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.
The SPE Library is just one of the great benefits of being an SPE member! Are you taking advantage of all of your SPE Benefits?
= Members Only |
Categories
|
Conference Proceedings
Investigation of the Chemical Resistance and the Material Aging Conditions of Polyethylene for Pipe Applications
The chemical resistance of polyethylene (PE) for pipe applications was investigated with special regard to physical and chemical material aging. Therefore, tensile tests were conducted on films which were exposed to two different aggressive media for different predefined periods of time and at two different temperatures as well as on films which were not exposed to the media. The impact of the media on the Young´s modulus E, the stress at yield σy, the strain at yield εy and the strain at failure εf were studied. Potentially physical or chemical material aging was investigated by the degree of crystallization, the Oxidation Induction Time (OIT) and via Infrared (IR)-spectroscopy.
IMPRESS | an innovative pilot injection-compression moulding platform for the production of micro-nanostructures on plastic parts
IMPRESS targets the development of a technological injection moulding platform for serial production of plastic components incorporating micro or nano scale functional features. The platform is based on most advanced facilities divided in three modules:
- tool manufacturing | involving different technologies of micro- nano direct manufacturing | from top-down to bottom-up such as self-assembling,
- injection moulding | including equipments fitted with innovative hardware technologies to improve replication quality and capability,
- intelligence | dedicated to advanced process control and online metrology integration.
Beside this large panel of facilities | three case studies will be presented for biology | medical and energy applications.
We present the main results obtained during the first year of the project.
Multi-objective Optimization Strategy For The Design Of Injection Mold Cooling System
The manufacturing of thermoplastics parts needs a cooling phase to give the shape to the part. In injection molding | cooling can represent more than 70 % of the total cycle time. This is the reason why cooling channels have to be designed with great care in order to meet quality with efficiency requirements. In this paper | we propose a methodology to optimize the geometry parameters and coolant temperatures of the channels based on the use of modeFRONTIER® software combined with the injection molding simulation software MOLDFLOW®. Multi-objective optimisation will be carried out with criterions based on quality and cycle time minimization.
THE RIGHT CHOICE - NATURAL AND ACCELERATED WEATHERING TEST METHODS COMPARED
Weathering and light exposure are important causes of damage to coatings | plastics | inks | and other organic materials. This damage includes gloss loss | fading | yellowing | cracking | peeling | embrittlement | loss of tensile strength | and delamination. For many manufacturers | it is crucial to formulate products that can withstand weathering and light exposure. Accelerated weathering and light stability testers are widely used for research and development | quality control | and material certification. However | the importance of outdoor testing cannot be overlooked.
Accelerated testers provide fast and reproducible results. The most frequently used accelerated weathering testers are the fluorescent UV accelerated weathering tester (ISO 4802-3 | ASTM G154) and the xenon arc test chamber (ISO 4892-2 | ASTM G155). In recent years | low cost and easy-to-use testers have been developed.
This paper compares two accelerated weathering test methods: fluorescent ultraviolet and xenon arc. The paper will describe the strengths and limitations for both techniques due to: simulation of the forces of weathering | including sunlight | temperature and moisture | mounting of test specimens | control of test parameters | and operational considerations.
MICROSCOPIC EXAMINATION OF A HOT WORKING TOOL USED FOR PLASTIC INJECTION
The failure of a mould-part used for hot-forming is investigated. The die | made from AISI H13 steel was intended for the production of plastic cups. The mould-part exhibited a | single uniform crack through thickness | after five millions working-cycles | whereas it’s predicted working life was ten millions cycles.
Data were collected regarding the material selection | manufacture and operational history. The die was optically inspected. Hardness measurements were carried out and chemical analysis was performed. Detailed optical and scanning electron microscopy observations suggest the type of failure and the factors that led to it.
PRELIMINARY FAILURE EXAMINATION OF A TOOL USED IN TYRE WASTE
RECYCLING - CASE STUDY
Tyres consist of synthetic rubber | metals and linen.
Tyre waste decomposes after hundreds of years | and its
presence is detrimental for the environment. Standing
water | trapped into tires may be a permanent pollution
source | while tyre waste next to a forest increases the
possibility of fire. European legislation imposes the
recycling of tyre waste | which includes the following
three steps: shredding in strips | cutting strips in small
pieces | and powder production from the pieces. At the
last stage magnets remove the metallic pieces | while
centrifugal screens remove the linen. Metals are sold to
the steel industry as scrap | linen is used in limekiln as a
combustion material and the rubber flakes are used in
numerous applications (e.g. road surface construction,
concrete additives | mouse pads | etc.).
CORRELATION BETWEEN DIFFERENT MICRO-STRUCTURAL PARAMETERS
WITH PHYSICAL/MECHANICAL PROPERTIES OF POLYETHYLENE BLOWN
FILMS
A wide range of PE materials | including LLDPE,
HDPEs and LDPE were used for preparation of the blown
films. By changing processing conditions | different
structures for these blown films were produced and their
structural parameters investigated. Establishing
fundamental /structural model between structural
parameters and tensile modulus of blown films was the
objective of this work. A model for the tensile modulus
was proposed and correlated to some structural
parameters including crystallinity | orientation factors for
crystalline c-axis and amorphous phase | lamellar
thickness and crystal size. The measured modulus and
calculated one were compared and a reasonable
agreement was found between them.
FLEXURAL PROPERTIES AND FAILURE MECHANISM ASSESSMENT FOR
ADDITIVE MANUFACTURED LOM BARS ON DIFFERENT BUILDING
ORIENTATIONS
Plastic Laminated Object Manufacturing has not been
assessed from the flexural properties point of view. The
deflection range in parts manufactured by this technique is
wider than in parts fabricated by other additive
manufacturing methods like SLS or FDM. This fact has
increased the interest on the final application of these parts
rather than restricted to Rapid Prototyping applications. In
this study it will be compared the impact of building
orientation and geometric features of parts over the
flexural properties. Through optical observation it will be
studied the failure mechanism
SEQUENTIAL INJECTION MOLDING: DESIGN CONSIDERATIONS
New injection processes have been developed last decades, improving the designer freedom in order to launch attractive functionalities. All these procedures should be carefully analysed before to decide their use, because it is necessary to understand their natural restrictions, cost and operation requirements and rheological implications in the tools construction. This contribution presents a wide study made in the T.I.I.P., research group from the University of Zaragoza, which gives simulation results and experimental values about sequential injection moulding, and some practical considerations for designers and toolmakers, in order to get successfully results.
KINETCIS AND CHEMICAL REACTIONS OF ACETALDEHYDE STRIPPING PROCESS IN POLY(ETHYLENE TEREPHTHALATE) RESIN
The Kinetics of acetaldehyde (AA) stripping from PET pellets were determined at different temperatures, along with the determination of the residual concentrations of other less volatile compounds such as 2-methyl-1,3-dioxolane (2MD). The rate constants for the polymerization and AA diffusivity coefficients were determined at different temperatures of air stripping of PET. The air stripping of AA from PET is shown to involve chemical reactions and physical changes including polymerization, diffusion and generation of AA, 2MD, EG and water. This paper discusses the mechanisms of the chemical reactions and the formation of the by-products. The techniques used to elucidate the mechanism include gas chromatography (GC), intrinsic viscosity (IV), and density.
FEED ENHANCEMENT TECHNOLOGY FOR LOW BULK DENSITY MATERIAL
INTO CO-ROTATING TWIN-SCREW COMPOUNDING EXTRUDERS
Effectively feeding low bulk density material into a
co-rotating twin-screw extruder has always been a
challenge. However with the introduction of even finer
particle size fillers (sub-micron in some cases) as well as
new generations of polymer reactor resins, the issue has
become even more problematic. Additionally as bulk
density decreases, the materials tend to fluidize more
easily. Fluidization lowers the “effective” bulk density
even further and exacerbates feeding issues. Typical unit
operations within the compounding process where
material is more susceptible to fluidization are: transfer
from storage vessel to feeders, from feeder to twin-screw
extruder and within the feed zone conveying section of the
twin-screw extruder. While there are methods to minimize
the potential for fluidization such as dense phase
conveying from storage to feeder, minimization of the
feeder height above the extruder feed opening,
incorporating a vent into the feed hopper, extending the
length of the conveying zone in the extruder feed section,
the process eventually reaches a feed volume limitation,
which more often than not is well below an economically
viable production rate. This paper will review a new Feed
Enhancement Technology (FET) that provides significant
improvement for the introduction of fine particle / low
bulk density materials into the extruder.
Co-rotating Fully Intermeshing Twin-screw Compounding Extruders Technology:
Advancements for Improved Performance and Productivity
The co-rotating fully intermeshing twin-screw
extruder is the primary production unit for compounding
of polymer based materials. It also has had a long term
presence in processing material in the chemical and food
industry and more recently in pharmaceuticals. While this
equipment celebrated its 50th anniversary several years
ago and might be considered a “mature” technology, it has
not experienced a decline in new developments as might
be expected, but rather a significant number of
advancements continue to evolve. This paper will
highlight several significant developments of the past 10
to 15 years. These are the implementation of high torque
(power) designs, the use of increased rpm in conjunction
with high torque for improved operating flexibility and
productivity, and finally a technology breakthrough for
feeding difficult to handle low bulk density materials.
COMPUTATIONAL ANALYSIS AND DESIGN OF SINGLE SCREW EXTRUDERS
HAVING SCREWS OF COMPLEX GEOMETRY WITH MIXING ELEMENTS
The methodology is based on some conventional
models for flow in the hopper, solids bed and melting
zone. In the melt pumping zone the Hele – Shaw
approximation is applied, which describes spreading flow
in two dimensions. The momentum and energy equations
are solved layer – by – layer starting from the barrel wall.
This methodology enables significant reduction of
computer time required for simulation of extruders with
complex screw geometry, over the fully 3D approach.
Good agreement was obtained with some available
experimental data and further evaluations of predictive
capabilities are currently underway.
PROCESSING AND PROPERTIES OF BIOABSORBABLE PLLA-HA COMPOSITES
Orthopedic procedures often require repair materials
that can carry large loads without excessive deformation or
failure. To this end, we designed composites using two
biocompatible/bioabsorbable polymers, poly(L-lactic acid)
(PLLA) and polycaprolactone (PCL). The latter was filled
with nano-needles of hydroxyapatite (HA), while the
PLLA was used in long-fiber form. Theory advises that
the HA nano-needles must be of high aspect ratio and be
aligned in the matrix to gain sufficient stiffness. We have
explored several processing techniques for accomplishing
this task, and have successfully made composites in the 8-
to 10-GPa range. Variations of this structure will also be
described.
STAGES MOULDING A NEW TECHNOLOGY FOR THE PRODUCTION OF PLASTIC PARTS
This paper presents a novel technology to produce
plastic parts called “Stages Moulding”. The patented
technology allows producing plastic parts with complex
shapes, from a wide variety of polymers, with excellent
surface quality, reduced thermal and mechanical stresses
and possibility to produce parts with reduced weights.
This novel process uses cheaper moulds and equipments
than those used in injection moulding. The specific
characteristics previously mentioned make this
technology very promising for the production of plastic
parts for different markets. The paper explains the main
characteristics of this technology presenting some real
examples of parts produced.
DEVELOPMENT OF STARCH BIOBASED AND BIODEGRADABLE PLASTICS
FOR THEIR USE IN TRAYS FOR FOOD-PACKAGING
This research work develops new methods to
produce biodegradable starch-based trays for the
purpose of replacing expanded polystyrene in the food
packaging market. The starch based biopolymers
present several drawbacks like poor mechanical
properties and very high density. In order to overcome
these drawbacks two research lines have been set up:
blending thermoplastic starch with biobased
reinforcements from agricultural wastes like barley
straw and grape wastes, and testing the foamability of
these materials with a Microwave-foaming method.
RELEVANCE OF THE FEMTOLASER NOTCH SHARPENING ON THE IMPACT
FRACTURE OF POLYCARBONATE
The traditional sharpening through the razor blade
method employed in the fracture characterization of
polymers creates plastic deformation at the notch tip,
which affects the fracture toughness values. Recently it
has been applied a technique based on femtosecond
pulsed laser ablation, which removes material with almost
no heat dissipation, preventing melting and thermal
deformation of the surrounding area and without plastic
deformation at the crack tip. In this work, the fracture
toughness of polycarbonate was studied using the Linear
Elastic Fracture Mechanics testing procedure at impact
velocity, evaluating the influence of crack sharpening by
femtolaser or razor blade sliding.
EFFECT OF NANOCLAYS ON THE FOAMING BEHAVIOR OF RIGID
POLYURETHANE MONITORED BY X-RAY RADIOSCOPY
X-ray radioscopy is a technique in which a series of
radiographies are acquired during an evolving process.
The present study aims to investigate the mechanisms
occurring during the reactive foaming process of rigid
polyurethane (PU) foams in its liquid state. The work
addresses a comparative study of in-situ pore growth
determination in PU foams with and without
nanoadditives (nanoclays), based on the mentioned
technique and thus providing a valid methodology to
investigate the foaming process in all its stages. The
results confirm that nanoparticles addition modify the
final pore size most probably based on a higher
nucleation rate at initial stages.
POLYURETHANE FOAM NANOCOMPOSITES: RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND FILLER-MATRIX CHEMICAL INTERACTION
Nanofillers are added to rigid PU foams to improve their mechanical properties, however this expected behaviour is not always found. A poor dispersion of the fillers is usually accepted as a possible explanation, but chemical interaction between matrix and fillers could also result in a reduction of the final foam properties. In this study, polyurethane rigid foams (with and without nanoclays) have been produced and characterized. Different dispersion techniques have been used. The experimental results suggested that chemical interaction between fillers and matrix plays a critical role in the mechanical behaviour of these type of systems.
IMPROVING THE THERMAL INSULATION OF POLYSTYRENE FOAMS BY THE
ADDITION OF CARBON BLACK.
This paper presents an investigation on the improvement
of the thermal conductivity of polystyrene foams by using
different types of carbon blacks as additives. Carbon
blacks with different morphologies were used as IRblockers.
To test the changes in the conductivity foams
with densities between 20 and 100 kg/m3 were produced
using the solid state foaming technique. The cellular
structure and thermal conductivity were analyzed in
detail. In addition the thermal conductivity was
analytically modeled to study the influence of the
different carbon black types on the heat flow by radiation.
The best morphology to reduce the thermal conductivity
has been detected.
|
This item is only available to members
Click here to log in
If you are not currently a member,
you can click here to fill out a member
application.
We're sorry, but your current web site security status does not grant you access to the resource you are attempting to view.