Die design for rigid PVC—the effect of die land length on extrudate swell

Rabinovitch, Elvira B.; Summers, James W.; Booth, Patrick C.

doi:10.1002/vnl.730140107

Cited by 4 publications

(3 citation statements)

References 8 publications

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“…Swell falls to a lower limit with increasing length of the parallel land region, as stresses due to extensional deformation in the upstream region of the die are able to relax. Studies of the effect of die length include references [65][66][67][68][69][70][71][72][73]. For slit extrusion of polystyrene at a wall shear rate of 240 s À1 [66], the swell ratio decreased from 4 for a zero length die to a lower asymptote of 2 as the parallel land length-to-gap ratio increased to about 30.…”

Section: Extrudate Swellmentioning

confidence: 99%

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Computer-aided design and optimization of profile extrusion dies for thermoplastics and rubber: a review

Pittman

2011

Proceedings of the Institution of Mechanical Engineers, Part E:

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A review is provided of issues and techniques in design and optimization of profile extrusion dies for thermoplastics and rubber, with particular emphasis on unplasticized polyvinyl chloride and rubber compounds. Traditional profile die design methods are contrasted with computer-based ones, with respect to efficiency and economic benefits. The main types of die construction are outlined. Physical phenomena relevant to the design and performance of dies are summarized, including: rheology and kinematics of the flow, wall slip, extrusion instabilities, residence time and degradation, extrudate swell, draw-down, and thermal effects. Approaches and strategies for die design are explained, including: flow balancing – with guidance from analytic flow results, the Avoid-Cross-Flow strategy, use of flow separators, and designing for extrudate swell. Published computer simulations of die flow used to assist with design are reviewed. Introducing automatic die design, the structure and elements of a computerized design optimization environment are set out. Key components and options within this are described, including: objective functions, constraints, design variables, optimization algorithms, design parameterization and flow domain meshing, and optimization strategies. Published implementations of computerized profile die design optimization are described. Automatic design optimization is compared with the work of a designer assisted by flow simulations in the industrial environment, showing how substantial reductions in demands on the designer's time are possible. The nature and potential of robust design is outlined, with techniques for its implementation. Conclusions are drawn as to the present state of the art in computer-assisted profile die design and optimization, and potential advances.

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Section: Extrudate Swellmentioning

confidence: 99%

“…It is decreased by addition of fillers and increased by processing aids that promote fusion [81]. Furthermore, uPVC swell is weakly influenced by die land length [65,67]. At a shear rate of 150 s À1 , capillary swell fell from 1.2 for a zero length die to 1.05 in dies of length greater than five diameters.…”

Section: Extrudate Swellmentioning

confidence: 99%

Computer-aided design and optimization of profile extrusion dies for thermoplastics and rubber: a review

Pittman

2011

Proceedings of the Institution of Mechanical Engineers, Part E:

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“…As a first step to improve color hold in vinyl siding which was already typically coextruded with a fairly UVtolerant vinyl capstock primarily accomplished with high TiO 2 levels [2], as much as 50% of the vinyl in the cap was replaced with a more weatherable nonvinyl polymer such as ASA. Eventually, as vinyl siding acceptance expanded throughout the United States.…”

Section: Introductionmentioning

confidence: 99%

Superior balance of weatherability and impact performance with acrylic‐capped vinyl siding

Szamborski

2007

Vinyl Additive Technology

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Vinyl siding, particularly in darker colors, has to be durable and be able to retain most of its original color when exposed outdoors. As the color palette for vinyl siding has been expanding and more and more colors are being offered to the homeowner, the need exists to improve color hold. A new acrylic capstock polymer, based on core‐shell technology, which can be coextruded onto vinyl siding, has been shown to provide excellent color retention, with good processability, impact and impact retention, and suitable gloss. The properties of this new capstock polymer are compared to other choices for capping vinyl siding. J. VINYL ADDIT. TECHNOL., 13:26–30, 2007. © 2007 Society of Plastics Engineers.

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Vinyl Chloride Polymers

Summers¹

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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PVC has a large sales volume, second only to polyethylene. Its high chlorine content provides it with a high level of combustion resistance for building products, electrical enclosures, and wire and cable insulation. PVC has a unique ability to be compounded with a wide variety of additives, making it possible to produce materials in a range from flexible elastomers (the first thermoplastic elastomers) to rigid compounds, materials that are weatherable such as for siding and windows, compounds that have stiff melts and little elastic recovery for outstanding dimensional control useful in profile extrusion, or low viscosity melts which compete effectively with ABS and PC/ABS in thin‐walled injection molding parts such as computer monitor housings. Some PVC properties are attributed to unique morphology. The polymer precipitates from its monomer and grows into primary particles, which are later the melt flow units. Fusion into larger structures and product strength are controlled by breakdown of the grains into primary particles, by choice of additives, by amount of melting (temperature), and by number of tie molecules (molecular weight). The main type of polymerization is the suspension process, with significant polymerization made by the mass, solution, microsuspension, and emulsion processes. In the suspension process, the polymerization takes place in droplets of monomer suspended in water. From an environmental viewpoint, PVC is over 50% chlorine and as a result, is one of the most energy‐efficient polymers. PVC is an inherent flame retardant, and acts as a marker, enabling automated equipment to sort PVC containers from other plastics in the waste stream. Vinyl is recycled by at least 170 recyclers in the United States and Canada and more than 3,500 communities accept vinyl products in their recycling programs. The analysis from 155 large‐scale, commercial incinerator facilities found no relationship between the chlorine content of waste nor the addition of PVC, and dioxin emissions from combustion processes. New requirements from the U.S. EPA make scrubbers mandatory on all incinerators and are necessary whether or not PVC is present in the waste feed.

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Die design for rigid PVC—the effect of die land length on extrudate swell

Cited by 4 publications

References 8 publications

Computer-aided design and optimization of profile extrusion dies for thermoplastics and rubber: a review

Computer-aided design and optimization of profile extrusion dies for thermoplastics and rubber: a review

Superior balance of weatherability and impact performance with acrylic‐capped vinyl siding

Vinyl Chloride Polymers

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