Search results for "Plastics"

A contribution to the kinetics of the polymerization of styrene with CF3SO3H as catalyst

1978

The time dependence of the cationic polymerization of styrene in CH2Cl2 with CF3SO3H as catalyst can be formally described as being first-order with respect to monomer concentration [M]0. The reaction rate shows a third-order dependence in catalyst concentration [C]0. A high polymer and a low polymer polystyrene fraction are found at [M]0>0.2 mole · l−. The reaction rate of the high polymer fraction is proportional to [C] 0 3 , that of the low polymer fraction probably proportional to [C] 0 2 . The polymerization active species may thus be triple ions in the first and ion pairs in the second case.

Optimization of Cell Growth on Bacterial Cellulose by Adsorption of Collagen and Poly-L-Lysine

2015

Poly-L-lysine and collagen were separately added to bacterial cellulose (BC) nanofibers. The ionic surface charge had been previously modified in order to promote the adsorption of poly-L-lysine and collagen. Cell adhesion of Chinese hamster ovary (CHO) cells on BC surfaces was confirmed by removing unattached cells from the BC substrates. Cell viability was calculated and it was determined that both poly-L-lysine-BC and collagen-BC substrates are viable for cell growth. The results showed that the cell viability in poly-L-lysine modified BC substrate is similar to the one observed in polystyrene tissue culture plates.

Influence of small amounts of polyvinylchloride on the recycling of polyethyleneterephthalate

1999

Abstract Polyethylene terephthalate (PET), and polyvinyl chloride (PVC), are commonly encountered in plastics stream coming from separate collections of plastic bottles. The presence of PVC in the recycled PET is very dangerous because of the chain scission provoked by the hydrogen chloride evolved from the macromolecules during degradation of PVC. Recycled PET must be free of PVC; contents of PVC as little as 100 ppm can induce degradation and discoloration of the polyester. PET, in its turn, is degraded when the processing is carried out in the presence of water. In previous work, however, the degradation of PET was eliminated and rather an increase of the molecular weight has been measur…

Influence of sodium bicarbonate treatment on the aging resistance of natural fiber reinforced polymer composites under marine environment

2019

Abstract Aim of the current study is to investigate how an innovative and eco-friendly chemical treatment based on sodium bicarbonate solution (10 wt%) can improve the aging resistance in marine environment of epoxy based composites, reinforced with flax and jute fibers. To this scope, treated and untreated fiber reinforced composites were manufactured through vacuum infusion technique. The resulting composites were then exposed to salt-fog spray conditions up to 60 days, according to ASTM B117 standard. The assessment of their durability was made by means of tensile, flexural quasi-static tests and Charpy impact tests. Furthermore, the water uptake evolution of each composite was monitored…

The effect of prepolymerization of a titanium catalyst on its deactivation in propylene polymerization

1997

Propylene polymerization rate was investigated in the presence of anunsupported titanium catalyst (TiCl3) that had been modified with a Lewis base (di-n-butyl ether) and activated (precat), or not activated (cat), by being used in a suspension prepolymerization (70°C, 0.6 MPa) of an identical monomer. The initial polymerization rate was higher with the precat than with the cat catalyst. Prepolymerization was also found to enhance the kinetic stability of catalyst's active sites, presumably by reason of the prepolymerization-induced modification of catalyst's morphology. Deactivation rate constants were evaluated for the active sites of either catalyst examined.

Dynamic Model Metallo‐Supramolecular Dual‐Network Hydrogels with Independently Tunable Network Crosslinks

2020

Studies of alumina as a support of titanium catalyst for low-pressure ethylene polymerization

1986

The effect of alumina treatment with aqueous solutions of hydrochloric acid and ammonium fluoride as well as temperature of its calcination on the activity of Al-Ti/Al2O3 supported organometallic catalyst for ethylene polymerization has been studied. The dependence between the spe­cific surface area of the support and both the kind and concentration of the modifying agent, concentration of OH-groups on Its surface and concentration of active centres with various activities is discussed with reference to the activity of the supported Al-Ti/Al2O3 catalyst. It was demonstrated that there is no simple relationship between the concentration of OH-groups on the support and the activity of the Ti-…

Blends of nylon 6 with a polyethylene functionalized by photooxidation

1990

An easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt-blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved b…

Macromol. Chem. Phys. 21/2013

2013

Study of methyl methacrylate polymerization in the presence of rubbers

2001

Grafting of poly(methylmethacrylate) onto various unsaturated rubbers is described. The grafting is achieved through thermally initiated methylmethacrylate in-situ polymerization. The main features of the polymerization process, i.e. conversion vs. time, grafting to rubber and gel percentage, have been investigated. The chemical structure of the rubber influences the process: rubber with pendant unsaturations gives rise to higher level of grafting.