Modifiers for engineering thermoplastics

Polyethers, polysulfones, polyterephthalamides and polysulfide polymers, and several other high temperature polymers are also part of this group, but they are still produced in low volumes. 

On the other hand, the concept of polymer alloying has been amply utilized to produce blends of engineering thermoplastics that combine the properties of their components and form materials with distinct 

A common thread for engineering plastics in terms of their utilization in structural applications is their mechanical strength. Failures in thermoplastics may occur due to large stresses applied at low rates, fatigue or impact. Toughness is a major requirement in end use applications of engineering resins. The purpose of this entry is to provide an overview of the impact modification of these materials and to direct the reader to specialized publications for more in-depth discussions on this topic. 

The high rates of stress loading associated with an impact process take on a special relevance in polymers, because of their time-dependent mechanical properties. The material behaves in a more ductile fashion when deformed at low stresses or strain rates, and generally becomes harder and more brittle as the strain rate is increased. Ductile deformation processes are preferred when fracture occurs, because they absorb larger levels of mechanical energy. Temperature has a similar effect to strain rate low temperatures induce brittleness, whereas high ones allow for ductile behavior of the material. 

The measurement of impact resistance can be a complex undertaking. Because of the notch sensitivity effect, analysis of fracture in polymers relies heavily on measuring the energy required to propagate cracks in a structure. Of particular interest are cracks subjected to stresses perpendicular to the faces of the crack (also known as Mode I deformation). Cracks in Mode I deformation generally tend to grow perpendicularly 

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Storage Keep tightly closed store in cool dry place Uses Impact modifier for engineering thermoplastics adhesion modifier for rubber compds., TPOs, adhesives adhesive for biaxially oriented nylon and PC films textile adhesive food-pkg. adhesives, paper/paperboard Features Bonds at low temps. 

Typical additive packages for engineering thermoplastics have been described by Titzschkau [9], such as processing aids for PA, PP, or PET/PBT, three-component additive packages for polyamides and polyesters (nucleating agent, lubricant and process heat stabiliser) and coated copper stabilisers for polyamides. Additive packages or combinations of up to five or more additives are quite common. A typical white window PVC profile formulation comprises an acrylic impact modifier, TiC>2, CaCC>3, calcium stearate, a... 

MBS impact modifiers are used for PVC (transparent and low temperature applications, mainly in packaging), and for engineering thermoplastics, especially for low temperature applications (PC, PBT and blends). 

Core-shell impact modifiers have also been reported as impact modifiers for engineering polymers. MBS impact modifiers with a SBR core, a polystyrene middle layer and an outer layer of MMA copolymers with glycidyl methacrylate, acrylamide or methacrylic acid functional monomers were evaluated in PC/PBT blends [104]. Optimal results were obtained with 60 wt% SBR content in the MBS and a modest amoimt of a functional monomer in the MMA copolymer shell. Core-shell impact modification of polycarbonate [105] (PMMA grafted on poly(n-butyl acrylate) and PBT[106] (SAN grafted onto a butadiene based rubber) have been reported. A comprehensive review of core-sheU impact modification of various polymers (PMMA, PVC, PC, PBT, PET, polyamides, thermoplastic blends, thermosets) has been presented by Cruz-Ramos [107]. 

Noryl. Noryl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polymers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (69). Because the mbber characteristics that are required for optimum performance in DMPPO—polystyrene blends are not the same as for polystyrene alone, most of the HIPS that is used in DMPPO blends is designed specifically for this use (70). Noryl is produced as sheet and for vacuum forming, but by far the greatest use is in pellets for injection mol ding. 

The use of elastomeric modifiers for toughening thermoset resias generally results ia lowering the glass transition temperature, modulus, and strength of the modified system. More recendy, ductile engineering thermoplastics and functional thermoplastic oligomers have been used as modifiers for epoxy matrix resias and other thermosets (12). 

Good electrical insulation properties with exceptional tracking resistance for an engineering thermoplastic and, in particular, for an aromatic polymer. In tracking resistance most grades are generally superior to most grades of polycarbonates, modified PPOs, PPS and the polyetherimides. 

Reactive compatibilization of engineering thermoplastic PET with PP through functionalization has been reported by Xanthos et al. [57]. Acrylic acid modified PP was used for compatibilization. Additives such as magnesium acetate and p-toluene sulfonic acid were evaluated as the catalyst for the potential interchange or esterification reaction that could occur in the melt. The blend characterization through scanning electron microscopy, IR spectroscopy, differential scanning calorimetry, and... 

Higher costs are acceptable if particular properties are obtained. For example, engineering thermoplastics such as modified and reinforced polyamides can be used for demanding and top-of-the-range applications. 

Dr. Riew has presented more than 50 technical papers and holds more than 25 patents on emulsion polymers, hydrophilic polymers, synthesis and application of telechelic polymers, and toughened plastics for adhesives and composites. His latest research is in the synthesis, characterization, and performance evaluation of impact modifiers for thermosets and engineering thermoplastics. His research interests include correlating polymer chemistry and physics, morphology, engineering, and static and dynamic thermomechanical properties to the failure mechanisms of toughened plastics. 

Polyamides such as PA6 are engineering thermoplastics with high heat and solvent resistance properties and hence make ideal thermoplastic matrix candidates of choice to make high-performance TPVs with dynamically vulcanized mbber blends. Although nylon blends with low rubber content have been known for a long time as impact-modified nylons, as discussed under Sect. 19.7.1, elastomeric TPV blends of polyamide with high rubber content (>60 %) have not been commercially available until recently. Because of their higher thermal and chemical resistance performance, the polyamide-based TPVs have often been called super-TPVs (Leaversuch 2004). 

The thermoplastics which have been reported as efficient modifiers for epoxy resin can be classified as a) engineering thermoplastics b) amorphous thermoplastics and c) crystalline thermoplastics. 

The most popular applications to make use of slip agents are polyvinyl chloride (PVC) and polyolefin film and sheet. The agents are usually modified fatty acid esters and are effective in concentrations of 1 - 3 phr. Fatty amides, which have FDA acceptance for a wide variety of applications, are also finding use as slip agents in engineering thermoplastics as well as PVC and polyolefins. The most frequently used amides are erucamide and oleamide. 

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