摘要:

AbstractThe kinetics of the activated anionic polymerization of caprolactam to nylon‐6 and its copolymers has been studied. Nylon‐6 block copolymer and nylon‐6 were prepared at various initial reaction temperatures (140°C to 165°C) by anionic polymerization in an adiabatic dewar flask. Different concentrations of poly(ethylene oxide) (PEO) in 4,4′‐diphenyl methane diisocyanate (MDI)‐capped PEO and 1 mole percent MDI, in a caprolactam solution, were used as the activators with the catalyst, the sodium salt of caprolactam. The kinetics of the reaction were analyzed from an adiabatic temperature rise. A new method was applied to determine the rate parameters. The activation energy,Ea, of nylon‐6 and nylon‐6 block copolymers were found to be 22 kcal/mole. The collision frequency factor,Ao, steadily decreased and the autocatalytic constant,Bo, decreased to a constant value of 16 with the introduction of PEO. However, it was found that the order of reaction,n, was almost a constant value at the second order fo

ISSN:0032-3888    

DOI:10.1002/pen.760281802

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractEffects of absorbed moisture on degradation behavior of high nitrile barrier polymers were monitored using thermogravimetric analysis techniques. Non‐modified and 10 percent rubber modified samples were heated isothermally at nitrile processing temperatures (200°C to 240°C) in air and nitrogen environments. Degradation was evaluated in terms of weight loss as a function of heating time and sample coloration. It was determined that complete removal of moisture, as well as high moisture concentration, contribute to increased degradation at the temperatures evaluated. Moisture levels in the range of 0.15 to 0.5 percent were found to minimize degradation. Heating environment, time, temperature, and rubber modification were also found to influence thermal stabil

ISSN:0032-3888    

DOI:10.1002/pen.760281803

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractPolyolefins are used in many rigid plastic packages that are developed for food applications. Generally, the polyolefins used are selected for a balance of cost, ease of molding, and performance properties in a finished package. In this paper some of the physical and sorption properties of polyolefins that are critical to rigid plastic packages are discussed. Initially, a brief review of the performance requirements of plastic food packages will be presented. This is followed by discussions of specific properties of polyolefins such as impact resistance, adhesion and thermal resistance, and how they may be enhanced by coextrusion. Additionally, the sorption of food components such as flavors into polyolefin walls of packages is discussed. Here, the applicable theoretical considerations for sorption and their value for analyzing experimental data are presented. Finally, specific sorption properties of d‐limonene in ethylene‐propylene copolymers and their effects on package performance and design are reported and discus

ISSN:0032-3888    

DOI:10.1002/pen.760281804

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe three essential factors of the Juska–Harrison stress activated phase transition (SAPT) deformation model are analyzed. Based on the concept of “mechanical melting”, a formula for the theoretical melting stress is derived from thermodynamics. A comparison of experimental and calculated results for a number of polymers shows that the strain energy is high enough to induce isothermal “mechanical melting” during extension, and the observed yield stress has the same order of magnitude as the theoretical melti

ISSN:0032-3888    

DOI:10.1002/pen.760281805

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractHigh density polyethylene has been chlorinated by three different methods: in suspension and in solutions of two different solvents. Carbon‐13 NMR and infrared analysis show that chlorination in chlorobenzene solution leads to statistically random distribution while chlorination in suspension gives highly blocky substitution. An intermediate distribution was obtained by chlorination in tetrachloroethane solutio

ISSN:0032-3888    

DOI:10.1002/pen.760281806

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractChlorination of high density; polyethylene results in polymers which consist of unmodified methylene units and chlorinated methylene co‐units. The effect of the concentration and distribution of chlorinated units on the solid state structure has been examined by thermal, wide angle X‐ray diffraction and dynamic mechanical analysis. As the substitution becomes more random, the crystallinity, crystallite size, and crystalline perfection decrease for a given chlorine content. The chlorinated units are shown to be capable of co‐crystallizing, and the concentration of chlorine in the crystalline phase increases as the distribution is made more random. Concurrently, the chlorine concentration of the amorphous phase decreases. Segregation of chlorine into the amorphous regions is most efficient when the substitution is b

ISSN:0032-3888    

DOI:10.1002/pen.760281807

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractFracture behavior of epoxy mortar was investigated in Mode I fracture using single edge notched beams with varying notch depth and beam thickness. The beams were loaded in both 3‐point and 4‐point bending. Influence of polymer content and temperature on the fracture behavior of epoxy mortar was studied using uniform Ottawa 20–30 sand. The polymer content was varied between 10 percent and 18 percent of the total weight of the composite. The temperature was varied between 22°C and 120°C. The flexural strength of the polymer mortar increases with increase in polymer content while the flexural modulus goes through a maximum. The critical stress intensity factor (KIC) was determined by several methods including compliance method (based on crack mouth opening displacement) and finite element analysis. TheKICfor epoxy mortar increases with increase in polymer content and epoxy mortar strength but decreases with increase in temperature. The critical stress intensity factor of epoxy mortar is represented in terms of polymer content and polymer strength or stiffness. Numerical tests based on random sampling and stratified sampling procedures were performed to substantiate the experimentally observed fracture toughness values of epoxy

ISSN:0032-3888    

DOI:10.1002/pen.760281808

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractWe have reexamined the parallel Avrami model recently proposed by Velisaris and Seferis (1) to describe the non‐Isothermal crystallization of poly(etheretherketone), PEEK. We show that, based on considerations of morphology development, the crystallization process with the larger Avrami exponent has the higher melting point, whereas the process with the smaller Avrami exponent has the lower melting point. This assignment differs from that of Velisaris and Seferis. In addition, we have used the infinite crystal melting point, as required by crystallization theory, to determine the Avrami rate parameters for the two processes. With this revision of the parallel Avrami model, we have applied the model to non‐isothermal crystallization of APC‐2 PEEK composite. Under the assumption that the linear growth rate determines the Avrami rate parameter, both the transport activation energy,U, and the kinetic parameter,Kg, are found to compare favorably with the values previously determined from isothermal crystallization of neat resin

ISSN:0032-3888    

DOI:10.1002/pen.760281809

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe energy stored in polystyrene after plastic deformation is measured by the differential scanning calorimetry (DSC) technique. Similar to metals, the stored energy increases with plastic straining, first rapidly, and then more slowly, and finally the stored energy seems to approach a saturation value (about 1 cal/gram). By comparing to the plastic work done, the fraction stored ranges from 30 percent after 10 percent compression to 10 percent after 60 percent compression. The fraction is about twice as large as that of copper. The release of stored energy has two distinct parts, one belowTgand the other aboveTg. Most of the strain recovery seems to accompany the second part. By using the Kissinger plot, the second part has an activation energy, of 142 kcal/mole which is about 10 percent larger than that of compressive strain recovery.

ISSN:0032-3888    

DOI:10.1002/pen.760281810

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThermal treatment of amorphous poly(aryl‐ether‐ether ketone) below the glass transition temperature has been studied. The extent of aging was measured by differential scanning calorimetry. X‐ray and Fourier transform infrared spectra were used to study both melt‐cast and annealed samples. The effect of the thermal treatment of viscoelastic response was evaluated using creep tests. Aging has been shown to be accompanied by a marked change in the transport properties of the m

ISSN:0032-3888    

DOI:10.1002/pen.760281811

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY