High performance polyamide 6 composites prepared by reactive extrusion

To improve the properties of polyamide 6 (PA6) composites, a series of modified PA6 composites was prepared by reaction extrusion. An amorphous PA6 was first obtained by the complexing reaction of Li⁺ in lithium chloride with amino groups, and then epoxy resins, nano‐SiO₂ as well as POE‐g‐MAH were in turn added into the PA6/LiCl system. The effect of different additives on the crystallization behavior and mechanical properties of PA6 composites was well‐studied by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and mechanical properties tests. The results demonstrated that PA6 was amorphous at 6 phr lithium chloride and a network structure was formed in PA6 matrix in the presence of epoxy resins, thus the mechanical properties of composites greatly were enhanced. However too many nano‐SiO₂ particles might impair the tensile strength of PA6 composites. Additionally, a PA6 composite with excellent properties was obtained in the presence of POE‐g‐MAH due to the crystal form change in PA6 matrix and the strong interaction between PA6 and POE‐g‐MAH. POLYM. COMPOS., 35:985–992, 2014. © 2013 Society of Plastics Engineers     

Characterization of low molecular weight carboxyl-terminated polyamides obtained by reactive extrusion of polyamide 6 with trimellitic anhydride

Reactive extrusion has been applied as a very effective and fast process for controlled chemical degradation of a commercial polyamide 6 with trimellitic anhydride in the melt. A reaction mechanism based mainly on the amide/anhydride reaction has been discussed and confirmed by measurements of the solution viscosity, end group analysis, SEC, NMR, and IR spectroscopy. The systematic loss of molecular weight of the polyamides resulting from PA chain repture and the formation of imide linkages and carboxyl end groups were investigated. The theoretical values of molecular weight and end group concentration of the obtained oligoamides predicted by the reaction mechanism are in good agreement with the experimental ones. © 1996 John Wiley & Sons, Inc.     

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     

聚酰胺6-聚氨酯嵌段共聚物的合成及表征

以聚醚三元醇、二苯甲烷二异氰酸酯以及己内酰胺为单体,在碱性催化剂条件下,通过单体浇铸工艺合成聚酰胺6-聚氨酯(PA6-PU)嵌段共聚物.采用傅里叶变换红外光谱仪、差示扫描量热仪表征其结构与性能.结果表明,PA 6-PU嵌段共聚物的熔点下降,且具有两相结构.力学性能分析显示,PU组分的嵌入使共聚物的常温冲击强度南7.20 kJ/m2提高到42.76 kJ/m2,低温(-50℃)冲击强度由4.20 kJ/m2提高到15.14 kJ/m2.     

双螺杆反应挤出合成PA6/蒙脱土纳米纺丝切片

采用己内酰胺作单体,通过双螺杆反应挤出的方法合成了PA6/蒙脱土纳米纺丝切片。设计了合理的螺杆组合方式,设定了双螺杆筒体温度,选择适当的螺杆转速,所得到的切片相对分子质量适当,分布较小,适宜纺制纤维。采用WAXD、DSC对切片进行分析表明,单体在蒙脱土硅酸盐片层中插层聚合。用该切片纺制成的纤维强度为5.35cN/dtex,伸长28.1％,模量52.42cN/dtex,比纯PA6有所提高。     

反应挤出法聚1-丁烯热塑性弹性体的合成及表征

采用负载钛催化体系[TiCl4/MgCl2-Al(i-Bu)3],在反应挤出机上合成了聚1-丁烯热塑性弹性体(PB-TPE),与聚合釜本体聚合法合成的PB-TPE的力学性能、热性能、元素组成以及催化剂的催化效率进行了比较。结果表明,利用反应挤出法合成PB-TPE是可行的;与聚合釜本体聚合法合成的PB-TPE相比,其力学性能还不理想,在热性能和元素组成上也有一定差异,且催化剂的催化效率较低。     

反应挤出合成S/B嵌段共聚物的研究

以同向紧啮合双螺杆挤出机为反应器、有机锂为引发剂,采用混合单体加料方式,本体法一步合成了苯乙烯-丁二烯嵌段共聚物。^1H-NMR图谱表明该丁苯共聚物的结构以嵌段为主,无规链段为辅。其力学性能则体现出受丁二烯质量分数的影响。     

用反应挤出法合成苯乙烯-异戊二烯嵌段共聚物

以同向紧密啮合双螺杆挤出机为反应器,有机锂为引发剂,采用混合单体加料方式,本体法一步合成了苯乙烯-异戊二烯嵌段共聚物。核磁共振谱图和透射电子显微照片均表明该共聚物具有纳米级多嵌段结构,其物理机械性能受异戊二烯质量分数的影响。     

Mechanical behaviour modelling of a nanostructured polyamide blends obtained by reactive extrusion process

The aim of the present work was to study the effect of the composition and operating conditions on the properties of nanostructured polyamide blends obtained by reactive extrusion. The ultimate objective consisted in optimizing the high impact energy of these materials using an experimental design based on the D-optimality and rotatability criteria. A thermodynamic approach of relaxation phenomena called distribution of nonlinear relaxations (DNLR) was proposed to account for the nonlinear mechanical behaviour of the obtained polyamide blends for different compositions and extrusion conditions. Five parameters of the DNLR law have thus been modelled as functions of these operating conditions using quadratic polynomial relations.The accuracy of this modelling was evaluated by establishing some comparison between the experimental data and the predictive results and by performing statistical tests.     

Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent. Part I: Extrusion parameters analysis

Condensation reaction between a carboxyl terminated polyamide 12 (CTPA) (Mn = 2000 g mol^?1) and a dioxazoline [2,2′‐(1,3‐phenylene)‐bis(2‐oxazoline)] (OO) was achieved by reactive extrusion. Extrusion parameters effects on the process were analyzed through residence time distribution (RTD) and conversion distribution (CD) evolutions. RTD was measured using ultraviolet and ultrasonic detectable tracers. RTD measured along the extruder screws showed a decrease of the dimensionless variance (σ) with the reaction progress. Comparing measured molar masses and dispersity with those calculated using CD, competition between condensation and chain scission was detected. Effects of barrel temperature, screw profile, rotation speed and viscous dissipation on the reactive system evolution were analyzed and used for the process optimization. It was shown that a polyester amide with a Dp _n 12 can be obtained using this dioxazoline coupling agent by reactive extrusion.     

Influence of extrusion temperature on thermal properties of polyamide 6/MMT nanocomposites

Abstract

The effect of processing temperature on the melt flow and thermal behaviour of polyamide 6 (PA6)/organophillic montmorillonite (MMT) nanocomposite was investigated. PA6/MMT nanocomposites were prepared by melt extrusion at five different processing temperatures. Neat PA6 was also extruded as a reference. The composites were characterised by melt flow measurement, differential scanning calorimetry, dynamic mechanical analysis and X-ray diffraction.     

Synthesis and characterization of polyamide powders for sorption of reactive dyes from aqueous solutions

Polyamide (PA) fine powders or granules, obtained by anionic solution/suspension polymerization of lactams, were used for the sorption of reactive dye Brilliant Red HE‐3B from aqueous solutions. They provided a relatively large surface area and porosity that allowed an increased sorption rate. The visible molecular absorption spectroscopy was used to evaluate the performance of the investigated systems. Under the same conditions, the sorption capacity of polyamide particles decreases in the following manner: PA6‐powders > PA12‐powders > PA4‐granules. The effect of pH, initial dye concentration, temperature, and sorption duration on dye removal was studied for the PA6‐powder/reactive dye system. The equilibrium sorption isotherms have been analyzed by the linear, Freundlich, and Langmuir models. The data conform to a Langmuir isotherm and a pseudosecond order kinetic model, respectively. In addition, the apparent thermodynamic parameters were calculated and the obtained values support the conclusion that the reactive dye molecules are adsorbed onto PA‐powders by an entropy‐driven, endothermic process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Blends of polyamide 6 with bisphenol-A polycarbonate. I. Thermal properties and compatibility aspects

Blends of polyamide 6 (PA6) and polycarbonate (PC) have been investigated, over a full range of composition, to check interactions between them. SEM observations show that the mixtures are characterized by domains of clearly segregated homophases and voids between the two polymers. DSC and DMTA data indicate the presence of two T_g' s, corresponding to two separate phases, with the T_g of the PC phase decreasing on increasing the PA6 amount. Moreover, the crystallization kinetics of PA6 is slightly showed down by the PC. Chemical reactions between the two polymers are supposed to give rise to low molar mass compounds, as shown by GPC; these species plasticize the PC and partially dissolve into the molten polyamide, causing decrease of PC T_g and reduction of overall crystallization rate of PA6. Apparent influence of PC on melting temperature and enthalpy of PA6 is also discussed.     

Molecular characterization and rheological properties of modified poly(ethylene terephthalate) obtained by reactive extrusion

The use of a tetrafunctional epoxy‐based additive to modify the molecular structure of poly(ethylene terephthalate) (PET) was investigated with the aim of producing PET foams by an extrusion process. The molecular structure analysis and shear and elongation rheological characterization showed that branched PET is obtained for 0.2, 0.3 and 0.4 wt% of a tetrafunctional epoxy additive. Gel permeation chromatography (GPC) analysis led to the conclusion that a randomly branched structure is obtained, the structure being independent of the modifier concentration. The evolution of shear and extensional behavior as a function of molecular weight (M_w), degree of branching, and molecular weight distribution (MWD) were studied, and it is shown that an increase in the degree of branching and M_w and the broadening of the MWD induce an increase in Newtonian viscosity, relaxation time, flow activation energy and transient extensional viscosity, while the shear thinning onset and the Hencky strain at the fiber break decrease markedly.     

Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent. Part II: Effects of extrusion conditions

Condensation reactions between a carboxyl terminated polyamide 12 and a dioxazoline carried out by reactive extrusion have been characterized in the first part of this study. In the present paper, we focus on the influence of extrusion conditions on reaction progress. Influences of screw profile, screw speed, barrel temperature and feed rate have been established. The use of a flow computation software permitted confirmation of the importance of thermal and mechanical degradations in the condensation process.     

Synthesis and properties of fluorescent light‐emitting polyamide hybrids with reactive nanosilica by epoxide functionalization

A series of poly(carbazole‐quinoxaline‐amide)s (PCQAs) containing phenyl and long alkyl chain as pendants was synthesized from polycondensation between a new diamine with a synthesized and several commercial dicarboxylic acids using Yamazaki's method. PCQAs had inherent viscosities and weight average molecular weights ( ) in the range of 0.48–0.62 dL g^?1 and 51,600–58,500 g mol^?1, respectively. These luminescent polymers are readily soluble in a variety of organic solvents and formed low‐colored and tough thin films. In this study, silane modified SiO₂ (mSiO₂) nanoparticles were prepared, characterized and used with PCQAs in preparation of nanocomposites via solution blending method. The interfacial interaction strength between mSiO₂ and the polymer–matrix enhanced thermal stability (T_10%, from 463°C to 500°C) and mechanical strength (from 100 MPa to 150 MPa) for composite containing 30 wt % mSiO₂ in comparison with the pure polyamide. These materials showed good ability for extraction–elimination of metal ions such as Cr⁶⁺, Cr³⁺, Co²⁺, Zn²⁺, Pb²⁺, Cd²⁺, and Hg²⁺ from aqueous solutions either individually or in the mixture at various pH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40219.     

Grafting of polyethylenes by reactive extrusion. I. Influence on the molecular structure

Grafting of polyethylenes is an important method used in the modification of polyolefins with functional groups. Lately, the use of extruders as polymerization reactors has increased considerably. However, knowledge of the details of the reaction in the extruder is still limited. In this investigation, the grafting of various commercial polyethylenes, high-density polyethylenes (HDPEs), and linear low-density polyethylenes (LLDPEs) with diethyl maleate (DEM) was carried out in two corotating twin-screw extruders with different screw configurations and extrusion conditions. Two initiators at different concentrations were used. It was found that when the initiator level was raised in the LLDPEs the grafting degree increased and the molecular weight distribution of the grafted LLDPE2 did not show appreciable differences when they were compared to the virgin resin. On the other hand, the terminal vinyl group concentrations decreased at the expense of increasing the trans unsaturation concentrations. This last result is consistent with the formation of long-chain branching. Additionally, the weight-average molecular weight of grafted high-density polyethylene (HDPE1-g-DEM) decreased. The grafting efficiencies were consistent with the attained residence times and also with the kinetics of the decomposition of the peroxides. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 161–176, 1998     

Improving the flame-retardant property of bottle-grade PET foam made by reactive foam extrusion

Upcycling of low intrinsic viscosity (IV) poly(ethylene terephthalate) (PET) grades, such as bottle- or recycled grades, by a reactive foam extrusion process, provides an appropriate alternative to high pricing, high IV grades commonly used for foaming applications. However, the drawback of bottle-grade PET foams is its flame retardant (FR) performance. In this study, pyromellitic dianhydride was used as a chain extender to foam bottle-grade PET. The influence of different FRs, containing halogenated (HFR) and four different phosphorous-based types, on the processability and final foam properties was investigated. HFR showed better processability to achieve proper foams with fine morphology compared to P-based FRs, where the FR content was adjusted between 2 and 5 wt%. However, HFR exhibited lower FR performance by cone calorimeter testing compared to the P-based FRs and the commercial reference foam Kerdyn. Nonetheless, all of the FRs can only improve the time to ignition of the neat PET foams while the other values depend on the specific type of FR. In addition, all FR foams have improved mechanical properties more than twice in comparison to the neat PET foam.     

Grafting of polyethylenes by reactive extrusion. II. Influence on rheological and thermal properties

In this article, the effects of the grafting degree and the processing conditions employed to prepare LLDPEs-g-DEM and HDPEs-g-DEM via reactive extrusion on their rheological and thermal properties were studied. The rheological properties of the virgin samples of LLDPEs, HDPEs, and their functionalized products were determined using capillary and dynamic rheometry. The thermal behavior of the virgin materials and their grafted products was examined by differential scanning calorimetry (DSC). It was found that the rheological properties are more sensitive than are the molecular structure characteristics to the changes produced by the grafting reactions with DEM, under the employed experimental conditions. There is an increase in the dynamic viscosity at low frequencies, in the storage modulus, and in the shear-thinning behavior when the grafting degree increases. The crossover between G″ and G′ moves to lower frequencies and the relaxation time spectrum functions are broader in the grafted materials. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2549–2567, 1999     

纺丝级尼龙6的反应挤出研究

利用阴离子开环聚合反应在双螺杆上快速制得了相对分子质量适当 ,相对分子质量分布较低(小于 3) ,单体含量低 (质量分数为 2 .5%～ 2 .8% ) ,流变性能好 ,易于纺丝的纺丝级尼龙 6。介绍了双螺杆反应挤出机的设计原理 ,讨论了催化剂、活化剂、助剂和挤出条件等因素对纺丝级尼龙 6的相对分子质量及其分布、残留单体量等的影响。实验发现 ,催化剂主要起引发反应的作用 ,活化剂则可大大加快反应速度 ,而助剂的加入可有效地提高聚合物的可纺性。