scholarly journals Preparation of high molecular weight polyvinyl alcohol by emulsifier-free emulsion polymerization

2020 ◽  
Vol 206 ◽  
pp. 02023
Author(s):  
Xinqiu Hong ◽  
Liming Zou ◽  
Jingyang Zhang ◽  
Liujian Wang
Keyword(s):  
Molecular Weight ◽  
Polyvinyl Alcohol ◽  
Emulsion Polymerization ◽  
High Molecular Weight ◽  
Thermo Gravimetric Analysis ◽  
Degree Of Polymerization ◽  
Gravimetric Analysis ◽  
Structure And Property ◽  
H Nmr ◽  
Redox Initiator

In this report, high molecular weight polyvinyl alcohol (PVA) was prepared by emulsifier-free emulsion polymerization, using the redox initiator of potassium persulfate (KPS) / N,N-dimethyl ethanolamine (DMEA). The structure and property of PVA were studied by using ubbelohde viscometer, fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy (1H-NMR), X-ray Diffraction (XRD), differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA). The results showed that the viscosity-average degree of polymerization (DP) of PVA 7506, which was much higher than that of PVA commonly used in industrial production. The syndiotacticity and crystallinity of PVA was 54.2 % and 35.6 %, respectively.

scholarly journals Development of novel polystyrene composite beads for defect-free lost foam casting

2021 ◽  
Author(s):  
Satiendra (Uttam) Jagoo
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
High Molecular Weight ◽  
Suspension Polymerization ◽  
Thermo Gravimetric Analysis ◽  
Lost Foam Casting ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Composite Beads ◽  
Lost Foam

The wider adoption of the Lost Foam Casting (LFC) process by the foundry industry has been impeded by the occurrence of fold defects. It is well known that a new foamed polymer, which degrades with less thermal energy (or less endothermic) and produces fewer gaseous pyrolysis products, may be a solution to fold defects. Hence, this pioneering research was an attempt to develop novel polystyrene composite beads for the LFC process through suspension polymerization. Low molecular weight polystyrene composite beads were initially produced, and the presence of the additives inside these beads was confirmed by Energy Dispersive X-ray (EDX) analysis. High molecular weight polystyrene composite beads were then produced. The thermal properties of these low and high molecular weight beads were then produced. The thermal properties of these low and high molecular weight beads were studied using advanced characterization techniques such as a thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that these polystyrene composite beads degrade faster and at lower onset temperatures of degradation than the unmodified polystyrene beads in the LFC industry to reduce casting defects.

scholarly journals Osmometry with single Sephadex beads

1970 ◽  
Vol 119 (1) ◽  
pp. 67-73 ◽  
Author(s):  
A. G. Ogston ◽  
J. D. Wells
Keyword(s):  
Molecular Weight ◽  
Polyvinyl Alcohol ◽  
Osmotic Pressure ◽  
High Molecular Weight ◽  
Molecular Form ◽  
Degree Of Polymerization ◽  
Significant Extent ◽  
Fine Needle ◽  
Single Bead ◽  
Time Required

1. The measurement of osmotic pressure by means of a single bead of Sephadex (Edmond, Farquhar, Dunstone & Ogston, 1968) has been made more precise by immobilizing the bead on a fine needle. The design, calibration and use of the osmometer are described. 2. The method is particularly suitable for measuring high osmotic pressures in solutions of high-molecular-weight solutes, which must not penetrate the Sephadex to a significant extent. 3. With Sephadex G-50 the limit of precision is about 1.5cmH2O and the lower limit of molecular weight for a solute of compact molecular form is about 105. 4. The time required for each equilibration is less than 10min. 5. An impaled bead can be stored in the dry state without affecting its calibration. 6. Measurements on a sample of polyvinyl alcohol, degree of polymerization stated as 1750±50, gave ¯mn 43000±3000 and A2 (6.0±0.24)×10−4.

scholarly journals Development of novel polystyrene composite beads for defect-free lost foam casting

2021 ◽  
Author(s):  
Satiendra (Uttam) Jagoo
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
High Molecular Weight ◽  
Suspension Polymerization ◽  
Thermo Gravimetric Analysis ◽  
Lost Foam Casting ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Composite Beads ◽  
Lost Foam

The wider adoption of the Lost Foam Casting (LFC) process by the foundry industry has been impeded by the occurrence of fold defects. It is well known that a new foamed polymer, which degrades with less thermal energy (or less endothermic) and produces fewer gaseous pyrolysis products, may be a solution to fold defects. Hence, this pioneering research was an attempt to develop novel polystyrene composite beads for the LFC process through suspension polymerization. Low molecular weight polystyrene composite beads were initially produced, and the presence of the additives inside these beads was confirmed by Energy Dispersive X-ray (EDX) analysis. High molecular weight polystyrene composite beads were then produced. The thermal properties of these low and high molecular weight beads were then produced. The thermal properties of these low and high molecular weight beads were studied using advanced characterization techniques such as a thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that these polystyrene composite beads degrade faster and at lower onset temperatures of degradation than the unmodified polystyrene beads in the LFC industry to reduce casting defects.

Construction of Dendritic-Linear Brushes on Silica Nanoparticles by Electrostatic Assembly

2013 ◽  
Vol 652-654 ◽  
pp. 490-494
Author(s):  
Bo Shi ◽  
Liang Liang ◽  
Bo Lin ◽  
Min Hua Qi
Keyword(s):  
Thermo Gravimetric Analysis ◽  
Gravimetric Analysis ◽  
Linear Segment ◽  
Benzyl Ether ◽  
Scanning Calorimetry ◽  
Thermo Gravimetric ◽  
H Nmr ◽  
Electrostatic Assembly ◽  
Before And After ◽  
Assembly Behavior

Using dendritic bromide poly (benzyl ether), G2-Br, as macroinitiator, dendritic-linear polymer (G2-PS-NHSO3Na) was obtained via atom transfer radical polymerization and nucleophilic substitution of G2-PS-Br. G2-PS-NHSO3Na was constructed on cationic silica by both electrostatic attraction and steric effort coming from dendritic block of G2-PS-NHSO3Na. 1H-NMR and differential scanning calorimetry were used to characterize the structure and thermal behavior of G2-PS-NHSO3Na; thermo-gravimetric analysis and TEM were applied to analysis the assembly amount of G2-PS-NHSO3Na and the dispersibility of silica before and after assembly. The results show that G2-PS-NHSO3Na can be synthesized successfully and has exact structure; it can be constructed on cationic silica with 27% assembly amount; the aggregation of silica can be prevented effectively by the dendritic-linear brushes, but the molecular weight of linear segment and the generation of dendritic block will influence the assembly behavior and the amount of the dendritic-linear brushes.

scholarly journals Synthesis, characterization and photoinduced curing of polysulfones with (meth)acrylate functionalities

2010 ◽  
Vol 6 ◽  
Author(s):  
Cemil Dizman ◽  
Sahin Ates ◽  
Lokman Torun ◽  
Yusuf Yagci
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Thermal Gravimetric Analysis ◽  
Gravimetric Analysis ◽  
Condensation Polymerization ◽  
Thermal Gravimetric ◽  
Uv Curable ◽  
H Nmr ◽  
Rate Of Polymerization ◽  
Photo Curing

The UV-curable telechelic polysulfones with (meth)acrylate functionalities were synthesized by condensation polymerization and subsequent esterification. The final polymers and intermediates at various stages were characterized by 1H NMR, FT-ATR, and GPC. The oligomeric films prepared from the appropriate solutions containing these telechelics and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as the photoinitiator undergo rapid polymerization upon irradiation forming insoluble networks. The photo-curing behavior was investigated by photo-DSC and the effects of the molecular weight of the polysulfone precursor and type of functionality on the rate of polymerization and conversion were evaluated. Thermal properties of the photochemically cured films were studied by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA).

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