摘要:

Polymer science and technology is one of the most active and promising fields in science, embracing a multitude of topics from natural polymers such as cellulose, wool, silk, jute, etc., which are of utmost importance for living systems, to the synthetic high polymers. In recent years, the intensive activity in the field of polymer science, of course, has been a reflection of the materials' widespread application in industry and domestic life. Because of the tremendous increase in the price of petroleum and limited supply of coal, attention all over the world is focused on the utilization of natural resources for the synthesis of polymeric materials.

ISSN:0360-2559    

DOI:10.1080/03602558808081141

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A low thermal inertia mold (LTIM) is evaluated based on its ability to reduce residual stress and molecular orientation in thin polycarbonate parts. The mold employs a special cavity design which incorporates the use of high-temperature (above 350 °C) thermoelectric devices. Residual stresses are compared in LTIM and conventionally molded parts via an estimation of critical J-integral values (Jc)-the essential energy needed for crack initiation per unit area. The estimated values ofJcfor LTIM and conventional parts are 6.3 and 7.3 kJ/m2, respectively. This difference may be due to the elevated LTIM cavity temperature which alleviates residual stresses and in turn reduces the estimated value ofJc.Observations of birefringence distributions were used to compare molecular orientation. The amount of birefringence is greatly reduced in a large central region of the LTIM parts, indicating low levels of orientation. Conventional parts show distinct color fringes along the melt flow path, indicative of flow-induced orientation.

ISSN:0360-2559    

DOI:10.1080/03602558808081142

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The electrical conductivity of aromatic polymers has become a topic of intense interest in recent years. Benzenoid and heterocyclic aromatic polymers [1–14] and polymers with nonaromatic heteroatoms in the backbone [15–27] (such as ideal structures1–3, respectively) have been investigated. Not surprisingly, the electrical conductivities of different polymers are different. However, there also is much variation in the observed conductivities of individual samples of each polymer. Depending on the route of synthesis, extent of halogenation, identity and concentration of dopant, level of contaminants, and degree of crystallinity, observed conductivities can vary by as much as 6 orders of magnitude (e.g., Refs. 7, 13, 28, 29, and references therein). Clearly, analytical techniques that provide complete structural characterization of these polymers are needed in order to understand fully the structural properties that underlie their electrical conductivities.

ISSN:0360-2559    

DOI:10.1080/03602558808081143

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In injection molding, complete mold cavity filling is a design goal that has to be met 100% every time. Mold cavity filling is a complicated process which depends on many variables such as mold cavity surface temperature, injection pressure, injection speed, melt temperature, flow index of material being molded, etc. The aim of experimental investigation of the low thermal inertia molding (LTIM) [1] process is to demonstrate the feasibility of molding completely filled, thin parts at low injection pressure and injection speed without sacrificing part quality. The evaluation of the new molding concept consists of comparison of a conventionally molded thin rectangular part with an identical part molded by the LTIM process. The length of filling in the conventional cavity and in the LTIM cavity are compared at different injection pressures and injection speeds. The mold design, experimental procedure, and results of the molding are discussed in the following sections.

ISSN:0360-2559    

DOI:10.1080/03602558808081144

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Toughened unsaturated polyesters were prepared by chemical reaction, physical blending, and the block copolymerization method, respectively. Mechanical properties of thus-formed unsaturated polyesters after curing were compared. The superior performance of block copolymers was explained with a dynamic test and morphology study. Mechanical properties of their sheet-molding compounds were studied as well.

ISSN:0360-2559    

DOI:10.1080/03602558808081145

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Six years of production experience have proved high-strength SMC to be an excellent material for heavy-duty automotive parts. New fields for applications with difficult fiber structures will be opened up in the near future.

ISSN:0360-2559    

DOI:10.1080/03602558808081146

出版商:Taylor & Francis Group    

年代:1988

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:10.1080/03602558808081140

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor