Plastic drawbacks

This chapter highlighted the huge diversity of microbial PHAs, demonstrating that these versatile biopolyesters possess the potential to replace various contemporary fossil-based plastics. Drawbacks in the large-scale production of PHAs were discussed, and economic feasibility was considered. 

Surfa.cta.nt-TypeAntista.ts, Inherently conductive antistats have the advantage of not being dependent on atmospheric moisture to function. Thek drawbacks include expense, coloration of the plastic, and alteration of the mechanical properties of the plastic. The added stiffness caused by conductive fillers may not be a problem with a rigid container, but it can be a problem for a flexible bag. 

Uses. Dicyandiamide is used as a raw material for the manufacture of several chemicals, such as guanamines, biguanide and guanidine salts, and various resias. Siace 1975, it has also been used ia the manufacture of potassium or sodium dicyanamide which are used as iasecticides and ia chemotherapy. Melamine has extensive appHcations ia the resia and plastic iadustry guanamines are used as copolymers (qv) ia many resia compositions. Guanidine phosphate [1763-07-1] is employed as a fire retardant ia appHcations where water solubiHty is not a drawback. 

These methods are the simplest, cheapest, and practically most accessible for airflow visualization. They are sold in the form of small glass tubes or plastic bottles through which air is pumped manually. Time for use of one unit is typically one hour or up to one day. One drawback of these two principles is the fact that the emitted smoke is strongly irritating if inhaled and also corrosive. Therefore, they must be used with some care, but this will normally not lead to any major re strictions. Another limitation is the low amount of smoke that is emitted. 

OFETs constructed on a silicon wafer do not lake advantage of one of the main interest of organic materials, namely the possibility of building electronic devices on plastic substrates. A second important drawback of the silicon-based structure is the difficulty to individually address the gale of transistors built on the same wafer, which would prevent the achievement of integrated circuits. 

In particular, it should be noted that the past traditional equations that have been developed for other materials, principally steel, use the relationship that stress equals the modulus times strain, where the modulus is constant. Except for thermoset-reinforced plastics and certain engineering plastics, most plastics do not generally have a constant modulus of elasticity. Different approaches have been used for this non-constant situation, some are quiet accurate. The drawback is that most of these methods are quite complex, involving numerical techniques that are not attractive to the average designers. 

The practice of molding inserts in place is usually employed to provide good holding power for plastic products, but there are drawbacks to this method. It normally takes a pin to support the insert, and since this pin is small in relation to the cored hole for the insert, it is easily bent or sheared under the influence of injection pressure. Should the insert fall out of position, there is danger of mold damage. Also, the hand placement of inserts contributes to cycle variation and with it potentially product quality degradation. Some of these problems can be overcome by higher mold expenditures,... 

The efficacy of ethylene oxide treatment depends upon achieving a suitable concentrahon in each article and this is assisted greatly by the good penetrating powers of the gas, which diffuses readily into many packaging materials ineluding mbber, plastics, fabric and paper. This is not without its drawbacks, however, since the level of... 

However, there seems to be some drawback in the solubility or dispersibility of ion-sensing material in silicone rubber. This is mainly because silicone rubber does not contain a large quantity of plasticizer as the membrane solvent, in which neutral carriers can be dissolved easily, unlike in plasticized-PVC ion-sensing membranes. This issue is serious, especially with silicone-rubber membranes containing neutral carriers that show high crystallinity. Valinomycin, a typical ionophore, seems applicable to silicone-rubber-based K" -selec-tive electrodes [7,8,12-14]. Conventional crown-ether-based neutral carriers are also quite soluble in silicone rubber. 

Instead, when two solids are pressed together, due to surface irregularity, the real contact area A (see Fig. 4.2) can be much smaller (for metal a factor 10-6) than the nominal contact area A. An applied force results in a strong pressure on the contact area A, and a plastic or permanent deformation occurs. The deformation changes the area A hence the thermal conductance of the contact is proportional to the force. A drawback of the deformation of the lattice is the reduction of the bulk conductivity of the material. 

Glass jars make good containers because they are more likely to isolate soil samples from possible contamination. They can, however, break. It is important to remember that the composition of lid liners may be important in maintaining soil sample integrity. Liners can have the same drawbacks as plastic or paper containers. 

The drawback has been overcome by a technique that effects downward flow of transfer solution by capillary action under alkaline conditions, accomplishing efficient transfer of DNA to either nitrocellulose or plastic membranes in 2.5 hours (C2). 

The choice of plasticizer types and levels is a subtle compromise between the bestowed advantages and drawbacks ... 

Flexible PVC suffers from the same drawbacks as rigid PVC the more so as the amount of plasticizer increases, increasing creep, fire sensitivity (except for FR plasticizers), fume toxicity and corrosivity, and decreasing chemical resistance and thermal ageing resistance. 

Thermal insertion a heating tool heats the insert, which in turn heats the plastic part receiving the insert. The tool then presses the insert into the hole in the part. The advantages and drawbacks of this process are ... 

The combination of simple processes from plastic and metal technologies. Each material has its advantages and drawbacks. Hybrids that closely associate two or more families benefit from their best properties and mask their weaknesses. 

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