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1.
Extrudate swell behavior of polystyrene (PS) and linear low‐density polyethylene (LLDPE) melts was investigated using a constant shear rate capillary rheometer. Two capillary dies with different design configurations were used, one being a single flow channel and the other being a dual flow channel. A number of extrudate swell related parameters were examined, and used to explain the discrepancies in the extrudate swell results obtained from the single and dual flow channel dies, the parameters including output rate and output rate ratio, power law index, wall shear rate, wall shear stress, melt residence time, pressure drop induced temperature rise, flow channel position relative to the barrel centerline, and the flow patterns. It was found in this work that the power law index (n value) was the main parameter to determine the output rate ratio and the extrudate swell between the large and small holes for the dual flow channel die: the greater the n value the lower the output rate ratio and thus decreased extrudate swell ratio. The differences in the extrudate swell ratio and flow properties for PS and LLDPE melts resulted from the output rate ratio and the molecular chain structure, respectively. The extrudate swell was observed to increase with wall shear rate. The discrepancies in the extrudate swell results from single and dual dies for a given shear rate were caused by differences in the flow patterns in the barrel and die, and the change in the melt velocities flowing from the barrel and in the die to the die exit. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1713–1722, 2003 相似文献
2.
Simple blending of natural rubber/ethylene–propylene–diene rubber (NR/EPDM) generally results in inferior mechanical properties because of curative migration and their differences for filler affinity. In this work, the 70/30 and 50/50 NR/EPDM blends prepared by reactive processing techniques were investigated and compared with the simple, nonreactive blends. The reactive blend compounds were prepared by preheating EPDM, containing all curatives to a predetermined time related to their scorch time prior to blending with NR. For the 70/30 gum blends, four types of accelerators were studied: 2,2‐mercaptobenzothiazole (MBT), 2,2‐dithiobis‐ (benzothiazole) (MBTS), N‐cyclohexyl‐2‐benzothiazolesulfenamide (CBS), and N‐tert‐butyl‐2‐benzothiazolesulfenamide (TBBS). When compared with the simple blends, the reactive blends cured with CBS and MBTS showed a clearly improved tensile strength whereas the increase of tensile strength in the blends cured with TBBS and MBT was marginal. However, a dramatic improvement of ultimate tensile properties in the reactive 50/50 NR/EPDM blends cured with TBBS was observed when compared with the simple blend. For the N‐550‐filled blends at the blend ratios of 70/30 and 50/50, the reactive‐filled blends prepared under the optimized preheating times demonstrated superior tensile strength and elongation at break over the simple blends. The improved crosslink and/or filler distribution between the two rubber phases in the reactive blends accounts for such improvement in their mechanical properties. This is shown in the scanning electron micrographs of the tensile fractured surfaces of the reactive blends, which indicate a more homogeneous blend. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
3.
Graft copolymer of natural rubber and N-(4-hydroxyphenyl)maleimide (i.e., NR-g-HPM) was synthesized. It was found that the grafting yield increased upon increasing the grafting temperature and the highest grafted HPM content was obtained at 200 °C. Furthermore, increases in concentration of HPM led to drop in grafted HPM. Therefore, an optimum grafting temperature and dose of HPM were found to be 200 °C and 2 phr, respectively. Dynamically cured 60/40 NR-g-HPM/PP blends with various loading levels of HPM in graft copolymerization were then achieved by dynamic vulcanization. It was found that the blend with 2 phr of HPM exhibited the highest tensile strength, elongation-at-break, mixing torque during dynamic vulcanization, storage modulus and complex viscosity and the lowest tension set (i.e., the highest elasticity). This was attributed to the highest grafted HPM which created greater possibility to form linkage between NR-g-HPM and the phenolic modified PP compatibilizer molecules which promoted easier interactions between the blend components. TGA analysis found that the NR-g-HPM/PP blends exhibited two stages of weight loss while the pure PP exhibited a single stage. Furthermore, the NR-g-HPM/PP blend exhibited higher degradation temperature than that of the unmodified NR/PP blend which was the confirmation of higher heat resistance of NR-g-HPM. 相似文献
4.
Effects of in‐situ functionalization of carbon nanotubes with bis(triethoxysilylpropyl) tetrasulfide (TESPT) and 3‐aminopropyltriethoxysilane (APTES) on properties of epoxidized natural rubber–carbon nanotube composites
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Yeampon Nakaramontri Charoen Nakason Claudia Kummerlöwe Norbert Vennemann 《Polymer Engineering and Science》2015,55(11):2500-2510
Composites of carbon nanotubes (CNT) and epoxidized natural rubber (ENR) were prepared by in‐situ functionalization of CNT with two alternative silane coupling agents: bis(triethoxysilylpropyl) tetrasulfide (TESPT) and 3‐aminopropyltriethoxysilane (APTES). The reactions of ENR molecules with the functional groups on CNT surfaces and with the silane molecules were characterized by Fourier transform infrared. Furthermore, cross‐link density, relaxation behaviors, curing, mechanical, electrical, and morphological properties of pristine ENR and the ENR composites were investigated. Very low percolation thresholds, at CNT concentrations as low as 1 phr, were observed in the ENR–CNT and the ENR–CNT–TESPT composites. This might be attributed to improvements in the chemical linkages between ENR molecules and functional groups on CNT surfaces that led to a homogenous dispersion of CNTs in the ENR matrix, with loose CNT agglomerates. POLYM. ENG. SCI., 55:2500–2510, 2015. © 2015 Society of Plastics Engineers 相似文献
5.
Natural rubber grafted with poly(dimethyl(methacryloyloxymethyl)phosphonate) (i.e., NR‐g‐PDMMMP) was prepared in latex medium via photopolymerization. Thermal and flame resistance properties of the NR‐g‐PDMMMP prepared with various levels of grafted PDMMMP or grafting rate (GR) were investigated. Thermal behaviors were investigated by thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). It was found that the graft copolymer exhibited phase separation with double Tg values. A shift of Tgs toward each other was observed with increasing GR, which indicated tendency to become a single phase material. Increasing GRs also caused increasing heat and flame resistance with increasing degradation temperature and level of char residue. Furthermore, increasing level of limited oxygen index (LOI) and decreasing burning rate were observed with increasing the GR. This is attributed to increasing content of char residue of the phosphorus compound, which acted as the thermal insulation and a barrier of oxygen to transfer to the burning materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
6.
Mechanical, dynamic, thermal, and morphological properties of dynamically cured 60/40 NR/PP TPVs with various loading levels of paraffinic oil were investigated. It was found that stiffness, hardness, tensile strength, storage shear modulus, complex viscosity, glass transition temperature (Tg) of the vulcanized rubber phase, degree of crystallinity and crystalline melting temperature (Tm) of the polypropylene (PP) phase decreased with increasing loading levels of oil. This is attributed to distribution of oil into the PP and vulcanized rubber domains causing oil‐swollen amorphous phase and vulcanized rubber domains. An increasing trend of elastic response in terms of tension set and damping factor was observed in the TPVs with loading levels of oil in a range of 0–20 phr. It is supposed that a major proportion of oil was first preferably migrated into the PP phase and caused an abrupt decreasing trend of degree of crystallinity and Tm of the PP phase. The dispersed vulcanized rubber domains remained small as particles with a low degree of swelling. Increasing loading levels of oil higher than 20 phr caused a decreasing trend of elongation at break and elastomeric properties. Saturation of oil in the PP phase was expected and the excess oil was transferred to the rubber phase which thereafter caused larger swollen vulcanized rubber domains. The remaining amount of oil was able to separate as submicron pools distributed in the PP matrix. This caused lowering of Tg, Tm, crystallinity of PP phase as well as strength, elastomeric, and dynamic properties of the TPVs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
7.
Warapong Krengvirat Srimala Sreekantan M. N. Ahmad-Fauzi Charoen Chinwanitcharoen Go Kawamura Atsunori Matsuda 《Journal of Materials Science》2012,47(9):4019-4027
The volatilization of bismuth (Bi) species and bismuth oxide (Bi2O3) leads to the presence of the oxygen vacancies (V
O00) and consequently restrains the properties of bismuth titanate (BIT; Bi4Ti3O12). This report presents the incorporation of different atomic ratios of praseodymium ion (Pr3+: x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) into the BIT (Bi4−x
Pr
x
Ti3O12) ceramics through an intermediate fuel agent-assisted self-combustion synthesis (IFSC). X-ray diffraction and Raman spectroscopy
results revealed that some of bismuth ion (Bi3+) in the pseudo-perovskite layer containing Ti–O octahedra was substituted by Pr3+ ion. The substitution by ion with a smaller ionic radius caused the structure distortion and consequently resulted in the
phase transformation from an orthorhombic symmetry to a tetragonal symmetry. Besides, it suppressed the volatilization of
Bi and Bi2O3 and increased the stability of metal–oxygen octahedra in the BIT. These play a crucial role to control the crystal growth,
as well as limit the V
O00. Dense ceramic with a relative density up to 96.2% was obtained by incorporating Pr3+ with atomic ratio of 1.0. It exhibited high dielectric constant as 908.19 and low dissipation factor as 0.0011. The results
address the possibility to control the structure, morphology and dielectric properties of BIT ceramic by incorporating Pr3+ ion through IFSC. 相似文献
8.
Charoen Nakason Methakarn Jarnthong Azizon Kaesaman Suda Kiatkamjornwong 《应用聚合物科学杂志》2008,109(4):2694-2702
Epoxidized natural rubber (ENR) with a level of epoxide groups of 20 mol % was prepared via the performic epoxidation method. It was then used to blend with high‐density polyethylene (HDPE) at various blend ratios. Three types of blend compatibilizers were prepared. These included a graft copolymer of HDPE and maleic anhydride (MA; i.e., HDPE‐g‐MA) and two types of phenolic modified HDPEs using phenolic resins SP‐1045 and HRJ‐10518 (i.e., PhSP‐PE and PhHRJ‐PE), respectively. We found that the blend with compatibilizer exhibited superior tensile strength, hardness, and set properties to that of the blend without compatibilizer. The ENR and HDPE interaction via the link of compatibilizer molecules was the polar functional groups of the compatibilizer with the oxirane groups in the ENR molecules. Also, another end of the compatibilizer molecules (i.e., HDPE segments) was compatibilizing with the HDPE molecules in the blend components. The blend with compatibilizer also showed smaller phase morphology than the blend without compatibilizer. Among the three types of the blend compatibilizer, HDPE‐g‐MA provided the blend with the greatest strength and hardness properties but the lowest set properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
9.
Methakarn Jarnthong Charoen Nakason Natinee Lopattananon Zheng Peng 《Polymer Composites》2012,33(11):1911-1920
Thermoplastic natural rubber nanocomposites based on epoxidized natural rubber (ENR) and polypropylene blends at a fixed blend ratio of 50/50 wt% reinforced with small amount (2.5 wt%) of nanosilica (SiO2) were prepared by melt‐mixing through three different incorporation sequences in an internal mixer. The effects of incorporation techniques on morphology, crystallization behavior, mechanical properties, dynamic, rheological characteristics, and thermal resistance of thermoplastic natural rubber (TPNR) nanocomposites were investigated. It was found that the dispersion of nanosilica in TPNRs was significantly dependent on the incorporation sequence. In the case where SiO2 was premixed in ENR before blending with polypropylene (PP), the final morphology showed the good dispersion of SiO2 in ENR phase, while the SiO2 particles were localized near the PP interface when SiO2 was premixed the in PP first. Whereas, when the three components were simultaneously mixed, the SiO2 particles were mainly dispersed in the PP phase. It was also found that the improvements of Young's modulus, tensile strength, damping behavior, and thermal stability of TPNR nanocomposites were more pronounced when the SiO2 particles localized in ENR phase. By contrast, the presence of SiO2 particles in PP domain either near the interface or inside the PP phase affected the reduction in crystallinity of PP phase and showed a negative effect on mechanical properties due to the poor interface interaction between PP and SiO2 particles. POLYM. COMPOS., 33:1911–1920, 2012. © 2012 Society of Plastics Engineers 相似文献
10.
Enhancement of electrical conductivity and other related properties of epoxidized natural rubber/carbon nanotube composites by optimizing concentration of 3‐aminopropyltriethoxy silane
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Yeampon Nakaramontri Charoen Nakason Claudia Kummerlöwe Norbert Vennemann 《Polymer Engineering and Science》2017,57(4):381-391
Carbon nanotube (CNT)‐filled epoxidized natural rubber (ENR) composites were prepared by mixing in an internal mixer and thereafter on a two‐roll mill. Silane coupling agent, namely 3‐aminopropyltriethoxy silane (APTES), was directly incorporated in the ENR‐CNT composites during mixing of rubber and CNTs in the mixer, to perform in situ functionalization. It was found that pre‐crosslinking of ENR and APTES occurred especially at high APTES concentrations, such as 0.06 mL/(g of CNTs) and caused strong CNT agglomeration in the ENR matrix. However, the pre‐crosslinking could be reduced or avoided by decreasing the APTES concentration. In the concentration range 0.01–0.015 mL/(g of CNTs) of APTES, the APTES molecules were grafted on the CNT surfaces and generated new chemical linkages with the ENR. This improved the CNT dispersion in the ENR matrix and enhanced the composite properties. A very low approximately 0.5 phr of CNT threshold concentration for electric percolation was achieved in this type of composites. Also, three‐dimensional connected CNT networks were found to form in the ENR matrix at very low APTES levels. Thus, the electrical conductivity achieved in these composites reached the level required of conductive materials. POLYM. ENG. SCI., 57:381–391, 2017. © 2016 Society of Plastics Engineers 相似文献