Graftability of beaten pulps and acetylated pulps

Ce(IV)-induced polymerization of acrylonitrile with acetylated bagasse and wood pulps, having different acetyl contents, has been investigated. The graft yield is dependent on the acetyl content as well as the origin of the pulp. Increasing the acetyl content of pulps caused a significant decrease in the polymer loading. However, the rate of polymerization of acetylated wood pulp is much higher than that of acetylated bagasse pulp. The ceric consumption during grafting decreases as the acetyl content of the pulp increases. The effect of beating of the pulps, to various degrees of freeness, on their reactivity toward grafting process has also been studied. Generally, the state of cellulose, as defined by its degree of beating, and the origin of the pulp strongly influenced the graft yield. In creasing the beating degree of bagasse pulp resulted in a decrease in graft yield, while beating of wood pulp, to a definite degree, inhibits the polymerization reaction. The consumption of Ce(IV) by the beaten pulps during oxidation is somewhat greater than that consumed by the unbeaten pulps, whereas the consumption during grafting of acrylonitrile onto beaten pulps depends on the initial concentration of ceric solution. Also, the effect of grafting of acrylonitrile onto acetylated wood and bagasse pulps on their strength properties as well as the effect of grafting onto beaten pulps on their properties has been investigated. Grafting of acrylonitrile onto acetylated bagasse pulp decreased its strength properties, but improved its beatability comparatively to those of original pulp (0 acetyl content). On the other hand, grafting of acrylonitrile onto acetylated wood pulp resulted in a great improvement in its strength properties compared to those of grafted unacetylated pulp. Grafted unbeaten pulps gave thinner and weaker paper than the original pulp (without grafting). Beating of bagasse pulp before grafting gave pulp which possessed a higher strength properties, at low °SR, than those of pulp beaten after grafting. Raising the °SR by rebeating the pulp after reaction up to the original value had an adverse effect on the strength. Beating of bagasse pulp before grafting did not accelerate the reaction rate, but it saved some power consumption, since the time required for beating of grafted pulp to a given °SR was lower than that of ungrafted pulp.     

Activating pulp toward acetylation by chemical or mechanical means

Activation of pulps during acetylation, by prior mechanical or chemical treatment, has been investigated. The effect of degree of beating on the acetylation rate of wood and bagasse pulps has been studied. It is found that the acetylation rate of pulps increases when the degree of beating of pulps is increased to a definite degree, after which it slows down. The maximum reactivity of bagasse pulp is obtained at 50°SR, while that of wood pulp is observed at 30°SR. The effect of grafting of acrylonitrile onto bagasse and wood pulps on their reactivity during acetylation has been also studied. The results indicate that grafting of acrylonitrile onto pulps has a favorable effect on their acetylation rate. This is dependent on the degree of grafting as well as the origin of pulp fibers. The most suitable method of activation during acetylation reaction is dependent on the origin of the pulp. The reactivity of bagasse pulp during acetylation is influenced more by beating of pulp, prior to the reaction, than by the grafting of acrylonitrile onto pulp. On the other hand, the acetylation reaction of wood pulp is activated by grafting rather than by beating. Also the effect of the activation process, mechanical or chemical, on the strength properties of the paper sheets produced from acetylated pulps has been investigated. Chemical activation of wood pulp prior to acetylation resulted in pulp with slightly higher strength properties than that activated by mechanical means. But, in the case of bagasse pulp, mechanical activation resulted in a pulp with strength superior to that produced by chemical activation.     

Graft copolymerization of vinyl monomers with modified cotton. II. Grafting of acrylonitrile and methyl methacrylate on acetylated cotton

Ce(IV)-induced polymerization of acrylonitrile and methyl methacrylate with acetylated cotton having different acetyl contents was investigated. The extent of interaction between the cotton and monomer is dependent upon the acetyl content of the former as well as on the reaction conditions. Increasing the acetyl content caused a significant decrease in the graft yield. Increasing the acrylonitrile concentration was accompanied by a substantial increase in the graft yields. The same effect was found with the initiator up to a certain concentration, but beyond it there was a reversal. The rate of grafting increased by rising the temperature and follow the order 60° > 40° > 30°C. The Ce(IV) consumption during grafting is greater than that consumed during oxidation. The consumption of Ce(IV) by the cellulosic materials was favorably influenced by the concentrations of monomer and initiator, time, and temperature. Rates of grafting and Ce(IV) consumption during oxidation of acetylated cottons having different acetyl contents strongly support the postulated mechanism of grafting using the Ce(IV)–cellulose redox system. Ce(IV) oxidation had practically no effect on the acetyl groups (expressed as per cent combined acetic acid) of the modified cotton.     

Graft copolymerization of vinyl monomers on modified cottons. III. Grafting of acrylonitrile and methyl methacrylate on cyanoethylated cotton by the ceric ion method

The interaction of acrylonitrile and methyl methacrylate with cyanoethylated cotton in the presence of ceric ion has been studied under a variety of conditions. Increasing the reaction time, the monomer concentration, and the temperature favorably influences the degree of grafting. The same holds true for initiator concentration up to a certain limit, after which a decrease in the graft yield was obtained. On the other hand, ceric consumption during grafting and oxidation increases by increasing the magnitudes of all these factors. However, the consumption during grafting is always higher than that during oxidation. The graft yields obtained with cyanoethylated cotton are greater than those of the control, being increased by increasing the degree of substitution (D.S.) of the cyanoethylated cotton, suggesting that the cyanoethyl groups afford additional sites of grafting. On the other hand, the ceric consumption during oxidation of cyano-ethylated cotton was much lower than that of the control, being increased also by increasing the D.S., indicating perhaps that ceric ion attacks the cyanoethylated cotton exclusively at the cyanoethyl groups. Based on these findings, a scheme for the mechanism of reaction of a vinyl monomer with cyanoethylated cotton was proposed.     

Cerium-initiated grafting of acrylonitrile onto cellulosic materials

Grafting of acrylonitrile onto native cotton, swollen cotton, viscose, ramie, and hydrocellulose was studied with tetravalent cerium as initiator. The effect of temperature on the graft yields is examined. With ceric ammonium nitrate the grafting yields are found to be higher at 20 and 40 than at 60°C. Ceric ammonium sulfate, on the other hand, produces more grafting at 60 than at 20 and 40°C. The consumption of ceric ions is less, whereas the per cent graft yields are higher for the swollen cottons and viscose than for native cotton. Graft yields are shown to be related to substrate accessibility if the grafting reaction is carried out under conditions that suppress homopolymerization. Oxidation of these celluloses with Ce^IV has also been studied. It is found that more Ce^IV is consumed during grafting than during oxidation of cellulose under identical reaction conditions. Excess Ce^IV consumed in the grafting reaction has been shown to be directly related to extent of homopolymerization, which accompanies grafting. Some data on the storage stability of the free-radical activity produced by oxidation of cellulose with Ce^IV are also reported. It is observed that the cerium-oxidized samples can initiate graft poly merization even after 4–5 hr. if stored in nitrogen.     

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.     

Effect of Some Physical Treatments On the Reactivity of Cotton Stalk Pulp Toward Grafting

The effect of different physical treatments-for example, grinding, beating, and swelling with ethylene diamine-on the reactivity of bleached cotton stalk pulp toward grafting with methylmethacrylate monomer using ceric ion redox system is studied. the effect of monomer concentration and liquor ratio of grafting system on the graftability is also demonstrated. the graftability of treated samples is improved by using a liquor ratio of 50:1 instead of 40:1 for the untreated sample. Optimum graft yield for the beaten samples is obtained at 37°SR. Increasing the °SR of the beaten samples decreases the graft yield till it reaches a value lower than that of the untreated sample at 61°SR. Swelling of cotton stalk pulp with ethylene diamine has a high effect on the reactivity toward grafting. the physically treated pulps are characterized by infrared spectra to clarify the effect of these treatments on the crystallinity index (Cr I) of cotton stalk pulp.     

Grafting of acrylonitrile and methyl methacrylate from their binary mixtures on cellulose using ceric ions

Ceric ion‐initiated grafting on cellulose from a binary mixture of acrylonitrile and methyl methacrylate was carried out in heterogeneous and acidic conditions at 30 ± 0.1°C in a nitrogen atmosphere. To avoid the complexation of water molecules with Ce(IV) ions, the concentration of the nitric acid was taken to be more than the concentration of ceric ions. The effect of the feed concentration, reaction time, and ceric ions concentration on grafting were investigated at a fixed composition. To investigate the effect of monomer–monomer interactions on grafting, the graft copolymerization was also studied, using different feed compositions (f_AN) ranging from 0.25 to 0.80. In this range of feed composition, the synergistic effect of methyl methacrylate molecules has shown an important effect on acrylonitrile monomer and facilitate the incorporation of the acrylonitrile monomer into the grafted chains. The reactivity ratios of acrylonitrile and methyl methacrylate were calculated using the Mayo and Lewis method and were found to be 0.74 and 1.03, respectively. The average sequence lengths of the monomers (m̄M) were found to be dependent on the feed compositions and found to be arranged in alternate fashion in the grafted chains. The probability of the addition of a monomer (P_1,1) to the growing radicals on cellulose ended with its own type of monomer was found to be dependent on the feed composition. The composition of the grafted copolymers, homocopolymers, was determined by IR and elemental analysis for nitrogen. None of the grafted chain on cellulose was found to be made of a single type of monomer. The ceric ion consumption during grafting was found to be independent of the molarity of the feed but shown an appreciable change in the initial few hours of grafting. The variation in the values of the grafting parameters as a function of the reaction conditions is suitably explained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 767–778, 2001     

Graft copolymerization of acrylonitrile onto hemicellulose using ceric ammonium nitrate

The ability of ceric ammonium nitrate to induce graft copolymerization of acrylonitrile onto hemicellulose was investigated. The graft yield depends on monomer and initiator concentrations as well as reaction time and temperature. Chemical analysis of the reaction product of hemicellulose and acrylonitrile in the presence of ceric ammonium nitrate revealed that the ceric ammonium nitrate acted as initiator for polymerization of acrylonitrile and as oxidizing agent for hemicellulose. Proof for grafting of hemicellulose was provided through IR analysis.     

Modification of sago starch by graft copolymerization. Effect of reaction conditions on grafting parameters

Graft copolymerization of acrylonitrile onto sago starch was carried out by a free radical initiating process in which the ceric ion (Ce 4+ ) was used as an initiator. The reaction conditions significantly influence the graft copolymerization. The percentage of grafting, grafting efficiency and rate of grafting were all dependent on the concentration of ceric ammonium nitrate (CAN), acrylonitrile (AN), sago starch (AGU, anhydro glucose unit), mineral acid (H 2 SO 4 ) and the reaction temperature and period. The optimum yield was obtained when the concentrations of CAN, AN, AGU and H 2 SO 4 were used at 9.61×10 ?3 , 0.653, 0.152 and 0.187 mol L ?1 , respectively. The optimum temperature and reaction period were 50°C and 90 min, respectively. The rate of graft copolymerization was examined using the experimental results and the reaction mechanism. The polya1crylonitrile grafted sago starch was characterized by using FT-IR spectroscopy, DSC and SEM analysis.     

Graft copolymerization of vinyl monomers on cellulosic materials

Graft copolymers of acrylonitrile, ethyl acrylate, methyl acrylate, ethyl methacrylate and methyl methacrylate and of acrylonitrile/ethyl methacrylate and acrylonitrile/methyl methacrylate monomer mixtures on carboxymethylcellulose (degree of substitution 0.4–0.5) were prepared by use of ceric ion initiator in aqueous medium. The extent of graft polymer formation was measured in terms of graft level, molecular weight of grafted polymer chains and frequency of grafting as function of ceric ion concentration. It was found that at comparable reaction conditions, the molecular weight and frequency of grafting were not of the same order of magnitude. For the monomer mixtures, the copolymer compositions obtained from the total nitrogen content of the acrylonitrile/alkyl methacrylate copolymer samples showed that a relativity low amount of the acrylonitrile monomeric units were incorporated into the graft copolymer even at high acrylonitrile content of the feed.     

Pierre-gilles de gennes nobel laureate in physics 1991

Grafting of acrylonitrile on to hydrocellulose derived from the hydrolysis of wood pulp has been studied using cerie ammonium nitrate as initiator. The graft yield, the grafting efficiency and the total conversion were found to be highly affected by the various parameters studied including the initiator and monomer concentrations, the polymerization time and temperature. Moreover, the effect of the extent of grafting on the moisture regain property of the hydrolysed wood pulp has been also investigated.     

Methylmethacrylate Grafting onto Cotton Stalk Pulp

Grafting of cotton stalk pulp with methylmethacrylate monomer using a ceric salt redox system is carried out. The effect of different variables—for example, monomer dose, reaction time, reaction temperature, acid concentration, initiator concentration, and liquor ratio—are studied. The effect of the presence of different amounts of residual lignin in cotton stalks pulp on the grafting process is demonstrated. Residual lignin percentage in the pulp plays an important role in determining the grafting rate. A sharp decrease in the grafting rate is observed by increasing the residual lignin percent in pulp from 1.64% to 4.96%. As the residual lignin percentage in the pulp is increased to 12% in pulp, the grafting reaction is nearly stopped. Optimization of the grafting conditions is clarified.     

球形纤维素珠体-AN-AM接枝共聚物的制备

以球形纤维素珠体为原料,丙烯腈(AN)和丙烯酰胺(AM)为单体,硝酸铈铵和过硫酸钾(KPS)为引发剂,制备纤维素珠体-AN-AM接枝共聚物,并通过正交单因素实验,研究了反应温度、引发剂用量、单体用量、反应时间等因素对接枝效果的影响。实验结果表明:当反应温度为60℃,引发剂硝酸铈铵用量为20%,KPS用量为15%(引发剂与单体AN的质量百分比),单体AN浓度为0.75 mol/L,AM浓度为0.28 mol/L,硝酸浓度为0.14 mol/L,反应时间为3 h时,接枝效果最好。此条件下,AN、AM与纤维素的接枝率可达259.4%,接枝效率可达49.40%。     

The xanthate method of grafting. III. Effect of lignin content on the graftability of wood pulp

Several commercial wood pulps of different chemical origin and with various lignin content were copolymerized with acrylonitrile using the xanthate grafting process. A number of experiments were carried out to evaluate the effects exerted by the residual lignin and by other wood components on the grafting reaction. The results obtained show that graft copolymers can be prepared in good yields with pulps containing as much as 23% lignin. With the aim to investigate the effect of lignin in more detail, two series of pulps were prepared by delignification of a crude sulfite pulp and a crude Kraft pulp to different levels of lignin content. Sodium chlorite was used as a bleaching agent. Copolymerization results obtained with these pulps indicate some fundamental differences in behavior between sulfite and Kraft pulps. In both cases, the copolymerization is afflicted by a short inhibition period whose duration, however, does not depend on the lignin content in the pulp.     

Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I

The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.     

研究丙烯腈与淀粉在微波加热时的接枝共聚反应

通过微波加热,研究了以硝酸铈铵为引发剂,淀粉与丙烯腈的接枝共聚反应,探讨了引发剂浓度、单体浓度、反应时间和微波功率对接枝共聚的影响。     

纸浆纤维与丙烯酰胺接枝共聚反应规律及产物结构与性能研究

采用铈离子引发纸浆纤维与丙烯酰胺的异相接枝共聚反应,研究了单体浓度、引发剂浓度、反应温度及时间等对单体转化率与接枝率的影响。用ＩＲ、ＴＧ、ＤＳＣ、ＳＥＭ、Ｘ－射线衍射,偏光显微镜等手段对接枝物的结构和性能进行了表征。结果表明,接枝物的热稳定性高于原纤维,接枝主要发生在纤维的表面和无定形区,对它的结晶性没有损害     

Synthesis and physicochemical properties of graft copolymer of corn starch and acrylamide

Graft copolymerization of corn starch with acrylamide using ceric ammonium sulphate/citric acid initiation system has been studied under nitrogen atmosphere in aqueous medium. The grafting parameters are favored by increasing monomer concentration and reaction time but are affected by higher concentration of initiator and high temperature. The optimum conditions established for grafting were as follows: the concentration of initiator, 0.003 mol/L; the concentration of citric acid, 0.03 mol/L; monomer/starch, 1:1 feed ratio (w/w); reaction time, 3.0 h; and temperature, 35°C. The extent of grafting was examined by Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. Both swelling power and solubility increased with the increase in temperature. Graft copolymerization increased swelling power and reduced solubility. Rapid visco‐analyzer pasting profile was studied. Graft copolymerization of corn starch results in high pasting temperature, high peak viscosity, and setback as compared with native starch. Breakdown was retarded at low percentage grafting (6.60%) but increased at high percentage grafting (60.27%). POLYM. COMPOS. 28:47–56, 2007. © 2007 Society of Plastics Engineers     

Characterization of cationic polyacrylamide‐grafted starch flocculant synthesized by one‐step reaction

Cationic polyacrylamide‐grafted starch (St‐g‐CPAM) flocculant was prepared by using corn starch and acrylamide (AM) as monomers, dimethyl diallyl ammonium chloride (DMDAAC) as cationic monomer through solution polymerization. The effects of initiator, reaction temperature, and monomer concentration on flocculation, the efficiency of grafting, and the yield of grafting were investigated. The results show that the optimal conditions of the polymerization are as follows: the concentration of ceric ammonium nitrate is 0.5%, the reaction temperature is 60°C, the concentration of total monomer is 20%, and the monomer ratio between AM and DMDAAC is 7 : 3. The flocculation capability was characterized by turbidity reduction. The thermal behavior, chemical structure, and microstructure of St‐g‐CPAM were also investigated by thermal gravimetric, IR, and SEM analyses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011