Blowing, grading

In 2009, a facility capable of manufacturing 10,000 tonnes/year of PBS and its copolymers was constructed by Hexing Chemical (tradename Hexing PBS). The facility can manufacture resins for extrusion, injection, moulding, thermoforming and blowing grade [41]. 

The HDPE Tipelin and mLLDPE Exact 0201 (film blowing grades) have been chosen as the tested material. Linear viscoelastic properties (storage G and loss G" moduli), transient shear viscosity and transient first... 

Cjcolac Brand ABS—General Purpose Blow Molding Grades, Technical PubHcation SR-616, GE Plastics, Pittsfield, Mass., 1989. 

Pellets for injection-molding, extmsion, and blow-molding appHcations include mineral-filled, glass-filled, pigmented, and flame-retarded grades. 

One unfortunate characteristic property of polypropylene is the dominating transition point which occurs at about 0°C with the result that the polymer becomes brittle as this temperature is approached. Even at room temperature the impact strength of some grades leaves something to be desired. Products of improved strength and lower brittle points may be obtained by block copolymerisation of propylene with small amounts (4-15%) of ethylene. Such materials are widely used (known variously as polyallomers or just as propylene copolymers) and are often preferred to the homopolymer in injection moulding and bottle blowing applications. 

With the advent of improved clarity grades in the 1990s there has been interest in replacing PVC for blow moulded containers for bottled water. 

Structurally viscous grades are based on branched polymers (branching being effected by the use of tri- or higher functional phenols). These polymers exhibit a sharp decrease in viscosity with increasing shear rate which makes them particularly suitable for extrusion and blow moulding and also, it is claimed, in reducing drip in case of fire. 

Comparatively little information is available concerning the use of additives in commercial grades of polycarbonate. Pigments, heat and ultraviolet stabilisers, blowing agents and fire retardants are used but the range of materials available... 

Amongst the special grades that should be mentioned are those containing blowing agents for use in the manufacture of structural foams (see Chapter 16). 

In the late 1970s several developments occurred causing renewed interest in poly(ethylene terephthalate) as a plastics material. These included the development of a new mouldable grade by ICI (Melinar) and the development of a blow moulding technique to produce biaxially oriented PET bottles. In addition there appeared a glass-fibre filled, ionomer nucleated, dibenzoate plasticised material by Du Pont (Rynite) (see Chapter 26). 

Thin wall plastics are used to hot fill (injection and blow molded bottles, thermoformed containers, etc.) without sagging during filling and maintaining mechanical properties such as impact strength and stiffness in temperatures from at least —40°F to 250°F (—40°C to 120°C). Plastic used includes special grades of PEN, PET, PP, PS, and PVC. 

The large volumes of PET produced for fibers, films, blow-molding and injectionmolding grades have led to large-scale, low-cost processes for making terephthalic acid, and to a lesser degree, dimethyl terephthalate (DMT) (2). 

PBT-PC blends show increased melt strength allowing them to be easily processed by blow molding and profile extrusion. The PBT-PC blends have been extruded into sheet and thermoformed into parts. Enhanced melt strength allows PBT-PC blends to be foamed. Structural foam grades for injection molding (10-30% density reduction) are commercially available. 

---