The difference of equilibrium melting point between poly(l-lactic acid) and poly(l-lactic acid)/poly(d-lactic acid) blends: cases with three molecular weights

2018 ◽  
Vol 68 (2) ◽  
pp. 271-276 ◽  
Author(s):  
Weijie Guo ◽  
Jun Shao ◽  
Xinxin Ye ◽  
Peng Sun ◽  
Chunfeng Meng ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Melting Point ◽  
Molecular Weights ◽  
Equilibrium Melting Point ◽  
The Difference

Molecular Dynamics Simulations on Melting of Aluminum

2013 ◽  
Vol 423-426 ◽  
pp. 935-938 ◽  
Author(s):  
Ji Feng Li ◽  
Xiao Ping Zhao ◽  
Jian Liu
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Molecular Dynamics Simulations ◽  
High Pressures ◽  
Ambient Pressure ◽  
Initial Porosity ◽  
Equilibrium Melting Point ◽  
Porosity Effect ◽  
Dynamics Simulations ◽  
Experimental Melting Point

Molecular dynamics simulations were performed to calculate the melting points of perfect crystalline aluminum to high pressures. Under ambientpressure, there exhibits about 20% superheating before melting compared to the experimental melting point. Under high pressures, thecalculated melting temperature increases with the pressure but at a decreasing rate, which agrees well with the Simon's melting equation. Porosity effect was also studied for aluminum crystals with various initial porosity at ambient pressure, which shows that the equilibrium melting point decreases with the initial porosity as experiments expect.

scholarly journals Investigation on compatibility of PLA/PBAT blends modified by epoxy-terminated branched polymers through chemical micro-crosslinking

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 39-54 ◽  
Author(s):  
Bo Wang ◽  
Yujuan Jin ◽  
Kai’er Kang ◽  
Nan Yang ◽  
Yunxuan Weng ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Glass Transition ◽  
Sem Analysis ◽  
Branched Polymers ◽  
Poly Lactic Acid ◽  
Elongation At Break ◽  
Butylene Terephthalate ◽  
The Difference ◽  
Physical And Chemical ◽  
The Impact

AbstractIn this study, a type of epoxy-terminated branched polymer (ETBP) was used as an interface compati- bilizer to modify the poly lactic acid (PLA)/poly(butylene adipate-co-butylene terephthalate) (PBAT) (70/30) blends. Upon addition of ETBP, the difference in glass transition temperature between PLA and PBAT became smaller. By adding 3.0 phr of ETBP, the elongation at break of the PLA/PBAT blends was found increased from 45.8% to 272.0%; the impact strength increased from 26.2 kJ·m−2 to 45.3 kJ·m−2. In SEM analysis, it was observed that the size of the dispersed PBAT particle decreased with the increasing of ETBP content. These results indicated that the compatibility between PLA and PBAT can be effectively enhanced by using ETBP as the modifier. The modification mechanism was discussed in detail. It proposes that both physical and chemical micro-crosslinking were formed, the latter of which was confirmed by gel content analysis.

scholarly journals Evaluation of the Efficiency of Ethanol Precipitation and Ultrafiltration on the Purification and Characteristics of Exopolysaccharides Produced by Three Lactic Acid Bacteria

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Manel Ziadi ◽  
Taroub Bouzaiene ◽  
Sana M’Hir ◽  
Kaouther Zaafouri ◽  
Ferid Mokhtar ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Lactobacillus Plantarum ◽  
Lactococcus Lactis ◽  
Leuconostoc Mesenteroides ◽  
Ftir Analysis ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Monomer Composition ◽  
Ethanol Precipitation

Exopolysaccharides (EPS) produced by three Lactic Acid Bacteria strains,Lactococcus lactisSLT10,Lactobacillus plantarumC7, andLeuconostoc mesenteroidesB3, were isolated using two methods: ethanol precipitation (EPS-ETOH) and ultrafiltration (EPS-UF) through a 10 KDa cut-off membrane. EPS recovery by ultrafiltration was higher than ethanol precipitation forLactococcus lactisSLT10 andLactobacillus plantarumC7. However, it was similar with both methods forLeuconostoc mesenteroidesB3. The monomer composition of the EPS fractions revealed differences in structures and molar ratios between the two studied methods. EPS isolated fromLactococcus lactisSLT10 are composed of glucose and mannose for EPS-ETOH against glucose, mannose, and rhamnose for EPS-UF. EPS extracted fromLactobacillus plantarumC7 andLeuconostoc mesenteroidesB3 showed similar composition (glucose and mannose) but different molar ratios. The molecular weights of the different EPS fractions ranged from 11.6±1.83 to 62.4±2.94 kDa. Molecular weights of EPS-ETOH fractions were higher than those of EPS-UF fractions. Fourier transform infrared (FTIR) analysis revealed a similarity in the distribution of the functional groups (O-H, C-H, C=O, -COO, and C-O-C) between the EPS isolated from the three strains.

Method of quantifying the loss of acidification activity of lactic acid starters during freezing and frozen storage

2000 ◽  
Vol 67 (1) ◽  
pp. 83-90 ◽  
Author(s):  
FERNANDA FONSECA ◽  
CATHERINE BÉAL ◽  
GEORGES CORRIEU
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Storage Time ◽  
Frozen Storage ◽  
Operating Conditions ◽  
Linear Relationships ◽  
Before And After ◽  
Acidification Activity ◽  
The Difference ◽  
And Storage

We have developed a method to quantify the resistance to freezing and frozen storage of lactic acid starters, based on measuring the time necessary to reach the maximum acidification rate in milk (tm) using the Cinac system. Depending on the operating conditions, tm increased during the freezing step and storage. The loss of acidification activity during freezing was quantified by the difference (Δtm) between the tm values of the concentrated cell suspension before and after freezing. During storage at −20 °C, linear relationships between tm and the storage time were established. Their slope, k, allowed the quantitation of the decrease in acidification activity during 9–14 weeks of frozen storage. The method was applied to determine the resistance to freezing and frozen storage of four strains of lactic acid bacteria and to quantify the cryoprotective effect of glycerol.

Effect of Size on Degradation of Porous Poly(Lactic Acid) Scaffold

2011 ◽  
Vol 311-313 ◽  
pp. 1741-1745
Author(s):  
Chao Guo ◽  
Xiao Bo Sheng ◽  
Cheng Lin Chu ◽  
Yin Sheng Dong
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Mass Loss ◽  
Porous Scaffold ◽  
Repeat Unit ◽  
Poly Lactic Acid ◽  
Porous Scaffolds ◽  
Degradation Behaviors ◽  
The Difference ◽  
Autocatalytic Effect

Poly (lactic acid) (PLA) scaffolds with different sizes are often fabricated for various requirements. A cellular automaton simulation was used to investigate the effect of the size on the degradation behaviors of porous PLA scaffolds. Four porous PLA scaffolds with 90% initial porosity and different sizes were established by a novel repeat unit method. Mass loss and the change in molecular weight during the degradation were simulated. The results indicate that mass loss is related to the size of the porous scaffold while molecular weight change is independent on the size. With the size of the porous scaffold increasing, the mass loss increases while the difference in mass loss between the scaffolds with different sizes decreases. All these changes can be attributed to the difference in the autocatalytic effect and corresponding oligomer diffusion ability of the porous scaffolds with different sizes.

scholarly journals Effects of oat bran, processed to different molecular weights of β-glucan, on plasma lipids and caecal formation of SCFA in mice

2010 ◽  
Vol 104 (3) ◽  
pp. 364-373 ◽  
Author(s):  
Tina Immerstrand ◽  
Kristina E. Andersson ◽  
Caroline Wange ◽  
Ana Rascon ◽  
Per Hellstrand ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Propionic Acid ◽  
Plasma Lipids ◽  
Plasma Cholesterol ◽  
Control Diet ◽  
Cholesterol Lowering ◽  
Molecular Weights ◽  
Oat Bran ◽  
Diet Pattern ◽  
The Difference

In the present study, we evaluated the cholesterol-lowering effects of different oat bran (OB) preparations, differing regarding their peak molecular weight (MWp) of β-glucans (2348, 1311, 241, 56, 21 or < 10 kDa), in C57BL/6NCrl mice. The diets were designed to be atherogenic (0·8 % cholesterol and 0·1 % cholic acid), and they reflected the Western diet pattern (41 % energy fat). All OB preparations that were investigated significantly reduced plasma cholesterol when compared with a cellulose-containing control diet, regardless of the molecular weight of β-glucan. Moreover, the difference in viscous properties between the processed OB (from 0·11 to 17·7 l/g) did not appear to play a major role in the cholesterol-lowering properties. In addition, there was no correlation between the molecular weight of β-glucan and the amount of propionic acid formed in caecum. Interestingly, however, there was a significant correlation between the ratio of (propionic acid+butyric acid)/acetic acid and the MWpof β-glucans: the ratio increased with increasing molecular weight. The results of the present study suggest that the molecular weights and viscous properties of β-glucan in oat products may not be crucial parameters for their cholesterol-lowering effects.

Isotopic Effect on the Melting Point of Lithium Nitrate

1970 ◽  
Vol 25 (5) ◽  
pp. 697-699 ◽  
Author(s):  
Bert Jansson ◽  
Arnold Lundén
Keyword(s):  
Melting Point ◽  
Isotope Effects ◽  
Zone Melting ◽  
Isotopic Effect ◽  
Lithium Nitrate ◽  
Lithium Metal ◽  
Self Diffusion ◽  
Fee Structure ◽  
The Difference ◽  
Self Diffusion Coefficient

The techniques of segregation during normal freezing and of zone melting have been used to establish that the melting point of 6LiNO3 is higher than that of 7LiNO3. The difference is of the order of 0.03 °C. The isotope shift of the melting point is in the opposite direction of the isotope effects found previously for phase transitions in solid lithium metal and lithium sulfate. For the latter salt a recalculation based on a more accurate value for the self-diffusion coefficient shows that the temperature of transition at about 575 °C to a fee structure is about 0.08 degr. lower for 6Li2SO4 than for 7Li2SO4.

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