Testing and quality

A product development process at
Sulzer Mixpac also has to pass through
a number of stages—from the product
idea through the first prototypes to the
manufacturing of the tools 1 and the
subsequent production by injection
molding and other manufacturing
processes 2. The last milestone in the
product development before the first
“marathon“ is the so-called series
approval. This example should illustrate
that the process planning (the training
plan), the determination of the process
steps (the training), and also the mea -
surement (target/actual) are decisive for
the success of the product development
3. Processes and their desired results
have to be defined before they can be
measured. At Sulzer Mixpac, it is taken
for granted that “if something needs to
be improved, one first has to measure it.”
Sulzer Mixpac is a “top athlete” in the
plastics industry. The company does not
deal with all types of plastics, however.
The focus lies on the world of semi-crystalline
thermoplastics. Due to their properties,
semi-crystalline thermoplastics
are being increasingly used. At the same
time, however, the specifications and
legal regulations for the industries are
becoming stricter. Both the legal requirements
and the daily pursuit of optimal
processes require solid measurement
and analysis technology based on stateof-the-art
science and technology. These
technologies are used in research and
development, quality testing, and process
and product optimizations, as well as
for failure analysis.
A wide bandwidth of physical and
analytical methods is necessary in order
to portray the complete product development
process in a measurable manner.
In its own laboratories, Sulzer Mixpac
has the required instrumentation, the
many years of experience, and the knowhow
that are necessary for the polymer
analysis.
Thermal analysis
Many of the properties of the starting
materials that are important for plastic
injection molding, and also for the end
products, can be determined with the
help of thermal analysis.
• DSC (differential scanning calori -
metry): DSC analysis measures the
necessary amounts of heat that are
used or arise in the physical transformation
of the plastic. The reaction heat,
the decomposition temperatures, and
also the glass transition and melting
ranges can be cited as examples.
• TGA (thermo-gravimetric analysis):
The composition and filling materials
of the returns can be analyzed through
the “controlled evaporation” of plastics.
In order to do this, the materials
are heated up to 1100 °C.
Rheology
Rheology describes the flow characteristics
of substances. In the plastics
industry, this property is a very
important measurement parameter for
the processing of various plastics, as
well as for the individual batches of
the same plastics.
• MFR/MVR (melt flow rate/melt
volume rate): The end result provided
by the melt flow rate (MFR) is the
flow behavior of the plastic under
certain temperature and pressure conditions.
The viscosity of the plastic
melt is determined by this measurement
procedure.
2 Injection molding production in Haag, Switzerland.
• Rotation viscometer: Lying on a
heated plate, a plate or a cone is
pressed on to the specimen by means
of a pressure-driven motor. During the
rotation process, the frictional force
(torque) that is necessary to overcome
the flow resistance is measured. The
result measured is, for example, the
shear viscosity of the specimen. This
measurement is taken to determine
the characteristics of plastics or mixed
adhesives with regard to workability
and/or mixing quality.
Spectroscopy
It is possible to determine the structure
and/or the identity of the plastic
through spectroscopy. With color analysis,
it is, thereby, possible to break down subjective
color perceptions into reproducible
measurements.
• FTIR (Fourier transformation infrared
spectrometer): With this measuring
instrument, it is possible to carry out
very fast identifications (characterizations)
on organic materials. The
specimen is clamped in the ATR unit
and is, thereby, placed in the path of
a laser-controlled infrared beam. The
penetration of the radiation excites the
atomic groupings of the melt (vibrations),
from which the absorption
spectrum can be measured. The position
and intensity of these peaks
are characteristic for certain atomic
groupings. By comparison with the
“standard spectra” available in the
database, the material characterization
and contamination of plastics, as
examples, can be carried out quickly
and easily.
TESTING AND QUALITY
Sulzer Technical Review 1/2011 |
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