摘要:

AbstractUnidirectional hybrid laminates based on glass fibers (GF) and high performance polyethylene fibers (PEF) were prepared with a partially polymerized methyl methacrylate (MMA) matrix at room temperature followed by heating at 55°C for the stipulated time (well below the softening point of PEF). The ultimate flexural strength (UFS), flexural modulus (FM) and interlaminar shear strength (ILSS) of the composites were determined and analyzed. An interesting observation of the study was the change in flexural behavior, which was largely dependent on the position of GF and PEF ply/plies in the compression and tension sides. When the ply/plies of PEF were at the tension side, the UFS and FM showed a higher value than that when GF plies were in the tension side of the hybrid composites. The ILSS also follows the same trend regarding the position of the GF and PEF plies

ISSN:1042-7147    

DOI:10.1002/pat.1995.220061001

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of pigments of different chemical compositions on the crystellization process of PP was studied by means of differential scanning calorimetry in isothermal mode. The Avrami equation was applied to obtain the crystallization parameters of polypropylene with different pigments.Lipatov's equations were applied for evaluation of the thickness and volume content of the transition layers. Results show that pigments affect not only the degree of crystallinity but also the structure of the amorphous phase and the integrity of the crystalline/amorphous interphase. Finally, the morphology and mechanical properties of pigmented polypropylene were studied in view of the different chemical compositions of the various pigments.

ISSN:1042-7147    

DOI:10.1002/pat.1995.220061002

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractCompositions of neat polyproylene (PP), PP–PE (polyethylene) blend and PP–PE–DBS (dibenzylidene sorbitol) were studied with respect to their crystallization kinetics by means of differential scanning calorimetry in isothermal mode. A modified Avrami equation was applied to obtain the crystallization parameters of PP, PP–PE and PP–PE–DBS. Optical and hot‐stage microscopy and dynamical analysis were used for structure determination.Experimental results have indicated that PE addition inhibits PP crystallization rate and acts as a plasticizer, while addition of DBS changes the crystallization kinetics. A detailed study of the DBS nucleation effects indicates that owing to the high surface energy, nuclei are formed during primary crystallization, leading to a fine PP crystalline structure and improved mechanic

ISSN:1042-7147    

DOI:10.1002/pat.1995.220061003

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractStable polyacrylamide (polyAA)–montmorillonite adducts were prepared by two distinct processes: (1) free radical copolymerization of AA with alkaline clay previously treated with 2‐(N‐methyl‐N,N‐diethyl ammonium iodide)ethylacrylate (QD1) and (2) direct interactions of alkaline montmorillonite with various preformed copolymers of AA with QD1. The structure of the adducts as determined by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X‐ray diffraction was shown to consist of AA macromolecules inserted between lamellar layers whose spacing was larger than in the polymer‐free clay. The polymer was strongly attached to the inorganic surfaces, probably due to cooperative formation of electrostatic bonding. The thermal stability of the organic polymers in the resulting complexes was substantially enhanced while the mobility of macromolecu

ISSN:1042-7147    

DOI:10.1002/pat.1995.220061004

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractEmulsion copolymerization of Tribromophenyl Maleimide (TBPMI) and styrene was conducted by semi‐batch and batch processes. The effects of monomer composition and copolymerization method on copolymerization rate, molecular weight and molecular weight distribution, latex particle size and size distribution, glass transition temperature (Tg), thermal stability and mechanical properties were investigated. A kinetic study has shown that the rate of copolymerization in the batch process increased with increasing TBPMI content in the monomer feed. For the semi‐batch polymerized samples, molecular weight decreased and molecular weight distribution increased with increasing TBPMI content in the monomer feed. For the batch polymerized samples, molecular weight also decreased but no obvious tendency was observed for the molecular weight distribution when TBPMI content increased. Compared with the batch copolymers, the semi‐batch copolymers have a higher molecular weight at the same initial monomer mixture composition. Latex particle size decreased, while particle size distribution slightly increased with increasing TBPMI content in both semi‐batch and batch latices. The semi‐batch samples exhibit only a single Tg, the value of which increses linearly with increasing TBPMI content. For the batch copolymers, two Tgs were found, reflecting a mixture of styrene‐rich and TBPMI‐rich copolymer chains. TGA results indicate that the thermal stability of the semi‐batch copolymers increased with increasing TBPMI concentration. Young's and flexural moduli increased, while tensile and flexural strengths decreased by increasing the TBPMI content for both the semi‐batch and batch specimens. The semi‐batch specimens have higher tensile and flexural strenghts

ISSN:1042-7147    

DOI:10.1002/pat.1995.220061005

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY