Thermal behavior of graft copolymers of cotton cellulose and acrylate monomers

Cotton cellulose yarn was grafted with methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate at various percentages of grafting. The effects of concentration of the initiator, concentration of the acid, and of temperature on grafting was studied and the mechanism discussed. The effect of reactivity of the monomer on the percentage graft-on is pointed out. Thermal behavior of natural and grafted cotton yarn was studied using dynamic thermogravimetry in air at a heating rate of 6°C/min up to a temperature of 500°C. The thermal stabilities of the samples grafted with various acrylate monomers to various percentages of grafting were computed from their primary thermograms by calculating the values of IDT, IPDT, and E^*. The results show that the thermal stability increases with increase in graft-on per cent, and the thermal stabilities of natural cotton and cotton grafted with different monomers are in the order ethyl > methyl > natural cellulose > methyl methacrylate > n-butyl acrylate.     

Photolysis of vinyl ketone copolymers. 4: Macromonomeric products from photolyses of copolymers of styrene and methyl acrylate with methyl vinyl ketone

Some statistical copolymers of styrene and methyl vinyl ketone, prepared by free radical copolymerization, have been photolyzed in benzene solution using u.v. light of wavelength 300 or 350 nm. It is confirmed by n.m.r. spectroscopy that the oligomeric products so obtained have unsaturated end-groups with structures resembling that of -methyl styrene, as would be expected on the basis of a predominantly Norrish type II photolysis mechanism. The molecular weights of the oligomers slightly exceed those expected from the copolymerization statistics, indicating probably that some slight cross-linking or repolymerization of end-groups accompanies the chain scission. Although not homopolymerizable, the unsaturated styrene oligomers produced by photolysis can be free-radically copolymerized with methyl acrylate, demonstrating that they behave as macromonomers. A copolymer of methyl acrylate with methyl vinyl ketone also gives fragments with unsaturated end-groups on photolysis, but here the accompanying cross-linking or end-group repolymerization is more dominant, leading to oligomeric products with extremely broad molecular weight distributions.     

Extrusion behavior of starch graft copolymers: Starch-g-polystyrene and starch-g-poly(methyl acrylate)

Starch-g-polystyrene and starch-g-poly(methyl acrylate) copolymers were synthesized and extruded without separating homopolymer PS or PMA. The extrusion behavior resembled that of thermoplastic melts in that these products were shear thinning and exhibited significant extrudate swelling and entrance pressure losses in capillary flow. These and other observations indicate that the materials comprise deformable polymer-grafted starch particles suspended in the corresponding homopolymer melt. Flow is apparently by superparticle, rather than continuum melt mechanisms.     

木薯淀粉/VAc-MA接枝共聚物的合成研究

通过正交试验设计,研究醋酸乙烯酯和丙烯酸甲酯两种单体接枝改性木薯淀粉的影响因素。利用SAS统计分析得出适宜的工艺条件:引发剂浓度16mmol.L-1,总单体浓度1.45mol.L-1,两单体配比(VAc/MA)为30/70,反应温度65℃,反应时间5h。采用红外光谱对该接枝共聚物结构进行了分析。     

Synthesis and characterization of vegetable tannin-vinyl graft copolymers part I. Cutch-poly(methyl acrylate) graft copolymers

New graft copolymers were synthesized by grafting methyl acrylate onto cutch, a vegetable tanning agent, in acetic acid medium with hydrogen peroxide as the initiator. The graft copolymers were characterized by infrared spectroscopy and thermogravimetric analysis. The dependence of the percentage of grafting, monomer conversion, efficiency of grafting and rate of grafting on the concentrations of initiator, acetic acid, and cutch were investigated. The optimum experimental conditions for grafting were obtained. A probable mechanism of grafting was also proposed.     

Synthesis of graft copolymers of binary vinyl monomer mixtures onto acetylated Saccharum spontaneum L and characterization

Methylmethacrylate (MMA) + acrylamide (AAm), MMA + acrylonitrile (AN), and MMA + acrylic acid (AA) binary vinyl monomer mixtures were graft copolymerization onto acetylated Saccharum spontaneum L, was carried out and maximum graft yield (185.6 %) was found with MMA+AAm binary mixture. Synthesized graft co‐polymers were characterized with FT‐IR spectrophotometry, scanning electron microscopy (SEM), thermal analysis TGA/DTA/DTG, and X‐ray diffraction (XRD) techniques. Thermal stability of Ss‐g‐poly(MMA + AAm) was found to be more than that of natural, acetylated S. spontaneum fiber and other graft copolymers. Although on grafting, percentage crystallinity and crystallinity index were found to decrease but graft copolymers were found to exhibit more moisture, chemical, and thermal resistance. Also, it can be observed that the surface of the grafted fibers is highly rough in comparison with the ungrafted fiber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Vinylic graft copolymers of cellulose. I. Effects of monomer concentrations and crystallinity index of cellulosic substrate on grafting vinyl acetate onto cotton

Graft copolymerization of vinyl acetate (VA) and methyl acrylate (MA) on cotton cellulose was initiated by the Ce (IV) ion, and ungrafted vinylic polymer was separated from the graft copolymer by acetone extraction. The influence of the ratio aqueous initiator solution volume/monomeric volume (V_aq/V_mon), vinyl acetate volume/methyl acrylate volume (V_VA/V_MA), and the cellulose crystallinity index (CI) on the grafting reaction were studied. To modify the crystallinity of cellulose, native cotton was treated with NaOH in the concentrations 10, 15, and 20% (mercerized). The viscosimetric average molecular weight (M_v), the polymerization degree (PD), and the crystallinity index proposed by Nelson and O'Connor (CI) were determined for native and NaOH-treated cotton. The polymeric side chains grafted were separated from the cellulose backbone by acid hydrolysis in 72% H₂SO₄. The viscosimetric average molecular weight (M_v) was determined, and the number of vinylic chains per cellulosic chain (graft frequency, GF) were calculated. The grafting percentage, %G, was higher for most amorphous cellulose and for a higher methyl acrylate percentage (%MA) in monomeric reaction mixtures (VA-MA). The V_aq/V_mon ratio that yields the highest %G was 70/30. The increase of the %G with the %MA in the VA–MA monomeric mixture seems to be due to both an increase in the length of vinylic grafted chains (as shown by its M_v) and the number of grafted chains (GF). The increase in the %G when the crystallinity index (CI) of the cellulosic substrate decreases seems to be due to an increase in the length of the vinylic grafted chains, but not to an increase in the number of grafted chains, since the M_v increases and GF decreases when the CI of cellulose decreases.     

Copolymerization of pentachlorophenyl acrylate with vinyl acetate and ethyl acrylate. Polymer-bound fungicides

Copolymers of pentachlorophenyl acrylate (M₁) with both vinyl acetate and ethyl acrylate were prepared (in benzene at 60°C initiated by t-butyl peroxypivalate) at a variety of M₁/M₂ ratios. The reactivity ratios for the vinyl acetate (M₂) copolymerizations were r₁ = 1.44 and r₂ = 0.039, while for ethyl acrylate copolymerizations r₁ = 0.21 and r₂ = 0.88. The glass transition temperatures were obtained as a function of the M₁/M₂ ratio. The values of T_g for the copolymers fell between those of poly(pentachlorophenyl acrylate) and either poly(vinyl acetate) or poly(ethyl acrylate). A series of bulk copolymers with low pentachlorophenyl acrylate content were studied as biocidal coatings using accelerated growth agar dish tests inoculated with Aspergillus sp., Pseudomonas sp., Alternaria sp., and Aureobasidium pullulans. The copolymers retarded or prevented growth but did not give a zone of inhibition around the coatings. Pentachlorophenol, when added to coating polymers, did exhibit a zone of inhibition due to migration of this biocide into the agar medium.     

Effect of cardinyl acrylate on thermal behavior of methyl methacrylate copolymers

Cardinyl acrylate (CA), prepared by the reaction of acryloyl chloride and cardinol, was copolymerized with methyl methacrylate (MMA) in bulk at 80°C using 2% benzoyl peroxide as an initiator. The copolymer composition was determined by ¹H-NMR spectroscopy. Three copolymer samples containing 0.0048–0.0838 mol fraction of cardinyl acrylate were obtained. A significant improvement in the thermal stability of MMA was observed by incorporating 0.0048–0.0838 mol fraction of CA in the backbone. The activation energy for decomposition in the temperature range 350–480°C for copolymers was higher than PMMA. © 1992 John Wiley & Sons, Inc.     

Sequence determination of vinyl acetate–methyl acrylate copolymers by NMR spectroscopy

Vinyl acetate/methyl acrylate (V/M) copolymers were prepared by free-radical solution polymerization in benzene. Copolymer compositions were obtained from ¹H-NMR spectroscopy. Reactivity ratios for the copolymerization of V with M were calculated using the Kelen-Tudos (KT) and the nonlinear error in variables (EVM) methods. The reactivity ratios obtained from the KT and EV methods are r_V = 0.04 ± 0.03 and r_M = 7.28 ± 2.88 and r_v = 0.04 ± 0.01 and r_M = 7.28 ± 0.37, respectively. The microstructure was obtained in terms of the distribution of V- and M-centered triad sequences from ¹³C{¹H}-NMR spectra of copolymers. Homonuclear ¹H-2D-COSY and 2D-NOESY NMR were used to determine the most probable conformer for the V/M copolymer. The copolymerization behavior of the V/M copolymers as a function of conversion is also reported. © 1994 John Wiley & Sons, Inc.     

Grafting of vinyl acetate onto chitosan and biocidal activity of the graft copolymers

The reaction process of polycarbosilane (PCS) fiber cured by cyclohexene vapor has been studied and compared with that of PCS fiber cured by air. The influence of curing temperature on Si? H bond reaction degree and gel content, the structure and composition of PCS were investigated by FTIR, EA, TGA, NMR, and GC‐MS. The results showed that, Si? H bond in the molecular structure of PCS reacted during cyclohexene curing process and the reaction degree increased when the curing temperature increases. Simultaneously, gel content of PCS fiber rapidly increased till PCS fiber became infusible. Si? H radical and Si? CH₂ radicals formed Si? CH₂? Si crosslinking of PCS molecules through the agency of cyclohexene. Some cyclohexyls linked to principal chain of PCS, which was proven by ¹³C‐CPMAS‐NMR, and broke off, and cyclohexane and some monosilane are generated as byproducts when temperature increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermal behavior of cotton grafted with vinyl monomers individually and in mixture compositions

Thermal analysis of cotton samples grafted with acrylamide, acrylonitrile, methyl acrylate, and methyl methacrylate individually and in mixture compositions has been carried out. Additional endothermic peaks in the DTA curves characteristic of the polymers grafted were observed. Graft copolymerization of acrylamide and acrylonitrile makes cotton thermally more stable, while in the case of methyl acrylate-and methyl methacrylate-grafted cottons, the initial decomposition starts at higher temperatures, but subsequent decomposition is faster and the overall thermal stability is lowered. In the case of binary mixtures of acrylamide and acrylonitrile, inception of decomposition starts earlier, but subsequent decomposition takes place at much higher temperatures than for individual monomer-grafted cottons. Interaction between monomers during grafting is indicated. When fabric samples containing polyacrylamide grafts are methylolated and subsequently cross-linked, there is a reduction in the thermal stability of the treated cotton.     

Thermal behavior of methacrylic acid–ethyl acrylate copolymers

The thermal degradation behavior of copolymers of methacrylic acid (81.5–17.4 mol%) was studied using thermogravimetry (TGA) and differential scanning calorimetry (DSC) and the degradation products were analyzed using mass spectroscopy and DSC–FTIR. From mass spectroscopy, it was observed that in the copolymers the main degradation products obtained below 280°C included water, ethanol, and methanol, whereas at higher temperature (up to 400°C), CO₂, CO, and small olefins were liberated. Elimination of water and ethanol is attributed to anhydride formation, which is believed to result from two routes: (a) anhydride formation involving adjacent acid groups and (b) anhydride formation involving adjacent acid and ester groups. An endothermic transition in the DSC and percent weight loss in the TGA in the same temperature range (140–280°C) support the above proposal. An increase in weight loss with increase in EA content of the copolymer confirms the participation of EA in the anhydride formation. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of graft copolymers of ethyl acrylate/acrylamide mixtures onto starch

Graft copolymerization of ethyl acrylate/acrylamide onto corn starch using potassium permanganate–citric acid initiation system was investigated. Major factors affecting the polymerization reaction were thoroughly investigated in terms of initiator concentration, monomer concentration, polymerization time, polymerization temperature, and starch/liquor, and the obtained results implied that the polymer yield which were expressed by total monomer conversion, grafting ratio, and grafting efficiency were determined by these factors. The optimum reaction conditions were as follows: starch, 30 g; potassium permanganate (based on weight of starch), 0.1%; citric acid (based on weight of starch), 0.5%; ethyl acrylate, 20%; acrylamide, 0.4 g; time, 3 h; temperature, 40°C; starch/liquor, 1:3. We concluded that the initiator of potassium permanganate–citric acid system could be used as a cheap initiator in manufacturing the starch graft copolymer. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Block copolymers obtained by free radical mechanism. II. Butyl acrylate and methyl methacrylate

Block copolymers were synthesized using methyl methacrylate and butyl acrylate as the monomers and a multifunctional initiator, di-t-butyl 4,4'-azobis(4-cyanoperoxyvalerate). The polymerizations for the formation of the block copolymers were carried out in two stages. First the poly(methyl methacrylate) polymeric initiator was synthesized and isolated. In the second stage, the thermallyactivated azo group in the polymer backbone initiated the polymerization of butyl acrylate. Upon termination by combination a tri-block results. Selective solvent fractionation was used to separate the block from the homopolymers.     

Graft-copolymerization of starch with acrylamide,II. Thermal behaviour of graft copolymers

Thermal behaviour of starch-graft-polyacrylamide (S-g-PAM) copolymers was evaluated. Grafting of polyacrylamide onto starch lowers the initial decomposition temperature. However, the over-all stability as assessed by the shape of thermogravimetric curve and integral procedural decomposition temperature increased with an increase in % graft-on.     

High-temperature coupling of high-speed GPC with continuous viscometry. II. Ethylene–vinyl acetate copolymers

An application of the high temperature coupling of a gel permeation chromatograph with a home-made continuous viscometric detector is described. It concerns the comprehensive characterization of ethylene–vinyl acetate copolymers. Suitable chromatographic conditions are chosen to enable a correct use of the universal calibration concept. Through analysis of poly(vinyl acetate) fractions and commercial polyethylene samples, a comparison is made with the results of classical measurements. Average molecular weights as well as intrinsic viscosity appear to be in good agreement within experimental error, which proves the system for the characterization of random ethylene–vinyl acetate copolymers. In attempting to obtain a reliable estimate of long chain branching frequency λ, a series of commercial samples has been selected, with the vinyl acetate weight fraction within the range 0–45%. As a rule, experimental viscosity law exhibits two parts, a straight line with a Mark–Houwink exponent 0.7 in the low molecular weight region and a curvature, well smoothed by a third-degree polynomial regression. Consequently, long chain branching does not appear before a limiting molecular weight of about 50,000. Beyond this limit, λ is 0.5 × 10^?4, with no dependence on molecular weight, which resembles low density polyethylene.     

Microstructure analysis of methyl acrylate/methyl methacrylate copolymers by two‐dimensional NMR spectroscopy. II

In the present article, a comprehensive two‐dimensional heteronuclear multi bond correlation (HMBC) spectral analysis of methyl acrylate (A)/methyl methacrylate (B) copolymers is reported. The methylene carbon and methine carbon resonances assigned from the 2D HSQC spectroscopy were established by analyzing the two and three bond order couplings with α‐methyl protons, methylene protons, and methine protons. Quaternary carbon resonances of the B unit were assigned by investigating the two bond order couplings with α‐methyl protons and methylene protons. Assignments of carbonyl carbon resonances based on the analysis of three bond couplings with α‐methyl protons and methylene protons are reported. The analyses present comprehensive assignments of the carbonyl carbon resonances showing the critical contribution of 2D HMBC spectroscopy in the indirect analysis of carbon resonances. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006