The effects of processing time
and concentration of cobalt acetylacetonate III complex in poly(ethylene terephthalate)/polycarbonate
reactive blending were investigated. The blend was prepared in an internal
mixer at 270°C, 60 rpm, at different processing times (5–20 min)
and catalyst concentration (0.00625–0.075 mass%). The reaction product
was evaluated by differential scanning calorimetry (DSC), thermogravimetry
(TG) and wide angle X-rays scattering (WAXS).
In general, the
DSC curves showed two glass transition temperatures (Tg’s)
close to each homopolymer, independent of the processing time and complex’s
concentration, suggesting the presence of two phases: one rich in PET and
other one rich in PC. In all cases, melting temperature (Tm),
cold crystallization temperature (Tcc)
and crystallinity degree (Xc)
were progressively reduced with blending conditions. The TG curves presented
two decays. The first one represented the PET rich phase and the other one
was related to the PC phase. The WAXS diffractograms showed that the Bragg’s
angle and interplanar spacing of PET remaining practically unchanged. 相似文献
PMMA containing 50 wt% of anthracene-labeled PMMA chains end-capped by a phthalic anhydride group (anth-PMMA-anh) has been melt blended at 180°C with PS containing 33 wt% of chains end-capped by an aliphatic primary amine (PS-NH2) and PS bearing 3.5 pendant amine groups (as an average) along the chains (PS-co-PSNH2), respectively. The reactive chains have been synthesized by atom transfer radical polymerization. Conversion of anth-PMMA-anh into PS-b-PMMA and PS-g-PMMA copolymers has been monitored by SEC with a UV detector. The interfacial reaction mainly occurs in the initial melting and softening stage (<1.0 min.), although at a rate which strongly depends on the number of reactive groups attached to PS chains, the higher conversion being observed for the PS-co-PSNH2 containing blends. The phase morphology depends on the architecture of the in-situ formed copolymer. Indeed, a coarser phase dispersion is observed in case of the graft copolymer compared to the diblock. 相似文献
Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials. 相似文献
Thermal analysis and SEM were employed to gain insights in the different stages of morphology development and the thermal properties of polymer‐monolithic stationary phases. The studied system was a thermally initiated free‐radical copolymerization reaction at 70°C of styrene and divinylbenzene in the presence of tetrahydrofuran and 1‐decanol. The key events in the early stages of morphology development are initiation, chain growth, branching, and cyclization, leading to microgel particles. Interparticle reactions through pendant vinyl groups lead to the formation of microgel clusters. The rapid increase in molecular weight and cross‐link density of the microgel clusters causes a reaction‐induced phase separation, and the formation of a macroscopic network of interconnected globules was observed (macrogelation) at around 45 min. After 3 h or 65% conversion, a space‐filling macroporous monolithic network was observed. Afterwards, mainly growth of existing globules takes place, reducing the macropore size. The porogen ratio affects the timing of the reaction‐induced phase separation, strongly influencing the morphology of the polymer material. The use of a mixture of divinylbenzene isomers yielded a monolithic material that is less cross‐linked at the surface compared to the central part of the polymer backbone due to copolymerization‐composition drift. The less cross‐linked outer layer starts devitrifying at 100°C. 相似文献
Summary: The effect of chain architecture of in situ formed copolymers on the interfacial morphology of reactive polymer blends was investigated. We found that the chain architectures of copolymers at the interface significantly affected the reaction and interface roughness. Although the amount of in situ formed Y‐shaped graft copolymers was smaller than that for diblock copolymers, the interface area generated by the former was larger than that generated by the latter.
Cross‐sectional TEM images for the mid‐sample reacted at 180 °C for different reaction times. 相似文献
This paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene-maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence. In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co-continuous two-phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes. 相似文献
Microspheres were prepared using N‐methylolurea‐dodecylamine conjugate (MU‐DOA), an emulsifiable and self‐condensaible oil. MU was prepared by reacting urea and formaldehyde at 70°C in alkali conditions and then conjugating it to DOA by a condensation reaction. The MU‐DOA conjugate was emulsified in distilled water without an emulsifier, and then the oil droplets were hardened to obtain microspheres by a self‐condensation reaction among methylols of the conjugate. The reactions of each step, e.g., the preparation of MU, the conjugation of MU and DOA, and the self‐condensation of emulsified oil, were confirmed by Fourier transform infrared (FTIR) spectra. On scanning electron microscopy (SEM), the microspheres formed by the self‐condensation of the emulsified MU‐DOA were shown as spherical and less than 30 µm in diameter. The phase transition temperatures of DOA, MU‐DOA, and MU‐DOA microspheres were 30.3°C, 21.1°C, and 20.1°C, respectively. The lower transition temperature of MU‐DOA is probably due to the bulky MU, which could reduce the intermolecular interaction of MU‐DOA. Zeta potentials of the microspheres decreased from positive to negative value as pH increased from 3.5 to 10.5. The deprotonation of the amines of MU‐DOA would be responsible for that result. 相似文献
The thermal stability and molecular order in monolayers of two organic semiconductors, PBI‐PA and PBI‐alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI‐PA, are reported. In situ X‐ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI‐PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI‐alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate. 相似文献
Hydrothermal processing of polyamide 6(PA6) with the presence of lanthanum chloride(La Cl3) was studied in the temperature region from 160 °C to 250 °C. PA6 will be dissolved in the superheated water when temperature is above 160 °C. And as PA6 is dissolved, hydrolysis will happen, which makes PA6 chains degrade. By adding La Cl3 in the hydrothermal environment, the PA6 hydrolysis will intensify, especially when the hydrothermal temperature is higher than 200 °C. When the hydrothermal system cools down, the hydrolyzed PA6 segments will crystallize from the solution or remain dissolved in the solution depending on molecular weight. In addition, the hydrolyzed compound of La Cl3 would affect the crystallization of PA6 segments with proper size, and ? phase would be presented. 相似文献