Thermal stability of polyacrylamide solutions: effect of residual impurities in the molecular-weight-degradation process upon heating

1981 ◽  
Vol 5 (1) ◽  
Author(s):  
Guy Muller
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Degradation Process ◽  
Thermal Stability Of ◽  
Residual Impurities

scholarly journals Physicochemical characteristics of chitosan from swimming crab (Portunus trituberculatus) shells prepared by subcritical water pretreatment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gengxin Hao ◽  
Yanyu Hu ◽  
Linfan Shi ◽  
Jun Chen ◽  
Aixiu Cui ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Sodium Hydroxide ◽  
Subcritical Water ◽  
Physicochemical Characteristics ◽  
Ash Content ◽  
Portunus Trituberculatus ◽  
Swimming Crab ◽  
Water Pretreatment ◽  
Thermal Stability Of

AbstractThe physicochemical properties of chitosan obtained from the shells of swimming crab (Portunus trituberculatus) and prepared via subcritical water pretreatment were examined. At the deacetylation temperature of 90 °C, the yield, ash content, and molecular weight of chitosan in the shells prepared via subcritical water pretreatment were 12.2%, 0.6%, and 1187.2 kDa, respectively. These values were lower than those of shells prepared via sodium hydroxide pretreatment. At the deacetylation temperature of 120 °C, a similar trend was observed in chitosan molecular weight, but differences in chitosan yield and ash content were not remarkable. At the same deacetylation temperature, the structures of chitosan prepared via sodium hydroxide and subcritical water pretreatments were not substantially different. However, the compactness and thermal stability of chitosan prepared via sodium hydroxide pretreatment was lower than those of chitosan prepared via subcritical water pretreatment. Compared with the chitosan prepared by sodium hydroxide pretreatment, the chitosan prepared by subcritical water pretreatment was easier to use in preparing oligosaccharides, including (GlcN)2, via enzymatic hydrolysis with chitosanase. Results suggested that subcritical water pretreatment can be potentially used for the pretreatment of crustacean shells. The residues obtained via this method can be utilized to prepare chitosan.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Effect of Solution Content ZnO Nanoparticles on Thermal Stability of Polyvinyl Chloride

2013 ◽  
Vol 4 (2) ◽  
Author(s):  
Farshad Farahbod ◽  
Narges Bagheri ◽  
Fereshteh Madadpour
Keyword(s):  
Thermal Stability ◽  
Chain Length ◽  
Polyvinyl Chloride ◽  
Zno Nanoparticles ◽  
Degradation Process ◽  
Treatment Conditions ◽  
Thermal Degradation Process ◽  
The Stability ◽  
Thermal Stability Of ◽  
Better Than

Today's pipe made of polyvinyl chloride (PVC) is used as basic good in different industries. The thermal stability of the PVC while is filled with ZnO nanoparticles was studied in this paper. This paper show that the stability of the PVC resin mixed with ZnO nanoparticles solution and Sn was better than that of the PVC resin mixed with Sn alone. The UV (ultraviolet)–vis spectra is showed that under certain heat treatment conditions, the PVC samples without ZnO nanoparticles solution embodied relatively high content of the conjugated double bonds with the chain length of about 3–5. However, the content of the conjugated double bond with the chain length of about 6 was greatly increased when the nanoparticles was filled into the PVC resin. This work shows the ZnO nanoparticles could inhibit the thermal degradation process of PVC resin in ionic mechanism.

scholarly journals Largely enhanced thermal conductivity and thermal stability of ultra high molecular weight polyethylene composites via BN/CNT synergy

RSC Advances ◽  
2019 ◽  
Vol 9 (70) ◽  
pp. 40800-40809
Author(s):  
Yiyou Guo ◽  
Changlin Cao ◽  
Fubin Luo ◽  
Baoquan Huang ◽  
Liren Xiao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermal Stability ◽  
Molecular Weight ◽  
Boron Nitride ◽  
Thermal Conduction ◽  
Conduction Path ◽  
Ultra High Molecular Weight ◽  
Thermal Stability Of ◽  
Enhanced Thermal Conductivity

The carbon nanotubes (CNTs) synergistically assist boron nitride microsheets (BNs) to form a more continuous and effective thermal conduction path.

scholarly journals Investigation on the Properties of PMMA/Reactive Halloysite Nanocomposites Based on Halloysite with Double Bonds

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 919 ◽  
Author(s):  
Shiwei Chen ◽  
Zhizhou Yang ◽  
Fuzhong Wang
Keyword(s):  
Mechanical Property ◽  
Thermal Stability ◽  
Molecular Weight ◽  
Polymer Nanocomposites ◽  
Moisture Absorption ◽  
Young Modulus ◽  
Double Bonds ◽  
Scanning Calorimetry ◽  
General Applicability ◽  
Thermal Stability Of

PMMA/reactive halloysite nanocomposites were firstly prepared using reactive halloysite with double bonds. The halloysite was functionalized to improve its dispersion in the polymer matrix. The reactive halloysite could increase the molecular weight of PMMA. The molecular distribution of PMMA/reactive halloysite nanocomposite was more uniform than that of PMMA. The moisture absorption of PMMA/reactive halloysite nanocomposite increased with the addition of the reactive halloysite. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) confirmed that the thermal stability of PMMA/reactive halloysite nanocomposites was greatly enhanced. Significant improvement in the mechanical property of PMMA nanocomposites was achieved by the addition of 3 wt % reactive halloysite. A 31.1% increase in tensile strength and a 64.2% increase in Young’ modulus of the nanocomposites with 3 wt % of the reactive halloysite were achieved. Finally, the formation mechanism of PMMA/reactive halloysites nanocomposites was proposed. This approach demonstrated the potential for general applicability to other polymer nanocomposites.

scholarly journals Synthesis, Characterization and Copolymerization of N-(phenylamino)maleimide with MMA

2007 ◽  
Vol 4 (2) ◽  
pp. 265-271
Author(s):  
B. L. Hiran ◽  
S. N. Paliwal ◽  
Jyoti Choudhary ◽  
P. R. Choudhary
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Density Measurement ◽  
Gel Permeation Chromatography ◽  
Radical Copolymerization ◽  
Free Radical Copolymerization ◽  
H Nmr ◽  
Gel Permeation ◽  
Ft Ir ◽  
Thermal Stability Of

The free radical copolymerization of N-(phenylamino)maleimide (N-PAMI) was carried. The copolymerization with methyl methacrylate (MMA) was performed at 65°C with AIBN as the initiator in THF solvent. Resulting copolymer was characterized by density measurement, intrinsic viscosity, solubility, FT-IR &1H NMR spectroscopy. Effect of the solvent and time on copolymer yield was also investigated. The molecular weight of copolymer was determined by gel permeation chromatography (GPC). The thermal stability of copolymer was determined by Thermogravimetric analysis (TGA).

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