The study investigated the effects of ageing on the tensile properties and fracture behaviour of an epoxy filled with inorganic fillers having different reactivity to water, such as fly ash, calcium carbonate (CaCO3), and Portland cement. CaCO3 is insoluble in water, whereas fly ash and cement are reactive to water; however, fly ash is less reactive than cement. The water absorption, tensile properties, and mode-I fracture toughness of the epoxy containing 7?wt% of filler were compared after ageing the composites in distilled water at 50?°C. Gravimetric analyses showed that compared to neat epoxy, CaCO3 slightly decreased the equilibrium water uptake of the filled epoxy, whereas fly ash and cement increased the equilibrium water uptake. Compared to the other fillers, the tensile strength of CaCO3-filled epoxy was inferior in both dry and wet conditions. However, in dry condition, the elastic modulus of CaCO3-filled epoxy was slightly higher. Overall, the fly ash-filled epoxy showed better tensile and fracture properties in both dry and wet conditions although it absorbed more water than the other fillers did. Scanning electron microscopy revealed that crack deflection played a dominant role in the toughening of filled epoxies in both dry and wet conditions. 相似文献
The influence of thermodynamic interactions among the components of a polymer system on mechanical properties and their retention on aging has been investigated. The systems considered involve plasticized poly(vinyl chloride)(PVC), and CaCO3 fillers. Inverse gas chromatography was used to measure interaction parameters, and to express these in terms of acid-base concepts. Interaction data were obtained over a wide temperature range. It was shown that the volume of plasticizers retained by the PVC correlates with the measured interaction parameters. Similarly, the interaction parameters identify a CaCO3 filler preferred for reinforcing rigid PVC, and a different CaCO3 filler for use in given PVC-plasticizer combinations. The mechanical properties of filled PVC (up to 40 phr CaCO3), and particularly the ultimate properties of the compounds, correlate with interaction concepts, as do property retention data after accelerated aging of the compounds at 100°C. It is concluded that component interaction parameters may provide useful guidelines to the formulation of compounds with superior properties and reduced property losses due to aging. 相似文献
Changes in properties of PVC compounds upon weathering are categorized as due to physical aging or due to chemical change. PVC's tensile strength, flexural strength, tensile modulus, and flexural modulus generally rise slightly with weathering. DSC data on weathered samples show an annealing effect identical to physical aging. The impact strength of weathered PVC is substantially lower than expected from physical aging. Molecular weight of PVC on the weathered surface is lowered upon weathering. Thus the loss of impact strength of PVC upon weathering is mainly due to chemical change. 相似文献
PVC fibers, fastened to a needle frame, were crosslinked by 2-dibutylamino-4, 6-dimercapto-1,3,5-trizine in the presence of tetra-n-butylammonium bromide and alkali in water at 96°C. Solvent resistance, characterized by the gel fraction of THF, improves markedly. Mechanical properties of the fibers investigated by tensile tests at 20°C show that both the modulus and tensile strength at break increase, while elongation at break decreases over 40% gel content. Creep tests indicate that the resistance to heat deformation improves by crosslinking. The heat distortion temperature increases by 12°C at 75% gel content. Results of dynamic tests show that the Tg of PVC fibers determined by a peak in the loss modulus (E'') increases from 40% gel content. Dynamic modulus (E') increases by 74% at 23°C and the Tg by 37°C in the case of crosslinked PVC fibers having a 92% gel content. The shrinkage of PVC fibers in hot water at 94°C for 30 min decreases more than 50% over 75–80% gel content indicating the improved resistance to heat deformation. 相似文献
Disposable PVC gloves are cost effective, but their mechanical properties can be compromised at extremely high concentrations of plasticizers. The tensile properties of PVC gloves can be improved by incorporating modified fillers into the PVC matrix. In this research, calcium carbonate (CaCO3) was functionalized with γ-methacryloxy propyl trimethoxyl silane (KH-570) and then further modified through a click reaction with n-Octadecyl mercaptan. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy have confirmed that n-Octadecyl mercaptan-modified KH-570 was successfully grafted onto the surface of CaCO3. Composite films were manufactured by blending either pristine CaCO3 or modified CaCO3 with PVC resin paste and their tensile properties, light transmission, moisture permeability, and solvent resistance were evaluated. Compared with CaCO3/PVC and KH-570-modified CaCO3/PVC composite films, n-Octadecyl mercaptan-modified CaCO3/PVC composite films showed higher light transmittance, lower moisture permeability, and higher tensile properties. Dynamic mechanical analysis revealed that these films had low glass transition temperatures, thus broadening their applicability to low-temperature conditions. 相似文献
Poly(L ‐lactide) (PLLA) composites incorporating various inorganic fillers (ifR‐PLA) were prepared by the melt blending technique, and their mechanical and thermal properties were evaluated. The filler types influenced the mechanical properties of ifR‐PLA; for those incorporating particle‐ and whisker‐type fillers the tensile moduli were 3.1–3.7 and 3.7–4.5 GPa, respectively, and the flexural moduli were 4.1–4.8 and 4.8–6.1 GPa. It was found that the tensile strength and modulus, as well as the flexural modulus, of ifR‐PLA incorporating whisker‐type fillers increased in proportion to the volume percent of the fillers (Vf). The flexural strength of ifR‐PLA incorporating 9Al2O3 · 2B2O3 whiskers showed a similar increase, while that of ifR‐PLA incorporating CaCO3 whiskers showed a decrease with increasing Vf. This difference may be because the 9Al2O3 · 2B2O3 with its large aspect ratio kept its original fibrous shape, while the CaCO3 lost its fibrous shape during the blending process. However, the reinforcing effect of these fillers was relatively low compared with that known for the corresponding composites of the conventional polymeric materials, probably because of the poor surface adhesion of PLLA to the fillers.
Comparison of effect on storage moduli of different fillers. 相似文献
An effect of nanosize CaCO3 on physical, mechanical, thermal and flame retarding properties of PBR was compared with commercial CaCO3 and fly ash filled PBR. CaCO3 at the rate of 9, 15, and 21 nm were added in polybutadiene rubber (PBR) at 4, 8 and 12 wt.% separately. Properties such as swelling index, specific gravity, tensile strength, Young's modulus, elongation at break, modulus at 300% elongation, glass transition temperature, decomposition temperature, flame retardency, hardness, and abrasion resistances were determined. The swelling index decreased and specific gravity increased with reduction in particle size of fillers in PBR composites. There was significant improvement in physical, mechanical, thermal and flame-retarding properties of PBR composites due to a reduction in the particle size of fillers. Maximum improvement in mechanical and flame retarding properties was observed at 8 wt.% of filler loading. This increment in properties was more pronounced in 9 nm size CaCO3. The results were not appreciable above 8 wt.% loading of nano fillers because of agglomeration of nanoparticles. In addition, an attempt was made to consider some thermodynamically aspects of resulting system. The cross-linkage density has been assessed by Flory-Rehner equation in which free energy was increased with increase in filler content. 相似文献
In the quest to improve the thermooxidative aging of the poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, nitrile rubber (NBR) was incorporated into the blend to yield a ternary blend of PVC/ENR/NBR. A Brabender Plasticorder with a mixing attachment was used to perform the melt mixing at 150°C and 50 rpm followed by compression molding. The mechanical properties, dynamic mechanical properties, and thermooxidative aging behavior of the ternary blend were compared with those of the binary blends (i.e., PVC/ENR and PVC/NBR). It was found that the ternary blend exhibits mechanical properties which are superior to those of PVC/ENR. A single glass transition temperature (Tg) obtained from dynamic mechanical analysis coupled with synergism in the modulus and some other mechanical properties indicate that PVC, ENR, and NBR form a single phase (miscible system) in the ternary blend. Di-2-ethyl hexylphthalate (DOP) plasti-cizer improves the aging resistance of the blends generally, whereas the presence of CaCO3 as a filler only imparts minor influences on the properties and aging resistance of the blends. 相似文献