HDPE for

Plastic materials represent less than 10% by weight of all packagiag materials. They have a value of over 7 biUion including composite flexible packagiag about half is for film and half for botties, jars, cups, tubs, and trays. The principal materials used are high density polyethylene (HDPE) for botties, low density polyethylene for film, polypropylene (PP) for film, and polyester for both botties and films. Plastic resias are manufactured by petrochemical companies, eg. Union Carbide and Mobil Chemical for low density polyethylene (LDPE), Solvay for high density polyethylene, Himont for polypropylene, and Shell and Eastman for polyester. 

By the mid-1990s capacity for polyethylene production was about 50 000 000 t.p.a, much greater than for any other type of plastics material. Of this capacity about 40% was for HDPE, 36% for LDPE and about 24% for LLDPE. Since then considerable extra capacity has been or is in the course of being built but at the time of writing financial and economic problems around the world make an accurate assessment of effective capacity both difficult and academic. It is, however, appeirent that the capacity data above is not reflected in consumption of the three main types of material where usage of LLDPE is now of the same order as the other two materials. Some 75% of the HDPE and LLDPE produced is used for film applications and about 60% of HDPE for injection and blow moulding. 

Some branching could be incorporated in the backbone of the polymer by adding variable amounts of comonomers such as hexene. These comonomers modify the properties of HDPE for specific applications. 

The product yield of LDPE and HDPE for the same degradation time is in the order of ZSM-5 catalyst > RFCC catalyst > thermal, and the cumulative yield of liquid product from LDPE was greater than that from HDPE. 

Many analytical techniques are in use for the qualitative and quantitative evaluation of monomers and oligomers extracted from PA6 (GC, differential refrac-tometry, IR, PC, SEC, HPLC, RPLC, etc.). FTIR has been used for quantitative analysis of caprolactam oligomer content (extract %) in polyamide-6 [113], The method, which involves a 3h extraction in boiling methanol, is suitable for process control and plant environment. Kolnaar [114] has used FTIR characterisation of fractional extracts with pentane, hexane, and heptane of HDPE for blow moulding applications. Vinyl acetate in packaging film has similarly been determined by quantitative FUR. 

A major characteristic of the Phillips process chain polymerisation of ethylene is that it leads to very limited branching. The resulting polymer is thus highly linear and can reach high levels of crystallinity, hence high densities approaching 0.96-0.97. Such a polyethylene is known as HDPE for "High-density polyethylene". 

In South Africa, owing to the diversity and small production volume of specific motor car models, it is not economically feasible to blow-mold HDPE fuel tanks. The only cost-effective plastic tank manufacturing process used in South Africa is rotational molding, using LLDPE with a density of 0.939 g/cm3. Some selected properties of LLDPE before and after petrol exposure are compared to HDPE in Table 16.2. It is clear that owing to weaker mechanical properties, LLDPE is far less suitable than HDPE for petrol containment, mainly because of its lower crystallinity. 

The plastics industry uses P.R.222 primarily in polyurethane. The pigment exhibits average tinctorial strength. 1/3 SD colorations in HDPE, for instance (1% TiOz), are formulated at 0.23% pigment concentration. 

Figure 10.2. Absorption kinetics of ethylbenzene into HDPE for specimens soaked in a 36 wt % ethylbenzene/C02 solution at 80 °C and 243 bar.

The most important application area of HDPE is the production of containers and injection molded articles. Bottles for detergents, gasoline cans and heating oil tanks are some examples. The most common use of HDPE for injection molded articles is for the production of storage and distribution containers, like buckets and bottle cases. However, processing into films and pipes has become increasingly more common. Films made out of HDPE possess high fat resistance (as wrappers for meat) and have better aroma barrier properties compared to lower density PE materials. 

Blow molding uses compressed air to blow and expand a hot plastic tube ( rubbery melt ) in a female mold cavity, until the plastic conforms to the walls of the mold. This has developed into a major way to produce plastic bottles, and also more specialized hollow shapes such as fuel tanks, seat backs, tricycles, surfboards, and so on. The leading material is HDPE for milk, water, and household chemicals. Second largest is PET for carbonated beverages. A number of other thermoplastics are blow molded in smaller amounts for more specialized uses. 

HDPE for Pipe Gets Top Performance Ratings 100 yr Pressure Rating, PT, July 2003. 

Alpha Packaging manufactures botdes and jars made from polyethylene terephthalate (PET) and high-density polyethylene (HDPE) for the pharmaceutical, nutritional and personal care markets. Technologies used include injection blow moulding, injection stretch blow moulding, and extrusion blow moulding. Alpha manufactures stock and custom containers in a variety of styles and colours. 

When plastics are recycled, the various types must be separated from one another. To aid in the separation, many states require manufacturers to include a recycling symbol on their products to indicate the type of plastic. You are probably familiar with these symbols, which are found on the bottom of plastic containers. The symbols consist of three arrows around one of seven numbers an abbreviation below the symbol indicates the type of polymer from which the container is made. The lower the number in the middle of the symbol, the greater is the ease with which the material can be recycled 1 (PET) stands for poly(ethylene terephthalate), 2 (HDPE) for high-density polyethylene, 3 (V) for poly(vinyl chloride), 4 (LDPE) for low-density polyethylene, 5 (PP) for polypropylene, 6 (PS) for polystyrene, and 7 for all other plastics. 

Selar PT amorphous poly(ethylene terephthalate) (PET) blends combined the inherent barrier properties of PET with the ability to be processed on conventional equipment without orientation or crystallization steps. Besides food packaging grades, other industrial grades of Selar PT are available that rival PP or HDPE for paint pails and other containers that require a hydrocarbon or solvent barrier. 

Discuss why it is acceptable to use HDPE for fluid containers when HDPE has a finite permeability, i.e. for petrol through the wall of a petrol tank, or water vapour through the wall of a brake fluid container. 

Table 29-03. Physical Properties of Equistar Chemicais Alathon HMW-HDPE for Film...

Problem Long-term heat stabilization of HDPE for wire and cable applications requires high levels oi AOs, but these can interiere with intended cross-linking mechanisms and cause migratiorr/extraction problems. 

Polyolefins are used in automotive industry due to their low cost, good weather resistance, and excellent properties. They can be used in many parts to reduce the vehicle weight, save fuel, increase comfort, and reduce CO2 emission. Polyethylene (UHMWPE or HDPE), for example, is used to absorb vibration and noise and for impact protection. Polypropylene is one of the lightest polyolefins, and with a proper design, an improvement in the passenger safety can be achieved. Polypropylene can also be used in bumper systems to absorb the kinetic energy. 

Yamauchi et al. investigated the structures of NR/high density polyethylene (HDPE) thermoplastic elastomers (TPEs) and their composites with carbon black using SANS. The extremely low contrast between crystalline and amorphous HDPE for SANS enabled us to measure the interface thickness between NR and HDPE in the TPE (5 mn) as well as that between NR and carbon black in the composite (2.4 mn). The interface thickness and fractal dimension of the blends and composites were earefully analysed using SANS even though both polymers were not deuterated. It was revealed that NR and HDPE are immiscible blends. 

Unpigmented HDPE milk and water bottles are the most valuable type of HDPE for recycling. They are made from a high-quality fractional melt index homopolymer HDPE, usu-... 

An example of this can be seen from the recycling experience of Fitchburg, WI. In early 1990, the town received a grant to evaluate homeowner participation regarding each recyclable over an 8 week period, from Match 1 to April 26,1990. The town s weekly curbside recycling program served 2,823 households and collected 11,360 pounds of HDPE for an average of 1,420 lbs./week. The participation assessment study area included 1,185 households and therefore an estimated 596 Ibs.of HDPE/week [(1,185 / 2,823) 1,420] were collected from it. Data recorded are as follows ... 

HDPE all types 9.0 Ib/cap-yr projected - - - Eyring. 1990 Easily separable HDPE for residentid CSPU in Chicago area... 

Plastics have thermal conductivity much lower than metals and therefore are poorer heat conductors. Thermal conductivity for plastics ranges from 3 X lO cal/-(cm s °C) for polypropylene to 12 X lO cal/(cm s °C) for HDPE. For aluminum the thermal conductivity is 0.3 cal/(cm s °C), and for steel it is 0.08 cal/(cm s °C). For closed-cell plastic foams, values of thermal conductivity are much lower than those of the unfoamed plastic because gases, and air in particular, have a lower thermal conductivity than polymers. Plastic fillers may increase the thermal conductivity of plastics. Semicrystalline plastics generally have a higher thermal conductivity than do amorphous plastics. 

We discuss briefly the results of some investigations on HDPE. For a detailed discussion see [29]. 

This pol5mieric material exhibits many advantageous features similar to those of HDPE (for example resistance to chemicals), it does not, however, show the disadvantages of HDPE, which is initially a tendency towards stress crack formation. As the density of this material is relatively low, it is difficult to put it into any of the above categories and it has been therefore termed Linear Low Density Polyethylene (LLDPE) (Bork 1984). It should also be noted that the terms MDPE and LMDPE are hardly used any... 

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