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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Analytical Solutions of Nonlinear Constitutive Equations for Large Amplitude Oscillatory Shear (LAOS) Flow
Nonlinear viscoelastic models have been studies to elucidate the nonlinear behavior of viscoelastic materials. It is axiomatic that the analytical solutions of these constitutive equations are helpful to investigate various viscoelastic flows. For this reason, studies on calculating the analytical solutions of viscoelastic models have been spotlighted. However, various studies rely on power series approximations and it cannot overcome the inherent limitation of convergence radius. In this study, new approach is suggested to calculate analytical solutions of the Giesekus model. This approach provides systematic way to calculate not only shear stress but also normal stress under large amplitude oscillatory shear (LAOS) flow.
Properties of Poly(Ethylene Glycol) Methyl Ether Acrylategrafted Polylactide
Polyethylene glycol (PEG) is known to plasticize PLA but can exhibit migration over time. In order to reduce migration, reactive extrusion was used to chemically graft polylactide (PLA) with low molecular weight poly(ethylene glycol) methyl ether acrylate (APEG). APEG was added in various concentrations (0, 15 and 30 wt%) in the presence of an organic peroxide as a radical initiator. The covalent grafting of APEG on the PLA was evidenced by ATR-FTIR, 1H NMR. The physical effects of APEG in terms of thermal and flow properties were also investigated. The melt-state viscoelastic properties were characterized by oscillatory shear measurements. The glass transition temperature of the modified PLA was measured using differential scanning calorimetry. As expected, storage modulus decreased with APEG content and the glass transition temperature of the APEG-modified PLA was decreased by approximately 14°C compared to that of pure PLA.
In-Situ-Pultrusion – Structural Thermoplastic FRP-Parts
Fiber reinforced plastics, produced by In-Situ-Pultrusion are supposed to be used as local reinforcement of injection molded plastic parts. For this purpose, the pultruded parts are overmolded after being inserted into the injection mold. From process technologies reasons, the parts made by In-Situ-Pultrusion consist of cast Polyamide 6 (PA6). This cast PA6 differs from standard injection molding PA6. In previous studies, it was shown that a good bonding between the partners can be reached. In this work, a new bending girder made of PA6GF30 and In-Situ-pultruded PA6 is presented. Some mechanical properties were tested and compared with an equal bending girder, made of pure PA6GF30.
Interfacial Fracture Behavior of Injection Molded Parts
The formation of interfaces cannot be avoided in joining processes of thermoplastics. Generated by injection molding, they could be mainly divided into “cold” and “hot” interfaces. Cold interfaces occur during assembly injection molding (AIM) and “hot” interfaces or well known as weld lines represents the meeting of two melt streams. A new tensile test coupled with transmitted light microscope (TLM) was developed to classify the interfaces in terms of morphology and strength and analyze the failure behavior of thin sections. The objective is to improve the injection molding process by understanding the failure behavior.
Evaluation of Consumption Process on Antioxidants in Polyethylene by Chemiluminescence Measurement Method
In recent years, plastic pipes have been increasingly used for hot water supplies and heating systems and these require materials with long-term durability. In this paper, we report the preparation of polyethylene samples containing different amounts of antioxidants. Furthermore, we conducted accelerated degradation tests on these samples, and we evaluated the degradation of the polyethylene samples by chemiluminescence. We found that non-isothermal chemiluminescence measurements are more suitable for both the qualitative monitoring of the deactivation of antioxidants and the degradation of polyethylene resin samples as compared to isothermal measurements. The process of antioxidant consumption is discussed on the basis of the chemiluminescence measurements.
Non-Destructive Testing of Composites by Robot Supported Aircoupled Ultrasound
Air-coupled ultrasound is used as a non-destructive testing method for fiber reinforced plastics. By using reemission measurements only one sided access is needed. In order to make a complete scanning of components with a curved surface, a six-axis industrial robot is used. The problem here is to relate each ultrasonic measurement point to the right point on the examined part. In this work, two different procedures are studied and presented with several examples to solve this problem. One possibility is to determine the position by knowing the exact velocity of the robot arm. In the other method, the position will be sent from the robot system to the ultrasound system via incremental displacement signals. To validate the method, multiaxial curved components were investigated, like a carbon fiber car roof with impact damages.
Non-destructive Testing of CFR-Tapes with Thermoplastic Matrix using Air-coupled Ultrasound
For analysis of CFR-Tapes with thermoplastic matrix, air-coupled ultrasound is evaluated as a non-destructive testing method for detecting material defects, mechanical defects and incorrect fiber volume ratio. The inspection performance is determined by means of specially prepared specimen and applying further investigation based on Matlab. It is shown that air-coupled ultrasound testing is not only capable of detecting a variety of defects, but has the potential of being applied as an inline testing system for the production of CFR-Tapes.
Foam Injection Molding of Polylactide with in-Situ Fibrillated Polytetrafluoroethylene
Manufacturing polymeric foams with high cell densities with injection molding is of great interest to industry, primarily because of the flexibility and costeffectiveness of the technology. Yet, there is still limited research work on foam injection molding of polylactide (PLA), an emerging bio-derived bio-degradable thermoplastic. The manufacture of PLA foam of high cell density and void fraction with injection molding remains challenging due the low melt-strength property of the resin. In this work, we examined processing of PLA foams with in-situ fibrillated polytetrafluoroethylene (PTFE) through injection molding. The prepared PLA/PTFE foams possessed void fractions of 50% and above.
Tensile Properties Modification of Ductile Polyoxymethylene/ Poly (Lactic Acid) Blend by Annealing Technique
This research aimed to improve tensile property of polyoxymethylene/poly (lactic acid) blend (POM/PLA) by annealing process. POM/PLA at ratio of 60/40 was injection molded to dumbell specimens. The blend was annealed at 80 C and 100 °C for 10-30 min. The effect of annealing on crystallinity, mechanical performance and fracture behavior was investigated. Crystallinity of PLA in the blend increased with increasing annealing times, which resulted in the increment of tensile strength and tensile modulus of POM/PLA blend. However, higher crystallinity of PLA in the blends after annealing yielded higher notch sensitivity and lower fracture toughness as compared to unannealed blend. The optimum condition of POM/PLA (60/40) was found at annealing temperature of 80 °C for 10 min, which obtained good in tensile strength and tensile modulus of the blend. It can be noted that notch sensitivity factor of neat polymer was improved in unannealed POM/PLA blend.
Polystyrene Foam Insulation: Implementation of Alternate Sustainable Flame Retardant
Sustainable solutions are being increasingly demanded in the construction product market place. Polystyrene insulation is an increasingly important component of green construction. The benefits of insulation in residential and commercial buildings include lower energy consumptions, improved thermal comfort, reductions in the first costs of the heating and cooling equipment and reductions in CO2 emissions from the burning of fossil fuels across the United States.
As with all foam insulations, polystyrene foam insulation is combustible and must comply with stringent building and fire codes, which have been in place since 1976. The basic requirement in codes is a flame spread index of 75 or less and a smoke developed index of 450 or less when tested in accordance with ASTM E84, in addition to separation of the foam insulation from building occupants through use of a thermal barrier, typically ½” gypsum board. Additional requirements are in place depending upon the particular application.
Like many other building products – from electrical wires to structural and decorative wood products to paint – foam insulation uses flame retardants to protect people and property from the hazards of fire. Flame retardants used in foam insulation meet current regulations and their history of safe use is supported by scientific research.1 Manufacturers are committed to product safety and the effectiveness of flame retardants, and support research and development efforts to continually advance and improve these materials.
A recent announcement by the Design for the Environment program of the U.S. EPA detailed a suitable polymeric flame retardant for use in polystyrene foam insulation. The chemistry is a brominated polymeric flame retardant to replace Hexabromocyclododecane (HBCD)2. HBCD has recently been listed as a persistent organic pollutant (POP) under the UNEP Stockholm convention and is on the Authorisation List (Annex XIV) under the European Union REACH (Regi
Flow of Molten Plastics: Puzzles and Problems
When high-molecular weight polyolefins and vinyl polymers are melted and formed into commercial products, the melts show themselves to be not just viscous liquids but complex fluids that exhibit a range of peculiar flow behaviors that cause problems for processors. Extrudate swell, shark skin, and wall slip are among the phenomena that complicate life for the plastics engineer. These arise from the elasticity of melts, their very high viscosities and the large normal stress differences generated in shear. Normal stress differences generate flow in a direction orthogonal to the principal flow and are the cause of the well-known rod-climbing or Weissenberg effect, which is shown in Fig. 1 in a polymer solution. It has also been observed in molten polymers.
Multicomponent Injection Molding of Thermoplastics and Liquid Silicone Rubber (LSR) – Either Cured by Heat or UV Light
For processing thermally curing liquid silicone rubber (LSR) as well as UV light curing LSR for multicomponent injection molding with thermoplastics in an comparable way a processing center was designed and set into operation.
For the production of the multicomponent specimens a modular tool was designed. In there a thermoplastic plate gets molded on the one side, then gets transferred automatically by a robot system and gets overmolded by the silicone on the other side. The complete silicone side of the tool is easily changeable from a heated cavity, which is more or less state of the art, to a transparent cavity, wherein the UV LSR gets cured by according LEDs.
In first studies tests have been carried out concerning the adhesion between several thermoplastic materials and different LSR types, cured by heat as well as by UV light. The adhesion has been tested according to VDI 2019.
The used injection molding technique makes an intermediate treatment like surface activation of the thermoplastic plate possible before it gets overmolded. Therefore exemplarily different surface treatments and their effects on the adhesion strength of the material composite were evaluated.
New Materials Bring New Testing Challenges
Polymers have been utilized in automotive applications for many years. However as OEM’s strive for affordable lightweight vehicles, suppliers are discovering what may have been acceptable yesterday is today’s opportunity for improvement. One such opportunity involves utilizing new materials to differentiate automotive interiors. Faced with the challenge of setting new trends, interior design engineers must also satisfy customer expectations that the materials used will withstand the rigors of everyday use. This paper reviews the recent development of piano-black; high-gloss components that eliminate the need for secondary processes such as painting, and how one OEM discovered during field tests their initial screening tests were inadequate. Scratch and mar testing solutions are discussed for a better understanding of how to compare and select the finishing option that offers the most durable outcome.
Thermal and Time-Dependent Rheological Stability Behavior of Polyacrylonitrile with Various Plasticizers
The feasibility of melt spinning polyacrylonitrile (PAN) with plasticizers has been investigated for decades but it is still not been commercialized yet. In this paper, the thermal and time-dependent rheological stability behavior of PAN with various plasticizers is reported. The thermal behavior experiments show that the plasticizers are able to sufficiently decrease the melt temperature of PAN which make the melt spinning process feasible. The timedependent rheological stability experiments show that PAN could hold its viscosity stable without significant degradation and crosslinking for a sufficient period of time below 180?.
Applied Rheology for Understanding Flow Instabilities in Polymer Processing
Due to the fact that polymer melts behaves as non- Newtonian viscoelastic fluids, their flow behavior is rather complex and leads to number of flow phenomena which have negative impact on their processing and final product properties [1-19]. The polymer melt elasticity, high shear viscosity, extensional viscosity and its tendency to slip at the solid surfaces causes the flow destabilization. Typical flow instabilities occurring during polymer melt flows are die drool [1-2, 11-12, 15-18], neck-in [3, 5, 7, 15, 17], film blowing instabilities [3, 5, 14, 15-17] and interfacial instabilities in coextrusion [4, 5, 6, 10, 15, 17]. In this work, it is demonstrated how the polymer melt rheology and modeling of polymer processing can be used to understand and minimize the above mentioned flow instabilities occuring in extrusion and coextrusion technologies.
Slow Crack Growth Fracture Resistance Parameter Evaluation for Parent and Joint HDPE Materials
Slow crack growth (SCG) under sustained loads (pressure and axial loads) is one of the limiting failure modes that affect the long term performance of High Density Polyethylene (HDPE) pressure piping identified for use in replacement of existing steel piping for Class II applications in nuclear power plants. Several different tests have shown  the much lower time to failure of joint HDPE material when compared to the parent HDPE material, indicative of the much lower SCG resistance of the joint HDPE material. Hence, the integrity of the HDPE pipe joints and the critical flaw size evaluation is an area of increased focus for the nuclear industry and regulators, and the plastic pipes industry. Towards this end, task and working groups have been formed within the ASME Boiler and Pressure Vessel Code Committee Sections XI, IX, and III to address the needs for the HDPE piping evaluations in nuclear safety related applications. This current study is a comparison of the resistance to the SCG exhibited by the parent and fusion HDPE materials in the SENT specimen testing. Analysis of the crack growth resistance parameter through crack-mouth-opening-displacement (CMOD), and crack-opening-angle (COA) revealed a marked difference between the parent and fusion HDPE material. The experimental analysis also revealed a similar crack growth in normalized time indicative of the same constraint in the experimental specimen, but differing fracture energy in the parent HDPE material versus the butt-fusion joint material. The findings are in line with the large difference observed in the time to failure between the parent and fusion HDPE materials from creep tests at constant load.
Microinjection Molding: Influence of Molding Parameters on the Electrical Conductivity of Polypropylene Filled with Multi-Walled Carbon Nanotubes
Polypropylene (PP) composite with 10 wt% multi-walled carbon nanotubes (CNT) was prepared by melt dilution and then subjected to microinjection molding (?IM) process. A mold with a three-step configuration along the flow direction was adopted. The influence of actual injection molding parameters on the electrical conductivity of the microparts was evaluated by design of experiments (DOE) method. The distribution of maximum shear rates within the microparts was simulated via Autodesk Moldflow Insight, and the distribution of CNT along the flow direction was examined by scanning electron microscopy (SEM). Results indicated that the distribution of overall maximum shear rates follows an order of thin section>middle section>thick section, in harmony with the state of dispersion of CNT within the micro-components.
Improving the Mechanical Properties and Flame Retardancy of Multilayered PP Foam/Films via the Introduction of Flame Retardants
In this work we improve the mechanical properbities and flame retardancy of polypropylene (PP) foam/films produced by continuous multi-layered co-extrusion.Two different types of PP were used and named as PP1 and PP2. The nitrogen/phosphorous based flame retardant (FR) particles play the dual role of nucleating agent and flame retardant. FR particles were used to fabricate PP-FR composites. To investigate the effect of FR on PP crystallization and rheology, DSC thermograms, small amplitude oscillatory shear (SAOS), transient extensional viscosity were measured on both PP1 and PP2 system. FR particles played role of a nucleating agent for both PP1 and PP2 system. PP2 system has a 4x higher zero shear viscosity than PP1, while PP1 system showed much stronger strain-hardening than PP2. PP1 foam/ PP2 film structures were fabricated with different FR content. Both neat PP1 foam/PP2 film and PP1 foam/PP2 film-20%FR have good 16 layered film/foam structures and well-defined ellipsoidal shape bubble cells. The compressive modulus of PP1 foam/ PP2 film samples is 5-6 times higher than that of PP1 foam samples. Compressive strain of PP1 foam/ PP2 film samples is 2-3 times higher than one of PP1 foam samples. PP1 foam/ PP2 films showed excellent flame retardancy.
Properties of Melt Blended Chitin Nanowhisker-Polypropylene Composites
Chitin is a well-known biopolymer that can be extracted from crustacean shells and inherently has good mechanical properties. This paper focuses on using chitin nanowhiskers as a filler to improve the properties of neat polypropylene. Melt blended chitin nanowhisker polypropylene composites with chitin nanowhisker loadings ranging from 2 to 10 wt% was used for analysis. A combination of thermal, barrier, and mechanical properties were examined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), water vapor transmission test, and tensile test respectively. It was observed that the chitin nanowhisker helped improve thermal stability and crystallization. Additionally, an improvement of about 20% and 17% in elastic modulus and ultimate tensile strength respectively was observed at 5 wt% chitin nanowhisker loading. Lastly, a 258% improvement in water vapor resistance was displayed for the 2 wt% chitin nanowhisker loading. Results from the study showed that chitin nanowhisker is a suitable biodegradable filler material for polypropylene to strengthen its thermal, barrier, and mechanical properties.
Extensional Mixing Elements for Twin-Screw Extrusion: Effectiveness at Dispersive Mixing Operations in Composites
The extensional mixing element for twin-screw extrusion was applied to the melt mixing of two different polypropylene/carbon nanofiller systems and compared to a standard shear kneading block in an effort to improve the state of dispersive mixing of the operation. It was concluded that there was a qualitative and quantitative difference in microscale dispersion for both carbon nanotubes and graphene nanosheets when implementing the extensional mixing element, as evidenced by the optical microscopy images and subsequent image analysis. However, the composites exhibited minimal differences in rheological or electrical percolation, indicating that the reducing the initial agglomerate size is only a small part of effective composite production.
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