摘要:

AbstractThe values of Mark–Houwink–Sakurada constants were determined for poly(α‐methyl styrene) (PαMs) of high and low molecular weights in a variety of solvents by a new approach, which requires only polydisperse samples. The results are in accord with those reported in the literature. In addition, the present work reports the values of the Flory interaction parameter for PαMs in 13 solvents of distinct solvent power at various temperatures. Three refined methods pertaining to both polar and nonpolar solvents were applied to estimate the solubility parameter (δ2) of PαMs resulting in δ2= 18.75 ± 0.15 (J/mL)1/2at 30°C. Finally, the scatter data of the Huggins coefficient over a range of expansion factors varying from 0.7 to 2.6 seem to conform better to a newly proposed empirical equation than to the contemporary model after Imai. © 1993 John W

ISSN:0021-8995    

DOI:10.1002/app.1993.070500701

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this study, the grafting of methyl methacrylate onto poly(ethylene terephthalate) fibers using azobisisobutyronitrile is reported. An increase in temperature and monomer concentration were found to increase the graft yield. The graft yield increased up to an initiator concentration of 0.90 × 10−2mol/L and decreased at higher initiator concentrations. The fiber densities decreased, and fiber diameters and intrinsic viscosities increased with increasing graft yield. Moisture regain values showed a slight increase with the grafting. Fiber orientation decreased the graft yield to an important extent. The overall activation energy for grafting was calculated to be 11.9 kcal/mol. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070500702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe optical effects (fluorescence, anisotropy, and absorption) of kraft lignin solutions in three different kinds of solvents (0.1NNaOH, DMF, and pyridine) on the measurement of the weight‐averaged molecular weight of lignin were investigated, and a correction procedure for these optical effects in the determination of the weight‐averaged molecular weight of kraft lignin was developed. It was found that the fluorescence effect is the main source of error in the determination of the molecular weight of lignin, and the anisotropy and absorption strongly affect the second virial coefficient. It was also found that the anisotropic effect of kraft lignin dissolved in DMF and pyridine is contributed mainly by the anisotropic solvents rather than by the lignin particles and that the lignin solution in 0.1NNaOH is essentially optically isotropic. By using the correction procedure provided, the corrected molecular weight of lignin determined in three kinds of solvents varies only about ±10%, whereas the apparent weight‐averaged molecular weight of the same lignin differs by ±57%. © 1993 John Wiley&S

ISSN:0021-8995    

DOI:10.1002/app.1993.070500703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractPlasma‐induced graft copolymerization of acrylic acid, which was incorporated onto polyethylene (PE) film, was prepared. A bisamino poly(ethylene oxide) (PEO) was immobilized onto the poly(acrylic acid) (PAAc)‐grafted PE membrane to modify the surface properties. The samples were characterized by ESCA. A respective chemical shift of Ar plasma‐treated and control polymeric film was revealed by ESCA. The presence of the grafted PAAc and PEO was also verified. Glucose oxidase (GOD) was immobilized onto this novel grafted polymeric film with and without PEO being used as a spacer. The Michaelis constant,Km, and the maximum reaction velocity,Vmax, were estimated for the free and the immobilized GOD. GOD immobilized onto the polymeric films with and without a spacer obeyed Michaelis kinetics. The Michaelis constant,Km, was larger for the immobilized GOD than for the free one whereasVmaxwas smaller for the immobilized GOD. The bioactivity of PEO‐modified PAAc‐grafted PE membrane (PAAc–PEO–GOD) was higher than that of PAAc‐grafted PE membrane (PAAc–GOD). The pH and thermal stabilities of the immobilized GOD without a spacer (PAAc–GOD) were higher than those of the immobilized GOD with a spacer (PAAc–PEO–GOD) and the free form. © 1

ISSN:0021-8995    

DOI:10.1002/app.1993.070500704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe structure of oriented transfer films of poly(tetrafluoroethylene) (PTFE), previously used as orientation‐inducing layers for a variety of materials, was studied. Transmission electron microscopy and X‐ray diffractometry were empolyed to determine the continuity and relative volume of the PTFE films, which were deposited onto glass substrates by friction transfer at controlled temperatures, pressures, and sliding rates. The thickness and continuity of the films were found to increase with increasing temperature and applied pressure. In the range of sliding rates used (0.1–10 mm/s), no significant correlation between this processing variable and the thickness or continuity was apparent. Transmission electron microscope investigations showed that, generally, the (100) plane of the PTFE crystalline unit cell was parallel to the glass surface. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070500705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractFlexural behavior of particle‐filled fiber‐reinforced polyester composite was investigated by varying the polymer and fiber contents. The polymer content was varied between 10% and 18% of the total weight of the polyester composite (PC) and the glass fiber content was varied up to 6% (by weight of PC). The chopped glass fibers were 13 mm long. The fine aggregates were well graded, with particle size varying from 0.1 to 5 mm, and were mainly composed of quartz. The fine aggregates and glass fibers were also pretreated with a coupling agent (γ‐methacryloxypropyltrimethoxysilane, γ‐MPS) to improve the mechanical and fracture properties of the polyester composites. In general, the addition of fibers increased the flexural strength, toughness, fracture properties, and failure strain (strain at peak stress), but the flexural modulus of polyester composites remained almost unchanged. The addition of 6% fiber content and silane treatment increased flexural strength of 18% PC by 95% to 41.6 MPa (6,040 psi). Crack resistance curves, based on the stress intensity factor (KR‐curve), have been developed for the fiber‐reinforced PC systems. A two‐parameter relationship was used to predict the complete flexural stress‐strain data. There is good agreement between the predicted and measured stress‐strain relationships. © 1993

ISSN:0021-8995    

DOI:10.1002/app.1993.070500706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe presence of wall slip during the flow of polymeric melts has significant ramifications on the melts' processability. In this study, the effects of materials of construction and surface roughness on the wall slip behavior of a linear low density polyethylene were investigated, using capillary flow. Capillaries, constructed from copper, stainless steel, aluminum, and glass, were used. The inner surface roughness of the capillaries were characterized by the employment of a profilometer and scanning electron microscopy. The roughness profiles of copper capillaries were also altered by the employment of chemical etching. Using Mooney's analysis, the wall slip velocity values were determined to be in the range of 0.09 to 1.34 mm/s. The wall slip velocity values were the highest for stainless steel and were negligible for aluminum. The relative work of adhesion values of polyethylene were the smallest for stainless steel and copper and the highest for glass. Overall, the wall slip velocity values increased with decreasing surface roughness of the capillaries and with decreasing work of adhesion. © 1993 John Wiley&Sons, Inc

ISSN:0021-8995    

DOI:10.1002/app.1993.070500707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractMechanical and Morphological properties of polyamide‐6/ABS blend systems, compatibilized by styrene‐maleic anhydride (SMA) copolymer, have been studied. The strength, modulus, and impact properties improved upon the addition of SMA. Morphological studies, using small angle light scattering, polarizing microscopy, and scanning electron microscopy, showed that SMA acts as a compatibilizer for the above system. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070500708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe amount of research on lignocellulosic/thermoplastic composites has increased dramatically. Little attention, however, has been directed towards the subject of crystallinity at the interface (interphase). Optical microscopy and differential scanning calorimetry were used in this work to study crystallinity in the cellulose/polypropylene system. The results verify that cellulose acts as a nucleating agent for polypropylene, producing a transcrystalline region around the fiber. Treatment of the fibers with alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), or stearic acid, inactivates the surface features responsible for transcrystallinity. These treatments also affect the overall degree of crystallinity of the sample. Morphological features, resulting from a transcrystalline or nontranscrystalline interphase, may have a significant effect on mechanical properties. A possible mechanism for the appearance of transcrystallinity involving crystal structure matching is also proposed. © 1993 John Wiley&Sons, Inc

ISSN:0021-8995    

DOI:10.1002/app.1993.070500709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe chelating resins incorporating amide linkages were synthesized in open reaction vessels (OV) by polycondensing different proportions,viz., 1 : 1, 1 : 1.3, and 1.3 : 1 of polyethyleneimine (PEI) and diethylenetriaminepentaacetic acid (DTPA), respectively, at 145–155°C, and at varying curing times (15 h and 22 h). For the proportion 1 : 1, the synthesis was performed in a closed reaction vessel (CV) as well. The resins were characterized by FTIR, elemental, and thermogravimetric analysis, apart from sarptometric surface studies. The extent of crosslinking was evaluated by swelling measurements and the chemical stability was assessed by acid and alkali treatment. The effect of the mode of heating and curing times on the extent of crosslinking and pore structure modifications were evaluated. The influence of these factors on the capacities, the kinetics, and the break through curve trends of these resins were studied using zinc and cadmium metal ions as references. The reproducibility of the resins were ascertained by assessing the extent of change in the break through curve trends of their different batches, synthesized under identical conditions. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070500710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY