Summary: The effects of interfacial interaction between nano‐CaCO3 and PVC on mechanical properties and morphology of PVC/nano‐CaCO3 composites were studied. Nano‐CaCO3 was treated with vibromilling in the presence of PVC and coupling agents. The mechanical properties of PVC/treated nano‐CaCO3 are remarkably improved. Transmission electron microscopy results revealed that vibromilled nano‐CaCO3 particles are well dispersed in PVC matrix with good homogeneity and well adhered to PVC matrix. Molau test indicated that chemical reaction between newly formed surface of nano‐CaCO3 and PVC or coupling agent took place. Theoretical calculation results show that the interfacial interaction between PVC and nano‐CaCO3 are substantially improved through vibromilling treatment of nano‐CaCO3 in the presence of PVC and coupling agent.
Summary: Polyoxymethylene (POM)/elastomer/filler ternary composites were prepared, in which thermoplastic polyurethane(TPU) and an inorganic filler, CaCO3, were used to achieve balanced mechanical properties of POM. A two‐step processing method, in which the elastomer and the filler were mixed to a masterbatch first and then the masterbatch was melt‐blended with pure POM, was used to obtain a core‐shell microstructure with CaCO3 covered by TPU. A brittle‐ductile transition phenomenon was observed with increasing TPU content for this ternary system. To better understand the toughening mechanism, we investigated the fractured surface, interparticle distance, and the spherulite size of POM as function of the TPU and CaCO3 content. The critical TPU content depended on not only the content of CaCO3, but also the size of CaCO3 particles. The observed brittle‐ductile transition was discussed based on the crystallinity and spherulite size of POM as well as Wu's critical interparticle distance theory. The results showed that the impact strength of POM/TPU/CaCO3 ternary system depends on a critical, interparticle distance, which varies from one system to another. The dependence of the impact strength on the spherulite size was considered for the first time, and a single curve was constructed. A critical spherulite size of 40 micron was found, at which brittle‐ductile transition occurs, regardless of the TPU and CaCO3 content or the size of CaCO3 particles. Our results indicate that the spherulite size of POM indeed plays a role in determining the toughness, and must be considered when discussing the toughening mechanism.
Izod impact strength vs. the crystal size for POM/TPU blends and POM/TPU/CaCO3 ternary composites. 相似文献
Abstract Polylauryllactam was used to improve the impact strength of polyvinylchloride (PVC)/chlorinated polyethylene (CPE) blends without sacrificing their tensile properties. The enhancement of the impact strength increased with the increase of the CPE content in the PVC/CPE blends due to the formation of intermolecular hydrogen bonds among PVC, polylauryllactam and CPE macromolecules. A doubled impact strength of the PVC/CPE blend with 20 weight percent of CPE was obtained after the addition of 1.5 phr polylauryllactam. The PVC/CPE blends with polylauryllactam have a better dimensional stability compared with the PVC/CPE blends without the additive, according to their viscoelastic characteristics. Polylauryllactam shortened the processing time to reach a minimum melt viscosity in the processing of the PVC/CPE blends. 相似文献
High density polyethylene (HDPE), calcium carbonate (CaCO3), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder.
The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect
of EVA loading on the melting temperature (Tm) and the crystallization temperature (TC) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO3 was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading
of CaCO3, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO3 blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and
interfacial interaction between CaCO3 with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of
the CaCO3 by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO3/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques. 相似文献
The permeability P, diffusivity D, and activation energy for diffusion, ED, of He, O2, N2, and CO2 were determined for blends of PVC/chlorinated polyethylene (CPE), where the chlorine content of the CPE components varied: 36 wt-% for CPE-1, 42 wt-% for CPE-2, and 48 wt-% for CPE-3. The difference in thermal expansion coefficients Δα above and below the glass transition temperature Tg of the polymers and the fractional free volume Vg of the polymers at their Tg were determined. Density and crystallinity measurements for the blends were also carried out as in the earlier work (Shur and Rånby, J. Appl. Polym. Sci., 19 , 1337 (1975)). Dynamic mechanical measurements of the blends were made using a torsion pendulum at about 1 Hz. P and D decreased, but ED increased with increasing CI content of CPE in the blends. P and D for the blends showed no additivity. The permeability indicated phase inversion for blend compositions at about 10% of CPE-1 and CPD-2 by weight. The experimental and the calculated densities were largely the same for PVC/CPE-1 blends; but for PVC/CPE-2 and PVC/CPE-3 blends, the experimental values were higher than the calculated ones. The Δα and Vg values for PVC and the three CPE samples decreased with increasing CI content in the polymers. Dynamic mechanical measurements indicate that PVC/CPE-1 and PVC/CPE-2 blends form largely incompatible blends, while PVC/CPE-3 blends are compatible to some extent. There is some weak interaction between PVC and CPE-3 giving a low level of compatibility. The solubility of gases obtained from time-lag measurements of diffusion for 50/50 blends decreased for He, O2, and N2, but increased for CO2 with increasing Cl content in CPE. The solubility of He, O2 and N2 shows a positive correlation with the Lennard-Jones force constant ?/k. However, a deviation from the linear relation between ?/k and In S was observed for CO2 and the deviation became larger with increasing Cl content in CPE. The abnormally high solubility of CO2 is probably due to the high polarizability of this gas. The heat of solution ΔHs indicates that for He the sorption process may be a molecular slip process (endothermic), but for other gases the sorption may proceed by a dissolution process (exothermic). There is a large difference between the calculated solubility for the blends assuming incompatibility and the experimental values from time-lag measurements. This may partly be due to the uncertainty of sorption values obtained from the time-lag method and/or partly to changes of sorption modes by interaction between PVC and CPE in the blends. The resulting transport behavior of the blends is discussed on the basis of the free volume concept and of phase–phase interaction in the blends. 相似文献