摘要:

AbstractA major stream of post‐consumer plastics is a commingled blend of polyethylenes and polypropylenes, which usually exhibits lower performance compared with that of the homopolymers due to the incompatible nature of polyethylenes and polypropylenes. Various studies have been carried out to characterize the structure, morphology, mechanical, thermal, and rheological behavior of this blend. The effect of processing, modification, and compatibilization have also been studied by various workers. This article is a review of the work done on polyethylene–polypropylene blends to help in the understanding of this important blend. © 1994 John Wiley&Sons,

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130101

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe addition of various nucleating agents to a polymer leads to the modification of its crystalline structure, i.e., the formation of small spherulites with consequent changes in mechanical and optical properties. The aim of our research was to determine the role of nucleating agents on the crystallization of propylene copolymers. Random and block copolymers containing propylene and low amounts of ethylene were used in formulations with nucleating agents based on derivatives of sorbitol such as dibenzylidene sorbitol (DBS) and para‐methyldibenzylidene sorbitol (MDBS). The introduction of low concentrations of DBS and MDBS leads to significant changes in the crystalline structure with respect to α and β phases, as well as in the kinetics of crystallization. Using WAXS, DSC, optical microscopy, and tensile testing, the following changes of nucleated propylene copolymers were observed: (a) an increase in the crystallization temperature; (b) an increase of the level of crystallinity; (c) a considerable decrease of the size of spherulites (i.e., an improvement of the transparency of the random copolymers); (d) a decrease of the amount of the β phase in block copolymers; (e) an increase in tensile strength at yield; and (f) an increase in secant modulus. In most cases we found that the most efficient nucleating agent was the MDBS. © 1994 John Wiley&Sons

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130102

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

年代:1994

数据来源: WILEY

摘要:

AbstractMixtures of phenoxy, (a polyhydroxyether of bisphenol A) with respectively ethylene–propylene copolymer containing grafted anhydride groups along the chains (EP‐g‐MA), terpolymers of ethylene, t‐butyl acrylate and acrylic acid (EAA), and the sodium ionomer of a terpolymer of ethylene alkyl acrylate and methacrylic acid (I), were produced on a 25 cc torque rheometer. Small amounts of different organic sodium compounds, exhibiting varying levels of base strength, were also used to catalyze the reaction between the functional groups of the two polymers in the mixture. It was found that whereas EP‐g‐MA reacted with phenoxy to produce both graft copolymers and cross‐linked products in varying amounts, the terpolymers containing carboxylic acid groups in the backbone of the polymer chains would never give rise to the formation of cross‐linked products even when large amount of a strong base, such as sodium ethoxide, was used to catalyze the reactions. The latter mixtures exhibited the characteristics of ionomers, involving also alkoxide anions from the phenoxy component to an extent which depended on the base strength of the sodium compound used. The ionomeric mixtures displayed morphological features varying from finely dispersed particles to cocontinuous phases. © 1994 John

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130103

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe flow behavior of polycarbonate (PC) blended with three kinds of polyolefins (LDPE, HDPE, PP) was studied at 260°C using an Instron Capillary Rheometer. Flow behavior of the blends was found to be very different from that of the individual components, and significant viscosity reductions were observed for blends consisting of 5% and 15% polyolefins. In particular, the viscosity of PC/HDPE was found to be much lower than that of the parent viscosity at a shear rate below 100 1/s. For pure components, a crossover of PC viscosity was observed at high shear rate for HDPE and PP. Interfacial slippage in the blends has been suggested as the flow mechanism by which a substantial reduction in the melt viscosities of either component takes place upon the addition of a small amount of the other. A new method was proposed to evaluate the relationship between the characteristic slip factor of the blend and the viscosity of the mixture. A single master curve was obtained, i.e., σm/αAB=a·p±b, where σmis the shear stress at the matrix, αABthe slip factor,pthe viscosity ratio, anda, bthe constants. © 1994 John Wiley&So

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130104

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn this short review, some important phenomena often observed in blends of thermotropic liquid crystalline and thermoplastic polymers are described. Their outstanding physical properties will probably lead to applications as in situ composites. LCP of low concentration in the thermoplastic matrix can be used as a processing agent. The relations between rheology, morphology, and mechanical properties of the blends are explained. Flexible elements in the LCP‐molecules can lead to partial miscibility and improved adhesion between the components. A review of recent literature is given. © 1994 John Wiley&Sons, I

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130105

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe influence of a cross‐linking agent (divinyl benzene) on new polystyrene–polyethylene, IPN‐like networks was investigated by means of thermal, mechanical tests and a few microscopy observations. It was found that with increased concentration of cross‐linking agent, i.e., with PS cross‐linking density, Young's and storage moduli, measured in the molten rubbery state, increased linearly. Also the elongation and the stress at break were very sensitive to the content of cross‐linking agent, mainly in the low concentration region (0 to 2%). PE and PS domains of about 1 μm circular cross sections were observed on a smoothed surface of a PE/PS blend. Smaller and uniformly dispersed domains were observed for all the IPN‐like systems. The crystallinity, measured by DSC and WAXS, and the IPN morphological features, appeared to be independent of the styrene cross‐linking content, viz., the content of DVB. The overall behavior seemed to resemble that of classical simultaneous IPNs. © 1994 Joh

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130106

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe compatibilizing effect of styrene–sodium methacrylate (S‐NaMA) ionomer on nylon‐6 (N6) and polystyrene (PS) blends was studied. The dispersed particle size of these blends containing the ionomers was significantly reduced compared with that of the blends without the ionomer. The reduction of the particle size was more pronounced when the ionomer with lower ionic content was added to the blend. The blends using ionomer with the lower ionic content showed higher tensile strength than the blends using ionomer with the higher ionic content. It is suggested that these results are caused by the proper combination of specific interactions and structural similarity between the component polymers and the ionomers. © 1994 John Wiley&Son

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130107

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

年代:1994

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130108

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

年代:1994

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130109

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

年代:1994

数据来源: WILEY