TGA analysis of γ‐irradiated linear low‐density polyethylene

Linear low‐density polyethylene (LLDPE), based on butene‐1 or hexene‐1, was irradiated with γ‐rays under vacuum or in the presence of air. The study focused on the influence of the dose rate and the γ‐dose on the thermal properties of LLDPE. Differential scanning calorimetry, thermogravimetric analysis (TGA), and TGA/FTIR techniques were used to address the thermal behavior as a result of γ‐irradiation. During this irradiation, competition between crosslinking and scission reactions, subsequent to oxidation reactions, occurred in the polymeric material, which strongly depends on the experimental conditions. A decrease of the crystallinity for γ‐irradiated samples was observed in particular for samples irradiated under vacuum. This observation may be explained by increased hindrance of segment mobility due to crosslinking reactions that prevent crystal growth. TGA investigations revealed an enhancement of the thermal stability for samples irradiated under vacuum but not for those irradiated in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2790–2795, 2006     

Optimization of preparation conditions of carboxymethyl potato starch through orthogonal experimental design

To optimize the preparation conditions of carboxymethyl potato starch (CMPS), the effects of relevant factors on viscosity (η) of 2% CMPS aqueous solution and degree of substitution (DS) were investigated. These condition parameters included etherification temperature, alkalization and etherification time, water content in the mixed solvent, ratio of liquid volume to starch mass, molar ratio of sodium hydroxide to monochloroacetic acid, and molar ratio of monochloroacetic acid to anhydroglucose unit. After individual parameter influencing η and DS was researched one by one, an orthogonal experiment of L₁₈ (2 × 3⁷) was designed to identify the main factors affecting them. In light of range analysis, the comparative importance of factors impacting η and DS was obtained, separately. Results of variance analysis showed that the most effective factor to control DS was etherification temperature, whereas the influences of all factors on η were not significant. Meanwhile, η and DS of the optimized final product were found to be 12,000 mPa.s and 0.68, respectively. In addition, the structure of CMPS was characterized by Fourier transform infrared (FTIR) spectrophotometer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

复合变性淀粉合成与性能评价

以马铃薯淀粉为原料,环氧氯丙烷为交联剂,氯乙酸为醚化剂,采用溶剂法及“酸前法”制备工艺合成了高黏度交联一羧甲基化复合变性淀粉（CCMS）。确定了合成CCMS的最佳组合工艺参数。结果表明：当淀粉、氯乙酸及氢氧化钠物质的量比为1：0．57：1．01,交联剂用量为干淀粉质量的0．67％,乙醇纯度90．0％,反应温度65℃,反应时间70min时,合成的CCMS具有较好的抗剪切性能和较高的黏度,不同钻井液体系中均有较好的增黏性、降滤失性、抗高温性和抗盐性,高温老化后仍具有良好的降滤失能力。     

Crosslinking of corn starch with sodium trimetaphosphate in solid state by microwave irradiation

Corn starch was crosslinked with sodium trimetaphosphate (STMP) in solid state under microwave irradiation to improve the degree of substitution (DS) and decrease the reaction time. The effects of modification factors on the crosslinking of starch were systematically studied. It was found that the microwave irradiation provided a convenient and efficient method to prepare crosslinked starch with sufficient DS. The DS value of crosslinked starches obtained by microwave irradiation was significantly improved and the reaction time was also dramatically decreased to achieve an appropriate DS value by microwave irradiation, when compared with using traditional method. The high microwave power provided faster reaction kinetics to obtain the desired DS value at an identical reaction condition. If the reaction temperature is lower than the decomposition temperature of crosslinked starch, the higher DS value can be achieved at the higher microwave power. It was detected that the DS data obtained by reacting intermittently was higher than those by reacting continuously. It was also noticed that DS data varied drastically with the increasing of the amount of STMP and sodium carbonate. The swelling ratio of crosslinked starch in water was lower than that of native starch because of the nongelatinization of highly crosslinked starch. SEM analysis indicated that the crosslinking of corn starch by microwave irradiation caused no significant changes in the microstructure of starch granules. Light microscope analysis also showed the uniformity of so‐prepared crosslinked corn starch applying microwave irradiation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5854–5860, 2006     

Synthesis and properties of starch grafted poly[acrylamide‐co‐(acrylic acid)]/montmorillonite nanosuperabsorbent via γ‐ray irradiation technique

The novel nanosuperabsorbent copolymer (NSAP) was synthesized by grafting copolymerization of acrylamide (AM) and acrylic acid (AA) onto starch with montmorillonite (MMT) initiated using ⁶⁰Co γ‐ray irradiation. NSAP was characterized by IR spectroscopy and X‐ray diffraction (XRD). Different synthesis parameters were studied, such as AM‐to‐AA ratio, radiation total dose, radiation dose rate, crosslinker content, and clay content. NSAP can effectively improve the water retention capacity of soil. The effects of NSAP on crops were also studied, showing that NSAP has an encouraging potential for agricultural application. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1341–1346, 2005     

Dielectric properties of γ‐irradiated POE highly filled with aluminum hydroxide

The influence of γ irradiation on the dielectric and physicochemical properties of polyethylene‐octene elastomer (POE) containing 120 phr aluminum hydroxide (Al(OH)₃) as fillers has been investigated. The dielectric properties of the γ‐irradiated POE highly filled with Al(OH)₃ have been measured over a wide range of frequencies (70 kHz–3 MHz). It was found that γ irradiation strongly influences the dielectric properties of the POE composite in the dose range 0–250 kGy. POLYM. ENG. SCI. 46:1721–1727, 2006. © 2006 Society of Plastics Engineers     

γ‐Radiation‐treated starch/poly(vinyl alcohol) composites for cotton fabric sizing

Films of different composites based essentially on maize starch (MS)/poly(vinyl alcohol) (PVA) blends were prepared by the solution‐casting technique and subjected to various doses (20–100 kGy) of γ‐radiation. The MS/PVA blends were modified by the addition of glycerol (GY) and a graft copolymer (GP) of MS with acrylamide separately or together with the polymer blend solutions before casting. The γ‐treated composites were evaluated in terms of the apparent viscosity and their suitability as sizing materials for cotton fabrics. The sizeability of these composites for cotton fabrics was assessed in terms of the size removal percentage at different temperatures and the effect on the tensile properties and water absorption. The change in the apparent viscosity with the shear rate showed that γ‐irradiation improved the behavior of MS/PVA blends and their composites with GY or GP as a sizing material for cotton fabrics. Moreover, the improvement in the tensile mechanical properties of the sized cotton fabrics with these composites gave further support to this finding. The results for the size removal percentage and water adsorption indicated that these composites could be removed by washing at 70°C for 10 min. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3818–3826, 2004     

玉米羧甲基淀粉崩解剂的合成及性能改进

采用玉米淀粉为原料,以环氧氯丙烷为交联剂、氢氧化钠和氯化铵为复合催化剂、氯乙酸为醚化剂复合变性合成用作药片崩解剂的羧甲基淀粉,探讨了各种反应条件对淀粉的取代度、膨润性能及反应效率的影响,反应效率提高,反应时间大大缩短。原料最佳配比:n(脱水葡萄糖单元)∶n(环氧氯丙烷)∶n(氯乙酸)∶n(氢氧化钠)=1∶0.4∶0.6∶1.2,反应温度60°C左右,反应时间1～2h。     

Influence of γ‐irradiation on poly(methyl methacrylate)

Poly(methyl methacrylate) (PMMA) was γ‐irradiated (5–20 kGy) by a ¹³⁷Cs source at room temperature in air. The changes in the molecular structure attributed to γ‐irradiation were studied by mechanical testing (flexure and hardness), size‐exclusion chromatography, differential scanning calorimetry, thermal gravimetric analysis, and both Fourier transform infrared and solution ¹³C‐NMR spectroscopy. Scanning electron microscopy was used to investigate the influence of the dose of γ rays on the fracture behavior of PMMA. The experimental results confirm that the PMMA degradation process involves chain scission. It was also observed that PMMA presents a brittle fracture mechanism and modifications in the color, becoming yellowish. The mechanical property curves show a similar pattern when the γ‐radiation dose increases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 886–895, 2002     

Effect of γ‐irradiation on the physical properties and dyeability of poly(vinyl butyral) blends with polystyrene and poly(ethylene glycol)

Cast films of polymer blends essentially based on poly(vinyl butyral) (PVB) and equal ratios of polystyrene (PS) and poly(ethylene glycol) (PEG) were prepared from benzene and butyl alcohol solutions of the individual polymers. The effect of γ‐irradiation on the thermal decomposition and tensile mechanical properties was investigated. Moreover, the effect of γ‐irradiation on the dye affinity of PVB/PS and PVB/PEG for basic and acid dyestuffs was studied. The thermogravimetric analysis (TGA) study showed that the unirradiated PVB polymer films prepared in benzene displayed higher thermal stability than the same polymer films prepared in butanol. However, in all cases the thermal stability was found to increase with increasing γ‐irradiation dose. On the other hand, PVB/PS blend possesses higher thermal stability than PVB/PEG, as shown from the determination of the weight loss (%) at different heating temperatures, the temperatures of the maximum rate of reaction and the activation energy. While, pure PS films showed the stress‐strain behavior of brittle polymers, PVB/PS films showed the behavior of tough polymers with yielding properties. The results of dyeing clearly showed that the solvent type, blend composition, and irradiation dose are determining factors for the dye affinity for basic or acid dyes. For example, unirradiated PVB films prepared from butanol displayed a higher affinity for the basic and acid dyes than the same polymer prepared from the same benzene. However, PVB prepared from butanol showed higher affinity to the dyes than PS prepared from the same solvent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Infrared spectra of γ‐irradiated poly(acrylic acid)–polyacrylamide complex

Samples of polyacrylamide (PAAm), poly(acrylic acid) (PAA), and their complex were γ‐irradiated at different doses, namely 48, 96, and 144 KGy. The examination of the infrared spectra of these samples showed that there are no significant observable changes in their spectral features apart from slight changes in the intensities of the absorption bands. The analysis of the absorbances ratios (A 1700 cm^?1/A 1450 cm^?1) and (A 1650 cm^?1/A 1450 cm^?1), denoted as R₁ and R₂, respectively, showed that these ratios depend on γ‐doses. It was found that in the case of PAA, R₁ assumed linear increase with increasing the dose to 96 KGy and then showed marked decrease. For the complex, R₁ increased slightly by increasing the dose to 96 KGy and then decreased. For PAAm, although irradiation with 48 KGy increases the values of R₂, irradiation with 96 and 144 KGy decreases its value. On the other hand, for the complex, R₂ suggested slight decrease on irradiation with 48 KGy followed by continued increases with increasing the dose up to 144 KGy. The increase in R₁ and R₂ may be due to crosslinking as a result of the formation of free radicals. The decrease in these ratios after irradiation with 96 KGy may be due to degradation. It was concluded that γ‐irradiation has a lower effect on the complex (i.e., the complex has a structure which is different from those of PAA and PAAm). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1619–1623, 2002     

Effect of γ-irradiation on chlorendic acid based unsaturated polyesters

The effect of gamma ray irradiation on chlorendic acid based unsaturated polyesters was studied. Four different types of unsaturated polyesters, made by varying the molar ratios of chlorendic acid to isophthalie acid were irradiated with a Co⁶⁰ qource. After irradiation, the chlorine content decreases rapidly as the isophthalate content in the polyester chain increases. As the chlorendle acid content increases, the change in acid value after irradiation decreases. The increase in intrinsic viscosity is quite marked in high isophthalate containing polyesters after gamma ray irradiation and there is a noticeable decrease in intrinsic viscosity after gamma irradiation of high chlorendic acid containing polyesters. The effect of gamma irradiation on the percentage of cis and trans forms of these polyesters was studied with the help of infrared spectra. It appears that as the chlorendic acid content increases, on gamma irradiation conversion from trans unsaturation to cis unsaturation increases rapidly.     

Thermal decomposition behavior of γ‐irradiated poly(vinyl acetate)/poly(methyl methacrylate) miscible blends

Miscible polymer blends based on various ratios of poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) were prepared in film form by the solution casting technique using benzene as a common solvent. The thermal decomposition behavior of these blends and their individual homopolymers before and after γ‐irradiation at various doses (50–250 kGy) was investigated. The thermogravimetric analysis technique was utilized to determine the temperatures at which the maximum value of the rate of reaction (T_max) occurs and the kinetic parameters of the thermal decomposition. The rate of reaction curves of the individual homopolymers or their blends before or after γ‐ irradiation displayed similar trends in which the T_max corresponding to all polymers was found to exist in the same position but with different values. These findings and the visual observations of the blend solutions and the transparency of the films gave support to the complete miscibility of these blends. Three transitions were observed along the reaction rate versus temperature curves; the first was around 100–200°C with no defined T_max, which may arise from the evaporation of the solvent. The second T_max was in the 340–380°C range, which depended on the polymer blend and the γ‐irradiation condition. A third transition was seen in the rate of reaction curves only for pure PVAc and its blends with PMMA with ratios up to 50%, regardless of γ‐ irradiation. We concluded that γ‐irradiation improved the thermal stability of PVAc/PMMA blends, even though the PMMA polymer was degradable by γ irradiation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1773–1780, 2006     

The effect of γ‐Irradiation and reactive extrusion on the structure and properties of polycarbonate and starch blends: A work oriented to the recycling of thermoplastic wastes

Polymer materials with improved properties can be obtained through polymer blends. As a polymer mixture is generally immiscible and incompatible, it is necessary to develop new methods to improve the interfacial adhesion. In this study, polycarbonate‐based extruded thermoplastic were developed by blending polycarbonate with thermoplastic starch using extensive process engineering based on structure–property correlations. Starch was destructurized and plasticized followed by melt‐blending with polycarbonate. The optimal conditions for processing of the thermoplastics blends were found to be 230°C, 2 min of processing time, and 3–6 wt % of glycerol. The effect of γ‐irradiation on the fabrication of the blend was studied. Changes in structure, morphology, and properties resulting from γ‐exposure in the range 0–150 kGy were investigated. Electron spin resonance results revealed that numerous radicals remained trapped in the materials after irradiation even after a long time enabling reactions between starch and polycarbonate. Results obtained from tensile test, differential scanning calorimetry, and dynamic mechanical analysis revealed the relatively good affinity between the two components after blending in a micro‐extruder. Irradiated blends are thermally more stable than those non‐irradiated. Mechanical tests also showed that the efficiency of the irradiation depended greatly on the dose applied to the initial materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

酶促酯化制备松香酸淀粉酯的性质及结构表征

以松香和木薯淀粉为原料,二甲基亚砜（DMSO）为溶剂,采用酶催化酯化法在温和条件下制备了取代度0.031～0.092的松香酸淀粉酯,并对其部分理化性质进行了研究。结果表明：松香酸淀粉酯的性能与其取代度密切相关。随着取代度的增大,酯化淀粉产物的可溶指数和溶胀度降低,相对黏度和特性黏度增强,分子链也随取代度的增大而增加。通过对淀粉-碘络合物的紫外光谱分析,发现随着取代度的增大,酯化产物的最大紫外吸收波长向长波长方向移动,且蓝值减小。红外光谱（FT-IR）、核磁氢谱（¹H NMR）、差示热扫描（DSC）、热重差（TGA）和扫描电镜（SEM）对不同取代度的松香酸淀粉酯表征分析的结果表明：酯化产物在1727 cm^-1处产生C O的特性吸收峰,糊化温度及热稳定性相对预处理淀粉有所降低,淀粉颗粒的结晶度下降。     

Homogeneous graft copolymerization of chitosan with butyl acrylate by γ‐irradiation via a 6‐O‐maleoyl‐N‐phthaloyl‐chitosan intermediate

The graft copolymerization of butyl acrylate (BA) onto chitosan was tried via a new protection‐graft‐deprotection procedure. About 6‐O‐maleoyl‐N‐phthaloyl‐chitosan was synthesized and characterized by Fourier transform infrared spectra analysis (FT‐IR) and ¹H‐NMR. Because the intermediate 6‐O‐maleoyl‐N‐phthaloyl‐chitosan was soluble in organic solvents, the graft copolymerization was carried out in a homogeneous system. Grafting was initiated by γ‐irradiation. The graft extent was dependent on the irradiation dose and the concentration of BA monomer, and copolymers with grafting above 100% were readily prepared. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 489–493, 2006     

Deoxycholate‐chitosan nanospheres fabricated by γ‐irradiation and chemical modification: Nanoscale synthesis and controlled studies

A systematic protocol to fabricate self‐assembly deoxycholate‐chitosan nanospheres (DC‐CsNS) by γ‐ray pre‐irradiation and chemical modification was studied. Hydrophobic deoxycholic acid moieties were chemically conjugated to pre‐irradiated chitosan. The influences of chitosan physical forms (i.e., colloid and flake) during irradiation, radiation doses, and the reaction system (heterogeneous or homogeneous) on the chemical modification and the particle shape and size were investigated. Pre‐irradiation of chitosan in colloidal form produced smaller DC‐CsNS particle size than that of flake form. In the heterogeneous reaction, the pre‐irradiated dose influenced the DC‐CsNS particle size, whereas in the homogeneous reaction all pre‐irradiation doses gave an identical average size range of 30–50 nm. By pre‐irradiation (10 kGy) of chitosan in colloidal form before heterogeneous chemical conjugation, it is possible to obtain DC‐CsNS with an average size of 46 nm. DC‐CsNS of about 50 nm in size could also be synthesized using homogeneous chemical conjugation onto non‐irradiated chitosan with the addition of N‐hydroxysuccinimide (NHS). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

两步加碱法制备N,O-羧甲基壳聚糖—反应条件对取代度的影响

利用两步加碱法制备羧甲基壳聚糖,并采用等电点沉降法对其精制。结果表明,在m(壳聚糖)∶m(氯乙酸)∶m(氢氧化钠)=1∶4 8∶4 8,反应时间6h,温度60℃,异丙醇用量50mL,水用量22mL的较适宜反应条件下,制得的羧甲基壳聚糖取代度高达1 7,与传统方法制得的产物取代度最大1 1相比,有较大幅度的提高。同时,对影响产物取代度因素的研究表明:碱量、氯乙酸用量和反应温度是影响产物取代度的关键因素;产物取代度随碱量的增加而增加,随氯乙酸用量和反应温度的提高,呈现先增后减的规律。最后,对产物进行的红外光谱分析表明,产物为N,O 羧甲基壳聚糖,且主要是氧位取代。     

Carboxymethylation of cellulosic material (average degree of polymerization 2600) isolated from cotton (Gossypium) linters with respect to degree of substitution and rheological behavior

Carboxymethylation of cellulosic material (average degree of polymerization 2600) containing 76.5% cellulose and 23.6% xylose isolated from cotton (Gossypium) linters was studied under varying reaction conditions with respect to maximum degree of substitution (DS). The influence of reaction conditions on the apparent viscosity of the prepared derivatives was also studied. The conditions optimized were sodium hydroxide concentration 3.75M, monochloroacetic acid concentration 2.05 mol/AGU, carboxymethylation time 3.5 h, and temperature 55°C, to yield carboxymethyl cellulose of DS 0.77. Rheological studies of 1 and 2% solutions of the optimized product revealed their non‐Newtonian pseudoplastic behavior. Repeating units of the optimized product were also determined by HPLC after complete depolymerization of the polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1477–1482, 2005     

Preparation and properties of starch oxalate half-ester with different degrees of substitution

Oxalic acid, a strong dicarbonic acid mainly come from starch, was used to esterify gelatinized corn starch under nonaqueous conditions to give a material with degrees of substitution (DS) ranging from 0.08 to 0.87 depending on the oxalic acid/starch molar ratios used. The reaction product was washed by extraction with 95% ethanol solution and then characterized by using spectroscopic techniques (FT-IR, ¹H-NMR and ¹³C-NMR). The results from these analyses revealed the presence of carbonylic groups, indicating that the esterification reaction was successful. SEM showed that granules of corn starch swelled on gelatinization and the particles had a porous structure favorable to esterification. The effect of different degree of substitution on properties of oxalate starch half-ester was studied by intrinsic viscosity measurement, wide angle X-ray scattering (WAXS), thermogravimetry (TG) and humidity absorption. X-ray diffraction studies revealed the loss of the ordered A-type crystalline structure, characteristic of corn starch. With the increase in DS, Mw (estimated by intrinsic viscosity), the thermal stability of starch oxalate half-ester decreased markedly while its ability to take up water increased due to the introduction of the carboxylic group.