Studies of mechanical and moisture regain properties of methyl methacrylate grafted silk fibers

The mechanical properties such as the tenacity, breaking extension, initial modulus, elastic and work recovery, and stress relaxation behavior of methyl methacrylate (MMA) grafted silk fibers prepared under different conditions were measured and explained in terms of the relative dominance of the stress concentration, reduction in the interchain cohesion, and fiber matrix stiffening at different grafting percentages. The moisture regain characteristics of fibers grafted in the presence of different solvents were also studied and compared. The grafting of MMA on silk was found to improve the recovery properties significantly without affecting the stress relaxation behavior. The moisture regain studies indicate that moisture regain is reduced with increasing length of the grafted poly(MMA) chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 969–974, 2002; DOI 10.1002/app.10202     

Some physical properties of acrylamide and acrylonitrile grafted nylon 6

Graft copolymerization of acrylamide and acrylonitrile on nylon 6 swollen in formic acid (60%) for 30 min was performed using ceric ions as initiator at 60°C. The optimum conditions to get highest percentage of graft-on were utilised to prepare the grafted samples with various amounts of polymer deposited inside the fibres. The mechanical properties, moisture regain, density, infrared studies, birefringence, dye uptake and dynamic mechanical properties were determined for the grafted samples and the results are discussed in relation to possible structural changes due to graft copolymerisation.     

亲水性聚酯短纤维对气态水的吸湿与放湿性能研究

测试比较了聚酯短纤维、亲水性聚酯短纤维、脱脂棉纤维在不同温度下对气态水的吸湿与放湿性能,分析了纤维中亲水基团对吸湿速率的影响,以及烘干温度对纤维回潮率的影响。结果表明:在105℃条件下,亲水性聚酯短纤维中的水分不能完全脱除;随着烘干温度从105℃上升至125℃,亲水性聚酯短纤维以及脱脂棉纤维继续脱除水分,且水分释放变化率更明显;随着烘干温度从105℃升至125℃,聚酯短纤维的回潮率没有变化,保持在0.40%,而亲水性聚酯短纤维的回潮率从1.33%提高至1.43%;亲水性聚酯短纤维对气态水的吸湿与放湿性能明显强于聚酯短纤维。     

Mechanical property studies of poly(methyl methacrylate)-grafted viscose fibers

Graft copolymerization of methyl methacrylate (MMA) on viscose fibers (grade 1.5 × 51 mm; Nagda; grey staple; bright bleached) was studied under a photoactive condition with visible light using conventional Mohr's salt–potassium persulphate as the redox initiator. The mechanical properties of the grafted viscose fiber, such as tenacity, breaking extension, and initial modulus were studied. The effect of monomer–solvent combination on viscoelastic nature (elasticity work recovery and stress relaxation) of the grafted fibers have also been explained. The moisture regain characteristics of the grafted fibers were also studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2585–2591, 1998     

丙烯酸接枝改性PET纤维的结构与性能

采用丙烯酸接枝改性聚对苯二甲酸乙二酯(PET)纤维,探讨了接枝率对PET纤维结构、回潮率、染色性能以及力学性能的影响。结果表明:随着接枝率的增加,PET纤维密度变化不大,双折射率略为下降,纤维的吸湿性、抗静电性和染色性能提高,拉伸性能有所下降。当接枝率为10.78%时,PET纤维经0.03 mol/L的Na_2CO_3溶液处理后,其质量比电阻为1.34×10~6Ω·g/cm~2,回潮率为5.05%,纤维拉伸强度为3.31 cN/dtex,上染率达93.8%。     

Physical and fine structure properties of cotton fibers swollen with trimethylbenzylammonium hydroxide

Cotton fiber was treated with aqueous trimethylbenzylammonium hydroxide (Triton B) at concentrations over the range 25%–40%. After complete removal of the swelling agent, the samples were evaluated for the extent of swelling, strength and elongation, birefringence, moisture regain, density, crystallinity, x-ray diffraction patterns, and microfibrillar morphology. Electron-microscopical examination and other evaluation of fine structure properties revealed that the nature of swelling is intercrystalline up to 30% concentration of Triton B, and intracrystalline beyond that. Although the swelling as measured by propanol-2 retention after treatment with 30% Triton B is about twice as much as that of the control, the original structure remains almost unchanged except for some gain in strength and elongation and increase in moisture regain. At 32% Triton B concentration and beyond, rapid decrystallization takes place, accompanied by a fall in birefringence, density, and crystallinity index. X-Ray analysis showed significant loss of lateral order and partial conversion of cellulose I to cellulose II at 35% and 40% Triton B concentrations. The results indicate that, used at the critical concentration of 30%, Triton B can be a useful swelling agent for cotton fibers as it opens up the fine structure of cellulose considerably without impairing any important physical properties.     

Some physicochemical properties of methyl methacrylate-grafted nylon 6. II.

Graft copolymerization of methyl methacrylate on nylon 6 was investigated using KMnO₄ as initiator at 60°C. The optimum conditions of the grafting process using various amounts of methyl methacrylate have been utilized. Physical and chemical properties of the grafted nylon such as moisture regain, density, and infrared spectra are studied. Furthermore, the dyeing behavior of the grafted nylon toward acid and direct dyes is also investigated. The rate of graft copolymerization (R_p) of methyl methacrylate with this system was evaluated and expressed by the following equation depending upon the potassium permanganate concentration used: The degree of polymerization of isolated poly(methyl methacrylate) from the grafted nylon was found to be a first-order dependence.     

Photoinduced graft copolymerization of 2-hydroxyethyl methacrylate on cotton cellulose in the presence of triethyleneglycol dimethacrylate

The addition of a bifunctional monomer, triethylene glycol dimethacrylate (TEGDMA), to a grafting system containing 2-hydroxyethyl methacrylate (HEMA) and benzoin ethyl ether photoinitiator substantially increased the graft add-on of the unswollen and sodium hydroxide–swollen cotton cellulose. Grafting caused changes in the properties of the substrate such as moisture regain, the water of imbibition, and the dyeability with a direct and a reactive dye in accordance with the graft level. The observations have been explained in relation to structural changes in the grafted cotton. © 1994 John Wiley & Sons, Inc.     

Properties and structure of nylon fibers in relation to drawing and aqueous phenol treatments

The changes in nylon 66 fiber structure and properties which take place during drawing and aqueous phenol treatments were studied by means of measurements of length, birefringence, density, moisture regain, x-ray diffraction, stress–strain behavior, and sound velocity. Drawing was found to establish molecular orientation along the fiber axis predominantly in the early stages, whereas the development of lateral order occured primarily after a certain level of orientation had been achieved. Treatments in aqueous phenol solutions caused longitudinal contractions which depended on phenol concentration (1-5%), draw ratio (1-6), and the tension on the fiber during the treatment. The treatments resulted in an increase in the lateral order, decrease in orientation and corresponding changes in mechanical properties. Moisture regain was inversely related with density for the untreated fibers of various draw ratios, but the relationship became complex after treatments in phenol. The data are interpreted in terms of changes in the lateral order distributions, which permits an increase in the fibers' sorptive capacity despite an increase in the mean lateral order.     

生物质胶原蛋白纤维性能测试及对纺纱的影响分析

测试了生物质胶原蛋白纤维的力学性能、卷曲性、回潮率、质量比电阻等,并和棉、毛、丝等纤维进行对比。实验结果表明,胶原蛋白纤维拉伸强度较大,卷曲弹性较好,回潮率略低于棉,含油率适中,纺纱性能优良。     

Grafting of formaldehyde-crosslinked and cyanoethylated cotton cellulose with acrylate monomers

Formaldehyde-crosslinked cotton and cyanoethylated cotton were grafted with methyl, ethyl, and n-butyl acrylates and methyl methacrylate using ceric ion as initiator. It was observed that the graft yields for formaldehyde-crosslinked cotton were significantly higher than those for native cotton. An increase in the bound formaldehyde resulted initially in a decrease in molecular weight of grafts; but later on, an increase was observed. In the case of cyanoethylated cottons, increasing the degree of substitution resulted in increase in graft yields. Molecular weights of the grafts increase up to a D.S. of 0.3, after which they decrease. These results are interpreted in terms of rates of initiation and termination being influenced by production of additional sites due to swelling of cellulose fibers.     

Graft copolymerization of methyl methacrylate upon gelatin initiated by benzoyl peroxide in aqueous medium

The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65–90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 × 10⁻² mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate‐grafted gelatin as density, moisture regain, and water uptake were also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1547–1556, 1999     

Physical,chemical, and dyeing properties of Bombyx mori silks grafted by 2‐hydroxyethyl methacrylate and methyl methacrylate

To obtain silk weight gain and to improve silk properties, Bombyx mori silks were grafted with either 2‐hydroxyethyl methacrylate (HEMA) or methyl methacrylate (MMA). The moisture regain of the HEMA‐grafted and MMA‐grafted silks depended on the hydrophilicity of the used monomers. The acid and alkaline resistances of the HEMA‐grafted and MMA‐grafted silks were clearly improved. Both commercial synthetic dyes, that is, acid and reactive dyes, and a natural dye extracted from turmeric, with potassium aluminum sulfate as a mordant, were used in this study. The results suggested that the dye uptake increased in the presence of poly(2‐hydroxyethyl methacrylate) or poly(methyl methacrylate) in the silk fibroin structures when acid and curcumin dyes were used. The washfastness level of the HEMA‐grafted silk dyed by acid and reactive dyes was similar to that of the degummed silk. However, the colorfastness to washing of the MMA‐grafted silk dyed by an acid dye was improved when the polymer add‐on concentration was 65%. In addition, the washfastness for both grafted silks was improved when they were dyed with natural curcumin dyestuff. The acid and alkaline perspiration fastness properties remained unchanged for the HEMA‐grafted and MMA‐grafted silks when acid, reactive, and curcumin dyes were applied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The effect of N,N-dimethylformamide and polymer grafting on the morphology of polyester fibers in fabric substrate

Photo-induced graft polymerization of acrylic acid (AA) and methyl acrylate (MA) in the liquid and vapor phase, respectively, onto N,N-dimethyformamide (DMF)-pretreated poly(ethylene terephthalate) (PET) fibers in fabric substrate was studied. The effect of various synthesis conditions and DMF pretreatment on the graft yields on PET was investigated. The internal morphology and properties of DMF-pretreated and grafted PET fibers in the fabric were characterized using density and birefringence measurements, differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), dyeing methods, and critical dissolution times. The grafting was promoted by increasing DMF pretreatment temperature and the amount of DMF retention in the PET. Increasing biacetyl and monomer flow time and irradiation time enhanced grafting. DMF pretreatment resulted in increases in total void content, degree of crystallinity, trans-isomer content, chain folding, segmental mobility, and molecular packing of the PET, but caused decreases in its amorphous orientation, intermolecular forces, and individual void size through longitudinal shrinkage, lateral swelling, and removal of oligomers. Subsequent graft copolymerization led to further changes in the internal morphology and properties of the PET. PET grafted with AA had a higher cohesive energy density, lower degree of molecular packing, and larger individual void size, but less total void content, lower segmental mobility, less chain orientation, and a lower degree of crystallinity. PET grafted with MA showed increases in total void content, individual void size, segmental mobility, and molecular packing, but showed decreases in chain orientation and degree of crystallinity. © 1996 John Wiley & Sons, Inc.     

Structure of decrystallized cotton in fabrics prepared by alkali and acrylonitrile treatments

The crystalline structure of decrystallized cotton, prepared by partial cyanoethylation with the use of sodium hydroxide aqueous solution and acrylonitrile, was examined by x-ray and IR data, in connection with such fabric properties as moisture regain. It was found that the moisture regain of the cotton fabric first increased, passed through a maximum at about 6 mole-% of cyanoethylation, and then slightly decreased with increasing degree of cyanoethylation. The increase of moisture regain in the region of the lower degree of cyanoethylation was well related to the decrease in the crystallinity of cotton. The x-ray diffraction studies revealed that the distension and disorder of the unit cell occurred primarily in the direction perpendicular to the (101) crystal plane as cyanoethylation proceeded.     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

Mechanical and some other properties of acrylic-monomer-grafted nylon 6 fiber

Nylon 6 fiber, grafted with various vinyl monomers, viz., methyl methacrylate (MMA), ethyl methacrylate (EMA), and n-butyl methacrylate (n-BMA) were evaluated for their tensile, dye uptake, moisture regain, and solubility characteristics and compared to those of the parent nylon 6 fiber. The tensile properties (tenacity and initial modules) of the grafted samples show a decreasing trend and the percentage breaking elongation an increasing trend with the increase in the graft level in the case of all the three monomers compared to parent nylon 6 fiber. Disperse dye uptake also shows a decrease with the increase in the graft level in all the three monomers grafted only onto nylon 6 fiber. With the introduction of hydrophobic groups in the polymer backbone the moisture regain values decrease. This is true for all the samples and follows the order MMA-g-nylon > EMA-g-nylon > n-BMA-g-nylon. Solubility of the polymer in the solvent orthochlorophenol (OCP) and metacresol (MC) also decreases with the increase in the graft level for all the three monomers used in the following manner: OCP: EMA-g-nylon > n-BMA-g-nylon > MMA-g-nylon; MC: n-BMA-g-nylon > EMA-g-nylon > MMA-g-nylon.     

Grafting of poly(ethylene terephthalate) fibers with methacrylic acid using benzoyl peroxide

The graft copolymerization of methacrylic acid onto poly(ethylene terephthalate) fibers, by the aid of benzoyl peroxide, have been investigated. The graft yield increased up to 85°C, and then decreased with the further increase in temperature. The maximum graft yield was obtained at benzoyl peroxide concentration of 4.0 × 10^?3 mol/L. The increase in the concentration of monomer was found to increase the graft yield. The change in the graft yield was followed by the experiments carried out using different water/solvent mixtures. Also, the change in the properties of polye (thylene terephthalate) fibers grafted with methacrylic acid such as moisture regain, density, and diameter were investigated.     

Chemical modification of cotton fiber by alkali-swelling and substitution reactions—acetylation,cyanoethylation, benzoylation,and oleoylation

By impregnating cotton fiber with alkaline swelling agents and reacting with some chemical agents which can be substituted for the hydroxyl groups on cellulose molecules in the presence of alkali, highly accessible or decrystallized cotton fibers can be obtained. As the effective substitution reactions, acetylation by acetic anhydride and cyanoethylation by acrylonitrile were applied. The cotton fibers modified by these chemical treatments showed no decrease of tensile strength, and had moisture regain higher than the untreated cotton though the degrees of substitution were as high as 20–30 mol %. The resistance to heat or acid and the soil removal were improved. Dyeability for direct dye was increased, and dyeability for disperse or cationic dye was also given. Benzoylation and oleoylation were also investigated. Crease recovery of the cotton fabrics was somewhat improved and dyeability for disperse dye was given. The cotton fabrics oleoylated after decrystallizing by alkali–acrylonitrile treatment had moisture regain almost the same as the untreated cotton, while high water repellency was given.     

Study on ketalization reaction of polyvinylalcohol by ketones. V. The film properties of polyvinylketals obtained by aliphatic ketones

The physical and chemical properties of polyvinylketals (PVKL) prepared from seven aliphatic ketones [acetone, methyl ethyl ketone (MEK), methyl n-propyl ketone (nPK), methyl i-propyl ketone (iPK), methyl n-butyl ketone (nBK), methyl i-butyl ketone (iBK), methyl t-butyl ketone (tBK)] were studied. The moisture regain and water vapor permeability of PVKL films decrease in the following order: acetone > MEK > nPK > iPK ≒ nBK > iBK > tBK. The contact angle measurements revealed that this order is determined by the surface free energy of films, which depends upon the kind of the original ketones. PVKL (acetone) with low ketalization degree was not soluble in neutral water and had lower moisture regain than PVA. As shown in X-ray analysis, the molecular orientation was not random, the crystalline part of PVA remaining. Thus, it becomes clear that behavior of PVKL in water is affected not only by the hydrophobicity of film surface, but also by the crystallinity of PVKL.