摘要:

Scratch and mar of coatings is an important aspect of retaining initial performance levels. A number of test methods have been developed to measure coating resistance to damaging conditions. For the coatings industry, it is critical to have accelerated tests that indicate probable long term (i.e., service life) performance, and to have a means to correlate mar performance with chemical substructures of coatings. In this paper the synergism of measurement techniques for monitoring scratch and mar performance is explored. Laboratory mar tests, which have been validated by commercial experience, are used as the basis for comparison of a coating's performance. The combined elements of chemical, physical, mechanical, morphological and appearance properties of coatings have been explored. Chemical changes during cure and subsequent exposure have been followed by infrared techniques which show degree of cure, extent of photo-oxidation and hydrolysis, as well as changes in cross-linking with time and temperature. Physical and mechanical properties measured includeTg, hardness, standard stress/strain measurements, as well as “Method of Essential Work”. Physical properties can be correlated with visual recovery of plastic flow damage and resistance to mar. Furthermore, microscratch experiments have been utilized to explore forces that are needed to induce surface damage and to determine the transitions between elastic deformation, plastic flow, and brittle fracture type damage. Morphology of scratches was examined by the use of atomic force microscopy before and after exposure. Optical imaging techniques were used to characterize scratch and mar. These studies are useful in understanding mechanisms of coating failure.

ISSN:1023-666X    

DOI:10.1080/10236660008034629

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Low-molecular-weight fractions have been isolated from polystyrene, poly(vinyl chloride) and high-density polyethylene (HDPE) by fractionation methods. These fractions were subjected to high-performance gel permeation chromatography (HPGPC) to separate individual oligomer species. Repeated injection of fractions and collection of the individual oligomers allowed characterization by nuclear magnetic resonance spectroscopy and mass spectroscopy. Structures for end groups in these oligomers have been deduced, and shown to be consistent with polymerization mechanisms for the formation of each addition polymer. An example of an HPGPC procedure is provided for quantifying the concentration of an oligomer in HDPE by a standard addition method.

ISSN:1023-666X    

DOI:10.1080/10236660008034630

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The thermal degradation of poly(p-nitrostyrene) has been studied by mass spectrometric thermal analysis and pyrolysis gas chromatography. It was shown that the main thermal degradation process is depolymerization. Polymer cross-linking leads to a change in the thermal degradation mechanism.

ISSN:1023-666X    

DOI:10.1080/10236660008034631

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A new experimental setup for detecting flow-rate fluctuations caused by the passage of polymer through a separation system, including a differential refractometer and a singlecapillary on-line viscometric detector in size exclusion chromatography (SEC) is demonstrated. Numerical methods for correction of elution volume and the baseline of the viscometric output, including the “Lesec effect”, are presented on SEC data of (2-hydroxy-ethyl) cellulose in 50% methanol/50% water 10 mM NaCl (mobile phase). The effect of flow-rate fluctuations on experimental molecular weight averages is discussed.

ISSN:1023-666X    

DOI:10.1080/10236660008034632

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Hemicellulose B (arabinoxylan, corn fiber gum, CFG) was prepared from corn fiber (CF) by alkaline extraction with 2 meq/g of CF using either NaOH, Ca(OH)2or an equimolar mixture of the two. Prior to CFG extraction, oil was removed from CF by extraction with hexane and starch was removed from CF by treatment with α-amylase. The solutions of alkali-extracted CFG were then bleached with alkaline H2O2. The effect of extractant composition on the weight-average molar massMw, weight-average intrinsic viscosity [η]w, andz-average root-mean-square radius of gyrationRgzon CFG was determined. Depending on extractant composition and method of calculation,Mwranged from 2.7–6.96 × 105, [η]wfrom 1.87 to 2.00 dL/g andRgzfrom about 31 to 50 nm. Substituting Ca(OH)2for NaOH reducedMwandRgzbut had little or no effect on [η]w. Chromatographic analysis in conjunction with molar mass detection revealed that molar mass distributions were bimodal.Mwfor the high-molar-mass component ranged from about 8.4–16.1 × 105, whereasMwranged from about 1.1–2.1 × 105for the low-molar-mass component. The high-molar-mass component comprised about 15–43% by weight of CFG and was much more compact in shape than the low-molar-mass component.

ISSN:1023-666X    

DOI:10.1080/10236660008034633

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Poly(methyl methacrylate)-graft-polydimethylsiloxane (PMMA-graft-PDMS) samples with different compositions were prepared by radical copolymerization of PDMS macromonomer with methyl methacrylate. The chemical composition distributions (CCDs) of the graft copolymer samples were determined by the high-performance liquid chromatography (HPLC) based on the reversed-phase adsorption mode, using a prepacked column of butyl-modified silica gel and the linear gradient elution of acetonitrile and tetrahydrofuran. The CCD of one of the graft copolymer samples was also determined by the demixing-solvent fractionation using the demixing-solvent pair of dimethylsulfoxid-tetrachloroethylene reported by Stejskalet al.The CCD by HPLC was in good agreement with theoretical CCD, while the CCD by the demixing-solvent fractionation was narrower than those by the HPLC and the theoretical calculation.

ISSN:1023-666X    

DOI:10.1080/10236660008034634

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Highly isotactic and syndiotactic copolymers of methyl methacrylate (MMA) and butyl methacrylate (n-BuMA) with random monomer sequence distribution were prepared in toluene at -78°C witht-C4H9MgBr andt-C4H9Li/(C2H5)3Al, respectively.13C NMR spectra of carbonyl region of the copolymers were measured in chlorobenzene-d5at 115°C and 125 MHz and analyzed in regard to both monomer sequence and configurational sequence distributions.13C NMR spectra of radically prepared poly(MMA-ran-n-BuMA)s were also analyzed based on the assignments established by the analysis of the spectra of the stereoregular copolymers.

ISSN:1023-666X    

DOI:10.1080/10236660008034635

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The changes in composition of an abiotically degraded polyester-amide, poly(butylene adipate-co-caproamide), in an aqueous environment at 37°C; 60°C and 80°C were investigated. The changes in polymer composition were studied using pyrolysis-GC-MS,1H-NMR, FTIR, and size exclusion chromatography, and degradation products were analyzed by solid-phase extraction and subsequent GC-MS. During the degradation of PEA in an aqueous environment, the main degradation products were 6-aminohexanoic acid, 1-hydroxydodecanoic acid-6-one-5-oxo and dimers. After longer degradation times and at higher degradation temperatures, 1-hydroxydodecanoic acid-6-one-5-oxo was cleaved further into hexanedioic acid and 1,4-butanediol. At 80°C, the degradation was fastest with the largest weight loss due to dissolution of oligomer. At 80°C, the amide content in the copolymer increased with increasing degradation time. We suggest that there is a two-step degradation mechanism with the formation of linear degradation products, where the hydrolysis of ester bonds is favored over that of amide bonds.

ISSN:1023-666X    

DOI:10.1080/10236660008034636

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

1H,13C and29Si NMR spectroscopy was used to study the terminal structures, stereoregularity, and optical activity of silicon-containing polymers. In the ring-opening polymerization of 1,1,2-trimethylsilacyclobutane using a platinum catalyst, extensive chain transfer reactions occurred. The five-membered cyclic carbosiloxane could be easily polymerized by phenyllithium to give a high-molecular-weight polymer through regioselective ring-opening. Polymerization of optically active allylsilane, vinylsiloxane, and cyclic carbosiloxane gave highly isotactic poly(carbosilane) and poly(carbosiloxane).

ISSN:1023-666X    

DOI:10.1080/10236660008034637

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Nonisothermal crystallization behavior of blends of poly(ethylene terephthalate) (PET)-nylon 6 has been investigated. Component polymers in the blends exhibited separate crystallization and melting peaks. Nonisothermal crystallization parameters, like rate of crystallization, has changed for both the component polymers, whereas the degree of crystallinity has increased for PET with increasing amount of nylon 6 in the blends and decreased for nylon 6 with increasing amount of PET in blends. Thus blending seems to have improved crystallization parameters.

ISSN:1023-666X    

DOI:10.1080/10236660008034638

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor