FILLER CONTENT

ASTM D1579-01 Standard test method for filler content of phenol, resorcinol, and melamine adhesives. 

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The relative effectiveness of nucleating agents in a polymer can be determined by measuring recrystallization exotherms of samples molded at different temperatures (105). The effect of catalyst concentration and filler content has been determined on unsaturated polyesters by using dynamic thermal techniques (124). Effects of formulation change on the heat of mbber vulcanization can be determined by dsc pressurized cells may be needed to reduce volatilization during the cure process (125). 

Figure 12.21. Effect of filler content on the properties of plasticised PVC compounds. (a) Tensile strength, (b) BS softness number.

Na20 content Filler content Time Molecular weight of polyethylene... 

It is precisely the loosening of a portion of polymer to which the authors of [47] attribute the observed decrease of viscosity when small quantities of filler are added. In their opinion, the filler particles added to the polymer melt tend to form a double shell (the inner one characterized by high density and a looser outer one) around themselves. The viscosity diminishes until so much filler is added that the entire polymer gets involved in the boundary layer. On further increase of filler content, the boundary layers on the new particles will be formed on account of the already loosened regions of the polymeric matrix. Finally, the layers on all particles become dense and the viscosity rises sharply after that the particle with adsorbed polymer will exhibit the usual hydrodynamic drag. 

Filler content, % aci values for ash with specific surface areas, m2/g ... 

Rheological experiments have shown that the relative viscosity of compositions filled with the above materials is an exponential function of filler content by volume. The impact of an otherwise constant quantity of filler increases in the series FP — LDP — SDP, i.e., symbatically with the probability of particle comminution in the plasticization process. This effect is most clearly apparent for... 

Note that, apart from the filler particle shape and size, the molecular mass of the base polymer may also have a marked effect on the viscosity of molten composites [182,183]. The higher the MM of the matrix the less apparent are the variations of relative viscosity with varying filler content. In Fig. 2, borrowed from [183], one can see that the effect of the matrix MM on the viscosity of filled systems decreases with the increasing filler activity. In the quoted reference it has also been shown that the lg r 0 — lg (MM)W relationships for filled and unfilled systems may intersect. The more branches the polymer has, the stronger is the filler effect on its viscosity. The data for filled high- (HDPE) and low-density polyethylene (LDPE) [164,182] may serve as an example the decrease of the molecular mass of LDPE causes a more rapid increase of the relative viscosity of filled systems than in case of HDPE. When the values (MM)W and (MM)W (MM) 1 are close, the increased degree of branching results in increase of the relative viscosity of filled system [184]. 

The value of A decreases linearly with increasing filler content for a fixed filler content it increases from a filler with the spherical shape of particle to scales and further to fibers. For /J the observed behavior was reversed. 

The authors of [203-205] proposed a theory according to which the normal stresses of the matrix and filler may differ only under one condition i.e. the filler content by volume is above some critical value — when its concentration is sufficient to generate the so-called secondary network. In accordance with Privalko and Lipatov s classification [102], this concentration corresponds to the lower boundary of the high-filled class of composites. 

As established in [214], in roller-mixed PVC-based composites one observes a much better uniformity of filler distribution over the matrix volume the relative viscosity is thereby considerably reduced. That is, for a fixed filler content, the viscosity of a system with agglomerates is always higher than that of the well-dispersed sample. 

Depending on the nature of the polymer-filler interaction and the fracture surface status (smooth or rough), Eq. (34) predicts either a rather smooth variation of the elongation with increasing filler concentration or a sharp drop at some small filler content. 

From the models worked out in [236, 237] it ensues that for a fixed filler content the composite moduli must be greater in the case of absolute adhesion than where there is practically no adhesion at all. Yet, in a number of works it has been noted that, quite to the contrary, the modulus of the composite is practically independent of adhesion [238-241]. 

In a series of reviews [244-246] the models proposed for the assessment of the effect of fillers on the complex of PCM properties are discussed. Analysis of the models shows that, for a fixed filler content, the strength must be higher in compositions with fillers featuring the absolute adhesion to the matrix than in systems with little or no adhesion. The relative elongation and specific impact strength must, on the contrary, go up with the increasing adhesion. 

Using water repelling agents it is possible to either considerably reduce the viscosity of compositions with a predetermined filler content, or increase the admissible filler concentration for given viscosity [262], In a filled system (e.g. PP + chalk) the treatment of the filler to enhance its polymerophilic properties promotes breakdown of agglomerates [263],... 

It has been found that, for a fixed mineral filler content, the viscosity of PMF-based composites increases when the coat is made of polyethylene [164, 209, 293], poly(vinyl chloride) [316] and polypropylene [326, 327], The picture was different, however, for composites based on the ethylene/vinyl acetate copolymer to which kaolin with grafted poly (vinyl acetate) was added [336]. Addition of PMF with a minimum quantity of grafted polymer results in a sharp drop of flowability (rise of viscosity), in comparison to addition of unmodified filler but with a further increase of the quantity of grafted polymer the flow gradually increases and, depending on the kaolin content and quantity of grafted polymer, may even become higher than in specimens with unmodified filler, for equal concentrations. 

Second, if we speak about polymer melts, we should take into account their non-Newtonian properties, so that theTi((p) dependence will be different at different rates or shear stresses. This, besides all other things, raises the question on the correct selection of conditions for comparing the viscosity of the systems with different filler content. 

Fig. 2-40 Example where creep rate is related inversely to the reinforcements and filler content.

Filler Content c, % Tensile Modulus E, N/mm2 (kips/in.2) Breaking Strength o>, N/mm (kips/in.2) Elongation at Break st, % Impact Strength az, kJ/m2... 

The experimental data show that the magnitude of the heat capacity (or similarly of the specific heat) under adiabatic conditions decreases regularly with the increase of filler content. This phenomenon was explained by the fact that the macromolecules, appertaining to the mesophase layers, are totally or partly excluded to participate in the cooperative process, taking place in the glass-transition zone, due to their interactions with the surfaces of the solid inclusions. 

The variation of the adhesion coefficient, A, versus the filler content, uf, was plotted in Fig. 15, for a diameter of the fibers equal to df = 12 pm. The strong variation of this quantity with the filler content is obvious in this figure and confirms once again the role played by the mesophase. 

With DMA the effect of temperature on the modulus can be studied. By increasing the temperature from -150 to 300°C, one encounters several transitions in PA (Fig. 3.1). There is a transition at about —120°C, the y-transition, which is due to the mobilization of methylene units. There is also a transition at —30°C, which is present in wetted aliphatic PA this is due to non-H-bonded amide units and is termed the /J-transition. At about 50°C the glass Uansition (Tg) (a-transition) of the aliphatic polyamides PA-6 and PA-6,6 occurs. At this Uansition, the modulus is lowered considerably. For partially aromatic PA, the Tg occurs above 100°C. The last transition is the flow temperature, at which temperature the material melts the flow temperature and the melt temperature, as measured by DSC, correspond well. The modulus is a measure of dimensional stability and increases with crystallinity and filler content (Fig. 3.12). 

Why does the stress increase greatly with filler content at a small strain ... 

Thus, in the coarse carbon black-fiUed mbber, the modulus increases according to the Guth equation with filler content, because the contribution from the GH layer (1% of the diameter) will disappear... 

Transition from liquid behavior to solid behavior has been reported with fine particle suspensions with increased filler content in both Newtonian and non-Newtonian liquids. Industrially important classes are rubber-modified polymer melts (small rubber particles embedded in a polymer melt), e.g. ABS (acrylo-nitrile-butadiene-styrene) or HIPS (high-impact polystyrene) and fiber-reinforced polymers. Another interesting suspension is present in plasticized polyvinylchloride (PVC) at low temperatures, when suspended PVC particles are formed in the melt [96], The transition becomes evident in the following... 

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