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1.
The effect of the amount of desorbed water on the mechanical properties of composites based on low-density polyethylene and linen yarn production waste (LW) is analyzed by statistical methods. It is shown that the amount of absorbed water decreases during the desorption process at room temperature both for specimens modified and unmodified with diphenylmethane diisocyanate (DIC.) The most sensitive to the action of water is the elastic modulus, which decreases considerably under the effect of water and is fully restored in the desorption process. The tensile strain also increases with the amount of absorbed water. It is found that the elastic modulus of the unmodified composite correlates linearly with the amount of desorbed water. Between the amount of desorbed water and the tensile strain, as well the specific work of deformation, a negative linear correlation is revealed. After water desorption, all strength and deformation characteristics of both the modified and unmodified composites are fully recovered.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 515–524, July–August, 2005. 相似文献
2.
The possibilities of utilizing wastes of linen thread production (chaffs, spinning and roving losses) in recycled polyolefin composites have been investigated. The wastes were mixed with recycled polyethylenes (produced from domestic and industrial film production wastes). The physicomechanical properties (tensile strength, bending and tensile moduli, and water resistance) and the fluidity (melt flow-behavior index) for systems with a different filler content are estimated. Almost all the composite materials obtained have satisfactory fluidity (melt flow-behavior index is not lower than 0.07–0.15 dg/min). For all types of the composites, a slight increase in tensile strength and a considerable increase (3–7 times) in bending and tensile moduli were observed. The water resistance of the composites decreased with an increase in the filler content. The modification of filled systems with diisocyanates (diphenylmethane diisocyanate) improved the useful properties and water resistance of all the composites investigated. 相似文献
3.
4.
The effect of the amount of absorbed water on the physicomechanical indices (tensile modulus, tensile strength, and ultimate strain) of composites based on secondary polyethylene (SPE) of two trademarks and linen yarn production waste (LW), both with and without a coupling agent (diphenylmetane diisocyanate - DIC), is evaluated. It is shown that the strength properties considerably depend on the time of water sorption and on the blend composition. The tensile strength decreases with increased amount of absorbed water (with increased time of exposure to distilled water) and with increased content of LW in the composites. This can be explained by the plasticizing effect of water molecules, which is confirmed by the increase in the ultimate strain of specimens after their exposure to water. The slight increase in the strength observed for the systems modified with DIC is probably caused by cross-linking of the free diisocyanate in the system under the action of moisture. The diisocyanate intensifies the interfacial interaction and retards the water-sorption process. Therefore, the resulting strength indices of these systems are higher than those of the unmodified compositions. 相似文献
5.
Kajaks J. A. Reihmane S. A. Bulmanis V. N. Lejnieks J. E. 《Mechanics of Composite Materials》2001,37(2):167-170
The effect of the amount of absorbed water on the physicomechanical indices (tensile modulus and tensile strength) of composites based on low-density polyethylene (LDPE) and linen yarn production waste (LW), both with and without coupling agents (stearic acid - SA and diphenylmetane diisocyanate - DIC), is studied. It is shown that the strength properties depend considerably on the time of water sorption and on the blend composition. The tensile strength decreases with increased amount of absorbed water (with increased time of exposure to distilled water) and with increased content of LW in the composite. Somewhat different results are obtained for systems containing SA and DIC modifiers. The modifiers, intensifying the interfacial interaction, retard the process of water sorption, therefore the drop in the strength indices is not so significant. Of special interest is the behavior of systems with DIC. In some cases, a slight increase in strength (after a two to five day exposure to water) is observed, which is probably caused by cross-linking of the free diisocyanate in the system under the action of moisture. 相似文献
6.
G. G. Bakradze J. A. Kajaks S. A. Reihmane J. E. Lejnieks 《Mechanics of Composite Materials》2007,43(5):427-432
The effect of the amount of sorbed water on the mechanical properties (tensile modulus, tensile strength, unit work of fracture,
and characteristic strains) of composites based on a recycled low-density polyethylene, both unmodified and modified with
diphenylmethane diisocyanate (DIC), is an a lyzed by statistical methods. The results of tensile tests are found to depend
on the amount of sorbed water considerably. The elastic modulus, the unit work of fracture, and the characteristic strains
correlate linearly with the amount of water. It is found that the elastic modulus drops after the sorption of water, but then,
during the desorption process, it is restored gradually and reaches its initial value after a 30-day drying. This is explained
by the plasticizing effect of water on composite materials containing hydrophilic natural fibers. DIC improves the interfacial
interaction of the fiber-matrix interface and slows down the desorption of water. The investigations of the main deformational
and strength characteristics of the unmodified and modified systems showed that the ad verse effect of water completely disappeared
after a 30-day drying. The same conclusion, with a 95% probability, can be drawn from the results of an analysis of variance
(ANOVA).
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 626–638, September–October, 2007. 相似文献
7.
The possibilities of using various methods of mathematical statistics for processing and analyzing the results of deformation and strength tests on composites made from a low-density polyethylene and linen yarn production waste are evaluated. The hypothesis that the experimental strength data agree with the Gaussian distribution is examined by the Shapiro–Wilk test (W-test.) It is shown that the Gaussian distribution, both for systems unmodified and modified with diphenylmethane diisocyanate (DIC), is valid only for two parameters: the maximum tensile strength max and the elastic modulus E
t. For the other parameters (the relative elongation max corresponding to max, the specific total work of failure A
b), and the specific work of failure to the tensile strength A
max), a non-Gaussian distribution is observed. An analysis of measurements for different specimens by the Bartlett test shows that the E
t data have equal variances for both systems (with and without DIC), but for the system containing DIC, the max data have different variances. A two-factor ANOVA analysis reveals that DIC considerably affects the tensile strength and modulus of composites, but the influence of test conditions is a statistically significant factor only for the modulus. The coefficient of variation is considerably lower for max than for E
t and can be used as a quantitative measure for the degree of heterogeneity of the composites investigated. 相似文献
8.
The possibilities of utilizing wastes of linen thread production (chaffs, spinning and roving losses) in recycled polyolefin composites have been investigated. The wastes were mixed with recycled polyethylenes (produced from domestic and industrial film production wastes). The physicomechanical properties (tensile strength, bending and tensile moduli, and water resistance) and the fluidity (melt flow-behavior index) for systems with a different filler content are estimated. Almost all the composite materials obtained have satisfactory fluidity (melt flow-behavior index is not lower than 0.07–0.15 dg/min). For all types of the composites, a slight increase in tensile strength and a considerable increase (3–7 times) in bending and tensile moduli were observed. The water resistance of the composites decreased with an increase in the filler content. The modification of filled systems with diisocyanates (diphenylmethane diisocyanate) improved the useful properties and water resistance of all the composites investigated.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 199–210, March–April, 1999. 相似文献
9.
J. A. Kajaks G. G. Bakradze A. V. Viksne S. A. Reihmane M. M. Kalnins R. Krutohvostov 《Mechanics of Composite Materials》2009,45(6):643-650
The shear strength of three-layer birch veneer/polyolefin/birch veneer lap joints has been investigated. It was found that
the optimum technological parameters for producing three-layer laminated systems (plywood) at 180°C were a pressure time of
1-3 min (plus 3-min preheating) and pressure of 5-10 MPa. All the systems investigated exhibited relatively high values of
shear strength, which were higher than those of the industrially produced plywood based on phenol-formaldehyde glues (3.5-5
MPa). It is shown that the use of interfacial modifiers can increase the shear strength by 50% compared with its initial values.
The high shear resistance is explained by the high mechanical adhesion between the hot melts and the wood substrate. After
a prolonged moisture influence (70 days at relative air humidity of 80%), all the systems investigated showed a considerable
(up to 25%) increase in the shear strength. This can be explained by swelling of birch veneer, which gives rise to additional
resistance forces between the hot melt and the substrate. 相似文献
10.
G. Bakradze J. Kajaks S. Reihmane R. Krutohvostov V. Bulmanis 《Mechanics of Composite Materials》2007,43(6):573-578
The effect of water on the mechanical properties (tensile modulus, ultimate tensile strength, tensile strain, and specific
work at break) of both chemically treated and untreated composites based on a recycled low-density polyethylene and linen
yarn production waste is analyzed. It is found that three water sorption-desorption cycles change the tensile properties of
both the materials irreversibly. This effect is considered as the result of partial fracture of the fiber-matrix interface.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 839–848, November–December, 2007. 相似文献