Thermoplastic interpenetrating polymer networks (IPNs) were prepared by combining poly(n-butyl acrylate) with polystyrene, both polymers crosslinked independently with acrylic acid anhydride (AAA). Decrosslinking of both polymers was carried out by hydrolysis of the anhydride bonds. Neutralization of the carboxylic acid groups to form the ionomer was carried out in a Brabender Plasticorder. Two subclasses of thermoplastic IPNs were studied: (1) Chemically blended thermoplastic IPNs (CBT IPNs) were prepared by synthesizing polymer II in polymer I in a sequential synthesis; (2) mechanically blended thermoplastic IPNs (MBT IPNs) were prepared by melt blending separately synthesized polymers. Rheovibron characterization revealed that of the two combinations, the CBT IPNs were better mixed than the MBT IPNs. Investigations of phase continuity via melt viscosity and modulus suggest that the CBT IPNs have some degree of dual phase continuity. Transmission electron microscopy suggests dual phase continuity and relatively small phase domains, 2000–5000 Å for the CBT IPNs. The mechanical properties from tensile and Izod impact tests showed that the CBT IPNs were stronger than the MBT IPNs. 相似文献
The use of functional azo initiators and the thermal history of the materials have been shown to exert significant effects on the properties of interpenetrating polymer networks (IPNs). The IPNs prepared with a reactive azo initiator from MDI and 1,2-PBD (1,2-polybutadiene diol) with PMMA have been found to exhibit greater ductility, lower rigidity, and lower moduli than IPNs prepared with AIBN. This probably resulted from the attached PMMA blocks modifying the properties of the PU matrix phases. Increasing thermal treatment of IPNs prepared from either the reactive or the normal azo initiators exhibited increased Tg values in both DSC and DMTA scans. These results have been explained by increased association from chemical reactions between the hard segments of the polyurethane and poly(methyl methacrylate) ester groups. 相似文献
The thermoplastic interpenetrating polymer networks (IPNs) are combinations of two physically crosslinked polymers. Thermoplastic IPNs were prepared by combining polymer I, an SEBS triblock elastomer with polymer II, an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume). Neutralization of the acid groups to form the ionomer was carried out on a Brabender Plasticorder. Two subclasses of the thermoplastic IPNs were identified. Chemically blended systems, prepared by a sequential polymerization method, were compared with compositionally equivalent mechanically blended systems prepared by melt blending the separately synthesized polymers. The chemically blended thermoplastic IPNs (CBT IPNs) exhibited lower melt viscosities than compositionally equivalent mechanically blended thermoplastic IPNs (MBT IPNs). Moreover, the melt viscosities of many of the CBT IPNs were even lower than that of either homopolymer component, leading to an explanation in terms of an unusually low value of the rubbery modulus front factor. Although both types of thermoplastic IPNs underwent a phase inversion during neutralization of polymer II, the phase inversions were often incomplete. Morphological studies revealed that more equal dual phase continuity existed in the MBT IPNs than in the CBT IPNs after ionomer formation. 相似文献
The process of crosslinking sodium and n-butyllithium polybutadienes as well as the products of their modification obtained by epoxidation has been studied. It has been found that the crosslinking efficiency of epoxy-1,2-polybutadiene is half that of the starting polybutadiene. However, the crosslinking efficiency of epoxy-1,4-polybutadiene was found to be similar to that of the starting 1,4-polybutadiene. The shift in glass transition temperature for epoxy-polybutadienes brought about by the change in the chemical composition (ΔTg)M was found to be 67 K for 1,4-polybutadiene, and 51 K for 1,2-polybutadiene. The effect of the epoxy groups and crosslinks on the glass transition temperatures of modified crosslinked polymers is also discussed. 相似文献
Macrolattice structure in the ordered phase of a poly(styrene-b-butadiene-b-styrene) (SBS, with the bulk morphology of spherical polystyrene microdomains in the polybutadiene matrix) dissolved in a
selective solvent (dodecyl methacrylate, C12MA, or a 75/25 w/w mixture of C12MA and butylene diacrylate, BDA) which mixes preferentially with the polybutadiene matrix was examined by means of transmission
electron microscopy. The use of C12MA/BDA mixture as the selective solvent provided the opportunity of freezing the macrolattice structure upon UV-initiated
polymerization of the acrylic monomers when the SBS content is above ca. 60 wt%. Results indicated clearly a body-centered
cubic structure, in contrast to the simple cubic packing previously proposed. 相似文献
In this paper we report the variation of the etch rate of polymers in the afterglow of a radio frequency discharge in oxygen as a function of total flow rate in the range 2–10 cm3 (STP)/min. The measurements were made at ambient temperature with the O(3P) concentration held essentially constant. We report results on three polymers: cis-polybutadiene, a polybutadiene with 33% 1,2 double bonds, and a polybutadiene with 40% 1,2 double bonds. We have observed that the etch rate of these polymers decreases significantly with increasing flow rate, strongly suggesting that the vapor-phase products of polymer degradation contribute to the degradation process. 相似文献
Plastic foams with nano/micro‐scale cellular structures were prepared from poly(propylene)/thermoplastic polystyrene elastomer (PP/TPS) systems, specifically the copolymer blends PP/hydrogenated polystyrene‐block‐polybutadiene‐block‐polystyrene rubber and PP/hydrogenated polystyrene‐block‐polyisoprene‐block‐polystyrene. These PP/TPS systems have the unique characteristic that the elastomer domain can be highly dispersed and oriented in the machine direction by changing the draw‐down ratio in the extrusion process. A temperature‐quench batch physical foaming method was used to foam these two systems with CO2. The cell size and location were highly controlled in the dispersed elastomer domains by exploiting the differences in CO2 solubility, diffusivity, and viscoelasticity between the elastomer domains and the PP matrix. The average cell diameter of the PP/TPS blend foams was controlled to be 200–400 nm on the finest level by manipulating the PP/rubber ratio, the draw‐down ratio of extrusion and the foaming temperature. Furthermore, the cellular structure could be highly oriented in one direction by using the highly‐oriented elastomer domains in the polymer blend morphology as a template for foaming.
Composites based on polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS triblock thermoplastic elastomer) and magnesium hydroxide (Mg(OH)2) (5–60 wt.‐%) have been prepared by twin screw extrusion. Interfacial modifiers included dispersants, i.e., isostearic acid, oleic acid, stearic acid; and coupling agents, i.e., maleanised polybutadiene and vinyltriethoxysilane. In each case, approximately one monolayer of treatment was used. A dual bore motor driven extrusion rheometer was used for assessment shear and elongation flow behavior (Cogswell's method) over a shear rate range of 100 s?1 to 5 000 s?1. Untreated filler and filler treated with coupling agents gave composites that become increasingly pseudoplastic as filler level increased. Fatty acid structure was shown to have some influence over the level of melt viscosity reduction normally associated with such treatments; stearic acid gave the most pronounced reduction in melt viscosity possibly due to the tightly packed monolayer. Elongational flow properties, determined using Cogswell's method, indicated significant chain extension/branching of the bulk matrix when high levels of untreated filler were present and long range filler‐matrix interaction in composites modified with maleanised polybutadiene.
Elongational viscosity versus extensional stress (obtained by Cogswell's method) for SBS blended with filler surface treatments (□) unfilled matrix, and unfilled matrix plus (?) Hist and (?) MPBD. 相似文献