scholarly journals Composting of Polylactide Containing Natural Anti-Aging Compounds of Plant Origin

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1582 ◽  
Author(s):  
Moraczewski ◽  
Malinowski ◽  
Sikorska ◽  
Karasiewicz ◽  
Stepczyńska ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Visual Assessment ◽  
Thermal Strength ◽  
Scanning Calorimetry ◽  
Microscopic Appearance ◽  
Composting Process ◽  
Phase Transition Temperatures ◽  
The Impact ◽  
Industrial Composting

The paper presents the effects of biodegradation of polylactide containing natural anti-aging compounds. Polymer containing 0.5; 5 and 10 wt % of coffee, cocoa or cinnamon extracts were subjected to industrial composting for 7, 14, 21 or 28 days. The effect of the composting process on polylactide properties was examined based on visual assessment, scanning electron microscopy, average molecular weight, differential scanning calorimetry, thermogravimetry, and tensile strength. The impact of the tested extracts on the effects of the composting process was compared with the impact of a commercially available anti-aging compound. It was found that the tested extracts in most cases did not adversely affect the effects of the composting process compared to pure polylactide, often resulting in intensification of biodegradation processes. As a result of the composting process, changes in the macro- and microscopic appearance of the samples and a decrease in molecular weight, phase transition temperatures, thermal resistance, and thermal strength were observed on a scale close to or greater than the reference anti-aging compound.

scholarly journals Physicochemical and Antifungal Properties of Clotrimazole in Combination with High-Molecular Weight Chitosan as a Multifunctional Excipient

Marine Drugs ◽  
2020 ◽  
Vol 18 (12) ◽  
pp. 591
Author(s):  
Bożena Grimling ◽  
Bożena Karolewicz ◽  
Urszula Nawrot ◽  
Katarzyna Włodarczyk ◽  
Agata Górniak
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Weight Ratio ◽  
Scanning Calorimetry ◽  
Minimal Inhibitory Concentrations ◽  
Dissolution Tests ◽  
Effective Combination ◽  
The Impact ◽  
High Molecular Weight Chitosan

Chitosans represent a group of multifunctional drug excipients. Here, we aimed to estimate the impact of high-molecular weight chitosan on the physicochemical properties of clotrimazole–chitosan solid mixtures (CL–CH), prepared by grinding and kneading methods. We characterised these formulas by infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffractometry, and performed in vitro clotrimazole dissolution tests. Additionally, we examined the antifungal activity of clotrimazole–chitosan mixtures against clinical Candida isolates under neutral and acid conditions. The synergistic effect of clotrimazole and chitosan S combinations was observed in tests carried out at pH 4 on Candida glabrata strains. The inhibition of C. glabrata growth reached at least 90%, regardless of the drug/excipient weight ratio, and even at half of the minimal inhibitory concentrations of clotrimazole. Our results demonstrate that clotrimazole and high-molecular weight chitosan could be an effective combination in a topical antifungal formulation, as chitosan acts synergistically with clotrimazole against non-albicans candida strains.

Synthesis of Segmented Anisotropic-Isotropic Poly(Aryl Ester)Poly(Arylene Ether) Copolymers

1989 ◽  
Vol 175 ◽  
Author(s):  
J. E. McGratn ◽  
K. L. Cooper ◽  
W. Waehamad ◽  
H. Huang ◽  
G. L. Wilkes
Keyword(s):  
Molecular Weight ◽  
Liquid Crystal ◽  
Benzoic Acid ◽  
Liquid Crystalline ◽  
Average Molecular Weight ◽  
Nucleophilic Aromatic Substitution ◽  
Copolymer Composition ◽  
Aromatic Substitution ◽  
Scanning Calorimetry ◽  
Arylene Ether

AbstractCarboxyl functional poly(arylene ether) oligomers of controlled number average molecular weight were synthesized via nucleophilic aromatic substitution step polymerization using p-hydroxy benzoic acid as the molecular weight and end group controlling reagents. The subsequent functionalized polyarylene ethers were copolymerized with acetoxy benzoic acid or acetoxyphenoxy benzoic acid via melt acidolysis procedures. Successful copolymers were generated using chlorobenzene as a solvent for the first s age of the reaction followed by melt reaction at temperatures as high as 325°C. Resulting copolymer composition and segment size were investigated. It was possible to prepare improved solvent resistant copolymers through incorporation of the liquid crystal polyester (LCP) segment. Extraction tests using boiling chloroform showed that a high percentage of segmented copolymer were generated. Swelling characteristics were also noted and were observed to decrease as a function of the LCP concentration utilized. Multiple transitions were observed in differential scanning calorimetry consistent with Tg's, Tm's and possibly with liquid crystal transitions. Optical microscopy showed an ordered microstructure developed which is consistent with the presence of liquid crystalline phases. The materials were successfully compression molded to afford tough coherent films at all compositions, implying the likelihood of improved compressive strength relative to the LCP homo- or copolyesters.

The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor

Holzforschung ◽  
2016 ◽  
Vol 70 (6) ◽  
pp. 495-501 ◽  
Author(s):  
Binh T.T. Dang ◽  
Harald Brelid ◽  
Hans Theliander
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Ion Concentration ◽  
Small Scale ◽  
Kraft Cooking ◽  
Flow Through ◽  
Cooking Times ◽  
The Impact

Abstract The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (Mw) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to Mw decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].

scholarly journals Synthesis, Characterization and Glass - Reinforced Composites of Thiourea - Formaldehyde - Phenol Resin

2004 ◽  
Vol 1 (5) ◽  
pp. 256-262 ◽  
Author(s):  
Kanuprasad Dahyalal Patel ◽  
Dhirubhai J. Desai ◽  
Manish M. Morekar ◽  
Yogesh Shrikant Tilak
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Average Molecular Weight ◽  
Conductometric Titration ◽  
Spectral Studies ◽  
Reinforced Composites ◽  
Number Average Molecular Weight ◽  
Scanning Calorimetry ◽  
Alcoholic Alkali ◽  
Glass Reinforced Composites

N,N'-Dimethylol thiourea-formaldehyde (DMTUF) resin having the methylol group (CH2OH) has been prepared and characterized. The condensation of DMTUF resin with Phenol (P) was carried out in the presence of alcoholic alkali catalyst at varying ratios of DMTUF: P, namely 1:1, 1:1.5 and 1:2. The resultant DMTUFP resin was characterized by elemental analysis, IR spectral studies, number average molecular weight (M¯n) estimated by non-aqueous conductometric titration, and thermo gravimetry. The curing study of DMTUFP resin with hexamethylene tetramine (HMTA) was monitored by differential scanning calorimetry (DSC) and kinetic parameters were evaluated. Glass-reinforced composites based on the DMTUFP-HMTA system have also been prepared and characterized.

scholarly journals Initiator Feeding Policies in Semi-Batch Free Radical Polymerization: A Monte Carlo Study

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1291 ◽  
Author(s):  
Ali Seyedi ◽  
Mohammad Najafi ◽  
Gregory T. Russell ◽  
Yousef Mohammadi ◽  
Eduardo Vivaldo-Lima ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Monte Carlo ◽  
Free Radical ◽  
Methyl Methacrylate ◽  
Radical Polymerization ◽  
Average Molecular Weight ◽  
Free Radical Polymerization ◽  
Monte Carlo Algorithm ◽  
Single Shot ◽  
The Impact

A Monte Carlo simulation algorithm is developed to visualize the impact of various initiator feeding policies on the kinetics of free radical polymerization. Three cases are studied: (1) general free radical polymerization using typical rate constants; (2) diffusion-controlled styrene free radical polymerization in a relatively small amount of solvent; and (3) methyl methacrylate free radical polymerization in solution. The number- and weight-average chain lengths, molecular weight distribution (MWD), and polymerization time were computed for each initiator feeding policy. The results show that a higher number of initiator shots throughout polymerization at a fixed amount of initiator significantly increases average molecular weight and broadens MWD. Similar results are also observed when most of the initiator is added at higher conversions. It is demonstrated that one can double the molecular weight of polystyrene and increase its dispersity by 50% through a four-shot instead of a single shot feeding policy. Similar behavior occurs in the case of methyl methacrylate, while the total time drops by about 5%. In addition, policies injecting initiator at high monomer conversions result in a higher unreacted initiator content in the final product. Lastly, simulation conversion-time profiles are in agreement with benchmark literature information for methyl methacrylate, which essentially validates the highly effective and flexible Monte Carlo algorithm developed in this work.

Binary molybdenum-based catalyst for coordination polymerization of styrene

2016 ◽  
Vol 49 (5) ◽  
pp. 408-421 ◽  
Author(s):  
Jieting Geng ◽  
Youguo Shao ◽  
Feng Song ◽  
Feng Li ◽  
Jing Hua
Keyword(s):  
Molecular Weight ◽  
Catalyst Activity ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Catalyst System ◽  
Bulk Polymerization ◽  
Molar Ratio ◽  
Scanning Calorimetry ◽  
Coordination Polymerization ◽  
Co Catalyst

Coordination polymerization of styrene (St) using molybdenum pentachloride supported by phosphite ligand in the presence of metal organic compound was studied for the first time. The types of phosphite and co-catalysts significantly affected the catalytic activity of the molybdenum (V) (Mo(V)) active center and the number-average molecular weight ( Mn) of the resultant polymer. Among the examined catalysts, tri(nonylphenyl)phosphite (TNPP) ligand and AlOPhCH3( i-Bu)2 as co-catalyst provided the polymer with highest yield (up to 87.1%), metallocene as co-catalyst provided the polymer with highest Mn (up to 5.32 × 105). The effect of [P]/[Mo] molar ratio on catalyst activity of the polymerization was discussed and the structures of Mo·TNPP complexes were preliminarily studied by infrared (IR) and ultraviolet spectroscopies. Besides, the polystyrene (PS) samples synthesized through bulk polymerization and solution polymerization were characterized by gel permeation chromatography, IR, carbon 13 nuclear magnetic resonance, and differential scanning calorimetry, respectively, and the results indicated both of the PS had high molecular weight (approximately 105) and atactic structure. All these results demonstrated that Mo(V) catalyst system was very effective for St polymerization.

On the structure alteration of crosslinkable gelatin coupled with methacrylic acid and its hydrogel

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Xiaohong Hu ◽  
Dan Li ◽  
Feng Zhou ◽  
Changyou Gao
Keyword(s):  
Molecular Weight ◽  
Triple Helix ◽  
Sol Gel ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Apparent Molecular Weight ◽  
Small Range ◽  
Scanning Calorimetry ◽  
Physical Chemical ◽  
Substitution Degree

AbstractPhysical structures of a crosslinkable gelatin derivative (GM) were studied in terms of alteration of apparent molecular weight, triple helix content and mechanical strength. The GM with a substitution degree (DS) of 49% and 79% was prepared by grafting mechacrylic acid (MA), which was able to form injectable hydrogel by photoinitiating polymerization. The zeta potential was increased along the increase of DS. After modification, the apparent number-average molecular weight (Mn) detected by gel permeation chromatography was decreased to about 2/3 of gelatin, while the apparent weight-average molecular weight (Mw) was changed within a small range. Differential scanning calorimetry and circular dichroism (CD) revealed that ability of triple-helix formation of GM was decreased along with the increase of DS and decrease of GM concentration. After photocrosslinking, the sol-gel transition of GM49 physical-chemical hydrogel still existed, but completely disappeared for its chemical hydrogel. The physical-chemical hydrogel showed a larger storage modulus at 20°C than at 37°C as a result of additional physical crosslinking.

scholarly journals Synthesis of High Molecular Weight Stereo-Di-Block Copolymers Driven by a Co-Initiator Free Catalyst

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 232
Author(s):  
Carmen Moya-Lopez ◽  
Ivan Bravo ◽  
José A. Castro-Osma ◽  
David Chapron ◽  
Patrice Bourson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Diblock Copolymers ◽  
Average Molecular Weight ◽  
Kinetic Studies ◽  
Scanning Calorimetry ◽  
One Pot ◽  
Mechanism Of Reaction ◽  
Sequential Addition ◽  
The One

Stereo-diblock copolymers of high molecular weight polylactide (PLA) were synthetized by the one pot-sequential addition method assisted by a heteroscorpionate catalyst without the need of a co-initiator. The alkyl zinc organometallic heteroscorpionate derivative (Zn(Et)(κ3-bpzteH)] (bpzteH = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-para-tolylethoxide) proved to assist in the mechanism of reaction following a coordination-insertion process. Kinetic studies along with the linear correlation between monomer and number average molecular weight (Mn) conversion, and the narrow polydispersities supported the truly living polymerization character of the initiator, whereas matrix-assisted laser desorption/Ionization-time of flight (MALDI-TOF) studies showed a very low order of transesterification. The high stereo-control attained for the afforded high molecular weight derivatives was revealed by homonuclear decoupled 1H NMR spectra and polarimetry measurements. The nanostructure of the PLA derivatives was studied by both wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) and the stereocomplex phase of the PLA stereo-diblock copolymers was successfully identified.

The Research of Second Acid Fracturing Temporary Plugging Agent in Long Interval Gas Well of Puguang

2012 ◽  
Vol 629 ◽  
pp. 370-375
Author(s):  
Cheng Yu Zhou ◽  
Dong Wang ◽  
Hong Liu ◽  
Wei Xiong
Keyword(s):  
Molecular Weight ◽  
Spectroscopic Analysis ◽  
Polyester Fibre ◽  
Average Molecular Weight ◽  
Scanning Calorimetry ◽  
Gas Well ◽  
Acid Fracturing ◽  
Infrared Spectroscopic Analysis ◽  
Series Of Experiments ◽  
Temporary Plugging Agent

On the basis of physical truth of long Interval gas well in Puguang, it proposes a technology for adding temporary plugging agent in the second acid fracturing fluid. The CKHG-1 system and polyester fibre solid intensifier have been synthetized and taken infrared spectroscopic analysis. A series of experiments have been done such as density, molecular weight, differential scanning calorimetry, scanning electron microscopy, acid soluble rate and core flowing experiment. The results were obtained through tests, including temporary plugging agent density of 1.2297 g/ml, average molecular weight of 1.27×105, glass-transition temperature of 61°C, temporary plugging particles covering fixed effect was ideal, acid soluble rate after four hours of 95%, temporary plugging rate >99%. They can meet actual conditions in worksite.

Synthesis, Characterization and Glass-Reinforced Composites of Acetone–Formaldehyde–Phenol Resins

1997 ◽  
Vol 9 (2) ◽  
pp. 153-160 ◽  
Author(s):  
Hasmukh S Patel ◽  
Bharat C Dixit
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Average Molecular Weight ◽  
Conductometric Titration ◽  
Spectral Studies ◽  
Reinforced Composites ◽  
Number Average Molecular Weight ◽  
Scanning Calorimetry ◽  
Alcoholic Alkali ◽  
Glass Reinforced Composites

Acetone–formaldehyde (AF) resin having the methylol group (–CH2OH) has been prepared and characterized. The condensation of AF resin with phenol (P) was carried out in the presence of alcoholic alkali catalyst at varying ratios of AF:P, namely 1:1, 1:1.5 and 1:2. The resultant AFP resins were characterized by elemental analysis, IR spectral studies, number average molecular weight ( Mn) estimated by non-aqueous conductometric titration, and thermogravimetry. The curing study of AFP resins with hexamethylene tetramine (HMTA) was monitored by differential scanning calorimetry (DSC) and kinetic parameters were evaluated. Glass-reinforced composites based on the AFP–HMTA system have also been prepared and characterized.

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