Puncture resistance

Polybutylene exhibits high tear, impact, and puncture resistance. It also has low creep, excellent chemical resistance, and abrasion resistance with coilability. 

Linear Low Density Polyethylene. Films from linear low density polyethylene (LLDPE) resias have 75% higher tensile strength, 50% higher elongation-to-break strength, and a slightly higher but broader heat-seal initiation temperature than do films from LDPE. Impact and puncture resistance are also improved over LDPE. Water-vapor and gas-permeation properties are similar to those of LDPE films. 

Even though separation may not be the primary function for which the geotextde is instaded, in almost every case the geotextde does perform as a separator. For the separation function, the physical properties of concern are primarily strength-related, including wide width, puncture resistance, and tear resistance. 

Film. By far the largest appHcation for LLDPE resins (over 60% in the United States) is film. Because LLDPE film has high tensile strength and puncture resistance, it is able to compete with HDPE film for many uses. The toughness and low temperature properties of LLDPE film also exceed those of conventional LDPE. Furthermore, because LLDPE resins exhibit relatively low strain hardening in the molten state and lower extensional viscosity, it can be produced at high rates with Httle risk of bubble breaks. 

BP. These nitrile alloy membranes are compounded from PVC, flexibilized by the addition of butadiene—acrylonitrile copolymers, PVC, and other proprietary ingredients. Typically reinforced with polyester scrim, NBP membranes are 1 mm thick and have a width of 1.5 m. They ate ptedominandy used in mechanically fastened roofing systems. NBP membranes exhibit excellent teat and puncture resistance as well as good weatherabihty, and remain flexible at low temperatures. They ate resistant to most chemicals but ate sensitive to aromatic hydrocarbons. The sheet is usually offered in light colors. The physical characteristics of NBP membranes have been described (15). 

It is generally claimed that metallocene polyethylenes (often abbreviated to m-PE) exhibit superior mechanical and optical properties as well as better organoleptic properties (resulting from the lower residue levels). As an example m-LLDPE is particularly favoured as a stretch film for wrapping because of the good prestretchability, high puncture resistance and tear strength, all of which are claimed to be better than with conventional LLDPE. 

The commercial grades available in the 1970s used either zinc or sodium as the cross-linking ion and ranged in melt flow index from 0.4 to 14. The main application of the ionomer resins has been for packaging film. The polymer is particularly useful in composite structures to provide an outer layer with good heat sealability. The puncture resistance of film based on ionomer film has the puncture resistance of a LDPE film of twice the gauge. 

General advice on the suitability and degree of resistance of glove materials are summarized in Table 13.12. In all cases, however, in addition to the necessary mechanical properties (i.e. resistance to abrasion, blade cut resistance, tear resistance and puncture resistance rated according to European Standard EN 388), consideration should be given to the resistance to the specific chemicals involved. 

To improve the end use performance and make the processability easy, control of MW and MWD as well as the use of.more than one comonomer has been reported for LLDPE [28]. Union Carbide s high MW-LLDPE with broad MWD is a 1-hexene-based resin, and its film provides superior (about 30-50% higher) tensile strength, puncture resistance, and dart impact strength than conventional 1-hexene-based resin, but with lower tear resistance in the transverse direction. The broad MWD makes the resin processability easy on the conventional extruder. 

Based on this analysis it is evident that materials which are biaxially oriented will have good puncture resistance. Highly polar polymers would be resistant to puncture failure because of their tendency to increase in strength when stretched. The addition of randomly dispersed fibrous filler will also add resistance to puncture loads. From some examples such as oriented polyethylene glycol terephthalate (Mylar), vulcanized fiber, and oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with puncture loading conditions in applications can be reinforced against this type of stress by use of a surface layer of plastic with good puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this type of application is the addition of an oriented PS layer to foam cups to improve their performance. 

Polyethylene sack or T-shirt bags are stronger than paper bags, take up 30% less storage space, provide water and puncture resistance, recyclable, etc. 

Mechanical Breakage. Mechanical breakage of packages can occur for several reasons. The materials may not have sufficient strength (heavy enough paper or film), puncture resistance may be insufficient, or one part of the structure may be too weak (or too strong) for the particular application. 

FMCs must resist penetration by construction equipment, rocks, roots, and other natural phenomena. Traffic by operational equipment can cause serious tearing. A geotextile placed on top of or beneath a membrane increases its puncture resistance by 3 or 4 times. Remember, however, that a geotextile placed beneath the FMC and the clay layer will destroy the composite action between the two. This will lead to increased infiltration through penetrations in the FMC. 

Bentonite clay expands when moist to create a waterproof barrier. Bentonite is sold in various forms, including panels and mats. Bentonite is not as resistant to chemicals as the thermoplastic membranes, nor is it puncture resistant. The major flaw of bentonite as a radon barrier, however, is that it is only tightly expanded when wet. This is acceptable for a waterproofing material, but not for a gas barrier. 

Polyethylene-coated kraft paper vapor barrier is available in 8 x 125 ft rolls. Overlaps of 6 in. are marked on the paper with a printed line. They can be sealed with polyethylene tape. This material is attractive to contractors because it is more puncture resistant than a 6-mil polyethylene construction film, but less expensive than many alternative products. 

Figure 8,10 illustrates the general configuration for testing a film s puncture resistance. We can perform this test in a number of ways. The probe may be attached to the crosshead of a universal testing machine, similar to the one illustrated in Fig. 8.3. We drive the probe down through the film at a constant speed, while recording the force. Alternatively, we can perform an impact puncture test, in a similar fashion to impact plaque testing.

Every year, Americans use over one billion sharp objects to administer healthcare in their homes. These sharp objects include lancets, needles, and syringes. If not disposed of in puncture-resistant containers, they can injure sanitation workers. Sharp objects should be disposed of in hard plastic or metal containers with secure lids. The containers should be clearly marked and be puncture resistant. 

Other relatively inexpensive personal protective items that are not absolutely essential but should be considered are protective garments and gloves. One-piece coveralls with head covers and booties made from lightweight plastic such as Tyvek are relatively inexpensive, semi-repellent, and disposable. Nitrile gloves are preferred over latex gloves because they have much greater tear and puncture resistance. 

Films and sheets with high clarity, puncture resistance, impact strength, low heat-seal temperature used for shrink-wrap, heavy-duty shipping sacks, produce bags, bag-in-box food and technical packaging films... 

Packaging films and sealants, puncture-resistant films for pouches and blister packs, glass coatings... 

Envelope material such as DuPont s Tyvek Stiffer than other polyethylene films Strong and puncture resistant... 

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