Jungang Gao

Structure of a boron-containing bisphenol-F formaldehyde resin and kinetics of its thermal degradation

Abstract The structure and thermal degradation of a boron-containing bisphenol-F formaldehyde resin (BBPFFR) synthesized by the formalin method have been studied. The results showed that a six-membered ring containing boron–oxygen coordinate linkage was formed in the thermosetting process, and the coordinated oxygen atom was provided by the phenolic hydroxyl. The degradation of this resin began with the oxidation and breakage of ether linkages and carbonyl groups. The kinetic parameters of thermal degradation were determined by thermogravimetric analysis.

Thermal stability of boron-containing phenol formaldehyde resin

The boron-containing phenol-formaldehyde resin derived from phenol, formaldehyde and boric acid was synthesized. The mechanisms of synthesis and curing reactions were investigated by infrared spectroscopy and chemical analysis. The kinetics of thermal degradation and thermal stability were determined by thermal analysis. The results show that the resin has higher heat oxidation resistance than common phenol-formaldehyde resins. In addition, the fiberglass-reinforced laminate has good mechanical and electric properties.

Thermal properties and stability of boron-containing phenol-formaldehyde resin formed from paraformaldehyde

A boron-containing phenol-formaldehyde resin (BPFR) was synthesized from boric acid, phenol and paraformaldehyde. The structure change of BPFR during curing was studied by Fourier-transform infrared (FTIR) spectroscopy. The glass transition temperatures (Tg) were determined by differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The thermal degradation of BPFR was studied by FTIR and thermogravimetry analysis (TGA). The results indicate that the degradation of BPFR begins with the breaking of B–O bonds. The TGA results show that the dynamic thermal degradation of BPFR appears as four reaction stages in nitrogen and three in static air. The kinetic analysis results show that the reaction follows a first order mechanism to the second and third stages in air, and first order to the second stage and third order to the third and fourth stages in nitrogen.

Liquid Crystalline Phase Behavior and Sol–Gel Transition in Aqueous Halloysite Nanotube Dispersions

The liquid crystalline phase behavior and sol-gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol-gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects.

Kinetics of Curing and Thermal Degradation of POSS Epoxy Resin/DDS System

Polyhedral oligomeric silsesquioxanes epoxy resin (POSSER) was prepared from 3-glycidypropyl-trimethoxysilane (GTMS) and tetramethylammonium hydroxide (TMAH) by hydrolytic condensation. POSSER was characterized using Fourier-transformed infrared spectroscopy (FTIR), 1H-NMR, and liquid chromagraphy/mass spectrometry (LC/MS). The epoxy value of POSSER is 0.50 mol/100 g. The LC/MS analysis indicated that T10 is the majority and contain some amount of T8, besides, a trace T9 also exists. The curing kinetics of POSSER with 4,4′-diaminodipheny sulfone (DDS) as a curing agent was investigated by means of differential scanning calorimetry (DSC). The curing reaction order n is 0.8841 and the activation energy Ea is 61.06 kJ/mol from dynamic DSC analysis. Thermal stability and kinetics of thermal degradation were also studied by thermal gravimetric analysis (TGA). TGA results indicated that the temperature of POSSE/DDS system 5% weight loss is approximately 377.0°C, which is higher by 12.6°C than that of pure POSSER, and the primary degradation reaction (300–465°C) followed first order kinetics; the activation energy of degradation reaction is 75.81 kJ/mol.

Synthesis and Structure Characterization of Boron-Nitrogen Containing Phenol Formaldehyde Resin

ABSTRACT A boron-nitrogen modified phenol formaldehyde resin (BNPFR) was prepared from phenol, formalin, ammonia water, n-butyl alcohol, boric acid, and paraformaldehyde. The reaction mechanism and structure of BNPFR during the synthesis and curing process were investigated by FTIR, NMR. The thermal stability was determined by thermogravimetric analysis. The results showed that borate, ether linkage, methylene bridges, and hexatomic ring containing coordinate linkage of boron-nitrogen were formed mostly in the synthesis and thermosetting process. The carbonyl group was formed in the synthesis and curing process at higher temperature. The initial thermal degradation temperature of BNPFR is 100°C higher than common phenol formaldehyde resin (PFR).

Dynamic Rheological Behavior and Mechanical Properties of PVC/O-POSS Nanocomposites

The PVC/Polyhedral oligomeric silsesquioxanes containing octyl groups (O-POSS) nanocomposites were prepared. Plastic behavior and dyanmic rheology of nanocomposites were investigated. Influences of composition on storage modulus, loss modulus and complex viscosity were discussed. The mechanical properties and morphology were determined. The results show that both plastic time and balance torque of nanocomposites all decreased when O-POSS was added. The impact strength of nanocomposites can increase 8kJ/m2 when O-POSS content is 1.5 wt%, but the T g is not decreased. The O-POSS can be used as an efficient process aid and impact aid for PVC at low content.

Nonisothermal Curing Kinetics and Physical Properties of Unsaturated Polyester Modified with EA-POSS

The polyhedral oligomeric silsesquioxanes (EA-POSS) which contain epoxy acrylate group were synthesized from 3-glycidypropyl-trimethoxysilane (GTMS) and acrylic acid in two steps: hydrolytic condensation of GTMS and esterification of polyhedral oligomeric silsesquioxanes epoxy resin (POSSER) with acrylic acid under appropriate conditions. The unsaturated polyester resin (UPR) was mixed with EA-POSS at different proportions, and the cure kinetics were investigated by nonisothermal differential scanning calorimetry (DSC) technique. The results show that UPR, the methyl methacrylate and EA-POSS have very good compatibility and can co-cure in free radical polymerization. The curing reaction can be described by a two-parameter autocatalytic Šesták-Berggren (S-B) model and kinetic equations are obtained. The reaction rate is increased with the addition of EA-POSS. The electrical properties of fiberglass-reinforced laminates, thermal stability and dynamic mechanical properties of EA-POSS/UPR nanocomposites were determined. The results indicate that these properties are all modified after EA-POSS is added to the UPR. The mechanical loss peak temperature Tp increases by about 30–35°C and the initial decomposition temperature increases by about 15°C.

Rheological Behavior and Mechanical Properties of Blends of Poly(vinyl chloride) with CP-POSS

In this work, a polyhedral oligomeric silsesquioxane which contains 3-chloropropyl groups (CP-POSS) was synthesized. The rheological behavior of CP-POSS/PVC blends was investigated by torque rheometer and capillary rheometer. Mechanical properties were investigated by electronic material tester. Influences of blending composition, shear rate and shear stress on melt apparent viscosity and non-Newtonian index (n) were discussed. The results show that the plastic time decreases and melt viscosity increases with increasing content of CP-POSS. CP-POSS has a good compatibility with PVC. The blend has the best impact strength when the content of CP-POSS is 7 wt%. The CP-POSS can be used as a processing aid and impact-resistant aid for PVC.

UV-Curable Coating of Unsaturated Polyester/Epoxy Resins Containing Polyhedral Oligomeric Silsesquioxanes

UV-curable coating of unsaturated polyester/epoxy resin (UP-ER) modified with methylacryloylpropyl polyhedral oligomeric silsesquioxanes (MAP-POSS) was prepared. The UV-cured process, kinetics, and some properties of coating were investigated. The results show that this coating has a better UV-curing property. The curing reaction can be described by a two-parameter autocatalytic Šesták-Berggren (S-B) model. The mechanical loss peak temperature T p of curing coating nanocomposites increased with increasing MAP-POSS content and has a highest value when MAP-POSS content is 12%, which is 121.8°C, and higher, about 18.3°C, than a pure UP-ER system. The coating film has lower volume shrinkage than pure UP-ER.