Materials Science Forum Vol. 848

Abstract: PMMA-BMA oil absorption resin was prepared by dispersion polymerization. Oil absorption properties were adjusted by changing the monomer ratio, content of initiator and crosslinking agent. Absorption capacity of porous material, which PMMA-BMA oil absorption resin adhesive in the polyurethane surface, was also investigated. The experimental results show that the best oil absorption ratio of PMMA-BMA copolymer resin was obtained when the MMA/BMA mole ratio was1:1.5, and the initiator and crosslinking agent was 0.4% and 0.35% of the copolymer resin respectively. The porous material was fabricated using the porous polyurethane sponge dipped in the liquid copolymer resin. The porous material resin can be reused since its low oil retention rate, and it can be used as absorption container of oil vapor.

Abstract: Multiwalled carbon nanotubes (MWCNT)-reinforced polymerized cyclic butylene terephthalate (pCBT) nanocomposites were prepared by in situ ring opening polymerization of cyclic butylene terephthalate oligomers (CBT). The results of differential scanning calorimetry (DSC) indicated that the melting peak located at the low temperature (Tm1) increased and that at higher temperature (Tm2) decreased with the increasing of content of the MWCNT. During the cooling the MWCNT served as nucleation points from where crystallization can start. The more the MWCNT in the system the earlier the crystallization starts. The Morphological investigations performed by scanning electron microscopy (SEM) shown that the MWCNT were embedded in the matrix and held tightly by the matrix. The modulus and strength increased with MWCNT concentration in the nanocomposites, however, the elongation at break, absorbed energy at break and impact strength were decreased with the increasing of MWCNT content.

Abstract: Liquid crystalline polyurethanes (LCPU) were prepared from 4,4’-methylenediphenyl diisocyanate (MDI), 1,6-hexanediol (HDO), 2,2-dimethylol propionic acid (DMPA) and polytetramethylene ether glycol (PTMG). The experiments synthesized three liquid crystalline polyurethane films with different soft/hard segment ratio. Chemical and structural characterization of the polyurethanes were investigated by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, differential scanning calorimeter and polarized microscopy respectively. Swelling rate and shape memory property were tested. The results indicated that the polyurethane with 62% soft segment and large group of carboxyl displayed excellent swelling and shape memory properties, and the shape recovery rate reached 100%. It was found that the crystallinity, thermal stability decreased and the temperature flexibility, water absorption and shape recovery rate increased with the increase of polytetramethylene ether glycol.

Abstract: Ionic polyurethane (IPU) was synthesized as shape memory materials. Poly (tetramethylene ether) glycol with 2000g/mol number average molecular weight were used as soft segment, 4,4-methylenebis (phenyl isocyanate), and 1,2-dihydroxy-3-propanesulfonic acid salt were used to compose the segment of SMP materials. The structure and properties of these IPU films were characterized by Fourier Transform infrared, X-ray diffraction, Thermal gravimetric analysis and Differential scanning calorimeter. The results showed that the glass transition temperature of the IPU increased with the increase of hard segment content. The physical properties in terms of swelling property, water absorption and ion-exchange capacity increased with the improving of sulfonic group content in IPU. The shape memory property of IPU exhibited that the shape fixity ratio and recovery rate improved remarkably with the increase of hard segment content.

Abstract: In this study, a method of recycling spent coffee grounds (SCG) is introduced. The SCG was dried and crushed into micron-sized coffee particles. The coffee particles could be used to prepared polyurethane (PU) films with different contents (0wt.%, 5wt.%, 10wt.%, 15wt.%, 20wt.%, 25wt.% and 30wt.%). The anti-ultraviolet property, thermal comfort performance and mechanical property of different PU films were measured. The results showed that after the blending of coffee particles, the films exhibited excellent anti-ultraviolet property and thermal comfort performance, and the mechanical properties were also retained. This study also provided an effective approach to reuse SCG, which is consistent with the environmental-friendly society principle.

Abstract: Nitrogen fertilizer is an important nutrition for the crops. However, the majority of common nitrogen fertilizers have not been absorbed by the plant, which causes great economical loss and environment pollution. In order to solve the above problem, the biodegradable slow-release coating materials for urea was prepared by introducing the active free radical of short chain cassava starch into concentrated natural rubber latex. The effects of the amount of starch, modifier dosage on the water absorption kinetics of natural rubber latex slow-released film, and the mechanical properties, slow-released performance, thermal stability and mildew characteristics in the tropical climate conditions was also examined. The results showed that the swelling rate of natural latex composite film increased with the increment of starch content. However, the water modifier imposed a different effect on the initial swelling rate and the equilibrium-swelling ratio of latex composite film. The preliminary swelling was slow but the time for achieving a basic balance state of the swelling was short. In addition, the thermal degradation process of the natural rubber latex slow-released composite film was divided into two stages. The maximum heat loss temperature of each stage shift toward the each other due to the increasing dosage of water modifier. The biodegradability of the composite film improved but the release rate of urea got faster when the starch content increased.

Abstract: A series of MDI-50 based non-ionic waterborne polyurethane dispersions (MDI-NPUD) were prepared by the mixing of 2,4’-diphenylmethane diisocianate (2,4’-MDI) and 4,4’-MDI (MDI-50) which reacted with hydroxylated tung oil (HTO) and polyethylene glycol-800 (PEG-800), Fourier Transform Infrared Spectroscopy (FTIR) and Proton-Nuclear Magnetic Resonance (¹H-NMR) were used to characterize and analyze their molecular structures. The results indicated that MDI-50 and HTO were introduced as hard segment while PEG acted as soft segment. The surface tension, Hydrophile-Lipophile Balance (HLB) and stability were investigated. All MDI-NPUDs had much lower surface tension than the dicyclohexyl methane diisocyanate (HMDI) based NPUD (HMDI-NPUD). By changing the feed ratio of MDI-NPUD, the properties of MDI-NPUD could be controlled

Abstract: A series of addition-type imide oligomer (degree of polymerization: n=1-9) derived from 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA), 3,4'-oxydianiline (3,4'-ODA) and 4-phenylethynylphthalic anhydride (PEPA) was synthesized by thermal imidization. The resultant oligomers were characterized for their chemical architecture, thermal property, and processability. The experimental results showed that oligomers PI-1 and PI-2 had somewhat crystalline phase. PI-4, PI-6 and PI-9 exihibited high solubility in solvents. These imide oligomers have a very low melt viscosity, and thus provide wide processing window by the rheological behaviors. Furthermore, the cured polyimides exhibited excellent thermal stability under N₂ atmosphere. The temperatures of 5% weight loss in N₂ atmosphere were all above 524°C.

Abstract: In this paper, both the permittivity and the microwave transmittance properties of organosilicon-matrix composites under different temperatures have been studied. In order to investigate the reason for the changing of dielectric property, both TGA and high-temperature dielectric spectrum measurement have been carried out. A theoretical model of radome, with a temperature gradient distribution, has been built to analyze the dependence of microwave transmittance property on temperature. Based on the experimental results, we can optimize the effective operating temperature of this kind of organosilicone-matrix composites.

Abstract: The thermotropic liquid crystal copolyester P-BPA2.5 and P-BPAF2.5 with low melting temperature and high glass transition temperature were obtained by introducing 2.5mol% bisphenol A (BPA), bisphenol AF (BPAF) and terephthalic acid (TA) receptively into the molecular chain of poly (oxybenzoate-co-oxynaphthoate). The isothermal and nonisothermal degradation behavior of the two copolyesters P-BPA2.5 and P-BPAF2.5 were studied by thermo-gravimetry analysis (TGA) under nitrogen atmosphere. The degradation kinetics of the copolyesters under dynamic and isothermal heating conditions was evaluated byKissinger-Akahira-Sunose (KAS) and iso-conversional methodrespectively. Results showed that the activation energy (E) values followed the order P-BPAF2.5>P-BPA2.5 under dynamic heating atmosphere. However, the P-BPA2.5 showed a better thermal stability as compared with P-BPAF2.5 under isothermal heating conditions. The differences of degradation mechanism between the two copolyesters may be a reason for this phenomenon, which was discussed in detail in the text.