摘要:

DSC investigations are reported for a broad assortment of blends and copolymers of the immiscible poly(ethylene oxide) (PEO)/poly(tert-butyl) methacrylate) (PTBMA) system. Contrary to expectations, the PEO crystallization and melting behavior of the copolymer system is similar to that of the PEO/poly(methyl methacrylate) (PMMA) copolymer system (which is usually considered to be miscible in the melt). This is discussed with the concept of a UCST-type granulated demixing in the latter. In both systems the crystallization is rather sensitive to the block structure, even for comparable molecular weights and compositions. This indicates some importance of DSC as an additional tool in copolymer characterization. Free PEO ends favor the crystallization in all cases.

ISSN:0360-2559    

DOI:10.1080/03602559008049832

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The effect of different physical treatments-for example, grinding, beating, and swelling with ethylene diamine-on the reactivity of bleached cotton stalk pulp toward grafting with methylmethacrylate monomer using ceric ion redox system is studied. the effect of monomer concentration and liquor ratio of grafting system on the graftability is also demonstrated. the graftability of treated samples is improved by using a liquor ratio of 50:1 instead of 40:1 for the untreated sample. Optimum graft yield for the beaten samples is obtained at 37°SR. Increasing the °SR of the beaten samples decreases the graft yield till it reaches a value lower than that of the untreated sample at 61°SR. Swelling of cotton stalk pulp with ethylene diamine has a high effect on the reactivity toward grafting. the physically treated pulps are characterized by infrared spectra to clarify the effect of these treatments on the crystallinity index (Cr I) of cotton stalk pulp.

ISSN:0360-2559    

DOI:10.1080/03602559008049833

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A discussion is presented of the mechanism of chain initiation and propagation stages in the cationic polymerization of olefins based on the example of catalytic systems of the type “aluminum chlorides-weak proton donor” (water, alcohols).

ISSN:0360-2559    

DOI:10.1080/03602559008049834

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Polymer additives are primarily responsible for the ultimate properties and performance of commodity polymers which are being used increasingly in demanding applications. the physical loss of additives from the polymer substrate is a major limitation to the traditional method of incorporating additives into polymers. the relatively low degree of permanence of additives is undermined further during in-service performance of polymers under aggressive environments. Loss and migration of additives is, therefore, a major concern to the manufacturing industry because of adverse effects on polymer performance and durability as well as the inherent lexicological consequences of migrating additives, especially in medical and food applications. This paper explores the use of reactive processing to achieve the desired degree of permanence and substantivity of polymer additives. This method has been exploited to chemically bind additives to the polymer backbone. By comparison with conventional procedures, reactively processed polymers are superior.

ISSN:0360-2559    

DOI:10.1080/03602559008049835

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Various parameters concerning the performance of isocyanate as a coupling agent have been discovered. Greater premixing time (e.g., 20 min) leads to an improvement in the mechanical properties of the composites. the isocyanate solution is more efficient in comparison with undiluted isocyanate. Moreover, the chemical structure of isocyanate, which provides a better interaction with thermoplastics, results in superior properties. the reactivity of different isocyanates decreases in the following order: PMPPIC, TDIC, HMDIC, EIC. Again, isocyanate can act as a promoter or as an inhibitor, depending on the concentration of isocyanate used. For example, with a moderate concentration, it promotes maximum mechanical properties, while with a higher concentration, mechanical properties deteriorate. In addition, the nature of the pulp (e.g., CTMP, cotton, or sawdust) and fiber loading percentage as well as different grades of polymer supplied by different companies also play an important role in the mechanical properties of thermoplastic composities.

ISSN:0360-2559    

DOI:10.1080/03602559008049836

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The mechanical properties and dimensional stability of composites of polystyrene filled with sawdust of hardwood aspen and softwood spruce have been investigated under various extreme conditions, for example, exposure to water at room temperature for 14 days and at boiling temperature for 24 h, as well as heat exposure at ± 105°C for 5 days and at -20°C for 2 h. Mechanical properties improve due to the treatment of the composites with a coupling agent [e.g., 3% poly [methylene(polyphenyl isocyanate)] (PMPPIC)], or by using coated (10% polymer ± 8% PMPPIC) or grafted (styrene) fibers. the treated composites or treated fiber-filled composites also showed more dimensional stability compared to nontreated composites. In addition, mechanical properties improve due to the treatment of the composites under different extreme conditions compared to normal ones. From the experimental results, it is suggested that different compounding methods of preparation of composites play an important role in improving the mechanical properties of the wood fiber-filled thermoplastic composites, even under extreme conditions.

ISSN:0360-2559    

DOI:10.1080/03602559008049837

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The infrared spectra of grafted bleached cotton stalks pulp are recorded in the region of 250–4000 cm−1. A new absorption band appearing at 1755 cm−1is assigned as a carbonyl stretching vibration produced from the graft copolymerization of methylmethacrylate monomer onto cotton stalk pulp. the effect of grafting on the frequency and intensity of OH and carbonyl bands give information about the reaction mechanism of the grafting process.

ISSN:0360-2559    

DOI:10.1080/03602559008049838

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An international symposium on degradation and stabilization of polymers was convened by the All-Union Center on the Problems of Polymer Aging and Stabilization* set up at the Institute of Chemical Physics, Academy of Sciences of the USSR. The symposium was held October 10-13, 1988, in Moscow, USSR.

ISSN:0360-2559    

DOI:10.1080/03602559008049839

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0360-2559    

DOI:10.1080/03602559008049831

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor