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Role of slip additives in blown film extrusion of low density polyethylenes
Vol.
POiJDER PROCESSING OF IRON-FILLED UI3t&JPE
18,
No. 5,
Page
16
High molecular weight polymers such as UHMWPE are difficult to process by conventional melt-forming techniques since they retain their high viscosity in the melt. In an attempt to overcome these deficiencies, an alternative powder-processing technique has been developed. This approach essentially consists of cold compaction of the powder followed by sintering. The technique may show faster processing times when compared to melt processes such as compression moulding. In the powder approach, compaction takes only a few minutes. However, sintering is time-consuming, because coalescence of the polymer particles takes place by viscous flow, which is an inherently leisurely process. Also, since heat must be conducted through the polymer from the outside, its insulating nature causes the properties to vary across the width of the sample. Changes in preform dimension due to viscoelastic recovery after compaction and during sintering can be significant. This paper describes how a conductive filler (iron) was incorporated into the polymer to provide conductivity while keeping the filler level to approximately 10 vol.-$. This conductive path enhanced the heat transfer, achieved heating uniformity, and reduced the sintering time. Mod. Plast. Int., 1988,
SIElF'LIFIED MASTERBATCH PRODUCTION
18,
(Feb.), 42
New BTS twin screw compounding extrusion lines produced by Betol are suitable for thermoplastics and thermoset systems incorporating high filler loadings, heat sensitive additives and/or shear sensitive additives. The process is primarily an intensive mixing operation carried out at sufficient temperature to soften the base polymer, thus facilitating the efficient dispersion of pigments and other additives. The modular screw and barrel sections are fully interchangeable In masterbetch for flexibility in processing characteristics. the closely intermeshing screw profile allows high compounding, degrees of dispersion for heavily loaded masterbatches. A novel hydraulically assisted horizontal barrel withdrawal mechanism allows rapid access to the screws for cleaning. A high torque DC motor is fitted with tacho feedback for precise speed holding.
ROLE OF SLIP ADDITIVES IN BLOWN FILM EXTRUSION OF LOW DENSITY POLYETHYLENES
In this study, the effects of slip additives on the rheology of low density polyethylene resins and the mechanical, optical and surface characteristics of blown films were investigated. It is determined that the slip additive remains dispersed in the At relatively high matrix during flow through the capillaries. concentrations the slip additive adversely affects some of the ultimate film properties including tensile strength and haze. Plast.
POLYMERS
1999 Elsevier Science Publishers B.V., Amslerdam./88/$0.00 + 2.20 No part of this publication may he reproduced, stored in a retrieval system, or transmitted by any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers (Readers in the U.S.A. - please see special regulations listed on back cover.)
POiJDER PROCESSING OF IRON-FILLED UI3t&JPE
18,
No. 5,
Page
16
High molecular weight polymers such as UHMWPE are difficult to process by conventional melt-forming techniques since they retain their high viscosity in the melt. In an attempt to overcome these deficiencies, an alternative powder-processing technique has been developed. This approach essentially consists of cold compaction of the powder followed by sintering. The technique may show faster processing times when compared to melt processes such as compression moulding. In the powder approach, compaction takes only a few minutes. However, sintering is time-consuming, because coalescence of the polymer particles takes place by viscous flow, which is an inherently leisurely process. Also, since heat must be conducted through the polymer from the outside, its insulating nature causes the properties to vary across the width of the sample. Changes in preform dimension due to viscoelastic recovery after compaction and during sintering can be significant. This paper describes how a conductive filler (iron) was incorporated into the polymer to provide conductivity while keeping the filler level to approximately 10 vol.-$. This conductive path enhanced the heat transfer, achieved heating uniformity, and reduced the sintering time. Mod. Plast. Int., 1988,
SIElF'LIFIED MASTERBATCH PRODUCTION
18,
(Feb.), 42
New BTS twin screw compounding extrusion lines produced by Betol are suitable for thermoplastics and thermoset systems incorporating high filler loadings, heat sensitive additives and/or shear sensitive additives. The process is primarily an intensive mixing operation carried out at sufficient temperature to soften the base polymer, thus facilitating the efficient dispersion of pigments and other additives. The modular screw and barrel sections are fully interchangeable In masterbetch for flexibility in processing characteristics. the closely intermeshing screw profile allows high compounding, degrees of dispersion for heavily loaded masterbatches. A novel hydraulically assisted horizontal barrel withdrawal mechanism allows rapid access to the screws for cleaning. A high torque DC motor is fitted with tacho feedback for precise speed holding.
ROLE OF SLIP ADDITIVES IN BLOWN FILM EXTRUSION OF LOW DENSITY POLYETHYLENES
In this study, the effects of slip additives on the rheology of low density polyethylene resins and the mechanical, optical and surface characteristics of blown films were investigated. It is determined that the slip additive remains dispersed in the At relatively high matrix during flow through the capillaries. concentrations the slip additive adversely affects some of the ultimate film properties including tensile strength and haze. Plast.
POLYMERS
1999 Elsevier Science Publishers B.V., Amslerdam./88/$0.00 + 2.20 No part of this publication may he reproduced, stored in a retrieval system, or transmitted by any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers (Readers in the U.S.A. - please see special regulations listed on back cover.)