Search results for " Polypropylene."

Resource or waste? A perspective of plastics degradation in soil with a focus on end-of-life options.

2018

‘Capable-of-being-shaped’ synthetic compounds are prevailing today over horn, bone, leather, wood, stone, metal, glass, or ceramic in products that were previously left to natural materials. Plastic is, in fact, economical, simple, adaptable, and waterproof. Also, it is durable and resilient to natural degradation (although microbial species capable of degrading plastics do exist). In becoming a waste, plastic accumulation adversely affects ecosystems. The majority of plastic debris pollutes waters, accumulating in oceans. And, the behaviour and the quantity of plastic, which has become waste, are rather well documented in the water, in fact. This review collects existing information on pla…

DIMENSIONAL STABILITY OF REINFORCED MATRICES.

1983

Particulate fillers are often used to improve the dimensional stability of polymeric items obtained through processing techniques such as injection molding, deep drawing, hot stamping, etc. In these operations the material undergoes large multiaxial deformations which result in molecular orientation and remain as frozen-in stresses during cooling of the material. Once the formed objects are exposed to sufficiently high temperatures, various degrees of spring-back take place and subsequent changes in shape and dimension occur (1).

Dielectric spectroscopy analysis of EVA-silicate nanocomposite insulating materials

2005

Nanocomposite materials show promising results for applications as electrical insulation. Among several materials presently under investigation, previous works indicate that polypropylene and ethylene-vinilacetate filled by nanosilicates present lower content of space charge and higher electric strength. However, efforts are needed to explain nanocomposite behaviour and characterize their electrical, thermal and mechanical properties. In this paper, the results of broad-band dielectric spectroscopy performed on ethylene-vinylacetate copolymer filled by layered micro and nanosized silicates are reported. The nanofillers consist of montmorillonite and fluorohectorite, that is, natural and syn…

Photo-oxidation of nano- and micro-filled polypropylene

2010

An Innovative Friction Stir Welding Based Technique to Produce Dissimilar Light Alloys to Thermoplastic Matrix Composite Joints

2016

Abstract Aluminum sheets can be joined to composite materials with different techniques. Each of them has advantages and weak points over the others. In literature, new techniques and patents are continuously developed to overcome these difficulties. In the paper a new Friction Stir Welding based approach is proposed to mechanically join AA6082-T6 to self-reinforced polypropylene. The aluminum sheet is pre-holed along both the sides of the weld line. A pinless tool generates the heat and pressure needed to activate back-extrusion of the composite. Joints have been produced with varying hole diameter and pitch. The mechanical resistance of the joint has been evaluated and the different failu…

Synthesis of PP-LCP graft copolymers and their compatibilizing activity for PP/LCP blends

1998

The aim of this work was the synthesis of new graft copolymers consisting of polypropylene (PP) backbones and liquid crystalline polymer (LCP) branches, to be used as compatibilizing agents for PP/LCP blends. The PP-g-LCP copolymers have been prepared by polycondensation of the monomers of a semiflexible liquid crystalline polyester (SBH 1 : 1 : 2), that is, sebacic acid (S), 4,4′-dihydroxybiphenyl (B), and 4-hydroxybenzoic acid (H) in the mole ratio of 1 : 1 : 2, carried out in the presence of appropriate amounts of a commercial acrylic-acid-functionalized polypropylene (PPAA). The polycondensation products, referred to as COPP50 and COPP70, having a calculated PPAA concentration of 50 and…

Mesophase formation in poly(propylene-ran-1-butene) by rapid cooling

2009

Abstract The effect of random insertion of low amount of 1-butene of less than about 11 mol% into the isotactic polypropylene chain on structure formation at non-isothermal crystallization at different rate of cooling was investigated by X-ray scattering, density measurements, and atomic force and polarizing optical microscopy. Emphasis is put on the evaluation of the condition of crystallization for replacement of lamellar crystals by mesomorphic nodules on increasing the cooling rate/supercooling. In the polypropylene homopolymer, mesophase formation occurs on cooling at rates larger about 150–200 K s −1 , while in case of poly(propylene- ran -1-butene) mesophase formation is observed on …

Effect of the Orientation on the Properties of Compatibilized Polypropylene/Liquid Crystal Polymer Blends

1999

Abstract Blends of polypropylene and a semirigid liquid crystal polymer have been compatibilized with an acrylic acid modified polypropylene and with an ad-hoc synthesized graft copolymer made from polypropylene and from the monomers of the liquid crystal polymer. The two compatibilizers improve the adhesion and the mechanical properties of the two incompatible phases. The two compatibilizers give about the same results. The effect of the compatibilization improve also the orientation of the liquid crystalline polymer particles and the mechanical properties.

Chemical composition and particle size influence the toxicity of nanoscale plastic debris and their co-occurring benzo(α)pyrene in the model aquatic …

2021

Little is known about how particle chemical composition and size might influence the toxicity of nanoscale plastic debris (NPD) and their co-occurring chemicals. Herein, we investigate the toxicity of 3 × 1010 particles/L polyethylene (PE, 50 nm), polypropylene (PP, 50 nm), polystyrene (PS, 200 and 600 nm), and polyvinyl chloride (PVC, 200 nm) NPD and their co-occurring benzo(a)pyrene (BaP) to Daphnia magna and Danio rerio. During the 21 days of exposure to PE 50 nm and PS 200 nm, the number of broods produced by D. magna decreased compared to other treatments. Exposure to BaP alone did not produce any effects on the reproduction of the daphnids, however, the mixture of BaP with PS (200 or …

Biologic response of inguinal hernia prosthetics: a comparative study of conventional static meshes versus 3D dynamic implants.

2015

Despite improvements in prosthetics and surgical techniques, the rate of complications following inguinal hernia repair remains high. Among these, discomfort and chronic pain have become a source of increasing concern among surgeons. Poor quality of tissue ingrowth, such as thin scar plates or shrinking scars-typical results with conventional static implants and plugs-may contribute to these adverse events. Recently, a new type of 3D dynamically responsive implant was introduced to the market. This device, designed to be placed fixation-free, seems to induce ingrowth of viable and structured tissue instead of regressive fibrotic scarring. To elucidate the differences in biologic response be…