and the composites have mechanical properties near to those of natural bone. CONCLUSION: The PA6/n‐HA nanocomposite with high n‐HA content shows a similarity to natural bone in terms of chemistry and mechanical properties. This makes it a possible candidate for biomaterials suitable for bone repair or fixation. Copyright © 2008 Society of Chemical Industry     

Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends

Polyamide and polypropylene (PP) are two important classes of commercial polymers; however, their direct mixing leads to incompatible blends with poor properties. Polypropylene functionalized with glycidyl methacrylate (PP‐GMA) was used as a compatibilizer in blends of PP and nylon 6, because of the possible reaction of ? NH₂ and ? COOH groups with the epoxide group of GMA. Two types of nylon 6 with different ratios between ? NH₂ and ? COOH groups were used. The one with higher concentration of ? COOH groups was less compatible with PP in a binary blend. When PP‐GMA was used as a compatibilizer, a better dispersion of nylon in the PP matrix was obtained together with better mechanical properties for both nylons used in this work. © 2001 Society of Chemical Industry     

Preparation and characterization of flame‐retardant melamine cyanurate/polyamide 6 nanocomposites by in situ polymerization

This article focuses on an improved method, i.e., improved in situ polymerization of ε‐caprolactam in the presence of melamine derivatives to prepare flame‐retardant melamine cyanurate/polyamide 6 (MCA/PA6) nanocomposites. The chemical structures of these synthetic flame retardant composites are characterized by Fourier‐transform infrared spectroscopy and X‐ray diffraction. Morphologies, mechanical properties, and thermal properties also are investigated by the use of transmission electron microscopy, mechanical testing apparatus, differential scanning calorimetry, and thermogravimetric analysis, respectively. Through transmission electron microscopy photographs, it can be found that the in situ‐formed MCA nanoparticles with diametric size of less than 50 nm are nanoscaled, highly uniformly dispersed in the PA6 matrix. These nanocomposites, which have good mechanical properties, can reach UL‐94 V‐0 rating at 1.6‐mm thickness even at a relatively low MCA loading level. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of homogeneously dispersed polyamide 6/MWNTs nanocomposites via simultaneous in situ anionic ring‐opening polymerization and compatibilization

Toluene 2, 4‐diisocyanate (TDI) functionalized multiwalled carbon nanotubes (MWNTs‐NCO) were used to prepare monomer casting polyamide 6 (MCPA6)/MWNTs nanocomposites via in situ anionic ring‐opening polymerization (AROP). Isocyanate groups of MWNTs‐NCO could serve as AROP activators of ?‐caprolactam (CL) in the in situ polymerization. Fourier transform infrared (FTIR) showed that a graft copolymer of PA6 and MWNTs was formed in the in situ polymerization. MWNTs‐PA6 covalent bonds of the graft copolymer constituted a strong type of interfacial interaction in the nanocomposites and increased the compatibility of MWNTs and MCPA6 matrix. The nanocomposites were characterized for the morphology, mechanical, crystallization, and thermal properties through field emission transmission electron microscopy (FETEM), tensile testing, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). FETEM analysis showed that MWNTs were homogeneously dispersed in MCPA6 matrix. The initial tensile strengths and tensile modulus of the nanocomposite with 1.5 wt % loading of MWNTs were enhanced by about 16 and 13%, respectively, compared with the corresponding values for neat MCPA6. DSC analysis indicated that the crystallization temperature of the nanocomposites was increased by 8°C by adding 1.5 wt % MWNTs compared with pure MCPA6. Besides, it was found that the thermal stability of MCPA6 was improved by the addition of the MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of zinc oxide addition on the compatibilization efficiency of maleic anhydride grafted high‐density polyethylene compatibilizer for high‐density polyethylene/polyamide 6 blends

A high‐density polyethylene with grafted maleic anhydride units has been investigated as a compatibilizer for high‐density polyethylene with polyamide 6. The material acts as an effective compatibilizer, causing a marked reduction in dispersed phase size as well as an increase in tensile strength and toughness. Compatibilizer also affects the glass‐transition temperature, crystallization kinetics, and amount of crystalline material for certain blend compositions. The addition of zinc cations, which are effective in increasing ethylene‐acid copolymer compatibilizer performance in low‐density polyethylene/polyamide blends, has little, if any, effect on compatibilizer performance in these high‐density polyethylene/polyamide blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3871–3881, 2007     

Kinetics of the in situ polymerization and in situ compatibilization of poly(propylene) and polyamide 6 blends

In previous articles, we reported on a novel reactive extrusion process to obtain a compatibilized blend of polymer A and polymer B. It consisted in polymerizing the monomer of polymer A in the presence of polymer B. A fraction of the latter contained initiating sites from which the polymerization of monomer A took place. As such, both polymer A and a graft copolymer of polymer A and polymer B were formed in the process. That process was called in situ polymerization and in situ compatibilization of polymer blends. Its feasibility was illustrated for in situ polymerized and in situ compatibilized poly(propylene) and polyamide 6 (PP/PA6) blends. The latter were prepared by activated anionic polymerization of ?‐caprolactam (CL) in the presence of PP in a batch mixer and a twin‐screw extruder, respectively. A fraction of the PP contained isocyanate groups from which PA6 grafts were formed. Sodium caprolactam (NaCL) was used as the catalyst and a diisocyanate compound was used as the activator. In this study, we report on the effects of various parameters on the kinetics of the anionic polymerization of CL in the presence of PP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1498–1504, 2004     

Effect of the compatibilization of linear low‐density polyethylene‐g‐acrylic acid on the morphology and mechanical properties of poly(butylene terephthalate)/linear low‐density polyethylene blends

A poly(butylene terephthalate) (PBT)/linear low‐density polyethylene (LLDPE) alloy was prepared with a reactive extrusion method. For improved compatibility of the blending system, LLDPE grafted with acrylic acid (LLDPE‐g‐AA) by radiation was adopted in place of plain LLDPE. The toughness and extensibility of the PBT/LLDPE‐g‐AA blends, as characterized by the impact strengths and elongations at break, were much improved in comparison with the toughness and extensibility of the PBT/LLDPE blends at the same compositions. However, there was not much difference in their tensile (or flexural) strengths and moduli. Scanning electron microscopy photographs showed that the domains of PBT/LLDPE‐g‐AA were much smaller and their dispersions were more homogeneous than the domains and dispersions of the PBT/LLDPE blends. Compared with the related values of the PBT/LLDPE blends, the contents and melting temperatures of the usual spherulites of PBT in PBT/LLDPE‐g‐AA decreased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1059–1066, 2002; DOI 10.1002/app.10399     

Reactive compatibilization of the polyamide 6/poly(phenylene oxide) blend by means of styrene–maleic anhydride copolymer

The compatibilization of the polymer blend polyamide 6/poly(phenylene oxide) (PA-6/PPO) system has been studied using the reactive random copolymer styrene–maleic anhydride (SMA) as a compatibilizer precursor. SMA is miscible with PPO when the MA content of SMA is not higher than 8 wt %. The anhydride groups of SMA react with the amino end groups of PA-6 during melt blending to form a graft copolymer at the interface with a compatibilizing effect as a result. Two different blending procedures were compared to each other and the compatibilizing effect of the added SMA was evaluated for a matrix/dispersed particle type of morphology. The effect of the different material parameters such as the functionality of SMA (wt % MA in SMA) and the molecular weight of PA-6, and blending parameters such as the extrusion time was analyzed with respect to the blend phase morphology. Finally, the amount of reacted MA groups in the blends PA-6/(PPO/SMA) was determined with FTIR after the use of an extraction method to remove the PA-6 matrix phase. The comparison between the morphological data (particle size reduction of the dispersed PPO/SMA phase) and the FTIR data (amount of reacted MA groups) of the blends considered, turned out to be very logical. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 889–898, 1999     

Numerical simulation of reactive extrusion processes of PA6

To analyze the complicated relationships among the variables during the reactive extrusion process of polyamide 6 (PA6), and then control the chemical reaction and the material structures, the process of continuous polymerization of caprolactam into PA6 in a closely intermeshing co‐rotating twin screw extruder was simulated by means of the finite volume method, and the influences of three key processing parameters on the reactive extrusion process were discussed. The simulated results of an example were in good agreement with the experimental results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2331–2336, 2007     

Novel Polyamide 6/Polystyrene In Situ Microfibrillar Blends Prepared by Anionic Polymerization of ε‐Caprolactam via Reactive Extrusion

In this study, polyamide 6/polystyrene in situ microfibrillar blends are prepared via anionic polymerization of ε‐caprolactam in a twin screw extruder. Scanning electron microscope analysis reveals that microfibrillated PA6 dispersed phase, which is continuous and preferentially oriented parallel to the extrusion direction, is in situ formed within polystyrene (PS) matrix during reactive extrusion at the content PS equal to 30 and 40 wt%. Mechanical properties analysis shows that the yield strength and elongation at break of PA6/PS (70/30 and 60/40) microfibrillar blends are remarkably increased with respect to those of pure PS. Also, the in situ fibrillation mechanisms are investigated by the analysis of morphological evolution. This work demonstrates a facile and efficient route to fabricate the microfibrillar blends with relatively high contents of polymer microfibrils.

     

Comparison of carboxylated and maleated polypropylene as reactive compatibilizers in polypropylene/polyamide‐6,6 blends

Using reactive extrusion, polypropylene is functionalized with maleic anhydride and compared on an equimolar basis to polypropylene that is functionalized with an asymmetric, carboxylic acid containing peroxide. The grafting efficiency for the asymmetric peroxide is double that obtained for the maleic anhydride system. Moreover, the asymmetric peroxide yields a functionalized material with minimal molecular weight degradation and desirable mechanical properties, relative to maleic anhydride‐grafted polypropylene. In compatibilized blends of polypropylene and nylon 6,6, the polypropylene that was functionalized with the asymmetric peroxide is found to be an improved compatibilizer compared to that of maleic anhydride‐grafted polypropylene. The differences in mechanical properties of the two different functionalized polypropylene materials and their respective blends are rationalized on the basis of the grafting efficiency, molecular weight degradation during reactive extrusion, and effect of free functional species on the ability to form graft copolymers in compatibilized blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2398–2407, 2001     

Effects of olefin‐based compatibilizers on the morphology,thermal and mechanical properties of ABS/polyamide‐6 blends

In this study, commercially available epoxidized and maleated olefinic copolymers, EMA‐GMA (ethylene‐methyl acrylate‐glycidyl methacrylate) and EnBACO‐MAH (ethylene‐n butyl acrylate‐carbon monoxide‐maleic anhydride), were used at 0, 5, and 10% by weight to compatibilize the blend composed of ABS (acrylonitrile‐butadiene‐styrene) terpolymer and PA6 (polyamide 6). Compatibilizing performance of these two olefinic polymers was investigated from blend morphologies, thermal and mechanical properties as a function of blend composition, and compatibilizer loading level. Scanning electron microscopy (SEM) studies showed that incorporation of compatibilizer resulted in a fine morphology with reduced dispersed particle diameter at the presence of 5% compatibilizer. The crystallization behavior of PA6 phase in the blends was explored for selected blend compositions by differential scanning calorimetry (DSC). At high compatibilizer level a decrease in the degree of crystallization was observed. In 10% compatibilizer containing blends, formation of γ‐crystals was observed contrary to other compatibilizer compositions. The behavior of the compatibilized blend system in tensile testing showed the negative effect of using excess compatibilizer. Different trends in yield strengths and strain at break values were observed depending on compatibilizer type, loading level, and blend composition. With 5% EnBACO‐MAH, the blend toughness was observed to be the highest at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 926–935, 2007     

Reactive extrusion for the synthesis of nylon 12 and maleated low‐density polyethylene blends via the anionic ring‐opening polymerization of lauryllactam

Nylon 12 was successfully synthesized in a twin‐screw extruder via the anionic ring‐opening polymerization of lauryllactam (LL). Maleated low‐density polyethylene (LDPE–MAH) was added to improve the mechanical properties of nylon 12. The in situ blends of nylon 12 and LDPE–MAH were characterized by mechanical testing and scanning electron microscopy. With increasing LDPE–MAH content, the tensile strength and flexural strength decreased, whereas the blend had improved impact strength and achieved supertoughness when the content of LDPE–MAH was 30 wt %. In the in situ formed low‐density polyethylene‐g‐PA12 copolymer, the domain of the LDPE–MAH phase was finely dispersed in the nylon 12 matrix. The good interface between the two phases demonstrated that LDPE–MAH could be used as a macromolecular activator to induce the polymerization of LL. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

In situ compatibilization of polystyrene and polyurethane blends by using poly(styrene-co-maleic anhydride) as reactive compatibilizer

Blends of polystyrene (PS) and polyurethane (PU) elastomer were obtained by melt mixing, using poly(styrene-co-maleic anhydride) (SMA) containing 7 wt % of maleic anhydride groups as a reactive compatibilizer. Polyurethanes containing polyester flexible segments, PU-es, and polyether flexible segments, PU-et, were used. These polyurethanes were crosslinked with dicumyl peroxide or sulfur to improve their mechanical properties. The anhydride groups of SMA can react with the PU groups and form an in situ graft copolymer at the interface of the blends during their preparation. The rheological behavior was accompanied by torque versus time curves and an increase in the torque during the melt mixing was observed for all the reactive blends, indicating the occurrence of a reaction. Solubility tests, gel permeation chromatography, and scanning electronic microscopy confirmed the formation of a graft copolymer generated in situ during the melt blending. These results also indicate that this graft copolymer contains C C bond between SMA and PU chains. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2514–2524, 2001