The Relationship between Bulk Property and Property Distribution in Thin-Wall Injection Molded PP at Different Molecular Weight and Molecular Weight Distribution

Thin-wall injection molded parts have been paid much attention to the lightweight saving from viewpoints of natural resources saving. In the injection molding, skin-core structure can be found in the parts. This skin-core structure affects the property of completed injection molding parts (bulk property) even if in thin-wall injection molding. However, there is a few research about the relationship between bulk property and internal property distribution in the injection molding specimen. In this study, thin-wall injection molded parts of polypropylene (PP) were prepared by 4 different molecular weight and molecular weight distribution to reveal the relationship between bulk property and property distribution. These characteristics were investigated by using tensile test, fracture toughness characterized by Essential Work of Fracture (EWF) method for bulk property and film tensile test by sliced sample for tensile property distribution. The property distribution test results revealed that the highly bulk property sample had thicker highly mechanical property layer on its surface.

THE RELATION OF SEQUENCE DISTRIBUTIONS OF S-SBR TO ITS MOLECULAR WEIGHT DISTRIBUTIONS

The relationship between sequence distributions and molecular weight distributions of S-SBR, obtained from styrene and butadiene anionic copolymerization at various conversions with THF/Li^+ as an initiator has been studied by ^(13)C-NMR,GPC. The results showed that the molecular weight distributions of the copolymer couldbe correlated sophisticatedly to the binary sequcne distributions or the monomer unit distributions of the copolymer in a corrected Poisson's distribution from.

Exploring the relationship of hyaluronic acid molecular weight and active targeting efficiency for designing hyaluronic acid-modified nanoparticles

Although it is reported that the targeting ability of hyaluronic acid(HA)-based nanoparticles(NPs) is molecular weight(MW) dependent,the influence of HA MW on targeting efficiency of HA-functionalized NPs and the underlying mechanism remain elusive. In this study,we constituted three HA-functionalized Dox-loaded NPs(Dox/HCVs) different HA MWs(7,63,and 102 k Da) and attempted to illustrate the effects of HA MW on the targeting efficiency.The three Dox/HCVs had similar physiochemical and pharmaceutical characteristics,but showed different affinity to CD44 receptor. Furthermore,Dox/HCV-63 exerted the best targeting effect and the highest cytotoxicity compared with Dox/HCV-7 and Dox/HCV-102. It was interesting to found that both the HA-CD44 binding affinity and induced CD44 clustering by HA-based NPs were HA MW-dependent,the two of which determine the apparent targeting efficacy of Dox/HCV NPs in the conflicting directions. Those results laid a good foundation for rationally designing HA-based NPs in cancer therapy.

Effect of Molecular Weight on Thermoelectric Performance of P3HT Analogues with 2-Propoxyethyl Side Chains

By replacing hexyl chains in poly(3-hexylthiophene)(P3HT)with 2-propoxyethyls,four poly(3-(2-propoxyethyl)thiophene)(P3POET)homopolymers with comparable polydispersity indexes(PDI)and regioregularities were prepared herein in addition with step increment of about 7 kDa on numberaverage molecular weight(M_(n))from around 11 to 32 kDa(accordingly denoted as P11k,P18k,P25k,and P32k).When doped in film by FeCl_(3)at the optimized conditions,the maximum power factor(PF_(max))increases greatly from 4.3μW·m^(-1)·K^(-2)for P11k to 8.8μW·m^(-1)·K^(-2)for P18k,and further to 9.7μW·m^(-1)·K^(-2)for P25k,followed by a slight decrease to 9.2μW·m^(-1)·K^(-2)for P32k.The close Seebeck coefficients(S)at PF_(max)are observed in these doped polymer films due to their consistent frontier orbital energy levels and Fermi levels.The main contribution to this PF_(max)evolution thus comes from the corresponding conductivities(σ).Theσvariation of the doped films can be rationally correlated with their microstructure evolution.

Effects of low molecular weight polysaccharide from Sargassum thunbergii against palmitic acid-induced intracellular lipid accumulation in 3T3-L1 adipocyte and HepG2 cells

Low molecular weight polysaccharides can be isolated from Sargassum thunbergii(LMPST)and in vitro experiments were conducted to evaluate the inhibitory effects on lipids.Two natures of LMPST were attained from S.thunbergii and appraised their LMPST on palmitic acid(PA)induced lipid accretion in Hep G2,and 3T3-L1 cells.LMPST treatment lessened lipid deposition and intracellular free fatty acid and triglyceride intensities in PA-treated above mentioned cells.The mechanistic study publicized that LMPST2 significantly suppressed adipogenesis and stimulated the PA-treated 3T3-L1 cells occupied in the lipolysis pathway.Furthermore,in PA-treated Hep G2 cells,the free fatty acid oxidation was significantly increased by LMPST2.Given these constructive properties of LMPST2 from S.thunbergii,is a potential candidate for diminishing the intracellular lipids,and for a therapeutic agent in those conditions.

Determination and Temperature Dependence of Plateau Modulus for Polymerization of Propylene to Isotactic Polypropylene with Ultra-high Molecular Weight under Catalysis of Ziegler-Natta Catalyst

The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.

Molecular Weight and Distribution of Cellulose and Cellulose Microspheres

[ Objective ] This study aimed to provide basic data for studying the relationship between structure and property of cellulose microspheres by measuring molecular weight of cellulose and cellulose microspheres with viscosity method and gel permeation chromatography （GPC） method. [ Method] In viscosity method, cadmium ethylenediamine was used as the solvent, intrinsic viscosity η of the solution was determined at 25 ℃ by using a Ubbelohde viscometer, to calculate the molecular weight of cellulose; in GPC method, 8% LiC1 / N, N-dimethylacetamide （LiC1/DMAc） was used as the solvent and 0.5% LiC1/DMAc was used as the mobile phase to determine the relative molecular weight and distribution of cellulose and cellulose microspheres. In addition, the determination results were analyzed to compare these two methods. [ Result ] Viscosity-average molecular weight Mr/ of cellulose and cellulose microspheres determined with viscosity method were 224,532 and 16,686, respectively; weight-average molecular weight Mw of cellulose and cellulose microspheres determined with GPC method were 284,196 and 22,345, respectively. [ Conclusion] The determination results of （;PC method are relatively close to the actual value and could truly reflect the characteristics of molecular weialat distribution of eellulose and cellulose mierosr, heres.

Analysis of Molecular Weight Distribution and Antioxidant Activities of Cirrhinus molitorella Skin Collagen Hydrolysates

[Objective] The aim of this work was to identify molecular weight （MW） distribution and antioxidant activity of fish skin col agen hydrolysates. [Method] The MW distribution of hydrolysates was determined using both size exclusion chromatography and matrix-assisted laser desorption ionization time-of-flight mass spec-trometry （MALDI-TOF-MS）. Fish skin were treated by the alkaline protease 2709. [Result] The optional conditions for hyerolysis were time 3 h, temperature 55 ℃, pH 10.0, substrate concentration 80 g/L and E/S 4%. The results of both methods indi-cated that the molecular weight of col agen hydrolysates was from 400 to 1 800 Da, and the peptides’ molecular weight was less than 1 400 Da mostly. The reducing power and antioxidant/radical scavenging activity [1, 1-diphenyl-2-picryl-hydrazyl （DPPH） free radical scavenging activity] were determined. [Conclusion] The results reveal that the fishskin hydrolysate is a potential source of antioxidants.

INFLUENCES OF MOLECULAR WEIGHT AND BRANCHING PARAMETER OF LACQUER POLYSACCHARIDE ON THE GROWTH OF LEUCOCYTES

A method of determining branching parameter of lacquer polysaccharide wasestablished by acid-base back-titration of terminal uronic acid of branches. The branchingfactors obtained are in agreement with the values determined by colorimetric method withcarbazole and the results estimated by using Zimm-Stockmayer equation from viscositydata. Influences of molecular weights and branching factors of five fractions of lacquerpolysaccharide on the bioactivities were studied. The results show that the polysaccharideshave bioactivities in motivating the growth of leucocytes, and the effect increases with thedecrease of molecular weight and branching factor in the range studied (17×10~4 >M_w>4×10~4).

Mechanism of size effects of a filler on the wear behavior of ultrahigh molecular weight polyethylene

Although the size effects of a filler are closely related to the complex multi-level structures of their polymer composites;unfortunately,such relationships remain poorly understood.In this study,we investigated the effects of various sizes(40-600 nm)of silicon carbide(SiC)fillers on the wear behavior of ultrahigh molecular weight polyethylene(UHMWPE)in the presence of the silane coupling agent KH-560.All of these SiC fillers improved the wear resistance of UHMWPE significantly,with a medium size(150 nm)being optimal.To examine the reasons for this behavior,we analyzed the multi-level structures of the samples in terms of their matrix structures(crystalline;amorphous;interphase),matrix-filler interactions(physical adsorption;chemical crosslinking;hybrid network)and the external effects of SiC fillers(bearing loads;transferring frictional heat).The high rigidity and thermal conductivity of SiC fillers and,more importantly,the intrinsic characteristics of the matrix structures(larger crystal grains;higher interphase;stronger amorphous entangled networks)were the key parameters affecting the enhancement in the wear-resistance of the UHMWPE.Herein,we also provide interpretations of the corresponding physical effects.Our results should improve our understanding of the structure-property relationships and,thus,should guide the formula design of UHMWPE composites.

Study on the influence of humic acid of different molecular weight on basic ion exchange resin's adsorption capacity

In this paper, humic acid （HA） was ultra-filtered into different molecular weight sections and was characterized by multielement analysis, UV254/TOC, FT-IR and three-dimensional fluorescence spectrometric. Since humic acids of different molecular weights have different hydrophilic and molecular size, the maximum adsorption capacity of basic ion exchange resins appears on the humic acid whose molecular weight ranges from 6000 to 10,000 Da.

Study on Enzymatic Hydrolysis of Gadus morrhua Skin Collagen and Molecular Weight Distribution of Hydrolysates

Process parameters on enzymatic hydrolysis and molecular weight （MW） distribution of collagen hydrolysates from Gadus morrhua skin were investigated. The optimal process parameters were obtained by the single-factor and orthogonal experiments. The molecular weight distribution of hydrolysates was determined using both Sephadex G25 partition and high speed liquid chromatography electricity spray mass spectrum （HPLC-ESI-MS）. Collagen hydrolysates were first gained by an alkaline protease ＂alcalase＂ for 3 h at temperature （50~C）, pH （10.0）, substrate concentration （75 g L-~）, and E/S （3%）. The molecular weight distribution of collagen hydrolysates ranged from 300 to 1 500 Da, and most of peptides were under 1 200 Da. Sephadex G25 partition and HPLC-ESI-MS should be successfully employed to determine the molecular weight distribution of collagen hydrolysates.

Biosynthesis of poly-3-hydroxybutyrate with a high molecular weight by methanotroph from methane and methanol

Poly-3-hydroxybutyrate （PHB） can be produced by various species of bacteria. Among the possible carbon sources, both methane and methanol could be a suitable substrate for the production of PHB. Methane is cheap and plentiful not only as natural gas, but also as biogas. Methanol can also maintain methanotrophic activity in some conditions. The methanotrophic strain Methylosinus trichosporium IMV3011 can accumulate PHB with methane and methanol in a brief nonsterile process. Liquid methanol （0.1%） was added to improve the oxidization of methane. The studies were carried out using shake flasks. Cultivation was performed in two stages： a continuous growth phase and a PHB accumulation phase under the conditions short of essential nutrients （ammonium, nitrate, phosphorus, copper, iron （Ⅲ）, magnesium or ethylenediamine tetraacetate （EDTA）） in batch culture. It was found that the most suitable growth time for the cell is 144 h. Then an optimized culture condition for second stage was determined, in which the PHB concentration could be much increased to 0.6 g/L. In order to increase PHB content, citric acid was added as an inhibitor of tricarboxylic acid cycle （TCA）. It was found that citric acid is favorable for the PHB accumulation, and the PHB yield was increased to 40% （w/w） from the initial yield of 12% （w/w） after nutrient deficiency cultivation. The PHB produced is of very high quality with molecular weight up to 1.5 × 10^6Da.

A HIGHLY ACTIVE NEODYMIUM CHLORIDE ISOPROPANOL COMPLEX/MODIFIED METHYLALUMINOXANE CATALYST FOR PREPARING POLYISOPRENE WITH HIGH CIS-1,4 STEREOSPECIFICITY AND NARROW MOLECULAR WEIGHT DISTRIBUTION

Neodymium chloride isopropanol complex （NdCl3.3＇prOH） activated by modified methylaluminoxane （MMAO） was examined in isoprene polymerization in hexane, with regards to Nd compounds, aluminum （Al） compounds, [Al]/[Nd] ratio, polymerization temperature and time. NdCl3＇3iprOH exhibited high activity producing polymers feasting high cis-l,4 stereospecificity （〉 96%）, very high molecular weight （Mn 〉 1.0 × 10^6） and fairly narrow molecular weight distribution （MWD, Mw/Mn 〈 2.0） simultaneously. In comparison, neodymium isopropoxide also showed high activity providing polymers with narrow MWD （Mw/Mn = 2.07）, but somewhat low cis-1,4 content （ca. 92%）, while neodymium chloride had no activity under present polymerization conditions. The Al compounds affected the polymer yield in the order of Al（i-Bu）3 〉 MMAO 〉 Al（i-Bu）2H. MMAO as cocatalyst afforded polyisoprene with high Mn over 1.0 × 10^6, whereas as stronger chain transfer agent than MMAO, AI（i-Bu）3 and AI（i-Bu）EH yielded polymers with low Mn （1.0 × 10^5-8.0 × 10^5）. NdCl3·3＇PrOH/MMAO catalyst showed a fairly good catalytic activity even at relatively low [Al]/[Nd] ratio of 30, and the produced polymer remained high cis-1,4 content of 95.8% along with high Mn over 1.0× 10^6 even at elevated temperatures up to 70℃. The polymerization rate is of the first order with respect to the concentration of isoprene. The mechanism of active species formation was discussed preliminarily.

WEIGHTED ALGORITHM FOR FINGERPRINTING RELATIONAL DATABASES

The necessity and the feasibility of introducing attribute weight into digital fingerprinting system are given. The weighted algorithm for fingerprinting relational databases of traitor tracing is proposed. Higher weights are assigned to more significant attributes, so important attributes are more frequently fingerprinted than other ones. Finally, the robustness of the proposed algorithm, such as performance against collusion attacks, is analyzed. Experimental results prove the superiority of the algorithm.

PREPARATION OF MICROPOROUS ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE) BY THERMALLY INDUCED PHASE SEPARATION OF A UHMWPE/LIQUID PARAFFIN MIXTURE

Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS).Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures,i.e.the cloud points and the dynamic crystallization temperatures,respectively.It was found that the cloudI points were coincident with the cryst...

STRUCTURE,MOLECULAR WEIGHT AND BIOACTIVITIES OF(1→3)-β-D-GLUCANS AND ITS SULFATED DERIVATIVES FROM FOUR KINDS OF LENTINUS EDODES

Lentinan samples,(1→3)-β-D-glucans containing 4.6-15.2 wt% proteins,coded as L-I_1 L-I_2 L-I_3 and L-I_4(L-I)were isolated from four kinds of Lentinus edodes.These glucans were treated with acetone to remove the protein in orderto obtain free protein glucans coded as LNP-I_1,LNP-I_2.LNP-I_3 and LNP-I_4(LNP-I).The free-protein polysaccharideswere sulfated to give derivatives(S-LNP-I)with degree of substitution(DS)from 0.4-0.8.The structural features andweight-average molecular weight(M_w)of the samples were investigated by using infrared spectroscopy,elemental analysis,^(13)C-NMR,size exclusion chromatography combined with laser light scattering(SEC-LLS)and viscometry.The effects ofstructure and conformation of the polysaccharides on antitumor activities were assayed in vivo(Sarcoma 180 solid tumors)and in vitro(Sarcoma 180,HL-60,MCF-7 and Vero tumors).The results indicated that the predominant species of thesamples L-I and LNP-I in 0.2 mol/L NaCl aqueous solution existed as triple-helical chains with high rigidity and in dimethylsulfoxide(DMSO)as single-flexible chains.Interestingly,the antitumor activities of LNP-I are lower than those of the nativeglucans(L-I),whereas their sulfated derivatives have higher inhibition ratio against Sarcoma 180 than LNP-I.The resultsreveal that the binding of protein,sulfated modification and the triple helix conformation are important factors in theenhancement of the antitumor activities of polysaccharides on the whole.

Studies on Human Immunoglobulin G from GBS Patient (Ⅲ)-The Determination of Molecular Weight of Human Immunoglobulin G by Capillary SDS Gel Electrophoresis

Guillain-Barre syndrome (GBS) is considered to be an autoimmune disorder of peripheralnervous system. In this paper. capillary SDS gel electrophoresis was performed on neutral coatedfused-silica capillary to determine the molecular weight of purified IgG samples from GBS patient.

Efficacy and Safety of Low Molecular Weight Heparin Prophylaxis for Venous Thromboembolism Following Lumbar Decompression Surgery

Objective To evaluate the efficacy and safety of low molecular weight heparin (LMWH) prophylaxis for venous thromboembolism (VTE) after lumbar decompression surgery. Methods Patients at high or the highest risk of VTE who underwent lumbar spine surgery in Peking Union Medical College Hospital from January 2004 to April 2011 were included in the present study. All the patients received a half dose of LMWH 6 hours after surgery followed by a full dose LMWH once per day until discharge. We recorded incidences of deep venous thrombosis (DVT), pulmonary embolism (PE), bleeding complications, and medication side effects. Results Seventy-eight consecutive patients were eligible and enrolled in this study. The mean hospital stat was 8.5±4.5 days. No symptomatic DVT, PE, or major bleeding events were observed. One patient developed wound ecchymosis, another developed wound bleeding, four had mild hepatic aminotransferase level elevation, and one developed a suspicious allergic reaction. Conclusion LMWH may be applied as an effective and safe prophylaxis for VTE in high-risk patients undergoing lumbar decompression surgery.

Structure and Properties of Self-reinforced Material Made from Ultra-high Molecular Weight Polyethylene-montmorillonite Nanocomposite

High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.