Papers by Keyword: Molecular Weight (MW)

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Authors: Qiao Wang, Jian Wang, Geng Zhong
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 Mw 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.
Authors: Tian Ming Gao, Rui Hong Xie, Pu Wang Li, Mao Fang Huang
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.
Authors: Jing He, Xue Gang Luo, Tao Ying, Ji Liang Wu
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.
Authors: Yan Jie Li, Yi Ming Ha, Feng Wang, Yong Fu Li
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.
Authors: Masahiro Momota, Satoshi Tanaka, Nozomu Uchida, Keizo Uematsu
Authors: Yao Yang Tsai, Chih Kang Chang
Abstract: Suspending powder in dielectric fluid of EDM (electrical discharge machining) has been developed to improve the quality of machined surface recently. The used powders are usually Al, Cu, Cr and so on metal powder because conductive particle can increase the spark gap and improve surface roughness of machined surface. Semi-conductive powder, Si is also utilized for the sake of increasing machining speed. This paper presents a new tryout to suspend polymer particles in the dielectric fluid of EDM. Experimental results show that the EDM process with suspending polymer particles still can be carried out but its surface roughness is not so good in conventional EDM oil. However the conventional EDM oil was taken the replace of silicone oil, suspending polyaniline (PANI-emer) of high molecular weight (Mw~65000) has finer improvement even better than using Si powder. Its surface roughness achieves less than Ra 0.2μm at low concentration and will be decreased gradually with increasing the concentration of PANI-emer (Mw~65000). The surface roughness is Ra 0.14μm when the powders concentration is 10g/l. Even for different type of polyaniline shows different machining characteristics. The surfaces roughness becomes worse when the concentration of low molecular weight PANI-emer (Mw~20000) is higher. An electric-conductive PANI-salt powder has a rapid decrease of surface roughness with increasing its concentration than other materials.
Authors: Wen Jing Guo, Fu Cheng Bao, Zheng Wang, Liang Chang, Li Gao
Abstract: This study is devoted to investigate the effects of wood fiber content on structure and properties of wood fiber /poly(lactic acid) bio-composites (WF/PLA bio-composites). The WF/PLA bio-composites with WF from 30% to 60% and from 70% to 90% were prepared using melt extrusion and high-speed mixing methods respectively. The physical, mechanical, thermal, and macromolecular properties of WF/PLA bio-composites were evaluated. The results are as follows: Density of WF/PLA bio-composites increased when WF increased from 30% to 60%, and decreased when WF increased from 70% to 90%. Water resistance of bio-composite decreased with increasing WF content. The flexural strength of WF/PLA bio-composites were lowered when adding WF into PLA. The flexural strength decreased when WF increased from 30% to 50%, and then increased when WF increased from 60% to 80%. The flexural modulus of the bio-composite was higher than that of PLA without WF. Both n and w of PLA in WF/PLA bio-composite were decreased more than 70% with WF increased. The Tg, Tm values of PLA in the bio-composites were decreased with the WF increased. The cold crystal temperature (Tcc) was decreased with WF increased at low WF content. All the property changes were related to the decreasing of molecular weight of PLA in WF/PLA bio-composites.
Authors: Jun Ying Zhang, Peng Dou
Abstract: Environmentally benign adhesive was synthesized by dispersion copolymerization of styrene(St) and butyl acrylate (BA) in an ethanol medium with benzoyl peroxide (BPO) as the initiator and poly(vinylpyrrolidone) as the stabilizer in the presence of acrylic acid(AA) as the functional monomer. The effect of the concentration of stabilizer, initiator and functional monomer on the conversions, molecular weights and molecular weight distributions was investigated. The results show that the conversions almost keep invariable with the increasing of stabilizer concentration, but the molecular weights increase and molecular weight distributions decrease. Conversions increase with the increasing of initiator concentration, but the molecular weights and molecular weight distributions decrease. However with the increasing of functional monomer concentration, conversions and molecular weight distributions increase but the molecular weights decrease.
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