NATPET – is the producer of high quality polypropylene grades, its products reached more than 60 countries on the globe and are well appreciated by its customers due to the differentiated quality of the products. This achievement was possible by virtue of the regulatory compliance document that made it possible in satisfying the converters to cope with local regulation and customer satisfaction.
What is regulatory compliance? What is the need for such compliance for our products? Since there are many regions and countries and each of them has their own laws and regulations, why and how we have to comply with all those regulations? What is the regulatory compliance document of a product and how does it benefits? These are some of the questions that comes in the minds of all those people who are either producers and manufacturers of any product or people involved in product stewardship. In this article we had tried to address such questions mainly focusing the producers of plastic resins like polypropylene.
Regulatory compliance simply means conforming to regulation which may be local, national or international regulation, also called as standards. From product point of view these standards include lists of substances that are either authorized, restricted or banned in the manufacturing of that product or during value addition at any later stage. Take for example polypropylene, it is first produced in the form of pellets of 2-3 mm diameter and then converter which is responsible for producing the finished product like plastic articles add value to it by adding some additives to improve its physical, chemical and/or optical characteristics. There are various organizations for setting up the standards. Internationally we have mainly International Organization for Standardization (ISO). Regional organizations include European Union (EU), Gulf Petrochemical and Chemical Association (GPCA) etc. Organizations like US Food and Drug Administration (FDA), China Food Contact regulations, Saudi Food and Drug Administration (SFDA), Coalition of Northeastern Governors (CONEG) provide national standards. These organizations not only develop an extensive list of substances to regulate but also provide standard test methods to identify substances, some have chemical inventory and in order to comply the product must be registered in their inventory if not already present.
The world has seen massive growth in the industries and production rates. Take the example of Saudi Arabia. Comparing 1974 statistics with 2011 of the total number of industries it was found that from around two hundred in the 70’s the numbers have grown to more than five thousand with plastic and rubber industries alone increased from around a dozen to more than five hundred. The exports figure of Saudi Arabia also shows amazing behavior. From 1995 to 2011 there is increase of 15.7 % in the export values. These massive production increase and export/import of products has almost succeeded in meeting the demands of the ever growing human population but has affected the humans and environment at the same time. Plastic and plastic products are one of the major problems. Use of plastics has increased many fold. Their presence is almost inevitable. Be it shopping bags, food packaging items, bottles, stationary items, household items and automobile parts, everywhere we find applications of plastic. No doubt this has consequences on ourselves and surroundings. By nature plastics like polypropylene and polyethylene are non-hazardous but some of the substances present inside may be. These substances may be catalyst residuals or materials added at the time of production or during conversion to enhance the properties of the final product, also called as additives. Some substances present in the plastic may also be impurities and these cannot be removed but can be controlled. These hazardous substances may migrate from plastic to food and environment through food packaging material, oxidation of plastic in the presence of sunlight, prolong presence in the soil and water bodies, through invasive and non-invasive medical devices and digestion of plastic parts by animals who mistake them with food, eventually ending up in humans and animals. Since plastic is non-biodegradable it remains in the surrounding for long periods of time and hence may release hazardous substances in the soil and water bodies due to the action of heat and light and mechanical wear. To check all the above environmental and health related issues and to maintain them under control, governments and international organizations provide regulatory guidelines and limits to be followed by the producers and manufacturers of any article including plastic in order to safeguard our planet and achieve a sustainable growth. These regulatory guidelines depend on the material and their application.
Regulatory compliance or product stewardship is a vast field and many huge and multinational companies producing variety of products have established separate department to handle this sensitive issue as failure to follow the regulations will create legal problems for the company and might result in paying heavy prices. As mentioned earlier there are various international, regional and national organizations that have been established by countries and associations that setup the regulatory standards and to sell any product in a region the product must meet the standards set for that particular region. The kind of regulation depends on the material itself and on the application of the material. For example, plastics have different set of compliance than ceramics and within plastics substance like polypropylene has different set of compliance than polyvinyl chloride, PVC. On the basis of application substances to come in contact with food have all the different set of compliance than the substances to be used in medical field which are again different for the substances for normal household usage.
There are more than 200 countries in the world. In place of having separate regulatory standards and to help flourish cross border trade the neighboring countries formed economic associations and executive bodies that are set up to enforce standards and safety, or to oversee use of public goods and regulate commerce. Some of these like REACH, EU Food contact, US Food and Drug Administration, China Food Contact and many others have very extensive list of restricted and authorized chemicals and materials and hence are accepted in most of the countries of the world. It is therefore important to realize those key regulatory bodies and make our product in compliance with them. NATPET is the producer of polypropylene and as mentioned earlier its product has reached more than 60 countries around the globe, namely countries of Europe, Africa, Latin America, Middle East, China, Southeast Asia, surely this was possible not without its product regulatory compliance. Let’s have a look at some of the regulations its product comply to:
• REACH (Registration, Evaluation, Authorization and Restriction of Chemicals)
• European Union Food Contact
• FDA (Food and Drug Administration)
• China Food Contact
• CONEG (Coalition of Northeastern Governors)
• California Safe Drinking water and Toxic Enforcement Act of 1986
• Rhode Island Air Toxics
• Switzerland “VOC-LENKUNGSABGABE”
• RoHS (Restriction of Hazardous Substances in Electric and Electronic Equipment)
Apart from these there are certain chemical like BHT, Ozone depleting substances, Phthalates, Bisphenol A, Organo-tin Compounds and many others whose use is restricted or banned in the production of plastics and hence NATPET product are in compliance to many of these.
All the above regulatory compliance information, regarding each and every product of NATPET is mentioned in the document called Regulatory Compliance Product Declaration, in short RCPD. NATPET is one of the few companies in Saudi Arabia which provide its customer with this document. It is sent with every consignment along with the MSDS (Material Safety Data Sheet). To cope up with the changing laws and standards and for including new regulations RCPD is reviewed periodically and updated every year. For convenience of its customer NATPET also provide RCPD on its website.
Why the world’s renowned companies like LyondellBasell, ExxonMobil, SABIC, Total, Borealis, Sinopec maintain this regulatory document for their product? It must have helped them. NATPET in their very initial stage realized the importance of such document and developed it, and hence now reaping its fruit. RCPD is the most complete regulatory document of a product. Conventionally, the producer issued certificate for each compliance required by customer separately. This had various drawbacks. Firstly, from the producer point of view, a lot of documentation was required, tracking was not easy in case of any amendment in the existing compliance. The certificate were issued only on the demand of customer hence there were delays in providing the document to the customer as these required the producer to do tests inside its facility or through some external laboratory and then come up with the required document. Sometimes this resulted in heavy fines from the sea port because of delay in custom clearance. From buyer point of view, the main problem was of reselling the product to other trader or converter in another country or region as this would mean new regulations. The buyer will again approach to the producer for additional certificate this would mean another delay. Thus it restricted the flexibility in cross border trade. Now with RCPD going with every consignment the whole import/export process has become smooth. Companies are finding it easy to keep record of their products regulation and are able to know in what areas they need to improve. Meanwhile buyers, traders, and converters need not to approach the producer for certificate unless which is not mentioned in the RCPD. This has really improved the international trade. No wonder all the multinationals are following this strategy.
Plastics Thermoforming Technology and Polypropylene
Thermoforming is the process of heating plastic sheet to a pliable state and forming it into shape. It offers processing advantages over injection molding and blow molding, it needs lower pressure, lower mold cost, and ease of fabrication of large parts. By using a multi cavity tool, smaller, thin wall parts, such as those used for food packaging, can be formed in large volume with relatively short cycle time. The critical issues addressed in the development commercial polypropylene grades include sheet quality, wall thickness and dimensional stability.
History of Thermoforming
Keratin as a component in tortoise shell, was probably the first material to be thermoformed. Keratin is found in animal horn and hoof. Also, others experimented with natural and extracted cellulosic in the 1800s. Modern thermoforming began about 60 years ago, shortly before, during, and shortly after the Second World War, with major developments in two important areas. Researches in thermoplastic resin chemistry led to commercializing of extrusion grade flexible PVC, PS, PP and PE. And continuous forming was achieved with the invention of the screw extruder and the roll-fed thermoformer. These breakthrough allowed a wide variety of prewar domestic products, particularly thin-gage packages, to be developed. The packaging industry adopted thermoforming as a basic process late 1970s to such an extent that the thermoformed package was considered the most significant packaging development of the 1970s decade.
Polypropylene in thermoforming
For the last 20 years, polypropylene is the raw material with the highest rate of growth because of good price-performance ratio. Nowadays polypropylene (PP) is considered a competitor to impact polystyrene PS, PVC and APET in many thin-gage thermoforming applications. It is priced competitively in $/MT with the competition, but its density (900 kg/m3) is 83% of that of PS and two-thirds of that of PVC and APET facilitate to higher number of products per kg over its competitors. PP finds unique applications where the product must sustain high temperature (100oC) and aggressive environmental conditions. The typical thermoforming sequence involves the clamping, heating, shaping, cooling and trimming of an extruded plastic sheet.
The thermoform ability of polypropylene (PP) is directly related to the quality of the extruded sheet. Sheet gauge uniformity is important to minimize part-to-part variation. Orientation is measured as a percentage of shrinkage in the machine and cross-direction of the sheet when heated to a temperature between (170 to 185°C). High levels of orientation will cause distortion of the sheet during heating and subsequent poor temperature uniformity of the sheet entering the thermoforming tool, this will result in poor thermoformed part quality. To minimize orientation, die gap to sheet thickness ratio and melt temperature should be minimized, and the recommended die gap is usually kept from 10 to 15% greater for sheet thickness.
The thermoforming process can be divided into heating, vacuum/pressure forming, cooling and trimming. The most important concerns in sheet heating are to reach the required melt phase forming temperature and to obtain uniform sheet temperature. The amount of heat energy required to reach proper sheet temperature for thermoforming varies by polymer type. Polypropylene requires more heat energy than many other plastic materials. Therefore, longer heating times are normally required to obtain optimum thermoforming conditions.
The longer heating times required for polypropylene have made sag bands, air support systems and other sheet support mechanisms popular for thermoforming. Since proper heating is critical to the quality of thermoformed parts.
Thermoforming is accomplished by vacuum, positive air pressure, plug-assisted (pressure) vacuum forming or combinations and variations of these once the sheet reaches thermoforming temperature. Plug-assisted vacuum, forming generally provides the best results for smaller, deep draw, well defined parts. Plug assists are mechanical forms used to push the molten plastic uniformly into deep draw mold cavities. Plug material of construction, design and timing can be critical to optimization of the thermoforming process.
Methods of Thermoforming
There are several methods of thermoforming to accomplish to the final shape which is depends upon the part design and shape, where the most common methods are:
o Drape Thermoforming
Drape Thermoforming, in which the plastic sheet is stretched over a positive mold. Once the plastic seals against the mold edges, a vacuum is introduced pulling the material tightly against the mold contour.
o Vacuum Thermoforming
Vacuum Thermoforming, in which a heated sheet of plastic is laid over a negative or concave mold. Once the materials seals at the mold edges, it is subjected to a vacuum pulling the material tightly into the mold.
o Plug Assisted Vacuum Thermoforming
Plug Assist Thermoforming in which is similar to cavity forming but with a male plug forcing the material partially into the mold cavity. A vacuuming completes the thermoforming and is sometimes aided by positive air pressure. This thermoforming method is particularly fast and helps maintain consistent wall thicknesses.
It is helpful to construct the plug from materials that are easily machined to control part thickness uniformity. Hard wood and synthetic foam are popular plug materials for prototype and production molds respectively. Foam plugs can be machined and have isolated properties to prevent overheating of the plug or quenching of the thermoformed plastic. The plug shape, although similar to the shape of the mold cavity, should be smaller in size and without part detail. The plug shape influences the distribution of the polymer. E.g., a flat plug face will form a part with a heavy bottom, whereas a spherical face plug will provide distribution and a sidewall thickness for deep draw.
The plug speed (timing) is typically set in accordance with the rate of vacuum bleed (vacuum between sheet and mold). For a semi speeds generally provide the best material distribution in the part. After the plug is extended, the vacuum forces the molten sheet into the mold for part definition and cooling.
In melt phase thermoforming, the mold Therefore, the mold temperature plays an important part in thermoforming. Mold temperatures affect the appearance of the part, the length of the forming cycle and the dimensional stability of the part. Polypropylene mold temperatures are typically (30 to 65°C). Cycle time is generally controlled by cooling limitations, as the part should be cooled to below its distortion temperature before removal from the mold.
Trimming the part successfully from the plastic web depends upon the temperature of the sheet and the type of trimming equipment, Thinner sheet (less than 0.04 in. or 1 mm) is easily trimmed with proper cooling time (1-2 minutes). Thicker sheet is cooled using surface cooling such as air or water spray for post-trimming on a continuous basis. Thick sheet (greater than 0.125 in. or 3 mm) and large parts are often trimmed after cooling for several minutes in ambient condition or on a sizing tool. The trimming tool is also important to obtain good finished parts. Thin parts (less than 0.03 in. or 0.75 mm) is trimmed using sheet rule dies; thicker parts generally require shearing dies. Tool and die clearances should be minimized; less than 0.0005 in. (0.0125 mm) is recommended. Due to the shrinkage of polypropylene (approximately 0.01 in/in.), webs greater than 30 in. should be slit before trimming. This allows greater trim precision and easier guidance through a continuous trim press. Plastic trim should be minimized by part and mold design, because the economics of the thermoforming process depend upon use of regrind.
Plastics thermoforming process is widely used nowadays, because of the high demanding on the packaging articles especially for food packaging. However, thermoformed products (whether Vacuum Forming, Pressure Forming or plug assisted) can be virtually indistinguishable from injection molded products. Most importantly, thermoforming has less set up and lead time, so it is extremely ideal for project designs and market concepts that require the manufacturing process to be quick. Eventually, the cost advantage of a thermoformed part or design compared with injection depends on the quantity parameter besides the required time of production. In heavy gauge thermoforming there is a broad range of laminates available or pre-forming decoration that eliminates the requirement for secondary processes. Twin Sheet Thermoforming has the advantage of two-color product option with better esthetic choice. It is accomplished by heating two extruded plastic sheets simultaneously and then forming and sealing or fusing these two sheets together during the thermoforming process. In many cases, the twin-sheeting process produces parts that can resemble a blow-molded or rotational molded product, but with several advantages.