SPE Library

The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Conference Proceedings

SOLVING PROBLEMS WITH BIOBASED, SUSTAINABLE PLA AND RECYCLABILITY OF PET FOR HIGH-VALUE APPLICATIONS VIA SOLID-STATE SHEAR PULVERIZATION

Audrey Durin, Rudy Valette, Bruno Vergnes, Thierry Coupez, Chantal David, May 2010

Solid-state shear pulverization (SSSP) can lead to in situ mechanochemistry and enhanced dispersion relative to melt-state processes. SSSP of poly(ethylene terephthalate) (PET) results in low levels of branching and enhanced dispersion of heterogeneous nuclei, leading to increased melt viscosity and crystallizability, providing a solution to the problem of recycling PET for high-value applications. (PET undergoes molecular weight reduction during melt processing.) Adding 1 wt% microcrystalline cellulose to poly(lactic acid) (PLA) via SSSP can lead to major enhancements in crystallizability and materials with increased heat distortion temperature relative to neat PLA.

A FULL 3D SIMULATION FOR TWIN SCREW EXTRUSION BASED ON AN IMMERSION DOMAIN METHOD. APPLICATION TO MIXING ELEMENTS

Audrey Durin , Rudy Valette , Bruno Vergnes , Thierry Coupez, May 2010

A full 3D simulation software has been applied for characterizing the flow conditions in mixing processes (batch mixers, single and twin screw extruders, cokneaders…). The approach is based on an immersion domain approach and uses the Finite Element Method. In the present work, we studied the flow conditions of a Carreau-Yasuda fluid in a portion of twin screw extruder, constituted by different types of conveying elements and blocks of kneading discs. The influence of geometrical parameters (staggering angle, number of tips, disc thickness…) on the flow conditions (pressure and pressure gradients, flow patterns, mixing efficiency…) has been characterized and compared to previous studies from the literature.

STUDY ON CELLULAR STRUCTURE AND SKIN LAYER THICKNESS OF MICROCELLULAR INJECTION MOLDED PARTS USING NEWLY-DEVELOPED EQUIPMENT

Han-Xiong Huang , Jian-Kang Wang , Hong-Fei Xu, May 2010

Experiments of microcellular injection molded polystyrene parts were carried out on equipment newly developed in this lab. Three processing parameters including the nozzle temperature injection speed and shot size were investigated in terms of their effects on the cellular structure and skin layer thickness of microcellular injection molded parts. The results showed that finer and more uniform cell structure is formed at appropriate nozzle temperatures. Cell diameter decreases cell density increases and cellular structure uniformity improves with the increase of injection speed or shot size. Moreover increasing the injection speed leads to the decrease of the skin layer thickness. Shot size does not show significant influence on the skin layer thickness.

PVC FLOW STREAMS IDENTIFY ELONGATIONAL FLOW

Rajkumar Thiruvenkataswamy, Sung-hwan Yoon, Joey L. Mead, Carol M. F. Barry, May 2010

At Antec 2008, a new single screw compounder (SSE) was introduced with newly designed mixers along the screw. These mixing elements had spiral flutes with elongational mixing (SFEM). The Elongator [1], hereafter SFEM, demonstrated simple processing of RPVC powder with an increased output from the historic limit of 30 rpm to a faster speed of 180 rpm at only 174 ?øC, vented, starved or flood fed. There was no need for a vacuum hopper or crammer feeder with this simple screw design. At Antec 2009, continuing work was presented with mixing tests performed with the smaller SSE using a newly designed SFEM (hereafter SFEM-II). Two tests were performed with the RPVC powder, one using 0.5% color concentrate and the other wood flour. Elongation flow has been shown in single screws to compound to the 500 nanometer level [2]. This paper shows the elongational mixing in cross sections of a mixture of PVC and color on a screw that was stopped and cooled during operation. The boundaries of the flows are visible as well as the progression of mixing.

FACTORS INFLUENCING DIMENSIONS WHEN INJECTION MOLDING MICROFLUIDIC DEVICES

Rajkumar Thiruvenkataswamy , Sung-hwan Yoon , Joey L. Mead , Carol M. F. Barry, May 2010

To evaluate the ability to maintain the dimensions of the microfluidic channels during manufacturing polystyrene polycarbonate and PMMA were molded using electroformed nickel tooling. Melt and mold temperature flow direction (i.e. impingement and parallel flow) backing material for the tooling and vacuum venting were systematically varied to determine their effects on channel depths and widths. Replication of channel depths depended on melt viscosity and was enhanced by mold and melt temperature but replication of channel widths depended on cooling and the ability fill the channels. Impingement flow provided better replication of channels widths. Backing material and vacuum venting had no effect on replication.

FRACTURE TOUGHNESS TESTING (KIC) OF PE 4710 PIPE MATERIAL

Harvey Svetlik , Dale B. Edwards , Ahamed Shabeer, May 2010

Plane strain fracture toughness testing is rarely performed on ductile plastics such as polyethylene due to the inherent toughness of the material. In particular the newer bi-modal polyethylene materials such as PE 4710 are extremely tough and rarely are available in sizes to assure plane strain in the test specimen. In this study very large bars of PE 4710 were fabricated and tested per ASTM D5045 Standard Test. The test results Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials demonstrate the superior fracture resistance of the material as well as the difficulty in achieving brittle fractures in materials of this type.

COMPARISON STUDY OF N2 AND CO2 AS PHYSICAL BLOWING AGENTS FOR INJECTION FOAM MOLDED WOOD-FIBER PLASTIC COMPOSITE

Peter U. Jung, Yongrak Moon, C.B. Park, May 2010

Due to rising environmental concerns, the plastic industry has been seeking bio-plastics that can replace current plastics. Efforts are continuously being made to reduce weight and cost without a major compromise to required properties. Foaming can offer a plastic with significant weight reduction. There has been research to evaluate the effects of chemical blowing agents (CBAs) on wood-fiber plastic composites (WPC). Although physical blowing agents (PBAs) have a number of advantages, their effects on WPC have not been fully investigated. Therefore, this research utilizes N2 and CO2 to analyze their effects on the foaming and mechanical properties of injection foam molded WPCs.

THE ROLE OF MOLECULAR PARAMETERS OF PP IN THE SENSITIVITY TO SPECIFIC NUCLEATION

Lenka Chvátalová , Jana Výchop ová , Roman Cermák , Martin Obadal, May 2010

The efficiency of -nucleating agent (NU 100) in commercial isotactic polypropylenes (PP) differing in melt flow indexes (MFI) was analyzed. Polymorphic composition of neat PP and PP containing 0.01 and 0.03 wt.% of NU 100 was analyzed using wide-angle X-ray scattering and differential scanning calorimetry.Morphology was observed by polarized-light microscopy.MFI influenced the -phase formation only with 0.01 wt.% of NU 100: The step change of -phase content between PP with MFI 1 and 12 was observed. A significant effect of final temperature of heating on -phase formation in the samples was detected. PP containing 0.03 wt.% of NU 100 crystallized into -phase.

MODELING OF COUPLING BETWEEN SPECIFIC ENERGY AND VISCOSITY DURING TWIN SCREW EXTRUSION OF STARCHY PRODUCTS

Françoise Berzin , Ahmed Tara , Bruno Vergnes , Chantal David, May 2010

Starchy products are commonly transformed by twin screw extrusion, either for the manufacturing of food products (extrusion cooking of snacks or breakfast cereals, for example) or for the production of bio-based materials (bioplastics). During the extrusion process, starch is submitted to high shear rates and stresses which lead to a modification of its basic structure. As many properties of the extruded starch are directly connected to the molecular weight and its distribution, it is very important to be able to predict the changes experienced during the extrusion process. In order to model the transformation of starch during twin screw extrusion process, it is thus necessary to take into account the strong coupling between viscosity and thermomechanical treatment. It is the purpose of thepresent work. We have used the software Ludovic was developed ten years ago to calculate the flow of a polymer along a twin screw extruder. We have assumed that the degradation reaction (viscosity decrease) was linked to the specific energy received during the flow. We have compared extrusion cases with and without viscosity/energy coupling and we show that it is important to take it into account in order to correctly predict the parameters of the extrusion process (torque, energy, product temperature') and the starch transformation.??, which

AN INVESTIGATION OF THE EFFECT OF SCREW GEOMETRY ON MELTING IN A SINGLE-SCREW EXTRUDER

S. Azcarate, A. Herrero, J. Esmoris, R. Oñate, A. Cervera,, May 2010

Screw-freezing experiments in a single-screw extruder were conducted with screws having different compression ratios and compression rates for an ABS resin. Three-dimensional finite element simulations of the melting process in the compression section of the extruder were also performed for the compression ratios and compression rates used in the experiments. Even though some discrepancies existed between the numerical predictions and experimental data, the melting profiles predicted by the finite element simulations were in good agreement with the corresponding experimental data.

DEVELOPMENT OF PLASTIC DENTAL BRACKETS BY MICROINJECTION: MECHANICAL AND RHEOLOGICAL SIMULATION, PROTOTYPES PRODUCTION BY MICROMILLING AND PRODUCTION BY MICROINJECTION

S. Azcarate , A. Herrero , J. Esmoris , R. Oñate , A. Cervera, May 2010

Although plastic dental brackets are available on the market, they are all made out of plastic materials with poor mechanical properties. This project sought to develop plastic dental brackets with better mechanical properties than the metallic ones in order to enlarge the aesthetic treatment market. The project started by selecting the material, PSU from BASF, and then focused on prototype production by direct micro milling in order to check the design and mechanical properties experimentally. Once the design was tuned, rheological simulation took place to be produced by microinjection. A first micro mould was produced to check microinjection feasibility. The remaining micro moulds were produced and the first production series obtained. The product was patented and launched on the market.

SYTHESIS AND FOAMING OF WATER EXPANDABLE POLYSTYRENE-ACTIVATED CARBON COMPOSITES

Jintao Yang , Shu-Kai Yeh , Zhihua Guo , Zhiqi Cai , L. James Lee, May 2010

Water can act as a co-blowing agent for carbon dioxide (CO2) based polystyrene foaming. With the introduction of water into the foaming process it is possible to produce foams with ultra-lower density. Herein we report a modified method to prepare water expandable polystyrene (PS)ƒ??activated carbon (AC) composites using suspension polymerization of inverse emulsion. PS is hydrophobic and does not absorb any water. Thus a good water absorbent carrier such as activated carbon can be used to carry water in the foaming process. Activated carbon pre-saturated with water is introduced into the styrene monomer resulting in the formation of water-inoil inverse emulsion. Via suspension polymerization spherical water/activated carbon PS beads could be subsequently obtained. By the extrusion foaming process a PS/AC composite foam with ultra-low density (~0.03g/cc) is successfully produced.

EXTRUSION FOAMING OF CANCELLOUS POLYSTYRENE STRUCTURES

Raymond K.M. Chu, S. Lee, W. Ishaque, B. Zaman, P. Jung, Chul B. Park, May 2010

Foams of cancellous structures are versatile. They can be utilized as particulate filters, spill absorbent linens, tissue engineering scaffolds, and selective extraction membranes. This paper presents an investigation on the fabrication of cancellous polymeric structures with a foam extrusion process. Experiments were conducted on styrenic polymers with supercritical carbon dioxide as the foaming agent. To promote cell wall opening, the strategy of inhomogeneous domain was incorporated in the foaming process. Results showed that a higher foam porosity and more cancellous morphological structure were achieved through the finely dispersed secondary phase in high-impact polystyrene.

A STUDY OF EXTRUSION FOAMING BEHAVIOR OF RANDOM AND BLOCK POLYPROPYLENE COPOLYMER/CLAY NANOCOMPOSITES WITH USING CO2 AS A PHYSICAL BLOWING AGENT

Wentao Zhai, Richard E. K. Lee, T. Kuboki, Chul B. Park, May 2010

Due to the excellent mechanical properties and low material cost, polypropylene (PP) has obtained an increasing market share, up to 26.5% in 2015 according to the expectation, in the world. However, the usage of PP in polymeric foaming field is limited owe to its poor melt strength. Several kinds of commercial high-melt strength PP have been developed for foaming, but high material cost, about 1.8 times compared to the regular one, tends to increase the price of final foam products. How to offer an effective and economical attractive way in fabricating PP foam have attracted a wide attention nowadays. In this study, two linear PP resins, i.e., random copolymer (RPP) and block copolymer (BPP), with similar melt flow rate were selected. Their foaming behavior was investigated by using continuous extrusion foaming with CO2 as the physical blowing agent. The nanoclay was introduced with the aim to show its potential effect in preparation polymeric foams with high expansion ratio and well defined cell structure. The difference in foaming behavior between RPP and BPP was also investigated.

A STUDY OF EXTRUSION FOAMING BEHAVIOR OF RANDOM AND BLOCK POLYPROPYLENE COPOLYMER/CLAY NANOCOMPOSITES WITH USING CO2 AS A PHYSICAL BLOWING AGENT

Wentao Zhai , Richard E. K. Lee , T. Kuboki , Chul B. Park, May 2010

Due to the excellent mechanical properties and low material cost polypropylene (PP) has obtained an increasing market share up to 26.5% in 2015 according to the expectation in the world. However the usage of PP in polymeric foaming field is limited owe to its poor melt strength. Several kinds of commercial high-melt strength PP have been developed for foaming but high material cost about 1.8 times compared to the regular one tends to increase the price of final foam products. How to offer an effective and economical attractive way in fabricating PP foam have attracted a wide attention nowadays. In this study two linear PP resins i.e. random copolymer (RPP) and block copolymer (BPP) with similar melt flow rate were selected. Their foaming behavior was investigated by using continuous extrusion foaming with CO2 as the physical blowing agent. The nanoclay was introduced with the aim to show its potential effect in preparation polymeric foams with high expansion ratio and welldefined cell structure. The difference in foaming behavior between RPP and BPP was also investigated.

A STUDY OF EXTRUSION FOAMING BEHAVIOR OF RANDOM AND BLOCK POLYPROPYLENE COPOLYMER/CLAY NANOCOMPOSITES WITH USING CO2 AS A PHYSICAL BLOWING AGENT

Wentao Zhai , Richard E. K. Lee , T. Kuboki , Chul B. Park, May 2010

Due to the excellent mechanical properties and low material cost, polypropylene (PP) has obtained an increasing market share, up to 26.5% in 2015 according to the expectation, in the world. However, the usage of PP in polymeric foaming field is limited owe to its poor melt strength. Several kinds of commercial high-melt strength PP have been developed for foaming, but high material cost, about 1.8 times compared to the regular one, tends to increase the price of final foam products. How to offer an effective and economical attractive way in fabricating PP foam have attracted a wide attention nowadays. In this study, two linear PP resins, i.e., random copolymer (RPP) and block copolymer (BPP), with similar melt flow rate were selected. Their foaming behavior was investigated by using continuous extrusion foaming with CO2 as the physical blowing agent. The nanoclay was introduced with the aim to show its potential effect in preparation polymeric foams with high expansion ratio and welldefined cell structure. The difference in foaming behavior between RPP and BPP was also investigated.

BLISTERING IN POLYESTER SWIMMING POOL GELCOATS

Jan Spoormaker, May 2010

Blistering of polyester boats and swimming pools is a serious problem and this is mainly due to voids after the so-called gelcoat. Water diffuses through the gelcoat and fills the voids with water. The water can react with the polyester or with remainders of the components that react to obtain unsaturated polyester. The water soluble reaction products cause osmosis and the blister grows till it ruptures. Results from literature searches about the degradation reactions are presented. A court case about blistering of a swimming pool after 2.5 years will be used as an example. During this court case it was learned that an alleged party can try to use allegations that are not in line with laws from nature.

ON-LINE MONITORING OF POLYMER BLEND COMPOSITION BY EMISSION FT-IR SPECTROSCOPY

Jan Spoormaker, H. Schouenberg, May 2010

A FT-IR spectrometer is modified to collect the infrared radiation from the molten extrudate in a polymer blend compounding operation and the IR spectra are analyzed to quantify the blend composition on-line. PLS models are calibrated and validated using the spectra from a set of known blends and blend compositions are predicted via the PLS model from the emission IR spectroscopy acquired instantaneously on the extrudate strands. The chemical compositions of three types of polymer blends during compounding on a twin-screw extruder are measured and monitored in this way. This information can be used for on-line process monitoring and fault diagnosis as well as verification of extrusion models.

MOLD COST PRICE CALCULATIONS

Jan Spoormaker , H. Schouenberg, May 2010

The calculation of the cost price of injection moulds is based on experience with costs of previous molds. The widely used system of Maillard attributes 'points' to the complexity of the cavities, mould base and the number of cavities. A suitable computer program is CALCMASTER and it accounts for: Manufacturing hours for the cavities Manufacturing hours for the mould base Total number of toolmaker hours Total costs for hot runners Costs for injection trials, follow-up, price at mould acceptance. It also calculates: Injection time, Injection pressure and clamping force requirement. Theoretical cooling time, actual cooling time, cycle time, maximum holding time.

QUASI-SIMULTANEOUS LASER BEAM WELDING OF POLYMERS IN CLOSED LOOP

Wolfgang Horn, May 2010

Polymer welding with lasers is getting a state-of-the-art tool in medical device manufacturing and automotive production. Most commonly used are contour welding and quasi-simultaneous welding. An advantage of contour welding is the availability of closed-loop pyrometercontrolled processing optics. On-axis sensors are used for measuring the part's temperature. The pyrometer controller allows the storage of process data for documentation and quality analysis. The new optics developed combine the benefit of contour welding with the speed and addressability of quasi-simultaneous welding. Possibilities and limits of quasi-simultaneous closed-loop welding will be discussed with examples of industrial applications.