Search results for "Poly ethylene"

1975

The density of crystals of poly(ethylene terephthalate), (PETP), Qc is checked by X-ray diffraction assuming a triclinic unit cell and the indices of reflections as found by Bunn. The following unit cell dimensions are found: a = 4,48A, b = 5,85A, c = 10,75 A, α = 99,5°, β = 118,4°, and γ = 111,2°. This gives the density Qc as 1,515g/cm3 which is about 4% higher than that reported by Bunn. Negligible differences in spacings for samples annealed at different temperatures (120°C–260°C) have been found. Only for an annealing temperature of 100°C the higher d-values lead to Qc = 1,484g/cm3. For undrawn PETP films annealed at 250°C the same value of Qc as for drawn PETP was obtained on the basis…

Ester Functional Epoxide Monomers for Random and Gradient Poly(ethylene glycol) Polyelectrolytes with Multiple Carboxylic Acid Moieties

2020

The tailormade ester functional epoxides, methyl 4,5-epoxypentenoate (MEP) and tbutyl 4,5-epoxypentenoate (tBEP), were synthesized in good overall yields (60–65%) in short reaction sequences. Both ...

Incorporation of nisin in poly (ethylene-co-vinyl acetate) films by melt processing: a study on the antimicrobial properties

2011

Both industry and academia have shown a growing interest in materials with antimicrobial properties suitable for food packaging applications. In this study, we prepared and characterized thin films of ethylene-co-vinyl acetate (EVA) copolymer with antimicrobial properties. The films were prepared with a film blowing process by incorporating a nisin preparation as an antimicrobial agent in the melt. Two grades of EVA containing 14 and 28% (wt/wt) vinyl acetate (EVA 14 and EVA 28, respectively) and two commercial formulations of nisin with different nominal activities were used. The effect of the nisin concentration also was evaluated. The films with the highest antimicrobial activity were th…

Collapsibility of metastable sand by non-conventional oedometer tests

2018

The stability of foundations soils could represent a clear and present threat for the conservation of even well preserved buildings, particularly for Architectural heritage conservation and land art heritage. A dramatic case is the presence of collapsible metastable sands as foundation soils, as it occurs in the sacral complex Valle dei Templi in Agrigento. This site listed by UNESCO, stands on a crest of a calcarenite cuesta, overlaying a layer of these sands. When the collapsible sand is dry, the structure is strong enough to bond the sand particles together. When the sand becomes wet, a de-structuration mechanism occurs and the soil’s strength is compromised. This paper has a twofold aim…

Stereocomplex Formation in Polylactide Multiarm Stars and Comb Copolymers with Linear and Hyperbranched Multifunctional PEG

2013

Multicompartment Micelles with Adjustable Poly(ethylene glycol) Shell for Efficient in Vivo Photodynamic Therapy

2014

We describe the preparation of well-defined multicompartment micelles from polybutadiene-block-poly(1-methyl-2-vinyl pyridinium methyl sulfate)-block-poly(methacrylic acid) (BVqMAA) triblock terpolymers and their use as advanced drug delivery systems for photodynamic therapy (PDT). A porphyrazine derivative was incorporated into the hydrophobic core during self-assembly and served as a model drug and fluorescent probe at the same time. The initial micellar corona is formed by negatively charged PMAA and could be gradually changed to poly(ethylene glycol) (PEG) in a controlled fashion through interpolyelectrolyte complex formation of PMAA with positively charged poly(ethylene glycol)-block-p…

Reduction of the Interfacial Tension between Poly(dimethylsiloxane) and Poly(ethylene oxide) by Block Copolymers:  Effects of Molecular Architecture …

1997

Interfacial tensions σ were measured by means of the sessile drop method for mixtures of poly(ethylene oxide) [PEO, Mw = 41 kg/mol] with five samples of poly(dimethylsiloxane)s [PDMS, Mw ranging fr...

Effect of graphene nanoplatelets on the dielectric permittivity and segmental motions of electrospun poly(ethylene-co-vinyl alcohol) nanofibers

2021

The influence of the addition of graphene nanoplatelets (GNPs) on the intra/inter – molecular segmental motions of poly(ethylene-co-vinyl alcohol) (EVOH) was assessed by means of dielectric thermal analysis (DETA). The relaxation spectra were studied in terms of the dielectric permittivity (ε′) and the dielectric loss tangent (tan δ) at wide ranges of frequency (from 10−2 to 107 Hz) and temperature (from -150 to 140 °C). Two relaxation zones were disthinguished. Below the glass transition temperature (Tg), two β-relaxations were observed, which are characteristic local modes of mobility of the EVOH side groups, and related to the influence of the different surroundings of ethylene or vinyl …

The anisotropic behaviour of a preoriented poly (ethylene terephthalate) during plastic deformations

1978

Data on the anisotropic tensile behavior of samples cut along several directions of a biaxially oriented PET sheet are here presented. Shear deformations were observed together with the usual elongations. The data are compared with the predictions of a non-linear model recently proposed.

Competition between degradation and chain extension during processing of reclaimed poly(ethylene terephthalate)

1998

During processing of poly(ethylene terephthalate) (PET) hydrolytic chain scission, induced by the presence of small amounts of water, is the main cause of degradation. During repeated reprocessing chain scission can also occur because of the presence of other polymeric contaminants like PVC. In order to avoid or to limit hydrolytic chain cleavage adequate drying of PET before melt processing is necessary. Of course this practice is even more recommended when repeated processing steps are used, as for PET recycling. The behavior of recycling PET obtained from post-consumer water bottles when treated in a melt mixer under different conditions has been investigated in order to better understan…