摘要:

AbstractWood cellulose, a versatile and renewable natural resource, has potential for use as a reinforcement for synthetic organic polymers. During the past 80 years a number of materials using the reinforcing properties of wood cellulose have found major markets. Forms of wood cellulose proposed as reinforcements include: wood fibers, cellulose fibers, microfibillar, and microcrystalline cellulose. Recent attention has been given to them as fillers/reinforcements in thermoplastics and elastomers. Most cellulosic composites derive their existence from their comparatively low materials cost and the filling rather than reinforcing properties of cellulose. However, cellulose chains have a potential stiffness much higher than glass and in the same range as superstiff aramid fibers. This paper examines the state of the art of combining wood cellulose with synthetic organic polymers to from composites and considers new ways for better using cellulose's reinforcing potential.

ISSN:0272-8397    

DOI:10.1002/pc.750100202

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractAn experimental study on the flow behavior of glass fiber reinforced Noryl (a commercial poly(phenyleneoxide)/polystyrene blend) using a capillary rheometer is described. The effect of fiber concentration on shear viscosity and die swell was studied at various temperatures. Breakage of glass fibers during flow through the rheometer is discussed; it was found that the average fiber length (about 230 μm) was not significiantly altered, except at the highest shear rate (575 s−1) studied. The incorporation of short fibers into thermoplastic polymer melts increases their viscosity without changing the basic rheological character‐shear rate dependency. No discernible viscosity changes were measured by incorporating 10 weight percent fibers, and upon further increase of fiber concentration from 20 to 30 weight percent no appreciable increase in viscosity was noted. It is shown that short glass fibers cause a large reduction in extrudate swell. The presence of voids and fiber orientation contribute to the decrease of the die swell, an effect greater than expected from volumetric considerations a

ISSN:0272-8397    

DOI:10.1002/pc.750100203

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractMechanical properties of short fiber reinforced thermoplastics depend on the fiber orientation distribution produced during the melt flow processing step. An experimental investigation of fiber orientation during shear flow through a circular die is presented. A quantitative determination of the glass fiber orientation distribution was done by analyzing photomicrographs of polished extrudate sections. Planar and axial fiber orientation distributions as affected by shear rate and total shear are discussed. The reliability of a classical metallographic technique for fiber orientation determination was evaluated. Orientation effects are expressed by a single orientation parameter which is used to account for the average fiber orientation contribution to the relative viscosity. The influence of shear rate, total shear, fiber concentration, and temperature on fiber orientation has been investigated. It is concluded that an orientation parameter should be used to account for fiber concentration effects on the relative viscosity. Calculated values, considering the orientation parameter, show good agreement with the experimental relative viscosity results.

ISSN:0272-8397    

DOI:10.1002/pc.750100204

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractStudies on the high temperature sorption of caprolactam by polymer resins and their composites have been conducted. The systems investigated were glass fiber reinforced (GFR) poly(phenylene sulfide) (PPS), polyetheretherketone (PEEK) neat resin, GFR PEEK and carbon fiber reinforced (CFR) PEEK. To measure changes of caprolactam sorption, melting behavior, mechanical properties, and fracture surface morphology were determined. Absorption of caprolactam by the PEEK composites was 30 to 40 percent less than by the neat resin. This is attributed to the fibers, which acted to constrain the matrix and thus limit its swellability. Reductions in melt temperature, percent crystallinity, ultimate tensile strength, and modulus were observed following exposure to the chemical environment. The loss of strength and stiffness was a consequence of the degradation of the matrix/fiber interface by the sorbed caprolactam.

ISSN:0272-8397    

DOI:10.1002/pc.750100205

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractFor short fiber reinforced thermoplastics the effect of fiber length and the fiber/matrix bond on the ultimate properties of the material are well understood. But, how the process conditions under which the composite is made affect the fiber length and the fiber matrix bond has not been so thoroughly reported in the literature. A study of this relationship has been made on a co‐rotating twin screw extruder incorporating 30 percent by weight of glass fiber into nylon 66 to make the composite.Experimental results are presented to show how machine variables such as mixing configuration and screw speed affect the material properties and process efficiency. The properties of the composite were assessed by measurement of the fiber length distribution and tensile strength.From the results in the text it is possible to select machine variables to give desired production conditions. Although most of the work concerns the twin screw extruder, some of the consequences of subsequent injection molding are also show

ISSN:0272-8397    

DOI:10.1002/pc.750100206

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractA systematic study of the effect of surface pretreatment of cellulosic fibers and the processing time and temperature on the mechanical properties of the cellulose‐containing polypropylene was undertaken. Using non‐treated fibers, the elastic modulus increased gradually with the cellulose content, typically doubling its value at 30 phr fiber content. Treatment of fibers with coupling agent improves significantly the interfacial adhesion and therefore the mechanical properties of composite. Scanning electron micrographs reveal that the shear stress is sufficiently high to break and delaminate the cellulosic fibers. Addition of maleic anhydride modified polypropylene also improves the properties of resulting composi

ISSN:0272-8397    

DOI:10.1002/pc.750100207

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractCarbon fibers and pyrolytic graphite blocks were treated with plasma of acrylonitrile (AN) and styrene (ST) monomers, using an induction‐coupled, RF‐plasma reactor. Both substrates were stable towards plasma, leading to a deposition of thin, coherent coatings of 400Å∼1000Å thickness. Both monomers produced surfaces which are substantially more polar (γc=54 dynes/cm for AN and 40 dynes/cm for ST) than the untreated surfaces (γc=32 dynes/cm). ESCA and IR studies indicate that the plasma polymers contain a high concentration of oxygen (12 percent in PPAN and 17.8 percent in PPST), in the form of CO, COOH, COC, and OH groups. Also, treated fibers exhibited slightly higher tensile strengths than the untreated counterparts, suggesting that the plasma coatings effectively heal some of the surface flaws of the fiber. The abundant surface polar groups combined with the improved tensile properties of the plasma treated fibers make them attractive reinforcements for advanced comp

ISSN:0272-8397    

DOI:10.1002/pc.750100208

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractThe fiber length degradation during compounding (two‐roll milling and twin‐screw extrusion) of glass fiber and polypropylene (PP)/low density polyethylene (LDPE) blend matrices based composites was investigated. The effect of LDPE percentage and fiber content on fiber length were studied using a semiautomatic image analysis system. Two‐roll milling causes a more severe attrition of the fibers than twin‐screw extrusion. In the first case, the higher the LDPE percentage in the polymer matrix, the larger the final fiber length. Both methods lead to a broader fiber length distribution as LDPE percentage increases. The effect of fiber content is opposite to that of the LDPE percentage, but in the case of twin‐screw extrusion it is less noticeable, During the injection molding of the composites a slight decrease of the final fiber length takes place. This decrease depends on the initial fiber length, the effect being more pronounced for long

ISSN:0272-8397    

DOI:10.1002/pc.750100209

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractHigh‐modulus carbon‐fiber‐reinforced thermoplastic composites typically fail at the interface due to poor adhesion between fiber and matrix. To increase interfacial strength, the research described herein focuses on modifying the fiber surface (via high‐temperature acid treatment or zinc electrolysis) to facilitate chemical functional groups on the fiber that might increase fiber‐matrix inter‐actions. The thermoplastic matrix materials used in this study were random copolymers of ethylene and methacrylic acid in which the carboxyl groups in the methacrylic acid segments were neutralized with either sodium or zinc counterions. Mechanical tests were performed to determine the macroscopic effects of fiber pretreatment on the ultimate mechanical properties of the composites. Fabrication was designed such that fiber‐matrix separation provides the dominant contribution to mechanical gracture. Composites containing fibers treated with nitric acid, or a mixture of nitric and sulfuric acids exhibit a 20 to 25 percent increase in transverse (tensile) fracture stress relative to composites fabricated with as‐received fibers. Scanning electron microscopy of the fiber‐matrix interface at fracture allows one to “zoom‐in” and obtain qualitative details related to adhesion. Fracture surface micrographs of the above‐mentioned acid‐treated fiber‐reinforced composites reveal an increase in the amount of matrix material that adhered to the fiber surface relative to the appearance of the fracture surface of composites fabricated with as‐received fibers. The presence of acid functionality in the matrix, rather than the divalent nature of the zinc counterions, produces the largest relative enhancement of transverse (tensile) fracture stress in the above‐mentioned composites contain

ISSN:0272-8397    

DOI:10.1002/pc.750100210

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractStudies were performed to determine the toughness characteristics of composites prepared from modified addition‐type polyimides, using Celion 6000 graphite fiber as the reinforcement. The polyimides were prepared from aromatic diamines containing flexibilizing ether connecting groups. The composite flexural and short beam shear strengths were determined at room temperature and elevated temperatures. Composite toughness was evaluated using 10° off axis tensile tests and double cantilever beam fracture tests at room temperature. The effects of the flexibilized resin structure on composite mechanical properties, toughness characteristics, and thermo‐oxidative stability are discu

ISSN:0272-8397    

DOI:10.1002/pc.750100211

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY