A mathematical model of melt-fracture in polymers.

Prastaro, Agostino (Cent. Ric., Montedison S.p.A., Ferrara, Italy).

Quad. Ing. Chim. Ital., 13(3-4), 37-44 (Italian) 1977. CODEN: QICIAU.

A nondimensional no., the critical Weissenberg no. (Wc), which characterized the onset of instability in the flow of a polymer melt, was used in the development of a math. model of melt-fracture which could be used to predict and account for the extrusion characteristics of any polymer.

A comparative study of melt fracture in capillaries and slits.

Vlachopoulos, J.; Chan, T. W. (Dep. Chem. Eng., McMaster Univ., Hamilton, Ont., Can.). Proc. - Int. Conrg. Rheol., 7th, 178-9. Edited by: Klason, C.; Kubat, Josef. Swed. Soc. Rheol., c/o Dep. Polym. Mater., Chalmers Univ. Technol.: Goeteborg, Swed. (English) 1976. CODEN:

The onset of melt fracture in polystyrene (I) [9003-53-6] and polyethylene (II) [9002-88-4] took place at higher shear stresses when extruded through slt dies than through capillary dies. Extrudate distortion through slit dies showed mid-section buckling, surface roughness, and ragged edges, whereas spiral or wavy distortion occurred in capillary dies. The flow-av. value of recoverable shear should be used as a criterion for initiation of melt fracture.

Scarola, Leonard Sebastian; Kurtz, Stuart Jacob; Blakeslee, Theodore

Robert, III (Union Carbide Corp., USA). S. African ZA 8000112 31 Dec

1980, 76 pp. (English). (South Rica).

Origin of sharkskin.

Weill, A. (Ec. Appl. Hauts Polym., Univ. Louis Pasteur, Strasbourg, Fr.). Rheol. Acta, 19(5), 623-32 (English) 1980. CODEN: RHEAAK. ISSN: 0035-4511. DOCUMENT The main flow instability and the sharkskin phenomenon in linear polyethylene [9002-88-4] melt flow are presented in terms of relaxation oscillator theory, and permit an understanding of the influence of exptl. parameters on the period of oscillatory flow. Sharkskin is interpreted to be the same phenomenon as the other instability, but to occur in the die entry region rather than in the whole die itself. Various aspects of sharkskin characteristics in extrudates are considered.

Cogswell, Frederic N. (Imperial Chemical Industries Ltd., Engl.). Can. CA 1028114 21 Mar 1978, 22 pp. (English). (Canada). CODEN: CAXXA4. NCL: 18-188. PRIORITY: GB 72-32559 12 Jul 1972. DOCUMENT TYPE: Patent CA Section: 37 (Plastics Fabrication and Uses)

Rudin, Alfred; Chang, Rong-Jong (Dep. Chem. Eng., Univ. Waterloo, Waterloo, Ont., Can.). J. Appl. Polym. Sci., 22(3), 781-99 (English) 1978. CODEN: JAPNAB. ISSN: 0021-8995. DOCUMENT TYPE: Journal CA Section: 35 (Synthetic High Polymers)

Linear polyethylene [9002-88-4] behaved differently from most other polymers in fixed piston-speed extrusion and during melt fracture because of the existence of a extensive entanglement network in the melt. The polymer was extruded from a capillary rheometer with driving piston operated at fixed speed and at fixed pressure. Apparent d. decreased at shear rates approaching melt fracture region in fixed-piston-speed operation. Flow of other polymer melts were essentially incompressible in fixed-piston-speed operation, and all polymers exhibited incompressible flow in fixed-pressure extrusion. The oscillating portion of the flow curve reflects alternating periods in which the polymer exits faster and slower than the rate at which the advancing piston clears the rheometer reservoir.

Three layer film.

Horner, Jerome Thomas; Anthony, John; Fraser, William Allen (Union Carbide Corp. , USA). Eur. Pat. Appl. EP 32629 29 Jul 1981, 12 pp. (English). (European Patent Organization).

A flexible coextruded 3-layer film, free from melt fracture, comprises outer layers of high-pressure, low-d. polyethylene (I) [9002-88-4] and a core layer of low-pressure, low-d I. Thus, a film having outer layers of high-pressure I (0.18 mil thickness) and a core layer of low-pressure I (1.4 mil thickness) had no melt fracture.

Ramamurthy, Arakalgud (Union Carbide Corp., USA). U.S. US 4554120 A 19 Nov 1985, 16 pp. Cont.-in-part of U.S. Ser. No. 508,667, abandoned. (English). (United States of America). CODEN: USXXAM. CLASS: IC: B29F003-04. NCL: 264085000.

Ramamurthy, Arakalgud V. (Union Carbide Corp., USA). U.S. US 4552712 A 12 Nov 1985, 9 pp. Cont.-in-part of U.S. Ser. No. 508,670, abandoned. (English). (United States of America). CODEN: USXXAM. CLASS: IC: B29F003-04. NCL: 264085000. APPLICATION: US 84-627516 3 Jul 1984. PRIORITY: US 83-508670 28 Jun 1983.

Ramamurthy, Arakalgud Venkatapathia (Union Carbide Corp. , USA). S. African ZA 8404921 A 27 Mar 1985, 36 pp. (English). (South Rica). CODEN: SFXXAB. CLASS: ICM: C08F. ICS: C08G. APPLICATION: ZA 84-4921 27 Jun 1984. PRIORITY: US 83-508670 28 Jun 1983. DOCUMENT TYPE: Patent CA Section: 38 (Plastics Fabrication and Uses)

In the title process, linear monodisperse C2H4 polymers contg. adhesion promoters are extruded through dies having die land regions defining opposing surfaces terminating in die gaps, ³1 surface being of stainless steel, with die land-die gap ratio 35-60:1, the melt fracture being reduced on the surface of the polymer adjacent to the stainless steel surface. Thus, a 1-butene-ethylene copolymer [25087-34-7] (d. 0.918) contg. 800 ppm diethoxylated tertiary fatty amine (Kemamine AS 990 [99241-69-7], as adhesion promoter) was extruded through a die, having opposing die land surfaces of stainless steel 304 with land length 2.2 in. and gap 40 mil, at 220° and blown (ratio 2) to give a 1.5-mil film exhibiting little surface melt fracture.

Reducing melt fracture during extrusion of a molten narrow-molecular-weight-distribution, linear ethylene copolymer.

Kurtz, Stuart Jacob (Union Carbide Corp. , USA). S. African ZA 8106335 A 29 Sep 1982, 38 pp. (English). (South Rica). CODEN: SFXXAB. APPLICATION: ZA 81-6335 11 Sep 1981. PRIORITY: US 80-192701 1 Oct 1980. DOCUMENT TYPE: Patent CA Section: 38 (Plastics Fabrication and Uses)

Eliminating surface melt fracture when extruding ethylene polymers.

Ramamurthy, Arakalgud Venkatapathia (Union Carbide Corp. , USA). S. African ZA 8404926 A 27 Feb 1985, 61 pp. (English). (South Rica). CODEN: SFXXAB. CLASS: ICM: C08F. ICS: C08G. APPLICATION: ZA 84-4926 27 Jun 1984. PRIORITY: US 83-508667 28 Jun 1983. DOCUMENT TYPE: Patent CA Section: 38 (Plastics Fabrication and Uses)

Ethylene copolymers are extruded at high rates without melt fracture by using brass dies and diethoxylated fatty amine stabilizers. Thus, butene-ethylene copolymer contg. 320 ppm Kemamine AS 990 was extruded at 66 lb/h through a brass (35:61.5:3.05 Zn-Cu-Pb-Fe) die without melt fracture, vs. severe surface melt fracture with a chrome plated die.

(Union Carbide Corp. , USA). Indian IN 152491 A 28 Jan 1984, 75 pp. (English). (India). CODEN: INXXAP. CLASS: IC: B29D001-00; B29D007-00; B29F001-022; B29F003-00; C08F003-04. APPLICATION: IN 80-CA26 7 Jan 1980. PRIORITY: US 79-1932 8 Jan 1979; US 79-99061 12 Dec 1979. DOCUMENT TYPE: Patent CA Section: 38 (Plastics Fabrication and Uses)

Kurtz, Stuart Jacob (Union Carbide Corp. , USA). S. African ZA 8202239 A 23 Feb 1983, 30 pp. (English). (South Rica). CODEN: SFXXAB. APPLICATION: ZA 82-2239 31 Mar 1982. PRIORITY: US 81-249914 1 Apr 1981. DOCUMENT TYPE: Patent CA

Additional observations on the surface melt fracture behavior of linear low-density polyethylene.

Moynihan, R. H.; Baird, D. G.; Ramanathan, R. (Dep. Chem. Eng., Virginia Polytech. Inst. and State Univ., Blacksburg, VA, USA). J. Non-Newtonian Fluid Mech., 36, 255-63 (English) 1990. CODEN: JNFMDI. ISSN: 0377-0257. DOCUMENT TYPE: Journal CA Section: 36 (Physical Properties of Synthetic High Polymers)

An exptl. investigation of the surface melt fracture behavior of linear LDPE is reported. The results of capillary expts. with different length-diam. ratios and slit-die expts. with various regions coated with fluorolastomer are presented; the role of the entry, land and exit regions in the surface melt fracture behavior is examd. In agreement with the mechanism proposed by Kuritz, the surface melt fracture arises at the die with the aid of prestressing conditions upstream of the exit.

Lee, Young Sil; Park, O Ok (Dept. of Chem. Eng., Korea Advanced Institute of Science and Technology, Taejon 305-701, S. Korea). Korean J. Chem. Eng., 11(1), 1-7 (English) 1994. CODEN: KJCHE6. ISSN: 0256-1115. DOCUMENT TYPE: Journal CA Section: 38 (Plastics Fabrication and Uses) Section cross-reference(s): 39

Lu, Jing; Barry, Carol M. F.; Orroth, Stephen A. (University of Massachusetts, Lowell, MA, USA). Annu. Tech. Conf. - Soc. Plast. Eng., 55th(Vol. 1), 347-350 (English) 1997 Society of Plastics Engineers CODEN: ACPED4. ISSN: 0272-5223. DOCUMENT TYPE: Journal CA Section: 38 (Plastics Fabrication and Uses)

Gendron, R.; Piche, L.; Hamel, A.; Dumoulin, M. M.; Tatibouet, J. (Industrial Materials Institute, NRC, Boucherville, PQ J4B 6Y4, Can.). Annu. Tech. Conf. - Soc. Plast. Eng., 55th(Vol. 2), 2254-2256 (English) 1997 Society of Plastics Engineers CODEN: ACPED4. ISSN: 0272-5223. DOCUMENT TYPE: Journal CA Section: 38 (Plastics Fabrication and Uses)

The melt fracture behavior, including sharkskin and gross distortion of the extrudate of various linear low-d. polyethylenes, LLDPE, was investigated using both std. off-line capillary rheometry and an in-line ultrasonic method. Extrusion was performed on a single screw extruder, equipped with a slit die instrumented with ultrasonic probes. Ultrasonic results and occurrence of sharkskin were closely related, which would tend to demonstrate that the initiation of surface melt fracture is consequent to the adhesion failure at the interface die/polymer

Kurtz; Stuart J. , Martinsville, NJ

Blakeslee, III; Theodore R. , Hillsborough, NJ

Scarola; Leonard S. , Union, NJ

Applicant(s): Union Carbide Corporation, New York, NY

Inventor(s): Chyu; Hyun S. , Chicopee, MA

Applicant(s): Monsanto Company, St. Louis, MO News, Profiles, Stocks and More about this company

Issued/Filed Dates: Nov. 30, 1976 / Jan. 2, 1975

The present invention relates to an improvement in a die for extruding thermoplastic sheet having a controlled degree of microsurface roughness. The improvement comprises having a beveled leading edge on at least one of the die lips wherein the bevel is away from the die orifice in order to control the degree of microsurface roughness in the extruded sheet.

Kim, Youn Cheol; Yang, Kyoung Sun (CORPORATE SOURCE Compounds & Application R & D Team, Research and Development Center, Samsung Chemical Group, Taejon 305-380, S. Korea). SOURCE Polym. J. (Tokyo), 31(7), 579-584 (English) 1999 Society of Polymer Science, Japan. CODEN: POLJB8. ISSN: 0032-3896. DOCUMENT TYPE: Journal CA SECTION/CROSS-REFERENCE(S) CA Section: 37 (Plastics Manufacture and Processing) Section cross-reference(s): 38

A com. linear low d. polyethylene (LLDPE) was modified by adding a small amt. dicumyl peroxide (DCP) during extrusion at moderate processing temp. (200°C). The effects of peroxide modification were to change the mol. wt. and rheol. properties, as evident by increase in high mol. portion, shear sensitivity and melt viscosity at low frequency region. These effects were confirmed by gel permeation chromatog. (GPC) and Rheometric dynamic spectrometer (RDS). One outstanding feature of peroxide modification was the remarkable delay in the onset of melt fracture upon extrusion. The diln. of DCP in polypropylene (PP) powder was more effective for improvement of these properties than by direct loading of DCP. The obsd. remarkable delay in melt fracture is believed to be due to increase in high mol. portion by producing long chain branch and crosslinking. That is, DCP modification results in delay in the onset of melt fracture through increase in high mol. portion which can resist high elongational stress when leaving the die.

Rosenbaum, Eugene E.; Randa, Stuart K.; Hatzikiriakos, Savvas G.; Stewart, Charles W.; Henry, Donald L.; Buckmaster, Marlin D. (CORPORATE SOURCE Department of Chemical Engineering, The University of British Columbia, Vancouver, BC, Can.). SOURCE Annu. Tech. Conf. - Soc. Plast. Eng., 56th(Vol. 1), 952-956 (English) 1998 Society of Plastics Engineers. CODEN: ACPED4. ISSN: 0272-5223. DOCUMENT TYPE: Journal CA SECTION/CROSS-REFERENCE(S) CA Section: 37 (Plastics Manufacture and Processing) Section cross-reference(s): 38, 42

The influence of a new processing additive (a compn. of fine particles of boron nitride) on the processability of polyolefins and fluoropolymers in extrusion is studied. The equipment used includes both an Instron capillary rheometer with two types of dies, namely capillary dies and special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer, and a 31.725 mm Entwistle extruder. A metallocene LLDPE and several tetrafluoroethylene perfluoropolymers were tested using these two pieces of equipment. The greatest influence of the additive occurs in crosshead dies and tips, where the additive particles seem to enhance melt slippage and relieve internal stresses. This action eliminates surface melt fracture and postpones the crit. shear rate for the onset of gross melt fracture to significantly higher values depending on resin type and the additive content. A possible mechanism explaining the effect of the additive on the processability of the resins is proposed. Practical wire coating and tubing extrusion studies with these resins were also carried out.

Ghanta, Venu G.; Riise, Brian L.; Denn, Morton M. (CORPORATE SOURCE Materials Sciences Division, Lawrence Berkeley Natl. Lab., Dep. Chem. Eng., Univ. California, Berkeley, Berkeley, CA 94720-1462, USA). SOURCE J. Rheol. (N. Y.), 43(2), 435-442 (English) 1999 American Institute of Physics. CODEN: JORHD2.

We have extruded a linear low-d. polyethylene through capillary dies fabricated from stainless steel and brass. We confirm a result first reported by Ramamurthy [Ramamurthy, A. V., "Wall Slip in Viscous Fluids and Influence of Materials of Construction," J. Rheol. 30, 337-357 (1986)]: sharkskin can be eliminated by the use of a brass die. We also find a substantially enhanced throughput from the brass die relative to the stainless-steel die at stresses in the range where sharkskin is obsd. with the latter. Finally, the large-pressure oscillations and periodic extrudate distortions obsd. in the slip-stick region with stainless steel are absent with brass, where the transition to the upper branch of the flow curve is more gradual.

Kim, Youn Cheol; Yang, Kyoung Sun; Choi, Chang-Hyun (CORPORATE SOURCE Research and Development Center, Samsung Chemical Group, Compounds & Application R & D Team, Taejon 305-380, S. Korea). SOURCE J. Appl. Polym. Sci., 70(11), 2187-2195 (English) 1998 John Wiley & Sons, Inc. CODEN: JAPNAB. ISSN:

Successive passes through an extruder can modify the melt morphol. of low-d. polyethylene (LDPE) by applying a shearing process. The major effects of shear modification are to decrease the elastic properties, as evidenced by the decrease in extrudate swell at the exit of a capillary and in melt viscosity at a low-frequency region. The effect of shear modification is also shown by the delay in the onset of melt fracture upon extrusion. The crit. shear stress resulted from extrudate appearance, and apparent discontinuity in the flow curve of LDPE shows a similar value with polypropylene rather than those of LLDPE and HDPE. The shearing histories experienced by these materials did not result in any measurable change in mol. wt., so that the chem. modification process such as degrdn. and crosslinking may be ruled out. These behaviors were also confirmed to the fact that the extrudate swell was fully reversible by annealing in a molten state. The effects of shear modification on rheol. properties could be explained by the changes in melt morphol. owing to the disentanglement of temporary couplings between long branches. Also, a redn. in melt elasticity by shear modification of LDPE can be used as an effective tool to improve the surface roughness of extrudates in the cable-making process.

Hong, Ye; Cooper-White, J. J.; Mackay, M. E.; Hawker, C. J.; Malmstrom, E.; Rehnberg, N. (CORPORATE SOURCE Department of Chemical Engineering, Materials Characterization and Processing Centre, The University of Queensland, Brisbane 4072, Australia). SOURCE J. Rheol. (N. Y.), 43(3), 781-793 (English) 1999 American Institute of Physics. CODEN: JORHD2. ISSN: 0148-6055. DOCUMENT TYPE: Journal CA

The use of hyperbranched polymers (HBPs) as a processing aid for linear low d. polyethylene (LLDPE) was investigated. Various generation (or pseudo-generation) HBPs were used which had either 16 carbon atom alkanes or a mixt. of 20/22 carbon atom alkanes on the end groups. In addn., the degree of end group substitution was studied. Blends of up to 10% HBP content were mixed via extrusion at 170 °C to produce 1 mm diam. fibers. Processability, surface appearance and the rheol. properties of the blends were evaluated. It was found the power requirement for extrusion was significantly decreased as a result of reduced blend viscosity, and also, the mass flow rate for a given extruder speed was greater than virgin LLDPE for all HBP blends. Melt fracture and sharkskin of the blends was successfully eliminated, and minimal preprocessing time was required for the effect to take place. Surface anal. using XPS and transmission electron microscope techniques were performed with both showing that the HBP had a preference to accumulate at the fiber surface. Rheol. expts. were similarly affected, therefore, the blend viscosity is really a composite of a HBP rich phase and a neat LLDPE phase. It is hypothesized that the HBP rich phase acted as a lubricating layer at the polymer/die wall interface. The HBP with a greater degree of end group substitution acted better as a processing/rheol. property aid. Blends of LLDPE and paraffin wax were also studied. The surface appearance of HBPs/LLDPE blends was superior to those blends mixed with paraffin wax, as was the extruder performance. The results suggest that HBPs, at trace levels (u500 ppm), may offer a no. of advantages when used as a processing aid for LLDPE.

Anon. (CORPORATE SOURCE UK). SOURCE Res. Discl. 418(Feb.), P174, No. 41802 (English) 1999 Kenneth Mason Publications Ltd. CODEN: RSDSBB. ISSN: 0374-4353.

Easy flow resins have many advantages as a processing aid and/or carrier resin for processing aids to improve dispersion and reduce the overall concn. of the fluorocarbon based polymer needed to eliminated melt fracture. Easy flow LLDPE resin was designed to process like high pressure low-d. polyethylene and processes at lower shear pressure and motor amperage and is less prone to melt at narrow die gaps.

Addcox, Jim H.; Giacoletto, Glen M. (CORPORATE SOURCE Chevron Chemical LLC, Orange, TX 77630, USA). SOURCE Polym., Laminations Coat. Conf., Volume 2, 927-939. TAPPI Press: Atlanta, Ga. (English) 1998. CODEN: 66XOA3. DOCUMENT

Fluorine-based processing aids are an effective means for improving the surface quality of polymer extrudates, esp. in LLDPE film applications. By reducing the shear-induced stresses which can cause melt fracture and die-lip build-up, processing aids have also allowed many film processors to increase the output of their equipment. Although their effects on extrusion processes are generally viewed as pos., the effects of processing aids on downstream film properties have been a historical concern. Many studies have been conducted which indicate that most com. available processing aids have little or no effect on surface-related film properties such as print adhesion and heat-seal integrity. In terms of heat-seal, these studies have focused primarily on the effects of fully quenched seals. In high-speed filling operations, such as vertical form and fill loading, the film processor must often rely on the hot-tack strength of the film to bear the wt. of the load until the seal has fully quenched. In this study, three different fluorine-based processing aids were evaluated in a monolayer LLDPE film application over a range of concns. The hot-tack performance of these films was not adversely affected by the processing aids.

Cobb, Daniel Christopher; Mercer, James Wilson, Jr. (CORPORATE SOURCE Eastman Chemical Company, USA). SOURCE U.S. US 6100320 A 8 Aug 2000, 5 pp. (English). (United States of America). CODEN: USXXAM. CLASS: ICM: C08K005-098. NCL: 524399000.

In a process for producing a profile by profile extrusion of a thermoplastic resin, a melt of the thermoplastic resin is extruded through a die to form the profile. The process is improved by utilizing a thermoplastic resin having a compn. of from about 99.95 to about 98.0 wt. percent amorphous or semicryst. polyester and from about 0.05 to about 2.0 wt. percent of a zinc salt of an org. acid. The improvement of the process is either by increasing speed or decreasing temp. of a profile extrusion process already operating at a max. speed and/or temp. with experiencing melt fracture. When melt fracture is present in the profile extrusion process, a method for reducing melt fracture in a profile is accomplished by combining from about 99.95 to about 98.0 wt. percent amorphous or semicryst. polyester and from about 0.05 to about 2.0 wt. percent of a zinc salt of an org. acid to form a melt, extruding the melt through an orifice of a die at a temp. and a speed to form an extruded article having a shape, and thereafter quenching the extruded article to form a profile.

AUTHOR(S) Inn, Y. W.; Fisher, R. J.; Shaw, M. T. (CORPORATE SOURCE Department of Chemical Engineering and Polymer Program Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136, USA). SOURCE Annu. Tech. Conf. - Soc. Plast. Eng., 57th(Vol. 1), 1280-1282 (English) 1999 Society of Plastics Engineers.

Rosenbaum, Eugene E.; Randa, Stuart K.; Hatzikiriakos, Savvas G.; Stewart, Charles W.; Henry, Donald L.; Buckmaster, Marlin (CORPORATE SOURCE Department of Chemical and Bio-Resource Engineering, The University of British Columbia, Vancouver, BC V6T-1Z4, Can.). SOURCE Polym. Eng. Sci., 40(1), 179-190 (English) 2000 Society of Plastics Engineers

The influence of a new processing additive (fine particles of boron nitride) on the processability of polyolefins and fluoropolymers in extrusion is studied. The equipment used includes an Instron capillary rheometer with two types of dies, namely capillary dies and special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer, and an extruder. Two metallocene polyethylenes and several Teflon fluoropolymers were tested using these two pieces of equipment. The additive had a significant effect on the extrudate appearance of polyethylene and fluoropolymer particularly in the crosshead dies. It was found to eliminate surface melt fracture and to postpone the crit. shear rate for the onset of gross melt fracture to significantly higher values depending on resin type, temp., and additive concn. (typically 0.005% to 0.5%). To explain the possible mechanism for the effect of the additive on the processability of the resins, rheol. measurements using both parallel-plate and sliding-plate rheometers were carried out. The rheol. of the resins did not seem to change significantly with the addn. of boron nitride except for the low-shear-rate (low-frequency) range, where the behavior of the filled resin was found to be similar to that of a crosslinked polymer or a phase-sepd. entangled blend. Practical wire coating and tubing extrusion studies for these resins were also carried out.

Shearer, Gifford; Tzoganakis, Costas (CORPORATE SOURCE Department of Chemical Engineering, University of Waterloo, Waterloo, ON, Can.). SOURCE Annu. Tech. Conf. - Soc. Plast. Eng., 57th(Vol. 1), 73-77 (English) 1999 Society of Plastics Engineers.

Polypropylene (PP) coated dies were used in an attempt to decrease the die pressure and eliminate surface melt fracture during the extrusion of linear low d. polyethylene (LLDPE). The investigated coatings were: controlled-rheol. PP, hydrosilylated PP, amorphous PP wax, and maleic anhydride grafted PP. Extrusion stability, die pressure, and extrudate appearance were used to compare the effectiveness of the different coatings.

AUTHOR(S) Yip, Franky; Rosenbaum, Eugene E.; Randa, Stuart K.; Hatzikiriakos, Savvas G.; Stewart, Charles W. (CORPORATE SOURCE Department of Chemical Engineering, The University of British Columbia, Vancouver, BC, Can.). SOURCE Annu. Tech. Conf. - Soc. Plast. Eng., 57th(Vol. 1), 1223-1227 (English) 1999 Society of Plastics Engineers. CODEN: ACPED4. ISSN: 0272-5223. DOCUMENT TYPE: Journal

The influence of a new processing additive (a compn. of fine particles of boron nitride) on the rheol. and processability of molten polymers is studied. The equipment used includes both an Instron capillary rheometer with special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer and a parallel-plate rheometer. A metallocene polyethylene and Teflon FEP with several types of boron nitride varying in particle size distribution are tested at various concn. levels. The additive with the finest particle size has the greatest influence in crosshead dies and tips. As a result, its use eliminates surface melt fracture and postpones the crit. shear rate for the onset of gross melt fracture to significantly higher values depending on the additive concn. The influence of the boron nitride type and its concn. on the polymer rheol. is also discussed. It is found that the activation energy for flow of Teflon FEP scales with the BN concn.

Woods, Susan S.; Pocius, Alphonsus V. (CORPORATE SOURCE Dyneon LLC, Oakdale, MN, USA). SOURCE TAPPI Polym., Laminations Coat. Conf., Volume 2, 1011-1039. TAPPI Press: Atlanta, Ga. (English) 1999. CODEN: 68GEA4.

Polyolefin plastomer films formulated with slip and antiblock were blown on a wide die gap with and without two Dynamar, i.e, Dynamar FX 9613 and Dynamar FX 5920A, polymer processing additives (PPAs). A wide die gap was used so that melt fracture-free film could be obtained with no PPA present for comparison purposes. The films were analyzed for the following properties: surface tension (on treated films), gloss, haze, clarity, transmittance, hot tack, heat seal, COF and block. In addn., the surface of films was examd. using ESCA (electron spectroscopy for chem. anal.) and SSIMS (static secondary ion mass spectrometry) to det. the surface chem. compn. PPAs when used at typical dose levels have essentially no effect on plastomer film surfaces or optical properties. Some detraction from haze was obsd. at high levels of PPA exceeding normal dose levels. The adhesion of coatings to these materials or of these materials to themselves would not be affected by the presence of the PPA additive.

AUTHOR(S) Eggen, Svein S. (CORPORATE SOURCE Borealis Research Centre, Stathelle 3960, Norway). SOURCE Annu. Trans. Nord. Rheol. Soc., 7, 57-62 (English) 1999 Nordic Rheology Society.