Polypropylene coupling agents

Ht prime . [Hoechst Celanese/Spec. Chm.] Furan dione ptopene polymer or maleic anhydride grafied polypropylene coupling agent for FP, PA. 

Hostaprfane . (Hoedist Cehuiese/Spec. Ch ] Furan dkme propene polyiner or maleic anhydride gralited polypropylene coupling agent for PP, PA. 

Natural materials that have been used to modify polymer properties include wood sawdust [188, 189], coconut fiber [167], carbon fibers [37], oat husks, cocoa, shells [190], sugarcane fibers [191], and banana fiber [193]. Monhonty and coworkers [193] observed a 70% increase in the flexural strength of polypropylene to which has been added 30% jute with a maleic anhydride-grafted polypropylene coupling agent. 

Coupling agents such as hydroxymethyl benzene or a polyoxyeth-ylene-polyoxypropylene ether [polypropylene glycol-polyethylene glycol ether, POE-POP ether, e.g., Ucon synthetic lubricant from Union Carbide Corp.)] and hydrotropes, such as an imidazoline car-boxylate may also be needed to hold the formulation together. 

Fig. 10. Viscosity and first normal stress difference vs. shear stress for polypropylene (at 200 °C) filled with calcium carbonate (50 wt%) with and without a titanate coupling agent (TTS ) (O, ) pure polypropylene (PP) (A,A) PP/CaC03=50 50 (by wt.) ( , ) PP/CaC03=50 50 with TTS (1 wt%). The open symbols were obtained from a cone and plate instrument and the closed symbols from a slit/capillary rheometer.

Similarly, Plueddemann has reported [3c] an optimum silane coupling agent layer thickness of 50-200 A for commercial glass fiber treatment for use in composite materials. On the contrary, optimum adhesion of polypropylene to aluminum was obtained with a silane primer layer between 0.5 and 10 pm thick. In... 

Improvement in the mechanical properties of glass/ polypropylene composites by using an azidosilane coupling agent [32]... 

Hunt et al. [ 17] have investigated the role of various coupling agents, such as zirconates, titanates, and zircoaluminates, in zirconia-polypropylene suspensions for use in the production of ceramics by injection moulding. All the coupling agents were observed to reduce the melt viscosity. 

The addition of MAPP at around 1-2% ensures perfect coverage of the wood fibres by polypropylene or polyethylene. The micrographs in Figure 5.25 clearly show the lack of adhesion between the fibres (in dark colour) and the PP matrix (in light colour). The mechanical properties are increased by at least 30% when a coupling agent is used. 

Figure 14.22 shows a line with examples of products. The basic plastic, usually polypropylene (PP) but also high-density polyethylene (PE-HD), and the additives required by the formulation (e. g coupling agent, UV stabilizer, pigment if required, antibacterial agent, or flame retardant), are added to the first barrel of the screw kneader by a gravimetric... 

Coupling agents for more inert polymers like polyolefins are often acid-modified versions of the matrix polymer, with maleic acid grafted polypropylene as a prime example. 

Figure 6.38 Viscosity (open symbols) and first normal stress difference (closed symbols) as a function of shear stress for neat polypropylene melt (Q. )> the same melt filled with 50% by weight CaC03 particles of size 2.5 fx, (A, A), and the filled melt with a titanate coupling agent ( , ). (From Han et al. 1981, reprinted with permission from the Society of Plastics Engineers.)...

The data in Table 6.4 have been developed from many years of practical experience. It provides information on the suitable types of coupling agents differentiated by the organic portion of the molecule. In polymers which are not reactive, such as polyethylene, polypropylene, etc., adhesion is built up by hydrogen bond formation. Methaciylosilanes provide this effect with these materials. Experimental work is always recommended to evaluate each combination of coupling agent, substrate, and polymer. So many diverse factors are involved that theoretical predictions are not always reliable. 

U.S. Pat. No. 5,153,241 [66] discloses composites made of thermoplastic polymers such as low-density polyethylene, polypropylene or polystyrene (90-60%) and wood pulp or sawdust (10-40% by weight) grafted with a titanium coupling agent (isopropyltri[n-ethylaminoethylamino] titanate) in acetone, along with some inorganic fillers, such as calcium carbonate and Portland cement. 

U.S. Pat. No. 5,981,631 [70] describes achieving compatibility of the ingredients in a thermoplastic composition by extruding a polymer (polyethylene, polypropylene, or PVC), wood fibers, and a coupling agent containing fatty acids and rosin acids, both having at least 16 carbon atoms. 

U.S. Pat. No. 5,480,602 [85] discloses a composite comprising polypropylene, polyethylene, or their combination along with lignocellulosic particles (50-70% by weight) and a polyurethane coupling agent (15-3% by weight of the mixture). 

TABLE 4.28 Effect of a nanoclay on flexnral strength and flexnral modnlns of polypropylene-based WPC containing 50% (w/w) maple wood flonr (80-mesh) [24]. No coupling agent added... 

TABLE 4.29 The same as in Table 4.28, but in the presence of 4% of a coupling agent, polypropylene grafted with maleic anhydride [24] ... 

There are many coupling agents, compatibilizers, crosslinking agents and other dispersants described in the literature as experimental ones. They are not used industrially because of a number of reasons, mainly because of the lack of scale-up testing and the lack of hnancial considerations. Among them are, for example, iV-vinylformamide-grafted polypropylene [14] and poly(A-acryloyl dopamine [15]. 

An application of Fourier transform infrared spectroscopy (FTIR) to maleated polypropylene-treated wood liber has indicated that esterification reaction between hydroxyl groups of lignilied liber (unbleached thermomechanical pulp, TPM) and the coupling agent does not occur [5], The FTIR spectra did not indicate the presence of any distinct absorption bands near 1730 cm, which may be associated to other ester links besides those already present in wood fiber. However, tensile and flexural strength and impact resistance of the WPC in the presence of the maleated polypropylenes increased significantly (up to 280%) (Tables 5.9 and 5.10). 

The question regarding the mechanism(s) of the action of maleated coupling agents was approached via studying the crystallization kinetics in wood-fiber-filled polypropylene in the presence and the absence of a maleated polypropylene copolymer... 

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