Styrene maleic anhydride and styrene glycidyl methacrylate copolymers as in situ reactive compatibilizers of polystyrene/nylon 6,6 blends

The reactive type copolymers styrene maleic, anhydride (SMA) and styrene glycidyl methacrylate (SG) are used as in situ compatibilizers in polyblends of polystyrene (PS) and nylon 6, 6 (N66). Both copolymers can react with N66 to form copolymers as effective compatibilizers to reduce interfacial tension and increase phase adhesion. However, the toughness of the compatibilized blends is significantly lower than of the corresponding noncompatibilized blends. Only a small fraction of SMA is actually reacted in a typical melt blending, and SG copolymer seems to be more reactive than SMA. The unreacted copolymers are expected to be distributed mostly in the PS phase because of their structural similarity. The reacted copolymers are not exclusively distributed along the interface; some may distribute in both matrices. SMA is known as a very brittle polymer, and the way it is distributed can greatly influence the toughness of the resulting blends. PS is also very brittle relative to N66, and moreover a high amount of SMA in the N66 phase is detrimental since N66 is responsible for the toughness of PS/N66 blends. The better compatibilized blends have the tendency to bring more SMA and reacted SMA into the N66 phase. The relative detrimental effect on the inherent toughness of N66 is much more severe than in case of PS, if they contain the same amount of SMA. This study demonstrates that polyblends with good compatibilizers do not guarantee toughness improvement. The way the compatibilizers affect the inherent properties of the matrix needs also to be taken into consideration.     

Poly(styrene-graft-ethylene oxide) as a compatibilizer in polystyrene/polyamide blends

Polystyrene (PS) blends containing a dispersed phase of either polyamide-6 (PA-6) or polyamide-12 (PA-12) were compatibilized by additions of 1, 3, or 5 wt % poly(styrene-graft-ethylene oxide). The graft copolymers were found to have a stabilizing effect on the domain sizes. Weight average radii of PA-6 domains in compression molded samples were reduced by a factor of 5 with 3 wt % graft copolymer added. The corresponding size reduction for PA-12 domains was by a factor of 3. Also, the domain sizes were more uniformly distributed in blends containing the graft copolymers. Thermal analysis of the blends revealed that compatibilization retarded the PA crystallization, with some PA crystallizing at the PS glass transition. This retarded crystallization is explained as a result of the domain size reduction and by the presence of graft copolymer at the interface. The graft copolymers had a toughening effect on the blends and the impact strength of a PS/PA-12 blend was improved by 65% by adding 3 wt % of graft copolymer. Binary blends of the PA and poly(ethylene oxide) (PEO) were investigated in a separate study to verify miscibility of the graft copolymer side chains and the PA. Hydrogen bonding between PA-6 and PEO was confirmed by IR spectroscopy and partial miscibility was indicated by melting point depressions. © 1995 John Wiley & Sons, Inc.     

Characterization of nylon 6/ABS blends with and without a maleated polybutadiene as compatibilizer

The physical properties of nylon 6/poly(acrylonitrile-butadiene-styrene) terpolymer (ABS) blends using a maleated polybutadiene (denoted PB-g-MA) as compatibilizer were investigated. The morphology results reveal that ABS domain sizes decrease with an increasing compatibilizer content, suggesting the good interaction between the nylon 6 matrix and the ABS dispersed phase. Cooling conditions and compatibilizer contents strongly affect the crystalline structure of nylon 6, as determined from X-ray diffraction and non-isothermal crystallization thermal analyses. The coexistence of α- and predominantly γ-form crystals for the 10 phr compatibilized blends was observed. Isothermal crystallization kinetics suggests that the introduced compatibilizer impeded the growth rate of the crystals, especially for the higher compatibilizer content. The compatibilizer was beneficial in enhancing the thermal stability of the blends.     

Supercritical CO2-assisted synthesis of poly(acrylic acid)/nylon6 and polystyrene/nylon6 blends

Poly(acrylic acid)/nylon6 and polystyrene/nylon6 blends were prepared using supercritical CO₂ as substrate-swelling agent and monomer/initiator carrier. Both supercritical CO₂/nylon6 binary system and SC CO₂/monomer/nylon6 ternary system were studied. Virgin nylon6 and synthesized blends were characterized through differential scanning calorimetry, infrared spectroscopy, and polarizing microscopy. Supercritical CO₂-induced crystallization was found in modified nylon6.     

Carboxylation of polypropylene by reactive extrusion with functionalized peroxides for use as a compatibilizer in polypropylene/polyamide-6,6 blends

Variable quantities of functionalized peroxides bearing carboxylic acid groups were reacted with polypropylene (PP) in a twin-screw extruder. Systematic variations in the molecular structure of the peroxides were found to significantly affect the grafting efficiency of the carboxylic acid group onto the PP backbone, as well as affect the polymer degradation process. This behavior was attributed to the relative reactivities of the different free radicals generated by thermal decomposition of the peroxides. Furthermore, the functionalized polypropylene (f-PP) was investigated as a compatibilizing additive for 80/20 PP/PA-6,6 (polyamide 6,6) blends. With incorporation of the f-PP into the blends, differential scanning calorimetry (DSC) showed an 80°C decrease in the PA-6,6 crystallization temperature. A near linear increase in the impact strength of the blends was observed with f-PP incorporations up to 30% of the PP phase. Moreover, blends containing 30% f-PP demostrated impact properties approaching that of pure PA-6,6.     

Interaction characterization of PA1010/PP blends using PP-g-AA as compatibilizer

The morphology of polyamide 1010/polypropylene blends was found to significantly depend upon the concentration of the compatibilizer[polypropylene-grafted-acrylic acid (PP-g-AA)]. A significant reduction in phase size was observed because of the interaction that existed between the PP-g-AA and polyamide. These interactions have been confirmed by several methods. The tensile mechanical properties and impact behavior of the prepared blends were investigated and correlated with scanning electron microscope (SEM) analysis of the fracture surfaces. It was found that PP-g-AA as the compatibilizer has a profound effect upon the properties of the blends. This behavior is attributed to a series of chemical and physico-chemical interactions taking place between the two components.     

Microstructural investigations of PBT/nylon 6,6 composites

The microstructure of composites made from blends of poly(p-phenylene benzobisthiazole) [PBT] and nylon 6,6 has been investigated with wide-angle X-ray diffraction, selected area electron diffraction, and small-angle X-ray scattering techniques. The composite samples investigated were spun in both fiber and film forms dilute solutions of methane sulfonic acid. The structure of the composites was found to be a microfibrillar network of PBT in a matrix of partially crystalline nylon 6,6. The diameters of the PBT microfibrils were in the range of 30 to 70 Å.     

A study on PVC/LLDPE blends with solid-state-chlorinated polyethylene as compatibilizer

Chlorinated polyethylene (CPE) prepared by solid-state chlorination was used as compatibilizer for poly(vinyl chloride) (PVC)/linear low-density polyethylene (LLDPE) blends. Effects of CPE molecular structure on stress-strain behaviors, dynamic mechanical properties, and morphologies of PVC/LLDPE blends were studied by using SEM, TEM, DMA, and testing mechanical properties. The results showed that the compatibility of PVC/LLDPE blends was improved with the addition of CPE. Also, adhesion strength between the two phases and mechanical properties of the blends were increased. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2535–2541, 1997     

丁腈橡胶增容丁苯橡胶/聚氯乙烯共混体系

采用一系列结合丙烯腈质量分数不同的丁腈橡胶(NBR)作为丁苯橡胶(SBR)／聚氯乙烯(PVC)不相容共混物的增容剂,研究了SBR／PVC／NBR硫化胶的力学性能,并用扫描电子显微镜、傅里叶变换红外光谱仪和动态黏弹仪研究了该硫化胶的形态结构与相容性。结果表明,结合丙烯腈质量分数为20％～26％的NBR是SBR／PVC的优良增容剂,可提高共混物的力学性能,使SBR相和PVC相达到微细均匀化分散,并在两相之间形成了界面层,使得增容效果达到最佳。     

Processing-morphology-property relationships in polyethylene/acrylonitrile copolymer/compatibilizer blends

Effects of blend composition, compatibilizer, and processing conditions on the morphology, rheology, and mechanical properties of the ternary blends are investigated. Introduction of compatibilizer and increasing shear rate lead to a finer particle dispersion. A modification of Wu's equation is utilized to obtain an estimate of the interfacial tension. The results indicate a reduction in interfacial tension upon addition of compatibilizer. Morphological stability of these blends is studied by reprocessing them in an injection molding machine and a twin-screw extruder. The nature of the reprocessing history was found to govern the morphology and the mechanical properties of the blends investigated.     

Preparation and characterization of LDPE/starch blends containing ethylene/vinyl acetate copolymer as compatibilizer

A series of LDPE blends with plasticized (PLST) and granular starch (FILST) were prepared. Ethylene/vinyl acetate (EVA) copolymer was used as a compatibilizer in three different amounts: 10, 25 and 50 wt% based on starch. The blends were studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Second derivative IR spectra showed peak shifts similar to those observed in V-type starch complexes with ethylene/vinyl alcohol copolymers. The possibility for V-type complex formation is supported by the lower biodegradation rates of the blends containing higher amounts of EVA. Mechanical properties of the blends, especially elongation at break, were satisfactory even for blends containing high amounts of starch (20–30 wt%).     

Tensile yield in nylon 6,6

Uniaxial tension tests to, the yield point were performed on poly(hexamethylene adipamide) (nylon 6,6) as a function of temperature from 21 to 200°C at a strain rate of 2 min^?1. At 21 and 60°C, measurements were also made at strain rates from 0.02 to 8 min^?1. Using simple rate theory, reasonable values of activation volume were obtained, but the simple theory is inadequate to determine the activation energy. The yield-strain temperature dependence changes at 160°C as a result of a reversible crystal-crystal transition. Because of this behavior of the yield strain, the yield energy is not a linear function of temperature, as observed for several other polymers.     

Liquid natural rubber (LNR) as a compatibilizer in NR/LLDPE blends

The effects of molecular weight of LNR, as a compatibilizer in NR/LLDPE blends, were studied. Rheological studies and mechanical properties of the blends showed that the molecular weight of LNR played a very important role in determining their performance. The blends that contained 15–25% LNR with an M_w of 4.8 × 10⁵ and an M_n of 1.66 × 10⁵ showed the highest mechanical properties. Outside this range of molecular weight, the compatibilizing property of LNR is no longer effective due to inhomogeneous blends. Improvements in the mechanical properties were in consonance with the increase in gel contents of the blends. The additions of LNR in the blends were able to reduce the interfacial tension; therefore, they improved the interaction between the phases of the blends. The studies also confirmed that, within the concentration range investigated, the LNR solvent did not influence the blend properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1776–1782, 2000     

Functionalized elastomeric compatibilizer in PA 6/PP blends and binary interactions between compatibilizer and polymer

Superior impact properties were obtained when maleic anhydride grafted styrene ethylene/butylene styrene block copolymer (SEBS-g-MAH) was used as a compatibilizer in blends of polyamide 6 (PA 6) and isotactic polypropylene (PP), where polyamide was the majority phase and polypropylene the minority phase. The optimum impact properties were achieved when the weight relation PA:PP was 80:20 and 10 wt% SEBS-g-MAH was added. The blend morphology was systematically investigated. Transmission electron microscopy (TEM) indicated that the compatibilizer forms a cellular structure in the PA phase in addition to acting as an interfacial agent between the two polymer phases. In this cellular-like morphology the compatibilizer appears to form the continuous phase, while polyamide and polypropylene form separate dispersions. In microscopy, PA appeared as a fine dispersion and PP as a coarse dispersion. The mechanical properties indicated that in fact PA, too, is continuous, and the blend can be interpreted as possessing a modified semi-interpenetrating network (IPN) structure with separate secondary dispersion of PP. The coarser PP dispersion plays an essential role in impact modification. Binary blends of the compatibilizer and one blend component were also investigated separately. The same cellular structure was observed in the binary PA/SEBS-g-MAH blends, and SEBS-g-MAH again appeared to form the continuous phase when the elastomer concentration was at least 10 to 20 wt%. By contrast, in PP/SEBS-g-MAH only conventional dispersion of elastomeric SEBS-g-MAH was observed up to 40 wt% elastomer. Impact strength was improved and the elastic modulus was lowered in both PA/SEBS-g-MAH and PP/SEBS-g-MAH blends when the elastomer content was increased. The changes in modulus indicate that the semi-IPN-like structure is formed in the binary PA/SEBS-g-MAH blends as well as in the ternary structure.     

Electrically and thermally conductive nylon 6,6

Increasing the thermal and electrical conductivity of typically insulating polymers, such as nylon 6,6, opens new markets. A thermally conductive resin can be used for heat sink applications. An electrically conductive resin can be used in static dissipative and Electromagnetic Interference/Radio Frequency Interference shielding applications. This research focused on adding various carbon based conductive fillers and a chopped glass fiber to nylon 6,6. These materials were extruded and injection molded into test specimens. Tensile tests as well as in-plane electrical resistivity, in-plane thermal conductivity, and through-plane thermal conductivity tests were conducted. One successful formulation consisted of 10% 3.2 mm chopped E-glass fiber/15% Thermocarb (high quality synthetic powdered graphite)/5% carbon black/70% nylon 6,6 (all % in wt%). For this formulation, the in-plane electrical resistivity was reduced from 10¹⁵ ohm-cm (neat nylon 6,6) to 15 ohm-cm. The through-plane thermal conductivity increased from 0.25 W/mK (neat nylon 6,6) to 0.7 W/mK. The tensile elongation at failure was 1.4%.     

Rheological evaluation of polystyrene/polyethylene blends

The dynamic shear behavior at 200°C of low density polyethylene, LDPE, polystyrene, PS, and their blends was studied. Two series of blends were prepared containing LDPE:PS = 1:2, 2:1 and 17:3; the first series contained 0, the second 5 wt% of the compatibilizing, partially hydro-genated poly(styrene-b-isoprene) di-block copolymer, SEB. From the Casson plot the relative values of apparent yield stress were found to be G′_y > G″_y the addition of SEB decreased both these functions, but the inequality remained valid. After subtracting the yield stress values the frequency relaxation spectrum was computed from the relation G″ = G″(ω). The linear viscoelastic functions determined from the spectrum were found to agree with experimental values within a range of error below 5%. The blends were found to be thermorheologically complex with the time-temperature shift factors depending on both temperature and frequency. A compositional dissymmetry of blend morphology was observed: PS dispersed in LDPE formed spheres, while at corresponding concentration LDPE in PS formed fibers. A difference in surface tension of the two polymers, leading to different spreading coefficients (S_PE/PS≠S_PS/PE), or dissymmetry of the interfacial tension coefficient, could provide a possible explanation.     

Effect of PP-g-MAH compatibilizer content in polypropylene/nylon-6 blends

A method commonly used to induce compatibility between polyamides and polyolefins is by chemical modification of the polyolefins. This concept has been employed to produce compatibilized blend of nylon 6 (N6) and polypropylene copolymer (PPCP) by adding maleic anhydride grafted polypropylene (PP-g-MAH) as a third component. The blends of N6, PPCP and PP-g-MAH were prepared using a twin screw extruder. TEM of the blends revealed better dispersion and reduction in the size of the dispersed phase. In case of N6 rich blends, about 25% increase in tensile strength was observed with just three phb of PP-g-MAH. The maximum impact strength and flexural modulus were observed at around 30% PPCP. The incorporation of PP-g-MAH increased the flexural modulus of N6/PPCP blends significantly.     

Synthesis and characterization of TPO-PLA copolymer and its behavior as compatibilizer for PLA/TPO blends

A thermoplastic polyolefin elastomer-graft-polylactide (TPO-PLA) was prepared by grafting polylactide onto maleic anhydride-functionalized TPO (TPO-MAH) in the presence of 4-dimethylaminopyridine (DMAP). The characterization of the TPO-PLA copolymers was conducted by FT-IR and ¹H NMR. The effects of reaction temperature and concentration of DMAP on the reactivity of graft polymerization were investigated by FT-IR, which revealed that a high reaction temperature and a high DMAP concentration are associated with dramatic depolymerization of PLA and reduction of steric hindrance effect in the graft reaction. A Molau test, SEM observations of cyro-fractured surface morphology and particle size analysis of PLA/TPO blend system demonstrate that this new copolymer, acting as a premade compatibilizer, significantly improved the compatibility of the PLA/TPO blends. As the concentration of TPO-PLA copolymer increased, elongation at break and tensile toughness increased with compatibilizer concentration up to 2.5 wt%, beyond which it declined, but TPO-PLA copolymer did not affect the tensile strength or modulus. The effect of the chemical composition of the TPO-PLA copolymer on the compatibilization efficiency and mechanical properties of the PLA/TPO blends was examined by altering the number of grafting sites and concentration of DMAP, suggesting that DMAP concentration dominated the properties of the ternary blend system. Two compatibilizers, TPO-MAH and TPO-PLA, were used to compatibilize the PLA/TPO blend; the results suggested that TPO-PLA was more efficient in reducing the interfacial tension between the two immiscible polymers and in improving the mechanical properties of PLA/TPO blending specimens.     

Reactive extrusion of polystyrene/polyethylene blends

The feasibility of inducing beneficial changes to polystyrene/polyethylene (PS/PE) blends via reactive extrusion processes is considered. Experiments have been conducted on 50:50 wt.% PS/PE blends that were treated with different levels of dicumyl peroxide and triallyl isocyanurate coupling agent. Both a low molecular weight and a high molecular weight blend series have been investigated. A “more reactive” polystyrene was synthesized by incorporation of a minor amount of ortho-vinylbenzaldehyde. Blends containing this modified polystyrene were subjected to identical processing' conditions on a counter-rotating twin screw extruder. Examination of the tensile properties of the extrusion products suggested that a judicious level of peroxide and coupling agent additives would be beneficial to the ultimate physical properties. The quantity of styrenic phase becoming chemically grafted to the polyethylene matrix was influenced most strongly by the level of the chosen coupling agent. As determined by scanning electron microscopy, the phase morphologies of the tensile test fracture surfaces were strongly dependent upon the reaction extrusion process; those extruded blends that had been exposed to the additive pre-treatment displayed substantially finer microstructure. The enthalpy of fusion of the polyethylene melting endotherm was likewise influenced by both the presence or absence of the additives as well as the molecular weight nature of the blend series.     

Surface plasticisation of nylon 6,6 by water

Tribological studies have been carried out on Nylon 6,6 with particular emphasis placed on the examination of the effect of water on this polymer. An examination of the sliding frictional behaviour of Nylon 6,6 against a steel substrate shows that the friction decreases with increasing load, probably due to the formation of thermally softened interfaces in the contact. After exposure of this polymer to water, dramatic changes to the frictional behaviour of the Nylon are observed; the friction increases with increasing load. From the application of the adhesion model of friction it is postulated that the observed changes are caused by extensive plasticisation of the Nylon and, as a consequence, an increase in the contact area. This proposition is confirmed by the reported scratch hardness data. After treatment with water the scratch friction mechanism changes significantly and a notable reduction in the hardness of Nylon is observed.