Industrial Activity in a Rural Environment

Zweifel, Bernhard O.

doi:10.2533/000942905777676939

Cited by 3 publications

(5 citation statements)

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“…The reorientation of polymer chains occurs in the amorphous regions where mobile polar groups migrate or rotate into the bulk. It is well known that oxidation of PO does not take place in the crystalline regions but in amorphous domains,79 and, due to creation of a greater number of oxygenic functional groups in PO with lower crystallinity, the surface modification by corona discharge plasma is more efficient 80,81…”

Section: Discussionmentioning

confidence: 99%

Study of Surface Properties of Polyolefins Modified by Corona Discharge Plasma

Novák

Pollák

Chodák

2006

Plasma Processes & Polymers

113

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Summary: Polyolefin surfaces, namely isotactic poly(propylene) (iPP) and low‐density polyethylene (LDPE), were modified by corona discharge plasma. The chemical changes on the modified surfaces were observed, deeply affecting the surface and the adhesive properties of the studied materials. The hydrophobic recovery in the case of iPP is considerably dependent on the polymer crystallinity. The presence of the processing agents in the LDPE has a significant influence on the surface hydrophobization dynamics.

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Section: Discussionmentioning

confidence: 99%

Study of Surface Properties of Polyolefins Modified by Corona Discharge Plasma

Novák

Pollák

Chodák

2006

Plasma Processes & Polymers

113

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“…3-5 are considered, we conclude that shot particles andbers in a given melt-blown web are structurally different. Absorption bands near 1600 -1800 and 3400 cm 2 1 have been assigned to PP oxidative degradation products, 10,11 and our spectral data suggest that shot particles consumed methylene and m ethyl groups during oxidative degradation 12,13 to produce a variety of oxidation products, including C5O and C5C groups (1600 -1800 cm 2 1 ), C-O groups (1168 cm 2 1 ), and hydroxyl or hydroperoxide groups (3400 cm 2 1 ).…”

Section: Resultsmentioning

confidence: 59%

“…Polypropylene Degradation Inside the Extruder. Thermal and m echanical reactions can lead to signi cant chain scission 12,17 that changes the polym er m olecularweight distribution (MW D). During extrusion, the shear rate can easily attain values that exceed 1000 s 21 near the barrel and in the mixing section.…”

Section: Resultsmentioning

confidence: 99%

“…11,16 For iPP, the predominant reactions are fragmentation and disproportionation of macroalkyl radicals that lead to chain scission and accumulation of carbon double bonds (C5C) and alkyl radicals in the melt. 12,13 If degradation occurs in this manner, we should expect to observe a C5C absorption band at 1645 cm 2 1 in FT-IR spectra of MB extrudate. As discussed previously, we obser ved a broad absorption band at 1600 -1800 cm 2 1 in our spectra of shot particles, but this band was relatively weak in spectra of bers.…”

Section: Resultsmentioning

confidence: 99%

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FT-IR Microspectroscopic Study of Shot Formation in Melt-Blown Webs

Bresee

2003

Appl Spectrosc

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We used Fourier transform infrared (FT-IR) microspectroscopy to investigate the chemical nature of fibers and defects called "shot" in melt-blown webs. Spectral differences were observed and evaluated in light of known thermal and oxidative degradation reactions for conditions comparable to those we used for melt blowing. Three different isotactic polypropylene polymers were evaluated in terms of the amount of shot produced and the amount of oxidative degradation exhibited by fibers and shot particles from each polymer. Little oxidative degradation was observed in fibers and the amount of degradation in fibers varied little for the three polymers we evaluated. Substantially more degradation was observed in shot particles, and the amount of degradation varied among the three polymers. Compared to polymer bound for fibers, we concluded that high temperature and mechanical shear in the extruder may introduce more chain scission in polymer bound for shot particles. Autoxidation reactions may occur after melt exits the die, and our data indicated that more oxidative degradation occurred in polymer that became shot particles than polymer that became fibers. The most favorable site for oxidation seemed to be tertiary rather than methylene hydrogen. Overall, the thermal history of polymer that becomes shot particles may be significantly different than the thermal history of polymer that becomes fibers, and this difference may have influenced shot formation.

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“…In the presence of UV > 240 nm and oxygen, the phenyl groups in PS, PPO, and PC can undergo ring-opening oxidation with formation of mucondialdehyde (Scheme 15.4) [36]. The radicals formed can undergo a variety of abstraction and decomposition reactions, resulting in a multitude of chemical products.…”

Section: Photo-fries Rearrangementmentioning

confidence: 99%

Polymer Degradation and Stabilization

Nguyen¹

2005

Handbook of Polymer Reaction Engineering

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IntroductionMost synthetic plastics and natural polymers are principally constituted of the elements C, H, N, and O, all of which are primary components of organic molecules. As with smaller organic molecules, these atoms are attached by relatively weak covalent bonds that are susceptible to chemical attack, particularly to oxidative degradation. During their potential lifetime, engineering plastics are exposed to diverse environmental factors which can act alone or in combination to adversely affect the initial material properties. These changes generally occur over several years, but can be accelerated or retarded in the presence of internal and external elements temperature, and temperature variations. Environmental factors that contribute to degradation include mechanical stresses, temperature variations, humidity, sunlight, oxygen, atmospheric pollutants, and microbial enzymes. Depending on the structural level at which material changes occur, it is usual to distinguish between physical, physicochemical, and chemical degradation.Physical degradation, commonly known as physical aging, results from changes in the thermodynamic state of the system (temperature, pressure, molar volume) during the daily use of the material. During processing, chains may be oriented and the sample inhomogeneously cooled, resulting in internal stress. With time, the chains have the opportunity to relax from their nonequilibrium conformations to a state of lower free energy. Partly immiscible blends, for instance, can remain in a homogeneous metastable state for an extended period of time. The presence of stress or heat can accelerate the phase separation process. The resultant changes in orientation, free volume, internal stress, crystalline content, and

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Industrial Activity in a Rural Environment

Cited by 3 publications

References 0 publications

Study of Surface Properties of Polyolefins Modified by Corona Discharge Plasma

Study of Surface Properties of Polyolefins Modified by Corona Discharge Plasma

FT-IR Microspectroscopic Study of Shot Formation in Melt-Blown Webs

Polymer Degradation and Stabilization

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