polyethylene compounds containing mineral fillers modified by acid coatings. 1: characterization and processing.

by:ZHENHUA     2020-09-02
Studies have been carried out to determine the effect of the filling coating on the processing properties of medium density polyethylene (MDPE]
Ultra-fine modification by flame-
Flame retardant magnesium hydrogen ([
M The Side size of these reunions (
About 1 [micro]m)
Smaller than in the uncoated sample, and corresponding to the width of the two main particles in the observation plane.
Figure 12 shows the degree of agglomeration [M Figs. 14-15.
The polymer filled with Mostun is expressed in a pseudo-plastic manner, and the shear viscosity is a reduced function of the shear rate.
In the case of a power law model [27]
The shear flow behavior is applicable, and the biological diagram of the shear stress ([tau])
Shear rate ([gamma])are linear: [tau]= k . [([gamma]). sup. n]hence: log[tau]=logk + n. log [gamma](4)
Shear viscosity ([eta]): [eta]= k . [([gamma]). sup. n-1]hence: log [eta]= logk + (n-1). log [gamma](5)
Plot in Fig. 14-
15 is based on the power law interpretation, and for most compounds studied within the selected shear rate range, the power law interpretation is valid (40-2000 [s. sup. -1]).
Gradient n is power lawindex (
False plastic index]
K is the consistency index, which is related to the viscosity of the material with a preset pseudoplastic index at a low shear rate.
Flow curves are usually found for all filled-MDPE compounds;
Using the power law interpretation, table 3 gives a summary of the data of the power law interpretation.
Capillary mold with constant lengthdiameter (L/D)
For the Wall, the ratio is usedslip analysis (seebelow).
The flow curve shown in the figure. 14-
15 has been from (18 X 1. 8)
Mm mold, considered typical of the results obtained from all other molds.
It should be noted that no attempt was made to make a final correction of the shear flow data to overcome the source of inaccuracy due to the convergence flow of the inlet.
In this case, Bagley correction technology [28]
Because the length/radius of the mold (L/R)
For the series of molds studied, the ratio is constant.
The flow analysis table shows several important results: first, the data depends to a certain extent on the mold geometry, which is demonstrated by the difference in flow behavior that occurs when using molds with different Capillary lengths.
This is discussed in the following paragraph from the perspective of the wall slip phenomenon.
Coating concentration is also important because compounds containing 14% behenic acid coatings always produce a lower shear viscosity compared to compounds with lower coating content (Fig. 14).
In addition, compounds containing [Mg(OH). sub. 2]
Modified filler with ten acids (Fig. 15)
It has a higher shear viscosity than the coating containing behenic acid.
These results are consistent with the specific energy data obtained from the APV extruder (Fig. 9)
, This reveals how the reduction in viscosity can help the calculation of the composite torquereadings, power consumption and specific energy as the coating chain length and concentration increase.
So, we have come to the conclusion that,
The acid coating level has a significant effect on the shear flow behavior of the filled MDPE compound, which is the same as the effect of the behenate salt (
Figure 14% data of behenic acid14)
As we all know, when the behenic acid coating is used for super-Single level.
In addition, when MDPE contains uncoated [the observed increase in viscosity]Mg(OH). sub. 2]
The packing is relatively moderate and the false plastic index is low (Table 3).
This will be discussed in the next paragraph, depending on the limited speed of the flow boundary.
Flow analysis using a mold with variable length but constant length/diameter ratio in order to study wall sliding behavior based on the method first attributed to Mooney [16, 28].
Apparent shear rate ([gamma])
The data takes over a series of constant shear stresses ([tau])
Horizontal, drawing the anti-mold radius (1/R)
Derived from visual measurements in the capillary range.
The existence of sliding of the positive gradient flow mode wall indicates the finite flow rate at the boundary of the capillary flow. Figures 16-
18 shows the selection of wall sliding data determined from the flow curves obtained from these molds.
For this type of analysis, relatively high levels of scattering are not uncommon, especially since in this case the data points are obtained from a series of flow curves that assume to exhibit power-law behavior.
There is no evidence of wall slippage in an unfilled MDPE polymer (Fig. 16)
However, at a shear stress level of up to 435 kPa, for compounds containing uncoated fillers (Fig. 17)
There is clear evidence that for all shear stress levels greater than 300 kPa, the slope of the constant shear stress line is greater than zero.
The higher the stress is heard, the greater the sliding speed of the wall.
This observation explains the apparent abnormal flow behavior of this compound in the flow curve discussed earlier (Figs. 14-15)
Because, under any given shear stress, wall sliding causes a higher apparent shear rate.
In contrast, any compound containing coated fillers does not show a tendency to slide at the flow boundary, even if organic-
Up to 14% in concentration (Fig. 18).
Mechanism of the wall-
It is not clear that there will be slippage in compounds containing uncoated fillers, which is the subject of ongoing research.
By using a surface coating, the interaction energy between the filler and the polymer can be controlled.
The meaning of these results is that the interaction energy associated with the unmodified filler increases (Fig. 8)
It seems that a limited wall slip is given at the flow boundary.
It is often argued that a wall slide occurs by migrating small molecules to the mold wall.
However, magnesium behenatesalt exists in compounds containing high levels of behenic acid co-filling (
See conclusions in the infrared spectrum section)
In the study presented here, it does not appear to cause an external lubrication effect.
The other proposed mechanism is the failure of adhesion between the polymer and the capillary wall [29, 30]
, Or the adhesive failure between the polymer chains in the melt near the wall [31]. Hill etal. [32]
A relationship has been developed to determine the critical wall shear stress of the wall slip ([[tau]. sub. cr])
Bonding work ([W. sub. ad])
Between the polymer and the mold wall :[[tau]. sub. cr]= 40 . ([W. sub. ad]/R)(6)
Further research is needed to determine the performance required to verify the application of this method, or to make corrections from this method to explain the different adhesion properties of heterogeneous systems such as polymers containing acids
Modified filler particles, including small-
Agglomeration effect of scale.
The different degrees of response analysis and orientation effects on packing dispersion and composite viscosity show the molecular orientation of MDPE polymers induced during injection mold filling, as shown in the experimental response data shown in the figure19.
These data are estimated based on the degree of contraction (
Elastic recovery)
After a period of static heating at 120 [degrees]
In the Air oven.
Overall, the measured response values for all samples, especially for unfilled MDPE, are very high, as are for high-mole mass materials.
However, these decrease gradually with the addition of uncoated fillers.
If the filler is re-coated continuously, the reply will be significantly increased, and when the short amount is increased, the reply will gradually decrease. chainfatty-
Acid coating is applied.
For example, for a higher level of behenic acid coating (
Greater than 10%)
, The reply value is reduced below the MDPE compound containing the uncoated filler.
When used on [Mg(OH). sub. 2]
Filler, with the increase of coating level, the reply seems to gradually increase, and the limit value close to the unfilled MDPE is about 75%.
Reply analysis is a method to measure the polymerization chain orientation relaxation caused by partial recovery of elastic components of shear strain in injection moldsfilling phase.
Figure 1. Initial and most eye-catching observations
19 is the response level that has been measured is very high.
This is attributed to the high molecular weight of the grade MDPE polymer of the pipe used, which requires fast injection speed and high retention pressure to fill and fully pack the mold.
Therefore, these conditions will produce high shear stress in the flowing melt, which is the reason for the observed heterosexual effect.
In these experiments, all injection molding conditions set independently remain the same at all times, so only the effects of the formulation are compared in the results.
Regression analysis of the center
Stretch the outer section of the dumbbell bar, corresponding to the position where the flow is relatively uniform, thus avoiding the impact due to excessive packaging at the position close to the gate.
Height orientation and alignment of chains
When injection molding of a semi-crystalline polymer, extended crystals are induced, especially in areas of high shear force and rapid cooling near the cavity wall.
When the sample is subsequently raised to a high temperature, a reversal occurs subsequently, as the previously directed polymer chain is directed toward a random-
Coil conformations, they are the preferred state of the lowest free energy.
For an unfilled MDPE, the reply value reaches 75%, well above 55% of the observed decrease level when not coated [30%]Mg(OH). sub. 2]
Exist in compounds.
It is expected that there will be a reduction in the melting of the addition of mineral fillers to the viscous polymer melt, although due to the enhanced thermal conductivity of the filled polymer, this effect will be offset by more cooling of the filled polymer
The subsequent increase in response observed in compounds containing coated fillers is associated with modified flow behavior (Figs. 17-18).
Therefore, a clear correlation was demonstrated between the appearance of wall slippage observed in MDPE modified by uncoated fillers and the subsequent lower degree of reversal observed in this material.
For a given injection (Volume flow)
During injection molding, the Wall slip at the cavity wall reduces the shear stress and orientation generated in the polymer chain.
In addition, the enhanced polymer-when there is an uncoated filler-
To some extent, the filling interaction may resist the driving force of elastic recovery.
Add about 6% coating in [Mg(OH). sub. 2]
The filler restores the fat to the maximum extent, but further increases the fat
The acid coating subsequently reduces the response, which may be due to the same lubrication effect that also results in a reduction in the shear viscosity in these compounds (Figs. 14-15)
This was discussed in the previous section.
In contrast, the addition of the ATPE coating increases the orientation relative to the compounds containing other types of coating modified fillers.
The chain entanglement and physical interaction between the polymer matrix and the fat ATPE chain helps the compound to have a higher viscosity and enhanced melt elasticity, resulting in a higher response.
Correlation with product performance add fat-
The acid coating on the filler promotes the relaxation of the polymer chain in the thermoplastic compound at high temperature, which is particularly evident at the addition level of about 6% in weight.
This coating concentration is related to the experimental single layer coverage and will be shown in the mechanical testing procedure (
See the second part of this article)
Represents the level of intense addition of many compounds studied.
The molecular orientation level taking the measurement reply as an example also has a great influence on the mechanical properties and will also be discussed in the second communication.
The shear stress distribution generated during injection molding is not only responsible for the arrangement of MDPE polymer chains, but also creates the preferred orientation of the high aspect ratio [Mg(OH). sub. 2]
Fill the particles. X-
Ray diffraction (XRD)
The analysis, also shown in the second part of this communication, reveals the plate-
During injection molding, the tank bag filler is arranged in parallel to the main flow direction.
This arrangement is shown to be very high when the coating level is 6% fatty acids.
When platelets are prioritized on the injection molding plane, the polymer chain shows a higher degree of response, as the direction of contraction is consistent with the direction of arrangement.
As we all know, the degree of polymer and/or filler particle orientation, combined with the direct effect of filler content and dispersion, may have a considerable impact on the mechanical properties of the injection molding assembly.
Further discussions in this regard will take place in Part II of the original text.
Therefore, for the filled thermoplastic compound, it is not appropriate to directly associate the formula variable with the specific mechanical properties.
On the contrary, it is important to recognize that different types and concentrations of coatings change the flow behavior of compounds during the manufacturing of components, which will subsequently have additional effects (but indirect)
The impact on the final physical nature.
Conclusion dry mixing process data allow determination of optimal mixing time for fat-magnesium hydroxide filler coatingacids.
These depend on the type and number of coatings added to the filler and the extent of external heating.
Infrared analysis shows that packing-
Once the temperature of the mixer exceeds the melting point of the coating, the coating reaction begins.
Best Mixing time specific to coating type.
It is possible to determine the experimental single layer of the acid and the mountain bean acid, but in the case of ten acids, the continuous reaction occurs due to the particle wear in the mixer.
Therefore, a large amount of organic magnesium salt has been formed.
Consistent experimental trends allow the prediction of optimal coating cycles in the case of other scaling
Dry mixing system.
The coating thickness data was measured by XPS and changes in the coating chain length and the addition level were shown.
Thickness between 10-detected
20 a indicates that fat c hains are perpendicular to the surface of the mineral filler.
Soaking heat data confirmed that the interaction between mineral fillers and organic polymer substrates decreased when fat content increased
Acid coating is applied.
The specific energy parameters of the screw composite data introduce the addition of the filling coating.
Due to the reduction of the interaction energy, the dispersion of the filler is enhanced, which is obtained by low temperature polishing and acid-Etching the surface.
The ATPE polymer coating increases the specific energy, which is considered due to a greater physical interaction with the MDPE chain.
All filled MDPE compounds exhibit pseudo-
Plastic shear flow behavior;
Filler increases shear viscosity of MDPE and fat
The acidic coating has an internal lubrication effect on the material.
The shear flow data depends on the mold geometry, because Wall slip appears in compounds containing uncoated magnetic hydroxide, and its mechanism is not clear.
Therefore, the infiller dispersion difference observed when using a coating with variable chain length is due to the influence of the coating on the behavior of the melting process of the compound, in terms of shear viscosity, internal and external effects such as wall sliding.
The molecular orientation in the injection sample is evaluated by heat recovery, which decreases when undeposited mg [is added](OH). sub. 2]
And then increase when coating filler is added.
Therefore, there is a clear correlation between walls
Sliding and observed responses in compounds containing uncoated fillers.
The author would like to thank the Engineering and Physical Sciences Research Committee for the sources of funding provided for this study (EPSRC)
Additional support from the UK, as well as an industrial consortium: BP chemical, ECC International, Alcan chemical, Rothon consultancy, Cookson Group, APV Baker Limited (
Industrial extruder business unit), Rosand Ltd.
And Stewart and Lloyd.
Contribution of colleagues from Loughborough University (Dr. M. Gilbertand Mr. J. F. Harper)
We are also very grateful.
Institute of Polymer technology and materials engineering (IPTME)(**. )(
Department of Chemistry)
Loughborough University, Leicester, LE11 3TU, UK reference (1. )J. A.
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