Thermoforming | 6 MINUTE READ

Conference Uncovers Innovations Across a Range of Processes, Markets

New materials and additives for injection and blow molding, extrusion, compounding, and thermoforming highlighted the SPE Polyolefins Conference.


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Several promising material and process developments were presented at SPE’s International Polyolefins 2017 conference, held in Houston this past March. Among the highlights were new materials and additives for applications ranging from food and non-food flexible and rigid packaging, to pipe, consumer goods, and automotive.

Houston-based LyondellBasell Industries (LBI) touted its Spherizone process—a two-in-one circulating reactor that can produce novel PP grades said to be suited for inter-material applications. Included are PP pipe grades that offer up to 30% weight reduction, homopolymer grades with improved processing, transparent random copolymers, and random/impact copolymer combinations with good transparency. 

Among the latest additions is Purell RP320M, a PP random copolymer that can be used in caps and closures, labware, and flexible and rigid packaging of medical devices and pharmaceuticals. RP320M reportedly offers good clarity and excellent homogeneity to meet high quality requirements in cast film and injection Among the latest additions is Purell RP320M, a PP random copolymer that can be used in caps and closures, labware, and flexible and rigid packaging of medical devices and pharmaceuticals. RP320M reportedly offers good clarity and excellent homogeneity to meet high quality requirements in cast film and injection molding. The material exhibits low gel content, which contributes to end-use applications that require superior gloss, transparency, surface smoothness, and planarity, as well as good tear resistance. Also claimed are excellent sealing properties in cast film and good processability for injection molding. SABIC SK Nexlene Company (U.S. office in Houston), the new 50/50 joint venture between SABIC and South Korea’s SK Global, is moving ahead with development of high-performance PE products made with “post-metallocene” single-site catalysts and octene-1 comonomer in the Nexlene bimodal solution process. Included are mLLDPE and mMDPE grades with 0.5-3.0 MI and densities of 0.857-0.945 g/cc for applications ranging from food and non-food film packaging to pipe, rotomolding of chemical tanks, and heavy-duty film.

New Nexlene film grades reportedly deliver enhanced toughness, low heat-seal temperature, downgauging potential, low extractables, and excellent bubble stability. Meanwhile, Nexlene MDPE grades boast a good impact/stiffness balance, as well as excellent ESCR and processability.

Also newly emerging are advanced specialty polyolefins—both polyolefin elastomers (POEs) with bimodality that offers better impact, and polyolefin plastomers (POPs) with molecular design that renders it more elastic. There’s also a new bimodal POE with improved heat resistance that is reportedly based on a “new olefin beyond octene in performance”... and also costs less.

Characteristics of Nexlene POEs reportedly include excellent impact strength, flexural modulus, and low-temperature ductility, and better physical properties than butene-based POEs. Applications include blending at 10-25% levels with mineral-filled 

PP in automotive bumper/grilles, side-sill panels, instrument panels, and door trim. Other target applications include wire & cable, due to easy processing, high electrical resistivity and heat resistance; and encapsulants for solar cells due to moisture and weather resistance and no lamination defects.

Nexlene POPs, meanwhile, are characterized by enhanced toughness, excellent hot-tack and seal-initiation temperature, and superior transparency. Target applications included packaging film (stretch hood, shrink, and silage); specialty film (thermal laminates and foam); industrial film (waterproof sheet, protective film); and specialty food-packaging films (barrier film, stand-up pouches, snacks, and processed-meat packaging).

Dow Chemical Company, Midland, Mich., discussed the latest on its Innate precision packaging resins launched in 2015. Made with a novel post-metallocene catalyst and a new process, these resins can incorporate various copolymers, according to Christina Serrat, application technology leader for packaging and specialty plastics. She said 1-mil film of Innate ST60 (0.85 MI, 0.918 density) exhibits significantly higher dart impact at similar modulus and better optics than a competitive mLLDPE.

In heavy-duty sacks, Innate shows outstanding toughness. In bag-in-box liquid packaging, Innate resins boast excellent stiffness/ toughness balance compared with mLLDPE. Moreover, Dow reports that downgauging with Innate shows a significant reduction in flex cracking. Overall, these resins are said to deliver film toughness without compromising stiffness or other properties.

Houston-based Kraton Corporation unveiled a developmental class of styrenic block copolymers. This new semi-crystalline block copolymer (SCBC) offers PE-like crystallinity but is also said to be elastic, stiff, and strong. It is compatible with PE and can be used in conjunction with PE and oil to make elastic and soft compounds. Moreover, unlike conventional SBCs, the new polymers are resistant to oil and organic solvents. Other potential applications are elastic film for packaging, automotive soft-touch skins, and non-woven fabrics.

Dow also discussed on-line compounding of TPO blends for large-part thermoforming and development in recent years of high-melt-strength (HMS) TPO for this purpose. Senior research scientist Kurt Koppi noted that TPOs have had limited acceptance in thermoforming primarily due to processing issues: excessive sag, webbing, and inconsistent forming from lot-to-lot or within a lot.

Key thermoformability findings, according to the Dow researchers, included the following:

• For large-part thermoforming, slow sheet sag rate is desirable.
• While with pre-compounded TPO, sag rate increases with sheet extrusion rate; the opposite occurs with on-line compounded TPO.
• TPO made with POE/talc concentrate sags faster, while TPO made with PP/talc concentrate sags slower.
• TPO sheet prepared via on-line compounding with a PP/talc concentrate exhibits a sag rate very similar to that of pre-compounded TPO when sheet was extruded at a fast rate.
• Such on-line compounded TPO sheets exhibit less thinning in the corners than those made of POE/talc concentrate.

Dow says on-line compounded TPO sheet matches the performance of pre-compounded TPO sheet when a talc concentrate is used in the formulation vs. a POE. A simple single-flighted screw works as well as a high-performance screw for on-line compounding. And on-line compounding of TPO sheet offers the potential to reduce manufacturing cost by eliminating a separate compounding step.

Solvay (through its Cytec acquisition—now Cyasorb Cynergy Solutions) unveiled two new proprietary stabilizers at the conference. Cyasorb Cynergy M535 UV stabilizer is designed for general PE injection molding applications, where it offers twice the performance of existing stabilizers at reduced concentrations. 

Cyasorb Cynergy B878T is a combination UV/heat stabilizer for PP/TPO building and construction applications such as roofing and solar shingles.

Total Cray Valley (TCV, U.S. office in Exton, Pa.) discussed its new technology for improving PP melt strength. According to TCV’s global business-development manager Anthony Marozsan, new Dymalink 9200 zinc diacrylate salt coagents (also available as 9201 masterbatch) are comprised primarily of ionomeric zinc salts, which reportedly represent a new class of polyolefin additives with a novel set of performance attributes. They are now globally available. 

Addition of these zinc salts to conventional PP at low loadings (1%) has been shown to result in improved tensile strength, HDT, and flexural modulus. Melt strength of PP is said to be enhanced with very few observed drawbacks. This is said to allow greater flexibility to tailor compounds to specific end-use requirements as compared with conventional HMS-PP.

Taiwan’s Chitec Technology (U.S. office in Houston) launched a novel plant-based dialkyl hydroxylamine antioxidant (DAHA). While DAHA antioxidants have shown a negative impact on long-term stabilization, this palm-based DAHA antioxidant combined with a HALS stabilizer has been shown to outperform a traditional phenolic antioxidant. 

Baerlocher (U.S. office in Cincinnati) discussed its new Baeropol RST stabilizer for use with recycled materials (also reported in our February K 2016 review of materials and additives). Its claim to fame is that it can reduce the use of phosphite antioxidants in polyolefins and assist in switching away from TNPP.

The BASF Corporation - Plastic Additives, Florham Park, N.J., presented its latest work aimed at optimizing stabilization systems for improved discoloration resistance while reducing costs in critical applications like cast and blown PE films and injection molded PP.