Characterization of nylon 6 fibers grafted by acrylic monomers

Samples of nylon 6 fibers grafted with the acrylic monomers methyl methacrylate (MMA), ethyl methacrylate (EMA), and n-butyl methacrylate (n-BMA) with various graft levels were investigated by infrared, X-ray and scanning electron microscopic studies and the changes due to grafting with respect to the parent nylon 6 fibers were studied. The IR spectra of grafted nylon 6 samples show that there is a little change in the peak heights by grafting of nylon 6 with various monomers. The characteristic peaks of parent nylon are, more or less, maintained in the case of grafted samples. A peak at 1730 cm^?1 of the ester group was noted which confirms that the polymer has been grafted with the monomer. X-ray diffraction data on the grafted samples show some remarkable variations with the degree of grafting, depending upon the nature of the graft monomer. The percentage of crystallinity varies with the degree of grafting. In the initial stages of grafting it shows a decrease in the case of PMMA graft and an increase in the case of PEMA and Pn-BMA graft. At higher degrees of grafting (above 50% graft add-on) the percentage of crystallinity decreases in all the three cases. Orientation index has been found to increase in the initial stages of grafting in the case of EMA and n-BMA grafted nylon 6 and it decreases later on, whereas in the case of MMA graft it decreases continuously even at low graft level. The studies of surface characteristics for the parent and grafted samples show that spectacular changes on the surface of the various samples have taken place. With the increase in the graft level the diameter of the fiber increases and also the voids and cracks appear on the surface.     

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.     

Graft copolymerization of nylon 6 with methylmethacrylate and methylacrylate,I. Optimum conditions of grafting and thermal behaviour of the copolymers

Nylon 6, 20 denier, monofilaments were grafted with methylmethacrylate and methylacrylate using ceric ion/sulphuric acid as initiator. Grafted nylon samples with different % graft-on were prepared by varying the reaction conditions. The thermal stabilities of these grafted samples were compared with parent nylon using dynamic thermogravimetry in air at a heating rate of 6 °C/min up to a temperature of 550 °C. The initial decomposition temperature (IDT) integral procedureal decomposition temperature (IPDT) and activation energy (E) values indicated that thermal stability decreased as a result of grafting.     

Thermal behaviour of acrylamide and acrylonitrile grafted nylon 6

The thermal behaviour of nylon 6, 20 denier, monofilament (semi-dull) and the graft copolymers of nylon 6 with acrylamide and acrylonitrile was studied using dynamic thermogravimetry in air at a heating rate of 6°C/min. up to a temperature of 550°C. The thermal stabilities of the samples grafted with acrylamide and acrylonitrile to various percentages of grafting were computed from their primary thermograms by calculating the values of initial decomposition temperature (IDT), integral procedure decomposition temperature (IPDT) and activation energy (E). The results show that the thermal stability of the samples grafted with acrylonitrile increases with increase in graft-on percentage and the thermal stability of the samples grafted with acrylamide decreases with increase in graft-on percentage. The reduction is, however, not very significant.     

Studies of Cu(II)–IO4− initiated graft copolymerization of methyl methacrylate from defatted pineapple leaf fibres

A study of the graft copolymerization of methyl methacrylate (MMA) from defatted pineapple leaf fibre (PALF) was carried out in the temperature range 45–55 °C, using a copper sulphate (CuSO₄) and potassium periodate (KIO₄) combination as initiator in an aqueous medium. Effects of variation of time and temperature, concentration of Cu(II), KIO₄ and MMA, the amount of PALF, and also the effects of some inorganic salts and organic solvents on the percentage of graft yield have been investigated. On the basis of experimental findings, a reaction mechanism is proposed. FTIR spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy of the original defatted PALF and MMA grafted PALF have been carried out. The thermal stability of PALF is improved through grafting. © 1999 Society of Chemical Industry     

Autoadhesion of high density polyethylene (HDPE) to HDPE by ultraviolet grafting of methacrylates and acrylates

A study has been made on the effect of the presence of grafted acrylic layers on the autoadhesion of polyethylene. Methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), and butyl methacrylate (BMA) were grafted onto high density polyethylene (HDPE). The grafting reaction was faster at higher temperature and methacrylates graft more easily than acrylates. For methacrylates and acrylates, the grafted amount increases with increasing length of the pendant alkyl chain. The grafting temperature is a crucial factor affecting the adhesion of grafted PE samples. For the samples grafted at lower temperature (in a room temperature water bath), the adhesion is very low (less than 50 N/m), even for very thick grafted layers. But for the samples grafted at higher temperature, much higher adhesion can be obtained. The presence of homopolymer was another factor affecting the adhesion of PE samples. When homopolymer is removed from the surface of the grafted sample, higher adhesion can be obtained. For some samples, the highest peel strength of more than 1000 N/m has been obtained. The low adhesion of the samples grafted at low temperature is attributed to the high branching of grafted chains.     

AUTOADHESION OF HIGH DENSITY POLYETHYLENE (HDPE) TO HDPE BY ULTRAVIOLET GRAFTING OF METHACRYLATES AND ACRYLATES

A study has been made on the effect of the presence of grafted acrylic layers on the autoadhesion of polyethylene. Methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), and butyl methacrylate (BMA) were grafted onto high density polyethylene (HDPE). The grafting reaction was faster at higher temperature and methacrylates graft more easily than acrylates. For methacrylates and acrylates, the grafted amount increases with increasing length of the pendant alkyl chain. The grafting temperature is a crucial factor affecting the adhesion of grafted PE samples. For the samples grafted at lower temperature (in a room temperature water bath), the adhesion is very low (less than 50 N/m), even for very thick grafted layers. But for the samples grafted at higher temperature, much higher adhesion can be obtained. The presence of homopolymer was another factor affecting the adhesion of PE samples. When homopolymer is removed from the surface of the grafted sample, higher adhesion can be obtained. For some samples, the highest peel strength of more than 1000 N/m has been obtained. The low adhesion of the samples grafted at low temperature is attributed to the high branching of grafted chains.     

Thermal behavior of ungrafted and grafted bagasse and wood pulps

The effect of grafting of methyl methacrylate (MMA) and acrylonitrile (AN) on the thermal behavior of the pulp of sugar cane loaded with CaCO₃ and the pulp of a broad-leaved tree has been studied by thermal methods. Different experimental conditions of grafting AN onto the eucalyptus pulp have been used, including both water and organic solvent systems as the medium of reaction. To optimize the grafting of MMA onto wood pulp, the effect of pulp swelling and the contact time of the monomer with the pulp have been examined. Ungrafted as well as grafted cellulose samples with different levels of grafting were characterized by differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA). The CaCO₃ filler makes the pulp of bagasse thermally more stable. The grafting of MMA onto the bagasse or the wood pulps improves their thermal stability. This is not the case for wood grafted with poly(AN). The thermal stability of the grafted and ungrafted samples varies after a few weight percent has been lost. The glass transition temperature (T_g) of the copolymers have been measured and they are in good agreement with the calculated data. © 1993 John Wiley & Sons, Inc.     

Influence of interchange reactions on the crystallization and melting behavior of nylon 6,6 blended with other nylons

The thermal behavior of blends of nylon 6,6, with an amorphous polyamide, Trogamid-T, and a semicrystalline polyamide, nylon 6,12, was studied. The blends were prepared both by solution blending and by melt blending, using a Maxwell extruder and a twin screw extruder. The concentration of the blends ranged from 75% to 95% by weight of nylon 6,6. Annealing the blend samples in the molten state in a differential scanning calorimeter (DSC) produced changes in the melting and crystallization behavior. This was attributed to transamidation reactions occurring between the blend components, leading to the formation of in-situ block copolymers. The length of the blocks decreased with annealing time, as suggested by reduced melting (T_m) and crystallization temperatures (T_c) and heat of fusion values. The changes in thermal behavior were dependent on the blending method, additive concentration, presence or absence of a catalyst, melt annealing time, and the extent of melt mixing. The extent of reaction, measured by the depression in equilibrium melting temperature, was linear with respect to the annealing time. The Trogamid-T containing blends appeared to be “nearly miscible” while those with nylon 6,12 were initially immiscible. The glass transition temperature (T_g) vs. the composition curve of the nylon 6,6/Trogamid-T blends showed a positive deviation from linear additivity, with the single T_g decreasing as a function of annealing time in the melt.     

Electron beam initiated grafting of methyl methacrylate onto polyethylene: Structure and properties

Polyethylene (PE, 100 parts by weight) was mixed with methyl methacrylate (MMA, up to 5 parts by weight) at 120°C and subsequently exposed to electron radiation of different doses (up to 20 Mrad) to prepare PE/MMA graft copolymers. Successful grafting was verified by IR spectroscopy. Gel formation indicated crosslinking. Grafting increased with increasing MMA concentration and increasing irradiation dose. Crystalline melting temperature and percent crystallinity were lower than those of untreated PE. Tensile strength, elongation at break and dielectric constant of grafted samples were measured and discussed.     

Grafting of methyl methacrylate onto silk fibers initiated by tri-n-butylborane

Structural characteristics of the methyl methacrylate (MMA)-grafted silk fibers using tri-n-butylborane as an initiator were analyzed by infrared spectroscopy and differential scanning calorimetry (DSC), and their refractive index and tensile properties were measured. Graft polymerization was promoted by FeCl₃ pretreatment of the silk. The graft yield reached a maximum by the immersion in 4% FeCl₃ solution for 1 min at 25°C. The infrared spectrum of poly(MMA)-grafted silk fibers showed overlapped absorption bands of silk fibroin with the β structure and of the grafted MMA polymer. A grafted silk fiber with graft yield of more than 140% exhibited two endothermic peaks at 321°C and 396°C on the DSC curve, attributed to the thermal decomposition of silk fibroin and grafted poly(MMA) chain, respectively. Refractive index measurements suggested that the molecular orientation and the crystallinity of the silk fiber decreased with increasing graft yield. Electron photomicrographs showed that silk was coated by grafted PMMA. The tensile strength of the grafted silk decreased rapidly by the grafting even at a lower level.     

Thermal analysis of ethylene–propylene copolymer-grafted-glycidyl methacrylate

The thermal properties of ethylene–propylene copolymer grafted with glycidyl methacrylate (EP-g-GMA) were investigated by using differential scanning calorimetry (DSC). Compared to the plain ethylene–propylene copolymer (EP), peak values of melting temperature (T_m) of the propylene sequences in the grafted EP changed a little, crystallization temperature (T_c) increased about 8–12°C, and melting enthalpy (ΔH_m) increased about 4–6 J/g. The isothermal and nonisothermal crystallization kinetics of grafted and ungrafted samples was carried out by DSC. Within the scope of the researched crystallization temperature, the Avrami exponent (n) of ungrafted sample is 1.6–1.8, and those of grafted samples are all above 2. The crystallization rates of propylene sequence in EP-g-GMA were faster than that in the plain EP and increased with increasing of grafted monomer content. It might be attributed to the results of rapid nucleation rate. © 1996 John Wiley & Sons, Inc.     

Effect of graft modification with poly(N‐vinylpyrrolidone) on thermal and mechanical properties of poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. The effect of graft modification with PVP on the thermal and mechanical properties of PHBV was investigated. The thermal stability of grafted PHBV was remarkably improved while the melting temperature (T_m) was almost not affected by graft modification. The isothermal crystallization behavior of samples was observed by polarized optical microscopy and the results showed that the spherulitic radial growth rates (G) of grafted PHBV at the same crystallization temperature (T_c) decreased with increasing graft yield (graft%) of samples. Analysis of isothermal crystallization kinetics showed that both the surface free energy (σ_e) and the work of chain‐folding per molecular fold (q) of grafted PHBV increased with increasing graft%, implying that the chains of grafted PHBV are less flexible than ungrafted PHBV. This conclusion was in agreement with the mechanical testing results. The Young's modulus of grafted PHBV increased while the elongation decreased with increasing graft%. The hydrophilicity of polymer films was also investigated by the water contact angle measurement and the results revealed that the hydrophilicity of grafted PHBV was enhanced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Hexavalent-chromium-initiated graft copolymerization of methyl methacrylate onto cellulose

Graft copolymerization of methyl methacrylate (MMA) onto cotton–cellulose has been carried out using hexavalent chromium Cr(VI) as initiator. Aqueous-methanolic solution of perchloric acid has been chosen as the reaction medium. The effect of monomer, initiator, acid, reaction medium, and temperature on the graft percentage has been found out. The reactions have also been carried out in the presence of polymerization, inhibitors, and retarders, such as hydroquinone and transition metal salts like CuSO₄, FeCl₃, etc. The grafted samples, after exhaustive separation of homopolymers and purification, were subjected to various chemical, mechanical, and thermal testings. The results of various analyses have been compared with the reference, and the improvement in the graft has been evaluated. A suitable mechanism for the grafting processes has been suggested, in accordance with the experimental results.     

Pseudo super-miscibility: Blends of semi-crystalline nylon pairs exhibiting a single Tg and a single Tm

Physical blends of nylon 6 (or nylon 66) homopolymer with random copolymers of nylon 6/nylon 66 or of nylon 6/nylon 12 were melt extruded into films and characterized by Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) techniques. The films containing up to 50–65% of the copolymer exhibited only a single melting temperature (T_m) corresponding to that of the pure homopolymer without any trace of the otherwise crystallizable, lower melting copolymer component. These observations are quite unusual since the binary blends of the homopolymers of nylon 6, nylon 66, and nylon 12 exhibit their characteristic 2 T_m's. That result was significant in that at least 20% nylon 6 units (T_m = 222°C) can be incorporated into nylon 66 (T_m = 262°C) without any depression either in the T_m or in the crystallinity of nylon 66 while retaining its T_m = 262°C as the only melting phase. Also, it has now become possible to develop blend compositions based on ≥ 4 polyamide moieties that exhibit a single T_g, high crystallinity, and a sigle T_m corresponding to the higest melting component. We believe that the observed phenomenon, pseudo super-miscibility, is kinetically driven (i.e., only the higher melting homopolymer crystallizes), rather than thermodynamically or crystallographically, since the structural units originate from polymers that are inherently not isomorphic. In view of the unexpected observation, at least in the field of nylons and its technological significance, we anticipate renewed interest in this area and more definitive understanding to emerge from future studies.     

Interactions in poly(vinylidene fluoride)/poly(methyl methacrylate-co-ethyl methacrylate) blends

Summary The interaction parameters B for blends of poly(vinylidene fluoride) (PVDF) with poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and five methyl methacrylate/ ethyl methacrylate copolymers (PMEMA) were determined by measurements of melting point depression of PVDF. The B values are negative, indicating an attractive intermolecular interaction. The intramolecular interaction parameter between MMA and EMA segments in PMEMA was found to be +3.25 cal/cm³, indicating a repulsive interaction between different monomer segments in the copolymer.     

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.     

Compatibility of nylon 6 and PMMA–oligoamide graft copolymer

PMMA–oligoamide graft copolymers, which were prepared by reacting poly(methyl methacrylate-co-methacryloyl chloride) with oligoamide, were blended with nylon 6. The compatibility was examined by measuring thermal properties such as melting point and crystallization temperature. It was observed that the melting point was significantly depressed as the grafted PMMA was added to nylon 6, suggesting that the blend is a miscible system. It was concluded that hydrogen bonding between amide groups of the two polymers enhanced the miscibility.     

Chemical grafting of 2‐ethyl methacrylate phosphoric acid onto nylon 6 fabric

Graft copolymerization of 2‐ethyl methacrylate phosphoric acid (EMPA) onto nylon 6 fabric is carried out using the K₂S₂O₈/CuSO₄ system as reaction initiators. The most important factors affecting the graft yield are monomer concentration, reaction time and temperature. It was found that the graft yield increased with increasing EMPA concentration, grafting time, and temperature. The grafted nylon 6 fabric shows an increase in moisture regain to reach a maximum of 8.01% with increasing the graft yield to 35.6%. Also, the dyeability with the basic dye was significantly increased due to grafting with EMPA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1357–1361, 2000     

Graft copolymerization of nylon 6 with methyl methacrylate using dimethylaniline/Cu2+ ion system

The ability of dimethylaniline (DMA)/Cu²⁺ ion initiator to induce grafting of methyl methacrylate (MMA) onto nylon 6 was investigated under a variety of conditions. It was found that the graft yield is dependent on the concentration of the Cu²⁺ ion, of DMA, and of MMA. While the graft yield increases as the monomer concentration increases, there are optimal concentrations of DMA and Cu²⁺ ion. Below or above these concentrations, lower grafting occurred. The type of cupric salt also affects grafting to varying degrees. While the presence of CuSO₄ and Cu(NO₃)₂ accelerates grafting, the presence of CuCl₂ offsets the reaction. Increasing the reaction temperature and reaction time favorably influences grafting. Addition of acetic acid enhances grafting, whereas formic acid decreases grafting. Preswelling of nylon with formic acid leaves the susceptibility of nylon toward grafting practically unaltered. Studies of the copolymerization reaction was not confined to the graft yield but was extended to homopolymer formation and total conversion.