Blends of bisphenol-A polycarbonate and acrylic polymers: III. Effect of imide concentration on compatibility (original) (raw)
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Journal of Polymer Science Part B, 1997
An acrylic polymer containing acid and anhydride units, referred to as reactive polyglutarimide (RPGI), has been used to react with PC. The reaction has been previously determined as an acidolysis of the carbonate bond which breaks the PC chain in two parts. One of those two parts remains free while the other one is grafted on the acrylic backbone. We have found that the anhydride units could also react with the carbonate bonds. In this case the PC macromolecule would also be broken in two parts, which would, however, both be grafted on the acrylic backbone. The reaction has been performed in solution in order to keep good contact between the reacting units. The influence of temperature and concentration on the grafting ratio has been studied. The best experimental conditions were determined in order to obtain a grafted copolymer where the acrylic backbone only supports, on the average, one PC side chain through acid reaction or two PC chains through anhydride reaction. Indeed, these two types of reactions could not be isolated. The efficiency of this copolymer as emulsifier has been studied in solution cast blends as well as in melt mixed blends. The copolymer strongly affects the microstructure in solution cast blends where films containing 30 wt % of PC have become transparent. However, the dispersed phase size of solvent cast blends could be highly influenced by the casting conditions related to solvent trapping. In melt mixed samples, the copolymer also reduces significantly the dispersed phase size, but no transparent blends have been observed so far. These results were compared with those given in the literature describing the efficiency of a synthesized copolymer which has a more complicated structure.
Interfacial activity of graft copolymers in blends: effect of homopolymer molecular weight
Polymer, 1992
The effect of varying the homopolymer molecular weight, corresponding to the minor phase, on the interfacial activity of graft copolymers in blends of homopolymers has been investigated. The system studied was polycarbonate/poly(methyl methacrylate) (PMMA) (65/35w/w) blends containing polycarbonate/ PMMA graft copolymers. The molecular weight of the polycarbonate homopolymer was increased from 3.6 to 52.4kgmol-1, always maintained lower than that of the polycarbonate block (143.8 kgmol-1). Molecular weights of all other components were kept constant. Copolymer interfacial activity, in terms of its efficacy to reduce the size of the dispersed phase and create interface, deteriorated considerably with increasing polycarbonate homopolymer molecular weight. The interfacial area occupied by a single copolymer molecule did not change dramatically. This behaviour was observed with constant (10% w/w) and varying (1-40% w/w) copolymer content. In dilute solutions (1 x 10-3g cm-3) with selective solvents (toluene), the copolymer formed micelles consisting of approximately nine copolymer molecules with no evidence for significant swelling of the polycarbonate core by unreacted polycarbonate homopolymer. Thermodynamic parameters of aggregation showed the process to be enthalpy driven. Copolymer interfacial activity is discussed in terms of phase diagrams for these systems with increasing homopolymer molecular weight. Phase separation of copolymer and polycarbonate homopolymer from the PMMA-rich matrix as the system crosses the b/nodal has been argued to be the mechanism to account for the presence of stable fine polycarbonate-rich dispersions in a PMMA-rich matrix. The relative molecular weight of the polycarbonate homopolymer to that of the polycarbonate block controls the position of the critical copolymer-homopolymer concentration relative to that of the overall system.
Blends containing tetramethyl bisphenol-A polycarbonate: 1. Styrenic polymers
1986
The phase behaviour of blends of tetramethyl bisphenol-A polycarbonate, MPC, with styrene copolymers and substituted styrene homopolymers was examined using d.s.c, and optical indications of phase separation on heating, i.e. lower critical solution temperature, LCST, behaviour. MPC was found to be miscible with styrene/acrylonitrile copolymers, SAN, having an AN content smaller than 13 ~, with a styrene/maleic anhydride copolymer, SMA, having an MA content equal to 8 ~ and with oligomeric styrene/allyl alcohol copolymers, SAA, having an AA content less than 19.1 ~. MPC was also found to be miscible with an oligomeric poly(~-methyl styrene), P~MS, and a copolymer of ~-methyl styrene/acrylonitrile, P~MSAN. Some of the mixtures showed LCST behaviour and based on this and excess volume measurements, to the extent possible, qualitative conclusions were made concerning the relative strength of the interactions among the various blend pairs. It appears that small amounts of AN or MA in the copolymers apparently increases the strength of interactions relative to those observed in polystyrene blends with MPC, whereas the inclusion of a methyl group in the styrenic repeat unit has the opposite effect. The phase behaviour of MPC with styrene based copolymers appears to be influenced by intrachain repulsion between styrene and comonomer units. MPC was found to undergo thermal and solvent induced crystallization when blends were cast from tetrahydrofuran and toluene solutions, but no crystallinity was observed when methylene chloride was used as the solvent.
Polymer, 2004
The phase morphology developed in immiscible polypropylene (PP)/polycyclohexylmethacrylate (PCHMA) blends has been studied using an in situ reactively generated polystyrene-graft-polypropylene compatibilizer from maleic anhydride grafted polypropylene (MA-g-PP) and amine end-capped polystyrene (PS-NH2) reactive precursors during melt-blending. The imidation reaction responsible for the formation of the compatibilizer is similar to the reaction occurring in polyamide/MA-PP (MA-EPR or MA-EPDM) blends which are industrially important. In the present blend PP/PCHMA/(PP-MA-PS-NH2), no undesired reaction occurs between the maleic anhydride groups and the backbone of the PCHMA chain, as is usually the case with polyamide homopolymer. This type of reaction, although considered non significant, has consequences on the phase morphology development as it affects the viscosity of the polyamide matrix when chain scission takes place. PP/PCHMA blends covering the whole range of compositions were prepared. The composition window at which the blends exhibit a droplet-in-matrix phase morphology and that where the two phases are co-continuous were determined using a selective phase extraction in combination with scanning electron microscopy. The generation in situ of the PP-g-PS compatibilizer substantially changed the state of the phase morphology developed. In the blends having a droplet-in-matrix type of morphology, the particle sizes were significantly reduced (by a factor of more than 10). Two types of MA-g-PP reactive copolymers differing in maleic anhydride content (1 and 8wt%) have been separately employed with the same grade of PS-NH2. Emphasis was put on a detailed investigation of the behaviour and structural stability of the blends exhibiting a co-continuous phase morphology when the compatibilizer is generated. Significant differences were found in relation to the maleic anhydride content of the MA-PP reactive compatibilizer precursor.
Macromolecules, 2005
It has long been appreciated that blending of immiscible polymers can allow for synergistic tunability of material properties. 1-5 However, compatibilization of immiscible blends remains an academic and technological challenge. As optimal properties often rely on an average dispersed-phase diameter less than several microns, the stabilization of the dispersed phase domain size against coarsening, taken as the definition 6 of compatibilization, is key to processing immiscible blends. Many compatibilization strategies have been tested, 1 most involving methods that theoretically lead to a reduction in interfacial tension 7 and/or to steric hindrance against coalescence. 6 These strategies include the addition of premade block, 8-12 tapered block, 13 graft, 14 and random 15,16 copolymers during melt processing. The use of added block/graft copolymers has led to compatibilization in selected small-scale studies but has not been commercialized, due in part to the very low critical micelle concentration 5,17,18 (cmc) that prevents sufficient copolymer from reaching blend interfacial regions during melt processing. Random copolymer addition typically leads to
Journal of Applied Polymer Science, 1996
Reactive blends (50/50 w/w) of a low molar mass polyethylene containing free carboxylic groups (PEox) and a semiflexible liquid crystalline polyester (SBH 1 : 1 : 2, by Eniricerche) have been prepared at 240°C in a Brabender mixer, in the presence of Ti(OBu), catalyst, for different mixing times (15, 60, and 120 min). In order to prove the formation of a PEg-SBH copolymer, the blends have been fractionated by successive extractions with boiling toluene and xylene. The soluble fractions and the residues have been analyzed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG and DTG), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). All analytical procedures concordantly show that PE-g-SBH copolymers with different compositions, arising from differences of either the number of PEox carboxylic groups entering the transesterification or the length of grafted SBH branches, are formed as a result of blending. Depending on the relative content of P E and SBH segments, the copolymers dissolve in the solvents, together with any unreacted PEox, or remain in the residues, together with neat SBH.
Characterisation of Diblock Copolymer Blends
2000
PACS. 81.30.-t -Phase diagrams and microstructures developed by solidification and solidsolid phase transformations. PACS. 61.10.Eq -X-ray scattering (including small-angle scattering). PACS. 61.12.-q -Neutron diffraction and scattering.
…, 1999
We investigate the influence of an asymmetric PS-b-PMMA block copolymer (bcp) on the morphology of melt-mixed immiscible binary polymer blends containing poly(styrene-co-acrylonitrile) random copolymer (SAN) and poly(cyclohexylmethacrylate) (PCHMA). By varying the SAN copolymer composition, the balance between the swelling of each block segment located at the interface between the two phases is altered and the effect on blend morphology is studied. As in earlier studies using a symmetric bcp, we find that for a specified shear history, there is a zone of effective emulsification of the blend bounded by regions of internal and external emulsification failure. However, the locations of the boundaries between stable and unstable emulsification differ for an asymmetric versus a symmetric bcp. Thus the morphology depends not only on the segmental swelling ratio but also on the difference in the effective size of each bcp segment. Scaling arguments successfully correlate the limits of stable emulsification for both symmetric and asymmetric bcp.
Journal of Polymer Science Part A: Polymer Chemistry, 1997
This work deals with the relationship between microstructure, melt viscosity, and copolymer concentration of PAmXD,6/PP-g-MA blends [poly(m-xylylene adipamide)/maleic anhydride functionalized polypropylene]. The blends were processed in a Brabender plastograph at a temperature of 265 { 5ЊC and at 45 rpm. The characterization of the microstructure was carried out through SEM analysis after microtome leveling and chemical etching. The melt viscosity of the components and of the blends was measured by the Brabender torque. It was found that the copolymers concentration controls the dimension of the dispersed phase. The composition of the blend (dispersed phase weight percent) has a more limited influence. Variations of the components viscosity ratio during the mixing time have little, if any influence on the dimension of the dispersed phase. A linear relation between the Brabender torque and the specific interfacial area was found. The determination of the copolymer weight fraction leads to the establishment of a close relation between the copolymer concentration and the specific interfacial area. For blends containing from 0 to 7.5 wt % of copolymer, this relation is linear and consequently the concentration of copolymer at the interface is constant at about one copolymer macromolecule per 16 nm 2 .