摘要:

AbstractThe surface properties of cellulose fibers have been modified by heat treatment, by silane coupling agents, and by maleated polypropylene grafts. The effectiveness of these methods has been evaluated by electron spectroscopy (ESCA), by contact angle measurements, and by inverse gas chromatography. The latter analyses yielded information on the fibers' acid/base interaction potential. Cellulose was found to be amphoteric, with prevalent acidic properties. Heat and chloro‐silane treatments accentuated acidity, while amino‐silane treatment produced net basicity in the fiber surface. Modification with maleated polypropylene reduced specific interactions and converted the fiber to a predominantly dispersion‐force solid. The modified fibers were used in composites with polypropylene (neutral), polystyrene (base), and chlorinated polyethylene (acid) as matrix. Stress/strain and dynamic mechanical parameters were found to vary with acid/base interactions between polymer and fiber, significant improvements being noted in elastic and storage moduli, in tensile strength and elongation. In polypropylene, properties were unaffected by acid/base considerations. Acid/base forces, not necessarily dominant, merit consideration in the design of surface modification strategies intended to optimize composite mechanical prope

ISSN:0272-8397    

DOI:10.1002/pc.750140602

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractToughening of dicyanate matrix composites with particulate‐modified resin‐rich interlayers was investigated in this study. Specifically, the cure behavior, viscosity, and fracture toughness of the modified dicyanate systems were analyzed. Creation of a layered composite structure showed no improvement in Mode 1 interlaminar fracture toughness(GIc), but greatly increased the Mode II interlaminar fracture toughness(GIIc).Furthermore, the concentration of modifier particles in the interlayer resin was found to directly affect the toughness improvement and fracture p

ISSN:0272-8397    

DOI:10.1002/pc.750140603

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe viscosity of thermoplastics aboveTgwas found to greatly affect the room temperature electrical properties of conducting thermoplastic composites made by compression molding of a powder mixture, while the mechanical properties are essentially not affected. The electrical resistivity decreased and the electromagnetic interference shielding effectiveness increased with increasing viscosity, as shown by using (i) the same filler, namely nickel particles, in polyimidesiloxane and polyether sulfone, and (ii) the same filler and matrix at different composite molding temperatures. This effect is attributed to the flow of the low viscosity thermoplastic particles during composite fabrication tending to disturb the connectivity of the filler particles achieved prior to heating.

ISSN:0272-8397    

DOI:10.1002/pc.750140604

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper describes methods of evaluating polybutene electrofusion joints and results of mechanical strength measurements for an electrofusion joint. Suitable fusion conditions were determined qualitatively through measurement of fusion interface temperatures and observation of the fusion zone. A method of determining standard fusion conditions, based on the relation between heating time and tensile strength, is also indicated. Differences in thermal properties between polybutene and polyethylene resins are discussed. It was found that polybutene required less supplied power per unit fusion area for suitable fusion. It was also confirmed that an electrofusion joint required a cold zone.

ISSN:0272-8397    

DOI:10.1002/pc.750140605

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe modification of epoxy polymers with some metal cations, viz., Zn2+, Fe3+and Mn4+, has been studied. These cations were introduced into the epoxy matrices by hardening of diglycidyl ether of bisphenon‐A with the chelates of the metal salts with some aliphatic amines. Studies center on the dependence of the mechanical strength and heat resistance of the metal containing epoxy polymers with Zn2+and Fe3+increases the strength and heat resistance significantly. These metal‐containing hardeners have excellent processability and can be used to produce high strength and high thermal resistance thermos

ISSN:0272-8397    

DOI:10.1002/pc.750140606

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe crystallization kinetics of poly(etherether ketone) (PEEK) in chopped mesophase pitch‐derived carbon fiber/PEEK composites have been studied. Various processing techniques are used in order to obtain controlled fiber length in the composites. Scanning electron microscopy performed on properly etched long fiber composite samples reveals that the nucleating sites density is low at the carbon fiber surface: transcrystalline layers are rarely observed. This is confirmed by differential scanning calorimetry. However, samples processed by mixing carbon fibers and molten polymer in a high temperature mixer have a widely different behavior: the nucleation density and the crystallization rate increase, the glass transition of these samples is displaced towards higher temperatures, and the solubility is dramatically lowered. We ascribe these phenomena to the adsorption of the polymer chains on carbon particles created by attrition during the mixtin

ISSN:0272-8397    

DOI:10.1002/pc.750140607

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractDesign of molding tools and molding cycles for sheet molding compounds (SMC) is often expensive and time consuming. Computer simulation of the compression molding process is a desirable approach for reducing actual experimental runs. The focus of this work is to develop a computer model that can simulate the most important features of SMC compression molding, including material flow, heat transfer, and curing. A control volume/finite element approach was used to obtain the pressure and velocity fields and to compute the flow progression during compression mold filling. The energy equation and a kinetic model were solved simultaneously for the temperature and conversion profiles differential scanning calorimetry (DSC) was used to experimentally measure the polymer zation kinetics. A rheometrics dynamic analyzer (RDA) was used to measure the rheological changes of the compound. A series of molding experiments was conducted to record the flow front location and material temperature. The results were compared to simulated flow front and temperature profiles.

ISSN:0272-8397    

DOI:10.1002/pc.750140608

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe objective of this work was to develop optically transparent glass fiber reinforced poly(methyl methacrylate) (PMMA) composites by matching the refractive index of the glass fiber reinforcement to that of the PMM, A matrix, thereby minimizing the quantity of light which is normally scattered and reflected at the interface of dissimilar materials. A pressure curing process is described for preparing composites 10 by 15 by 0.6 cm thick and containing up to ∼ 35% glass fiber. By curing at 65°C under 6.9 MPa N2for 18 H, composites have been produced with optical quality surfaces and flexural strengths more than seven times that of commercial PMMA of the same thickness. A transparent composite containing 10.4 vol% of 13 μm diameter fiber had an 84% optical transmission (92% maximum for PMMA) at 600 nm and 2

ISSN:0272-8397    

DOI:10.1002/pc.750140609

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractPolyimide (PMR‐15)/fiber composites are important structural components in many high temperature applications requiring high performance lightweight materials. Most composites are fabricated from “prepregs,” but resin transfer molding (RTM) is an alternative route to the formation of a resin‐saturated perform, further processing of which yields the final part. A simple model is proposed for the RTM of “thin” composite parts. Numerical solution of the model is accomplished through integration of the equation s formulated using he finite element method. This approach accounts for the changing shape of the flow front during RTM. The resulting computational schemes are numerically stable an

ISSN:0272-8397    

DOI:10.1002/pc.750140610

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractFinite element simulations on permeability variations of an aligned fiber assembly have been conducted. Two dimensional viscous flow in longitudinal and transverse directions has been studied respectively, using the steady state Navier‐Stokes equation but with small Reynolds numbers. Two groups of packing structures are investigated, both with introduced disturbances in the fiber assembly. One is the idealized packings, including hexagonal and square packings, but with selected fibers removed randomly, and with fiber center positions disturbed randomly. This gives random effect within the modeled cells, but on the macro‐scale the structure is still periodic. Numerical simulations are performed using available finite element packages. The result shows clearly that different physical mechanisms doninate the flow process in longitudinal and transverse permeabilities in the longitudinal flow case, the disturbance introduces openings within the bundle, and these openings become between fibers. Thus flow resistance increases substantially in the idealized packing cases. Numerical data are then compared with available data from other studies, particularly that from using self‐consistent me

ISSN:0272-8397    

DOI:10.1002/pc.750140611

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY