Guozheng Liang

Modification of polyaralkyl–phenolic resin and its copolymer with bismaleimide

Polyaralkyl–phenolic resin, whose commercial name is Xylok, is in the class of high-performance resins, but its slow reactivity and brittleness limit its application in modern industry. Many efforts have been made to modify Xylok, but have not satisfactorily resolved these problems. In this paper, the authors employ allylization to improve properties of Xylok. The allyl Xylok can be thermally polymerized by itself or with bismaleimide (BMI) as a good comonomer. The reactivity of the allyl Xylok/BMI resin system was investigated by gel characteristics and differential scanning calorimetry (DSC). The thermal stability of the cured copolymer was evaluated by dynamic thermogravimetric analysis (TGA). No weight loss was observed when the copolymer was heated to 490–500°C in a nitrogen atmosphere. The hot/wet resistance properties of the cured allyl Xylok/BMI resin were investigated by aging it in boiling water. After aging for 100 h, water absorption and heat deflection temperature (HDT) were 2.3% and 280°C, respectively. The properties of the glass fiber reinforced compression molding materials (GCM) based on the copolymer of the allyl Xylok/BMI matrix resin system are also discussed.

Novel modified bismaleimide resins with improved ablativity

To improve the ablativity of bismaleimide-type resins, a series of novel allyl compounds containing boron in their molecular structure, designated as ACB, were synthesized and characterized. The copolymers made up of 4,4-bismaleimidodiphenyl methane (BDM) and each ACB were prepared. The properties of the prepolymers and cured resins were all studied in detail. Results show that the prepolymers of BDM/ACB systems have similar processing characteristics such as solubility in acetone and reactivity to those of ordinary BMI resins made up of BDM and allyl compounds without boron, such as the famous BDM/BA (O,O-diallylbisphenol A) system, while the thermal resistance and ablativity of the former are better than those of the latter. Thermogravimetric analysis (TGA) in a nitrogen atmosphere revealed that the BDM/ACB systems were stable up to 480°C and their char yields at 800°C under anaerobic conditions were more than 50%. However, the char yield at 700°C of the BDM/BA system is only about 21%.

A high-performance bismaleimide resin with good processing characteristics

A new bismaleimide (BMI) resin system, designated 4504, with excellent heat resistance and good mechanical properties for advanced composites was developed. The 4504 resin was made up of 4,4′-bismaleimidodiphenyl methane, diallyl bisphenol A, and desirable catalysts. The reactivity of 4504 was investigated by gel characteristics and differential scanning calorimetry (DSC). Data showed that 4504 had a long work life under 100°C, but would gel within 7 min or 40 s at 140 or 160°C, respectively. The glass transition temperature (Tg) and heat-deflection temperature (HDT) of the cured 4504 resin were 315 and 290°C, respectively, which were much higher than the postcure temperature (200°C). In addition, the cured resin is also tough. Thermogravimetric analysis (TGA) in a nitrogen atmosphere revealed that the neat resin was stable up to 450°C; its char yield at 700°C under anaerobic conditions was 29.4%. Carbon fiber T300 laminates based on 4504 were prepared and characterized. In the case of short-beam (SBS) strength, when tested at 230°C, 51% of the original room temperature strength was retained.

New bismaleimide resin with improved tack and drape properties for advanced composites

In order to improve the tack and drape properties of prepregs based on bismaleimide (BMI) resins, a new allyl compound containing diglycidyl ether of bisphenol A backbone, designated as AE, was prepared by reacting m-allylphenol (1 mol) with an equimolar amount of diglycidyl ether of bisphenol A (0.5 mol). The copolymer of BMI/AE was prepared and characterized. The softening point of the copolymer is lower than room temperature. The prepregs based on BMI/AE have very good tack and drape properties and a long work life (three weeks) at room temperature. Thermogravimetric analysis (TGA) in nitrogen atmosphere revealed that the cured copolymer was stable up to 515°C. The hot/wet resistance properties of the cured copolymer were investigated by aging it in boiling distilled water. After aging for 100 h, the water absorption and heat defleation temperature (HDT) were 3.6% and 248°C, respectively. In addition, the cured copolymer has good mechanical properties at ambient and elevated temperature.

Interactions in organic rectorite composite gel polymer electrolyte

Abstract Rectorite (REC) was modified with dodecyl benzyl dimethyl ammonium chloride (1227) to form an organic-modified rectorite, termed OREC. The OREC was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of polymethyl methacrylate (PMMA), propylene carbonate (PC) and LiClO4. Studies of ionic conductivity and viscosity of liquid electrolytes and pure PC, respectively, clearly showed that these properties are greatly influenced by temperature and the amount of OREC added; a consequence of the interactions between the components of CPEs. The Fourier transform infrared (FTIR) spectroscopy results indicated that there were two kinds of interaction: namely (1) a strong hydrogen bond between Si-OH and C=O of PC and (2) a weak interaction between Li+ and C=O. Inverse gas chromatography (IGC) research supported the FTIR interpretation, indicating that the two interactions exist and that the H bond is the stronger of the two. In CPEs, the polymer matrix of PMMA merely supports the active components and does not influence the interactions between them. The OREC greatly increased the crucial plasticizer maintenance property when the amount of clay added was optimum.

Gel polymer electrolyte based on the synthesized co-polymer of poly(methyl methacrylate-maleic anhydride)

Abstract In this study, poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)) was synthesized in toluene from methyl methacrylate (MMA) and maleic anhydride (MAh) monomers via free radical polymerization, in the presence of 2,2’-Azo-bis-isobutyronitrile (AIBN), as initiator at 80ºC for 8 h. The molar ratio of monomers was found to be 1 MAh:8 MMA using hydrolysis and titration. The molecular weight of co-polymer was determined to be of the order of 104 (g/mol) by gel permeation chromatography. The co-polymer was characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopy. Thermogravimetric analysis indicated the initial decomposition temperature was ~270ºC. Differential scanning calorimetry indicated that the glass transition temperature was near 126ºC. Rectorite modified with benzyldimethyldodecylammonium chloride (OREC) was used as an additive to modify gel polymer electrolytes (GPEs) which consisted of P(MMA-MAh) used as a polymer matrix, propylene carbonate (PC) as a plasticizer and LiClO4 as the lithium ion source. X-ray diffraction analysis indicates that OREC can exfoliate well in GPEs when the amount of clay is suitable. The temperature dependence of the ionic conductivity of the resulting GPEs agreed well with the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr resulted in the greatest ionic conductivity. This OREC addition considerably improved the plasticized retention levels. As a consequence of OREC occupying the free volume space in the polymer matrix of GPEs, the bulk resistance of the GPEs was reduced and the glass transition temperature (Tg) increased.