Search results for " polypropylene"

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…

THERMOMECHANICAL DEGRADATION OF A POLYPROPYLENE/GRAPHENE NANOCOMPOSITE

2016

In this work the morphology and the rheological and mechanical properties of a nanocomposite made of a polypropylene with graphene nanoplatelets (GNP) have been investigated as a function of the compounding parameters to evaluate the thermomechanical degradation behaviour of this system. The presence of graphene seems to reduce the thermomechanical degradation of the matrix. A better dispersion of the GNP seems the cause of this behaviour.

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).

Morphogenetically-Active Barrier Membrane for Guided Bone Regeneration, Based on Amorphous Polyphosphate

2017

We describe a novel regeneratively-active barrier membrane which consists of a durable electrospun poly(ε-caprolactone) (PCL) net covered with a morphogenetically-active biohybrid material composed of collagen and inorganic polyphosphate (polyP). The patch-like fibrous collagen structures are decorated with small amorphous polyP nanoparticles (50 nm) formed by precipitation of this energy-rich and enzyme-degradable (alkaline phosphatase) polymer in the presence of calcium ions. The fabricated PCL-polyP/collagen hybrid mats are characterized by advantageous biomechanical properties, such as enhanced flexibility and stretchability with almost unaltered tensile strength of the PCL net. The pol…

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…

Photo-oxidation behaviour of micro- and nano-filled polypropylene: effect of the filler type and compatibilizer precursor

2011

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 …

Impact of different texture of polypropylene mesh on the inflammatory response.

2008

Morphology, reorganization and stability of mesomorphic nanocrystals in isotactic polypropylene

2006

Abstract The morphology and thermodynamic stability of crystals of isotactic polypropylene (iPP) were analyzed as a function of the path of crystallization by atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Samples were melt-crystallized at different rates of cooling using a “controlled rapid cooling technique”, and subsequently annealed at elevated temperature. Mesomorphic equi-axed domains with a size less than 20 nm were obtained by fast cooling from the melt at a rate larger about 100 K s−1. These domains stabilize on heating by growing in chain direction and cross-chain direction, to reach a maximum size of about 40–50 nm at a temperature of 433 K, with the q…

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…