Papers by Keyword: Molecular Weight (MW)

Abstract: Konjac glucomannan with different molecular weights/poly(acrylic acid) hydrogels were prepared in this paper. The structure of the IPN hydrogels was characterized by FT-IR and SEM. The swelling ratio of these hydrogels showed they had pH-sensitive properties and the enzymatic degradation tests showed the hydrogels retain the enzymatic degradation character of KGM. Furthermore, hydrogel composed of native KGM degraded sharply in enzymatic degradation test and it had bigger swelling ratio and weight loss ratio than those hydrogels which composed of lower molecular weights KGM. Therefore, hydrogels composed of lower molecular weight might release drug more stable when they were used as drug carrier.

Abstract: Arabinoxylans were prepared from bran, shorts and flour, three wheat milling fractions. The yields of bran arabinoxylan (WBAX), shorts arabinoxylan ( WSAX) and flour arabinoxylan ( WFAX) were 8.99%, 7.28% and 1.12% respectively. Sugar composition analysis showed that WFAX contained less non-cellulosic sugars ( 75.56%) compared with WFAX and WSAX. WBAX had the lowest Ara/Xyl ratio compared with WSAX and WFAX. HPSEC analysis showed that WFAX had higher molecular weight compared with WBAX and WSAX, and WBAX had the lowest molecular weight. WBAX, WSAX and WFAX in water solution had higher molecular weight than in 0.5mol/L NaOH and 1.0mol/L NaOH. In 1.0 mol/L NaOH solution, arabinoxylans had the lowest molecular weight compared that in 0.5 mol/L NaOH and distilled water. From the recovery of WBAX, WSAX and WFAX in different solvents, it showed that 1.0N NaOH had good dissolved effect for arabinoxylans, and water heating treatment ( 80°C 2hr, then stirring overnight at room temperature) had poor dissolved properties compared with 0.5 mol/L NaOH and 1.0 mol/L NaOH ( 25°C,2hr)

Abstract: Test of the rheology behavior for low protein natural rubber(LPNR) were carried out with rubber processing analyzer(RPA), and molecular weight were carried out with gel permeation chromatography(GPC). The results showed that molecular of LPNR is lower than natural rubber(NR), The complex viscosity(n*) of NR is higher than LPNR. The stress relaxation indicate that time of LPNR is faster than NR, it illuminate that LPNR has lower molecular weight than NR, and processing performance have distinct discrepancy between NR and LPNR. The torque(S’) with strain rising indicated that one linear viscoelastic region and one nonlinear viscoelastic region in whole range, and LPNR has lower S’ than NR.

Abstract: In order to resolve the soil polluted problem which were brought by polyethylene, the study focus on the effects of different molecular weight polyethylene powders to soil, and discuss the molecular weight change of polyethylene. This study made use of four kinds of molecular weight polyethylene powders as materials, added them into the soil of potted soybean to test efficient N content, efficient P content, efficient K content in every development period of soybean, and test the molecular weight of four kinds of polyethylene after the whole development periods of soybean. The Important findings in this study were that there are no significant differences among the efficient N content, efficient P content, efficient K of control group and every experimental group, the molecular weight of polyethylene are nearly no change. it means that the different molecular weight polyethylene powders have no effect to soil.

Abstract: Poly (γ-glutamic acid) (γ-PGA) is a special anionic, water-soluble and high viscous polymer ^[1] which is condensed by glutamate via amide linkages between their a-amino and γ-carboxylic acid groups ^[2]. For its excellent characters, potential applications of γ-PGA have been of interest in the past few years in a broad range of industrial fields ^[3]. And the decision to application of γ-PGA will be done, depending on its’ molecular weight. So this article main expresses the influence of different carbon sources to γ-PGA’s molecular weight distribution. By SDS-PAGE, we found that the molecular weight distributions of biosynthetic γ-PGA were different in the different carbon sources. All the results showed that changing the carbon source of mediums did make the biosynthetic γ-PGA’s yield and molecular weight distribution been changed.

Abstract: In this paper, recycled PE was added directly to the asphalt mixture to prepare high modulus asphalt mixture. To study the influence of the dosage and molecular weight of recycled PE on the performance of asphalt mixture, three kinds of recycled PE with different molecular weight and three asphalt binders (Conventional, SBS Modified and PE Modified) were used to prepare eight kinds of asphalt mixture. Various tests, including dynamic modulus, wheel tracking and Lottman test, were conducted to evaluate the performance of them. The results showed that 1) the dynamic modulus of asphalt mixture modified by recycled PE is higher than the normal mixture and mixture prepared with SBS modified asphalt binder; 2) adding recycled PE directly into the asphalt mixture during mixing is more effective than preparing asphalt mixture with PE modified asphalt binder in making high modulus asphalt mixture; 3) the recycled PE used to produce high modulus asphalt mixture should have certain big molecular weight, more than 27,000, and the dosage of recycled PE should be no less than 0.4% of the total weight of asphalt mixture. The performance tests indicted the good high temperature deformation resistance property of asphalt mixture modified by recycled PE.

Abstract: Due to the lack of trifunctional polypropylene oxide (TPPO) certified reference material (CRM) with precise molecular weight on the market, it is therefore very important to prepare such CRM to calibrate the molecular weight testing equipments, and assure the quality in polyurethanes manufacture. In this paper, the certification of TPPO CRM was introduced based on the size-exclusion chromatography with a multi-angle laser light scattering (SEC-MALLS) method and end-group analysis method. First, TPPO was synthesized via controlled ring-opening polymerization of propylene oxide in the condition of both high temperature and pressure using double metal cyanide (DMC) complexes as catalyst, and TPPO oligomer as coinitiator. Then, the molecular weight homogeneity of TPPO CRM was evaluated by using the F-distribution model, and the storage stability of the molecular weight of TPPO CRM was assessed. All potential uncertainty factors for the certification of TPPO CRM were evaluated using cause-effect diagram. The results showed that the chemical structure of TPPO CRM was an anticipatory structure, which was confirmed by IR. The molecular weight homogeneity of TPPO CRM was qualified. The storage stability period of the final product was one year with respect to its molecular weight, and the certification results of TPPO CRM obtained by SEC-MALLS and end-group analysis were 4996±162 and 5025±146, respectively.

Abstract: Xanthan gum samples were irradiated in aqueous solution at different doses (0-120 kGy) of 60Co γ-rays. The changes of molecular weight and structures of irradiated xanthan gum samples were investigated and characterized by using gel permeation chromatography(GPC), X-ray diffraction (XRD), fourier-transform infrared spectra (FTIR), ultraviolet–visible spectral (UV–vis) analysis and rheometer. Results showed the molecular weight decreased gradually with increasing irradiation dose. The radiation chemical yields G(d) of xanthan gum was 26.55. FTIR spectra and XRD indicated that γ-irradiation introduced no significant changes into the structure and crystal texture, but UV spectra showed a distinct absorption peak at about 265 nm, increasing with irradiation dose, which was attributed to the formation of carbonyl groups or double bond. Apparent viscosity of xanthan gum solution decreased with increasing irradiation dose and remain basically constant with the prolonging of shear time after irradiation.

Abstract: Polysiloxanes containing cyanoethyl groups (PDMS-CN) is a useful functional polysiloxanes. In this paper a new method was employed to prepare the polysiloxane with various number average molecular weight (Mn) and cyanoethyl groups. Mns of PDMS-CN were determined by GPC and the relationships between the instrinsic viscosity ([η]) and Mn of PDMS-CN were given. The contents of cyanoethyl groups were determined by FT-IR and ¹H NMR.

Abstract: Amorphophallus bulbifer (A. bulbifer) is a promising species in Amorphophallus sp., with great potentiality of developing, low risk for cultivation and considerable commercial benefits, mainly locates in tropical and subtropical regions or near the equator. Konjac glucomannan (KGM) is the main component of Amorphophallus tuber which is a water-soluble dietary fiber. In this work, some physiochemical properties of KGM in three Amorphophallus species flour [one was A.bulbifer, the other two were current main species namely Amorphophallus rivieri (A. rivieri) and Amorphophallus albus (A. albus)] were studied and compared with each other. The KGM content in A. rivieri, A. albus and A. bulbifer flour were 85.03%, 76.28% and 88.07% (w/w), respectively. The apparent viscosity, viscosity average molecular weight, whiteness, gel-forming properties and chemical structure of KGM in the three flours were investigated by using viscometer, colorimeter, texture analyzer and Fourier transform infrared (FT-IR) spectroscopy. The results indicated that the viscosity and M_w of A. bulbifer was the largest, gel strength was almost same (p>0.05) and the molecular structure were of no differences of three KGM. It may be proposed that transplanting A. bulbifer from its native land in the tropical and subtropical regions to temperate zone in the southwest part of China would be feasible, and it would cause the revolution of Amorphophallus sp. and more considerable benefits.