Polycarbonate Parts Research Articles

Hard coatings by plasma CVD on polycarbonate for automotive and optical applications

In many applications, plastic surfaces need coatings as a protection against abrasion or weathering. Leybold Optics is developing Plasma CVD processes and machinery for transparent hard coatings (THC) for polycarbonate parts. In this paper we present the current features and remaining challenges of this technique. The coatings generally show excellent adhesion. Abrasion resistance is superior to commonly used lacquers. Climate durability of the coating has been improved to pass the tests demanded by automotive specifications. Current activities are focused on improving the durability under exposure to UV radiation. Estimations show that our high-rate plasma CVD hard coating process is also economically competitive to lacquering.

Sub-micrometer adhesion modulation on polymer surfaces containing gratings produced by two-beam interference

Grating-like structures having a period of 416 nm were produced on the surface of poly-carbonate films by two-beam interference realized by the fourth harmonic of Nd:Yag laser. The period of the structures was half of that the applied master grating, the ratio of the width of the valleys to the period was tuned by the intensity, the depth of the modulation was increased by the number of laser pulses. Pulsed force mode atomic force microscopy was applied to study the topography and the adhesion on structured surfaces with sub-micrometer resolution. The adhesion modulation caused by the topography was calculated along line cross-sections of the AFM pictures taking into account the tip and surface geometry. The separation of the effects of the topography and the laser-induced material changes proved that the adhesion is increased at the areas illuminated by laser beam having a fluence above the melting threshold. The laser-induced material changes cause an additional adhesion increase at the valleys of the structure. It was shown that the adherence of albumin results in dense packing on poly-carbonate surface parts having sub-micrometer periodic adhesion modulation.

Residual stresses, shrinkage, and warpage of complex injection molded products: Numerical simulation and experimental validation

AbstractA numerical simulation model for predicting residual stresses and residual deformations which arise during the injection molding of thermoplastic polymers in the post‐packing stage has been developed. A thermoviscoelastic model with volume relaxation is used for the calculation of residual stresses. The finite element method employed is based on the theory of shells as an assembly of flat elements. This theory is well suited for thin injection molded products of complex shape. The approach allows the prediction of residual deformations and residual stresses layer by layer like a truly three‐dimensional calculation, while reducing the computational cost significantly. The hole drilling technique is used to measure the residual stresses across the thickness of the product. A three‐dimensional laser digitizing system, an image processing technique and a dual displacement transducer system are used to measure the warpage. Experiments are carried out on polycarbonate and high density polyethylene parts. Numerical results are in qualitative agreement with experimental observations, i.e., the skin of the box is surrounded by a compressive region while the core region is in traction. The trend of both the experimental and the predicted residual stress profiles is close. Different examples are presented to illustrate the influence of the geometrical complexity of the shape on the final deformations and residual stresses. The influence of the mold temperature on residual stresses and warpage is also analyzed.

The Physical Effects Of Volatile Anesthetics On Polycarbonate Membrane Oxygenators

The spillage of enflurane on the outside of a membrane oxygenator during cardiopulmonary bypass resulted in a leak at the venous outlet, with nearly fatal outcome. We studied the effect of three different volatile anesthetics on the polycarbonate parts of unused and used COBE CMS membrane oxygenators with 30-HRV open filtered reservoir. The polycarbonate parts were submitted to a series of tests and then exposed to the volatile anesthetics. Intact polycarbonate was not affected by etheric volatile anesthetics, but by halothane. Internal and externally applied stress (cyclic loading or pressure) may make the polycarbonate vulnerable for etheric volatile anesthetics. The bending motion caused by the continuos vibrations of the cardiopulmonary pump may damage the polycarbonate equipment, thus making it vulnerable to the harmful activity of etheric volatile anesthetics.

Quality control of polycarbonate parts

Analytical methods and control charting have been instituted for accessing the integrity of purchased parts molded from General Electric Company's Lexan ® 503 polycarbonate resin. The glass transition temperature, fiber glass, and loss-on-ignition ash data are used to establish means and control limits. Parts found to be out of control are examined using intrinsic viscosity in conjunction with the routine analyses.

Study of birefringence character of injection‐ and compression‐molded polycarbonate and its interpretation

AbstractBirefringence development in molded polycarbonate is of great importance in the manufacture of optical discs. It is important in characterizing birefringence to realize that we are dealing not with a scalar but with the anisotropy of the refractive index tensor–and with the orientation and shape of the refractive index ellipsoid. This usually varies heterogeneously; i.e., point‐to‐point through the thickness of molded parts. We present here an experimental study of the shapes and orientations of refractive index ellipsoids in injection‐ and compression‐molded polycarbonate parts. We consider the variations in ellipsoid character as a function of molding conditions such as injection rate and quench. In injection‐molded parts, the refractive index ellipsoid is coaxial with the flow direction in the center of the parts, but varies with position in the direction of the mold walls. In some cases, the extinction angle reaches a maximum at the mold wall and in other cases, there is an intermediate maximum. In the central “flow‐thickness” direction plane, the transverse axis of the refractive index ellipsoid is perpendicular to this plane. The birefringence (in principal axis coordinates) in the flow‐thickness direction plane exhibits an intermediate maximum whose position and magnitude vary with molding conditions. In some cases, multiple maxima exist. In compression‐molded parts, a principal axis is normal to the mold wall. The results are interpreted in terms of the Rheo‐Optical Law using flow‐induced orientation and residual stress mechanisms. If the contribution of the residual stress to the birefringence can be subtracted, we may compute biaxial orientation factors. We do this for a case that has low residual quench stresses.

Critical J-Integral Value of Injection-Molded Polycarbonate Using a Low Thermal Inertia Mold

Abstract A low thermal inertia mold (LTIM) is evaluated based on its ability to reduce residual stress and molecular orientation in thin polycarbonate parts. The mold employs a special cavity design which incorporates the use of high-temperature (above 350 °C) thermoelectric devices. Residual stresses are compared in LTIM and conventionally molded parts via an estimation of critical J-integral values (Jc)-the essential energy needed for crack initiation per unit area. The estimated values of Jc for LTIM and conventional parts are 6.3 and 7.3 kJ/m2, respectively. This difference may be due to the elevated LTIM cavity temperature which alleviates residual stresses and in turn reduces the estimated value of Jc. Observations of birefringence distributions were used to compare molecular orientation. The amount of birefringence is greatly reduced in a large central region of the LTIM parts, indicating low levels of orientation. Conventional parts show distinct color fringes along the melt flow path, indicative ...

Controlling the properties of polycarbonate during processing with the object of extending the service life of machine parts

The supermolecular structure and mechanical characteristics of polycarbonate can be controlled by introducing artificial structure-forming nuclei during processing into machine parts. The changes in the supermolecular structure and mechanical characteristics of the polycarbonate under cyclic loading on an hydraulic test bench are examined. The magnitude and distribution of the stresses in polycarbonate parts have been determined by means of strain-gage measurements, and recommendations are given for selecting the optimal part dimensions.