Biopla products factory

Plastics: Health, Safety and Environmental Impact
Authored by biopla Products factory
September 2008

Plastics Overview
Plastics are man-made polymers. A polymer is a large molecule that is made from the repetition of a single base unit. Polymers come in many different shapes with many different properties. (Though it is not, you might consider a brick wall to be a polymer made from bricks. Not all polymers are plastics; for example, protein and DNA are both polymers.) Most plastics are derived from oil, coal, natural gas and, more rarely, cellulose

In the past 15 years, commercial technology has emerged to make plastics from sugars or starches. Table 1 summarizes the raw material sources for plastics.Table I Sources of Common Plastics Raw Mate rials Examples of Types of Plastic Oil, Coal & Natural Gas most plastics (like PP, PET, HDPE, PVC, PC, etc)
Cellulose from plants cellulose acetates Sugars, starches PLA ; PHA Plastic production generally uses oil & natural gas that have been refined (in a process called cracking) and processed into chemicals (hydrocarbons) that are ready for the chemical process of polymerization.

In the USA about 4% of oil and natural gas consumption is for the production of plastics. For years, some plastics have been made from the renewable resource cellulose, which comes from plants. Recently a few biodegradable plastics have entered the marketplace. These are typically produced by using bacteria to prepare sugars for polymerization. With current commercial technology most biodegradable plastics are made from sugar or starches. However, there are
commercial technologies that use carbon dioxide and catalysts to produce biodegradable
plastics.1 Scientists are also working to develop plastics from algae or from processes that rely on nanotechnology. 2 It is likely that the next 100 years of plastics will show even greater innovation than the first 100 years.
Though plastics were known by scientists during the mid 1800s, the discovery of synthetic plastics really started during the 1920s with a plastic called Bakelite. During the 1930s,

the now common plastics polystyrene (PS), polyvinyl chloride (PVC), and nylon entered widespread production. In the early 1940s, polyethylene terephthalate (PET) was discovered and ten years later, polypropylene (PP) was discovered. Polycarbonate (PC) was introduced to the market in the 1970s. The usefulness of plastics and ease of synthesis from natural gas and oil have made them ubiquitous in the developed world.

With the increase in types of plastics and their widespread use, in 1988 the Society of the
Plastics Industry (SPI) introduced a voluntary resin identification coding system to help with
identification of plastics in products. Table 2 summarizes this system.

Identification Codes for Plastics
SPI Code Fami ly of Plastic Typical Use
#1 polyethylene terephthalate (PET, PETE) Soft drink and single-use water bottles
#2 high density polyethylene (HDPE) Milk bottles
#3 polyvinyl chloride (V, PVC) Pipes
#4 Low density polyethylene (LDPE) Wrapping films, grocery bags
#5 Polypropylene (PP) Yogurt cups, ketchup bottles
#6 polystyrene (PS) Single-use coffee cups
#7 Other e.g., polycarbonate (PC) Various
In 1995 many states started requiring these codes on certain products (like bottles and containers over a certain size). These codes attempt to identify the family of plastic to which the product belongs. Please note that #7 is regarded as a “catch-all” category –any plastic not fitting into the 1-6 families can be labeled as #7. PLA, polycarbonate,

The recycling codes are not an attempt to categorize which plastics are more or less benign or recyclable. For more information on the SPI codes,
see http://www.plasticsindustry.org/outreach/recycling/2124.htm.
It is important to note that the common names of plastics denote a family of plastics. For example, polypropylene (PP) refers to a family of plastics that all have the same single base unit. In the PP family there are several different types of PP depending on the arrangement of the base unit in the polymer. Further complicating matters, some plastics can be combined with other plastics and/or additives to produce different plastics, yet the resulting plastic may still be referred to by its common name.

Summary For the health of our consumers and the environment, we aim to minimize the impact caused by our products. As scientific understanding develops, we must be on the cutting edge of understanding the affects of our products. We pledge to act only if we are reasonably convinced our actions will minimize harm to humans and the environment. Specifically,

We only use: polylactide (PLA)

Polylactic acid or polylactide (PLA) is a biodegradable, thermoplastic, aliphatic polyester derived from renewable resources, such as corn starch or sugarcanes (rest of world). Although PLA has been known for more than a century, it has only been of commercial interest in recent years, in light of its biodegradability.

Ring-opening polymerization of lactide to polylactide

Bacterial fermentation is used to produce lactic acid from corn starch or cane sugar. However, lactic acid cannot be directly polymerized to a useful product, because each polymerization reaction generates one molecule of water, the presence of which degrades the forming polymer chain to the point that only very low molecular weights are observed. Instead, lactic acid is oligomerized and then catalytically dimerized to make the cyclic lactide monomer. Although dimerization also generates water, it can be separated prior to polymerization. PLA of high molecular weight is produced from the lactide monomer by ring-opening polymerization using most commonly a stannous octoate catalyst, but for laboratory demonstrations tin(II) chloride is often employed. This mechanism does not generate additional water, and hence, a wide range of molecular weights are accessible.

Polymerization of a racemic mixture of L- and D-lactides usually leads to the synthesis of poly-DL-lactide (PDLLA) which is not crystalline but amorphous. Use of stereospecific catalysts can lead to heterotactic PLA which has been found to show crystallinity. The degree of crystallinity, and hence many important properties, is controlled by the ratio of D to L enantiomers used.

Chemical and physical properties

Due to the chiral nature of lactic acid, several distinct forms of polylactide exist: poly-L-lactide (PLLA) is the product resulting from polymerization of L,L-lactide (also known as L-lactide). PLLA has a crystallinity of around 37%, a glass transition temperature between 50-80 °C and a melting temperature between 173-178 °C.

Polylactic acid can be processed like most thermoplastics into fiber (for example using conventional melt spinning processes) and film. The melting temperature of PLLA can be increased 40-50 °C and its heat deflection temperature can be increased from approximately 60°C to up to 190 °C by physically blending the polymer with PDLA (poly-D-lactide). PDLA and PLLA form a highly regular stereocomplex with increased crystallinity. The temperature stability is maximised when a 50:50 blend is used, but even at lower concentrations of 3-10% of PDLA, there is still a substantial improvement. In the latter case, PDLA acts as a nucleating agent, thereby increasing the crystallization rate. Biodegradation of PDLA is slower than for PLA due to the higher crystallinity of PDLA. PDLA has the useful property of being optically transparent.

Authored by biopla Products factory

Chem zone huiyuan road Ningbo China P.O: 315203

T:0086-574-86503646 . 87265646

F:0086-574-87252099

mike@2wplastic.com
September 2008