Volume 33, Issue 6

The polyphenylene sulfide (PPS) blended with polycarbonate (PC), reinforced glass fiber (GF) and nanometer calcium carbonate (nano-CaCO 3 ) filled PPS ternary composite, as well as the PPS/PC/GF/nano-CaCO 3 hybrid composite, were prepared by means of a twin-screw extruder, and the heat distortion temperature ( T d ) of these materials was measured to identify the influence of the PC and nano-CaCO 3 content on the heatproof properties. The T d values for the PPS/PC blend were lower than that of the neat PPS, when the PC weight fraction ( φ PC ) was less than 20%, and increased with increase in φ PC . The T d values for the PPS/GF/nano-CaCO 3 ternary composite, on which the particle surface was treated with a titanate coupler, were higher than that of the composite with the particle surface treated with a stearate coupler. When the nano-CaCO 3 weight fraction ( φ f ) was less than 6%, the T d values for the PPS/PC/GF/nano-CaCO 3 hybrid composites increased with increasing φ f ; at greater than the maximum of 6%, T d decreased. There was a certain synergistic effect of the GF and nano-CaCO 3 on the heatproof properties in the PPS/PC composite.

Elastomer toughened poly(butylene terephthalate) (PBT)/organoclay [Cloisite 30B, organo-montmorillonite (OMMT)] nanocomposites were prepared via melt blending using a micro-compounder. In this work, two types of impact modifiers, ultra low density polyethylene grafted glycidyl methacrylate (ULDPE-g-GMA, IM1) and ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA, IM2) were used, and a detailed comparison of the effect of both was made. With respect to the impact strength, 2 wt% of ULDPE-g-GMA produced a better result as compared to 2 wt% E-MA-GMA. Therefore, 2 wt% of ULDPE-g-GMA is considered as the optimized percentage for the preparation of nanocomposites. Being an impact modifier, ULDPE-g-GMA decreases the yield stress, tensile modulus and breaking strength of pure PBT. This issue was addressed in this paper by using organoclay, which may improve the tensile properties of PBT materials. The content of ULDPE-g-GMA was kept constant, whereas organoclay (OMMT) content was varied from 2 to 5 wt% in nanocomposites. The melting and crystallization behavior of pure PBT, impact modified PBT and its nanocomposites were studied by differential scanning calorimetry (DSC). Crystalline morphology was investigated using polarizing optical microscopy (POM) at 185°C, 195°C, and 205°C crystallization temperatures. The optimum increase in tensile modulus of the elastomer toughened PBT nanocomposites was seen with a 3 wt% addition of organoclay.

Foam extrusion of polypropylene with a foaming agent, Expancel 950 MB 80 and 950 MB 120, was performed. The process was performed using a co-rotating twin screw extruder, with an 18 mm screw diameter and 24 L/D ratio. Dependences of polymer mass flow rate, extrudate foam rate, and polymer pressure on screw speed and foaming agent amount were determined and relevant conclusions were drawn.

Imide ring containing novel polyamide-imides (PAIs) were prepared by triphenyl phosphite-activated polycondensation of phosphorus-containing aromatic amines, bis(3-aminophenyl) isopropyl phosphine (BAP) and bis(3-aminophenyl) aminotolyl phosphine (TAP), with various diimide-diacids (DIDAS). All polymers were fully characterized by FTIR, 1 H-NMR, 13 C-NMR, 31 P-NMR spectroscopy and elemental analysis. These polymers showed no significant weight loss below 419°C and glass transition temperatures (T g ) in the region of 231°C–290°C. The resulting polymeric films exhibited high optical transparency. The inherent viscosity of the synthesized polymers was in the range 0.55–0.85 dl/g and wide angle X-ray diffraction measurements revealed that these polymers were predominantly amorphous.

The graft copolymerization of poly(vinyl acetate) [poly(VAc)] onto starch was studied using the KMnO 4 -H 2 SO 4 redox system. The grafting parameters are favored by changing the concentration of KMnO 4 , the concentration of acid, the temperature, the time, and the concentration of monomer. A maximum graft yield of 38.3% was obtained at optimum conditions: KMnO 4 concentration=3.0×10 -3 mol/l, concentration of acid=1.5×10 -2 mol/l, temperature=40°C, time=3 h, and concentration of monomer=1 mol/l. The grafting of poly(VAc) onto starch was confirmed by the IR spectra of pure sago starch, poly(VAc), and poly(VAc) grafted starch. Both swelling power and solubility increased with the increase in temperature. Graft copolymerization increased swelling power and reduced solubility. This material may have use as an application as a biodegradable plastic.

In this study, α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane was used to prepare waterborne polyurethane-polysiloxane graft copolymer dispersions. α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane was synthesized via hydroxyl protection, alkylation, anionic ring-opening polymerization, hydrosilylation, and deprotection. Waterborne polyurethane-polysiloxane graft copolymers were prepared by the reaction of poly propylene glycol (PPG), toluene diisocyanate (TDI), 2,2-dimethylol propionic acid (DMPA), 1,4-butanediol (BDO), and α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane. The water absorption of copolymer films decreased from 163.9 to 17.3% when polysiloxane content increased from 0 to 5%. The tensile strength of the copolymer films increased from 14.0 MPa to 26.3 MPa and decreased when polysiloxane content was more than 3%. The results revealed that the properties of waterborne polyurethane-polysiloxane graft copolymer dispersions and films were improved by grafting polysiloxane chains to polyurethanes.

Polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) were blended by varying ABS content. The thermal, mechanical and tribological properties of the PC/ABS blends were systematically characterized. Increasing ABS content in the PC/ABS blends decreased thermal stability of the blends, as a result of the lower thermal stability of the ABS than that of the PC. Although the tensile strength of the PC/ABS blends apparently decreased with increased ABS content, the PC/ABS blend with 10 wt% of ABS had the highest tensile strength, because of improved processability of the blend. The friction and wear of the ABS measured against a steel ball of 6 mm in diameter were higher than those of the PC. As a result, a higher ABS content in the PC/ABS blends resulted in higher friction and wear of the blends. The scratch results showed that scratching with a 5 mm steel ball generated a scratch with a shorter length and lower depth on the PC than on the ABS, which indicated better scratch resistance of the PC. Therefore, the PC/ABS blend with 50 wt% of PC had better scratch resistance than the ABS, due to the influence of the PC embedded in the blend.

The effects of aluminum nitride (AlN) and aluminum powder (Al) on thermal conductivity and electrical conductivity of silicone rubber compounds were investigated and it was found that the thermal conductivity increased with increased fillers content. Silicone rubber filled with Al powder of 45 μm over 50 phr, exhibits higher thermal conductivity as compared to that filled with AlN powder of 4 μm at the same filler content. The results indicate that the particle size effect played a significant role on thermal conductivity. In addition, it was found that electrical conductivity and thermal conductivity increased proportionally when the Al powder content increased. In contrast, only the thermal conductivity kept increasing proportionally, but the electrical conductivity almost remained unchanged for the rubber with AlN. Furthermore, a new type of silicone rubber compound with a combination of the two fillers, comprising 100 phr of AlN powder and 50 phr of Al powder, was developed, which lead to synergistic enhancement of the thermal conductivity. The improvement in thermal stability of the new type of silicone rubber compounds enables use in high temperature environments.

A series of acetate starch was synthesized and mixed with bentonite to prepare acetate starch/bentonite composite as a novel additive in order to improve the thixotropic property of cement mortar. The thixotropic index and water retention value of the fresh cement mortar containing acetate starch, bentonite, and acetate starch/bentonite composite, respectively, were measured with and without hydroxypropyl methyl cellulose ether (HPMC). Acetate starch with the degree of substitution (DS) of about 0.5 provided the largest increase in the thixotropic index of the cement mortar. Application of HPMC gave high water retention ability and viscosity to the mortar, but the thixotropic property was not improved. Adding acetate starch or starch/bentonite composite to the mortar can increase its thixotropic index, whereas no significant improvements on the water retention ability and viscosity of mortars were observed. By the combined use of acetate starch/bentonite composite with HPMC, the water retention value (WRV) of the mortar was as high as 98%, and its thixotropic index increased from 4.06 to 5.30, with a high value of viscosity.

Digital cameras are small, but they must be able to take images with numerous pixels. To use few lenses in devices, aspheric lenses have been used. Fluorene-based polymers (FBPs) have a high refractive index and low birefringence. Because optical lenses must be manufactured as designed with low optical retardation, FBP optical lenses are widely used. This study assessed optical and flow characteristics of polycarbonate (PC) and two kinds of FBP. Molded specimen characteristics of PC and two FBPs revealed these properties of the FBPs. The results show that the unique structure of FBPs eliminated birefringence, because of the cardo structure part, including the fluorene ring. Differences in optical properties are attributable to structural differences of the part which is polymerized with the fluorene structure (the X part). The temperature dependence of FBPs in the flow characteristics and optical properties was smaller than that of PC; the slight temperature dependence is particularly obvious above the glass transition temperature ( T g ). The benzene ring content of FBP affects the resin optical and physical properties. The influence of the difference between the fluorene polyester structure and the PC structure was greater than that of the benzene ring content in the X part, in the molecular structure of FBP.

This paper reports the preparation and characterization of newly developed composites consisting of epoxy resin (EP) matrix, polyaniline coated kenaf fiber (KF-PANI) and polyaniline nanowires (PANI-NW). It was shown that the KF-PANI had optimum reinforcing effects and gradually increased electrical conductivity to the EP matrix at 15 wt% loading. Inclusions of PANI-NW to the EP/15KF-PANI composites indicated that the electrical percolation threshold occurred at 5 wt% without significant loss in the mechanical properties. The EP/KF-PANI/PANI-NW revealed conductive composites having good mechanical integrity above the PANI-NW percolation concentration. The Fourier transform infrared (FTIR) and UV-visible spectroscopy studies showed favorable interactions and synergizing effects within the three components.