Effects of starch alkenylsuccinylation on the grafting efficiency,paste viscosity,and film properties of alkenylsuccinylated starch‐g‐poly(acrylic acid)

Commercial cornstarch was alkenylsuccinylated with alkenylsuccinic anhydride to different degrees of substitution (DS) and then the products were graft‐copolymerized with acrylic acid for investigating the effects of starch alkenylsuccinylation on the graft copolymerization with vinyl monomer, as well as on paste viscosity and film properties of alkenylsuccinylated starch‐g‐poly(acrylic acid) (ASS‐g‐PAA). The number of carbon atom of alkenyl in alkenylsuccinates considered was 8 and 12, corresponding to octenylsuccinylation and dodecenylsuccinylation of starch, respectively. The graft copolymerization was accessed by grafting efficiency, grafting ratio, and conversion of monomer to polymer, and the film properties of ASS‐g‐PAA considered included tensile strength, breaking elongation, and work‐to‐break. Experimental results demonstrated that the alkenylsuccinylation showed marked effects on the copolymerization, paste viscosity, and film properties. It resulted in increased grafting efficiency, stable paste viscosity, and strong starch film. Carbon‐chain length of the alkenyl and DS value of the alkenylsuccinates also exhibited evident effects on the copolymerization and film properties. Octenylsuccinylation of starch before the copolymerization was superior to dodecenylsuccinylation in improving the efficiency and film properties. Low levels of octenylsuccinylation could be utilized to increase the efficiency of the copolymerization and improve the properties of starch film.     

Sorption of ethyl acetate and d‐limonene in poly(lactide) polymers

Poly(lactide) (PLA) polymers have garnered increased attention in the last few years as food packaging materials because they are environmentally friendly polymers. As the production of PLA increases and price per pound drops, PLA is becoming a growing alternative as a green food packaging material. In this research, the organic vapor barrier properties of commercially available PLA polymers were studied. Gravimetric sorption tests in PLA films were carried out, and the diffusion (D), solubility (S) and permeability (P) coefficients for ethyl acetate and d‐limonene in PLA were determined. For ethyl acetate, values of P = 1.22 × 10^?17 kg m m^?2 s^?1 Pa^?1, D = 2.63 × 10^?15 m² s^?1, and S = 4.62 × 10^?3 kg m^?3 Pa^?1) at 45 °C and a partial pressure of 12 654 Pa were obtained. For d‐limonene, no trace was detected after 21 days of testing at 45 °C and 258 Pa, which indicates a permeability coefficient lower than 9.96 × 10^?21 kg m m^?2 s^?1 Pa^?1. Poly(lactide) polymers demonstrated good aroma barrier to ethyl acetate and d‐limonene, and will most likely be good aroma barriers. PLA is not likely to promote flavor loss by either permeation or scalping. Copyright © 2005 Society of Chemical Industry     

Effects of starch acryloylation on the grafting efficiency,adhesion, and film properties of acryloylated starch‐g‐poly(acrylic acid) for warp sizing

In order to enhance the grafting efficiency of graft copolymerization of granular cornstarch with acrylic acid (AA) for improving the adhesion and film properties of starch‐g‐poly(acrylic acid) used as sizing agent, the esterification of hydrolyzed starch with acryloyl chloride was applied before graft copolymerization. The influence of three common initiators on the copolymerization were also studied. The initiators included ceric ammonium nitrate [Ce(NH₄)₂(NO₃)₆], hydrogen peroxide/ferrous ammonium sulfate [H₂O₂/FeSO₄ · (NH₄)₂SO₄], and potassium persulfate/sodium bisulfite [K₂S₂O₈/NaHSO₃]. It was found that acryloylation of starch before the copolymerization was an effective method for substantially enhancing the grafting efficiency and improving the performances such as adhesion‐to‐fibers and mechanical properties of grafted starch film. The acryloylation could increase the efficiency to 67–81% when the degree of substitution (DS) of acryloylated starch ranged from 0.010 to 0.036. The adhesion to polyester and cotton fibers reached their maximum at DS = 0.010 and 0.022, respectively. Strong and tough film was obtained when the DS value was in a range of 0.010–0.022. H₂O₂/FeSO₄ · (NH₄)₂SO₄ redox system was more appropriate for initiating the copolymerization of acryloylated starch with AA.     

A facile approach for controlled synthesis of hydrophilic starch‐based nanoparticles from native sago starch

A facile approach for the preparation of hydrophilic starch‐based spherical nanoparticles from native sago (Metroxylon sagu) starch using the drop‐wise solvent exchange method was reported. Starch‐maleate monoester (SM) was initially synthesized from native sago starch and maleic anhydride in an aqueous medium, and SM nanoparticles was subsequently precipitated in absolute ethanol under controlled conditions. The present study was focused mainly on modulating of the solvent and non‐solvent systems to prepare SM nanoparticles of different morphologies. The pH of the solvent system and the nature of surfactants being added into the solvent system could influence the morphology of regenerated SM nanoparticles. SM nanoparticles of discrete and spherical shape were regenerated from a basic SM sample solution, or an acidic sample solution in the presence of an appropriate surfactant. SM nanoparticles with mean diameter of about 250 nm was obtained by precipitation in absolute ethanol in the presence of Brij 35 as the surfactant.     

Water sorption kinetics of superabsorbent hydrogels of saponified cassava starch‐graft‐poly(acrylamide)

Superabsorbent polymers (SAPs) are hydrophilic polymeric networks that can absorb, swell and retain large quantity of water and other physiological fluids. In this paper, the water sorption pattern and kinetics of cassava starch based SAP hydrogels were studied under different conditions of swelling such as soaking duration, pH, presence of salts, and particle size of the hydrogel. The kinetics was studied using Voigt‐based viscoelastic model to determine the rate parameter and the swelling rate (SR). It was noted that under all conditions, the water sorption followed a second order kinetics. The absorbency was directly proportional to the rate of swelling. But when the sample was allowed to swell in aqueous solutions of CaCl₂ and AlCl₃, the absorbency as well as the SR was irregular. The particle size also had significant effect on water absorption by the SAP and the polymer with smaller particles showed more absorption than those with larger particle size. The solvent induced phase transition of the superabsorbent hydrogel was also studied.     

Microwave‐accelerated Synthesis and Characterization of Potato Starch‐g‐poly(acrylamide)

Using a very low concentration of potassium persulfate as initiator, acrylamide could be efficiently grafted onto potato starch under microwave irradiation and for the grafting O₂ removal from the reaction vessel was not required. Under optimal conditions, grafting and efficiency observed were 160% and 89%, respectively. Grafted starch was characterized by using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). It was observed that the microwave irradiation could significantly accelerate the synthesis of starch‐graft‐poly(acrylamide), because under identical conditions no grafting was observed in a conventional procedure. Viscosity, shear stability and water/saline solution retention of the microwave‐synthesized grafted starch were studied and compared with that of the parent starch.     

Synthesis,characterization and swelling behaviour of superabsorbent polymers from cassava starch‐graft‐poly(acrylamide)

Superabsorbent polymers (SAPs) were prepared from cassava starch by graft copolymerization of acrylamide on to starch using ceric ammonium nitrate (CAN) as free radical initiator, followed by alkali saponification. The reaction parameters such as concentration of acrylamide, concentration of CAN, temperature, and duration of polymerization reaction were optimized for maximum water absorbency using a 4‐factor 3‐level Box‐Behnken design. The highest values of percentage grafting and absorbency obtained were 174.8% and 425.2 g/g, respectively. The polymers were characterized by determination of grafting efficiency, N‐content, acrylamide content, FTIR analysis, SEM and XRD analyses. Thermogravimetric analysis (TG) showed that the SAP has higher thermal stability. The rate of water absorbency and the swelling behaviour of the SAP under different conditions of pH, and different salts were determined. The de‐swelling pattern of the hydrogels over different time durations was also determined.     

氢键控制与聚醋酸乙烯醇解纺丝

介绍聚乙烯醇中分子间、分子内氢键定义和表征方法 ,讨论了残留的羧基与聚乙烯醇的构象及结晶度对氢键形成的影响 ,分析了聚醋酸乙烯分步醇解纺丝和直接醇解纺丝中氢键的形成与结晶度。指出 :有效控制氢键形成是制备高强高模PVA纤维的关键。     

Microwave assisted synthesis and characterization of Sago starch‐g‐acrylamide

In the present investigation, sago starch was modified through microwave assisted chemical synthesis using acrylamide as grafting monomer. Grafted copolymer was characterized by fourier transform infra red spectroscopy (FTIR), scanning electron microscopy (SEM), X‐ray powder diffractometer (XRD) and thermo gravimetric analysis (TGA). Swelling study was also performed at various temperatures to access its suitability in diverse industrial application. The optimum reaction conditions were found as follows: starch, 1 g; acrylamide (AMD), 5 g; microwave power, 600 W, reaction time, 3 h. Grafting on the starch backbone confirmed by FTIR spectral analysis, while XRD confirmed formation of more crystalline structure after AMD grafting. TGA analysis showed formation of more thermostable copolymer after grafting, while swelling study proved its suitability for various industrial applications due to its extensive swelling at higher temperatures.     

Enzymatic synthesis of rose aromatic ester (2-phenylethyl acetate) by lipase

BACKGROUND: 2‐Phenylethyl acetate (2‐PEAc) is a highly valued natural volatile ester with a rose‐like odour that is widely used to add scent or flavour to cosmetics, soaps, foods and drinks. In this study, 2‐PEAc was synthesised enzymatically by transesterification of vinyl acetate with 2‐phenethyl alcohol catalysed by immobilised lipase (Novozym^® 435) from Candida antarctic RESULTS: Response surface methodology and a three‐level/three‐factor Box–Behnken design were used to evaluate the effects of time, temperature and enzyme amount on the molar conversion % of 2‐PEAc. The results showed that temperature was the most important variable. Based on the ridge max analysis results, optimum enzymatic synthesis conditions were predicted as a reaction time of 79 min, a temperature of 57.8 °C and an enzyme amount of 122.5 mg. The predicted and experimental yields were 86.4 and 85.4% respectively. CONCLUSION: Three immobilised lipases were screened and 15 reaction conditions were tested in order to find the combination for maximum yield. The optimisation of 2‐PEAc synthesis catalysed by Novozym^® 435 was successfully developed. The kinetic study of this transesterification reaction showed that it followed an ordered ping‐pong bi‐bi mechanism without any inhibition by reactants. Copyright © 2012 Society of Chemical Industry     

Preparation,characterization, and water resistance of cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion

Cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion (CAS‐g‐poly(St‐BA)) was synthesized by graft copolymerization of styrene (St) and butyl acrylate (BA) onto CAS using FeSO₄–H₂O₂ redox initiator. The maximum graft of 55.68% was derived when H₂O₂ concentration, monomer concentration, and St/BA ratio were 9%, 130%, and 1:1, respectively. The results obtained from FTIR, NMR (H¹ NMR and C¹³ NMR), XRD, SEM, and thermogravimetric analysis (TGA‐DTG) confirmed graft copolymerization of St and BA onto CAS. And it was demonstrated that film‐forming properties of starch were greatly improved via grafting St and BA onto starch. It was also found that paper sized with CAS‐g‐poly(St‐BA) exhibited higher ring crush index and bursting strength than paper sized with cationic potato starch (CS) and CAS, as well as much lower water absorption, which is further verified by contact angles results.     

响应面法优化醇溶性黑木耳多糖-聚醋酸乙烯酯接枝反应工艺

以醇溶性黑木耳多糖为原料,采用过硫酸铵-碳酸氢钠氧化还原引发体系,进行黑木耳多糖(AAP)/聚醋酸乙烯酯(PVAc)乳液接枝聚合反应。在单因素实验的基础上,以接枝温度、单体配比浓度、接枝时间、引发剂添加量为自变量,共聚物接枝率为响应值,采用响应面法研究各自变量的交互作用,确定了黑木耳醇溶性多糖接枝聚合最佳工艺:温度60℃,反应时间2.5h,多糖与PVAc比例为1:3,引发剂量占PVAc质量的4%,在该条件下聚合物接枝率达37.6%。实验结果为高分子天然产物研究提供理论依据。     

Inverse Emulsion of Starch‐graft‐Polyacrylamide

An inverse emulsion of cationic starch‐graft‐polyacrylamide was prepared by inverse emulsion polymerization and a subsequent Mannich reaction. The copolymerization was carried out using potassium persulfate as initiator. The reaction conditions and factors affecting emulsion stability were studied. Experiments showed that a high solids content, a high cationic degree and a stable latex can be obtained under the following condition: A molar ratio starch/acrylamide/formaldehyde/dimethylamine of 0.11:1:1:1.2; a stable inverse emulsion system; graft copolymerization of starch and acrylamide for 2‐3 h at 50 °C; pre‐formation of an aldehyde‐amine adduct, which is subsequently dropped into an inverse emulsion of starch‐graft‐polyacrylamide. The reaction temperature was 45 °C, the reaction time was 3‐4 h, and the pH was 5.5.